JP2015228772A - Gate drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a heat evolution of a gate drive circuit.SOLUTION: A gate drive circuit is provided for applying a constant voltage to a transistor gate by stepping down a power supply voltage, the circuit includes: a temperature detection circuit for detecting the temperature of the gate drive circuit; a comparator for comparing the voltage of the gate to the reference voltage; and a series regulator for generating a higher constant voltage than the reference voltage if the temperature of the gate drive circuit is higher than a prescribed temperature and if the voltage of the gate is lower than the reference voltage.

Description

  The present invention relates to a gate driving circuit.

  Conventionally, switching power supply voltage is reduced by using a series regulator, and the stabilized constant voltage is applied to the switching element gate to drive the switching element to reduce the cost of the power supply and increase the accuracy of the device. An apparatus is known (see, for example, Patent Document 1).

JP 2012-34450 A

  However, if the difference between the power supply voltage and the output voltage of the series regulator is large, there is a problem that heat generation of the gate drive circuit increases while the gate is driven.

  Therefore, an object is to suppress the heat generation of the gate drive circuit.

In order to achieve the above object, according to one aspect,
A gate drive circuit that steps down the power supply voltage and applies a constant voltage to the gate of the transistor,
A temperature detection circuit for detecting the temperature of the gate drive circuit;
A comparator for comparing the voltage of the gate with a reference voltage;
A series regulator that generates a constant voltage higher than the reference voltage when the temperature of the gate driving circuit is higher than a predetermined temperature and the voltage of the gate is lower than the reference voltage;
A gate drive circuit is provided.

  According to one aspect, heat generation of the gate drive circuit can be suppressed.

FIG. 4 is a diagram illustrating a gate drive circuit according to the first embodiment. FIG. 6 is a diagram illustrating an operation of the gate drive circuit according to the first embodiment. FIG. 6 is a diagram illustrating an operation of the gate drive circuit according to the first embodiment. FIG. 4 is a diagram illustrating a gate drive circuit according to the first embodiment. FIG. 4 is a diagram illustrating a gate drive circuit according to the first embodiment. FIG. 4 is a diagram illustrating a gate drive circuit according to the first embodiment. 6 is a diagram illustrating a gate drive circuit according to a second embodiment. FIG. FIG. 10 is a diagram illustrating an operation of the gate drive circuit according to the second embodiment. FIG. 10 is a diagram illustrating an operation of the gate drive circuit according to the second embodiment. FIG. 10 is a diagram illustrating a gate drive circuit according to a third embodiment.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and redundant description may be omitted.

<First Embodiment>
<Configuration of gate drive circuit>
FIG. 1 shows an example of a schematic configuration of a gate drive circuit 100 according to the present embodiment. The gate drive circuit 100 is mounted on a vehicle such as an automobile, for example. Specific examples of such a vehicle include a hybrid vehicle, a plug-in hybrid vehicle, and an electric vehicle.

  The gate drive circuit 100 includes a temperature detection circuit 101, a comparator (for example, a comparator) 102, a series regulator 103, an AND circuit 104, and a switching element 105.

  The power supply voltage is represented as a power supply voltage VCC, the reference voltage is represented as a reference voltage Vref, the output voltage of the gate drive circuit 100 is represented as a voltage VMP, the gate voltage of the switching element 106 is represented as a gate voltage Vge, and the output voltage of the series regulator 103 is represented as a voltage Vref ′.

  The gate drive circuit 100 steps down the power supply voltage VCC using the series regulator 103 and applies a stabilized constant voltage to the gate of the switching element (transistor) 106 shown in FIG. The driving of the switching element 106 is controlled by the constant voltage. The switching element 106 is connected in antiparallel with the diode 107 and directly connected with the gate resistor 108.

  The temperature detection circuit 101 detects the temperature of the gate drive circuit 100 using, for example, a known temperature sensor (not shown) provided in the temperature detection circuit 101, and outputs a detection signal to the AND circuit 104. For example, when the temperature of the gate drive circuit 100 is higher than a predetermined temperature, the temperature detection circuit 101 outputs a “high level” signal (= H signal) to the AND circuit 104 as a detection signal. For example, when the temperature of the gate drive circuit 100 is equal to or lower than a predetermined temperature, the temperature detection circuit 101 outputs a “low level” signal (= L signal) to the AND circuit 104 as a detection signal.

  The predetermined temperature is not particularly limited because it is a temperature that is appropriately set according to the specification, configuration, and the like of the gate drive circuit. At least a temperature that can detect whether or not the gate drive circuit is in an overheated state may be set.

  The comparator 102 compares the gate voltage Vge input to the inverting input terminal (− terminal) with the reference voltage Vref input to the non-inverting input terminal (+ terminal), and outputs the comparison signal to the AND circuit 104. ,Output. For example, when the gate voltage Vge is lower than the reference voltage Vref, the comparator 102 outputs an H signal to the AND circuit 104 as a comparison signal. For example, when the gate voltage Vge is equal to or higher than the reference voltage Vref, the comparator 102 outputs the L signal to the AND circuit 104 as a comparison signal.

  The series regulator 103 generates an output voltage (= voltage Vref ′) based on the output signal output from the AND circuit 104. The voltage Vref ′ is input to the non-inverting input terminal (+ terminal) of the amplifier (AMP) provided in the series regulator 103, and the voltage VMP is input to the inverting input terminal (−terminal).

  For example, when the output signal output from the AND circuit 104 is an H signal, the temperature of the gate driving circuit 100 is higher than a predetermined temperature (the gate driving circuit 100 is in an overheated state), and the gate voltage Vge is It means that it is lower than the reference voltage Vref.

  In this case, the series regulator 103 temporarily increases the output voltage (= voltage VMP) of the gate drive circuit 100 and generates a constant voltage (becomes the output voltage of the series regulator 103) higher than the reference voltage Vref. The gate of the switching element 106 is driven based on the voltage.

  For example, when the output signal output from the AND circuit 104 is an L signal, the temperature of the gate driving circuit 100 is equal to or lower than a predetermined temperature (the gate driving circuit 100 is not in an overheated state), and / or the gate voltage Vge is , It means that the reference voltage Vref or higher.

  In this case, the series regulator 103 maintains the output voltage (= voltage VMP) of the gate drive circuit 100 at the reference voltage Vref (which becomes the output voltage of the series regulator 103). The gate of the switching element 106 is driven based on the voltage.

  That is, the series regulator 103 reduces the difference between the output voltage and the power supply voltage VCC when the gate drive circuit 100 is in an overheated state. As a result, it is possible to suppress an increase in heat generation of the gate drive circuit 100 while driving the gate.

  The AND circuit 104 generates an output signal (logical product) based on the detection signal output from the temperature detection circuit 101 and the comparison signal output from the comparator 102, and outputs the output signal to the series regulator 103. The detection signal is a signal indicating whether or not the temperature of the gate driving circuit 100 is higher than a predetermined temperature, and the comparison signal is a signal indicating whether or not the gate voltage is lower than the reference voltage Vref.

  For example, when the H signal is input from the temperature detection circuit 101 and the H signal is input from the comparator 102, the AND circuit 104 outputs the H signal to the series regulator 103.

  For example, when the H signal is input from the temperature detection circuit 101 and the L signal is input from the comparator 102, the AND circuit 104 outputs the L signal to the series regulator 103.

  For example, when the L signal is input from the temperature detection circuit 101 and the H signal is input from the comparator 102, the AND circuit 104 outputs the L signal to the series regulator 103.

  For example, when the L signal is input from the temperature detection circuit 101 and the L signal is input from the comparator 102, the AND circuit 104 outputs the L signal to the series regulator 103.

  The switching element 105 is on / off controlled based on a drive signal output from a microcomputer or the like. For example, when the drive signal is an H signal and the switching element 105 is turned on, the series regulator 103 and the switching element 106 become conductive, so that the output voltage of the series regulator 103 is applied to the gate of the switching element 106. For example, when the drive signal is an L signal and the switching element 105 is turned off, the series regulator 103 and the switching element 106 are non-conductive, so that the output voltage of the series regulator 103 is not applied to the gate of the switching element 106.

  The switching element is not particularly limited, and for example, an IGBT (Insulated Gate Bipolar Transistor), a MOS (Metal Oxide Semiconductor) transistor, a bipolar transistor, or the like can be used.

<Output Voltage of Gate Drive Circuit 100>
Next, an example of the operation of the output voltage (= voltage VMP) of the gate drive circuit 100 will be described with reference to FIGS.

  FIG. 2 shows the operation of the voltage VMP when the gate drive circuit 100 is not overheated. FIG. 3 shows the operation of the voltage VMP when the gate drive circuit 100 is in an overheated state.

  As shown in FIG. 2, since the output voltage of the gate drive circuit 100 becomes the reference voltage Vref, the reference voltage Vref is applied to the gate of the switching element 106. The reference voltage Vref is lower than the power supply voltage VCC.

  As shown in FIG. 3A, the output voltage of the gate drive circuit 100 temporarily rises to become the power supply voltage VCC, so that the power supply voltage VCC is applied to the gate of the switching element 106. That is, the difference between the power supply voltage VCC and the output voltage of the series regulator 103 is reduced. At this time, excessive voltage stress is not applied to the gate of the switching element 106.

  Note that the output voltage of the gate drive circuit 100 can be changed in accordance with the rate of heat generation. The output voltage of the gate drive circuit 100 is preferably set so as to increase as the rate of heat generation increases in a range satisfying the reference voltage Vref and the power supply voltage VCC. For example, as shown in FIG. 3B, the output voltage of the gate drive circuit 100 is set to an intermediate voltage Vrefα (= (power supply voltage VCC−reference voltage Vref) / 2) between the power supply voltage VCC and the reference voltage Vref. Also good.

  According to the gate drive circuit 100 according to the present embodiment, when the gate drive circuit 100 is in an overheated state, the output voltage of the series regulator is increased, and the difference between the power supply voltage and the output voltage of the series regulator is reduced. That is, heat generation of the gate drive circuit 100 can be suppressed by performing constant voltage control on the gate of the switching element 106 with a voltage higher than the reference voltage only when necessary. Further, even when the gate driving circuit 100 is in an overheated state, the gate driving can be continued and the control continuity of the gate can be improved.

  The configuration of the gate drive circuit 100 is not particularly limited to the configuration shown in FIG. For example, as shown in FIG. 4, a switching element 109 having a small current capacity for on / off control may be newly provided. With this configuration, the current capacity of the amplifier can be reduced, so that the cost of the gate driving circuit can be reduced. Further, as shown in FIG. 5, NMOS transistors may be used as the switching elements 105 and 109.

  For example, as shown in FIG. 6, it may be configured to have a function of notifying the microcomputer by a detection signal whether or not the gate drive circuit is in an overheated state. With this configuration, the system voltage VP can be appropriately controlled on the microcomputer side. For example, when the gate drive circuit is in an overheated state, the surge can be suppressed by lowering the system voltage VP and slowing down the switching operation (by reducing the di / dt (current change rate) of the switching element). .

<Second Embodiment>
In this embodiment, the case where a constant current driving circuit is used as a power supply circuit of a gate driving circuit without using a series regulator will be described.

  FIG. 7 shows an example of a schematic configuration of the gate drive circuit 200 according to the present embodiment.

  The gate drive circuit 200 includes a temperature detection circuit 101, a constant current drive circuit 201, and a switching element 202.

  The power supply voltage is the power supply voltage VCC, the reference voltage is the reference voltage (VCC-Vconst), the output voltage of the gate drive circuit 200 is the voltage VFB, the gate voltage of the switching element 106 is the gate voltage Vge, and the constant current is the current (Vconst / Rref). Represent.

  The constant current drive circuit 201 charges the gate capacitance with a constant current when the gate drive circuit 200 is not overheated, and stops when the gate drive circuit 200 is overheated. The constant current drive circuit 201 outputs a detection signal to the microcomputer via the switching element 202, and the constant current drive circuit 201 receives a drive signal from the microcomputer.

<Output Voltage and Constant Current of Gate Drive Circuit 200>
Next, an example of the operation of the output voltage and the constant current of the gate drive circuit 200 will be described with reference to FIGS.

  FIG. 8 shows the operation of the voltage VFB when the gate drive circuit 200 is not in an overheated state. FIG. 9 shows the operation of the voltage VFB when the gate drive circuit 200 is in an overheated state.

  As shown in FIG. 8A, since the output voltage of the gate drive circuit 200 becomes the reference voltage (VCC-Vconst), the reference voltage (VCC-Vconst) is applied to the gate of the switching element 106. The reference voltage (VCC-Vconst) is lower than the power supply voltage VCC. Further, as shown in FIG. 8B, since the constant current driving circuit 201 performs constant current driving, the current is constant (constant current = (Vconst / Rref)).

  As shown in FIG. 9A, since the output voltage of the gate drive circuit 200 is the voltage Vrefβ, the voltage Vrefβ is applied to the gate of the switching element 106. The voltage Vrefβ is lower than the reference voltage (VCC−Vconst). Further, as shown in FIG. 9B, the constant current drive circuit 201 does not perform constant current drive, and thus the current is not constant (changes).

  Therefore, in the case of FIG. 8A, the difference between the voltage VFB and the gate voltage Vge of the switching element 106 is larger than in the case of FIG. That is, in the case of FIG. 8A, the voltage applied to the constant current driver circuit 201 is larger than that in the case of FIG.

  According to the gate drive circuit 200 according to the present embodiment, when the gate drive circuit 200 is in an overheated state, the constant current drive of the constant current drive circuit 201 is stopped and the voltage applied to the constant current drive circuit 201 is reduced. To do. That is, heat generation of the gate drive circuit 200 can be suppressed by making the output voltage of the gate drive circuit 200 lower than the reference voltage only when necessary. Further, a surge generated in the gate drive circuit 200 can be suppressed by using the detection signal.

<Third Embodiment>
In this embodiment, a case where a temperature monitor circuit and a high-select circuit are added to the gate drive circuit and the temperature of the switching element 106 is detected by a temperature sense element (for example, a thermistor, a temperature sense diode, etc.) will be described. To do.

  FIG. 10 shows an example of a schematic configuration of the gate drive circuit 300 according to this embodiment.

  The gate drive circuit 300 includes a temperature detection circuit 101, a comparator 102, a series regulator 103, an AND circuit 104, a switching element 105, a temperature monitor circuit 301, a temperature monitor circuit 302, and a high select circuit 303.

  The temperature monitor circuit 301 generates a first monitor signal based on the temperature of the gate drive circuit 300 detected by the temperature detection circuit 101 and outputs the first monitor signal to the high select circuit 303.

  The temperature monitor circuit 302 generates a second monitor signal based on the temperature of the switching element 106 detected by the temperature sense element 304 and outputs the second monitor signal to the high select circuit 303.

  The high select circuit 303 compares the first monitor signal and the second monitor signal, selects the signal having the higher temperature, generates a temperature signal, and outputs the temperature signal to the microcomputer. That is, the high select circuit 303 has information on whether or not both the gate drive circuit 300 and the switching element 106 are in an overheated state, and information on whether or not one of the gate drive circuit 300 and the switching element 106 is in an overheated state. Is notified to the microcomputer by a temperature signal.

  For example, when the gate drive circuit 300 and the switching element 106 are not overheated, the high select circuit 303 notifies the microcomputer of a temperature signal that both the gate drive circuit 300 and the switching element 106 are not overheated. The gate drive circuit 300 applies a reference voltage Vref to the gate of the switching element 106 based on a drive signal from the microcomputer.

  For example, when the gate drive circuit 300 is overheated and the switching element 106 is not overheated, the high select circuit 303 notifies the microcomputer of a temperature signal that only the gate drive circuit 300 is overheated. The gate drive circuit 300 applies a voltage higher than the reference voltage Vref to the gate of the switching element 106 based on a drive signal from the microcomputer, and the microcomputer limits the output of the system (load factor limitation). Thereby, it is possible to suppress heat generation and surge in the gate drive circuit 300.

  For example, when the switching element 106 is overheated and the gate drive circuit 300 is not overheated, the high select circuit 303 notifies the microcomputer of a temperature signal that only the switching element 106 is overheated. The microcomputer limits the output of the system. Thereby, the heat generation in the switching element 106 can be suppressed.

  For example, when the gate drive circuit 300 and the switching element 106 are in an overheated state, the high select circuit 303 notifies the microcomputer of a temperature signal that both the gate drive circuit 300 and the switching element 106 are in an overheated state. The gate drive circuit 300 applies a voltage higher than the reference voltage Vref to the gate of the switching element 106 based on a drive signal from the microcomputer, and the microcomputer limits the output of the system. As a result, heat generation suppression and surge suppression in the gate drive circuit 300 and heat generation suppression in the switching element 106 are possible.

  According to the gate drive circuit 300 according to the present embodiment, an overheat state of the gate drive circuit 300 and the switching element 106 is detected, and the output voltage of the series regulator, the output of the system, and the like are controlled according to the overheat state. Accordingly, it is possible to realize both the suppression of heat generation in the gate drive circuit 300 and the suppression of heat generation in the switching element 106 and the suppression of gate stress, and the gate drive circuit 300 having high control continuity and high reliability.

  As mentioned above, although the form for implementing this invention was explained in full detail, this invention is not limited to this specific embodiment, In the range of the summary of this invention described in the claim, various Can be modified or changed.

100, 200, 300 Gate drive circuit 101 Temperature detection circuit 102 Comparator 103 Series regulator 106 Switching element (transistor)

Claims (1)

A gate drive circuit that steps down the power supply voltage and applies a constant voltage to the gate of the transistor,
A temperature detection circuit for detecting the temperature of the gate drive circuit;
A comparator for comparing the voltage of the gate with a reference voltage;
A series regulator that generates a constant voltage higher than the reference voltage when the temperature of the gate driving circuit is higher than a predetermined temperature and the voltage of the gate is lower than the reference voltage;
A gate driving circuit.

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