KR101035017B1 - Half-bridge power converter for driving led by series-resonant connection of inductor, inductor and capacitor - Google Patents

Abstract

PURPOSE: An LLC half-bridge power converter for an LED is provided to expand a frequency usage range using a common CMOS timer, thereby reducing manufacturing costs. CONSTITUTION: An output unit(110) generates pulse power by controlling the frequency of a controller(100). The pulse power of the output unit is resonated by a LLC resonant unit(120). The resonated pulse power is rectified into DC power by a rectifying unit(130). The power of the rectifying unit is fed back to a controller through a feedback unit(140). The rectifying unit includes a soft start setting unit, a level detecting unit, an opto-coupling for a feedback signal, a controller frequency varying unit, and a protection circuit.

Description

Half-Bridge Power Converter for Driving LED by Series-Resonant connection of Inductor, Inductor and Capacitor}

The present invention relates to a power converter (SMPS) for supplying DC power required for the operation of general electronic devices such as a computer, a TV, an LED lamp, and more particularly, in an LLC half-bridge (LLC.HB resonant) type power converter. Using a CMOS timer with a 50% duty cycle of the controller and a frequency range of 50Khz ~ 1Mhz, the capacity of the capacitor for variable frequency of the CMOS timer is varied based on the output level. It's about an ELC halfbridge power converter for LEDs that keeps the output.

The current status of domestic and international applications of power converters for lighting LED lamps (2009) is, in fact, high efficiency and low energy consumption due to power converters that do not comply with the undefined specifications of LEDs and the required conditions. The description is colorless.

The cause of the current situation is a problem of the LED itself, but the short life of the power converter (power converter) and a high failure rate is the main cause. In view of such a situation, securing the high efficiency and high stability of the power converter must be the highest priority at hand.

Representative PWM power converters which are currently used most are a flyback method, a forward method, and a half bridge method. It is easy to design when the use frequency is within 100Khz, but the efficiency is more than 80%, the volume ratio is large and the manufacturing price is expensive.

On the other hand, the LC half-bridge (LLC, HB) method that has recently been commercialized as a power supply for driving LED lamps is known.

1 is a circuit diagram of a power converter for driving an EL half-bridge type LED according to the prior art.

As shown therein,

The controller 50 generates a predetermined frequency signal to control the output of the DC power supply, and the frequency signal of the controller 50 is input to the primary coil of the first transformer T1, and outputs of the two secondary coils. A power output unit 10 for generating an AC pulse signal by switching the DC power supply DC through two switching transistors FET1 and FET2 controlled by the control unit; An LLC resonator 20 for resonating the AC pulse signal of the power output unit 10 through an inductor L1, a primary coil and a resonant capacitor C1 of the second transformer 2, and the LLC resonator A rectifier for rectifying the outputs of both ends of the secondary coil of the second transformer T2 of (20) by the diodes D4 and D5 and smoothing it through the smoothing capacitor C4 to perform DC output (+ 12V) for load driving. 30 and the output of the rectifier 30 are divided by the distribution resistors R4 and R5 to detect the output level by the level detecting element TL431, and outputting the output of the level detecting element TL431. And an output level feedback unit 40 for feeding back to the control IC 50 through the coupler PC1.

In the conventional LC half-bridge (LLC_HB) power converter, when the primary coil of the first transformer T1 is controlled by the frequency control of the control IC 50, power is supplied to two secondary coils by DC power. This is induced, thereby generating a pulse in each of the two switching elements (FET1, FET2), which is resonated in the LLC resonator 20, rectified in the rectifier 30 to output the DC power source for driving the load. Since the operation of the LC half-bridge power converter is a general drive, it will not be described in detail.

In the LC half-bridge power converter as described above, the operation of the feedback unit 40 detects the output level by the distribution resistors R4 and R5, and the divided voltage is set by the level detection element TL431. In this case, the level detecting device TL431 is turned on to operate the optocoupler PC1. When the optocoupler PC1 is operated, the controller 50 fixes the resonance frequency so that the output level is fixed.

However, when a circuit failure occurs and the feedback signal is not applied to the controller 50 despite being above the output level (DC + 12V) set by the feedback unit 40, the controller 50 is moved in the direction in which the output level is increased. The lack of continuous control creates the risk of secondary accidents.

The control method used in the conventional LC half-bridge power converter is switched to the state of the maximum power (Power Max) at the time set by the soft-start function of the controller. At this time, the output of the rectifier 30 is monitored by the feedback unit 40 and fed back to the controller 50 by the voltage and current set value, the controller 50 is controlled to maintain the set voltage output. This control method causes a problem that the output voltage exceeds the set value when the output side voltage detection function is lost or other problems occur and the feedback unit 40 does not operate. These results can damage equipment using power converters.

In addition, the use of the controller IC, which determines all the performance of the DC power converter (S.M.P.S), is more advanced than the conventional flyback, forward, and half bridge methods, and is low and expensive. For this reason, it was difficult to approach low volume rate at low cost.

Power converters that supply DC power required for the operation of general electronic devices such as computers, TVs, and LED lamps achieve low power loss, high efficiency, low cost and minimum volume, considering the current trends and demands of future users. It is an immediate challenge.

The present invention aims to provide a high efficiency (90% or more), design, and minimum volume power converter circuit by using a C MOS timer (Timer IC) to extend the frequency use range up to 50KHz ~ 1Mhz.

In addition, the present invention configures the feedback circuit as an active circuit so that the feedback signal is applied to the controller as an on signal until the output is maximum, and the feedback signal is applied to the controller as an off signal when the output is maximum, thereby causing secondary side failure. It is to provide a power converter to prevent the occurrence of overvoltage at the time.

Based on the frequency control of the controller, a pulse output is generated at the output section, the pulse output of the output section is resonated through the LLC resonator section, rectified through the rectifier section at the secondary side of the resonator section, and a DC power output is output to the load side. In the LED half-bridge power converter configured to feed back to the controller through a feedback unit,

The controller has a frequency using a range of 50Khz ~ 1Mhz, C MOS timer (Timer IC) for controlling to increase the output by lowering the frequency of the output until the output of the rectifier reaches a set value based on the soft start and ,

The feedback unit detects the output of the rectifier and generates an on signal until reaching a set value, and controls the frequency output from the controller to the output unit in a lowering direction. When the output of the rectifier reaches a set value, the feedback unit is turned off. And generating a signal to maintain a frequency output from the controller to the output unit to control the output of the rectifier to be maintained at a set level.

The feedback unit,

A soft start setting unit for integrating the output of the rectifying unit;

A level detecting unit for distributing the output of the rectifying unit through a divider resistor and detecting whether the divided voltage level is equal to or higher than the set level and bypassing the output of the soft start setting unit when the level is detected by the level detecting element. Wow,

An optocoupler for a feedback signal, in which a light emitting element is controlled by an output of the soft start setting unit controlled by the level detecting unit, and a feedback signal is generated by the light receiving element;

A controller frequency for distributing an external DC power supply through a distribution resistor to apply a bias potential at the other end of the frequency variable capacitor of the controller and to control the bias at the other end of the frequency variable capacitor by the light receiving element of the feedback signal optocoupler. Variable part,

When the output pulse of the output unit is input via the reverse diode or more than the set value is characterized in that it comprises a protection circuit for turning off and protecting the light receiving element of the optocoupler.

The present invention configured as described above has a high efficiency (90%) by extending the frequency usage range from 50KHz to 1Mhz by using a conventional C MOS timer IC without using a dedicated control IC in the ELC half-bridge power converter for LEDs. Above), design accuracy, minimum volume power converter (SMPS) circuit is provided, and manufacturing cost can be reduced. In addition, the present invention is configured by the circuit of the feedback unit active circuit, initially lowering the frequency of the controller by the on-signal to increase the output, and when the output reaches the rated value, the feedback unit is turned off to maintain the frequency to the secondary side failure Even if a feedback part failure occurs, safety is secured because it does not go over the rated voltage.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In recent years, AC / DC or DC / DC power converters have faced the demands of users for low cost and high efficiency and small volume. The most suitable solution to this challenge is the LLC.HB approach.

However, the IC. LLC.HB IC, which is generally supplied, is a dedicated IC, which is expensive and can be used in a narrow range of 50KHz to 350KHz, and its range of use is not wide. With these ICs, it is difficult to meet various user requirements.

Meeting these requirements requires a low cost, high efficiency, and small volume circuit that meets the most important frequency range of the LLC.HB scheme, 50Khz to 1Mhz.

Accordingly, in the present invention, a circuit of a DC power converter is constructed by applying a CMOS timer (C MOS Timer IC) whose stability has been verified among ICs manufactured in the past 20 years.

FIG. 2 is a diagram of a conventional CMOS timer, which has a 50% duty cycle and has a frequency usage range of 50KHz to 1Mhz, and has been used for a long time with its stability verified. The present invention uses such a CMOS timer. By default, the soft start time is set to a fixed value, and the maximum operation is achieved until the feedback control circuit is activated, regardless of the formation of the secondary DC voltage.

Therefore, it is a core technology of the present invention to include a frequency varying means capable of varying the frequency by the control of the feed ball in the control of the CMOS timer (C MOS Timer IC).

FIG. 3 is a circuit diagram of an EL half-bridge power converter for an LED according to the present invention. As shown in FIG.

Based on the frequency control of the controller 100, a pulse output is generated at the output unit 110, and a pulse output of the output unit 110 is resonated through the LLC resonator 120, so that the secondary side of the LLC resonator 120 is formed. Rectifying through the rectifying unit 130 to output the DC power to the load side, and the LC half-bridge power for the LED configured to feed back the output of the rectifying unit 130 to the controller 100 through the feedback unit 140 In the converter,

The controller 100 has a duty of 50%, the use frequency range is 50Khz ~ 1Mhz based on the capacity change of the frequency variable capacitor (C3), based on the soft start set value set in the feedback unit 140 It is a CMOS timer (C MOS Timer IC) is configured to control the final output level of the rectifier 130 by receiving a feedback signal, the output frequency is changed in accordance with the change of the capacity of the variable capacitor (C3),

The feedback unit 140 detects the output of the rectifier 130 and operates the optocoupler based on the soft start set value. When the output of the rectifier 130 is equal to or higher than the rated set voltage, the opto coupler is turned off. And the capacitance of the variable frequency capacitor C3 of the controller 100 by the optocoupler.

The feedback unit 140,

A soft start setting unit 141 for generating a soft start voltage through the resistor R9 by setting a time constant of the output of the rectifying unit 130 by the resistor R8 and the condenser C9;

The output of the rectifier 130 is distributed through the distribution resistors R10 and R11, and the level detecting element IC2 detects whether the divided voltage level is equal to or higher than the set level, and then through the PNP transistor Q3. A level detector 142 which bypasses the output of the soft start setting unit 141 when the level is higher than the set level;

An optocoupler (OPT) for a feedback signal that receives the output of the soft start setting unit 141 controlled by the level detector 142 to the anode side to control the light emitting device and to generate a feedback signal by the ANP-type light receiving device Wow,

The external DC power is distributed through the distribution resistors R1 and R3 to apply the bias potential of the other end of the frequency variable capacitor C3 of the controller 100 and by the light receiving element of the feedback signal optocoupler OPT. A controller frequency variable part 143 for controlling the bias of the other end of the frequency variable capacitor C3;

The output pulse of the output unit 110 is input through the reverse diodes D3 and D2 and the optocoupler OPT is driven by the reverse diode D1 based on the set values of the capacitor C7 and the resistors R6 and R7. And a protection circuit 144 for controlling the base of the light receiving element.

The controller 100 of the present invention configured as described above is characterized in that it is widely used CMOS timer (C MOS Timer IC), the controller 100 of the CMOS timer (C MOS Timer IC) is a frequency use range Is 50Khz ~ 1Mhz, the duty cycle of the output control pulse is a known timer 50%. The output frequency of the CMOS timer IC is determined by the frequency variable capacitor C3 and the resistor R2 to switch the primary coil of the first transformer T1 of the output unit 110.

The present invention is characterized by varying the frequency by varying the capacitance of the frequency variable capacitor C3. The controller frequency variable part 143 sets the frequency by dividing the external input power supply DC by the resistors R1 and R3 to the other end of the frequency variable capacitor C3 to set the bias. At this time, by controlling the bias applied to the other end of the frequency variable capacitor (C3) by the operation of the opto-coupler (OPT) of the feedback unit 140 to change the capacity of the frequency variable capacitor (C3).

3 of the present invention uses the CMOS timer, which is a 50% duty cycle oscillator, as shown in FIG. 2 for the function of output voltage stabilization. As described above, the frequency variable means includes a capacitor C3 for variable frequency.

As shown in FIG. 4, the frequency variable capacitor C3 is connected to the THR terminal of the CMOS MOS Timer IC, which is the controller 100, and connected to the Q terminal of the CMOS MOS Timer IC. It is connected to the frequency variable capacitor C3 through a resistor R2.

The frequency variation in this state is the frequency variation by the variable of the resistor R2 or the capacitance of the capacitor C3. In the present invention, the variable frequency using the variable capacitance of the capacitor C3 is configured as an embodiment.

A, B and C in Fig. 5 are schematic diagrams of the capacitive variable frequency variable means.

As shown in FIG. 5A, there is a method of varying the capacitor C3 by the feedback unit and a method of varying the variable resistor by the feedback unit by connecting the variable resistor VR to the capacitor C3 as shown in FIG. 5B. They cannot be put to practical use because they have a variable speed limit. Accordingly, the present invention adopts a method of varying the capacitance of the capacitor C3 by using the light receiving element TR of the optocoupler OPT as shown in FIG.

As shown in Fig. 5C, a low frequency (50Khz) is set when the cathode C and the emitter E of the optocoupler TR are turned on by R and C. In the off state of the optocoupler (OPT) light receiving element TR, a high frequency (1 Mhz) is determined by R2 and R3.

When the circuit in this state is determined, the frequency is variable by increasing or decreasing the current of the light emitting element Opto-LED of the optocoupler OPT. That is, when the current of the light emitting device Opto-LED of the optocoupler OPT is minimum, the frequency becomes Hi, and the light emitting device Opto of the optocoupler OPT by the setting of the feedback unit 140 circuit is performed. -LED) The frequency changes from Hi to low by increasing the current. That is, it is possible to satisfy the maximum power (MAX power).

The full wave square frequency of the LC half-bridge (LLC, HB) power converter for LEDs of the present invention is varied using a CMOS Timer IC, but the variable frequency is a resistor R3 at the capacitor C3. And the cathode-emitter (CE) of the optocoupler (Opto-TR) of the optocoupler are connected in parallel to vary the resistance component of the on-to-coupler light-receiving element (Opto-TR). Resistance is variable. That is, the result is that the capacitance of the capacitor C3 is varied. This operation determines the frequency variation of the CMOS timer.

Therefore, in the circuit of the present invention, when the input power (external DC) is turned on, the function of the primary side is to set the soft start of the feedback unit 140 starting from the state where the power of the secondary side is low. The time constant resistor R8 of the unit 141 starts charging the time constant capacitor C9.

The time constant resistor R8 and the capacitor C9 set a soft start time (SS). At this time, when the voltage (Opto, A) of the opto-coupler (OPT) is applied to the anode point (A point) of the light-emitting device (Opto-LED) of the opto-coupler (OPT) at least 3.1V, the light-emitting device (Opto_LED) of the opto-coupler (OPT) is turned on and receives the light. The device Opto-TR is turned on with the base current, and the generation of the base current is determined by R3, thereby determining the high frequency at the base current.

At this time, the cathode-emitter (CE) voltage of the light receiving element (Opto-TR) of the optocoupler (OPT) is determined by the current of the light emitting element (Opto-LED), the cathode-emi of the light receiving element (Opto-TR) The inter-terminal (CE) voltage variation causes the combined resistance state of the resistors R1 and R3 to vary. As a result, the capacity of the variable frequency capacitor C3 is varied, thereby varying the frequency. As the turn-on amount of the photo coupler increases, the capacity of the frequency variable capacitor C3 increases, and in proportion thereto, the frequency decreases, and the output of the rectifier 130 increases.

Fig. 6 is a waveform diagram of the output voltage variation characteristic according to the present invention. As shown in FIG. 6, the output of the rectifier 130 rapidly rises by about 3.5V at t1 at the same time as power-on. The voltage thus increased is charged to the capacitor C9 by the resistor R8 of the soft start setting unit 141, and is applied to the anode (point A) of the light emitting element (Opto-LED) of the optocoupler OPT through the resistor R9. If this 3.1V or more is formed, a current will flow through the light emitting element (Opto-LED).

From this point, the frequency of the cathode-emitter (CE) resistance of the light-receiving element (Opto-TR), that is, the parallel resistance value of the resistor R3 and the cathode-emitter (CE) of the light-receiving element (Opto-TR) begins to decrease, thereby changing the frequency. The capacitance of the capacitor C3 increases, and the frequency of the CMOS timer (CMOS Timer IC) that is the controller 100 changes to low, and the output voltage to the rectifier 130 increases.

The increase in the output voltage of the rectifier 130 is determined by the time constant of the soft start setting unit 141. The slope of the soft start time (SS Time) section is determined as shown in FIG. .

Soft-start is made by determining the time constant of the time constant resistor R8 and the capacitor C9, and when the output voltage rises to a set value (eg, 12V), it is controlled by the level detector 142. . The level detector 142 applies the output of the rectifier 130 to an equal voltage of the distribution resistors R10 and R11 to the control terminal of the level detection element IC2 (TL431), so that the output voltage of the rectifier 130 reaches a set value. In this case, the control terminal voltage of the level detection device IC2 becomes a turn-on voltage of 2.5V.

Accordingly, since the R (reference) of the level detecting device IC2 is 2.5V, when more than this voltage is applied, the level detecting device IC2 is operated so that the voltage of the cathode K of the level detecting device IC2 is also 2.5V. At the same time, the P & P transistor Q3 is also turned on. At the same time, the voltage of the light emitting element (Opto_LED) anode (point A) of the optocoupler (OPT) is converted to a voltage of [2.5V + 0.6V (voltage between B and E of Q3) = 3.1V] 3.1V.

As such, the initial soft start (SS) function is performed by using the state of the secondary voltage rise, and the voltage control (Volt-Control) is performed and the set basic voltage can be maintained.

1 is a circuit diagram of an LC half-bridge power converter according to the prior art.

2 is a schematic diagram of a CMOS MOS Timer IC with a typical duty 50% cycle.

Figure 3 is an LCD half-bridge power converter circuit for the LED according to the present invention.

4 is a CMOS timer timer IC diagram according to the present invention.

5 (A), (B), (C) is a schematic view of frequency variation of a CMOS timer that is a controller according to the present invention.

6 is an output characteristic waveform diagram for explaining soft start according to the present invention;

<Description of the symbols for the main parts of the drawings>

100: controller 110: output unit

120: LLC resonator 130: rectifier

140: feedback unit 141: soft start setting unit

142: level detector 143: controller frequency variable

144: protection circuit OPT: optocoupler

Opto-TR: Optocoupler's light receiving element Opto_LED: Optocoupler's light emitting element

Claims (3)

Based on the frequency control of the controller 100, an external input power source DC is generated as a pulse output at the output unit 110, the pulse output of the output unit 110 is resonated through the LLC resonator 120, and the LLC resonance is performed. The rectifier 130 is rectified through the rectifier 130 at the secondary side of the unit 120 to output DC power to the load side, and the output of the rectifier 130 is detected through the feedback unit 140 to be fed back to the controller 100. In the EL half-bridge power converter for the LED is configured, The controller 100 controls the output unit 110 by generating a control pulse having a use frequency range of 50 kHz to 1 MHz and a duty of 50%, based on a soft start set value set in the feedback unit 140. It is a CMOS timer (C MOS Timer IC) configured to control the final output level of the rectifier 130 by changing the output frequency in response to the change in the capacitance of the capacitor (C3) for variable frequency, The feedback unit 140 detects the output of the rectifier 130 and operates the optocoupler based on the soft start set value. When the output of the rectifier 130 is equal to or higher than the rated set voltage, the opto coupler is turned off. And the capacitance of the variable frequency capacitor C3 of the controller 100 by the optocoupler, The feedback unit 140, A soft start setting unit 141 for generating a soft start voltage through the resistor R9 by setting a time constant of the output of the rectifying unit 130 by the resistor R8 and the condenser C9; The output of the rectifier 130 is distributed through the distribution resistors R10 and R11, and the level detecting element IC2 detects whether the divided voltage level is equal to or higher than the set level, and then through the PNP transistor Q3. A level detector 142 which bypasses the output of the soft start setting unit 141 when the level is higher than the set level; An optocoupler (OPT) for a feedback signal that receives the output of the soft start setting unit 141 controlled by the level detector 142 to the anode side to control the light emitting device and to generate a feedback signal by the ANP-type light receiving device Wow, The external DC power is distributed through the distribution resistors R1 and R3 to apply the bias potential of the other end of the frequency variable capacitor C3 of the controller 100 and by the light receiving element of the feedback signal optocoupler OPT. An LCD half-bridge power converter for an LED comprising a controller frequency variable part (143) for controlling the bias of the other end of the frequency variable capacitor (C3). delete The method of claim 1, wherein the output pulse of the output unit 110 is received through the reverse diode (D3) (D2) to the reverse diode (D1) based on the set value of the capacitor (C7) and resistors (R6, R7). EL half-bridge power converter for the LED further comprises a protection circuit for controlling the base of the light receiving element of the opto-coupler (OPT) by.

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