JP7310819B2 - Drive circuit and power supply circuit - Google Patents

Description

The present invention relates to drive circuits and power supply circuits.

2. Description of the Related Art Power supply devices such as inverter devices and DC-DC converters are equipped with semiconductor switching elements having three terminals including a gate terminal such as field effect transistors such as MOSFETs and thyristors in order to realize high-speed switching operations. In order for the power supply to operate properly, the semiconductor switching element must be reliably turned off when it should be off, and reliably turned on when it should be on.

On the other hand, in a semiconductor switching element that turns off when a voltage equal to or lower than a predetermined threshold is applied to its gate terminal, there is known a circuit that reliably turns off the semiconductor switching element by applying a negative voltage to the gate electrode ( For example, see Patent Document 1).

Japanese publication: JP 2013-90223

In the power supply device described above, even if the semiconductor switching element is connected to a circuit in which the gate voltage is negative as disclosed in Patent Document 1, the semiconductor switching element may not operate normally. For example, when the semiconductor switch is turned off with the gate voltage set to a negative voltage, noise such as a surge is input to the gate terminal, and the gate voltage sometimes rises. Due to the increase in gate voltage, the semiconductor switching element may not be turned off reliably at the timing when it should be turned off.

On the other hand, for example, when the semiconductor switch is in the ON state with the gate voltage set to a positive voltage, noise such as a surge is input to the gate terminal, and the gate voltage may drop. Since the conductivity between the channels of the semiconductor switching element is determined by the gate voltage, a decrease in the gate voltage causes the resistance value between the channels to rise and the semiconductor switching element to generate heat, and the heat generation causes an abnormality in the semiconductor switching element. I had something to do. Moreover, in the conventional circuit, it was difficult to eliminate the drop in the gate voltage due to noise and the like.

SUMMARY OF THE INVENTION It is an object of the present invention to suppress fluctuations in gate voltage due to noise or the like in a semiconductor switching element having a gate terminal for controlling the conduction state.

A drive circuit according to an exemplary embodiment of the present application is a drive circuit for a switching element that controls conduction between two terminals. The drive circuit includes a first terminal, a second terminal, a third terminal, a voltage output device, a voltage holding circuit, a capacitor element, and a third diode. The first terminal is connected to the gate electrode of the switching element. The second terminal is connected to one of the two terminals whose conduction state of the switching element is controlled. The voltage output device outputs voltage between the third terminal and the second terminal.

A voltage holding circuit is connected between the first terminal and the second terminal. Also, the voltage holding circuit has a first diode and a second diode. The cathode side of the first diode faces the first terminal side. The second diode is connected in series with the first diode, and the cathode side faces the second terminal side. The capacitor element has one end connected to the first terminal and the other end connected to the third terminal. The third diode has a cathode side connected to the third terminal, an anode side connected to the first terminal, and is connected in parallel with the capacitor element.

In the drive circuit of an exemplary embodiment of the present application, when noise or the like is input to the gate electrode, an electrical path is secured for suppressing fluctuations in the gate voltage due to the noise. It is possible to suppress the fluctuation of the gate voltage due to As a result, even if noise or the like is input to the gate terminal when the semiconductor switching element is in the ON state or the OFF state, it is possible to suppress the occurrence of a large change in the ON state or OFF state of the semiconductor switching element due to the noise or the like.

FIG. 1 is a diagram showing the configuration of a drive circuit. FIG. 2 is a diagram showing another example of the drive circuit. FIG. 3 is a diagram showing the operation when the switching element is in the ON state. FIG. 4 is a diagram showing the path of current that compensates for the gate-source voltage drop. FIG. 5 is a diagram showing the operation when the switching element is in the off state. FIG. 6 is a diagram showing current paths for suppressing a voltage rise between the gate and the source. FIG. 7 is a diagram showing an application example when the drive circuit is applied to a step-down chopper type power supply circuit. FIG. 8 is a diagram showing an application example when the drive circuit is applied to a boost chopper type power supply circuit. FIG. 9A is a diagram showing an example of applying the drive circuit to an inverter circuit. FIG. 9B is a diagram showing another example of applying the drive circuit to the inverter circuit. FIG. 10 is a diagram showing an application example in which the drive circuit is applied to a bidirectional converter circuit.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The scope of the present invention is not limited to the following embodiments, and can be arbitrarily changed within the scope of the technical idea of the present invention.

(Embodiment 1) [1-1. Switching Element] A drive circuit 1 according to the first embodiment will be described below. First, the switching element SW driven by the drive circuit 1 will be described. The switching element SW is a semiconductor element having three terminals: two terminals capable of switching between an ON state having conductivity and an OFF state having no conductivity, and a control terminal controlling the conductivity between the two terminals. be. Since such a semiconductor element can switch between an ON state and an OFF state at high speed, it is used as a switching element of a power supply circuit, as will be described later.

The switching element SW as a semiconductor element includes, for example, a MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor), an Insulated Gate Bipolar Transistor (IGBT), and the like.

When the switching element SW is a MOSFET, the two terminals for switching between the ON state and the OFF state are the source electrode and the drain electrode. Also, the control terminal for controlling the conductivity between the source and the drain is the gate electrode. The source-drain conductivity is controlled by the voltage applied to the gate electrode.

On the other hand, when the switching element SW is an insulated gate bipolar transistor, the two terminals for switching between the ON state and the OFF state are the collector electrode and the emitter electrode. Also, the control terminal for controlling the conductivity between the collector and the emitter is the gate electrode. The collector-emitter conductivity is controlled by the voltage applied to the gate electrode.

In the present embodiment, the drive circuit will be described by taking as an example a case where an n-channel MOSFET is adopted as the switching element SW. In an n-channel MOSFET, when a positive voltage exceeding a predetermined threshold is applied between a gate electrode and a source electrode (hereinafter referred to as between a gate and a source), the source between two terminals other than the gate electrode is applied. A conductive state is established between the electrode and the drain electrode (hereinafter referred to as source-drain), ie, an ON state. On the other hand, when a voltage lower than a predetermined threshold value is applied between the gate and source, the source and drain become non-conductive, that is, turned off.

In the following description, the voltage between the gate and the source is defined as "positive voltage" when the potential of the gate electrode is higher than the potential of the source electrode. In addition, “applying a positive voltage between A and B” means applying a voltage between A and B in which the potential of A is higher than the potential of B.

[1-2. Configuration of Drive Circuit] Next, a drive circuit 1 that drives the switching element SW, which is an n-channel MOSFET, will be described with reference to FIG. FIG. 1 is a diagram showing the configuration of a drive circuit. The drive circuit 1 includes a connection terminal 3 , a voltage holding circuit 5 , a negative potential generation circuit 7 and a voltage output device 9 .

The connection terminal 3 is a terminal for connecting the driving circuit 1 and the switching element SW to be driven. The connection terminal 3 has a first terminal T1 and a second terminal T2. The first terminal T1 is connected to the gate electrode G of the switching element SW. On the other hand, the second terminal T2 is connected to the source electrode S of the switching element SW.

The voltage holding circuit 5 is a circuit connected between the first terminal T1 and the second terminal T2. The voltage holding circuit 5 is a circuit that holds the voltage applied between the first terminal T1 and the second terminal T2, that is, between the gate and the source, at a predetermined constant value. Specifically, the voltage holding circuit 5 has a first diode D1 and a second diode D2. In the voltage holding circuit 5, the first diode D1 and the second diode D2 are connected in series.

Specifically, the first diode D1 has an anode side connected to the second terminal T2 and a cathode side connected to the cathode side of the second diode D2. As a result, the cathode side of the first diode D1 faces the first terminal T1 side. The first diode D1 is, for example, a Zener diode.

The first voltage _VZ1 that causes the first diode D1 to conduct from the cathode side to the anode side is higher than the voltage applied to the gate-source voltage required to conduct the source-drain of the switching element SW. Specifically, the first voltage _VZ1 is preferably set to a voltage corresponding to a voltage between the gate and the source within a range in which the conductive state between the source and the drain does not change due to a change in the voltage between the gate and the source. In other words, the first diode D1 preferably has a breakdown voltage sufficiently higher than the threshold voltage between the gate and the source that turns on the source and the drain. As a result, when a positive voltage is applied between the first terminal T1 and the second terminal T2, conduction can be ensured between the source and the drain of the switching element SW.

The second diode D2 has an anode side connected to the first terminal T1 and a cathode side connected to the cathode side of the first diode D1. As a result, the cathode side of the second diode D2 faces the second terminal T2. The second diode D2 is a general diode such as a pn diode or Schottky diode.

The negative potential generating circuit 7 has one end connected to the first terminal T1 and the other end connected to the third terminal T3. The negative potential generating circuit 7 generates a negative voltage between the first terminal T1 and the second terminal T2 when the voltage output device 9 outputs a zero voltage between the third terminal T3 and the second terminal T2. That is, it is a circuit in which the first terminal T1 is set to a negative potential. The negative potential generation circuit 7 has a capacitor element C and a third diode D3. In the negative potential generating circuit 7, the capacitor element C and the third diode D3 are connected in parallel.

Specifically, the capacitor element C has one end connected to the first terminal T1 and the anode side of the third diode D3, and the other end connected to the third terminal T3 and the cathode side of the third diode D3. Capacitor element C is a general capacitor such as a ceramic capacitor, a film capacitor, a Mylar capacitor, an electrolytic capacitor, or the like.

Also, the capacitance of the capacitor element C is preferably ten times or more the capacitance of the capacitance component formed between the gate electrode G and the channel of the switching element SW. As a result, for example, when the drive voltage is set to 0 V to turn off the switching element SW, by increasing the capacitance of the capacitor element C as described above, an electrode ( Even if a current flows from the drain electrode D) to the gate electrode G and the current is stored in the capacitor element C, the increase in the potential of the gate electrode G can be suppressed. In other words, even if noise is input to the gate electrode G, it is possible to avoid turning off the switching element SW due to the noise.

The third diode D3 has an anode side connected to the first terminal T1 and one end of the capacitor element C, and a cathode side connected to the third terminal T3 and the other end of the capacitor element C. The first diode D1 is, for example, a Zener diode.

The voltage output device 9 is connected to the third terminal T3 and the second terminal T2, and outputs a drive voltage between the third terminal T3 and the second terminal T2 to turn on or off the switching element SW. The voltage output device 9 is, for example, a gate driver that generates a drive voltage to be applied to the gate electrode G of the switching element SW. The voltage output device 9 is composed of a control circuit that controls the drive voltage waveform and a voltage output circuit that outputs the drive voltage based on control by the control circuit.

The voltage output device 9 outputs a positive voltage _VOUT between the third terminal T3 and the second terminal T2 when turning on the switching element SW. On the other hand, when the switching element SW is turned off, a voltage of 0 V is output between the third terminal T3 and the second terminal T2. Also, the voltage output device 9 can output a PWM-controlled pulse signal that varies between 0 V and V _OUT .

In the configuration of the voltage output device 9, the control circuit may be implemented by a computer system including a CPU, storage devices (temporary storage devices such as RAM and non-temporary storage devices such as ROM), and various interfaces. Also, control of the drive voltage may be implemented by a program executable by the computer system. The program is stored in the storage device.

In addition, part or all of the functions of the voltage output device 9 are implemented as one-chip hardware by, for example, SoC (System on Chip), FPGA (Field-Programmable gate array), ASIC (Application Specific integrated circuit), or the like. may be implemented.

As shown in FIG. 1, a fourth diode D4 may be connected in parallel between the source and drain of the switching element SW. Specifically, the cathode side of the fourth diode D4 is connected to the drain electrode D, and the anode side is connected to the source electrode S. Also, the fourth diode D4 may be a parasitic diode formed inside the switching element SW, which is a MOSFET.

In the voltage holding circuit 5, the cathode side of the first diode D1 faces the first terminal T1, and the cathode side of the second diode D2 faces the second terminal T2. Therefore, as a modification of the drive circuit 1, as shown in FIG. 2, the connection relationship between the first diode D1 and the second diode D2 may be reversed from that shown in FIG. Specifically, the cathode side of the first diode D1 may be connected to the first terminal T1, and the anode side may be connected to the anode side of the second diode D2. Furthermore, the cathode side of the second diode D2 may be connected to the second terminal T2, and the anode side may be connected to the anode side of the first diode D1. FIG. 2 is a diagram showing another example of the drive circuit.

[1-3. Operation of drive circuit] [1-3-1. Operation when Switching Element is in ON State] Next, the driving operation of the switching element SW by the driving circuit 1 having the configuration shown in FIGS. 1 and 2 will be described. First, with reference to FIG. 3, the operation when the switching element SW is in the ON state will be described. FIG. 3 is a diagram showing the operation when the switching element is in the ON state. As shown in FIG. 3, when the switching element SW is turned on, the voltage output device 9 outputs a positive voltage _VOUT between the third terminal T3 and the second terminal T2.

At this time, current flows in the order of (i) voltage output device 9, (ii) capacitor element C, (iii) second diode D2, and (iv) first diode D1, as indicated by thick arrows in FIG. . At this time, ignoring the forward voltage of the second diode D2, the voltage between the first terminal T1 (gate electrode G) and the source electrode is the breakdown voltage of the first diode D1 due to the existence of the first diode D1. A certain first voltage _VZ1 . Due to this first voltage _VZ1 , a current also flows to the gate electrode G, and the potential of the gate electrode G rises to finally reach the first voltage _VZ1 .

As described above, the first diode D1 has a breakdown voltage (first voltage V _Z1 ) that is sufficiently higher than the threshold voltage between the gate and source that turns on the source and drain. The switching element SW is turned on by outputting the positive voltage _VOUT to the second terminal T2.

Note that the positive voltage V _OUT is set higher than the first voltage V _Z1 so that the current flows in the direction indicated by the thick arrow in FIG. 3 . Furthermore, the positive voltage _VOUT is composed of the first voltage _VZ1 and the second voltage, which is the breakdown voltage that causes the third diode D3 to conduct from the cathode side to the anode side, so as to minimize current flow through the third diode D3. V _Z2 and the sum V _Z1 +V _Z2 or less.

Here, with the positive voltage V _OUT applied between the third terminal T3 and the second terminal T2, for example, surge noise is applied to the gate electrode G via capacitive coupling formed between the gate and the drain. Assume that the voltage between the gate and the source drops below _VZ1 after the input. In this case, due to the presence of the third diode D3, the gate-source voltage does not drop below V _OUT -V _Z2 .

This is because even if the gate-source voltage falls below V _OUT -V _Z2 , in this case, a voltage higher than the breakdown voltage is applied between the cathode and anode of the third diode D3. is. As a result, as indicated by the thick dotted line in FIG. 4, a current that compensates for the voltage drop due to the noise flows from the voltage output device 9 to the gate electrode G through the third diode D3. FIG. 4 is a diagram showing the path of current that compensates for the gate-source voltage drop.

In other words, the third diode D3 forms an electrical path for suppressing voltage fluctuations between the gate and the source caused by the surge noise when the surge noise is input to the gate electrode G.

The conductive state between the source and the drain of the switching element SW changes depending on the voltage applied between the gate and the source. Therefore, even if noise is input to the gate electrode, the voltage between the gate and the source does not drop excessively, thereby avoiding an excessive increase in the resistance value between the source and the drain due to the noise. As a result, even if noise input to the gate electrode G causes a current to flow between the source and the drain, excessive heat generation of the switching element SW can be suppressed.

In order to suppress an increase in the source-drain resistance value due to noise input to the gate electrode G, for example, the positive voltage V _OUT output by the voltage output device 9 is increased to near V _Z1 +V _Z2 , or And/or, it is preferable to lower the breakdown voltage (second voltage V _Z2 ) of the third diode D3 to bring V _OUT −V _Z2 closer to the first voltage V _Z1 .

[1-3-2. Operation when Switching Element is in OFF State] Next, the operation of the drive circuit 1 when the switching element SW is in the OFF state will be described with reference to FIG. FIG. 5 is a diagram showing the operation when the switching element is in the off state. As shown in FIG. 5, when the switching element SW is turned off, the voltage output device 9 outputs 0V between the third terminal T3 and the second terminal T2.

At this time, the potential of the side of the capacitor element C connected to the third terminal T3 drops from _VOUT to 0V. On the other hand, the potential of the side of the capacitor element C connected to the first terminal T1 drops to V _Z1 -V _OUT as the potential drops. This potential drop causes current to flow from the gate electrode G to the capacitor element C and from the capacitor element C to the voltage output device 9 as indicated by the thick arrows in FIG. As a result, the potential of the gate electrode G finally drops to V _Z1 -V _OUT .

As described above, V _OUT is greater than V _Z1 , so when the voltage output device 9 outputs 0V, the potential of the gate electrode G, that is, the voltage between the gate and source becomes negative. By setting the voltage between the gate and the source to a negative voltage in this manner, the switching element SW can be reliably turned off.

Here, for example, assume that a large voltage change occurs between the source and the drain while 0 V is applied between the third terminal T3 and the second terminal T2. At this time, surge noise may be input to the gate electrode G via capacitive coupling formed between the gate and the drain, and the voltage between the gate and the source may rise above _VZ1 . However, the existence of the capacitor element C having a large capacitance suppresses the increase in the voltage between the gate and the source. This is because the charge generated by the noise is stored in the capacitor element C. FIG. That is, by storing the charge generated by the noise in the capacitor element C as well, the voltage rise can be suppressed as compared with the case where the charge is stored only by the capacitance component formed in the gate electrode G. be. Thus, the drive circuit 1 can suppress the occurrence of erroneous ignition.

Further, for example, even if a large surge noise occurs and the voltage rise due to the noise cannot be suppressed even by the capacitor element C, the voltage between the gate and the source is higher than the forward voltage of the third diode D3. not voltage. Here, the forward voltage of the diode means the voltage required to conduct the diode from the anode side to the cathode side.

This is because even if the voltage between the gate and the source rises above the forward voltage of the third diode D3, in this case, a voltage larger than the forward voltage is generated between the anode and cathode of the third diode D3. This is because it is applied. As a result, current flows from the third diode D3 to the voltage output device 9 as indicated by the thick dotted line in FIG. FIG. 6 is a diagram showing current paths for suppressing a voltage rise between the gate and the source.

In other words, the third diode D3 forms an electrical path for suppressing voltage fluctuations between the gate and the source caused by the surge noise when the surge noise is input to the gate electrode G.

Generally, the forward voltage of the diode is lower than the breakdown voltage, and the forward voltage of the third diode D3 is sufficiently lower than the breakdown voltage of the first diode D1, ie, the first voltage _VZ1 . Therefore, even if noise is input to the gate electrode G and the voltage between the gate and source rises to the forward voltage of the third diode D3, the switching element SW remains off. In other words, it is possible to prevent the switching element SW from being erroneously turned on due to noise input to the gate electrode G.

[1-4. Summary] As described above, the drive circuit 1 of the present embodiment suppresses the voltage between the gate and the source from fluctuating even when noise is input to the gate electrode G, thereby preventing the switching element SW from malfunctioning. can be suppressed. Therefore, the drive circuit 1 of the present embodiment is useful as a circuit for driving devices that generally have a low gate-source threshold voltage, such as semiconductor switching devices using gallium nitride-based materials and inexpensive MOSFETs. .

[1-5. Application example of drive circuit] [1-5-1. Overview] Hereinafter, the case where the drive circuit 1 described above is applied to various circuits using a semiconductor switching element SW such as a MOSFET or an IGBT will be exemplified. A switching element SW such as a MOSFET or an IGBT is often used in a power supply circuit having a relatively large capacity.
is applied.

[1-5-2. Application Example to Step-Down Chopper Power Supply Circuit] First, an application example in which the drive circuit 1 is applied to the step-down chopper power supply circuit 11 will be described with reference to FIG. FIG. 7 is a diagram showing an application example when the drive circuit is applied to a step-down chopper type power supply circuit. As shown in FIG. 7, the step-down chopper type power supply circuit 11 includes a first input section 13, a first output section 15, a first inductor element L1, a first switching element SW1, a second switching element SW2, Prepare.

The first input section 13 connects the input power source _Pi1 . The input power supply P _i1 may be a DC power supply, or may be a device that generates power by smoothing AC power after full-wave rectification or half-wave rectification. Specifically, the first input unit 13 includes a first input terminal I1 connected to the positive potential side of the input power supply _Pi1 , a second input terminal I2 connected to the 0 potential side of the input power supply _Pi1 , have

The first output section 15 has a first output terminal O1 and a second output terminal O2 connected to the second input terminal I2. A device (load) driven by the step-down chopper power supply circuit 11 is connected between the first output terminal O1 and the second output terminal O2.

One end of the first inductor element L1 is connected to the first output terminal O1. The first inductor element L1 is an element having an inductor component, such as a coil.

The first switching element SW1 is a MOSFET having a gate electrode G, a source electrode S, and a drain electrode D, for example. A drain electrode D of the first switching element SW1 is connected to the first input terminal I1, and a source electrode S is connected to the other end of the first inductor element L1. A gate driver 17 is connected between the gate and source of the first switching element SW1.

The gate driver 17 applies a PWM-controlled pulse signal having a predetermined cycle between the gate and source of the first switching element SW1. The gate driver 17 is a device corresponding to the voltage output device 9 described above.

The first switching element SW1 realizes a switching function of adjusting the voltage value output between the first output terminal O1 and the second output terminal O2 in the step-down chopper type power supply circuit 11 .

The second switching element SW2 is a MOSFET having a gate electrode G, a source electrode S, and a drain electrode D, for example. The drain electrode D of the second switching element SW2 is connected to the other end of the first inductor element L1, and the source electrode S is connected to the second output terminal O2.

Between the source and the drain of the second switching element SW2, the ON state and the OFF state are switched in a complementary manner to between the source and the drain of the first switching element SW1 with a predetermined dead time. In the step-down chopper type power supply circuit 11, the second switching element SW2 realizes a synchronous rectification function for the first switching element SW1.

Further, as shown in FIG. 7, the drain electrode D of the second switching element SW2 is connected to the positive potential side of the input power supply _Pi1 via the first switching element SW1.

Therefore, at the timing when the first switching element SW1 switches from the OFF state to the ON state while the second switching element SW2 is in the OFF state, the potential of the drain electrode D of the second switching element SW2 changes to the positive potential of the input power supply _Pi1 . abruptly changes to the side potential. Due to this sudden change in the potential of the drain electrode D, surge noise is input to the gate electrode G of the second switching element SW2 via capacitive coupling between the gate and the drain, and erroneous ignition occurs in the second switching element SW2. can occur.

Therefore, the drive circuit 1 is connected between the gate and source of the second switching element SW2. Specifically, the first terminal T1 of the drive circuit 1 is connected to the gate electrode G of the second switching element SW2, and the second terminal T2 is connected to the second output terminal O2.

In the step-down chopper type power supply circuit 11 having the above configuration, the first switching element SW1 realizes the switching function of the power supply circuit, and the second switching element SW2 realizes the synchronous rectification function of the power supply circuit. As a result, the step-down chopper power supply circuit 11 applies a DC voltage lower than the voltage of the input power supply _Pi1 and determined by the duty ratio of the pulse signal of the gate driver 17 to the first output terminal O1 and the second output terminal O2. can be output between

In the step-down chopper type power supply circuit 11 having the above configuration, before the power supply circuit operates, the driving circuit 1 turns on and then turns off the source-drain of the second switching element SW2. After that, by starting the switching operation of the first switching element SW1, the operation of the step-down chopper type power supply circuit 11 is started. As a result, the voltage between the gate and the source of the second switching element SW2, which is likely to cause erroneous ignition, is set to a negative voltage in advance to prevent erroneous ignition from occurring in the second switching element SW2 during the operation of the power supply circuit. can be suppressed.

[1-5-3. Application Example to Boost Chopper Power Supply Circuit] Next, an application example in which the drive circuit 1 is applied to the boost chopper power supply circuit 21 will be described with reference to FIG. FIG. 8 is a diagram showing an application example when the drive circuit is applied to a boost chopper type power supply circuit. As shown in FIG. 8, the boost chopper type power supply circuit 21 includes a second input section 23, a second output section 25, a second inductor element L2, a third switching element SW3, a fourth switching element SW4, Prepare.

The second input section 23 connects the input power source _Pi2 . The input power supply _Pi2 may be a DC power supply, or may be a device that generates power by smoothing AC power after full-wave or half-wave rectification. Specifically, the second input unit 23 includes a third input terminal I3 connected to the positive potential side of the input power supply _Pi2 , a fourth input terminal I4 connected to the 0 potential side of the input power supply _Pi2 , have

The second output section 25 has a third output terminal O3 and a fourth output terminal O4 connected to the fourth input terminal I4. A device (load) driven by the boost chopper type power supply circuit 21 is connected between the third output terminal O3 and the fourth output terminal O4.

One end of the second inductor element L2 is connected to the third input terminal I3. The second inductor element L2 is an element having an inductor component, such as a coil.

The third switching element SW3 is a MOSFET having a gate electrode G, a source electrode S, and a drain electrode D, for example. The drain electrode D of the third switching element SW3 is connected to the other end of the second inductor element L2, and the source electrode S is connected to the fourth input terminal I4. A gate driver 27 is connected between the gate and source of the third switching element SW3.

The gate driver 27 applies a PWM-controlled pulse signal having a predetermined cycle between the gate and source of the third switching element SW3. The gate driver 27 is a device corresponding to the voltage output device 9 described above.

The third switching element SW3 realizes a switching function of adjusting the voltage value output between the third output terminal O3 and the fourth output terminal O4 in the boost chopper type power supply circuit 21 .

The fourth switching element SW4 is a MOSFET having a gate electrode G, a source electrode S, and a drain electrode D, for example. A drain electrode D of the fourth switching element SW4 is connected to the third output terminal O3, and a source electrode S is connected to the other end of the second inductor element L2.

Between the source and the drain of the fourth switching element SW4, the on state and the off state are switched complementarily to the between the source and the drain of the third switching element SW3 with a predetermined dead time. The fourth switching element SW4 realizes a synchronous rectification function for the third switching element SW3 in the boost chopper type power supply circuit 21 .

Further, as shown in FIG. 8, the source electrode S of the fourth switching element SW4 is connected to the 0 potential side of the input power supply _Pi2 via the third switching element SW3. Also, the source electrode S is connected to the positive potential side of the input power supply _Pi2 via the second inductor element L2.

Therefore, at the timing when the third switching element SW3 switches from the off state to the on state when the fourth switching element SW4 is in the off state, the potential of the source electrode S of the fourth switching element SW4 changes to the positive potential of the input power supply _Pi2. The potential changes sharply from a potential higher than the potential on the other side to near zero potential. As a result, the source-drain voltage changes abruptly. Due to this rapid change in the voltage between the source and the drain, surge noise is input to the gate electrode G of the fourth switching element SW4 via the capacitive coupling between the gate and the drain, causing erroneous firing in the fourth switching element SW4. may occur.

Therefore, the drive circuit 1 is connected between the gate and source of the fourth switching element SW4. Specifically, the first terminal T1 of the drive circuit 1 is connected to the gate electrode G of the fourth switching element SW4, and the second terminal T2 is connected to the other end of the second inductor element L2.

In the boost chopper type power supply circuit 21 having the above configuration, the third switching element SW3 realizes the switching function of the power supply circuit, and the fourth switching element SW4 realizes the synchronous rectification function of the power supply circuit. As a result, the boost chopper type power supply circuit 21 outputs a DC voltage, which is equal to or higher than the voltage of the input power supply _Pi2 and determined by the duty ratio of the pulse signal of the gate driver 27, to the third output terminal O3 and the fourth output terminal O4. can be output between

In the boost chopper type power supply circuit 21 having the above configuration, the source-drain of the fourth switching element SW4 is turned on and then turned off by the driving circuit 1 before the power supply circuit operates. After that, by starting the switching operation of the third switching element SW3, the operation of the boost chopper type power supply circuit 21 is started. As a result, the voltage between the gate and the source of the fourth switching element SW4, which is likely to cause erroneous ignition, is set to a negative voltage in advance to prevent erroneous ignition from occurring in the fourth switching element SW4 during operation of the power supply circuit. can be suppressed.

[1-5-4. Application Example to Inverter Circuit] Next, an application example in which the drive circuit 1 is applied to the inverter circuit 31 will be described with reference to FIGS. 9A and 9B. FIG. 9A is a diagram showing an example of applying the drive circuit to an inverter circuit. FIG. 9B is a diagram showing another example of applying the drive circuit to the inverter circuit. As shown in FIGS. 9A and 9B, the inverter circuit 31 includes a third input section 33, a third output section 35, a fifth switching element SW5, and a sixth switching element SW6. Note that FIGS. 9A and 9B show only the circuit configuration of the arm for one phase of the inverter output, in order to simplify the explanation. Therefore, for example, a three-phase inverter circuit includes three inverter circuits 31 . In the three-phase inverter circuit, three inverter circuits 31 are connected in parallel to the input power supply _Pi3 .

The third input section 33 connects the input power supply _Pi3 . The input power supply _Pi3 may be a DC power supply, or may be a device that generates power by smoothing AC power after full-wave or half-wave rectification. Specifically, the third input section 33 includes a fifth input terminal I5 connected to the positive potential side of the input power supply _Pi3 , a sixth input terminal I6 connected to the negative potential side of the input power supply _Pi3 , have The negative potential side of the input power supply _Pi3 may be at 0 potential or at a potential lower than 0 potential.

The third output section 35 has a fifth output terminal O5 connected to one power input terminal of a device (load) driven by the inverter circuit 31 .

The fifth switching element SW5 is a MOSFET having a gate electrode G, a source electrode S, and a drain electrode D, for example. Fifth switching element S
The drain electrode D of W5 is connected to the fifth input terminal I5, and the source electrode S is connected to the fifth output terminal O5.

The sixth switching element SW6 is a MOSFET having a gate electrode G, a source electrode S, and a drain electrode D, for example. The drain electrode D of the sixth switching element SW6 is connected to the fifth output terminal O5, and the source electrode S is connected to the sixth input terminal I6.

In the inverter circuit 31 having the above configuration, the source-drain of the fifth switching element SW5 is switched between the ON state and the OFF state at a predetermined cycle, and the sixth switching element SW6 of the inverter circuit 31 in the same phase is switched. is switched between the ON state and the OFF state complementarily to the source-drain of the fifth switching element SW5 with a predetermined dead time interposed therebetween. When the ON state ratio of the fifth switching element SW5 is high, current flows from the input power supply _Pi3 side to the fifth output terminal O5 side, and when the ON state ratio of the fifth switching element SW5 is small, A current flows from the fifth output terminal O5 side to the input power supply _Pi3 side.

Therefore, in the inverter circuit 31, when the fifth switching element SW5 is switched from the OFF state to the ON state while current is flowing from the input power supply _Pi3 side to the fifth output terminal O5 side, the fifth switching element SW5 in the OFF state is switched to the ON state. There is a possibility that the voltage between the source and the drain of the sixth switching element SW6 changes greatly, and erroneous ignition occurs on the side of the sixth switching element SW6.

On the other hand, when the sixth switching element SW6 is switched from the off state to the on state while current is flowing from the fifth output terminal O5 side to the input power supply _Pi3 side, the fifth switching element SW5 in the off state , the voltage between the source and the drain of the switch may greatly change, and erroneous ignition may occur on the side of the fifth switching element SW5.

Therefore, in the inverter circuit 31 shown in FIGS. 9A and 9B, the driving circuit 1 is preferably connected to both the high-side fifth switching element SW5 and the low-side sixth switching element SW6. As a result, in the inverter circuit 31, when the inverter circuit 31 is operated by applying a PWM-controlled voltage to the gate electrode G of the fifth switching element SW5, and when the gate electrode of the sixth switching element SW6 In both cases where a PWM-controlled voltage is applied to G and the inverter circuit 31 is operated, the occurrence of erroneous ignition in the other switching element can be suppressed.

Further, as shown in FIGS. 9A and 9B, the inverter circuit 31 includes a resistive element R1. In the inverter circuit 31 shown in FIG. 9A, one end of the resistance element R1 is connected to the fifth output terminal O5 and the other end is connected to the sixth input terminal I6, so that the resistance element R1 becomes the source of the sixth switching element SW6. - connected in parallel between the drains. As a result, the potential of the source electrode S and the potential of the drain electrode D of the sixth switching element SW6 can be substantially the same when the inverter circuit 31 is not operating.

In the inverter circuit 31 shown in FIG. 9A, before the operation of the inverter circuit 31, the source-drain of the sixth switching element SW6 is turned on and then turned off, and the gate-source of the sixth switching element SW6 is turned off. Negative voltage. After that, the inverter circuit 31 is operated.

By connecting the resistance element R1 in parallel between the source and the drain of the sixth switching element SW6, when the sixth switching element SW6 is turned on before the inverter circuit 31 operates, the fifth switching element SW5 It is possible to suppress the occurrence of erroneous ignition. This is because, when the sixth switching element SW6 is turned on before the operation of the inverter circuit 31, the potential of the source electrode S of the fifth switching element SW5 connected to the drain electrode D of the sixth switching element SW6 is almost because it does not change. As a result, a negative voltage can be applied between the gate and source of the sixth switching element SW6 without erroneously firing the fifth switching element SW5.

After that, the operation of the inverter circuit 31 is started. At this time, it is preferable to start the operation by turning on the source-drain of the fifth switching element SW5. This is because the sixth switching element SW6 already has a negative voltage between the gate and the source as described above, so that the occurrence of erroneous ignition is suppressed. Further, by turning off the fifth switching element SW5 next, a negative voltage can be applied between the gate and the source in the off state of the fifth switching element SW5.

Due to the above operation, in the subsequent operation of the inverter circuit 31, erroneous firing of both the fifth switching element SW5 and the sixth switching element SW6 is less likely to occur, so that the operation of the inverter circuit 31 with high reliability is realized. can be done.

On the other hand, in the inverter circuit 31 shown in FIG. 9B, one end of the resistance element R1 is connected to the fifth output terminal O5, and the other end is connected to the fifth input terminal I5, so that the resistance element R1 is connected to the fifth switching element SW5. are connected in parallel between the source and drain of As a result, the potential of the source electrode S and the potential of the drain electrode D of the fifth switching element SW5 can be substantially the same when the inverter circuit 31 is not operating.

In the inverter circuit 31 shown in FIG. 9B, before the operation of the inverter circuit 31, the source-drain of the fifth switching element SW5 is turned on and then turned off, and the gate-source of the fifth switching element SW5 is turned off. Negative voltage. After that, the inverter circuit 31 is operated.

Since the resistance element R1 is connected in parallel between the source and the drain of the fifth switching element SW5, an erroneous point occurs in the sixth switching element SW6 when the fifth switching element SW5 is turned on before the inverter circuit 31 operates. It is possible to suppress the occurrence of arcs. This is because the potential of the drain electrode D of the sixth switching element SW6 connected to the source electrode S of the fifth switching element SW5 hardly changes when the fifth switching element SW5 is turned on before the inverter circuit 31 operates. It is from. As a result, a negative voltage can be applied between the gate and source of the fifth switching element SW5 without erroneously firing the sixth switching element SW6.

After that, the operation of the inverter circuit 31 is started. At this time, it is preferable to start the operation by turning on the source-drain of the sixth switching element SW6. This is because the gate-source voltage of the fifth switching element SW5 is already negative as described above, so that the occurrence of erroneous ignition is suppressed. Further, by turning off the sixth switching element SW6 next, a negative voltage can be applied between the gate and the source in the off state of the sixth switching element SW6.

Due to the above operation, in the subsequent operation of the inverter circuit 31, erroneous firing of both the fifth switching element SW5 and the sixth switching element SW6 is less likely to occur, so that the operation of the inverter circuit 31 with high reliability is realized. can be done.

The resistance element R1 may be connected in parallel between both the source and the drain of the fifth switching element SW5 and the source and the drain of the sixth switching element SW6.

Moreover, it is preferable that the resistance element R1 has a resistance value sufficiently larger than the impedance of the load connected to the fifth output terminal O5. For example, if the load connected to the fifth output terminal O5 is a motor, it preferably has a resistance value of about 100 kΩ to 200 kΩ. Thereby, it is possible to suppress the presence of the resistance element R1 from affecting the operation of the inverter circuit 31 .

[1-5-5. Application Example to Bidirectional Converter Circuit] Next, an application example in which the driving circuit 1 is applied to the bidirectional converter circuit 41 will be described with reference to FIG. 10 . FIG. 10 is a diagram showing an application example in which the drive circuit is applied to a bidirectional converter circuit. As shown in FIG. 10, the bidirectional converter circuit 41 includes a first input/output section 43, a second input/output section 45, a third inductor element L3, a seventh switching element SW7, and an eighth switching element SW8. , provided.

The first input/output unit 43 connects the first power source P1. The first power source P1 is, for example, a secondary battery. Specifically, the first input/output unit 43 includes a first input/output terminal IO1 connected to the positive potential side of the first power supply P1 and a second input/output terminal connected to the 0 potential side of the first power supply P1. and IO2.

The second input/output unit 45 connects the second power source P2. The second power source P2 is, for example, a secondary battery having a voltage lower than that of the first power source P1. Specifically, the second input/output unit 45 is connected to the third input/output terminal IO3 connected to the positive potential side of the second power supply P2, the 0 potential side of the second power supply P2, and the second input/output terminal IO2. and a fourth input/output terminal IO4.

One end of the third inductor element L3 is connected to the third input/output terminal IO3. The third inductor element L3 is an element having an inductor component, such as a coil.

The seventh switching element SW7 is a MOSFET having a gate electrode G, a source electrode S, and a drain electrode D, for example. A drain electrode D of the seventh switching element SW7 is connected to the first input/output terminal IO1, and a source electrode S is connected to the other end of the third inductor element L3.

The eighth switching element SW8 is a MOSFET having a gate electrode G, a source electrode S, and a drain electrode D, for example. The drain electrode D of the eighth switching element SW8 is connected to the other end of the third inductor element L3, and the source electrode S is connected to the second input/output terminal IO2.

In the above circuit, the ON state and the OFF state are switched at a predetermined cycle between the source and the drain of the seventh switching element SW7, and a predetermined dead time is interposed between the source and the drain of the eighth switching element SW8. The bidirectional converter circuit 41 functions as a step-down chopper type power supply by switching between the on state and the off state complementarily with the seventh switching element SW7. As a result, power is supplied from the first power supply P1 to the second power supply P2.

That is, in the above case, the seventh switching element SW7 implements a switching function of determining the voltage value output between the third input/output terminal IO3 and the fourth input/output terminal IO4. On the other hand, the eighth switching element SW8 implements a synchronous rectification function for the seventh switching element SW7.

As described above, when the bidirectional converter circuit 41 functions as a step-down chopper type power supply, there is a possibility that an erroneous ignition occurs on the side of the eighth switching element SW8 that implements the synchronous rectification function. Therefore, the drive circuit 1 is connected between the gate and source of the eighth switching element SW8. Specifically, the first terminal T1 of the drive circuit 1 is connected to the gate electrode G of the eighth switching element SW8, and the second terminal T2 is connected to the second input/output terminal IO2. Hereinafter, the drive circuit 1 connected to the eighth switching element SW8 will be referred to as "second drive circuit 1b".

On the other hand, between the source and the drain of the eighth switching element SW8, the ON state and the OFF state are switched at a predetermined cycle, and a predetermined dead time is interposed between the source and the drain of the seventh switching element SW7. The two-way converter circuit 41 functions as a boost chopper type power supply by switching on and off in a complementary manner with the 8-switching element SW8. As a result, power is supplied from the second power supply P2 to the first power supply P1.

That is, in the above case, the eighth switching element SW8 realizes a switching function of determining the voltage value output between the first input/output terminal IO1 and the second input/output terminal IO2. On the other hand, the seventh switching element SW7 implements a synchronous rectification function for the eighth switching element SW8.

As described above, when the bidirectional converter circuit 41 functions as a boost chopper type power supply, there is a possibility that an erroneous ignition occurs on the side of the seventh switching element SW7 that implements the synchronous rectification function. Therefore, the drive circuit 1 is also connected between the gate and source of the seventh switching element SW7. Specifically, the first terminal T1 of the drive circuit 1 is connected to the gate electrode G of the seventh switching element SW7, and the second terminal T2 is connected to the other end of the third inductor element L3. Hereinafter, the drive circuit 1 connected to the seventh switching element SW7 will be referred to as "first drive circuit 1a".

In the above-described bidirectional converter circuit 41 as well, in order to suppress the occurrence of erroneous ignition in the seventh switching element SW7 and the eighth switching element SW8, before the bidirectional converter circuit 41 operates, the gate of one of the switching elements A negative voltage is preferably applied between the sources.

However, in the bidirectional converter circuit 41, unlike other power supply circuits, in order to set a negative voltage between the gate and the source of one of the switching elements, the voltage between the source and the drain of the switching element is turned on and then turned off. Attempting to set the state may cause false firing in the other switching element.

Specifically, when the eighth switching element SW8 is turned on, the potential of the source electrode S of the seventh switching element SW7 connected to the positive potential side of the second power supply P2 via the third inductor element L3 changes to the 2 changes from the positive potential of the power source P2 to 0 potential. As a result, the source-drain voltage of the seventh switching element SW7 abruptly changes by the voltage of the second power supply P2, and there is a possibility that an erroneous ignition occurs in the seventh switching element SW7.

On the other hand, when the seventh switching element SW7 is turned on, the potential of the drain electrode D of the eighth switching element SW8 changes from the positive potential of the second power supply P2 to the positive potential of the first power supply P1. As a result, the voltage between the source and the drain of the eighth switching element SW8 abruptly changes from the voltage of the second power supply P2 to the voltage of the first power supply P1, which may cause erroneous ignition in the eighth switching element SW8. be.

Therefore, in the bidirectional converter circuit 41, a negative potential application circuit 47 as shown in FIG. to As a result, before the bidirectional converter circuit 41 operates, a negative voltage can be applied between the gate and the source of either switching element without causing erroneous ignition in the seventh switching element SW7 and the eighth switching element SW8.

In the bidirectional converter circuit 41 shown in FIG. 10, the negative potential application circuit 47 is connected between the gate and source of the eighth switching element SW8. – may be connected between sources;

[1-5-6. Negative Potential Application Circuit] Hereinafter, a configuration example of the negative potential application circuit 47 and a method for applying a negative potential to the gate electrode G using the negative potential application circuit 47 will be described with reference to FIG. First, the configuration of the negative potential application circuit 47 will be described. As shown in FIG. 10, the negative potential applying circuit 47 has a negative potential applying capacitor element C1, a charging resistance element R2, a discharging resistance element R3, a charging power source P3, and a charging/discharging switching element SW9.

One end of the negative potential applying capacitor element C1 is connected to the gate electrode G of the switching element to which the negative potential applying circuit 47 is connected, and the other end is connected to the positive potential side of the charging power source P3 via the charging resistance element R2. In FIG. 10, the switching element to which the negative potential applying circuit 47 is connected is the eighth switching element SW8. The negative potential application capacitor element C1 is, for example, a general capacitor such as a ceramic capacitor, a film capacitor, a Mylar capacitor, or an electrolytic capacitor.

The charging resistance element R2 has one end connected to the other end of the negative potential applying capacitor element C1 and the other end connected to the positive potential side of the charging power source P3. The charging power supply P3 is, for example, a DC battery, a DC power supply device, or the like. As the charging power source P3, for example, the driving power source of the voltage output device 9 of the gate driver and the driving circuit 1 may be used to share the power source with other devices.

The discharge resistance element R3 has one end connected to the other end of the negative potential applying capacitor element C1 and the other end connected to the drain electrode D of the charge/discharge switching element SW9. The charge/discharge switching element SW9 is a MOSFET having a gate electrode G, a source electrode S, and a drain electrode D, for example. As described above, the drain electrode D of the charge/discharge switching element SW9 is connected to the other end of the discharge resistance element R3. The source electrode S is connected to the 0 potential side of the charging power supply P3.

A gate driver 49 is connected between the gate and source of the charge/discharge switching element SW9. For example, when the charge/discharge switching element SW9 is an n-channel MOSFET, the source-drain of the charge/discharge switching element SW9 can be turned on by outputting a positive voltage from the gate driver. On the other hand, by outputting 0 V from the gate driver, the source-drain of the charging/discharging switching element SW9 can be turned off.

While the first switching element SW1 to the eighth switching element SW8 used in the power supply circuit described above are elements capable of high-speed switching operation, the charge/discharge switching element SW9 does not require high-speed switching operation. Therefore, an inexpensive switching element can be used as the charge/discharge switching element SW9. In addition, the gate driver 49 does not need to output a high-frequency pulse signal and does not need to vary the duty ratio of the pulse signal, so the device can be made inexpensive.

Using the negative potential application circuit 47 having the above configuration, the gate electrode G can be set to a negative potential, that is, a negative voltage can be applied between the gate and the source in the following manner. First, 0V is output from the voltage output device 9 of the drive circuit 1 connected to the switching element to which the negative potential application circuit 47 is connected. Next, the negative potential application capacitor element C1 is charged through the charging resistance element R2. As a result, the potential on the side of the negative potential applying capacitor element C1 connected to the gate electrode G becomes close to zero potential, and the side connected to the charging resistance element R2 becomes the same potential as the positive potential of the charging power source P3. Charge is stored in the negative potential application capacitor element C1.

After that, when the source-drain of the charging/discharging switching element SW9 is turned on, the positive potential side of the negative potential applying capacitor element C1 is connected to the charging power supply P3 via the discharging resistance element R3 and the charging/discharging switching element SW9. It is connected to the 0 potential side and finally changes to 0 potential.

In accordance with the change in potential, the potential on the side of the negative potential applying capacitor element C1 connected to the gate electrode G changes from near 0 potential to negative potential. In this manner, the gate electrode G of the switching element connected to the negative potential application circuit 47 can be set to a negative potential.

(Other Embodiments) As described above, the above embodiments have been described as examples of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and modifications, replacements, additions, omissions, etc. can be made as appropriate. Therefore, other embodiments will be exemplified below.

[1] The breakdown voltage and forward voltage of the third diode D3 of the drive circuit 1 are preferably low. For example, the breakdown voltage of the third diode D3 is preferably less than 5V.

[2] In the inverter circuit 31, the resistance element R1 connected in parallel between the source and the drain of the switching element to which the drive circuit 1 is connected can be similarly provided in other power supply circuits other than the inverter circuit 31. For example, in the step-down chopper type power supply circuit 11 shown in FIG. 7, the resistance element R1 can be connected in parallel between the source and the drain of the second switching element SW2 to which the drive circuit 1 is connected. Further, in the boost chopper type power supply circuit 21 shown in FIG. 8, the resistance element R1 can be connected in parallel between the source and the drain of the fourth switching element SW4 to which the driving circuit 1 is connected.

[3] In order to perform strict voltage control in the drive circuit 1, the first diode D1 and the third diode D3 are preferably Zener diodes, but general diodes can also be used.

[4] The negative potential applying circuit 47 described with reference to FIG. 10 can be used not only for the switching elements of the bidirectional converter circuit 41 but also for switching elements such as other power supply circuits.

1 drive circuit 1a first drive circuit 1b second drive circuit 3 connection terminal 5 voltage holding circuit 7 negative potential generation circuit 9 voltage output device 11 step-down chopper type power supply circuit 13 first input section 15 first output section 17 gate driver 21 step-up Chopper-type power supply circuit 23 Second input section 25 Second output section 27 Gate driver 31 Inverter circuit 33 Third input section 35 Third output section 41 Bidirectional converter circuit 43 First input/output section 45 Second input/output section 47 Negative potential Application circuit 49 Gate driver C Capacitor element C1 Negative potential application capacitor element D1 First diode D2 Second diode D3 Third diode D4 Fourth diode I1 First input terminal I2 Second input terminal I3 Third input terminal I4 Fourth input terminal I5 fifth input terminal I6 sixth input terminal IO1 first input/output terminal IO2 second input/output terminal IO3 third input/output terminal IO4 fourth input/output terminal L1 first inductor element L2 second inductor element L3 third inductor element O1 First output terminal O2 Second output terminal O3 Third output terminal O4 Fourth output terminal O5 Fifth output terminal P1 First power supply P2 Second power supply P3 Charging power supply P _i1 to P _i3 Input power supply R1 Resistance element R2 Charging resistance element R3 Discharge resistance element SW Switching element SW1 First switching element SW2 Second switching element SW3 Third switching element SW4 Fourth switching element SW5 Fifth switching element SW6 Sixth switching element SW7 Seventh switching element SW8 Eighth switching element SW9 Charge/discharge switching Element T1 First terminal T2 Second terminal T3 Third terminal V _OUT positive voltage V _Z1 first voltage V _Z2 second voltage

Claims (15)

A driving circuit for a switching element that controls conduction between two terminals,
a first terminal connected to the gate electrode of the switching element;
a second terminal connected to one of the two terminals of the switching element;
a third terminal;
a voltage output device that outputs a drive voltage between the third terminal and the second terminal;
a first diode connected between the first terminal and the second terminal and having a cathode side facing the first terminal side; and a second diode connected in series with the first diode and having a cathode side facing the second terminal side. 2 diodes;
and a voltage holding circuit in which the current of the first diode and the current of the second diode always match ;
a capacitor element having one end connected to the first terminal and the other end connected to the third terminal;
a third diode having a cathode side connected to the third terminal, an anode side connected to the first terminal, and connected in parallel with the capacitor element;
A drive circuit. A driving circuit for a switching element that controls conduction between two terminals,
a first terminal connected to the gate electrode of the switching element;
a second terminal connected to one of the two terminals of the switching element;
a third terminal;
a voltage output device that outputs a drive voltage between the third terminal and the second terminal;
a first diode connected between the first terminal and the second terminal and having a cathode side facing the first terminal side; and a second diode connected in series with the first diode and having a cathode side facing the second terminal side. 2 diodes;
a voltage holding circuit having
a capacitor element having one end connected to the first terminal and the other end connected to the third terminal;
a third diode having a cathode side connected to the third terminal, an anode side connected to the first terminal, and connected in parallel with the capacitor element;
a negative potential application circuit that applies a negative potential to the gate electrode of the switching element,
The negative potential application circuit is
a negative potential applying capacitor element having one end connected to the gate electrode of the switching element;
a charging resistance element having one end connected to the other end of the negative potential applying capacitor element;
a charging power supply whose positive potential side is connected to the other end of the charging resistance element;
a discharge resistor element having one end connected to the other end of the negative potential applying capacitor element;
a charging/discharging switching element having two terminals whose conduction state is switched between an ON state and an OFF state, one of which is connected to the other end of the discharge resistance element, and the other of which is connected to the 0 potential side of the charging power supply;
A drive circuit. The driving voltage for turning on the switching element is higher than a first voltage for conducting the first diode from the cathode side to the anode side, and the first voltage and the third diode are connected from the cathode side to the anode side. 3. A drive circuit as claimed in claim 1 or claim 2 , which is less than or equal to the sum of the second voltage to conduct to. 4. The driving circuit according to claim 1 , wherein the capacitance of said capacitor element is ten times or more the capacitance of the capacitive component formed by said gate electrode. The first voltage for conducting the first diode from the cathode side to the anode side is higher than the voltage applied to the gate electrode required for conducting between the two terminals of the switching element. A drive circuit according to any one of the preceding claims. The anode side of the first diode is connected to the second terminal, the anode side of the second diode is connected to the first terminal, and the cathode side of the first diode is connected to the cathode side of the second diode. Item 6. The drive circuit according to any one of items 1 to 5 . The cathode side of the first diode is connected to the first terminal, the cathode side of the second diode is connected to the second terminal, and the anode side of the first diode is connected to the anode side of the second diode. Item 6. The drive circuit according to any one of items 1 to 5 . A driving circuit according to any one of claims 1 to 7 , wherein said first diode is a Zener diode. The drive circuit according to any one of claims 1 to 8 , wherein said third diode is a Zener diode. 10. The driving circuit according to any one of claims 1 to 9 , wherein before operation, the two terminals of the switching element are turned on and then turned off. 11. The drive circuit according to claim 1, further comprising a resistive element connected in parallel between said two terminals of said switching element. a first input terminal having a first input terminal connected to a positive potential side of an input power supply and a second input terminal connected to a 0 potential side of the input power supply; a first output terminal; a first output unit having a second output terminal connected to an input terminal; a first inductor element having one end connected to the first output terminal; a first switching element having one terminal connected to the first input terminal and the other terminal connected to the other end of the first inductor element; and an on state and an off state complementary to the first switching element. a step-down chopper type power supply circuit comprising: a second switching element, one of two switching terminals of which is connected to the other end of the first inductor element and the other of which is connected to the second output terminal; and the first terminal. is connected to the gate electrode of the second switching element, and the second terminal is connected to the second output terminal. a second input having a third input terminal connected to the positive potential side of the input power supply and a fourth input terminal connected to the 0 potential side of the input power supply; a third output terminal; a second output part having a fourth output terminal connected to the terminal; a second inductor element having one end connected to the third input terminal; one of which is connected to the other end of the second inductor element and the other of which is connected to the fourth input terminal; and the third switching element complementarily switches between an on state and an off state. a boost chopper type power supply circuit having two terminals, one of which is connected to the third output terminal and the other of which is connected to the other end of the second inductor element; 12. A power supply circuit comprising: a drive circuit according to any one of claims 1 to 11 , which is connected to gate electrodes of four switching elements, and the second terminal is connected to the other end of the second inductor element. a third input section having a fifth input terminal connected to the positive side of an input power supply and a sixth input terminal connected to the negative side of the input power supply; and a third output section having a fifth output terminal. a fifth switching element having two terminals that switch between an ON state and an OFF state at a predetermined cycle, one of which is connected to the fifth input terminal and the other of which is connected to the fifth output terminal; a sixth switching element having two terminals for switching between a state and an off state, one of which is connected to the fifth output terminal and the other of which is connected to the sixth input terminal; , wherein the first terminal is connected to the gate electrode of at least one of the fifth switching element or the sixth switching element, and the gate electrode of the fifth switching element or the sixth switching element is connected to the first terminal. A power supply circuit comprising: the drive circuit according to any one of claims 1 to 11 , wherein the second terminal is connected to one of terminals. a first input/output unit having a first input/output terminal connected to a positive potential side of a first power supply and a second input/output terminal connected to a 0 potential side of the first power supply; a third input/output terminal connected to the positive potential side of a second power supply having a lower voltage than the a third inductor element having one end connected to the third input/output terminal; and an ON state and an OFF state in a predetermined cycle when power is supplied from the first power supply to the second power supply. a seventh switching element having two terminals for switching between states, one of which is connected to the first input/output terminal and the other of which is connected to the other end of the third inductor element; and power from the second power supply to the first power supply. An eighth switching element, one of two terminals of which is switched between an on state and an off state at a predetermined cycle when supplying is connected to the other end of the third inductor element, and the other of which is connected to the second input/output terminal and a bidirectional converter circuit, wherein said first terminal is connected to the gate electrode of said seventh switching element, and said second terminal is connected to the other end of said third inductor element. a first drive circuit, which is the drive circuit according to any one of claims 1 to 3; A power supply circuit comprising: a second drive circuit which is the drive circuit according to any one of items 1 to 10 ;

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