GB2468490A - Resonant power converter having variable output power or switching frequency - Google Patents

Resonant power converter having variable output power or switching frequency Download PDF

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Publication number
GB2468490A
GB2468490A GB0904033A GB0904033A GB2468490A GB 2468490 A GB2468490 A GB 2468490A GB 0904033 A GB0904033 A GB 0904033A GB 0904033 A GB0904033 A GB 0904033A GB 2468490 A GB2468490 A GB 2468490A
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Prior art keywords
resonant
converter
actively
resonant converter
output power
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GB0904033D0 (en
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Koen Geirnaert
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Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/02—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc
    • H02M5/04—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters
    • H02M5/22—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M5/275—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/297—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases without intermediate conversion into dc by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal for conversion of frequency
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
    • H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
    • H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
    • H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
    • H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/538—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a push-pull configuration
    • H02M7/53803—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a push-pull configuration with automatic control of output voltage or current
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
    • H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/288—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps without preheating electrodes, e.g. for high-intensity discharge lamps, high-pressure mercury or sodium lamps or low-pressure sodium lamps
    • H05B41/2881—Load circuits; Control thereof
    • H05B41/2882—Load circuits; Control thereof the control resulting from an action on the static converter
    • H05B41/2883—Load circuits; Control thereof the control resulting from an action on the static converter the controlled element being a DC/AC converter in the final stage, e.g. by harmonic mode starting
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/288—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps without preheating electrodes, e.g. for high-intensity discharge lamps, high-pressure mercury or sodium lamps or low-pressure sodium lamps
    • H05B41/2885—Static converters especially adapted therefor; Control thereof
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/26—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc
    • H05B41/28—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters
    • H05B41/288—Circuit arrangements in which the lamp is fed by power derived from dc by means of a converter, e.g. by high-voltage dc using static converters with semiconductor devices and specially adapted for lamps without preheating electrodes, e.g. for high-intensity discharge lamps, high-pressure mercury or sodium lamps or low-pressure sodium lamps
    • H05B41/292—Arrangements for protecting lamps or circuits against abnormal operating conditions
    • H05B41/2928—Arrangements for protecting lamps or circuits against abnormal operating conditions for protecting the lamp against abnormal operating conditions
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
    • H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
    • H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/4815—Resonant converters
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Circuit Arrangements For Discharge Lamps (AREA)

Abstract

A resonant converter for driving a device, particularly a gas discharge lamp, where the converter is adapted for actively or passively controlling at least one input parameter of a resonant circuit and/or at least one resonant component in a resonant circuit of the converter so as to vary either the output power of the device or the switching frequency, while keeping the other substantially constant, or without substantially influencing the other. The input parameter may be input current or input voltage. The resonant component may be a capacitor and/or and inductor, and the contribution of this component to the impedance of the resonant circuit may be varied. The resonant component may be a MOSFET gate drain parasitic capacitor. A feedback control loop may be provided to regulate either the output power or the switching frequency.

Description

Resonant Power Converter Systems and Methods
Technical field of the invention
The invention relates to the field of power converter systems for operating gas discharge systems on high frequencies and for which the operating frequency needs to be changed to avoid acoustic resonance in the gas discharge system.
Background of the invention
Today most of the HID lamps are controlled with magnetic ballasts operated on the mains frequency or with a low frequent switching electronic ballasts. Nevertheless operating HID lamps on high frequency could bring several advantages. It leads not only to a higher efficient, cheaper and compacter ballast, but it also increases the lifetime of the lamp.
Operating HID lamps on high frequencies has also a significant drawback. When high intensity gas discharge (HID) lamps are operated above a typical switching frequency of 400Hz they can suffer from arc instability and flickering, called acoustic resonance.
These instabilities are resulting in bad operation, disturbing side effects like flickering or damage to the lamp.
Acoustic resonance is inherent on the high intensity gas discharge lamp and is occurring in bands spread over the frequency range from 400Hz till several 100KHz and these resonance bands can shift over time. The resonance band position is typically dependent on many external conditions like distance between the electrodes, tube radius, gas pressure, gas temperature, power, gas chemical components and concentrations.
Thus it is clear that during operation and lifetime the unstable frequency points or bands can shift.
Outside these instability bands the lamp can be operated safely. Operating a HID on high frequency requires two conditions. First the instability bands needs to be detected and second the lamp needs to be operated outside these bands.
A specific detection algorithm is explained in POT W02007/128472A1 where a new, direct and cost effective way of looking to the problem is proposed. Instead of evaluating the electrical signals to detect acoustic resonance, the patent describes a method to detect and avoid acoustic resonance by analyzing the optical output signal of the lamp. The algorithm enables detection of the instability bands by evaluating the optical power spectrum variations of the lamp during a scan of the operating frequency band.
Once the instability band in the operating frequency range is known, the frequency of the control signal of the electronic ballast can be shifted outside the instability bands.
The ballast power converter in general must fulfil sudden conditions to be able to control an HID lamp. The HID lamp does not accept DC voltages or currents, so the applied power signal to the lamp must be a symmetrical AC power signal. For the lamp life time and for EMI reasons it is also preferred that the waveform has a sinusoidal shape.
And for isolation reasons it is required that the lamp is isolated from the mains via a transformer. For these reasons classic converter topologies like full bridge push pull, fly-back and forward converters are not suitable. Fly-back converters and forward converters have no symmetrical output waves since the power is controlled with a pulse width modulated signal. A Full bridge Push-pull converter is suitable to control HID lamps over a wide frequency range since the full bridge can generate a symmetrical AC signal. The drawback of this converter type is that the full bridge is hard switching resulting in high switching losses.
An alternative converter is the resonant converter. The converter consists out of one or more switching elements that convert a DC power line to an AC power signal. This signal is applied to a resonant circuit to generate a phase shift between input switching voltage and the input switching current. The switching frequency determines the impedance of the resonant circuit and controls the output power. Due to the phase shift the converter can switch when the current is zero or the voltage is zero. By this principle the switching losses are minimised.
A typical resonant converter is the series resonant converter consisting of a halve bridge or a full bridge as switching input, a capacitor and an inductance in series serving as resonant circuit and a transformer to scale the output voltage to the load. Due to the capacitor in series and the transformer the output voltage is always a symmetrical AC signal. The operational switching frequency of a resonant converter is determined by the resonance frequency of the resonant elements. In a series converter with an inductance L and a capacitor C, the resonance frequency is fres= 2ir x 1/sqrt(LxC). To enable zero voltage or zero current switching the switching frequency needs to be above the resonance frequency. The output power is regulated by changing the switching frequency of the input signal via the switching elements.
Another type of resonant converter is the resonant fly-back or forward converter where only one switching element is used and where parasitic spread inductance of the transformer combined with a parallel capacitor form the resonant circuit.
Summary of the invention
It is an object of the present invention to provide good devices, systems and methods for driving loads.
It is an advantage of embodiments according to the present invention that devices are provided allowing control of one of a switching frequency or output power while maintaining the value of the other constant. State of the art resonant converters are used to control the output power by changing the switching frequency. A particular case is when the output load is a constant load like a gas discharge system in steady state. If, in that case, the frequency is shifted to operate the lamp outside the resonance band then the output power of the lamp as a result of the frequency shift will vary. This variation needs to be avoided since constant light output is required.
It is an advantage of embodiments according to the present invention that, in order to be able to shift the operating frequency of the ballast, an adapted ballast converter topology is provided. By making the passive resonance elements active or actively controllable the resonance frequency may be varied and may be used as a second degree of freedom to control the output power. Alternatively or in addition thereto, by making the input voltage or input current of the resonant converter variable the operating frequency can be varied and the variable input parameter like input voltage or input current may be used as a second degree of freedom to control the output power. This may introduce new variables in the function P0t= F(fswitching,L,C, Vinput, linput) since L or C and/or Vnput and or Input are made variable.
It is an advantage of embodiments of the present invention that these new variables can open alternative ways to control an output load.
It is an advantage of embodiments of the present invention that it allows to vary the value of the input current or input voltage with a symmetrical 50% duty cycle signal while other converter topologies control the input current by varying the pulse width of the control signal. The above object can be obtained using devices, systems and methods as set forth below.
The invention relates to a resonant converter for driving a device, the resonant converter being adapted for varying one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other.
The resonant converter may comprise a resonant circuit and may be adapted for actively or passively controlling at least one input parameter for the resonant circuit and/or at least one resonant component in the resonant circuit of the converter so as to vary one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other.
The resonant converter may be adapted for actively or passively controlling at least one input parameter and wherein the at least one input parameter comprises an input voltage or an input current.
The resonant converter may be adapted for actively varying or actively controlling, during operation, an impedance by actively varying or controlling at least one resonating element or component in the resonant circuit so as to allow varying one of the output power of the device and the resonance frequency, while keeping the other substantially constant or without substantially influencing the other.
Embodiments also may comprise features as set forth in the attached dependent claims.
The present invention also relates to a method or algorithm for driving a device, the method or algorithm comprising varying one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other. The method or algorithm may comprise actively or passively controlling at least one input parameter of a resonant circuit and/or at least one resonant component in a resonant circuit of the converter so as to vary one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other. The method or algorithm may comprise actively or passively controlling at least one input parameter for the resonant circuit so as to vary one of the output power of the device and the switching frequency, while keeping the other substantially constant or without substantially influencing the other. The method or algorithm may comprise actively varying or actively controlling, during operation, an impedance of a resonant circuit of a resonant converter by actively varying or controlling at least one resonating element or component in the resonant circuit so as to vary one of the output power of the device and the switching frequency, while keeping the other substantially constant or without substantially influencing the other.
Embodiments also may comprise features as set forth in the attached dependent claims.
The present invention also relates to the use of a converter as described above for controlling a gas discharge system, for igniting a gas discharge system, or for dimming a gas discharge system.
In some embodiments, instead of changing the output power by changing the switching frequency the output power can now be regulated by changing the value of at least one input parameter such as input voltage or input current, or by changing at least one resonator element or component, e.g. L and/or C, and by keeping the switching frequency constant. It is an advantage of embodiments that such techniques may be used for dimming e.g. gas discharge lamps, for example in the case that a gas discharge lamp is driven at an appropriate switching frequency.
In some embodiments, the switching frequency may be varied and the output power can be kept constant by varying at least one resonator element, e.g. L and/or C and/or by varying the input voltage or input current for the converter or resonant circuit thereof, if present. The at least one resonator element, e.g. L and/or C, may be varied to change the resonance frequency of the resonating elements impedance. Alternatively or in addition thereto the at least one input variable like input voltage or input current, may be varied to change the input power of the resonant circuit. By lowering the resonance frequency, lowering the input voltage and/or lowering the input current, the output power can be decreased by a constant switching frequency. So in case the switching frequency is to be lowered, the resonance frequency, input voltage or input current may be lowered to compensate and keep the output power constant.
In some embodiments, at least one of the resonating elements and/or the input voltage and/or the input current may be actively changed and a control loop may be regulating the frequency to keep the output power constant. In case the change of frequency is used to avoid acoustic resonance in a gas discharge system this may be a possible solution. The output power of the lamp can be kept constant while at least one of the resonating elements may be changed and/or the input parameters like input voltage or input current may be changed and the control loop may change the switching frequency to keep the output power constant.
Changing the resonating elements and/or the input parameter(s) may for example be done in two ways. A continuous mode, where a value of one or more of the resonating elements and/or one or more input variables like input voltage or input current may be changed continuously during operation and where the variations of the switching frequency may be used to establish a power control loop. Another mode can be the discrete mode, where one or more values of one or several resonant elements in the resonant circuit and/or one or more input variables like input voltage or input current may be changed in steps during operation. In case of changing one or more of the resonance elements and/or one or more input variables like input voltage or input current in steps the switching frequency of the converter may be changed in a control loop to keep the output power constant. When in this mode acoustic resonance is detected the one or more resonance elements and/or one or more input variables like input voltage or input current may be changed and the control loop may react by changing the switching frequency to keep the output power constant. This can be done in a continuous and in a discontinuous mode.
An alternative may be that the frequency of the lamp control signal may be changed by changing the switching frequency of the switching elements and that the power may be kept constant by changing the value of one or more of the resonating elements and/or by changing one or more input variables like input voltage or input current. Changing the switching frequency may need to be compensated by actively changing one or more of the resonance elements and/or one or more input variables like input voltage or input current to keep the output power constant.
Control of the output power may comprise control of output voltage and/or output current.
It is an advantage of embodiments according to the present invention that, by changing the resonance frequency of a resonant circuit and/or by changing one or more input variables like input voltage or input current, the output power can be regulated without changing the frequency or on the other hand the output power can be kept constant while changing the frequency.
It is the latter algorithm that can be used to keep the output power of a gas discharge system constant while changing the switching frequency of the converter.
Brief description of the drawings
Figure 1: Series resonant converter topology.
Figure 2: Resonant fly-back or forward converter.
Figure 3: An AC frequency analysis circuit of a series resonant impedance with variation of the serial capacity. The drain-source parasitic capacitor of a MOSFET is used and the value of the parasitic capacitor is varied by applying three different negative gate-source voltages, as can be used in an embodiment of the present invention.
Figure 4: AC analysis of resonant frequency change by varying drain-source parasitic capacitor value by applying three negative gate-source voltages, as can be used in an embodiment of the present invention.
Figure 5: Resonant Fly-back converter with discrete resonant frequency control, according to an embodiment of the present invention.
Figure 6: Transient output variation by changing the resonant frequency in steps, according to an embodiment of figure 5.
Figure 7: Resonant Fly-back converter with continuous resonant frequency regulation, according to an embodiment of the present invention.
Figure 8: Simulation result of a supply circuit to supply the driver for changing continuous the resonant frequency of the resonant converter, as can be performed using embodiments of the figure7.
Figure 9: Resonant Fly-back converter with discrete resonant frequency control, according to an embodiment of the present invention.
Figure 10: Transient output variation by changing the resonant frequency in steps, according to an embodiment of figure 9.
Figure 11: Resonant converter according to an embodiment of the present invention including the optical circuit for detecting acoustic resonance and the converter power regulation loop.
Figure 12: Series resonant converter combined with a boost converter.
Figure 13: Simulation of resonant converter input voltage variation and switching frequency variation.
Figure 14: Resonant Fly-back converter with discrete input current control by switching different input currents in parallel in discrete steps.
Figure 15: Simulation result of a resonant fly-back converter with discrete input current control by switching an additional input current.
Figure 16: Resonant Fly-back converter with continuous input current variation by changing the cascode voltage of the cascoded switching device.
Figure 17: Simulation result of changing input current in continuous mode by changing the cascode voltage on the cascode of the cascoded switching device.
Figure 18: Resonant Fly-back converter with continuous input current variation by changing the cascode voltage of the input switch by a DAC and an amplifier.
Figure 19: Resonant converter according to an embodiment of the present invention including the optical circuit for detecting acoustic resonance and the converter input current control loop.
Description of illustrative embodiments
The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. The present invention relates to gas discharge systems such as for example -but not limited to -gas discharge lamps such as e.g. high intensity discharge (HID) lamps, drive electronics for such lamps, adjusting systems for such lamps and method for controlling and/or driving such lamps. In embodiments of a first aspect, the present invention relates to a control system for controlling a gas discharge system.
The first figure shows a standard half bridge serial resonant converter. The converters converts a DC input voltage to an AC output voltage over a resistive load. The converter consists of a controller that is driving the gates of the half bridge switching elements, a serial resonant circuit consisting out of a capacitor and an inductor, a transformer and a resistive load. The output of the half bridge is connected to a serial resonant circuit consisting of a capacitor and an inductance. The signal coming from the half bridge is applied to the resonant circuit and has a block wave shape. Due to the resonant circuit that acts like an LC filter, the signal applied to the resistive load has a more sinusoidal shape. The current through the load is lagging behind on the input block wave resulting in zero voltage switching. By changing the frequency of the impedance of the resonant circuit is changing and is influencing the current. So by changing the frequency the output power can be controlled. The second figure shows another implementation of a resonant converter. This resonant fly-back /forward converter has a single switching element and also converts a DC input voltage to an AC output voltage over a resistive load. The converter consists of a controller and two switches where the top switch is used as a cascode and the bottom switch as a switching device, a resonant circuit that is build up with a capacitor and the leakage inductance of the transformer, a transformer and a resistive load. By switching on, current is build up in the primary inductance of the transformer; in the leakage inductance and voltage is build up over the capacitor. When switching the switch off, the capacitor is resonating with the leakage inductance of the transformer and the voltage on the drain of the cascade switch is flying back above the DC input voltage. By this converter an AC signal is generated on the input of the transformer symmetrical around the DC input voltage. This AC signal is brought to the load (resistor) via the transformer. In this converter the switching frequency is again determined by the resonance frequency of the resonant elements. Again in this type of resonant converter the power to the output can be regulated by changing the switching frequency. By changing the frequency the impedance of the resonant circuit is changing and influencing the current through the primary of the transformer.
In a first aspect, the present invention relates to a resonant converter for driving a device whereby the resonant converter is adapted for varying one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other. The resonant converter may comprise a resonant circuit and may be adapted for actively or passively controlling at least one input parameter of the resonant circuit and/or at least one resonant component in the resonant circuit of the converter so as to vary one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other. The resonant converter is adapted for driving a device, e.g. an output load. Such an output load may be a gas discharge system. Such a gas discharge system may be a gas discharge lamp, although the invention is not limited thereto. A gas discharge lamp may e.g. be a HID lamp, although the invention is not limited thereto.
In some embodiments of the present invention, the resonant converter may be for example a half bridge serial resonant converter or resonant fly-back/forward converter, although the invention is not limited thereto. The resonant circuit may comprise at least one resonating element. The at least one resonating element may be at least one capacitor. The at least one resonating element may be at least one inductor. The at least one resonating element may be at least one capacitor and at least one inductor. The at least one resonating element may be a piezo-element. It also may be a plurality of resonating elements. The resonant converter according to some embodiments of the present invention may be adapted for actively varying or controlling, during operation, an impedance by varying at least one resonating element in the resonant circuit so as to allow varying one of the output power of the device and the resonance frequency, while keeping the other substantially constant or without substantially influencing the other. In other words, the resonant converter may be adapted for varying the output power of a device while keeping the switching frequency constant or without substantially influencing the switching frequency, while in other embodiments, or the resonant converter may be adapted for varying the switching frequency, e.g. for driving the device in stable frequency regions where the problem of instable frequencies due to acoustic resonance is not present, and for maintaining the output power value constant or without substantially influencing the output power. Varying or controlling the output power may comprise control of output voltage and/or output current. It is an advantage of embodiments according to the present invention that the two parameters output power and switching frequency may be altered substantially independent of each other. The latter may be especially suitable for gas discharge lamps, such as e.g. HID lamps. Embodiments of the present invention may be especially suitable -although not being limited thereto -for operating a device at frequencies where acoustic resonance may be an issue, and for use in combination with a detection unit for such acoustic resonance, as e.g. described in PCT W02007/1 28472A1.
In some embodiments, the resonant converter may be adapted for actively varying or controlling or using at least one capacitor or at least one inductor of the resonant circuit.
The resonant circuit according to embodiments of the present invention may comprise variable and/or actively controllable resonant elements.
In some embodiments, controlling at least one resonating element may comprise controlling a value of the at least one resonating element. In some embodiments, controlling at least one resonating element may comprise controlling whether or not the at least one resonating element is connected in the resonant circuit and therefore controlling whether or not it can contribute. In some embodiments, the resonant converter may comprise a plurality of resonating elements in the resonant circuit and controlling at least one resonant element may comprise connecting one or more of the resonant elements by applying one or more switches. Controlling or actively controlling may thus be controlling whether or not resonant elements are connected in or contribute in the resonant circuit.
In embodiments of the present invention, the resonant circuit may be positioned between at least one switch of the resonant converter and the device to be driven. The resonant converter may be a converter comprising only one switch. Alternatively, the resonant converter may be a converter comprising two or more switches, e.g. two switches or four switches.
In some embodiments of the present invention, a converter may be provided comprising an additional control loop for separately and/or independently controlling one of the output power and/or the switching frequency, while the other is controlled separately and/or independently using active variation and/or control of an impedance of a resonant circuit in a resonant converter.
By way of illustration, the present invention not being limited thereto, examples of resonant converters according to embodiments of the present invention are described below with reference to figures 3 to 11.
Figure 3 shows a generic implementation of a serial resonant converter with variable resonant elements. This is an example of a resonant converter with variable resonance frequencies that can be varied continuously. In the present example, this is established by the resonant capacitor being a parasitic capacitor of a high voltage drain source mosfet. Due to the negative gate-source voltage, the transistor is always off and the more negative the voltage, the more charge is accumulated and the higher the capacitor becomes. Since high voltage mosfets have a parallel diode over the drain source, two mosfets may be put back to back to avoid a current path through the parallel diodes. The parasitic drain source capacitor can be varied by changing the gate voltage of the mosfet. By applying a negative voltage on the gate the mosfet is kept off and by varying the negative voltage the parasitic drain source capacitor can be influenced. This variable drain source capacitor can be used in a control loop to change the resonant frequency of the resonant circuit.
Figure 4 show an AC analysis of the resonant circuit in figure 3. The negative voltage of the voltage source between the gate and the source of the two back to back mosfets is changed. The simulation was done for 3 negative voltages resulting in 3 separate AC characteristics of the resonant circuit. The resonant peak is shifting from 41 0kHz to 370kHz with varying the gate voltage from -5V to OV with one value in between.
These curves show also that with a fixed frequency of E.g. 420kHz above the resonance peak, the output power the impedance and output power can be changed by going from the left to the right curve. As can be seen out of the phase curves in figure 4 it is necessary that the switching frequency is above the resonance peak (=top of the power curve) to have a phase shift of -9Odeg. Due to this phase shift the current is lagging on the input voltage resulting in zero voltage switching.
Figure 5 shows an implementation of a resonant fly-back /forward converter with variable resonant elements where the resonant capacitor is split up in separate values and can be switched in parallel with a fixed resonant capacitor. This is an example of a resonant converter with variable resonance frequencies that can be varied with discrete values. To switch the capacitor in parallel with the fixed capacitor a back to back high voltage npn of an opto-coupler is put in series with the switching capacitor. By putting two opto-couplers outputs back to back a floating switch is generated and the switch can be controlled via the input photodiodes of the opto-couplers by a low voltage driver.
Figure 6 shows a transient analysis of the output voltage of a resonant fly-back /forward converter with discrete resonant elements. The discrete resonance frequencies are determined by switching one or two capacitors in parallel with the fixed resonant capacitor. The figure shows the output voltage decreasing by switching one capacitor in parallel at time T=l2Oiis and releasing the capacitor at T=18Ois. By doing this the impedance of the resonance circuit increases and the output voltage decreases. This implementation can be used in a closed loop with constant output power regulation. By changing the resonant circuit and impedance by switching a parallel capacitor the controller will change the frequency to compensate and keep the output power constant.
Figure 7 shows an implementation of a resonant fly-back /forward converter with variable resonant elements where the resonant capacitor is build up by a parasitic capacitor of two back to back high voltage drain source nmos mosfets M3 and M4. To control the negative gate voltage on the mosfets a drive circuit is added. The drain voltage of the back to back connected mosfets is put on a gate of a floating pmos Ml. This floating pmos acts as a source follower that level shifts the gate voltage with the Vt of the pmos.
The source of the pmos is connected to the gate of an nmos M8 that acts as a source followers that level shifts the gate voltage with the Vt of the nmos The source of the nmos is connected to the resistor Ri. Over this resistor a voltage is generated via a controlled cascoded current source. The voltage over the resistor is connected to the gates of the floating back to back nmos M3 and M4 devices. By controlling the current through Ri, a variable negative gate source voltage on the back to back mosfets can be generated. By generating a variable negative gate source voltage the parasitic drain source capacitor of the back to back mosfets can be influenced. This can be seen in Figure 8. The source voltage of the back to back mosfets M3 and M4 gate voltage is the top curve in Figure8.
The gate voltage of the back to back mosfets M3 and M4 gate voltage is the bottom curve.
At time T=16tts the current trough the resistor Ri is increased via a cascoded current source, controlled by an opto coupler. By controlling the current through the opto coupler a negative voltage can be generated on the resistor of the source follower. This negative voltage is applied to the gates of the back to back mosfets. This negative voltage between the gate and the source of the back to back mosfets can be varied by varying the current through the opto coupler and can be build in a control loop to control the variation of the parasitic capacitor and the overall power conversion of the converter.
Further alternative embodiments is shown in Figure 9. Figure 9 is an alternative embodiment for figure 5 where the back to back opto coupler npn transistors are replaced by back to back nmos switches. The control of the gates of the nmos switches is done by a cascoded floating resistor. The current through the resistor is controller by a cascaded switched current source. By activating the gates of switches Ml and M6 the current is flowing through the pmos cascode and is generating a voltage over the floating resistor that is connected between the gates and the sources of the back to back nmos devices.
Activating the switches Ml and M6 is activating the back to back switches M3 and M4.
Figure 1 0 shows a transient analysis of the output voltage of a resonant fly-back /forward converter with discrete resonant elements. The discrete resonance frequencies are determined by switching one capacitor in parallel with the fixed resonant capacitor and the activation of the parallel capacitor is realised via a back to back nmos device. The figure shows the output voltage decreasing by switching one capacitor in parallel at time T=8Oiis and releasing the capacitor at T=l2Oiis. By doing so, the impedance of the resonance circuit increases and the output voltage decreases. This implementation can be used in a closed loop with constant output power regulation. By changing the resonant circuit impedance by switching a parallel capacitor the controller will change the frequency to compensate and keep the output power constant Figure 11 is shown a total implementation of a control algorithm for controlling a gas discharge system. The lamp stability is monitored via the optical sensor, amplified and evaluated with a filtering circuit. Once acoustic resonance is detected the output of amplifier goes high and the microcontroller takes action by activating the switch on the parallel resonance capacitors. By activating one or more switches the resonant frequency shifts and the impedance of the resonant circuit changes resulting in a variation of the output voltage. The power control loop that regulates a constant power to the lamp will react on this change by changing the frequency to keep the output power constant and to feed the lamp with a constant lamp voltage and current.
By this resonant converter with variable resonant elements topology, also additional features can be implemented. Dimming of the lamp can be done by a fixed frequency and by adapting the resonating elements. Igniting of the lamp can be done by using the fly-back during start-up and building a high voltage on the secondary side of the transformer.
To keep the zero voltage switching available during all operating conditions the switching frequency must be higher than the resonant frequency at all times. Therefore special measure may be taken in the control loop when varying the resonant elements. An easy way to control the switching frequency may be checking the zero crossing of the voltage and current and increasing the frequency till the current is lagging behind the voltage. At that moment the circuit is behaving as an inductive circuit. Another option is to shift the resonance frequency from high to low when making steps. By this way it may be guaranteed that the current always has a negative phase against the voltage.
The advantages, of controlling a gas discharge system with one of these resonant converter topologies are plural. The bill of material is reduced due to reduction of the amount of switching devices, the reduction of transformer size and inductive elements due to the higher switching frequency. The most significant reduction is the avoidance of a buck converter that is required to bring the voltage down after the EMI boost converter In other converter types this buck converter brings the DC voltage down to the level of the lamp operational voltage. The overall efficiency of a high frequent resonant converter is higher then a high frequent push pull converter due to the soft switching technique and the reduced conductive losses in the switching elements.
In some embodiments according to the first aspect, the resonant converter may be adapted for actively varying or controlling, during operation, the input voltage and/or input current or input power of the resonant circuit so as to allow varying one of the output power of the device and the switching frequency, while keeping the other substantially constant or without substantially influencing the other. The resonant converter may be adapted for actively varying or controlling, during operation, the input voltage and/or input current so as to allow varying one of the output power of the device and the resonance frequency, while keeping the other substantially constant or without substantially influencing the other. In other words, the resonant converter may be adapted for varying the output power of a device while keeping the switching frequency constant or without substantially influencing the switching frequency, while in other embodiments, or the resonant converter may be adapted for varying the switching frequency, e.g. for driving the device in stable frequency regions where the problem of instable frequencies due to acoustic resonance is not present, and for maintaining the output power value constant or without substantially influencing the output power. Varying or controlling the output power may comprise control of output voltage and/or output current. It is an advantage of embodiments according to the present invention that the two parameters output power and switching frequency may be altered substantially independent of each other. The latter may be especially suitable for gas discharge lamps, such as e.g. HID lamps. Embodiments of the present invention may be especially suitable -although not being limited thereto -for operating a device at frequencies where acoustic resonance may be an issue, and for use in combination with a detection unit for such acoustic resonance, as e.g. described in POT WO W02007/1 28472A1.
In some embodiments, the resonant converter may comprise input voltage and/or input current control circuits. In some embodiments of the present invention, the resonant circuit may be positioned between at least one switch of the resonant converter and the device to be driven. The converter may be a converter comprising only one switch.
Alternatively, the converter may be a converter comprising two or more switches, e.g. two switches or four switches.
In some embodiments of the present invention, a converter may be provided comprising an additional control loop for separately and/or independently controlling one of the output power and/or the switching frequency, while the other is controlled separately and/or independently using active variation and/or control of the input parameters ot the converter, e.g. of a resonant circuit in a resonant converter.
By way of illustration, the present invention not being limited thereto, examples of converters according to embodiments of the present invention are described below with reference to figures 12 to 13.
Figure 12 shows a generic implementation of a serial resonant converter with variable input voltage control. This is an example of a resonant converter with variable input voltage that can be varied continuously. In the present example, this is established by a -boost converter that regulates the input voltage of the resonant converter. The boost converter regulates the DC input voltage of the resonant converter on capacitor DC2 and is controlled via a pulse width modulating (PWM) signal. The PWM signal is regulated in a feedback loop from the resonant converter output. When changing the frequency of the resonant switching elements upwards the peak output voltage and output power decreases. The feedback loop compensates the input voltage to keep the peak output voltage constant. The compensation is established by increasing the pulse width of the PWM signal of the boost converter. It is clear that this loop is a slow loop since there is a decoupling capacitor DC2 between the output voltage of the boost converter that acts as the input voltage of the resonant converter. When e.g. acoustic resonance is detected in the HID lamp the operating frequency of the resonant converter needs to be shifted to an acoustic resonance free operating frequency, This shift in frequency needs to happen sufficiently slow, so the buck boost converter can compensate the input voltage in time to keep the output voltage and power constant.
Figure 13 shows a simulation of the output voltage of the converter. This output voltage variation is a result of an input voltage increase from 200Vdc to 300Vdc, applied on the resonant converter input at time T=300iis. This input voltage increase results in a peak output voltage increase. At time=500iis the switching is increased from 50Khz to 100Khz resulting in an output voltage decrease. This simulation shows that the output voltage and power can be kept constant by compensating the switching frequency shift by regulating the input voltage. This simulation shows also that the output power can be regulated by the varying the input voltage and by keeping the switching frequency constant.
Figure 14 shows an implementation of a resonant fly-back /forward converter with controllable input current. It is an advantage of this embodiment that it allows to control the load with a symmetrical 50 duty cycle signal while other converter topologies control the input current by varying the pulse width of the control signal. The input current is split up in separate values via different switchable cascoded resistors acting as switchable current sources. These switchable current sources can be added in parallel by switching the switches in series with the cascoded resistor. This is an example of a resonant converter with variable input current that can be varied with discrete values. The pulse generator with variable frequency is generating the gate drive signal for transistors Ml and M4. The gate drive signal for transistor Ml is passed via a nand gate and can be digitally switched on or off by single pulse generator or a microcontroller.
Figure 15 shows a simulation result of the output voltage of the converter. The output voltage increase is realised by a current increase by switching in parallel the additional 0.1 Ohm switchable cascoded resistor acting as a switched current source with the fixed 0.2 Ohm switchable cascoded resistor acting as a switched current source. The additional switched current source is connected at T=1 5Oiis and after a transient the new output voltage and power of the converter is increasing. This simulation shows also that the output power can be regulated by varying the input current and by keeping the switching frequency constant.
Figure 1 6 shows an implementation of a resonant fly-back /forward converter with variable input current where the input current is varied by controlling the cascode voltage of the cascode in series with the current switching device. It is an advantage of this embodiment that it allows to control the load with a symmetrical 50 duty cycle signal while other converter topologies control the input current by varying the pulse width of the control signal. By controlling the voltage of the cascode the current through the switching device can be regulated by regulating the maximum drain source voltage of the switching device.
Figure 17 shows a simulation result of the cascode voltage and the output voltage of the converter. By increasing the cascode voltage from 8V to by on T=l5Oiis the input current of the fly-back converter is increasing and resulting in an increase of the output voltage and power. This simulation shows also that the output power can be regulated by varying cascode voltage and the input current and by keeping the switching frequency constant.
Figure 1 8 shows an implementation of a resonant fly-back /forward converter with variable input current where the input current is varied by controlling the cascode voltage of the cascode in series with the current switching device. By controlling the voltage of the cascode the current through the switching device can be regulated by regulating the maximum drain source voltage of the switching device. The control voltage is generated from a digital word of a microcontroller that is translated to analog signal via a DAC and is connected via an amplifier to the gate of the cascode.
Figure 19 shows a total implementation of a control algorithm for controlling a gas discharge system, in the present example being a gas discharge lamp. The lamp stability is monitored via the optical sensor, amplified and evaluated with a filtering circuit. Once acoustic resonance is detected the output of the amplifier goes high and the microcontroller takes action by activating an additional switchable cascoded resistor. By activating one or more switches of the switchable cascoded resistors the output power tends to shift and the control loop will adapt the frequency to keep the output voltage and power constant and to feed the lamp with a constant lamp voltage and current.
By this resonant converter with variable input voltage or input current control topology, also additional features can be implemented. Dimming of the lamp can be done by a fixed frequency and by adapting the input current of input voltage. Igniting of the lamp can be done by using the fly-back during start-up and building a high voltage on the secondary side of the transformer.
To keep the zero voltage switching available during all operating conditions the switching frequency must be higher than the resonant frequency at all times. Therefore special measure may be taken in the control loop when varying the frequency. An easy way to control the switching frequency may be checking the zero crossing of the voltage and current and increasing the frequency till the current is lagging behind the voltage. At that moment the circuit is behaving as an inductive circuit.
The advantages, of controlling a gas discharge system with one of these converter topologies are plural. The bill of material is reduced due to reduction of the amount of switching devices, the reduction of transformer size and inductive elements due to the higher switching frequency. The most significant reduction is the avoidance of a buck converter that is required to bring the voltage down after the EMI boost converter In other converter types this buck converter brings the DC voltage down to the level of the lamp operational voltage. The overall efficiency of a high frequent converter is higher then a high frequent push pull converter due to the soft switching technique and the reduced conductive losses in the switching elements.
In one aspect, the present invention also relates to a method or algorithm for driving a device, the method comprising varying one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other. The method may comprise actively or passively controlling at least one input parameter of a resonant circuit and/or at least one resonant component in a resonant circuit of the converter so as to vary one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other. In some embodiments, the method comprises controlling one of an output power and/or a switching frequency by actively varying or controlling a resonating element in a resonant circuit of a resonant converter while simultaneously maintaining the value of the other (switching frequency and/or output power) substantially constant. In other embodiments, the method comprises controlling one of an output power and/or switching frequency by actively varying or controlling an input parameter, e.g. input current or input voltage of the resonant circuit thereof, if present, while simultaneously maintaining the value of the other (switching frequency and/or output power) substantially constant, The method and/or algorithm may comprise method steps having the functionality of the converter or converter topology as described above.
In another aspect, the present invention also relates to a system for controlling a gas discharge system, the system comprising an input port for receiving information regarding at least one unstable frequency or frequency band and a converter or converter topology as described above. The system may alternatively comprise part of or the complete detection system for detecting instabilities in driving frequency or frequency band as described in W02007/1 28472, the subject matter thereof being incorporated herein by reference.
In another aspect, the present invention relates to a converter for driving a high intensity discharge lamp (HID), the converter comprising exactly one switch. Such a converter may be a converter as described above.
According to embodiments of the invention, a converter as described above may be used for implementing a resonant AC/DC converter or DC/DC converter with fixed frequency.
Making the frequency fixed, this provides the advantage that filters EMI or EMC can be more easily implemented. The requirements on the EMI or EMC filters can be relaxed as less sharp filters are needed.

Claims (64)

  1. CLAIMS1. A resonant converter for driving a device, the resonant converter being adapted for varying one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other.
  2. 2. A resonant converter according to claim 1, wherein the resonant converter comprises a resonant circuit and whereby the resonant converter is adapted for actively or passively controlling a parameter related to the resonant circuit so as to vary one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other.
  3. 3. A resonant converter according to any of claims 1 to 2, wherein the resonant converter is adapted for actively or passively controlling at least one input parameter of a resonant circuit of the resonant converter and/or at least one resonant component in a resonant circuit of the converter so as to vary one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other.
  4. 4. A resonant converter according to claim 3, wherein the converter is adapted for actively or passively controlling at least one input parameter and wherein a value of the at least one input parameter can be varied or controlled continuously.
  5. 5. A resonant converter according to claim 3, wherein the converter is adapted for actively or passively controlling at least one input parameter and wherein a value of the at least one input parameter can be varied or controlled stepwise or discrete.
  6. 6. A resonant converter according to any of claims 3 to 5 wherein the converter is adapted for actively or passively controlling at least one input parameter and wherein the at least one input parameter comprises an input voltage.
  7. 7. A resonant converter according to any of claims 3 to 6 wherein the converter is adapted for actively or passively controlling at least one input parameter and wherein the at least one of the input parameters comprises an input current
  8. 8. A resonant converter according to any of the previous claims, wherein the converter is adapted for actively or passively controlling at least one input parameter and wherein the converter is adapted to maintain an output power of the device at substantially constant or predetermined value, while at the same time being adapted for varying, during operation, a switching frequency of the converter.
  9. 9. A resonant converter according to any of the previous claims, wherein the converter is adapted for actively or passively controlling at least one input parameter and wherein power regulation of the device is achieved by changing the value of one of the input parameters.
  10. 1 0. A resonant converter according to any of the previous claims, wherein the converter is adapted to maintain the switching frequency of the converter at a substantially constant or predetermined value while at the same time being adapted for varying, during operation, an output power of the converter.
  11. 11. A resonant converter according to any of the previous claims wherein the converter is adapted for actively or passively controlling at least one input parameter and wherein the circuit is positioned between at least one switch of the converter and the device to be driven.
  12. 12. A resonant converter according to claim 11, wherein the converter comprises exactly one switch.
  13. 13. A resonant converter according to claim 11, wherein the converter comprises exactly two switches or exactly four switches.
  14. 14. A resonant converter according to any of the previous claims, wherein the converter is adapted for actively or passively controlling at least one input parameter and wherein the input parameters are actively variable or actively controllable and part of a control loop for controlling one of an output power or a switching frequency.
  15. 1 5. A resonant converter according to any of the previous claims, wherein the converter is adapted for actively or passively controlling at least one input parameter and wherein the switching frequency for the converter can be controlled using a feedback loop adapted for keeping the power constant by changing the frequency.
  16. 1 6. A resonant converter according to any of the previous claims, wherein the converter is adapted for actively or passively controlling at least one input parameter by changing the total input power by applying several switchable cascoded resistors in parallel acting as switchable current sources and by connecting or disconnecting the switchable cascoded resistors, e.g. with a switch in series with the resistors.
  17. 1 7. A resonant converter according to any of the previous claims, wherein the converter is adapted for actively or passively controlling at least one input parameter by changing the total input power by varying a cascode voltage of the cascode on the switching devices acting as switchable current sources.
  18. 18. A resonant converter according to any of claims 16 to 17, wherein the converter comprises a buck boost converter to vary the input voltage.
  19. 19. A resonant converter according to any of the previous claims, the resonant converter comprising a resonant circuit, wherein the resonant converter is adapted for actively varying or actively controlling, during operation, an impedance by actively varying or controlling at least one resonating element in the resonant circuit so as to allow varying one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other.
  20. 20. A resonant converter according to claim 19, wherein the at least one resonating element comprises a capacitor and/or inductor.
  21. 21. A resonant converter according to claim 20, wherein a value of the at least one resonating element can be varied or controlled continuously.
  22. 22. A resonant converter according to claim 20, wherein a contribution of the at least one resonating element to the impedance of the resonant circuit can be varied or controlled continuously.
  23. 23. A resonant converter according to claim 20, wherein a value of the at least one resonating element can be varied or controlled stepwise or discrete.
  24. 24. A resonant converter according to claim 20, wherein a contribution of the at least one resonating element to the impedance of the resonant circuit can be varied or controlled stepwise or discrete.
  25. 25. A resonant converter according to any of claims 19 to 24 wherein the at least one resonating element is a capacitor.
  26. 26. A resonant converter according to any of claims 19 to 24 wherein the at least one resonating element is an inductor, e.g. coil.
  27. 27. A resonant converter according to any of claims 19 to 26, wherein the resonant converter is adapted to maintain an output power of the device at substantially constant or predetermined value, while at the same time being adapted for varying, during operation, a switching frequency of the device.
  28. 28. A resonant converter according to any of claims 19 to 27, wherein power regulation of the device is achieved by changing the value of one of the resonating elements.
  29. 29. A resonant converter according to any of claims 19 to 28, wherein the resonant converter is adapted to maintain the switching frequency of the device at a substantially constant or predetermined value while at the same time being adapted for varying, during operation, an output power of the device.
  30. 30. A resonant converter according to any of claims 1 9 to 29 wherein the resonant circuit is positioned between at least one switch of the resonant converter and the device to be driven.
  31. 31. A resonant converter according to claim 30, wherein the resonant converter comprises exactly one switch.
  32. 32. A resonant converter according to claim 30, wherein the resonant converter comprises exactly two switches or exactly four switches.
  33. 33. A resonant converter according to any of claims 1 9 to 32, wherein the resonant circuit or at least the at least one of the resonant elements that is actively variable or actively controllable is part of a control loop for controlling one of an output power or a switching frequency.
  34. 34. A resonant converter according to any of claims 19 to 33, wherein the resonance frequency for the converter can be controlled by actively varying or actively controlling the at least one of the resonant elements.
  35. 35. A resonant converter according to any of claims 19 to 34, wherein the resonant converter comprises a plurality of resonating elements in the resonant circuit and wherein controlling at least one resonant element comprises connecting one or more of the resonant elements by applying a switch.
  36. 36. A resonant converter according to claim 35, wherein controlling the at least one resonant element comprises changing the impedance by applying several capacitors in parallel and by connecting or disconnecting the capacitors, e.g. with a switch in series with the capacitor.
  37. 37. A resonant converter according to claim 36, wherein controlling the at least one resonant element comprises changing the impedance by applying several inductors in parallel or in series, e.g. by connecting or disconnecting the inductors with a switch in parallel or in series with the coil.
  38. 38. A resonant converter according to any of claims 19 to 37, wherein the impedance is actively varied or controlled using a parasitic capacitor of a semiconductor device where the capacitor value can be changed by changing another parameter of the semiconductor device.
  39. 39. A resonant converter according to claim 38, wherein the semiconductor device is a switch and/or transistor.
  40. 40. A resonant converter according to any of claims 19 to 39, wherein the at least one resonant element is a MOSFET gate drain parasitic capacitor.
  41. 41. A resonant converter according to any of claims 19 to 40, wherein the at least one resonant element is a MOSFET gate drain parasitic capacitor as series element in a parallel serial resonant converter and whereby the impedance of the resonant circuit can be actively controlled or varied by applying a negative voltage on a gate-source of the MOSFET to change the parasitic drain-source capacitor of the MOSFET.
  42. 42. A resonant converter according to any of claims 19 to 41, wherein the at least one resonant element is a MOSFET gate drain parasitic capacitor as parallel element in a resonant fly-back converter and whereby the impedance of the resonant circuit can be actively controlled or varied by applying a negative voltage on the gate-source to change the parasitic drain-source capacitor of the MOSFET that is used as a parallel element with a transformer in a resonant fly-back converter.
  43. 43. A method or algorithm for driving a device, the method comprising varying one of the output power of the device and/or the switching frequency, while keeping the other substantially constant or without substantially influencing the other.
  44. 44. A method or algorithm for driving a device, the method comprising actively or passively controlling a parameter related to a resonant circuit of a resonant converter so as to vary one of the output power of the converter and/or the switching frequency of the converter, while keeping the other substantially constant or without substantially influencing the other.
  45. 45. A method or algorithm according to any of claims 43 to 44, the method comprising actively or passively controlling at least one input parameter and/or at least one resonant component in a resonant circuit of the converter so as to vary one of the output power of the converter and/or the switching frequency of the converter, while keeping the other substantially constant or without substantially influencing the other.
  46. 46. A method or algorithm according to any of claims 43 to 45, the method comprising actively or passively controlling at least one input parameter.
  47. 47. A method or algorithm according to claim 46, the method or algorithm comprising actively varying the input parameters like input voltage or input current so as to vary one of the output power of the converter and/or the switching frequency of the converter, while keeping the other substantially constant or without substantially influencing the other.
  48. 48. A method or algorithm according to any of claims 46 to 47, the method comprising altering the switching frequency of the converter to avoid acoustic resonance in a gas discharge system and regulating the output power by another control loop that is changing an input voltage or input current of the converter or a resonant circuit thereof.
  49. 49. A method or algorithm according to claim 46 to 48 comprising altering the switching frequency in a converter to avoid acoustic resonance in a gas discharge system and keeping the output power constant by changing the value of input voltage or input current.
  50. 50. A method or algorithm according to any of claims 43 to 49, the method or algorithm comprising actively varying or actively controlling, during operation, an impedance of a resonant circuit of a the converter by actively varying or controlling at least one resonating element in the resonant circuit so as to vary one of the output power of the converter and/or the switching frequency of the converter, while keeping the other substantially constant or without substantially influencing the other.
  51. 51. A method or algorithm according to claim 50 comprising altering the switching frequency of the resonant converter to avoid the acoustic resonance in a gas discharge system and regulating the output power by another control loop that is changing the impedance of the resonant circuit.
  52. 52. A method or algorithm according to claim 50 comprising altering the switching frequency in a resonant converter to avoid acoustic resonance in a gas discharge system and keeping the output power constant by changing the value of resonant elements.
  53. 53. A method or algorithm according to any of claims 43 to 52 for controlling a gas discharge system.
  54. 54. A method or algorithm according to any of claims 43 to 52 for igniting a gas discharge system.
  55. 55. A method or algorithm according to any of claims 43 to 52 for dimming purposes.
  56. 56. A method or algorithm according to any of claims 43 to 55, wherein the method comprises starting on the highest resonance frequency of the frequency range that is covered by changing the resonant elements.
  57. 57. A method or algorithm according to any of claims 43 to 56, wherein the method comprises detecting at least one unstable frequency point or band for driving the device and varying a switching frequency of the converter taking into account the detected at least one unstable frequency point or band.
  58. 58. A method or algorithm according to claim 57, wherein the detecting of the at least one unstable frequency point or band is performed using a method as set forth in
  59. 59. Use of a resonant converter according to any of claims 1 to 42, for controlling a gas discharge system.
  60. 60. The use according to claim 59 of a converter, the converter being a resonant fly-back converter.
  61. 61. Use of a resonant converter according to any of claims 1 to 42, for igniting a gas discharge system.
  62. 62. The use according to claim 61 of a converter, the converter being a resonant fly-back converter.
  63. 63. Use of a resonant converter according to any of claims 1 to 42, for dimming a gas discharge system.
  64. 64. Use of a resonant converter according to any of claims 1 to 42, for implementing a resonant AC/DC converter or DC/DC converter with fixed frequency.
GB0904033A 2009-03-09 2009-03-09 Resonant power converter having variable output power or switching frequency Withdrawn GB2468490A (en)

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10536095B1 (en) 2017-04-20 2020-01-14 Maxim Integrated Product, Inc. Resonant converter with negative current feedback
CN116491056A (en) * 2020-11-06 2023-07-25 日产自动车株式会社 Resonance type power conversion device

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US6008589A (en) * 1996-03-05 1999-12-28 California Institute Of Technology Single-switch, high power factor, ac-to-ac power converters
US6246599B1 (en) * 2000-08-25 2001-06-12 Delta Electronics, Inc. Constant frequency resonant inverters with a pair of resonant inductors
US20020014861A1 (en) * 1998-10-13 2002-02-07 Shu-Yuen Ron Hui Dimming control of electronic ballasts
US20020149890A1 (en) * 2001-03-09 2002-10-17 Susumu Kaneko Resonance type power supply unit

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Publication number Priority date Publication date Assignee Title
US6008589A (en) * 1996-03-05 1999-12-28 California Institute Of Technology Single-switch, high power factor, ac-to-ac power converters
US20020014861A1 (en) * 1998-10-13 2002-02-07 Shu-Yuen Ron Hui Dimming control of electronic ballasts
US6246599B1 (en) * 2000-08-25 2001-06-12 Delta Electronics, Inc. Constant frequency resonant inverters with a pair of resonant inductors
US20020149890A1 (en) * 2001-03-09 2002-10-17 Susumu Kaneko Resonance type power supply unit

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10536095B1 (en) 2017-04-20 2020-01-14 Maxim Integrated Product, Inc. Resonant converter with negative current feedback
CN116491056A (en) * 2020-11-06 2023-07-25 日产自动车株式会社 Resonance type power conversion device
EP4243260A4 (en) * 2020-11-06 2024-01-10 Nissan Motor Resonance-type power conversion device

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