Drive unit

Abstract

To be able to preferably respond to a high-speed operation of a switching element.SOLUTION: According to a driving device for driving a switching element, provided is the driving device comprising a high potential line; a high potential side switching control part for switching whether or not to connect a control terminal of the switching element to the high potential line; a high potential side first resistance element arranged in series with the high potential side switching control part, in a path from the control terminal of the switching element to the high potential line; a high potential side capacitor provided in parallel to the first resistance element, in the path from the control terminal of the switching element to the high potential line; and a high potential side discharge control part for controlling whether or not to discharge the high potential side capacitor.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present invention relates to a driving device for driving a switching element. [Background technology]

[0002] BACKGROUND ART Conventionally, a driving device that controls a switching element such as a transistor is known (see, for example, Patent Document 1). Patent Document 1: Japanese Patent Application Laid-Open No. 2000-324801 Summary of the Invention [Problem to be solved by the invention]

[0003] It is preferable that the drive device be able to handle high-speed operation of the switching elements. [Means for solving the problem]

[0004] In order to solve the above problem, one aspect of the present invention provides a drive device for driving a switching element. The drive device may include a high potential line. The drive device may include a high potential side switching control unit that switches whether or not a control terminal of the switching element is connected to the high potential line. The drive device may include a first high potential side resistor element arranged in series with the high potential side switching control unit in a path from the control terminal of the switching element to the high potential line. The drive device may include a high potential side capacitor arranged in parallel with the first resistor element in a path from the control terminal of the switching element to the high potential line. The drive device may include a high potential side discharge control unit that controls whether or not to discharge the high potential side capacitor.

[0005] The high potential side discharge control section may discharge the high potential side capacitor on the condition that the control voltage at the control terminal of the switching element is equal to or higher than the plateau voltage.

[0006] The switching element may be one of a pair of switching elements that perform complementary operation. The high-side discharge control unit may discharge the high-side capacitor during the period from the completion of turn-on of the switching element to be driven to the start of the next turn-off.

[0007] The first resistor may be arranged between the control terminal of the switching element and the high-side switching controller, and the high-side capacitor may be arranged in parallel with the first resistor between the control terminal of the switching element and the high-side switching controller.

[0008] The driving device may include a high-potential side diode arranged in parallel with the first resistive element between the control terminal of the switching element and the high-potential side capacitor.

[0009] The high-side discharge control section may be a high-side switch arranged between the high-side line and the connection point of the high-side diode and the high-side capacitor.

[0010] The driver may include a second high-side resistive element arranged in series with a high-side diode between the junction of the high-side capacitor and the high-side switch and the control terminal of the switching element.

[0011] The driver may include a third high-side resistive element arranged in series with the high-side switch between the junction of the high-side capacitor and the high-side switch and the high-side line.

[0012] The drive device may include a high-side fourth resistor element arranged in series with the high-side capacitor between the connection point of the high-side switching control unit and the first resistor element and the connection point of the high-side diode and the high-side switch.

[0013] The capacitance of the high-potential-side capacitor may be variable. The driving device may include a capacitance control section that controls the capacitance of the high-potential-side capacitor.

[0014] The resistance value of the second resistive element may be variable, and the driving device may include a resistance control section that controls the resistance value of the second resistive element.

[0015] The resistance value of the third resistor element may be variable, and the driving device may include a resistance control section that controls the resistance value of the third resistor element.

[0016] The fourth resistor element may have a variable resistance value, and the driving device may include a resistance control unit that controls the resistance value of the fourth resistor element.

[0017] The drive device may include a reference potential line having a lower potential than the high potential line. The drive device may include a reference potential side switching control unit that switches whether or not the control terminal of the switching element is connected to the reference potential line. The drive device may include a first resistance element on the reference potential side that is arranged in series with the reference potential side switching control unit in a path from the control terminal of the switching element to the reference potential line. The drive device may include a reference potential side capacitor that is arranged in parallel with the first resistance element on the reference potential side in a path from the control terminal of the switching element to the reference potential line. The drive device may include a reference potential side discharge control unit that controls whether or not to discharge the reference potential side capacitor.

[0018] At least one of the switching element and the high-side switch may be a wide bandgap semiconductor element based on at least one of silicon carbide, gallium nitride, gallium oxide, and diamond.

[0019] The high-side switch may be any of a transistor device, a photocoupler, a digital isolator, a mechanical relay, or a photodiode. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 2 is a diagram illustrating an example of a power supply circuit 200 according to a reference example. [Figure 2] 1 is a diagram illustrating an example of the configuration of a power supply circuit 100. FIG. [Figure 3]10 is a diagram illustrating an example of operation when the switching element 112-1 and the reference potential side circuit 140 are turned off. FIG. [Figure 4] 10 is a diagram showing another example of the configuration of the reference potential side circuit 140. FIG. [Figure 5] 10 is a diagram showing another example of the configuration of the reference potential side circuit 140. FIG. [Figure 6] 10 is a diagram showing another example of the configuration of the reference potential side circuit 140. FIG. [Figure 7] 10 is a diagram showing another example of the configuration of the reference potential side circuit 140. FIG. [Figure 8] 10 is a diagram showing another example of the configuration of the reference potential side circuit 140. FIG. [Figure 9] 10 is a diagram showing another example of the configuration of the reference potential side circuit 140. FIG. [Figure 10] 10 is a diagram showing another example of the configuration of the reference potential side circuit 140. FIG. [Figure 11] 10 is a diagram showing another example of the configuration of the reference potential side circuit 140. FIG. [Figure 12] 10 is a diagram showing another example of the configuration of the reference potential side circuit 140. FIG. [Figure 13] 13 shows an equivalent circuit of the reference potential side circuit 140 and the switching element 112-1 shown in FIG. [Figure 14] 1 is a diagram showing an example of the configuration of a power supply circuit 100 according to an embodiment of the present invention. [Figure 15] 10 is a diagram illustrating an example of the operation of the switching element 112-1 and the high-potential side circuit 130. FIG. [Figure 16] FIG. 10 is a diagram showing another example of the configuration of the high-potential side circuit 130. [Figure 17] FIG. 10 is a diagram showing another example of the configuration of the high-potential side circuit 130. [Figure 18] FIG. 10 is a diagram showing another example of the configuration of the high-potential side circuit 130. [Figure 19] FIG. 10 is a diagram showing another example of the configuration of the high-potential side circuit 130. [Figure 20] FIG. 10 is a diagram showing another example of the configuration of the high-potential side circuit 130. [Figure 21] FIG. 10 is a diagram showing another example of the configuration of the high-potential side circuit 130. [Figure 22] FIG. 10 is a diagram showing another example of the configuration of the high-potential side circuit 130. [Figure 23] FIG. 10 is a diagram showing another example of the configuration of the high-potential side circuit 130. DETAILED DESCRIPTION OF THE INVENTION

[0021] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention. In this specification and drawings, elements having substantially the same function and configuration are designated by the same reference numerals to avoid redundant description, and elements not directly related to the present invention are not shown. Furthermore, in a single drawing, elements having the same function and configuration may be designated by the same reference numeral, and the reference numerals may be omitted for other elements.

[0022] In this specification, when terms such as "same" or "equal" are used, it may include cases where there is an error due to manufacturing variations, etc. The error is, for example, within 10%. Furthermore, when terms such as "same" or "equal" are used, it may be a close value for cost reasons. A close value means, for example, adopting an E-series value from a non-series value, such as "changing 3.1 Ω to 3.3 Ω."

[0023] 1 is a diagram illustrating an example of a power supply circuit 200 according to a reference example. The power supply circuit 200 supplies power to a load. The power supply circuit 200 of this example includes switching elements 112-1 and 112-2, driving devices 210-1 and 210-2, a control circuit 114, a high potential line 120, and a reference potential line 122.

[0024] The switching elements 112-1 and 112-2 are, by way of example only, transistors such as MOSFETs. Each switching element 112 may have a drain terminal, a source terminal, and a gate terminal. If the switching element 112 is an insulated gate bipolar transistor (IGBT) or the like, the drain terminal and the source terminal are also referred to as a collector terminal and an emitter terminal. The gate terminal is an example of a control terminal that controls the on / off state of the switching element 112.

[0025] In this example, the switching element 112-1 and the switching element 112-2 are connected in series between a high potential line 120 and a reference potential line 122. A reference potential such as a ground potential is applied to the reference potential line 122. A high potential higher than the reference potential is applied to the high potential line 120. An external power supply may be connected to the reference potential line 122 and the high potential line 120. In addition, a capacitor 116 may be connected between the reference potential line 122 and the high potential line 120.

[0026] In this example, the drain terminal of the switching element 112-2 is connected to the high potential line 120, the drain terminal of the switching element 112-1 is connected to the source terminal of the switching element 112-2, and the source terminal of the switching element 112-1 is connected to the reference potential line 122.

[0027] The power supply circuit 200 supplies power to a load from a connection point 118 between the switching elements 112-1 and 112-2. The switching elements 112-1 and 112-2 switch between their on / off states in a complementary manner. That is, when one switching element 112 is in the on state, the other switching element 112 is controlled to the off state. This switches between connecting the load to the high potential line 120 or the reference potential line 122.

[0028] The driver 210-1 controls the switching element 112-1 to switch between an ON state and an OFF state. The driver 210-2 controls the switching element 112-2 to switch between an ON state and an OFF state. The driver 210-2 may have the same function and structure as the driver 210-1. In this example, the structure and operation of the driver 210-1 will be described, and a description of the driver 210-2 will be omitted. In this specification, the driver 210-1 may also be simply referred to as the driver 210.

[0029] The driving device 210 generates a control signal to be input to the gate terminal of the switching element 112. In this specification, the switching element 112-1 may be simply referred to as the switching element 112. The driving device 210 has a high potential side circuit 230 and a reference potential side circuit 240. The reference potential side circuit 240 includes a first switching control unit 11, a first resistor element 21 on the reference potential side, a first power supply 31, and a first capacitor 50. The high potential side circuit 230 includes a second switching control unit 12, a first resistor element 22 on the high potential side, and a second power supply 32.

[0030] The first power supply 31 and the second power supply 32 are arranged in series between the high potential line 40 and the reference potential line 42. The first power supply 31 and the second power supply 32 generate a voltage between the high potential line 40 and the reference potential line 42. A connection point 91 between the first power supply 31 and the second power supply 32 may be connected to the source terminal of the switching element 112.

[0031] The first switching control unit 11 and the second switching control unit 12 control the switching of the ON / OFF state of the switching element 112. In this example, the first switching control unit 11 and the second switching control unit 12 are transistors arranged in series between the high potential line 40 and the reference potential line 42 and operating complementarily. Each transistor shown in this specification and drawings may be a bipolar transistor, a MOSFET, an IGBT, a wide bandgap semiconductor element made primarily of at least one of silicon carbide, gallium nitride, gallium oxide, and diamond, or another semiconductor switching element. A connection point 92 of the first switching control unit 11 and the second switching control unit 12 is connected to the control terminal (gate terminal) of the switching element 112.

[0032] The first switching control unit 11 controls whether or not the control terminal of the switching element 112 is connected to the reference potential line 42. In this example, when the first switching control unit 11 is in the on state, the control terminal of the switching element 112 is connected to the reference potential line 42. The second switching control unit 12 controls whether or not the control terminal of the switching element 112 is connected to the high potential line 40. In this example, when the second switching control unit 12 is in the on state, the control terminal of the switching element 112 is connected to the high potential line 40.

[0033] The control circuit 114 controls the on / off states of the first switching control unit 11 and the second switching control unit 12. The control circuit 114 may generate control signals to be applied to control terminals of the first switching control unit 11 and the second switching control unit 12.

[0034] The first resistor element 21 is disposed in series with the first switching control unit 11 in a path between the control terminal of the switching element 112 and the reference potential line 42. In this example, the first resistor element 21 is disposed between the first switching control unit 11 and the reference potential line 42. However, it may be disposed between the connection point 92 and the first switching control unit 11. When the first switching control unit 11 is turned on, the charge accumulated in the gate capacitance of the switching element 112 is drawn to the reference potential line 42 through the first resistor element 21. Therefore, the resistance value of the first resistor element 21 can adjust the speed at which the switching element 112 turns off, thereby adjusting the time rate of change (also referred to as di / dt) of the main current (drain current Id in this example) of the switching element 112. When the switching element 112 turns off, a surge voltage corresponding to the time rate of change of the main current of the switching element 112 is generated at the main terminals (source terminal and drain terminal in this example) of the switching element 112.

[0035] The first resistor element 22 is disposed in series with the second switching control unit 12 in a path between the control terminal of the switching element 112 and the high potential line 40. In this example, the first resistor element 22 is disposed between the second switching control unit 12 and the high potential line 40, but may be disposed between the connection point 92 and the second switching control unit 12. When the second switching control unit 12 is turned on, electric charge is charged from the high potential line 40 through the first resistor element 22 to the gate capacitance of the switching element 112. Therefore, the resistance value of the first resistor element 22 can adjust the turn-on speed of the switching element 112 and adjust the time rate of change (also referred to as di / dt) of the main current (drain current Id in this example) of the switching element 112. When the switching element 112-1 turns on, a reverse recovery surge voltage corresponding to the time rate of change of the main current of the switching element 112-1 is generated at the main terminals (source terminal and drain terminal in this example) of the other switching element (switching element 112-2 in this case).

[0036] As described above, increasing the resistance value of the first resistor element 21 reduces the time rate of change of the main current, thereby suppressing the surge voltage. However, increasing the resistance value of the first resistor element 21 lengthens the discharge time of the gate charge of the switching element 112, and increases the time from the start to the completion of the turn-off operation of the switching element 112 (referred to as the turn-off time in this specification). This increases the turn-off loss of the switching element 112. Note that the completion of turn-off may be the timing when the main current of the switching element 112 is completely cut off, or may be the timing when the voltage between the main terminals after the surge voltage occurs matches the voltage of the capacitor 116.

[0037] Similarly, increasing the resistance value of the first resistor element 22 reduces the time rate of change of the main current Id, thereby suppressing the reverse recovery surge voltage. However, increasing the resistance value of the first resistor element 22 lengthens the charging time of the gate charge of the switching element 112, and increases the time from the start to the completion of the turn-on operation of the switching element 112 (referred to as the turn-on time in this specification). This increases the turn-on loss of the switching element 112. Note that the completion of turn-on may be the timing when the main current of the switching element 112 becomes equal to the current flowing through the load, or the timing when the voltage between the main terminals becomes zero.

[0038] Furthermore, decreasing the resistance value of the first resistor element 21 shortens the turn-off time of the switching element 112, thereby reducing turn-off loss. However, this increases the surge voltage. Also, decreasing the resistance value of the first resistor element 22 shortens the turn-off time of the switching element 112, thereby reducing turn-on loss. However, this increases the reverse recovery surge voltage.

[0039] In recent years, the operating frequencies of semiconductor devices have been increasing, and it is desirable for the switching element 112 to also be able to operate at high speed. To operate the switching element 112 at high speed, it is desirable to simultaneously suppress the surge voltage and reduce the turn-off time and turn-off loss. Similarly, to operate the switching element 112 at high speed, it is desirable to simultaneously suppress the surge voltage and reduce the turn-on time and turn-on loss.

[0040] The power supply circuit 200 includes a first capacitor 50 provided in parallel with the first resistor element 21 in a path from the control terminal of the switching element 112 to the reference potential line 42. The first capacitor 50 in this example is provided in parallel with the first resistor element 21 between the reference potential line 42 and a connection point 93 of the first switching control unit 11 and the first resistor element 21.

[0041] By providing the first capacitor 50, immediately after the first switching control unit 11 is turned on, the gate charge of the switching element 112 moves to the first capacitor 50 via the first switching control unit 11. In this case, the gate charge does not pass through the first resistance element 21. Therefore, the gate voltage of the switching element 112 drops quickly. This allows the turn-off time of the switching element 112 to be shortened.

[0042] After a sufficient amount of charge has accumulated in the first capacitor 50, the gate charge of the switching element 112 moves to the reference potential line 42 mainly through the first switching control unit 11 and the first resistor element 21. Therefore, the time rate of change of the main current can be adjusted by the first resistor element 21, and the surge voltage can be suppressed.

[0043] In this way, by providing the first capacitor 50, it is possible to shorten the turn-off time of the switching element 112 and suppress the surge voltage. Similarly, by providing the second capacitor in parallel with the first resistor element 22, it is possible to shorten the turn-on time of the switching element 112 and suppress the surge voltage.

[0044] However, when the switching element 112 is repeatedly turned on and off, if the charge accumulated in the first capacitor 50 at the previous turn-off is not fully discharged by the time of the next turn-off, a sufficient gate charge cannot be transferred to the first capacitor 50 at the next turn-off. In this case, the turn-off time cannot be shortened. The same applies to the second capacitor during the turn-on operation.

[0045] In this example, the first resistor element 21 also serves as a discharge circuit for the first capacitor 50. Therefore, the charge stored in the first capacitor 50 is discharged through the first resistor element 21. Therefore, if the resistance value of the first resistor element 21 is increased to suppress surge voltages, the discharge of the stored charge in the first capacitor 50 becomes slower, and the stored charge may not be fully discharged before the next turn-off. Particularly when the switching element 112 operates at high speed, the first capacitor 50 may not be fully discharged in time. Reducing the resistance value of the first resistor element 21 shortens the discharge time of the first capacitor 50, but it becomes more difficult to suppress surge voltages. Similarly, if a second capacitor is provided in parallel with the first resistor element 22, the first resistor element 22 also serves as a discharge circuit for the second capacitor. Therefore, if the resistance value of the first resistor element 22 is increased to suppress surge voltages, the discharge of the second capacitor becomes slower, and the second capacitor may not be fully discharged before the next turn-on. In particular, when the switching element 112 operates at high speed, the second capacitor may not be able to discharge in time. If the resistance value of the first resistor element 22 is reduced, the discharge time of the second capacitor will be shortened, but it will become more difficult to suppress the surge voltage.

[0046] FIG. 2 is a diagram showing an example configuration of the power supply circuit 100. The power supply circuit 100 includes drivers 110-1 and 110-2 instead of the drivers 210-1 and 210-2 shown in FIG. 1. The configuration other than the driver 110 is the same as that of the power supply circuit 200 shown in FIG. 1. The driver 110-2 has the same function and configuration as the driver 110-1. In this example, the structure and operation of the driver 110-1 will be described, and a description of the driver 110-2 will be omitted. In this specification, the driver 110-1 may also be simply referred to as the driver 110.

[0047] The driving device 110 drives a switching element 112. The driving device 110 has a high-potential side circuit 130 and a reference potential side circuit 140. Like the driving device 210, the driving device 110 has a first power supply 31, a second power supply 32, a first switching control unit 11, a second switching control unit 12, a first resistor element 21, a first resistor element 22, and a first capacitor 50. Of these components, the first power supply 31, the first switching control unit 11, the first resistor element 21, and the first capacitor 50 are included in the reference potential side circuit 140. The first switching control unit 11 is an example of a reference potential side switching control unit, and the first capacitor 50 is an example of a reference potential side capacitor. The second power supply 32, the second switching control unit 12, and the first resistor element 22 are included in the high-potential side circuit 130. The second switching control unit 12 is an example of a high-potential side switching control unit. 2, the first resistor element 21 is arranged between the connection point 92 and the first switching control unit 11, and the first resistor element 22 is arranged between the connection point 92 and the second switching control unit 12. In another example, the first resistor element 21 may be arranged between the first switching control unit 11 and the reference potential line 42. Furthermore, the first resistor element 22 may be arranged between the second switching control unit 12 and the high potential line 40.

[0048] The first capacitor 50 is provided in parallel with the first resistor element 21 on a path from the control terminal of the switching element 112 to the reference potential line 42. In this example, the first capacitor 50 is arranged in parallel with the first resistor element 21 between the control terminal of the switching element 112 and the first switching control unit 11 (or a connection point 93). The connection point 93 is a connection point between the first resistor element 21 and the first switching control unit 11.

[0049] The reference potential side circuit 140 further includes a first discharge control unit 52 that controls whether or not to discharge the first capacitor 50. The first discharge control unit 52 is an example of a reference potential side discharge control unit. The first discharge control unit 52 is provided separately from the first switching control unit 11. The first discharge control unit 52 in this example is a first transistor that switches whether or not the electrode of the first capacitor 50 on the switching element 112 side is connected to the reference potential line 42. The first transistor is an example of a reference potential side transistor. When the first switching control unit 11 is in the on state and the first discharge control unit 52 is in the on state, both ends of the first capacitor 50 are connected to the reference potential line 42. This causes the first capacitor 50 to discharge without passing through the first resistor element 21. The on resistances of the first switching control unit 11 and the first discharge control unit 52 are sufficiently smaller than that of the first resistor element 21.

[0050] The first discharge control unit 52 is turned on after the first switching control unit 11 is turned on. As a result, for a predetermined period after the first switching control unit 11 is turned on, the gate charge of the switching element 112 moves to the first capacitor 50, and the gate voltage of the switching element 112 quickly drops. This shortens the turn-off time of the switching element 112. When the first discharge control unit 52 is turned on, the accumulated charge of the first capacitor 50 is discharged without passing through the first resistor element 21. This allows the accumulated charge of the first capacitor 50 to be quickly discharged, and the first capacitor 50 can be sufficiently discharged even when the switching element 112 operates at high speed. Furthermore, by adjusting the resistance value of the first resistor element 21, surge voltage can be suppressed.

[0051] The control circuit 114 may control the on / off state of the first discharge control unit 52. The control circuit 114 may control the first discharge control unit 52 based on the timing at which the first switching control unit 11 is turned on. For example, the control circuit 114 may turn on the first discharge control unit 52 a predetermined time after the first switching control unit 11 is turned on. The control circuit 114 may also control the first discharge control unit 52 based on the state of any of the drive device 110-1, the drive device 110-2, the switching element 112-1, and the switching element 112-2. The state of each device and element may be the instantaneous value or time waveform of the voltage or current at a predetermined position on the circuit.

[0052] The reference potential side circuit 140 may further include a first diode 54. The first diode 54 is an example of a reference potential side diode. The first diode 54 is arranged in parallel with the first resistor element 21 between the control terminal of the switching element 112 and the first capacitor 50. The first diode 54 is arranged such that the direction from the switching element 112 to the first capacitor 50 is the forward direction. Providing the first diode 54 prevents the accumulated charge in the first capacitor 50 from being discharged via the first resistor element 21. The first discharge control unit 52 of this example is arranged between the reference potential line 42 and a connection point 95 of the first diode 54 and the first capacitor 50.

[0053] 3 is a diagram showing an example of operation when switching element 112-1 and reference potential side circuit 140 are turned off. In FIG. 3, the horizontal axis represents time, and the vertical axis represents the magnitude of voltage or current. The gate voltage (gate-source voltage) of switching element 112 is Vgs, the gate current is Ig, the voltage between the main terminals is Vds, the main current is Id, and the voltage of first capacitor 50 is Vc.

[0054] In the initial state of FIG. 3, the switching element 112 is in the ON state. At timing t1, the first switching control unit 11 transitions from the OFF state to the ON state. This causes the gate current Ig to flow, and the gate charge of the switching element 112 moves to the first capacitor 50. The gate voltage Vgs quickly decreases, and the capacitor voltage Vc increases. In FIG. 3, the gate current Ig flowing into the control terminal of the switching element 112 is positive, and the gate current flowing out of the control terminal is negative. The gate charge moves to the first capacitor 50 until timing t2, when the gate voltage Vgs decreases to the plateau voltage of the switching element 112. The plateau voltage will be described later. The first capacitor 50 may have a capacity capable of transferring and storing the gate charge so that the gate voltage Vgs of the switching element 112 matches the plateau voltage, or may have a capacity capable of transferring and storing the gate charge until the gate voltage Vgs of the switching element 112 reaches at least the plateau voltage.

[0055] After the gate voltage Vgs drops to the plateau voltage (after t2), the gate charge of the switching element 112 flows to the reference potential line 42 through the first resistor element 21 and the first switching control unit 11. The gate current Ig becomes relatively small due to the resistance value of the first resistor element 21. Furthermore, since the switching element 112 starts to turn off, the voltage Vds between the main terminals gradually increases.

[0056] After a predetermined period of time has passed since the gate voltage Vgs decreased to the plateau voltage, the gate voltage Vgs begins to become smaller than the plateau voltage (timing t3). For example, when the charge of the feedback capacitance Crss (or the gate-drain capacitance Cgd) of the switching element 112 finishes discharging, the gate voltage Vgs begins to decrease. The length of the period t2-t3 may be zero. The time rate of change (di / dt) of the main current Id, which affects the magnitude of the surge voltage, is determined by the magnitude of the gate current Ig during the period t2-t3. In this example, the gate current Ig during this period can be adjusted by the first resistor element 21, thereby suppressing the surge voltage.

[0057] In the example of FIG. 2, the first discharge control unit 52 discharges the first capacitor 50 at a predetermined timing t4 after timing t3. In the example of FIG. 3, the first discharge control unit 52 is turned on when the gate voltage Vgs becomes equal to or lower than a first threshold voltage. The first threshold voltage is lower than the plateau voltage. This allows the capacitor voltage Vc of the first capacitor 50 to decrease quickly, allowing the first capacitor 50 to be sufficiently discharged even when the switching element 112 operates at high speed. Furthermore, the gate current Ig of the switching element 112 also flows through the first discharge control unit 52 to the reference potential line 42. This allows the gate voltage Vgs to also decrease quickly. Note that turning on the first discharge control unit 52 at timing t4 increases the gate current Ig, but this does not affect the magnitude of the surge voltage generated at timing t3.

[0058] As described above, according to the embodiment shown in FIGS. 2 and 3, it is possible to provide a driving device 110 that can suppress the surge voltage of the switching element 112 and shorten the turn-off time, and that can also accommodate an increase in the operating frequency of the switching element 112.

[0059] The plateau voltage may be a voltage that satisfies one or more of the following conditions (1) to (3). (1) The gate-source voltage Vgs in the region between the inflection points on the gate charge-Vgs characteristic curve of the switching element 112. (2) The gate voltage Vgs during the period in which the drain-source voltage Vds changes without changing the main current Id during the switching operation of the switching element. (3) The gate voltage Vgs during the discharge of the feedback capacitance Crss (or gate-drain capacitance Cgd) in the MOSFET If a specification value for the plateau voltage is set by the manufacturer of the switching element 112, that specification value may be used.

[0060] In addition, the first threshold voltage may be a voltage defined by any of the following (4)-(6), and if a specification value for the threshold voltage is set by the manufacturer of the switching element 112, that specification value may be used. (4) Gate voltage Vgs when the main current Id is 0. The case where the main current Id is 0 includes a case where the main current Id is substantially 0, such as when the main current is below the measurement resolution of the measuring instrument. (5) Gate voltage Vgs when a main current Id that is 0.1% of the rated current of the switching element 112 flows. The value of the main current Id used here is not limited to 0.1% of the rated current, and may be sufficiently smaller than the rated current, such as 1% or less. (6) Gate voltage Vgs when the main current Id flowing through the switching element 112 is equal to the off-state leakage current. "Equal to the off-state leakage current" includes cases where the difference is substantially equal, such as when the difference is equal to or less than the measurement resolution of the measuring instrument.

[0061] After timing t4, the first discharge control unit 52 is turned on, and the control terminal of the switching element 112 and the reference potential line 42 are equivalently short-circuited. As a result, the gate-source voltage Vgs of the switching element 112 is fixed to a reverse bias voltage, preventing the switching element 112 from being erroneously turned on. Therefore, the first discharge control unit 52 also functions as an active Miller clamp circuit that prevents the switching element 112 from being erroneously turned on.

[0062] Therefore, the discharge of the first capacitor 50 should be completed at the latest by the start of the next turn-on of the switching element. As long as it is before the next turn-on of the switching element, the first capacitor 50 may be discharged during the dead time period of the pair of switching elements 112-1 and 112-2 that operate complementarily. The dead time period refers to the period during which both switching elements 112 are in the off state (or are controlled to be in the off state).

[0063] It should be noted that by turning on the first discharge control section 52 when the gate voltage of the switching element becomes less than the first threshold voltage, the first discharge control section 52 can also function as an active Miller clamp circuit.

[0064] The control circuit 114 may control the first discharge control unit 52 based on at least one of the gate voltage Vgs, the gate current Ig, the main terminal voltage Vds, and the main current Id. The control circuit 114 may estimate the timing t3 at which the gate voltage Vgs begins to become smaller than the plateau voltage based on at least one of these. For example, the control circuit 114 may detect the timing at which the main terminal voltage Vds reaches its peak as t3, or may detect the timing at which the main current Id begins to decrease from its steady value as t3. The control circuit 114 may control the first discharge control unit 52 to the on state at a predetermined timing after timing t3.

[0065] FIG. 4 is a diagram illustrating another example of the configuration of the reference potential side circuit 140. In addition to the configuration of the reference potential side circuit 140 described in FIG. 2, the reference potential side circuit 140 of this example further includes a second resistor element 24 on the reference potential side. The second resistor element 24 is arranged in series with the first diode 54 between a connection point 95 of the first capacitor 50 and the first discharge control unit 52 and the control terminal of the switching element 112. In the example of FIG. 4, the second resistor element 24 is arranged between the first diode 54 and the connection point 95. However, in other examples, the second resistor element 24 may be arranged between the first diode 54 and the control terminal of the switching element 112. By arranging the second resistor element 24 in this manner, the discharge rate of the first capacitor 50 is not reduced and the current flowing through the first diode 54 can be kept within the limit value of the first diode 54.

[0066] By providing the second resistor element 24, it is possible to adjust the current flowing through the first diode 54. For example, by providing the second resistor element 24, it is possible to prevent a current exceeding the rated current from flowing through the first diode 54. Note that, in order to shorten the turn-off time, it is preferable that the resistance value of the second resistor element 24 is smaller than the resistance value of the first resistor element 21.

[0067] Moreover, by adjusting the resistance value of the second resistor element 24, it is possible to adjust the current flowing from the control terminal of the switching element 112 to the first capacitor 50. This makes it possible to adjust the time rate of change of the main terminal voltage Vds. Furthermore, by adjusting the resistance value of the first resistor element 21, it is possible to adjust the current flowing from the control terminal of the switching element 112 to the reference potential line 42 through the first resistor element 21 and the first switching control unit 11. This makes it possible to adjust the time rate of change of the main current Id. That is, in this example, by separately adjusting the first resistor element 21 and the second resistor element 24, it is possible to individually adjust the time rate of change of the main terminal voltage Vds and the time rate of change of the main current Id. This makes it possible to increase the switching speed without increasing the surge voltage, and reduce switching loss.

[0068] FIG. 5 is a diagram illustrating another example of the configuration of the reference potential side circuit 140. The reference potential side circuit 140 of this example further includes a third resistor element 26 on the reference potential side in addition to the configuration of any of the reference potential side circuits 140 described with reference to FIGS. 2 to 4. The reference potential side circuit 140 may also include a second resistor element 24, as shown in FIG. 4. The third resistor element 26 is arranged in series with the first discharge control unit 52 between the connection point 95 and the reference potential line 42. In the example of FIG. 5, the third resistor element 26 is arranged between the first discharge control unit 52 and the connection point 95. However, in other examples, the third resistor element 26 may be arranged between the first discharge control unit 52 and the reference potential line 42. In this way, by providing the third resistor element 26, the current flowing through the first discharge control unit 52 can be kept within the limit value of the first discharge control unit 52 without increasing the turn-off time.

[0069] By providing the third resistor element 26, it is possible to adjust the current flowing through the first discharge control unit 52. For example, by providing the third resistor element 26, it is possible to prevent a current exceeding the rated current from flowing through the first discharge control unit 52. Note that, in order to shorten the turn-off time, it is preferable that the resistance value of the third resistor element 26 is smaller than the resistance value of the first resistor element 21.

[0070] FIG. 6 is a diagram illustrating another example of the configuration of the reference potential side circuit 140. In addition to the configuration of any of the reference potential side circuits 140 described with reference to FIGS. 2 to 5, the reference potential side circuit 140 further includes a fourth resistor element 28 on the reference potential side. As shown in FIGS. 4 and 5, the reference potential side circuit 140 may include at least one of the second resistor element 24 and the third resistor element 26. The fourth resistor element 28 is arranged in series with the first capacitor 50 between the junction 93 and the junction 95. In the example of FIG. 6, the fourth resistor element 28 is arranged between the junction 93 and the first capacitor 50. However, in other examples, the fourth resistor element 28 may be arranged between the junction 95 and the first capacitor 50. By arranging the fourth resistor element 28 in this manner, the current flowing through the first capacitor 50 can be kept within the limit value of the first capacitor 50 without reducing the effectiveness of the Miller clamp circuit included in the first discharge control unit 52.

[0071] By providing the fourth resistor element 28, it is possible to adjust the current flowing through the first capacitor 50. For example, by providing the fourth resistor element 28, it is possible to prevent a current exceeding the rated current from flowing through the first capacitor 50 or the first diode 54. Note that, in order to shorten the turn-off time, it is preferable that the resistance value of the fourth resistor element 28 is smaller than the resistance value of the first resistor element 21.

[0072] Furthermore, by adjusting the resistance value of the fourth resistor element 28, it is possible to adjust the current flowing from the control terminal of the switching element 112 to the first capacitor 50. This makes it possible to adjust the time rate of change of the main terminal voltage Vds. Furthermore, by adjusting the resistance value of the first resistor element 21, it is possible to adjust the current flowing from the control terminal of the switching element 112 to the reference potential line 42 through the first resistor element 21 and the first switching control unit 11. This makes it possible to adjust the time rate of change of the main current Id. That is, in this example, by separately adjusting the first resistor element 21 and the fourth resistor element 28, it is possible to individually adjust the time rate of change of the main terminal voltage Vds and the time rate of change of the main current Id. This makes it possible to increase the switching speed without increasing the surge voltage, and reduce switching loss.

[0073] 7 is a diagram showing another example of the configuration of the reference potential side circuit 140. In the reference potential side circuit 140 of this example, the capacitance of the first capacitor 50 is variable in the configuration of any of the reference potential side circuits 140 described with reference to FIGS. 2 to 6. The driving device 110 may also include a capacitance control unit 124 that controls the capacitance of the first capacitor 50. The configuration other than the first capacitor 50 and the capacitance control unit 124 is the same as any of the examples described with reference to FIGS. 2 to 6.

[0074] 3 approaches 0. This can advance the timing t3 at which the gate voltage Vgs becomes smaller than the plateau voltage, thereby shortening the turn-off time of the switching element 112.

[0075] For example, if the capacitance of the first capacitor 50 is increased, a larger amount of gate charge can be transferred to the first capacitor 50. During the period t2-t3, the gate charge that has not been transferred to the first capacitor 50 is discharged via the first resistor element 21, and therefore, the period t2-t3 can be shortened by increasing the capacitance of the first capacitor 50. However, if the capacitance of the first capacitor 50 is made too large, a large gate current Ig flows even after the main terminal voltage Vds has risen, resulting in a large surge voltage.

[0076] The capacitance control unit 124 may adjust the capacitance of the first capacitor 50 within a range that does not increase the surge voltage. The capacitance control unit 124 may adjust the capacitance of the first capacitor 50 using circuit operation information (such as the gate voltage Vgs, the gate current Ig, the voltage between the main terminals Vds, the main current Id, and the capacitor voltage Vc) and control information for the element to be driven (such as the on-time and off-time of the element to be driven, and a signal input from the control circuit 114 to the drive device 110). Alternatively, the capacitance of the first capacitor 50 may be adjusted so that the period t2-t3 is shortened.

[0077] 8 is a diagram showing another example of the configuration of the reference potential side circuit 140. In the reference potential side circuit 140 of this example, the resistance value of the second resistor element 24 is variable in the configuration of the reference potential side circuit 140 shown in FIG. 4. The driving device 110 may also include a resistance control unit 126 that controls the resistance value of the second resistor element 24. The configuration other than the second resistor element 24 and the resistance control unit 126 is the same as the example described in FIG. 4.

[0078] According to this example, it is possible to adjust the current flowing through the first diode 54. Furthermore, by adjusting the resistance value of the second resistor element 24, it is possible to adjust the current flowing from the control terminal of the switching element 112 to the first capacitor 50 and the current flowing from the control terminal of the switching element 112 to the reference potential line 42 via the first discharge control unit 52. The resistance control unit 126 may adjust the resistance value of the second resistor element 24 so that the current flowing through the first diode 54 is within a limit value.

[0079] 9 is a diagram showing another example of the configuration of the reference potential side circuit 140. In the reference potential side circuit 140 of this example, the resistance value of the third resistor element 26 is variable in the configuration of the reference potential side circuit 140 shown in FIG. 5. The driving device 110 may also include a resistance control unit 126 that controls the resistance value of the third resistor element 26. The configuration other than the third resistor element 26 and the resistance control unit 126 is the same as the example described in FIG. 5.

[0080] According to this example, it is possible to adjust the current flowing through the first discharge control unit 52. Furthermore, by adjusting the resistance value of the third resistance element 26, it is possible to adjust the current flowing from the first capacitor 50 to the reference potential line 42 and the current flowing from the switching element 112 to the reference potential line 42 via the third resistance element 26. The resistance control unit 126 may adjust the resistance value of the third resistance element 26 so that the current flowing through the first diode 54 is within a limit value.

[0081] 10 is a diagram showing another example of the configuration of the reference potential side circuit 140. In the reference potential side circuit 140 of this example, the resistance value of the fourth resistor element 28 is variable in the configuration of the reference potential side circuit 140 shown in FIG. 6. In addition, the driving device 110 may include a resistance control unit 126 that controls the resistance value of the fourth resistor element 28. The configuration other than the fourth resistor element 28 and the resistance control unit 126 is the same as the example described in FIG. 6.

[0082] According to this example, it is possible to adjust the current flowing through the first capacitor 50. Furthermore, by adjusting the resistance value of the fourth resistor element 28, it is possible to adjust the current flowing from the control terminal of the switching element 112 to the first capacitor 50 and the current flowing from the first capacitor 50 to the reference potential line 42. The resistance control unit 126 may adjust the resistance value of the fourth resistor element 28 so that the current flowing through the first diode 54 is within a limit value.

[0083] 8 to 10 may control the resistance of one or more of the second resistor element 24, the third resistor element 26, and the fourth resistor element 28. The resistance control unit 126 may also control the resistance value of the first resistor element 21. In this case, the slope of the gate voltage Vgs during the period t3-t4 shown in FIG. 3 can be adjusted.

[0084] 11 is a diagram showing another example of the configuration of the reference potential side circuit 140. In addition to the configuration of the reference potential side circuit 240 shown in FIG. 1, the reference potential side circuit 140 of this example further includes a first discharge control unit 52. The first discharge control unit 52 of this example also controls whether or not to discharge the first capacitor 50. The timing at which the first discharge control unit 52 discharges the first capacitor 50 is the same as the examples described with reference to FIGS. 2 to 10.

[0085] The first discharge control unit 52 in this example is provided in parallel with the first capacitor 50. The first discharge control unit 52 in this example is a transistor that controls whether or not both electrodes of the first capacitor 50 are connected. However, the configuration of the first discharge control unit 52 is not limited to this. The first discharge control unit 52 only needs to be able to discharge the first capacitor 50 at any timing independent of the first switching control unit 11. This example also makes it possible to suppress surge voltage, shorten the turn-off time, and quickly discharge the first capacitor 50.

[0086] 12 is a diagram showing another example of the configuration of the reference potential side circuit 140. The reference potential side circuit 140 of this example is the same as any of the reference potential side circuits 140 described with reference to FIGS. 2 to 10, except that the first diode 54 is a Zener diode. The structure other than the first diode 54 is the same as any of the examples described with reference to FIGS. 2 to 10. According to this example, it is possible to suppress fluctuations in the gate voltage Vgs in the negative direction while the switching element 112 is turned off.

[0087] When the switching element 112-1 is turned off and the other switching element 112-2 is switched on or off, the gate voltage Vgs of the switching element 112-1 may fluctuate in the positive or negative direction. If the gate voltage Vgs fluctuates in the negative direction, dielectric breakdown may occur between the gate and source. Furthermore, if the gate voltage Vgs fluctuates in the positive direction, the switching element 112-1 may erroneously transition to the on state, resulting in a short-circuit state in which both the switching elements 112-1 and 112-2 are on.

[0088] 2 and other figures, the first discharge control unit 52 functions as an active Miller clamp circuit, which prevents the switching element 112-1 from erroneously transitioning to the on state. Furthermore, by using a Zener diode as the first diode 54, it is possible to prevent the gate voltage Vgs from fluctuating in the negative direction.

[0089] FIG. 13 shows an equivalent circuit of the reference potential side circuit 140 and switching element 112-1 shown in FIG. 12. FIG. 13 also shows capacitances Cgd, Cds, and Cgs between the terminals of the switching element 112-1. FIG. 13 also shows an equivalent circuit when the switching element 112 transitions to the off state and enters a steady state. The first switching control unit 11 and the first discharge control unit 52 are both in the on state. In this case, the first capacitor 50 is in a short-circuited state with both electrodes connected, and is therefore not taken into account in the equivalent circuit of FIG. 13. In the steady state, the gate voltage Vgs of the capacitance Cgs is approximately equal to the voltage Vg generated by the first power supply 31.

[0090] In this state, when the other switching element 112-2 is switched and the gate voltage Vgs rises in the negative direction, a voltage Vgs-Vg corresponding to the fluctuation is applied to the first diode 54. Note that a similar voltage Vgs-Vg is also applied to the first resistor element 21.

[0091] When the voltage Vgs-Vg exceeds the breakdown voltage of the first diode 54, the first diode 54 turns on, and the first power supply 31 and the capacitance Cgs are connected in parallel. At this time, the voltage applied to the first resistor element 21 drops to 0 V. Note that the breakdown voltage of the first diode 54 is preferably designed so that the gate voltage Vgs does not exceed the gate-source breakdown voltage.

[0092] Since the first power supply 31 and the capacitance Cgs are connected in parallel, the gate voltage Vgs becomes equal to the voltage Vg, which makes it possible to prevent the gate voltage Vgs from rising too much in the negative direction.

[0093] Fig. 14 is a diagram showing an example of the configuration of a power supply circuit 100 according to an embodiment of the present invention. The drive device 110 of this example differs from the example shown in Fig. 2 in the configurations of the reference potential side circuit 140 and the high potential side circuit 130. While the drive device 110 shown in Fig. 2 is intended to shorten the turn-off time, the drive device 110 of this example is intended to shorten the turn-on time.

[0094] The reference potential side circuit 140 of this example includes a first power supply 31, a first switching control unit 11, and a first resistor element 21. The functions of each component are the same as those in FIG. 2. However, the driving device 110 may include any of the reference potential side circuits 140 described with reference to FIGS. 2 to 13. In this case, the driving device 110 can achieve both a shorter turn-off time and a shorter turn-on time.

[0095] 2, the high-potential-side circuit 130 of this example includes a second capacitor 60 and a second discharge control unit 62. The second capacitor 60 is an example of a high-potential-side capacitor, and the second discharge control unit 62 is an example of a high-potential-side discharge control unit. The second capacitor 60 is provided in parallel with the first resistor element 22 in a path from the control terminal of the switching element 112 to the high-potential line 40. The second capacitor 60 of this example is arranged in parallel with the first resistor element 22 between the control terminal of the switching element 112 and the second switching control unit 12 (or a connection point 94). The connection point 94 is a connection point between the first resistor element 22 and the second switching control unit 12.

[0096] The second discharge control unit 62 is provided separately from the second switching control unit 12. In this example, the second discharge control unit 62 is a high-side switch that connects or disconnects the electrode of the second capacitor 60 on the side of the switching element 112 to the high-potential line 40. The high-side switch may be a transistor element, a photocoupler, a digital isolator, a mechanical relay, a photodiode, or another switching element. These elements connect or disconnect the electrode of the second capacitor 60 on the side of the switching element 112 to the high-potential line 40 in response to an input control signal. The use of an isolation transmission element such as a photocoupler allows the above-mentioned electrical isolation to be achieved with a simple design and a small circuit scale. The transistor element may be a semiconductor element formed on a silicon substrate or a semiconductor element formed on a compound semiconductor substrate such as GaN. The first discharge control unit 52 may also have a structure similar to that described for the second discharge control unit 62. When the second switching control unit 12 and the second discharge control unit 62 are both on, both ends of the second capacitor 60 are connected to the high-potential line 40. As a result, the second capacitor 60 is discharged without passing through the first resistor element 22. The on-resistance of the second switching control unit 12 and the second discharge control unit 62 is sufficiently smaller than that of the first resistor element 22.

[0097] The second discharge control unit 62 is turned on after the second switching control unit 12 is turned on. As a result, for a predetermined period after the second switching control unit 12 is turned on, the gate charge of the switching element 112 is supplied via the second capacitor 60, and the gate voltage rises quickly. This shortens the turn-on time of the switching element 112. When the second discharge control unit 62 is turned on, the accumulated charge of the second capacitor 60 is discharged without passing through the first resistor element 22. This allows the accumulated charge of the second capacitor 60 to be quickly discharged, and the second capacitor 60 can be sufficiently discharged even when the switching element 112 operates at high speed. Furthermore, by adjusting the resistance value of the first resistor element 22, surge voltages can be suppressed.

[0098] The control circuit 114 may control the on / off state of the second discharge control unit 62. The control circuit 114 may control the second discharge control unit 62 based on the timing at which the second switching control unit 12 is turned on. For example, the control circuit 114 may turn the second discharge control unit 62 on after a predetermined time has elapsed since the second switching control unit 12 was turned on. The control circuit 114 may also control the second discharge control unit 62 based on the state of any of the drive device 110-1, the drive device 110-2, the switching element 112-1, and the switching element 112-2. The state of each device and element may be the instantaneous value or time waveform of the voltage or current at a predetermined position on the circuit.

[0099] The high-potential side circuit 130 may further include a second diode 64. The second diode 64 is an example of a high-potential side diode. The second diode 64 is arranged in parallel with the first resistor element 22 between the control terminal of the switching element 112 and the second capacitor 60. The second diode 64 is arranged such that the direction from the switching element 112 toward the second capacitor 60 is the reverse blocking direction. Providing the second diode 64 prevents the accumulated charge in the second capacitor 60 from being discharged via the first resistor element 22. The second discharge control unit 62 in this example is arranged between the high-potential line 40 and a connection point 96 of the second diode 64 and the second capacitor 60.

[0100] FIG. 15 is a diagram showing an example of the turn-on operation of switching element 112-1 and high-potential side circuit 130. The horizontal axis in FIG. 15 indicates time, and the vertical axis indicates the magnitude of voltage or current. The gate voltage (gate-source voltage) of switching element 112-1 is Vgs, the gate current is Ig, the voltage between the main terminals is Vds, the main current is Id, and the second capacitor voltage is Vc'. In FIG. 15, the freewheeling current If flowing through the freewheeling diode of switching element 112-2 and the anode-cathode voltage V of the freewheeling diode are shown. AK 15 also shows the waveforms of the embodiment shown in FIG.

[0101] In the initial state of FIG. 15, the switching element 112-1 is in the off state. At timing t7, the second switching control unit 12 transitions from the off state to the on state. This causes the gate current Ig to flow and supply charge to the gate of the switching element 112-1 via the second capacitor 60. The gate voltage Vgs rises quickly, and the second capacitor voltage Vc' also rises. In FIG. 15, the gate current Ig flowing into the control terminal of the switching element 112-1 is assumed to be positive, and the gate current flowing out of the control terminal is assumed to be negative. Charge is supplied to the control terminal of the switching element 112-1 via the second capacitor 60 until the gate voltage Vgs reaches the threshold voltage Vth of the switching element 112-1. The threshold voltage Vth may be the same as the first threshold voltage described above. The second capacitor 60 may have a capacity capable of supplying gate charge so that the gate voltage Vgs of the switching element 112-1 matches the threshold voltage Vth, or may have a capacity capable of supplying gate charge until the gate voltage Vgs of the switching element 112-1 becomes at least the threshold voltage Vth.

[0102] After the gate voltage Vgs rises to the threshold voltage Vth (after t8 in FIG. 15), the gate current Ig flows from the high potential line 40 to the switching element 112-1 via the first resistor element 22 and the second switching control unit 12. The gate current Ig becomes relatively small due to the resistance value of the first resistor element 22. Furthermore, as the switching element 112-1 begins to turn on, the main current Id flowing through the drain terminal gradually increases.

[0103] According to this example, during the period from when the gate voltage Vgs rises to the threshold voltage Vth until it reaches the plateau voltage (t8 to t9 in FIG. 15), that is, during the period when the time rate of change (di / dt) of the main current Id, which affects the magnitude of the surge voltage, is determined by the gate current Ig, the gate current Ig can be adjusted by the first resistance element 22, and therefore the surge voltage can be adjusted.

[0104] Furthermore, when the switching element 112-1 is turned on and the main current Id increases, the return current If flowing through the switching element 112-2 decreases. The larger the time change di / dt of the main current Id flowing through the switching element 112-1, the larger the time change of the return current If, and the reverse recovery surge voltage V AK(peak) In this example, since the gate current flows through the first resistor element 22 after the period t8, the time change di / dt of the main current Id can be prevented from becoming too large. AK(peak) Furthermore, before period t8, the gate current flows through the second capacitor 60, not through the first resistor element 22, so that the gate voltage Vgs of the switching element 112-1 can be quickly raised to the threshold voltage Vth. This makes it possible to reduce turn-on loss and suppress reverse recovery surges at the same time.

[0105] In the examples of FIGS. 14 and 15 , the second discharge control unit 62 discharges the second capacitor 60 at timing t9 or at a predetermined timing t10 ​​after timing t9. In the example of FIG. 15 , the second discharge control unit 62 turns on and discharges the second capacitor 60 when the gate voltage Vgs reaches or exceeds the plateau voltage. The second discharge control unit 62 may turn on when the gate voltage Vgs reaches the plateau voltage, or may turn on after the gate voltage Vgs reaches the plateau voltage. This allows the capacitor voltage Vc′ of the second capacitor 60 to quickly decrease, thereby enabling the second capacitor 60 to be sufficiently discharged even when the switching element 112 operates at high speed, as in the previous examples. Furthermore, the gate current Ig of the switching element 112 also flows from the high-potential line 40 through the second discharge control unit 62 toward the control terminal. This allows the gate voltage Vgs to be quickly increased. When the second discharge control unit 62 is turned on at timing t10, the gate current Ig increases, but this does not affect the magnitude of the reverse recovery surge voltage occurring at timing t9.

[0106] As described above, according to the embodiment shown in FIGS. 14 and 15, similarly to the embodiment shown in FIGS. 2 and 3, it is possible to provide a driving device 110 that can suppress the reverse recovery surge voltage of the switching element 112 and shorten the turn-on time, and that can also accommodate an increase in the operating frequency of the switching element 112.

[0107] 14 and 15, the discharge of the second capacitor 60 may be completed at the latest by the start of the next turn-on of the switching element 112. The second discharge control unit 62 may discharge the second capacitor 60 between the completion of turn-on of the switching element 112 and the start of the next turn-off of the switching element 112. The second discharge control unit 62 may also discharge the second capacitor 60 during the dead time period of the pair of switching elements 112-1 and 112-2 that perform complementarily operating.

[0108] The control circuit 114 may control the second discharge control unit 62 based on at least one of the gate voltage Vgs, the gate current Ig, the voltage Vds between the main terminals, and the main current Id. The control circuit 114 may estimate, based on at least one of these, the timing t9 at which the gate voltage Vgs begins to exceed the plateau voltage. For example, the control circuit 114 may detect as t9 the timing at which the voltage Vds between the main terminals of one of the pair of complementary switching elements 112-1 and 112-2 performing reverse recovery (e.g., when 112-2 performs a turn-on operation, 112-1 performs a reverse recovery operation) reaches a peak, or may detect as t9 the timing at which the main current Id reaches a steady value. The control circuit 114 may control the second discharge control unit 62 to the on state at a predetermined timing after timing t9.

[0109] FIG. 16 is a diagram illustrating another exemplary configuration of the high-potential side circuit 130. In addition to the configuration of the high-potential side circuit 130 described in FIG. 14 , the high-potential side circuit 130 of this example further includes a second resistor element 74 on the high-potential side. The second resistor element 74 is arranged in series with the second diode 64 between a connection point 96 of the second capacitor 60 and the second discharge control unit 62 and the control terminal of the switching element 112. In the example of FIG. 16 , the second resistor element 74 is arranged between the second diode 64 and the connection point 96. However, in other examples, the second resistor element 74 may be arranged between the second diode 64 and the control terminal of the switching element 112. By arranging the second resistor element 74 in this manner, the discharge rate of the second capacitor 60 is not reduced, and the current flowing through the second diode 64 can be kept within the limit value of the second diode 64.

[0110] By providing the second resistor element 74, it is possible to adjust the current flowing through the second diode 64. For example, by providing the second resistor element 74, it is possible to prevent a current exceeding the rated current from flowing through the second diode 64. Note that, in order to shorten the turn-off time, it is preferable that the resistance value of the second resistor element 74 is smaller than the resistance value of the first resistor element 22.

[0111] FIG. 17 is a diagram showing another example of the configuration of the high-potential-side circuit 130. In addition to the configuration of any of the high-potential-side circuits 130 described with reference to FIGS. 14 to 16, the high-potential-side circuit 130 further includes a third resistor element 76 on the high-potential side. As shown in FIG. 16, the high-potential-side circuit 130 may also include a second resistor element 74. The third resistor element 76 is arranged in series with the second discharge control unit 62 between the connection point 96 and the high-potential line 40. In the example shown in FIG. 17, the third resistor element 76 is arranged between the second discharge control unit 62 and the connection point 96. However, in other examples, the third resistor element 76 may be arranged between the second discharge control unit 62 and the high-potential line 40. In this way, by providing the third resistor element 76, the current flowing through the second discharge control unit 62 can be kept within the limit value of the second discharge control unit 62 without increasing the turn-on time.

[0112] By providing the third resistor element 76, it is possible to adjust the current flowing through the second discharge control unit 62. For example, by providing the third resistor element 76, it is possible to prevent a current exceeding the rated current from flowing through the second discharge control unit 62. Note that, in order to shorten the turn-on time, it is preferable that the resistance value of the third resistor element 76 is smaller than the resistance value of the first resistor element 22.

[0113] Furthermore, by adjusting the resistance value of the third resistor element 76, it is possible to adjust the current flowing from the high potential line 40 to the control terminal of the switching element 112 via the second discharge control unit 62. This makes it possible to adjust the time rate of change of the main terminal voltage Vds. Furthermore, by adjusting the resistance value of the first resistor element 22, it is possible to adjust the current flowing from the high potential line 40 to the control terminal of the switching element 112 via the first resistor element 22 and the second switching control unit 12. This makes it possible to adjust the time rate of change of the main current Id. In other words, in this example, by separately adjusting the first resistor element 22 and the third resistor element 76, it is possible to individually adjust the time rate of change of the main terminal voltage Vds and the time rate of change of the main current Id. This makes it possible to increase the switching speed without increasing the surge voltage, thereby reducing switching loss.

[0114] FIG. 18 is a diagram showing another example of the configuration of the high-potential-side circuit 130. In addition to the configuration of any of the high-potential-side circuits 130 described with reference to FIGS. 14 to 17, the high-potential-side circuit 130 further includes a fourth high-potential-side resistor element 78. As shown in FIGS. 16 and 17, the high-potential-side circuit 130 may include at least one of the second resistor element 74 and the third resistor element 76. The fourth resistor element 78 is arranged in series with the second capacitor 60 between the junction 94 and the junction 96. In the example shown in FIG. 18, the fourth resistor element 78 is arranged between the junction 94 and the second capacitor 60. However, in other examples, the fourth resistor element 78 may be arranged between the junction 96 and the second capacitor 60. By arranging the fourth resistor element 78 in this manner, the current flowing through the second capacitor 60 can be kept within the limit value of the second capacitor 60 without reducing the effect of shortening the turn-off time achieved by the second discharge control unit 62.

[0115] By providing the fourth resistor element 78, it is possible to adjust the current flowing through the second capacitor 60. For example, by providing the fourth resistor element 78, it is possible to prevent a current exceeding the rated current from flowing through the second capacitor 60 or the second diode 64. Note that, in order to shorten the turn-on time, it is preferable that the resistance value of the fourth resistor element 78 is smaller than the resistance value of the first resistor element 22.

[0116] Furthermore, by adjusting the resistance value of the fourth resistor element 78, the current flowing from the control terminal of the switching element 112 to the second capacitor 60 can be adjusted. This makes it possible to adjust the time rate of change of the main terminal voltage Vds. Furthermore, by adjusting the resistance value of the first resistor element 22, the current flowing from the high potential line 40 through the first resistor element 22 and the second switching control unit 12 to the control terminal of the switching element 112 can be adjusted. This makes it possible to adjust the time rate of change of the main current Id. That is, in this example, by separately adjusting the first resistor element 22 and the fourth resistor element 78, it is possible to individually adjust the time rate of change of the main terminal voltage Vds and the time rate of change of the main current Id. This makes it possible to increase the switching speed without increasing the surge voltage, and reduce switching loss.

[0117] 19 is a diagram showing another example of the configuration of the high potential side circuit 130. In the high potential side circuit 130 of this example, the capacitance of the second capacitor 60 is variable in the configuration of any of the high potential side circuits 130 described with reference to FIGS. 14 to 18. The driving device 110 may also include a capacitance control unit 124 that controls the capacitance of the second capacitor 60. The configuration other than the second capacitor 60 and the capacitance control unit 124 is the same as any of the examples described with reference to FIGS. 14 to 18.

[0118] 15 approaches 0. This can advance the timing t8 at which the gate voltage Vgs reaches the threshold voltage Vth, thereby shortening the turn-on time of the switching element 112.

[0119] For example, if the capacitance of the second capacitor 60 is increased, a larger amount of gate charge can be transferred to the control terminal of the switching element 112 via the second capacitor 60. During the period t7-t8, the control terminal of the switching element 112 is charged via the second capacitor 60, and therefore the period t7-t8 can be shortened by increasing the capacitance of the second capacitor 60. However, if the capacitance of the second capacitor 60 is made too large, a large gate current Ig will flow even after the gate voltage Vgs becomes larger than the threshold voltage Vth, resulting in a large reverse recovery surge voltage.

[0120] The capacitance control unit 124 may adjust the capacitance of the second capacitor 60 within a range that does not increase the reverse recovery surge voltage. The capacitance control unit 124 may adjust the capacitance of the second capacitor 60 using circuit operation information (gate voltage Vgs, gate current Ig, main terminal voltage Vds, main current Id, second capacitor voltage Vc', etc.) and control information of the driven element (on time and off time of the driven element, signal input from the control circuit 114 to the drive device 110, etc.). Alternatively, the capacitance of the second capacitor 60 may be adjusted so that the period t7-t8 is shortened.

[0121] 20 is a diagram showing another example of the configuration of the high potential side circuit 130. In the high potential side circuit 130 of this example, the resistance value of the second resistor element 74 is variable in the configuration of the high potential side circuit 130 shown in FIG. 16. In addition, the driving device 110 may include a resistance control unit 126 that controls the resistance value of the second resistor element 74. The configuration other than the second resistor element 74 and the resistance control unit 126 is the same as the example described in FIG. 16.

[0122] According to this example, it is possible to adjust the current flowing through the second diode 64. Furthermore, by adjusting the resistance value of the second resistor element 74, it is possible to adjust the current flowing from the control terminal of the switching element 112 to the second capacitor 60 and the current flowing from the high potential line 40 to the control terminal of the switching element 112 via the second discharge control unit 62. The resistance control unit 126 may adjust the resistance value of the second resistor element 74 so that the current flowing through the second diode 64 is within a limit value.

[0123] 21 is a diagram showing another example of the configuration of the high potential side circuit 130. In the high potential side circuit 130 of this example, the resistance value of the third resistor element 76 is variable in the configuration of the high potential side circuit 130 shown in FIG. 17. The driving device 110 may also include a resistance control unit 126 that controls the resistance value of the third resistor element 76. The configuration other than the third resistor element 76 and the resistance control unit 126 is the same as the example described in FIG. 17.

[0124] According to this example, it is possible to adjust the current flowing through the second discharge control unit 62. Furthermore, by adjusting the resistance value of the third resistor element 76, it is possible to adjust the current flowing from the high potential line 40 to the second capacitor 60 and the current flowing from the third resistor element 76 to the control terminal of the switching element 112. The resistance control unit 126 may adjust the resistance value of the third resistor element 76 so that the current flowing through the second diode 64 is within a limit value.

[0125] 22 is a diagram showing another example of the configuration of the high potential side circuit 130. In the high potential side circuit 130 of this example, the resistance value of the fourth resistor element 78 is variable in the configuration of the high potential side circuit 130 shown in FIG. 18. In addition, the driving device 110 may include a resistance control unit 126 that controls the resistance value of the fourth resistor element 78. The configuration other than the fourth resistor element 78 and the resistance control unit 126 is the same as the example described in FIG. 18.

[0126] According to this example, it is possible to adjust the current flowing through the second capacitor 60. Furthermore, by adjusting the resistance value of the fourth resistor element 78, it is possible to adjust the current flowing from the second capacitor 60 to the high potential line 40 and the current flowing from the second capacitor 60 to the control terminal of the switching element 112. The resistance control unit 126 may adjust the resistance value of the fourth resistor element 78 so that the current flowing through the second diode 64 is within a limit value.

[0127] 20 to 22 may control the resistance of one or more of the second resistor element 74, the third resistor element 76, and the fourth resistor element 78. The resistance control unit 126 may also control the resistance value of the first resistor element 22. In this case, the slope of the gate voltage Vgs during the period t8-t9 shown in FIG. 15 can be adjusted.

[0128] 23 is a diagram showing another example of the configuration of the high-potential-side circuit 130. In addition to the configuration of the high-potential-side circuit 230 shown in FIG. 1, the high-potential-side circuit 130 of this example further includes a second capacitor 60 and a second discharge control unit 62. The second capacitor 60 of this example is provided in parallel with the first resistor element 22 between the connection point 94 and the high-potential line 40. The second discharge control unit 62 of this example also controls whether or not to discharge the second capacitor 60. The timing at which the second discharge control unit 62 discharges the second capacitor 60 is the same as the examples described with reference to FIGS. 14 to 22.

[0129] The second discharge control unit 62 in this example is provided in parallel with the second capacitor 60. The second discharge control unit 62 in this example is a transistor that controls whether or not both electrodes of the second capacitor 60 are connected. However, the configuration of the second discharge control unit 62 is not limited to this. The second discharge control unit 62 only needs to be able to discharge the second capacitor 60 at any timing independent of the second switching control unit 12. This example also makes it possible to suppress reverse recovery surge voltage, shorten the turn-on time, and quickly discharge the second capacitor 60.

[0130] The driving device 110 may be configured by appropriately combining any one of the reference potential side circuits 140 shown in Figures 2 to 12 and any one of the high potential side circuits 130 shown in Figures 14 to 23. In this case, the driving device 110 can shorten the turn-off time and turn-on time without increasing the surge voltage or reverse recovery surge voltage.

[0131] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention. [Explanation of symbols]

[0132] REFERENCE SIGNS LIST 11 first switching control section, 12 second switching control section, 21 first resistor element, 22 first resistor element, 24 second resistor element, 26 third resistor element, 28 fourth resistor element, 31 first power supply, 32 second power supply, 40 high potential line, 42 reference potential line, 50 first capacitor, 52 first discharge control section, 54 first diode, 60 second capacitor, 62 second discharge control section, 64 second diode, 74 second resistor element, 76 third Resistance element, 78... fourth resistance element, 91, 92, 93, 94, 95, 96, 118... connection point, 100... power supply circuit, 110, 210... drive device, 112... switching element, 114... control circuit, 116... capacitor, 120... high potential line, 122... reference potential line, 124... capacitance control section, 126... resistance control section, 130... high potential side circuit, 140... reference potential side circuit, 230... high potential side circuit, 240... reference potential side circuit, 200... power supply circuit

Claims

1. A driving device for driving a switching element, A high-voltage line, a high potential side switching control unit that switches whether or not a control terminal of the switching element is connected to the high potential line; a first resistor element on a high potential side arranged in series with the high potential side switching control unit in a path from the control terminal of the switching element to the high potential line; a high-potential side capacitor provided in parallel with the first resistor element in a path from the control terminal of the switching element to the high-potential line; a high potential side discharge control unit that controls whether or not the high potential side capacitor is discharged; Equipped with the high potential side switching control unit is provided between one electrode of the high potential side capacitor and the high potential line, The high potential side discharge control unit is provided in parallel with the high potential side switching control unit, and is provided between the other electrode of the high potential side capacitor and the high potential line. Drive unit.

2. A driving device for driving a switching element, A high-voltage line, a high potential side switching control unit that switches whether or not a control terminal of the switching element is connected to the high potential line; a first resistor element on a high potential side arranged in series with the high potential side switching control unit in a path from the control terminal of the switching element to the high potential line; a high-potential side capacitor provided in parallel with the first resistor element in a path from the control terminal of the switching element to the high-potential line; a high potential side discharge control unit that controls whether or not the high potential side capacitor is discharged; Equipped with the first resistor element is provided between the high potential line and the high potential side switching control unit, the high potential side discharge control unit is connected in parallel with the first resistance element; Drive unit.

3. A driving device for driving a switching element, A high-voltage line, a high potential side switching control unit that switches whether or not a control terminal of the switching element is connected to the high potential line; a first resistor element on a high potential side arranged in series with the high potential side switching control unit in a path from the control terminal of the switching element to the high potential line; a high-potential side capacitor provided in parallel with the first resistor element in a path from the control terminal of the switching element to the high-potential line; a high potential side discharge control unit that controls whether or not the high potential side capacitor is discharged; Equipped with the first resistor element is disposed between the control terminal of the switching element and the high potential side switching control unit, the high potential side capacitor is arranged in parallel with the first resistance element between the control terminal of the switching element and the high potential side switching control unit, a high-potential-side diode arranged in parallel with the first resistor element between the control terminal of the switching element and the high-potential-side capacitor; Drive unit.

4. The high potential side discharge control unit discharges the high potential side capacitor on the condition that the control voltage at the control terminal of the switching element is equal to or higher than a plateau voltage. A drive device according to any one of claims 1 to 3.

5. the switching element is one of a pair of switching elements that operate complementarily, The high potential side discharge control unit discharges the high potential side capacitor during the period from the completion of turn-on of the switching element to be driven to the start of the next turn-off. A drive device according to any one of claims 1 to 3.

6. the first resistor element is disposed between the control terminal of the switching element and the high potential side switching control unit, The high-potential side capacitor is arranged in parallel with the first resistance element between the control terminal of the switching element and the high-potential side switching control unit. The drive device according to claim 1 .

7. a high-potential-side diode arranged in parallel with the first resistor element between the control terminal of the switching element and the high-potential-side capacitor; The drive device according to claim 6.

8. The high-potential-side discharge control unit is a high-potential-side switch disposed between the high-potential line and a connection point between the high-potential-side diode and the high-potential-side capacitor.

8. The drive device according to claim 3 or 7.

9. a second high-side resistor element disposed in series with the high-side diode between the connection point of the high-side capacitor and the high-side switch and the control terminal of the switching element; The drive device according to claim 8.

10. a third high-potential-side resistor element disposed in series with the high-potential-side switch between the high-potential line and a connection point between the high-potential-side capacitor and the high-potential-side switch; 10. The drive device according to claim 8 or 9.

11. a fourth high-side resistor element disposed in series with the high-side capacitor between a connection point of the high-side switching control unit and the first resistor element and a connection point of the high-side diode and the high-side switch. A drive device according to any one of claims 8 to 10.

12. The capacitance of the high potential side capacitor is variable, a capacitance control unit that controls the capacitance of the high-potential side capacitor A drive arrangement according to any one of claims 1 to 11.

13. the resistance value of the second resistor element is variable, a resistance control unit that controls the resistance value of the second resistance element The drive device according to claim 9.

14. the resistance value of the third resistor element is variable, a resistance control unit that controls the resistance value of the third resistance element The drive device according to claim 10.

15. the resistance value of the fourth resistor element is variable, a resistance control unit that controls the resistance value of the fourth resistance element The drive device according to claim 11.

16. a reference potential line having a lower potential than the high potential line; a reference potential side switching control unit that switches whether or not a control terminal of the switching element is connected to the reference potential line; a first resistor element on the reference potential side that is arranged in series with the reference potential side switching control unit in a path from the control terminal of the switching element to the reference potential line; a reference potential side capacitor provided in parallel with the first resistor element on the reference potential side in a path from the control terminal of the switching element to the reference potential line; a reference potential side discharge control unit that controls whether or not the reference potential side capacitor is discharged; The drive arrangement of claim 1 , further comprising:

17. At least one of the switching element and the high-potential side discharge control unit is a wide band gap semiconductor element whose main material is at least one of silicon carbide, gallium nitride, gallium oxide, and diamond.

17. A drive arrangement according to any one of claims 1 to 16.

18. 18. The driving device according to claim 1, wherein the high-potential-side discharge control unit is any one of a transistor element, a photocoupler, a digital isolator, a mechanical relay, and a photodiode.

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