WO2021060152A1 - ゲート駆動回路 - Google Patents
ゲート駆動回路 Download PDFInfo
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- WO2021060152A1 WO2021060152A1 PCT/JP2020/035313 JP2020035313W WO2021060152A1 WO 2021060152 A1 WO2021060152 A1 WO 2021060152A1 JP 2020035313 W JP2020035313 W JP 2020035313W WO 2021060152 A1 WO2021060152 A1 WO 2021060152A1
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- 239000004065 semiconductor Substances 0.000 claims abstract description 27
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
- H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
- H03K17/687—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices the devices being field-effect transistors
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/06—Modifications for ensuring a fully conducting state
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/06—Modifications for ensuring a fully conducting state
- H03K17/063—Modifications for ensuring a fully conducting state in field-effect transistor switches
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
- H03K17/51—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used
- H03K17/56—Electronic switching or gating, i.e. not by contact-making and –breaking characterised by the components used by the use, as active elements, of semiconductor devices
- H03K17/567—Circuits characterised by the use of more than one type of semiconductor device, e.g. BIMOS, composite devices such as IGBT
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K2217/00—Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00
- H03K2217/0063—High side switches, i.e. the higher potential [DC] or life wire [AC] being directly connected to the switch and not via the load
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K2217/00—Indexing scheme related to electronic switching or gating, i.e. not by contact-making or -breaking covered by H03K17/00
- H03K2217/0081—Power supply means, e.g. to the switch driver
Definitions
- the present invention relates to a gate drive circuit that drives a power semiconductor switch such as an IGBT.
- High-frequency high-power switching elements such as high-power inverters and DCDC converters often use high-frequency high-power switching elements.
- a high-frequency high-power switching element an IGBT (Insulated Gate Bipolar Transistor) or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is often used.
- the input characteristics of the drive terminal (for example, the gate terminal) of such an element are often capacitive, and a large current must flow during drive. Therefore, various circuits for driving these high-frequency high-power switching elements have been proposed. Such circuits are often referred to as gate drive circuits.
- the present invention relates to an improved high side driver used in this gate drive circuit.
- the gate drive circuit having the circuit configuration shown in FIG. 8 has also been used.
- this circuit configuration it is a gate drive circuit 3a configured by using an N-channel MOSFET as Q1a in FIG.
- the gate potential In order to operate the N-channel MOSFET in ON, the gate potential must be set to a voltage higher than the source potential.
- the source voltage of Q1a in FIG. 8 rises to the vicinity of the positive side voltage Vcc of the power supply of the gate drive circuit 3a.
- the positive side voltage Vcc is supplied to the positive side voltage terminal 4 in FIG. 8, and similarly in FIG. 7, the positive side voltage Vcc is supplied to the positive side voltage terminal 4.
- a bootstrap circuit and a level shift circuit as described below are configured to create a high potential for raising the gate potential of Q1a in FIG. 8 to a voltage higher than the source potential.
- a series circuit of the diode 12 (hereinafter referred to as D1) and the capacitor 13 (hereinafter referred to as C1) is connected to the OUT terminal 7 and the positive side voltage terminal as shown in FIG. Connect with 4. Then, when the OUT terminal 7 is at the GND potential, an electric charge is stored in C1, and when the IN terminal 5 is set to High and Q1a is turned on, the output side transistor of the level shift photocoupler 10 (hereinafter referred to as PC1) is turned on.
- PC1 the output side transistor of the level shift photocoupler 10
- a power source having a high potential for driving Q1a can be relatively easily produced by D1 and C1.
- an insulating element such as a photocoupler (PC1 in FIG. 8) is used to insulate the high-voltage power supply from the input potential of the IN terminal 5, or a level shift circuit or the like is used to shift the voltage level from the high-voltage power supply.
- PC1 in FIG. 8 a photocoupler
- a level shift circuit or the like is used to shift the voltage level from the high-voltage power supply. It is a device to provide a separate switch. Without such a device, it is considered difficult to create a circuit that turns Q1a ON / OFF using the input potential of the IN terminal 5.
- Patent Document 1 Patent No. 6303060
- Patent No. 6303060 discloses a gate drive circuit using a P-channel MOSFET and an N-channel MOSFET.
- a circuit configuration is disclosed in which an input signal is supplied to a P-channel MOSFET via a level shift circuit.
- Patent Document 2 Japanese Unexamined Patent Publication No. 2006-270382
- Japanese Unexamined Patent Publication No. 2006-270382 Japanese Unexamined Patent Publication No. 2006-270382
- a level shift circuit capable of high-speed operation is used in a configuration in which power is supplied to a high-side driver from a floating power supply. It is disclosed.
- Patent Document 3 Japanese Unexamined Patent Publication No. 2000-286687
- Japanese Unexamined Patent Publication No. 2000-286687 Japanese Unexamined Patent Publication No. 2000-286687
- Japanese Patent No. 6303060 Japanese Unexamined Patent Publication No. 2006-270382 Japanese Unexamined Patent Publication No. 2000-286687
- the performance is considered to be insufficient, so that the N-channel MOSFET is often used, and the potential for driving the N-channel MOSFET is high.
- High power supplies can also be made relatively easily.
- an insulating component or a voltage shift circuit for eliminating the voltage difference from the input signal is required, the circuit becomes complicated and expensive, and the N-channel MOSFET is used. It may not be possible to obtain a sufficient improvement effect by adopting it.
- the present invention has been made in view of such a problem, and an object of the present invention is to provide a high-side driver for a gate drive circuit using an N-channel MOSFET with a simpler circuit configuration.
- the present invention is a circuit for driving a power semiconductor switch in order to solve the above problems.
- a drain terminal is connected to a positive side Vdc of a power supply of the circuit, and a signal for driving the power semiconductor switch is transmitted.
- a main switch N-channel MOSFET in which a source terminal is connected to an OUT terminal that is an output terminal, a charge storage circuit that injects a current from the positive side Vdc of the power supply of the circuit to store charge, and an output terminal of the charge storage circuit.
- a switch with a voltage detection function that operates by detecting a voltage difference from the positive side Vdc of the power supply of the circuit, and the switch with the voltage detection function has an output terminal voltage of the charge storage circuit of the circuit.
- the present invention is the high-side driver according to the above (1), which is a starting P-channel MOSFET connected in parallel with the main switch N-channel MOSFET, and is connected to the positive side Vdc of the power supply.
- An ON signal input terminal for inputting a start P-channel MOSFET having a source terminal connected and a drain terminal connected to the OUT terminal and a signal for operating the power semiconductor switch ON, and the start P channel.
- An ON signal input terminal connected to the gate terminal of the MOSFET is provided, and when a signal for operating the power semiconductor switch is input to the ON signal input terminal, the activation P-channel MOSFET is turned ON.
- the voltage of the OUT terminal rises, and the output terminal voltage of the charge storage circuit of the switch with the voltage detection function is the voltage of the positive side Vdc of the power supply of the circuit.
- High side that detects that the voltage is higher than a certain value applies a part or all of the output voltage of the charge storage circuit to the gate terminal of the main switch N channel MOSFET, and turns on the main switch N channel MOSFET. It is a driver.
- the present invention is the high-side driver according to the above (1) or (2), and the switch with the voltage detection function is the output terminal voltage of the charge storage circuit.
- the switch with the voltage detection function is the output terminal voltage of the charge storage circuit.
- the switch with the voltage detection function is the output terminal voltage of the charge storage circuit.
- the present invention is the high-side driver according to any one of (1) to (3) above, and is an OFF signal input terminal for inputting a signal for operating the power semiconductor switch OFF.
- a voltage conversion circuit connected between the positive side Vdc of the power supply of the circuit and the OFF signal input terminal, and between the positive side Vdc of the power supply of the circuit and the OFF signal input terminal.
- a voltage conversion circuit that divides the voltage and / or subtracts a constant value to convert the voltage is provided between the gate terminal of the main switch N channel MOSFET and the gate charge extraction MOSFET, and is provided between the main switch N channel.
- a high-side driver having a simpler configuration than before can be provided, and a gate drive circuit can be configured by using the high-side driver.
- FIG. 1 it is a circuit diagram which shows an example of the circuit structure of the specific gate drive circuit when the modification of the principle 1 is used. It is a circuit diagram of the conventional gate drive circuit using a P-channel MOSFET. It is a circuit diagram of the conventional gate drive circuit which used N channel MOSFET instead of P channel MOSFET.
- the gate drive circuit 26 in the explanatory diagram (FIG. 1A) of the first principle 1 includes a charge storage circuit 23 and a voltage detection in addition to the main switch N-channel MOSFET 21 (hereinafter referred to as Q21).
- a switch 22 with a function is provided.
- Q21 literally corresponds to a preferred example of a main switch N-channel MOSFET in the claims.
- the OUT terminal 25 is an output terminal, and the output voltage swings between a voltage lower than GND and a positive side voltage Vdc.
- the source terminal of Q21, which is the main switch of the gate drive circuit 26 of FIG. 1A, is connected to the OUT terminal 25, and the drain terminal thereof is connected to the positive voltage Vdc.
- Vgson means the gate threshold voltage of Q21.
- the charge storage circuit 23 stores the electric charge, but the pin for accumulating the electric charge and the pin for discharging the electric charge are different.
- a current is supplied from the a pin connected to the positive side voltage Vdc to charge the electric charge.
- the accumulated charge is superimposed on the potential of the OUT terminal 25 and is output from the b pin without flowing back to Vdc. Therefore, the potential of pin b is higher than the potential of OUT terminal 25 (source potential of Q1) by the voltage corresponding to the accumulated charge.
- the b pin is connected to the e pin of the switch 22 with a voltage detection function described below. Specific examples of the charge storage circuit 23 are shown in FIGS. 5a and 5b, which will be described in detail later. These specific examples give typical examples, and other circuit configurations may be used.
- the switch 22 with a voltage detection function in FIG. 1A the d pin is connected to the positive side voltage terminal 24 (Vdc), the e pin is connected to the b pin of the charge storage circuit 23, and the f pin is the gate terminal of Q21. Is connected to.
- the switch 22 with a voltage detection function monitors the voltage between the d pin (that is, the positive side voltage Vdc) and the e pin. As a result of this monitoring, when the voltage of the e-pin becomes higher than the voltage of the d-pin by a predetermined value or more, that is, when the voltage of the e-pin becomes higher than the voltage of Vdc by a predetermined voltage, the switch built in the self is turned on.
- the voltage corresponding to the charge accumulated in the charge storage circuit 23 is supplied from the b pin to the e pin, the voltage corresponding to the accumulated charge can be obtained by turning on the switch built in the switch 22 with the voltage detection function. Part or all of the above can be applied between the gate and the source of Q21. As a result, a voltage higher than Vdc is applied to the gate (between sources) of Q21, and if the gate-source voltage of Q21 is Vgson or higher, Q21 operates ON.
- the charge storage circuit 23 When the OUT terminal 25 rises from a low potential toward Vdc, the charge storage circuit 23 superimposes the voltage between the b pin and the c pin on the voltage of the OUT terminal 25 due to the already accumulated charge and outputs the voltage from the b pin. This is because the c pin is connected to the OUT terminal 25. Since the voltage superimposed and output in this way is superimposed on the voltage of the OUT terminal 25, if the potential of the OUT terminal 25 rises, the voltage of the b pin also rises accordingly. When the voltage of the OUT terminal 25 approaches Vdc further, the voltage of the e-pin of the switch 22 with the voltage detection function rises beyond the voltage of the d-pin (that is, the positive side voltage Vdc).
- the built-in switch referred to here corresponds to a preferable example of the internal switch in the claims.
- Vgson the voltage between the gate terminal and the source terminal in which Q21 is turned on and k is a constant.
- V CH > k x Vgson (2)
- k is a constant indicating the ratio of the output voltage of the charge storage circuit 23 applied to the gate terminal of Q21.
- k is a constant of 1 or less.
- the high-side driver having the configuration shown in FIG. 1A has its own output voltage, that is, the voltage of the OUT terminal 25 exceeds a certain level without using an insulating element such as a voltage shift circuit or a photocoupler. At that time, it has a function of autonomously operating ON and holding the state of ON operation.
- the f pin is connected to the gate terminal of Q21, and a resistor 29 may be provided between the gate terminal and the source terminal, but this is not an essential configuration.
- the terminal c of the charge storage circuit 12 is connected to the OUT terminal 25. Therefore, the increase in voltage at the OUT terminal 25 is applied to the terminal c.
- the c terminal of the electric storage circuit 12 may be connected to the OFF signal input terminal 34 instead of the OUT terminal 25.
- the details of the OFF signal input terminal 34 and the signal input to the OFF signal input terminal 34 will be described in FIG. 4 and the explanation of the principle 3 described later.
- FIG. 2 is a diagram for explaining another principle 2 of the present embodiment, in which the high-side driver of FIG. 1A described above is combined with a small-capacity semiconductor switch (starting P-channel MOSFET). Thereby, it is possible to provide a high-side driver of a gate drive circuit capable of driving the IGBT more rationally.
- FIG. 3 shows a graph schematically showing the process. This graph is a graph showing how the gate voltage rises with time. First, in the region A, the IGBT is in the OFF operation state, and only the gate voltage is rising.
- the area B is a time zone in which the IGBT shifts from the OFF operation to the ON operation. In this region, the rise in gate voltage temporarily slows down. In this region B, the transition to the ON operation is progressing, and it is a time zone in which the collector potential of the IGBT is decreasing. Since this region B is a time zone in which it is necessary to cover the discharge current of the charge of the feedback capacitance of the IGBT, the region B is a time zone in which a large drive current is required. Generally, since the output current of the gate drive circuit of the IGBT is finite, it takes a certain time for the charge of the feedback capacitance to be discharged. You may think that the time zone is this region B. In region C, the voltage between the collector terminal and the emitter terminal of the IGBT is almost saturated (the collector potential is sufficiently lowered). This region C is a region in which only the gate voltage further rises to further ensure the ON operation state of the IGBT.
- FIG. 2 Concept of FIG. 2 (Principle 2)
- the high-side driver of the gate drive circuit based on the principle shown in FIG. 2 is unique to the inventor of the present application as one of the circuits that reasonably satisfies the requirements in order to raise the gate voltage more quickly. It was invented in.
- the configuration of FIG. 2 is substantially the same as the configuration of FIG.
- Q22 corresponds to a preferred example of a starting P-channel MOSFET in the claims.
- the source terminal of Q22 is connected to Vdc (positive side voltage terminal 24), and the drain terminal is connected to the OUT terminal 25.
- a resistor 29b is connected between the Vdc and the gate terminal, and an ON signal is supplied to the gate terminal.
- the voltage V CH of the b pin of the charge storage circuit 23 and the threshold voltage V DET of the switch with the voltage detection function are set based on the above equations (1) and (2) so that the Q21 of the gate drive circuit is turned on. And set it appropriately.
- Appropriate setting means that when the IGBT enters the area B, the Q21 is set to operate ON.
- the gate voltage at which the IGBT to be driven enters the region B corresponds to equation (1) VO ON , Vdc is determined by design, and V CH is from equation (2) to Q21. It is determined from Vgson using a coefficient k. Therefore, the V DET of the equation (1) can be obtained from these values. Each voltage value may be set by such a calculation.
- the Q21 turns ON, so that a large current can be supplied to the gate terminal of the IGBT to be driven, and the driving target can be driven.
- the IGBT can be driven at high speed.
- the charge storage circuit 23 of the high-side driver discharges the accumulated charge completely, the ON operation of Q21 cannot be maintained and the Q21 is in the OFF operation state, but the discharge time constant of the accumulated charge amount is determined by the IGBT to be driven. If it is set longer than the time for passing through the region B (see FIG. 3), the requirement for operating the IGBT can be satisfied. If the IGBT to be driven enters the region C (see FIG.
- the P-channel MOSFET Q22 has a current. It is enough to supply. That is, the IGBT can be sufficiently driven.
- the N-channel MOSFET that is, Q21
- the current value is inferior to that of the N-channel MOSFET, but the power supply voltage Vdc.
- a P-channel MOSFET that is, Q22
- the present invention can provide an inexpensive gate drive circuit that is suitable for high-speed driving of an IGBT to be driven, has a simple circuit configuration, and is inexpensive.
- the g pin of the voltage conversion circuit 31 is connected to Vdc, the i pin is connected to the OFF signal input terminal 34, and the h pin is connected to the gate terminal of Q32.
- the source terminal of Q32 is connected to the OFF signal input terminal 34, and the drain terminal is connected to the backflow prevention circuit 33.
- the h pin is a so-called output terminal of the voltage conversion circuit 31, and corresponds to a preferable example of the output terminal in the claims.
- One end of the backflow prevention circuit 33 is connected to the drain terminal of Q32, and the other end is connected to the f terminal of the switch 22 with a voltage detection function, that is, the gate terminal of Q21.
- the backflow prevention circuit 33 may be, for example, a series circuit of a diode and a resistor, and the cathode side of the diode may be connected to the drain terminal of Q32 and the anode side may be connected to the f pin of the switch 22 with a voltage detection function.
- the Q21 In order not to interfere with the OFF operation of the IGBT that is the driving target, the Q21 must be rapidly put into the OFF operation state.
- the collector current of the IGBT When the IGBT to be driven shifts from the ON operation to the OFF operation, the collector current of the IGBT rapidly decreases, so that noise due to the generated magnetic flux and spike noise due to the wiring inductance of the collector circuit are generated in the system. These noises may be superimposed on the control circuit and the drive circuit, causing the elements constituting the circuit to malfunction. Therefore, the circuit configuration for shifting the Q21 from the ON operation to the OFF operation state is required to prevent malfunction due to noise and to have a high resistance to noise.
- FIG. 4 shows a circuit configuration having a high noise immunity when the N-channel MOSFET 21 (Q21), which is the main switch of the gate drive circuit, is turned off.
- the circuit configuration shown here is characterized in that the OFF signal input terminal 34 is connected to the source terminal of the gate charge extraction MOSFET 32 (Q32). That is, the characteristic configuration that the OFF signal input terminal 34 is connected to the source terminal instead of the gate terminal of Q32 is adopted.
- the voltage conversion circuit 31 has a voltage conversion function of dividing the voltage between the g pin and the i pin and / or converting the voltage by processing such as subtracting a constant value.
- the voltage conversion circuit converts the voltage between the g pin and the i pin by a predetermined mechanism, and outputs the converted voltage between the h pin and the i pin.
- the output voltage shall be a positive voltage.
- the h pin is a suitable example of an output terminal in the claims.
- the voltage conversion function will be described as an example of a process of subtracting a constant voltage, but the voltage may be divided (resistor voltage division) by using a resistor or the like.
- h-pin-i-pin voltage g-pin-i-pin voltage-constant voltage
- h-pin-i-pin voltage (g-pin-i-pin voltage) x t
- both of the above processes may be applied. That is, the voltage may be divided after subtracting a certain value. Alternatively, the pressure may be divided and then a constant value may be subtracted.
- the voltage (difference) between the g pin and the i pin further increases. Along with this, the voltage between the h pin and the i pin also rises, and when the gate threshold voltage of Q32 is exceeded, Q32 is turned on.
- the gate potential of Q21 becomes a voltage value higher than the potential of the OFF signal input terminal 34 by the amount of the voltage drop generated in the backflow prevention circuit 33. If the gate potential of Q21 is set lower than the gate threshold voltage (Vgson) of Q21, Q21 operates OFF. As a result of this operation, the bootst slap circuit is in a state that does not interfere with the OFF operation of the IGBT (IGBT that is the drive target connected to the OUT terminal 25) (not shown).
- the OFF operation of the IGBT to be driven is not hindered, but in order to maintain this state, the state of OFF operation of Q21 even when the OUT terminal 25 is at the Low voltage state. Must be maintained. Therefore, assuming that the Low voltage of the OUT terminal 25 is VO low and the voltage drop of the backflow prevention circuit 22 is V dr , the input voltage V IN low of the OFF signal input terminal 34 for turning off the Q21 is expressed by the following equation (4). ) Must be satisfied. Further, in the V INlow satisfying the equation (4), since it is necessary to operate the Q32 ON, the gate threshold voltage of the Q32 is set to VgsonQ32, and the conversion equation of the voltage conversion circuit 31 is expressed by the equation (3).
- the input voltage itself of the OFF signal input terminal 34 is expressed as VIN. Further, Vm represents a constant voltage used at the time of conversion in the voltage conversion circuit 31. Further, expressing the gate threshold voltage of Q21 in Vgson is the same as the principle 1.
- Q32 is in the OFF operation
- Q21 is in the ON operation
- the OFF signal input terminal 34 is connected to the source terminal of the MOSFET 32 (Q32). Therefore, unless the voltage of the OFF signal input terminal 34 is changed from Vdc to VINlow, the state of this circuit does not change to a state that does not interfere with the OFF operation of the IGBT to be driven. That is, in the specific example of each voltage described above, the state of the OFF signal input terminal 34 does not change to a state that does not interfere with the OFF operation of the IGBT unless the OFF signal input terminal 34 is changed from + 15V to -3V.
- the high-side driver in FIG. 4 requires a voltage change of 18V to change its state, and from the opposite perspective, it does not change its state for a voltage change (noise) of less than 18V. means. That is, it can be said that the noise tolerance is very high.
- the input signal is input to the gate terminal of the gate charge extraction MOSFET 32 (Q32), and the source terminal of Q32 has a fixed potential, for example, Vee (minus). It is often connected to the side voltage).
- the input signal is initially Vee, and in order to cause a state change (that is, in order to turn off Q21), a voltage of about Vee + 5V is applied to the gate terminal of Q32 to press Q32.
- a method of turning on the operation and turning off the Q21 is common.
- the voltage between the gate and the source of Q32 changes the state of the high-side driver by turning on Q32 when the voltage changes from 0V to 5V.
- the gate terminal of the MOSFET has a high input impedance and is easy to get noise.
- this circuit (FIG. 4) shown in Principle 3 can take a voltage difference of 3 times or more, and is clearly superior to the conventional method in terms of noise immunity characteristics.
- Example of Charge Storage Circuit Specific examples of the charge storage circuit 23 described so far are shown in FIGS. 5A and 5B. As shown in FIGS. 1, 2, and 4, the charge storage circuit 23 has a pin, b pin, and c pin. In the circuit shown in Example 1 of FIG. 5A, a series circuit of the diode D1 and the capacitor C1 is provided between the a pin and the c pin, and the connection point between the diode D1 and the capacitor C1 is connected to the b pin. There is. With such a circuit configuration, when the a pin is higher than the voltage drop of the diode D1 than the c pin, an electric charge is accumulated in the capacitor C1, and as a result, a voltage is generated in the capacitor C1.
- This voltage appears on pin b (between pin c and pin c). As described above, the voltage appearing on the b pin is connected to the e pin of the switch 22 with the voltage detection function, and is supplied to the gate terminal of the Q21 via the switch 22 with the voltage detection function.
- the circuit shown in Example 2 of FIG. 5A is a circuit in which a Zener diode D2 is connected in series with a diode D1 with respect to the circuit of Example 1. As a result, the capacitor C1 can be charged (accumulated) with a lower voltage by the amount of the voltage drop of the Zener diode D2.
- the circuit shown in Example 3 of FIG. 5A is a circuit in which the resistor R1 is connected in series with the diode D1 with respect to the circuit of Example 1. As a result, the charging current can be limited by the value of the resistor R1.
- 5A is a circuit in which a Zener diode D2 and a resistor R1 are connected in series with a diode D1 with respect to the circuit of Example 1.
- the capacitor C1 can be charged (accumulated) with a lower voltage by the amount of the voltage drop of the Zener diode D2, and the charging current can be limited by the value of the resistor R1.
- the circuit shown in Example 5 of FIG. 5B is a circuit in which the resistor R2 is connected in parallel to the capacitor C1 with respect to the circuit of Example 1. As a result, the electric charge accumulated in the capacitor C1 can be discharged, and the voltage output to the b pin can be lowered with the passage of time.
- the circuit shown in Example 6 of FIG. 5B is a circuit in which a resistor R3 is provided between the connection point between the diode D1 and the capacitor C1 and the b pin with respect to the circuit of Example 5. As a result, the value of the current discharged from the b pin can be limited by the value of the resistor R3.
- 5B is a circuit in which the Zener diode D3 is connected between the c pin and the b focus and the resistor R1 is removed from the circuit of Example 6.
- the value of the resistor R3 can limit the value of the current discharged from the b pin, and the voltage output from the b pin can be limited to the voltage drop that occurs in the Zener diode D3.
- FIG. 6A shows a circuit configuration of a gate drive circuit which is an example of a specific embodiment of the present invention.
- the range surrounded by the broken line is the gate drive circuit 40, which is a characteristic circuit in the present embodiment.
- Q21 is a P-channel MOSFET as a main switch.
- the P-channel MOSFETs Q44, diode D4, resistor R3, and resistor R5 constitute a switch 22 with a voltage detection function.
- Q44 corresponds to a preferred example of an internal switch in the claims.
- the charge storage circuit 23 is composed of a diode D2, a diode D3, and a capacitor C1. The operation of these circuits is as described above.
- Q22 is a small-capacity semiconductor switch, which corresponds to Q22 in FIG. 2 and operates in the same manner as Q22 in FIG. Q32 corresponds to Q32 in FIG. 4, and operates in the same manner as Q32 in FIG.
- the voltage conversion circuit 31 of FIG. 6A is composed of a diode D1, a resistor R2, and a resistor R1 and operates in the same manner as the voltage conversion circuit 31 of FIG.
- the backflow prevention circuit 33 is composed of a diode D5 and a resistor R4, and operates in the same manner as the backflow prevention circuit 33 of FIG.
- the high-side driver of the gate drive circuit 40 shown in FIG. 6A is composed of a single module, and the signal inputs of this module are represented by IN and inverted IN (in FIG. 6A, a symbol with a bar above IN is used.
- the inverted IN is an inverted signal of the IN signal (see FIG. 6A). It is assumed that the OUT terminal 25 and the IN terminal 45 swing from Vee to Vdc. Further, the inverting IN terminal 46 swings from Vdc to a voltage intermediate between Vdc and Vee.
- a circuit outside the gate drive circuit 40 is also shown in FIG. 6A.
- the control IC 50 is a device that controls ON / OFF of the power semiconductor switch.
- Vdc and Vee are supplied to the control IC 50 as power sources.
- the control IC 50 operates by this power supply, produces an IN signal, and supplies it to the IN terminal 45 of the gate drive circuit 40 (see FIG. 6A).
- the inverter 51 inverts this IN signal, creates an inverted IN signal, and supplies the inverted IN signal to the inverted IN terminal 46 of the gate drive circuit 40.
- V C1 of the capacitor C1 is charged by the current flowing from Vdc to Vee via the diode D3 and the diode D2.
- Charging voltage V C1 of the capacitor C1 is represented by the following formula (6).
- V C1 is adjustable by the Zener voltage V ZD3 constant-voltage diode D3.
- V C1 Vdc - Vee - V zd3 - VF D2 (6)
- V CH of the formula (1) described is equal to V C1.
- Q32 When the IN terminal 45 becomes High ( ⁇ Vdc), Q32 operates OFF, and the inverted IN terminal 46 becomes Low ( ⁇ intermediate potential between Vdc and Vee), Q22, which is a P-channel MOSFET which is a small-capacity semiconductor switch, changes. It operates ON. When Q22 is turned on, the voltage of the OUT terminal 25 starts to rise. However, this period is a period in which only the gate voltage of the IGBT is rising while the IGBT to be driven is still in the OFF operation (see region A in FIG. 3 described above).
- the switch 22 with a voltage detection function is its own switch, Q44, when the voltage between the e-pin and the d-pin reaches the threshold voltage V DET , that is, when the voltage of the OUT terminal 25 satisfies the equation (1). Is turned on. With the ON operation of Q44, the gate terminal of Q21 is a main switch N-channel MOSFET - between the source terminal, the voltage obtained by multiplying a constant k is applied to the storage voltage V C1 of the charge accumulation circuit 23, Q21 rapidly OFF operation Shifts to the ON operation state.
- the IGBT When Q21 shifts to ON operation, the IGBT is in a state of shifting from OFF operation to ON operation, and Q21 is responsible for a large current to cover the increase in gate current due to the feedback capacitance of the IGBT (Fig. 3). See region B).
- the amount of charge and the discharge time constant of the capacitor C1 are selected so as to cover the time zone of region B in FIG. After the charge of the capacitor C1 is discharged and the Q21 is turned off, the Q22 secures the gate voltage of the IGBT (see region C in FIG. 3).
- the IN terminal 45 starts to shift to Low, and the inverting IN terminal 46 shifts to High.
- the Q22 operates OFF.
- the gate drive circuit 40 of the present embodiment starts shifting the Q21 from the ON operation to the OFF operation state so as not to interfere with the OFF operation of the IGBT.
- the IN terminal 45 descends from Vdc toward Vee, a voltage is generated between the g pin and the i pin of the voltage conversion circuit 31. Along with this, the corresponding output voltage is output between the h pin and the i pin, which are the outputs of the voltage conversion circuit 31.
- the conversion formula of the voltage conversion circuit 31 is expressed by the following formula (8) if R1 >> R2.
- V hi is the h-pin-i-pin voltage that is the output of the voltage conversion circuit 31.
- V m of the formula (3) corresponds to Vz D1 of the following formula (8).
- V hi Vdc --V IN --Vz D1 (8)
- the conditions for the Q32 to operate ON are represented by the equation (5) already described. Assuming that the Low voltage of the OUT terminal 25 when the IGBT is in the OFF operation is VO low , the voltage of the IN terminal 45 which maintains the OFF operation state of the Q21 even if the voltage of the OUT terminal 25 drops is the above-mentioned formula. It is represented by (4).
- FIG. 6A The specific embodiment shown in FIG. 6A is an example in which the terminal c of the charge storage circuit 12 is connected to the OUT terminal 25, that is, the circuit configuration shown in FIG. 1A (principle 1) is used. is there.
- the circuit configuration shown in FIG. 1B (a modified example of the principle 1) may be used.
- FIG. 6B a circuit diagram of a specific embodiment using the configuration of FIG. 1B is shown in FIG. 6B. That is, as shown in FIG. 6B, the terminal c of the charge storage circuit 12 is connected not to the OUT terminal 25 but to the IN terminal 45.
- the high-side driver and the gate drive circuit provided with the high-side driver in the present embodiment have the following effects.
- the voltage generated by the charge storage circuit 23 is supplied to the main switch by using the switch 22 with a voltage detection function. Therefore, since the ON operation is autonomously performed by the voltage of the output voltage, it is not necessary to use a voltage shift circuit, an insulating element, or the like, and the circuit configuration can be simplified.
- a gate drive circuit suitable for high-speed drive of the power semiconductor switch, having a simple circuit configuration, and inexpensive is provided. can do.
- the embodiment described above is an example as a means for realizing the present invention, and should be appropriately modified or changed depending on the configuration of the device to which the present invention is applied and various conditions, and the present invention is the present embodiment.
- the mode is not limited to.
- the IGBT is mainly described as the power semiconductor switch to be driven, but other power semiconductor switches can also be applied.
- the configuration of the charge storage circuit and the switch circuit with the voltage detection function is an example, and other circuits having the same function may be used.
- the MOSFET is used as a main component, but other configurations may be used as long as they have the same effect and effect.
- various semiconductor switches and switches using other materials may be used.
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- Power Conversion In General (AREA)
- Electronic Switches (AREA)
Abstract
Description
そのため、これら高周波大電力スイッチング素子を駆動する目的の回路が種々提案されている。このような回路は、しばしばゲート駆動回路と呼ばれる。本発明はこのゲート駆動回路に用いられる改良されたハイサイドドライバに関する。
上述したような高周波大電力スイッチング素子を駆動する従来のゲート駆動回路の例が、図7、図8に示されている。
図7に示すゲート駆動回路3は、IGBT2をONに駆動する素子として、PチャネルMOSFET1(以下、Q1と称する)を使用する回路である。Q1は、そのゲート電圧をソース電圧より低電圧にすることでON動作する。その結果、Q1は導通して、ドレイン端子にVcc電圧が表れる。このVcc電圧は、抵抗11を介して、出力端子7を経由してIGBT2のゲート端子に印加される。
このように、図7に示す回路構成のゲート駆動回路3によれば、IN端子5の入力電位によって、IGBT2をON動作(またはOFF動作)させることができる。
しかし、一般にPチャネルMOSFETは、NチャネルMOSFETより品種も少なくON抵抗も大きい傾向にあり、図7のQ1はNチャネルMOSFETを使用した方がIGBT2をON動作させる回路としては性能の向上が期待できる。
図8に示す回路構成の例では、ダイオード12(以下、D1と称する)、キャパシタ13(以下、C1と称する)との直列回路を、図8のように、OUT端子7と、プラス側電圧端子4との間に接続する。そして、OUT端子7がGND電位の時にC1に電荷を蓄えて、IN端子5をHighにしてQ1aがON動作するときはレベルシフト用フォトカプラ10(以下、PC1と称する)の出力側トランジスタをON動作させて、C1に充電した電荷をQ1aのゲート端子に印加する。これによって、Q1aがON動作してOUT端子7の電圧が上昇すると、C1とD1のカソード側とが接続する点の端子電圧はVccより高電圧となり、Q1aのゲート端子にVccより高い電圧を印加することができる。
例えば、後述する特許文献1(特許第6303060号公報)には、PチャネルMOSFETと、NチャネルMOSFETとを用いたゲート駆動回路が開示されている。特に、入力信号が、レベルシフト回路を介してPチャネルMOSFETに供給されることを特徴とする回路構成が開示されている。
本発明は、このような問題に鑑みなされたものであり、その目的は、より簡易な回路構成で、NチャネルMOSFETを用いたゲート駆動回路のハイサイドドライバを提供することである。
まず、本発明の原理を3種説明してから、本発明の具体的な実施形態であるゲート駆動回路のハイサイドドライバを説明する。
図1Aは、本実施形態において、上記課題を解決するための原理1を説明するブロック図である。図1Aは、本原理1に係るゲート駆動回路26が描かれているとともに、ゲート駆動回路26によって駆動されるIGBT27も描かれている。また、理解しやすい説明のために、特徴的な構成であるハイサイドドライバを中心に描いており、ゲート駆動回路の従来の同様の回路構成部分は従来と同様の作用であるため省略して図示されていない部分もある。
まず、図1Aにおいて、OUT端子25は出力端子であり、その出力電圧は、GNDより低電位な電圧と、プラス側電圧Vdcとの間の電圧をスイングする。図1Aのゲート駆動回路26のメインスイッチであるQ21のソース端子はOUT端子25に接続し、そのドレイン端子はプラス側電圧Vdcに接続する。Q21のゲート電圧がOUT端子25(すなわちソース端子)よりVgson(一定値)だけ高い電圧になると、Q21がON動作して、OUT端子25に出力電圧(=およそVdc電圧)が出力される。ただし、ここでVgsonとは、Q21のゲート閾値電圧を意味する。
まず、OUT端子25(に接続するcピン)が低電位(=およそGNDまたはGNDより低電位な電圧)となった時に、プラス側電圧Vdcに接続したaピンから電流の供給を受けて電荷を蓄積する。そして、蓄積された電荷は、OUT端子25の電位に重畳して、Vdcに逆流することなくbピンから出力される。従って、bピンの電位は、OUT端子25の電位(Q1のソース電位)より蓄積した電荷に対応する電圧分だけ電位が高くなる。bピンは、次に述べる電圧検出機能付きスイッチ22のeピンに接続している。電荷蓄積回路23の具体例が図5a、図5bに示されており、これらについては後に詳述する。これら具体例は、代表的な例を挙げたものであり、他の回路構成でもよい。
すると、電圧検出機能付きスイッチ22に内蔵したスイッチがON動作するOUT端子25の電圧VOON は、下記の式(1)で示される。Q21がON動作すると、OUT端子25の出力電圧は、Q21がON動作することで急速に電圧が上昇し、最終的に大略Vdcとなる。
VOON = VDET - VCH + Vdc (1)
ただし、Q21がON動作するゲート端子とソース端子間の電圧をVgsonとし、kを定数として、下記の式(2)が成立しているものとする。
VCH >= k × Vgson (2)
ここで、kは、電荷蓄積回路23の出力電圧のQ21のゲート端子に印加される割合を示す定数である。kは、1以下の定数である。電荷蓄積回路23の出力電圧の全部がQ21のゲート端子に印加されるときは、k=1となる。電荷蓄積回路23の出力電圧の1/2がQ21のゲート端子に印加されるときは、k=1/2となる。このように、電荷蓄積回路23の出力電圧の一部又は全部がQ21のゲート端子に印加される。
なお、図1Aに示すように、fピンはQ21のゲート端子に接続するが、このゲート端子とソース端子との間に抵抗29を設けてもよいが、必須の構成ではない。
上述した原理1においては、電荷蓄積回路12は、その端子cがOUT端子25に接続されている。したがって、OUT端子25における電圧の上昇は端子cに印加されている。これに対して、図1Bに示すように、電化蓄積回路12のc端子を、OUT端子25ではなく、OFF信号入力端子34に接続してもよい。ここで、OFF信号入力端子34及びそこに入力される信号の詳細は、後述する図4、原理3の説明において説明している。
図1Aで説明した原理1による回路の場合は、後述する図2に示すように、起動のための起動用PチャネルMOSFETを組み合わせることが好ましい。このような構成によって、IGBTをより合理的に駆動することができる。詳細は2.原理2で後述する。
これに対して、図1Bに示されている原理1の変形例(図1B)によれば、図1Aに示す回路構成と異なり、PチャネルMOSFETを組み合わせる必要がなくなり、より簡便な回路構成とすることもできる。ただし、駆動対象であるIGBTを連続的にON動作させなければいけない場合を除く。
図2は、本実施形態の他の原理2を説明する図であり、上述した図1Aのハイサイドドライバに、小容量の半導体スイッチ(起動用PチャネルMOSFET)を組み合わせたものである。これによって、IGBTをより合理的に駆動することができるゲート駆動回路のハイサイドドライバを提供することができる。
IGBTなどの半導体スイッチのゲート回路は、OFF動作からON動作に移行する過程で、大略3つの状態を経由する。図3にその過程を模式的に表したグラフが示されている。このグラフは、時間とともにゲート電圧が上昇していく様子を示すグラフである。まず、領域AではIGBTはOFF動作の状態であり、ゲート電圧だけが上昇している領域である。
領域Cは、IGBTのコレクタ端子-エミッタ端子間電圧はほぼ飽和(コレクタ電位は十分に下がっている)状態である。この領域Cは、ゲート電圧だけがさらに上昇してIGBTのON動作の状態をより確実にする領域である。
IGBTを高速でOFF動作からON動作の状態にスイッチングするには、領域Aや領域Cと比較して、領域Bにおいて十分に大きな駆動電流が必要であると考えられる。図2で示した原理のゲート駆動回路のハイサイドドライバは、このようなIGBTの特性に鑑み、より早くゲート電圧を上昇させるために要求を合理的に満たす回路の一つとして本願発明者が独自に発明したものである。
図2の構成は、図1の構成と概ね同様であるが、新たに起動用PチャネルMOSFET30が加えられ、ON信号がこの起動用PチャネルMOSFET30(以下、Q22と称する)に加えられている点が異なっている。Q22は、請求の範囲の起動用PチャネルMOSFETの好適な一例に相当する。Q22のソース端子は、Vdc(プラス側電圧端子24)に接続されており、ドレイン端子は、OUT端子25に接続する。Vdcとゲート端子の間には抵抗29bが接続されており、ゲート端子には、ON信号が供給されている。
図2に示すON信号入力端子28がLOWとなると、Q22がOFF動作の状態からON動作に移行していく。すると、OUT端子25の電圧がVdcに向かって上昇し始める。この時間帯は図3の領域Aにあたる。なお、図2では省略しているが、図2のOUT端子には、駆動対象であるIGBTが接続されているものとする。ここでいう領域対象Aとは、その駆動対象であるIGBTの領域Aという意味である。
さて、OUT端子の電圧(図示していないIGBTのゲート電圧)が駆動対象であるIGBTのゲート閾値電圧に達すると、上述したように領域Bに突入する。このときゲート駆動回路のQ21がON動作するように、電荷蓄積回路23のbピンの電圧VCH と電圧検出機能付きスイッチの閾値電圧VDETを上述した式(1)及び式(2)に基づいて適切に設定する。
なお、メインスイッチのNチャネルMOSFET(Q21)を駆動するにあたっては、フォトカプラや電圧シフト回路等を使用せずに駆動できるという図1と共通する特徴は、図2でも効率よく利用できる。本発明(原理2)は、駆動対象であるIGBTの高速駆動に適し、かつ回路構成がシンプルで、安価なゲート駆動回路を提供することができる。
これまで、原理1(図1A)や、原理2(図2)においては、駆動対象であるIGBTをOFF動作からON動作の状態に移行する際の動作に特徴を有する回路を主として説明してきた。一方、駆動対象であるIGBTがON動作からOFF動作に移行するタイミングでは、通常、別の回路が動作してIGBTのゲート回路の電荷を引き抜き始める必要がある。このときIGBTのOFF動作を妨げてはならない。
本原理3(図4)を示す回路構成は、これらの要求を満たす耐ノイズ性能の高い回路構成である。図4に示す回路構成は、図1に示す回路構成に、電圧変換回路31と、ゲート電荷引き抜き用MOSFET32(以下、Q32と称する)と、逆流防止回路33とを加えた回路構成である。
逆流防止回路33の一方端はQ32のドレイン端子に接続され、他方端は、電圧検出機能付きスイッチ22のf端子すなわちQ21のゲート端子に接続される。逆流防止回路33は、例えば、ダイオードと抵抗との直列回路でよく、ダイオードのカソード側がQ32のドレイン端子に接続され、アノード側が電圧検出機能付きスイッチ22のfピンに接続されてよい。
hピン-iピン電圧 = gピン-iピン電圧 - 一定電圧
hピン-iピン電圧 = (gピン-iピン電圧) × t
のように表してもよい。ここで、比例定数tは 0<t=<1 の範囲の数としてよい。また、上記両方の処理を適用してもよい。すなわち、一定値を差し引いてから、分圧してもよい。また、分圧してから、一定値を差し引いてもよい。
このQ21のゲート電位を、Q21のゲート閾値電圧(Vgson)より低く設定しておけば、Q21はOFF動作する。そして、この動作の結果、本ブートストスラップ回路は不図示のIGBT(OUT端子25に接続する駆動対象であるIGBT)のOFF動作を妨げない状態となる。
(項目1.)Q32のゲート閾値電圧を、VgsonQ32と表す。
(項目2.)電圧変換回路31の変換式は、hピン-iピン間の電圧をVhiとすると、下記(3)式で表される。
Vhi = Vdc - VIN - Vm (3)
(項目3.)逆流防止回路33の電圧降下値をVdrとする。
(項目4.)Q21がOFF動作の状態になった時のOUT端子25の電圧をVOlowとする。すると、上述した(4)式と(5)式とは以下の通りとなる。
VINlow < VOlow - Vdr + Vgson (4)
VINlow < Vdc - Vm - VgsonQ32 (5)
この指令を妨げないようにするには、逆流防止回路33の電圧降下値Vdr = 2V、Vgson = 4Vとすれば、上記式(4)からVINlow < -3V となる。さらに、Q32のゲート閾値電圧をVgsonQ32 = 4V、及びVINlow = -3Vと仮定すると、上記式(5)から、電圧変換回路31の変換式の定数Vm < 14V が求められる。
すなわち、上述した各電圧の具体例では、OFF信号入力端子34は+15Vから-3Vまで可変しなければIGBTのOFF動作を妨げない状態に状態変化しないのである。このことは、図4の本ハイサイドドライバが状態変化をするのに18Vの電圧変化が必要であり、逆の見方をすると18V未満の電圧変化(ノイズ)に対しては状態を変化させないことを意味する。すなわち、ノイズ耐量が非常に高いと言える。
これまで説明してきた電荷蓄積回路23の具体例が、図5A、図5Bに示されている。図1、図2、図4で示したように、電荷蓄積回路23は、aピン、bピン、cピンを有している。図5Aの例1で示す回路は、aピンとcピンとの間に、ダイオードD1と、キャパシタC1との直列回路が設けられており、ダイオードD1とキャパシタC1との接続点はbピンに接続している。このような回路構成によって、aピンがcピンよりダイオードD1の電圧降下より高い場合には、キャパシタC1に電荷が蓄積され、その結果、キャパシタC1に電圧が発生する。この電圧がbピン(とcピンとの間)に表れる。すでに説明したように、bピンに表れる電圧は、電圧検出機能付きスイッチ22のeピンに接続されており、電圧検出機能付きスイッチ22を介して、Q21のゲート端子に供給される。
図5Aの例3で示す回路は、例1の回路に対して、抵抗R1をダイオードD1に直列に接続した回路である。この結果、抵抗R1の値によって充電電流を制限することができる。
図5Aの例4で示す回路は、例1の回路に対して、ツェナダイオードD2と、抵抗R1とをダイオードD1に直列に接続した回路である。この結果、ツェナダイオードD2の電圧降下分だけ、低い電圧でキャパシタC1を充電する(電荷を蓄積する)とともに、抵抗R1の値によって充電電流を制限することができる。
図5Bの例6で示す回路は、例5の回路に対して、抵抗R3を、ダイオードD1とキャパシタC1との接続点と、bピンとの間に設けた回路である。この結果、抵抗R3の値によって、bピンから放電される電流の値を制限することができる。
図5Bの例7で示す回路は、例6の回路に対して、ツェナダイオードD3を、cピンとbピントの間に接続し、抵抗R1を除去した回路である。この結果、抵抗R3の値によって、bピンから放電される電流の値を制限し、また、bピンから出力する電圧を、ツェナダイオードD3に生じる電圧降下の電圧まで制限することができる。
図6Aには、本発明の具体的な実施形態の一例であるゲート駆動回路の回路構成が示されている。特に、破線で囲んだ範囲が、本実施形態において特徴的な回路であるゲート駆動回路40である。Q21は、メインスイッチとしてのPチャネルMOSFETである。PチャネルMOSFETであるQ44、ダイオードD4、抵抗R3、抵抗R5は、電圧検出機能付きスイッチ22を構成する。Q44は、請求の範囲の内部スイッチの好適な一例に相当する。
OUT端子25、及びIN端子45は、大略VeeからVdcまでスイングするとする。また、反転IN端子46は、VdcからVdcとVeeの中間の電圧までスイングする。
ゲート駆動回路40の外部の回路も図6Aには示されている。制御IC50は、電力半導体スイッチのON/OFFを制御する装置である。この制御IC50には、電源としてVdcとVeeが供給されている。制御IC50は、この電源によって稼働し、IN信号を作り出し、ゲート駆動回路40のIN端子45に供給する(図6A参照)。インバータ51は、このIN信号を反転し、反転IN信号を作り出し、ゲート駆動回路40の反転IN端子46に供給する。
VC1 = Vdc - Vee - Vzd3 - VFD2 (6)
すでに説明した式(1)のVCHは、VC1に等しい。この等式を(7)式とする。
VC1 = VCH (7)
Vhi = Vdc - VIN - VzD1 (8)
図6Aで示した具体的な実施の形態は、電荷蓄積回路12の端子cがOUT端子25に接続する構成、すなわち図1A(原理1)に示す回路構成を利用した例である。
これに対して、図1B(原理1の変形例)に示す回路構成を利用してもよい。このように、図1Bの構成を利用した具体的な実施形態の回路図が図6Bに示されている。すなわち、図6Bに示すように、電荷蓄積回路12の端子cがOUT端子25ではなく、IN端子45に接続されている。
このような構成を採用することによって、「1.2 原理1の変形例」で説明したように、PチャネルMOSFETを組み合わせる必要がなくなり、より簡便な回路構成とすることもできる。これは、図6Bで言えば、抵抗R7と、Q22とからなる回路が必ずしも必要ではなくなると言うことを意味している。
以上説明したように、本実施形態におけるハイサイドドライバ及びそれを備えたゲート駆動回路によれば、次のような効果を奏する。
電圧検出機能付きスイッチ22を用いて、電荷蓄積回路23が作る電圧をメインスイッチに供給している。したがって、出力電圧の電圧によって自律的にON動作するので、電圧シフト回路や、絶縁素子等を用いる必要がなくなり、回路構成を簡易にすることができる。
また、駆動対象である電力半導体スイッチの動作特性に鑑みて、より合理的な駆動方法を採用したので、電力半導体スイッチの高速駆動に適し、かつ回路構成がシンプルで、安価なゲート駆動回路を提供することができる。
また、駆動対象である電力半導体スイッチがOFF動作する際に、そのOFF動作を妨げない回路を提供することができる。さらに、従来の回路に比べて、対ノイズ性に優れた回路を提供することができる。
また、以上説明した実施形態は、本発明の実現手段としての一例であり、本発明が適用される装置の構成や各種条件によって適宜修正又は変更されるべきものであり、本発明は本実施形態の態様に限定されるものではない。例えば、上述した実施形態においては、駆動対象である電力半導体スイッチとしてIGBTを主として説明したが、他の電力半導体スイッチでも適用することができる。
また、電荷蓄積回路や、電圧検出機能付きスイッチ回路の構成は、一例であり、同様の機能を備えた他の回路を用いてもよい。さらに、本実施形態(本発明)では、MOSFETを主たる構成要素として利用しているが、同様の作用効果を奏するものであれば、他の構成を利用してもよい。例えば、各種半導体スイッチや、他の材料を用いたスイッチを利用してもよい。
1a NチャネルMOSFET
2 IGBT
3、3a ゲート駆動回路
4 プラス側電圧端子
5 IN端子
6、8 GND端子
7 OUT端子
9、10、11 抵抗
10 フォトカプラ
12 ダイオード
13 キャパシタ
21 NチャネルMOSFET
22 電圧検出機能付きスイッチ
23 電荷蓄積回路
24 プラス側電圧端子
25 OUT端子
26、26b ゲート駆動回路
27 IGBT
28 ON信号入力端子
29、29b 抵抗
30 起動用PチャネルMOSFET
31 電圧変換回路
32 MOSFET
33 逆流防止回路
34 OFF信号入力端子
40 ゲート駆動回路
50 制御IC
51 インバータ
Claims (4)
- 電力半導体スイッチを駆動する回路であって、
前記回路の電源のプラス側Vdcにドレイン端子を接続し、前記電力半導体スイッチを駆動する信号を出力する端子であるOUT端子にソース端子を接続したメインスイッチNチャネルMOSFETと、
前記回路の電源のプラス側Vdcから電流を注入して電荷を蓄積する電荷蓄積回路と、
前記電荷蓄積回路の出力端子と、前記回路の電源のプラス側Vdcとの電圧差を検出して動作する電圧検出機能付きスイッチと、
を備え、
前記電圧検出機能付きスイッチは、前記電荷蓄積回路の出力端子電圧が前記回路の電源のプラス側Vdcの電圧より一定電圧以上高くなったことを検出した場合、前記メインスイッチNチャネルMOSFETのゲート端子に前記電荷蓄積回路の出力電圧の一部又は全部を印加し、前記メインスイッチNチャネルMOSFETをON動作させるハイサイドドライバ。 - 請求項1記載のハイサイドドライバであって、
前記メインスイッチNチャネルMOSFETと並列に接続された起動用PチャネルMOSFETであって、前記電源のプラス側Vdcにソース端子を接続し、前記OUT端子にドレイン端子を接続した前記起動用PチャネルMOSFETと、
前記電力半導体スイッチをON動作させるための信号が入力するON信号入力端子であって、前記起動用PチャネルMOSFETのゲート端子に接続するON信号入力端子と、
を備え、
前記ON信号入力端子に前記電力半導体スイッチをON動作させるための信号が入力した場合に、前記起動用PチャネルMOSFETがON動作し、
前記起動用PチャネルMOSFETがON動作することによって、前記OUT端子の電圧が上昇し、
前記電圧検出機能付きスイッチが、前記電荷蓄積回路の出力端子電圧が、前記回路の電源のプラス側Vdcの電圧より一定電圧以上高くなったことを検出し、前記メインスイッチNチャネルMOSFETのゲート端子に前記電荷蓄積回路の出力電圧の一部又は全部を印加し、前記メインスイッチNチャネルMOSFETをON動作させるハイサイドドライバ。 - 請求項1又は2記載のハイサイドドライバであって、
前記電圧検出機能付きスイッチは、
前記電圧検出機能付きスイッチが、前記電荷蓄積回路の出力端子電圧が、前記回路の電源のプラス側Vdcの電圧より一定電圧以上高くなったことを検出した場合、ON動作して、前記メインスイッチNチャネルMOSFETのゲート端子に前記電荷蓄積回路の出力電圧の一部または全部を印加する内部スイッチ、
を備えるハイサイドドライバ - 請求項1から3のいずれか1項に記載のハイサイドドライバであって、
前記電力半導体スイッチをOFF動作させるための信号を入力するOFF信号入力端子と、
前記回路の電源のプラス側Vdcと、前記OFF信号入力端子との間に接続された電圧変換回路であって、前記回路の電源のプラス側Vdcと、前記OFF信号入力端子との間の電圧を分圧、及び/又は、一定値を差し引いて電圧変換する電圧変換回路と、
前記メインスイッチNチャネルMOSFETのゲート端子と、ゲート電荷引き抜き用MOSFETとの間に設けられ、前記メインスイッチNチャネルMOSFETのゲート端子から前記ゲート電荷引き抜き用MOSFETへ向かう方向にのみ電流を流す逆流防止回路と、
ドレイン端子を前記逆流防止回路に接続し、ソース端子を前記OFF信号入力端子に接続し、ゲート端子を前記電圧変換回路が変換した電圧を出力する出力端子に接続する前記ゲート電荷引き抜き用MOSFETと、
を備え、前記ゲート電荷引き抜き用MOSFETの前記ドレイン端子は、前記逆流防止回路を介して前記メインスイッチNチャネルMOSFETのゲート端子に接続しており、
前記OFF信号入力端子に、前記電力半導体スイッチをOFF動作させるための信号が入力され、前記OFF信号入力端子の電圧が、前記回路の電源のプラス側Vdcから下降した場合、前記電圧変換回路の前記変換した電圧を出力する出力端子の出力電圧が上昇し、前記電荷引き抜き用MOSFETがON動作し、前記メインスイッチNチャネルMOSFETがOFF動作するハイサイドドライバ。
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