JP5394975B2 - Switching transistor control circuit and power converter using the same - Google Patents

Description

  The present invention relates to a control circuit for driving a switching transistor.

  Power converters are used in motor drivers, switching power supplies, lighting inverters, and other various industrial equipment. A power converter (inverter) is a half-bridge circuit including a high-side transistor and a low-side transistor connected in series, a circuit in which the low-side transistor is replaced with a rectifier diode, an H-bridge circuit, and the like (hereinafter collectively referred to as a switching output circuit). And a gate control circuit for driving the transistor.

JP 2006-315154 A

FIG. 1 is a circuit diagram showing a three-phase power converter 300 according to a comparative technique studied by the present inventors. The power conversion device 300 includes U-phase, V-phase, and W-phase switching output circuits 10 _U , 10 _V , and 10 _W, and control circuits 12 _U , 12 _V , and 12 _W that control the respective circuits. Since each phase is configured in the same manner, the configuration will be described by focusing on the U phase. Also, subscripts indicating phases are omitted as appropriate. It should be noted that the configuration of FIG. 1 should not be recognized as a known technique known to those skilled in the art.

  The switching output circuit 10 includes a high side transistor M1 and a low side transistor M2 provided in series between the power supply terminal PVDD and the ground terminal PGND. A diode is provided in parallel with each of the high-side transistor M1 and the low-side transistor M2 so that the cathode is on the power supply terminal PVDD side.

  The control circuit 12 alternately turns on and off the high-side transistor M1 and the low-side transistor M2 in response to control signals G1 and G2 from the control device 8. When the high-side transistor M1 is turned on and the low-side transistor M2 is turned off, the power supply voltage Vdd is output as the output U. Conversely, when the high-side transistor M1 is turned off and the low-side transistor M2 is turned on, the ground voltage VGND (0 V) is output as the output U.

The control circuit 12 includes a high side drive circuit 14 that drives the high side transistor M1 and a low side drive circuit 16 that drives the low side transistor M2.
The positive control power supply E1 generates a positive power supply voltage V1. The negative control power supply E2 generates a negative power supply voltage V2 (V2 <0).

The resistor R1, the diode D1, and the capacitor C1 constitute a so-called bootstrap circuit. Bootstrap circuit charges the capacitor C1 through the diode D1 for rectification, and generates a potential difference [Delta] V ₁ across it. The high potential side terminal of the capacitor C1, [Delta] V ₁ voltage V3 higher than the source voltage of the high side transistor M1 is generated.

Capacitor C2, resistor R2, and zener diode Z1 form a negative power supply circuit. Specifically by the capacitor C2 is charged, the potential difference [Delta] V ₂ is generated in the capacitor C2. This potential difference ΔV ₂ is kept at the Zener voltage Vz (for example, 5 V) of the Zener diode Z1. As a result, the terminal on the low potential side of the capacitor C2, [Delta] V ₂ voltage V4 lower than the source voltage of the high side transistor M1 is generated.

The high-side drive circuit 14 includes a positive power supply terminal P1 and a negative power supply terminal P2, and receives power supply voltages V3 and V4, respectively. When the control signal G1 takes the first level (for example, high level), the high side drive circuit 14 outputs the drive voltage V _G1 whose voltage level is the power supply voltage V3 to the gate of the high side transistor M1, and the high side drive circuit 14 The transistor M1 is turned on. The high side drive circuit 14 outputs a drive voltage V _G1 having a voltage level of the power supply voltage V4 to the gate of the high side transistor M1 when the control signal G1 takes the second level (for example, low level). The high side transistor M1 is turned off.

The low side drive circuit 16 includes a positive power supply terminal P3 and a negative power supply terminal P4, and receives power supply voltages V1 and V2, respectively. When the control signal G2 takes the first level (for example, high level), the low-side drive circuit 16 outputs the drive voltage V _G2 whose voltage level is the power supply voltage V1 to the gate of the low-side transistor M2, and the low-side transistor M2 Turn on. When the control signal G2 takes the second level (for example, low level), the low side drive circuit 16 outputs the drive voltage V _G2 whose voltage level is the power supply voltage V2 to the gate of the low side transistor M2, and the low side transistor M2 Turn off.

According to the configuration of FIG. 1, the negative power supply circuit is configured by the capacitor C2, the resistor R2, and the Zener diode Z1, so that the gate voltage V _G1 when the high-side transistor M1 is turned off is lower than the source voltage. . As a result, even if noise is mixed in the gate line or the source line, the gate-source voltage of the high side transistor M1 does not exceed the threshold voltage Vth of the MOSFET, so that malfunction due to noise can be prevented.

However, in the configuration of FIG. 1, even after a sufficient potential difference ΔV ₂ is generated in the capacitor C2, current flows through a path including the Zener diode Z1 and the resistor R2, so that useless power is consumed.

  SUMMARY An advantage of some aspects of the invention is to provide a control circuit capable of preventing malfunction of a high-side transistor while suppressing power consumption.

  One embodiment of the present invention relates to a control circuit for a high-side transistor. This control circuit is capable of switching between an operating state and a stopped state, generates a low level driving voltage lower than the low potential side terminal of the high side transistor in the operating state, and a negative voltage circuit in which current consumption decreases in the stopped state When a control signal for controlling on / off of the high side transistor is received and the control signal instructs the off of the high side transistor, a high voltage is applied to the control terminal of the high side transistor according to the low level driving voltage. A side drive circuit, and a control device that switches between an operating state and a stopped state of the negative voltage circuit.

  According to this aspect, wasteful power consumption can be reduced by switching the operation state and the stop state of the negative voltage circuit as necessary.

The control device may stop the negative voltage circuit when the potential difference between the potential of the low potential side terminal of the high side transistor and the low level driving voltage is larger than a predetermined threshold voltage.
When a low-level drive voltage that can reliably turn off the high-side transistor is generated, the further operation of the negative voltage circuit is wasted, and wasteful power can be reduced by stopping it.

The control device may stop the negative voltage circuit when the current flowing through the high-side transistor is smaller than a predetermined threshold current.
When the current flowing through the high-side transistor is small, that is, in a light load state, it is difficult for noise to occur, or even if it occurs, the amplitude is small, so even if the negative voltage circuit is stopped, the high-side transistor is mistakenly It is difficult to turn on. Therefore, also in this case, power consumption can be reduced.

The control device may stop the negative voltage circuit when the switching frequency of the high-side transistor is lower than a predetermined threshold value.
When the switching frequency is low, it is estimated that the load is light, and in this case as well, power consumption can be reduced by stopping the negative voltage circuit.

The control device may control the operation state and the stop state of the negative voltage circuit based on at least a signal synchronized with the control signal.
Control can be simplified by synchronizing with the control signal.

The negative voltage circuit may include a capacitor and a switch provided in series between the low potential side terminal of the high side transistor and the negative fixed voltage terminal, and may output a voltage generated at the low potential side terminal of the capacitor. The switch may be turned on in the operating state and turned off in the stopped state.
By turning off the switch, the charging path for the capacitor is cut off, so that power consumption can be reduced.

The control device may turn off the switch when the voltage across the capacitor is greater than a predetermined threshold voltage.
When a sufficient potential difference is generated in the capacitor, useless power consumption can be reduced by turning off the switch to cut off the current path.

  The negative voltage circuit may further include a Zener diode provided in parallel with the capacitor in such a direction that the cathode is on the high potential side terminal side of the capacitor. In this case, the voltage across the capacitor can be stabilized to a Zener voltage.

  Another aspect of the present invention is a power converter. This power conversion device includes a high-side transistor and a control circuit according to any one of the above-described aspects that drives the high-side transistor.

  Note that any combination of the above-described constituent elements and the constituent elements and expressions of the present invention replaced with each other among methods, apparatuses, systems, and the like are also effective as an aspect of the present invention.

  According to an aspect of the present invention, it is possible to prevent malfunction of the high-side transistor while suppressing power consumption.

It is a circuit diagram which shows the three-phase power converter device which concerns on the comparison technique which this inventor examined. It is a circuit diagram which shows the structure of the power converter device which concerns on embodiment. It is a circuit diagram which shows the structure of the power converter device which concerns on a 1st modification. It is a circuit diagram which shows the structure of the power converter device which concerns on a 2nd modification.

  The present invention will be described below based on preferred embodiments with reference to the drawings. The same or equivalent components, members, and processes shown in the drawings are denoted by the same reference numerals, and repeated descriptions are omitted as appropriate. The embodiments do not limit the invention but are exemplifications, and all features and combinations thereof described in the embodiments are not necessarily essential to the invention.

In this specification, “the state in which the member A is connected to the member B” means that the member A and the member B are electrically connected in addition to the case where the member A and the member B are physically directly connected. It includes the case of being indirectly connected through another member that does not affect the connection state.
Similarly, “the state in which the member C is provided between the member A and the member B” refers to the case where the member A and the member C or the member B and the member C are directly connected, as well as an electrical condition. It includes the case of being indirectly connected through another member that does not affect the connection state.

FIG. 2 is a circuit diagram showing a configuration of the power conversion device 100 according to the embodiment. The power conversion device 100 is a three-phase inverter, and U-phase, V-phase, and W-phase switching output circuits 10 _U , 10 _V , and 10 _W, and control circuits 12 _U , 12 _V , and 12 _W that control the switching circuits A control device 8 that generates control signals G1, G2, and G3 for the output circuits 10 _U , 10 _V , and 10 _W is provided. Members that are the same as or equivalent to those of the power conversion device 300 of FIG.

  An inductive load such as an electric motor, a transformer, and an inductor is assumed as a load (not shown) of the power conversion device 100, but is not particularly limited in the present invention. The control device 8 switches the drive phases U, V, W according to the state of the load, and controls the control signals G1, G2 so that the high-side transistor M1 and the low-side transistor M2 of the drive target phase are alternately turned on and off. Is generated. The control sequence of each power transistor (for example, 120-degree energization, 180-degree energization, etc.) may be performed using a known technique, and thus description thereof is omitted here.

  The negative voltage circuit 20 can be switched between an operating state and a stopped state, and generates a low level driving voltage V4 lower than a low potential side terminal (source, emitter) of the high side transistor M1 in the operating state. Since the low-side transistor M2 is on during the period in which the high-side transistor M1 is to be turned off, the voltage (source potential) at the low-potential side terminal of the high-side transistor M1 is substantially the ground voltage VGND. Therefore, the low level drive voltage V4 in the operating state is a negative potential.

  Further, the negative voltage circuit 20 is configured such that the circuit operation is stopped in the stopped state, and the current consumption is substantially zero in the stopped state, or is smaller than that in the operating state. When the stop state continues, the low level drive voltage V4 becomes the same level as the low potential side terminal (source) of the high side transistor M1, specifically, the ground voltage VGND.

  Specifically, the negative voltage circuit 20 includes a capacitor C2, a resistor R2, a Zener diode Z1, and a switch M3. The capacitor C2, the resistor R2, and the switch M3 are provided in series between the low potential side terminal (source) of the high side transistor M1 and the terminal to which the negative fixed voltage V2 is applied. The zener diode Z1 is provided in parallel with the capacitor C2 in such a direction that the cathode is on the high potential side terminal side of the capacitor C2.

  The switch M3 is a transistor of the same type as the low-side transistor M2, and is controlled by a switch drive circuit 18 configured similarly to the low-side drive circuit 16. When the switch M3 is turned on, the negative voltage circuit 20 is in an operating state, and when the switch M3 is turned off, the negative voltage circuit 20 is in a stopped state.

When the switch M3 is turned on, the negative voltage circuit 20 is substantially equivalent to the configuration of FIG. Accordingly, the voltage ΔV ₂ across the capacitor C2 becomes equal to the Zener voltage Vz, and a voltage lower by ΔV ₂ than the source of the high side transistor M1 is generated at the low potential side terminal of the capacitor C2. The negative voltage circuit 20 outputs the voltage at the low potential side terminal of the capacitor C2 as the low level drive voltage V4.

  When the switch M3 is turned off, the charging path for the capacitor C2 is cut off. As a result, the current consumption of the negative voltage circuit 20 is reduced.

  The configuration of the negative voltage circuit 20 is not limited to that shown in FIG. 2, and those skilled in the art can understand that the order of the capacitor C2, the resistor R2, and the switch M3 can be appropriately changed. Or it is good also as a completely different structure which can implement | achieve an equivalent function.

  The high side drive circuit 14 receives the high level drive voltage V3 generated by the bootstrap circuit (R1, D1, C1) at the positive power supply terminal P1, and the low voltage generated by the negative voltage circuit 20 at the negative power supply terminal P2. Receives level drive voltage V4.

The high-side drive circuit 14 receives a control signal G1 for controlling on / off of the high-side transistor M1, and when the control signal G1 instructs to turn off the high-side transistor M1, the high-side transistor M1 has a control terminal (gate). When the driving voltage V _G1 corresponding to the low level driving voltage V4 is applied and the turning off is instructed, the driving voltage V _G1 corresponding to the high level driving voltage V3 is applied to the gate of the high side transistor M1.

The control device 8 controls the operation state and the stop state of the negative voltage circuit 20 in addition to the control of the switching output circuits 10 _U to 10 _W. Specifically, the control signal G3 for switching the operation state and the stop state of the negative voltage circuit 20 is generated. When the control signal G3 is asserted (for example, high level), the negative voltage circuit 20 is in an operating state, and when the control signal G3 is negated (for example, low level), the negative voltage circuit 20 is in a stopped state.

  Hereinafter, specific control of the negative voltage circuit 20 by the control device 8 will be described.

  Control 1. First, the basic operation will be described. The control device 8 asserts the control signal G3 to activate the negative voltage circuit 20 during the period when the high side transistor M1 is to be turned off, and negates the control signal G3 during the period when the high side transistor M1 is to be turned on. Thus, the negative voltage circuit 20 is stopped.

  The generation of the negative voltage by the negative voltage circuit 20 is necessary during the off period of the high side transistor M1 and is not necessary during the on period of the high side transistor M1, and thus the negative voltage is generated during the period when no operation is required. By stopping the circuit 20, the power consumption can be reduced as compared with the power conversion device 300 of FIG.

  Further, in this case, since the control signal G3 can use a signal synchronized with the control signal G1, there is an advantage that the configuration and operation of the control device 8 can be simplified.

In addition to the control of the negative voltage circuit 20 synchronized with the control signal G1 , the control device 8 performs the following control for further power consumption reduction. Specifically, even in a period during which the negative voltage circuit 20 should be in an operating state, it is set in a stopped state.

  Control 2. The low level drive voltage V4 to be generated by the negative voltage circuit 20 is sufficient if it is low enough that the high side transistor M1 does not malfunction, and it is not required to be lower than that. Therefore, the control device 8 stops the negative voltage circuit 20 when the potential difference between the low-potential side terminal (source) of the high-side transistor M1 and the low-level drive voltage V4 is larger than a predetermined threshold voltage.

In order to perform this control, a comparison unit 22 is provided. Comparing comparator 22, the potential difference between the potential and the low level driving voltage V4 on the low potential side terminal of the high side transistor M1 (the source), i.e., the voltage [Delta] V ₂ across the capacitor C2 with a predetermined threshold voltage Vth Then, the detection signal S1 indicating the comparison result is generated. The control device 8 stops the negative voltage circuit 20 when the detection signal S1 indicates ΔV ₂ > Vth.

Note that in the case of performing control based on the voltage ΔV ₂ across the capacitor C2, ΔV ₂ is stably maintained near the threshold voltage Vth. Therefore, the Zener diode Z1 may be omitted. The resistor R2 can be omitted.

  Control 3. In a situation where there is no possibility that the high side transistor M1 malfunctions, it is not necessary to supply a negative voltage to the gate of the high side transistor M1. Therefore, the control device 8 puts the negative voltage circuit 20 in a stopped state in such a situation.

As a situation where the possibility of malfunction of the high-side transistor M1 is small, a case where the amplitude of noise accompanying switching of the high-side transistor M1 and the low-side transistor M2 is small can be considered. Since the amplitude of the noise depends on the current flowing through the high-side transistor M1 and the low-side transistor M2, the control device 8 determines that when the currents I _M1 and I _M2 flowing through the high-side transistor M1 or the low-side transistor _M2 are small, The control device 8 may be stopped. Specifically, the control device 8 controls the negative voltage circuit 20 based on the detection signal S2 corresponding to the current I _M1 or I _M2 . As a means for detecting the current, on the assumption that the on-resistance of the high-side transistor M1 and the low-side transistor M2 is known, a method for detecting the voltage drop, a resistor for detection in the current path, and the voltage drop There is no particular limitation as long as a method of detecting the current, a method of generating a replica current by a current mirror circuit, etc., and converting it into a voltage are used.

  According to this control, power consumption can be further reduced.

Control 4. When the switching frequency of the switching output circuit 10 is lower than a predetermined threshold value, the control device 8 may stop the negative voltage circuit 20.
Even in a situation where the switching frequency is low, the high-side transistor M1 is unlikely to malfunction. Therefore, power consumption can be reduced by stopping the negative voltage circuit 20.

  Control 5. When a signal indicating a light load state is given to the control device 8 from the outside, the negative voltage circuit 20 may be controlled based on the signal.

  The present invention has been described based on the embodiments. This embodiment is an exemplification, and it will be understood by those skilled in the art that various modifications can be made to combinations of the respective constituent elements and processing processes, and such modifications are within the scope of the present invention. is there. Hereinafter, such modifications will be described.

  FIG. 3 is a circuit diagram showing a configuration of a power conversion device 100a according to the first modification. The difference between the power conversion device 100a of FIG. 4 and the power conversion device 100 of FIG. 2 is that the negative control power supply E2 is replaced with a second negative voltage circuit 24. The negative voltage circuit 24 is a bootstrap circuit, and includes a capacitor C3 and a Zener diode Z2 provided in parallel between the ground terminal PGND and the negative power supply line PVSS. The negative voltage circuit 24 generates a negative voltage V2 that is lower than the ground voltage VGND by a Zener voltage Vz.

  Also in this modified example, the malfunction of the high side transistor M1 can be prevented and the power consumption can be suppressed similarly to the power conversion device 100 of FIG.

FIG. 4 is a circuit diagram illustrating a configuration of a power conversion device 100b according to a second modification. In the power conversion device 100b of FIG. 4, the negative voltage circuit 24b includes a diode D2 instead of the Zener diode Z2. Furthermore power conversion apparatus 100b, the voltage [Delta] V ₃ across the capacitor C3, a comparator 26 for comparing a predetermined threshold voltage Vth2. The comparison unit 26 generates a detection signal S3 indicating the comparison result. The control device 8 can perform voltage control such that ΔV ₂ = ΔV ₃ by turning on the switch M3 when the detection signal S3 indicates ΔV ₃ > Vth2 and the low-side transistor M2 is on. , Overcharge and undervoltage can be prevented, and wasteful power can be reduced.

  In the embodiments, a three-phase inverter has been described as an example, but the configuration of the inverter can take various topologies depending on the load to be driven and its application. For example, in the case of a single-phase inverter, it can be applied to an inverter for driving a DC / DC converter, a fluorescent lamp, or the like, or a single-phase motor. In the case of a bidirectional inverter or an H-bridge circuit, it can be used for driving a single phase motor, an inverter for driving a fluorescent lamp, or the like. Furthermore, a topology in which the low-side transistor of the switching output circuit 10 is replaced with a rectifying diode is also effective.

  Although the present invention has been described using specific terms based on the embodiments, the embodiments only illustrate the principles and applications of the present invention, and the embodiments are defined in the claims. Many variations and modifications of the arrangement are permitted without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Power converter, 8 ... Control apparatus, 10 ... Switching output circuit, 12 ... Control circuit, 14 ... High side drive circuit, 16 ... Low side drive circuit, 18 ... Switch drive circuit, 20 ... Negative voltage circuit, M1 ... High Side transistor, M2 ... Low side transistor, M3 ... Switch, C2 ... Capacitor, R2 ... Resistance, Z1 ... Zener diode, V4 ... Low level drive voltage, 22 ... Comparator, 24 ... Negative voltage circuit, 26 ... Comparator.

Claims (8)

A high-side transistor control circuit,
Including a switch provided between a low-potential side terminal and a negative fixed voltage terminal of the high-side transistor, wherein an operation state in which the switch is turned on and a stop state in which the switch is turned off can be switched. A negative voltage circuit configured to generate a low-level driving voltage lower than a low-potential side terminal of the high-side transistor and to reduce current consumption in a stopped state;
When a control signal for controlling on / off of the high-side transistor is received and the control signal instructs the high-side transistor to be turned off, a driving voltage corresponding to the low-level driving voltage is applied to the control terminal of the high-side transistor. A high side drive circuit for applying
In addition to the on / off state of the high-side transistor, the state of the high-side transistor or the control circuit can be detected, and the operation of the negative voltage circuit is controlled by controlling the switch based on the detected state. A control device for switching between the state and the stop state;
A control circuit comprising: The control device detects a potential difference between the potential of the low potential side terminal of the high side transistor and the low level driving voltage, and the potential difference between the potential of the low potential side terminal of the high side transistor and the low level driving voltage is 2. The control circuit according to claim 1, wherein the negative voltage circuit is set to the stop state when the voltage is larger than a predetermined threshold voltage. 3. The control device detects a current flowing through the high-side transistor, and stops the negative voltage circuit when the current flowing through the high-side transistor is smaller than a predetermined threshold current. The control circuit according to 1 or 2. The control device detects a switching frequency of the high-side transistor, and stops the negative voltage circuit when the switching frequency of the high-side transistor is lower than a predetermined threshold value. 4. The control circuit according to any one of items 1 to 3. The negative voltage circuit, between the low potential side terminal and the negative fixed voltage terminal of the high side transistor, includes a Capacity data provided in the switch in series, output voltage generated to the low potential side terminal of the capacitor control circuit according to any one of the force to Rukoto claim 1, wherein 4. The control circuit according to claim 5 , wherein the control device turns off the switch when a voltage across the capacitor is larger than a predetermined threshold voltage. 7. The control circuit according to claim 5 , wherein the negative voltage circuit further includes a Zener diode provided in parallel with the capacitor in such a direction that a cathode thereof is on a high potential side terminal side of the capacitor. . A high-side transistor,
The control circuit according to any one of claims 1 to 7 , which drives the high-side transistor;
A power conversion device comprising:

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