drive device

Abstract

The present application preferably enables high-speed operation of a switching element. A drive device for driving a switching element includes a high-potential line, a high-potential-side switching control section that switches whether or not a control terminal of the switching element is connected to the high-potential line, a first resistance element on the high-potential side that is arranged in series with the high-potential-side switching control section in a path from the control terminal of the switching element to the high-potential line, a high-potential-side capacitor that is arranged in parallel with 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 section that controls whether or not the high-potential-side capacitor is discharged.

Description

Technical Field

[0001] This invention relates to a drive device for driving switching elements. Background Technology

[0002] Previously, drive devices for controlling switching elements such as transistors were known (for example, see Patent Document 1). Patent Document 1: Japanese Patent Application Publication No. 2000-324801 Summary of the Invention The technical problem that the invention aims to solve

[0003] In the drive device, it is preferable to be able to handle the high-speed operation of the switching element. Technical means for solving technical problems

[0004] To address the aforementioned problems, in one aspect of the present invention, a driving device for driving a switching element is provided. The driving device may include a high-potential line. The driving device may include a high-potential side switching control unit that switches whether a control terminal of the switching element is connected to the high-potential line. The driving device may include a first high-potential side resistor element configured in series with the high-potential side switching control unit in the path from the control terminal of the switching element to the high-potential line. The driving device may include a high-potential side capacitor configured in parallel with the first resistor element in the path from the control terminal of the switching element to the high-potential line. The driving device may include a high-potential side discharge control unit that controls whether the high-potential side capacitor is discharged.

[0005] The high-potential side discharge control unit can discharge the high-potential side capacitor when the control voltage at the control terminal of the switching element is above the step voltage.

[0006] The switching element can be any element in a pair of complementary switching elements. The high-potential side discharge control unit can discharge the high-potential side capacitor during the period from the completion of the turn-on of the switching element being driven to the start of the next turn-off.

[0007] The first resistive element can be disposed between the control terminal of the switching element and the high-potential side switching control unit. The high-potential side capacitor can be disposed in parallel with the first resistive element between the control terminal of the switching element and the high-potential side switching control unit.

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

[0009] The high-potential side discharge control unit can be a high-potential side switch configured between the connection point of the high-potential side diode and the high-potential side capacitor and the high-potential line.

[0010] The driving device may include a second high-potential-side resistor element configured in series with a high-potential-side diode between the connection point of the high-potential-side capacitor and the high-potential-side switch and the control terminal of the switching element.

[0011] The driving device may include a third resistive element on the high-potential side, which is connected in series with the high-potential side switch between the connection point of the high-potential side capacitor and the high-potential side switch and the high-potential line.

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

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

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

[0015] The resistance value of the third resistive element can be variable. The driving device may include a resistance control unit that controls the resistance value of the third resistive element.

[0016] The resistance value of the fourth resistive element can be variable. The driving device may include a resistance control unit that controls the resistance value of the fourth resistive element.

[0017] The driving device may include a reference potential line with a potential lower than the high potential line. The driving device may include a reference potential side switching control unit that switches whether the control terminal of the switching element is connected to the reference potential line. The driving device may include a first resistor element on the reference potential side, configured in series with the reference potential side switching control unit in the path from the control terminal of the switching element to the reference potential line. The driving device may include a reference potential side capacitor configured in parallel with the first resistor element on the reference potential side in the path from the control terminal of the switching element to the reference potential line. The driving device may include a reference potential side discharge control unit that controls whether the reference potential side capacitor is discharged.

[0018] At least one of the switching element and the high-potential side switch can be a wide-bandgap semiconductor element with at least one of silicon carbide, gallium nitride, gallium oxide and diamond as the main material.

[0019] The high-potential side switch can be any of a transistor element, optocoupler, digital isolator, mechanical relay, and photodiode. Attached Figure Description

[0020] Figure 1This is a diagram illustrating an example of the power supply circuit 200 involved in the reference example. Figure 2 This is a diagram showing an example of the structure of the power supply circuit 100. Figure 3 This is a diagram showing an example of the operation of the switching element 112-1 and the reference potential side circuit 140 when they are turned off. Figure 4 This is a diagram showing other structural examples of the reference potential side circuit 140. Figure 5 This is a diagram showing other structural examples of the reference potential side circuit 140. Figure 6 This is a diagram showing other structural examples of the reference potential side circuit 140. Figure 7 This is a diagram showing other structural examples of the reference potential side circuit 140. Figure 8 This is a diagram showing other structural examples of the reference potential side circuit 140. Figure 9 This is a diagram showing other structural examples of the reference potential side circuit 140. Figure 10 This is a diagram showing other structural examples of the reference potential side circuit 140. Figure 11 This is a diagram showing other structural examples of the reference potential side circuit 140. Figure 12 This is a diagram showing other structural examples of the reference potential side circuit 140. Figure 13 Show Figure 12 The equivalent circuit of the reference potential side circuit 140 and the switching element 112-1 shown. Figure 14 This is a diagram illustrating a structural example of a power supply circuit 100 according to an embodiment of the present invention. Figure 15 This is a diagram illustrating an example of the operation of the switching element 112-1 and the high-potential side circuit 130. Figure 16 This is a diagram showing other structural examples of the high-potential side circuit 130. Figure 17 This is a diagram showing other structural examples of the high-potential side circuit 130. Figure 18 This is a diagram showing other structural examples of the high-potential side circuit 130. Figure 19 This is a diagram showing other structural examples of the high-potential side circuit 130. Figure 20 This is a diagram showing other structural examples of the high-potential side circuit 130. Figure 21This is a diagram showing other structural examples of the high-potential side circuit 130. Figure 22 This is a diagram showing other structural examples of the high-potential side circuit 130. Figure 23 This is a diagram showing other structural examples of the high-potential side circuit 130. Detailed Implementation

[0021] The present invention will now be described through embodiments thereof; however, these embodiments do not limit the scope of the invention as defined in the claims. Furthermore, the combinations of features described in the embodiments are not necessarily all necessary technical means to solve the technical problems of the present invention. Additionally, in this specification and the accompanying drawings, elements having substantially the same function or structure are labeled with the same reference numerals, thereby omitting redundant descriptions. Furthermore, elements not directly related to the present invention are omitted from the illustrations. Moreover, in one drawing, elements having the same function or structure are sometimes represented by reference numerals, while reference numerals are sometimes omitted for other elements.

[0022] This specification may also include cases referred to as "same" or "equal," where there are errors caused by manufacturing deviations, etc. This error is, for example, within 10%. Furthermore, in cases referred to as "same" or "equal," the values ​​may be close due to cost considerations. A close value is, for example, "taking 3.1Ω as 3.3Ω," a value derived from an E-sequence value from a non-sequence value.

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

[0024] As an example, switching elements 112-1 and 112-2 are transistors such as MOSFETs, but are not limited to these. Each switching element 112 may have a drain terminal, a source terminal, and a gate terminal. In the case where the switching element 112 is an insulated-gate bipolar transistor (IGBT) or the like, the drain terminal and source terminal are also referred to as the collector terminal and emitter terminal. The gate terminal is an example of a control terminal used to control the on / off state of the switching element 112.

[0025] In this example, switching elements 112-1 and 112-2 are connected in series between the high-potential line 120 and the reference potential line 122. A reference potential, such as 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 can be connected to the reference potential line 122 and the high-potential line 120. Furthermore, a capacitor 116 can be connected between the reference potential line 122 and the high-potential line 120.

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

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

[0028] Drive device 210-1 controls switch element 112-1 to switch between on and off states. Drive device 210-2 controls switch element 112-2 to switch between on and off states. Drive device 210-2 can have the same function and structure as drive device 210-1. In this example, the structure and operation of drive device 210-1 are described, and the description of drive device 210-2 is omitted. In addition, in this specification, drive device 210-1 is sometimes simply referred to as drive device 210.

[0029] The drive unit 210 generates a control signal input to the gate terminal of the switching element 112. In this specification, the switching element 112-1 is sometimes simply referred to as switching element 112. The drive unit 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 resistive 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 resistive 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 configured 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. The connection point 91 of the first power supply 31 and the second power supply 32 can 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 configured in series between the high potential line 40 and the reference potential line 42 and operate complementaryly. The transistors shown in this specification and the accompanying drawings can be bipolar transistors, MOSFETs, IGBTs, wide-bandgap semiconductor devices with at least one of silicon carbide, gallium nitride, gallium oxide, and diamond as the main material, or other semiconductor switching elements. The 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 to connect the control terminal of the switching element 112 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 to connect the control terminal of the switching element 112 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 can generate control signals applied to the control terminals of the first switching control unit 11 and the second switching control unit 12.

[0034] The first resistive element 21 is connected in series with the first switching control unit 11 in the path between the control terminal of the switching element 112 and the reference potential line 42. In this example, the first resistive element 21 is disposed between the first switching control unit 11 and the reference potential line 42, but it can also 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 stored in the gate capacitance of the switching element 112 is drawn to the reference potential line 42 through the first resistive element 21. Therefore, the speed at which the switching element 112 is turned off can be adjusted by the resistance value of the first resistive element 21, and the time change rate (also called di / dt) of the main current (drain current Id in this example) of the switching element 112 can be adjusted. In addition, when the switching element 112 is turned off, the surge voltage corresponding to the time change rate of the main current of the switching element 112 is generated on the main terminals of the switching element 112 (source terminal and drain terminal in this example).

[0035] The first resistive element 22 is connected in series with the second switching control unit 12 in the path between the control terminal of the switching element 112 and the high-potential line 40. In this example, the first resistive element 22 is disposed between the second switching control unit 12 and the high-potential line 40, but it can also be disposed between the connection point 92 and the second switching control unit 12. When the second switching control unit 12 is turned on, charge is transferred from the high-potential line 40 to the gate capacitance of the switching element 112 through the first resistive element 22. Therefore, the turning speed of the switching element 112 can be adjusted by the resistance value of the first resistive element 22, and the time change rate (also called di / dt) of the main current (drain current Id in this example) of the switching element 112 can be adjusted. In addition, when the switching element 112-1 is turned on, the reverse recovery surge voltage corresponding to the time change rate of the main current of the switching element 112-1 is generated on the main terminals (source terminal and drain terminal in this example) of other switching elements (switching element 112-2 in this case).

[0036] As described above, increasing the resistance value of the first resistive element 21 reduces the time rate of change of the main current and suppresses surge voltage. However, increasing the resistance value of the first resistive element 21 lengthens the discharge time of the gate charge of the switching element 112, and increases the time from the start of the cutoff operation to its completion (referred to as the cutoff time in this specification). Therefore, the cutoff loss of the switching element 112 increases. Furthermore, the cutoff completion can be the timing of the completion of the main current interruption of the switching element 112, or it can be the timing when the voltage between the main terminals after the surge voltage is generated matches the voltage of the capacitor 116.

[0037] Similarly, increasing the resistance value of the first resistive element 22 reduces the rate of change of the main current Id over time, suppressing reverse recovery surge voltage. However, increasing the resistance value of the first resistive element 22 lengthens the charging time of the gate charge of the switching element 112, increasing the time from the start of the switching operation to its completion (referred to as the conduction time in this specification). Therefore, the conduction loss of the switching element 112 increases. Furthermore, the completion of conduction can be timed when the main current of the switching element 112 equals the current flowing through the load, or when the voltage between the main terminals is zero.

[0038] Furthermore, reducing the resistance value of the first resistive element 21 can shorten the cutoff time of the switching element 112, thereby reducing cutoff losses. However, the surge voltage will increase. Similarly, reducing the resistance value of the first resistive element 22 can shorten the cutoff time of the switching element 112, thereby reducing conduction losses. However, the reverse recovery surge voltage will increase.

[0039] In recent years, the operating frequency of semiconductor devices has increased, and the switching element 112 is preferably capable of high-speed operation. To enable the switching element 112 to operate at high speed, it is preferable to simultaneously suppress surge voltage, turn-off time, and turn-off losses. Similarly, to enable the switching element 112 to operate at high speed, it is preferable to simultaneously suppress surge voltage, turn-on time, and turn-on losses.

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

[0041] By providing the first capacitor 50, after the first switching control unit 11 is in the on state, the gate charge of the switching element 112 immediately 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 resistive element 21. Therefore, the gate voltage of the switching element 112 decreases rapidly. Thus, the off-time of the switching element 112 can be shortened.

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

[0043] Therefore, by providing the first capacitor 50, the off-time of the switching element 112 can be shortened and surge voltage can be suppressed. Similarly, by providing the second capacitor in parallel with the first resistive element 22, the on-time of the switching element 112 can be shortened and surge voltage can be suppressed.

[0044] However, when the switching element 112 is repeatedly turned on and off, if the charge stored in the first capacitor 50 at the last off time is not sufficiently discharged before the next off time, then enough gate charge cannot be moved to the first capacitor 50 at the next off time. In this case, the inability to shorten the off time also applies to the second capacitor during the on operation.

[0045] In this example, the first resistive element 21 also serves as the discharge circuit for the first capacitor 50. Therefore, the charge stored in the first capacitor 50 is discharged via the first resistive element 21. Thus, if the resistance value of the first resistive element 21 is increased to suppress surge voltage, the discharge of the stored charge in the first capacitor 50 slows down, potentially resulting in insufficient discharge of the stored charge before the next turn-off. Specifically, when the switching element 112 operates at high speed, the first capacitor 50 may not have enough time to discharge. If the resistance value of the first resistive element 21 is decreased, the discharge time of the first capacitor 50 will be shortened, but it will be difficult to suppress surge voltage. Similarly, when the second capacitor is connected in parallel with the first resistive element 22, the first resistive element 22 also serves as the discharge circuit for the second capacitor. Therefore, if the resistance value of the first resistive element 22 is increased to suppress surge voltage, the discharge of the second capacitor slows down, potentially resulting in insufficient discharge of the second capacitor before the next turn-on. In particular, when the switching element 112 operates at high speed, the second capacitor may not have enough time to discharge. If the resistance value of the first resistive element 22 is reduced, the discharge time of the second capacitor 50 will be shortened, but it will be difficult to suppress surge voltage.

[0046] Figure 2 This is a diagram showing an example of the structure of the power supply circuit 100. The power supply circuit 100 includes drive devices 110-1 and 110-2, which replace... Figure 1 The drive units 210-1 and 210-2 are shown. The structure other than drive unit 110 is similar to... Figure 1 The power supply circuit 200 shown is the same. Drive device 110-2 can have the same function and structure as drive device 110-1. In this example, the structure and operation of drive device 110-1 are described, while the description of drive device 110-2 is omitted. Furthermore, in this specification, drive device 110-1 is sometimes simply referred to as drive device 110.

[0047] The drive unit 110 drives the switching element 112. The drive unit 110 has a high-potential side circuit 130 and a reference-potential side circuit 140. The drive unit 110 is identical to the drive unit 210, including a first power supply 31, a second power supply 32, a first switching control unit 11, a second switching control unit 12, a first resistive element 21, a first resistive element 22, and a first capacitor 50. In these configurations, the first power supply 31, the first switching control unit 11, the first resistive 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. Furthermore, the second power supply 32, the second switching control unit 12, and the first resistive 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. Figure 2 In one example, the first resistive element 21 is disposed between the connection point 92 and the first switching control unit 11, and the first resistive element 22 is disposed between the connection point 92 and the second switching control unit 12. In other examples, the first resistive element 21 may be disposed between the first switching control unit 11 and the reference potential line 42. Furthermore, the first resistive element 22 may be disposed between the second switching control unit 12 and the high potential line 40.

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

[0049] The reference potential side circuit 140 also includes a first discharge control unit 52 that controls whether the first capacitor 50 is discharged. The first discharge control unit 52 is an example of a reference potential side discharge control unit. The first discharge control unit 52 is separate from the first switching control unit 11. In this example, the first discharge control unit 52 is a first transistor that switches whether the electrode on the switching element 112 side of the first capacitor 50 is connected to the reference potential line 42. The first transistor is an example of a reference potential side transistor. If the first switching control unit 11 is in the on state and the first discharge control unit 52 is in the on state, the two 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 resistive element 21. Furthermore, the on-resistance of the first switching control unit 11 and the first discharge control unit 52 is sufficiently small compared to the first resistive element 21.

[0050] The first discharge control unit 52 enters the conducting state after a timing period following the first switching control unit 11 being in the conducting state. Consequently, during a predetermined period after the first switching control unit 11 is in the conducting state, the gate charge of the switching element 112 moves to the first capacitor 50, and the gate voltage of the switching element 112 rapidly decreases. Therefore, the off-time of the switching element 112 can be shortened. Then, the first discharge control unit 52 enters the conducting state, thereby discharging the stored charge of the first capacitor 50 without passing through the first resistor element 21. This allows the stored charge of the first capacitor 50 to be discharged rapidly, and even when the switching element 112 operates at high speed, the first capacitor 50 can be sufficiently discharged. Furthermore, by adjusting the resistance value of the first resistor element 21, surge voltage can be suppressed.

[0051] The control circuit 114 can control the on / off state of the first discharge control unit 52. The control circuit 114 can control the first discharge control unit 52 based on a timing that puts the first switching control unit 11 into the on state. For example, the first discharge control unit 52 can be put into the on state after a predetermined time has elapsed after the first switching control unit 11 is put into the on state. Furthermore, the control circuit 114 can also control the first discharge control unit 52 based on any state of the drive device 110-1, drive device 110-2, switching element 112-1, and switching element 112-2. The state of each device and element can be an instantaneous value or time waveform of voltage or current at a predetermined location 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 connected in parallel with the first resistive element 21 between the control terminal of the switching element 112 and the first capacitor 50. The first transistor 54 is configured such that the direction from the switching element 112 to the first capacitor 50 is positive. By providing the first diode 54, the stored charge in the first capacitor 50 can be prevented from discharging via the first resistive element 21. In this example, the first discharge control unit 52 is disposed between the connection point 95 of the first diode 54 and the first capacitor 50 and the reference potential line 42.

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

[0054] exist Figure 3 In the initial state, 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. As a result, the gate current Ig flows, and the gate charge of the switching element 112 moves to the first capacitor 50. The gate voltage Vgs drops rapidly, and the capacitor voltage Vc rises. Figure 3In this configuration, the gate current Ig flowing into the control terminal of the switching element 112 is set to positive, and the gate current flowing out of the control terminal is set to negative. Gate charge moves to the first capacitor 50 until the gate voltage Vgs drops to the step voltage of the switching element 112 at a timing t2. The step voltage will be described later. To make the gate voltage Vgs of the switching element 112 match the step voltage, the first capacitor 50 may have a capacitance for storing gate charge by moving it, or it may have a capacitance capable of moving and storing gate charge until the gate voltage Vgs of the switching element 112 at least becomes the step voltage.

[0055] After the gate voltage Vgs drops to the step 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. Due to the resistance value of the first resistor element 21, the gate current Ig decreases relatively. In addition, since the switching element 112 begins to turn off, the voltage Vds between the main terminals gradually increases.

[0056] If the gate voltage Vgs drops to the step voltage and a specified period passes, the gate voltage Vgs will begin to be less than the step voltage (timing t3). For example, the gate voltage Vgs begins to decrease when the charge release of the feedback capacitor Crss (or the gate-drain capacitance Cgd) of the switching element 112 ends. The length of the time period t2-t3 can also be 0. The rate of change of the main current Id (di / dt) that affects the magnitude of the surge voltage is determined by the magnitude of the gate current Ig before the time period t2-t3. In this example, the surge voltage can be suppressed because the gate current Ig during this period can be adjusted by the first resistive element 21.

[0057] exist Figure 2 In one embodiment, at a predetermined time t4 after time t3, the first discharge control unit 52 discharges the first capacitor 50. Figure 3 In the example, the first discharge control unit 52 enters the conducting state when the gate voltage Vgs is below the first threshold voltage. The first threshold voltage is smaller than the step voltage. Therefore, since the capacitor voltage Vc of the first capacitor 50 decreases rapidly, the first capacitor 50 can be fully discharged even when the switching element 112 operates at high speed. Furthermore, the gate current Ig of the switching element 112 also flows to the reference potential line 42 through the first discharge control unit 52. Therefore, the gate voltage Vgs also decreases rapidly. Additionally, when the first discharge control unit 52 is turned on at time t4, the gate current Ig increases, but this does not affect the magnitude of the surge voltage generated at time t3.

[0058] As mentioned above, according to Figure 2 and Figure 3The embodiment shown can both suppress surge voltage of the switching element 112 and shorten the cutoff time, and provides a drive device 110 that can cope with even an increase in the operating frequency of the switching element 112.

[0059] The so-called step voltage can be any one or more of the following conditions (1)-(3). (1) Gate-source voltage Vgs in the interval between the inflection points on the gate charge-Vgs characteristic curve of switching element 112. (2) During the switching operation of the switching element, when the main current Id does not change, the gate voltage Vgs during the period when the drain-source voltage Vds changes. (3) Gate voltage Vgs during discharge of the feedback capacitor Crss (or gate-drain capacitance Cgd) in the MOSFET. When the manufacturer of the switching element 112 or the like sets a specified value for the step voltage, that specified value can also be used.

[0060] In addition, the first threshold voltage can also be any of the voltages defined in (4)-(6) below, and the specified value can also be used when the manufacturer of the switching element 112 sets the specified value of the threshold voltage. (4) Gate voltage Vgs when the main current Id is 0. The case where the main current Id is 0 includes cases where it is actually 0, such as when the main current is less than the measurement resolution of the measuring device. (5) The gate voltage Vgs when the main current Id, which is 0.1% of the rated current of the switching element 112, passes through. The value of the main current Id used here only needs to be sufficiently small compared to the rated current, such as less than 1%, but is not limited to 0.1% of the rated current. (6) The gate voltage Vgs is equal to the leakage current during the cut-off state when the main current Id flowing to the switching element 112 is equal to the leakage current during the cut-off state. Equal to the leakage current during the cut-off state includes cases where they are basically equal, such as cases where the difference is less than or equal to the measurement resolution of the measuring instrument.

[0061] After timing t4, since the first discharge control section 52 is in the on state, the control terminal of the switching element 112 and the reference potential line 42 are effectively short-circuited. Therefore, the gate-source voltage Vgs of the switching element 112 is fixed at a reverse bias voltage, which prevents the switching element 112 from being erroneously turned on. Therefore, the first discharge control section 52 also functions as an active reflective clamping circuit to prevent the switching element 112 from being erroneously turned on.

[0062] Therefore, the first capacitor 50 should be discharged no later than the start of the next conduction of the switching element. Until the next conduction of the switching element, the first capacitor 50 can discharge during the dead time period of the pair of complementary switching elements 112-1 and 112-2. The dead time period refers to the period during which both switching elements 112 are in the off state (or controlled to be in the off state).

[0063] In addition, by turning on the first discharge control unit 52 when the gate voltage of the switching element is less than the first threshold voltage, the first discharge control unit 52 can also be used as an active reflective clamping circuit.

[0064] The control circuit 114 can control the first discharge control unit 52 based on at least one of the gate voltage Vgs, gate current Ig, inter-terminal voltage Vds, and main current Id. The control circuit 114 can estimate the timing t3 at which the gate voltage Vgs begins to fall below the step voltage based on at least one of these parameters. For example, the control circuit 114 can detect t3 as the timing when the inter-terminal voltage Vds indicates a peak value, or it can detect t3 as the timing when the main current Id begins to decrease from a stable value. The control circuit 114 can control the first discharge control unit 52 to be in the on state at a predetermined timing after t3.

[0065] Figure 4 This is a diagram illustrating other structural examples of the reference potential side circuit 140. The reference potential side circuit 140 in this example, besides... Figure 2 In addition to the structure of the reference potential side circuit 140 described herein, a second resistor element 24 on the reference potential side is also included. The second resistor element 24 and the first diode 54 are connected in series between the connection point 95 of the first capacitor 50 and the first discharge control unit 52 and the control terminal of the switching element 112. Figure 4 In this example, the second resistive element 24 is disposed between the first diode 54 and the connection point 95; however, in other examples, the second resistive element 24 may be disposed between the first diode 54 and the control terminal of the switching element 112. By distributing the second resistive element 24 in this manner, the discharge rate of the first capacitor 50 is not reduced, and the current flowing to the first diode 54 is limited within the limit value of the first diode 54.

[0066] By providing the second resistor element 24, the current flowing through the first diode 54 can be adjusted. For example, by providing the second resistor element 24, it is possible to prevent current exceeding the rated current from flowing through the first diode 54. Furthermore, to shorten the cutoff time, it is preferable that the resistance value of the second resistor element 24 is less than the resistance value of the first resistor element 21.

[0067] Furthermore, by adjusting the resistance value of the second resistor element 24, the current flowing from the control terminal of the switching element 112 to the first capacitor 50 can be adjusted. This allows for adjustment of the time-varying rate of change of the main terminal voltage Vds. Furthermore, by adjusting the resistance value of the first resistor element 21, the current flowing from the control terminal of the switching element 112 through the first resistor element 21 and the first switching control unit 11 to the reference potential line 42 can be adjusted. This allows for adjustment of the time-varying rate of change of the main current Id. In other words, in this example, by adjusting the first resistor element 21 and the second resistor element 24 individually, the time-varying rate of change of the main terminal voltage Vds and the time-varying rate of change of the main current Id can be adjusted independently. This allows for increased switching speed without increasing surge voltage and reduced switching losses.

[0068] Figure 5 This is a diagram illustrating other structural examples of the reference potential side circuit 140. The reference potential side circuit 140 in this example, besides... Figures 2 to 4 In addition to the structure of any reference potential side circuit 140 described herein, it also includes a third resistive element 26 on the reference potential side. The reference potential side circuit 140 is as follows: Figure 4 As shown, a second resistive element 24 may also be included. A third resistive element 26 is connected in series with the first discharge control unit 52 between the connection point 95 and the reference potential line 42. Figure 5 In the example, the third resistive element 26 is disposed between the first discharge control unit 52 and the connection point 95. However, in other examples, the third resistive element 26 may also be disposed between the first discharge control unit 52 and the reference potential line 42. Thus, by distributing the third resistive element 26, the current flowing to the first discharge control unit 52 can be limited within the limit value of the first discharge control unit 52 without increasing the cutoff time.

[0069] By providing the third resistor element 26, the current flowing through the first discharge control unit 52 can be adjusted. For example, by providing the third resistor element 26, it is possible to prevent current exceeding the rated current from flowing through the first discharge control unit 52. In addition, in order to shorten the cutoff time, it is preferable that the resistance value of the third resistor element 26 is less than the resistance value of the first resistor element 21.

[0070] Figure 6 This is a diagram illustrating other structural examples of the reference potential side circuit 140. The reference potential side circuit 140 in this example, besides... Figures 2 to 5 In addition to the structure of the reference potential side circuit 140 described herein, it also includes a fourth resistive element 28 on the reference potential side. The reference potential side circuit 140 is as follows... Figure 4 and Figure 5 As shown, it may include at least one of a second resistive element 24 and a third resistive element 26. A fourth resistive element 28 is configured in series with the first capacitor 50 between connection point 93 and connection point 95. Figure 6 In the example, the fourth resistor element 28 is disposed between the connection point 93 and the first capacitor 50, but in other examples, the fourth resistor element 28 may also be disposed between the connection point 95 and the first capacitor 50. Distributing the fourth resistor element 28 in this way limits the current flowing to the first capacitor 50 within a predetermined value, without diminishing the effect of the reflective clamping circuit of the first discharge control unit 52.

[0071] By providing the fourth resistor element 28, the current flowing through the first capacitor 50 can be adjusted. For example, by providing the fourth resistor element 28, it is possible to prevent an excessive current from flowing through the first capacitor 50 or the first transistor 54. In addition, to shorten the cutoff time, it is preferable that the resistance value of the fourth resistor element 28 is less than the resistance value of the first resistor element 21.

[0072] Furthermore, by adjusting the resistance value of the fourth resistor element 28, the current flowing from the control terminal of the switching element 112 to the first capacitor 50 can be adjusted. This allows adjustment of the time rate of change of the main terminal voltage Vds. Furthermore, by adjusting the resistance value of the first resistor element 21, the current flowing from the control terminal of the switching element 112 through the first resistor element 21 and the first switching control unit 11 to the reference potential line 42 can be adjusted. This allows adjustment of the time rate of change of the main current Id. That is, in this example, by adjusting the first resistor element 21 and the fourth resistor element 28 separately, the time rate of change of the main terminal voltage Vds and the time rate of change of the main current Id can be adjusted separately. This allows for increased switching speed without increasing surge voltage and reduced switching losses.

[0073] Figure 7 This is a diagram illustrating other structural examples of the reference potential side circuit 140. In this example, the reference potential side circuit 140... Figures 2 to 6 In the structure of any reference potential side circuit 140 described herein, the capacitance of the first capacitor 50 is variable. Furthermore, the drive device 110 may include a capacitance control unit 124 for controlling the capacitance of the first capacitor 50. The structure other than the first capacitor 50 and the capacitance control unit 124 is similar to... Figures 2 to 6 The same applies to any of the examples described.

[0074] The capacitor control unit 124 can adjust the capacitance of the first capacitor 50 so that... Figure 3 The period t1-t3 shown is close to 0. Therefore, the timing t3 at which the gate voltage Vgs is less than the step voltage can be advanced, which can shorten the cutoff time of the switching element 112.

[0075] For example, increasing the capacitance of the first capacitor 50 allows more gate charge to be moved to it. During the period t2-t3, since the gate charge that has not moved to the first capacitor 50 is discharged through the first resistive element 21, increasing the capacitance of the first capacitor 50 shortens the period t2-t3. However, if the capacitance of the first capacitor 50 is made too large, a large gate current Ig will flow even after the voltage Vds between the main terminals rises, thus increasing the surge voltage.

[0076] The capacitor control unit 124 can adjust the capacitance of the first capacitor 50 within a range that does not increase the surge voltage. The capacitor control unit 124 uses circuit operation information (gate voltage Vgs, gate current Ig, main terminal voltage Vds, main current Id, and capacitor voltage Vc, etc.) or control information of the driven element (on-time or off-time of the driven element, signals input from the control circuit 114 to the drive device 110, etc.) to adjust the capacitance of the first capacitor 50. Furthermore, the capacitance of the first capacitor 50 can be adjusted to reduce the time interval t2-t3.

[0077] Figure 8 This is a diagram illustrating other structural examples of the reference potential side circuit 140. In this example, the reference potential side circuit 140... Figure 4 In the structure of the reference potential side circuit 140 shown, the resistance value of the second resistive element 24 is variable. Furthermore, the drive device 110 may include a resistance control unit 126 that controls the resistance value of the second resistive element 24. The structure other than the second resistive element 24 and the resistance control unit 126 is similar to... Figure 4 The examples described are the same.

[0078] In this example, the current flowing through the first diode 54 can be adjusted. Furthermore, by adjusting the resistance value of the second resistor element 24, 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 can be adjusted. The resistor control unit 126 can 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] Figure 9 This is a diagram illustrating other structural examples of the reference potential side circuit 140. In this example, the reference potential side circuit 140... Figure 5 In the structure of the reference potential side circuit 140 shown, the resistance value of the third resistive element 26 is variable. Furthermore, the drive device 110 may include a resistance control unit 126 that controls the resistance value of the third resistive element 26. The structure other than the third resistive element 26 and the resistance control unit 126 is similar to... Figure 5 The examples described are the same.

[0080] In this example, the current flowing through the first discharge control unit 52 can be adjusted. Furthermore, by adjusting the resistance value of the third resistive element 26, 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 resistive element 26 can be adjusted. The resistance control unit 126 can adjust the resistance value of the third resistive element 26 so that the current flowing through the first diode 54 is within a limit value.

[0081] Figure 10 This is a diagram illustrating other structural examples of the reference potential side circuit 140. In this example, the reference potential side circuit 140... Figure 6 In the structure of the reference potential side circuit 140 shown, the resistance value of the fourth resistive element 28 is variable. Furthermore, the drive device 110 may include a resistance control unit 126 that controls the resistance value of the fourth resistive element 28. The structure other than the fourth resistive element 28 and the resistance control unit 126 is similar to... Figure 6 The examples described are the same.

[0082] In this example, the current flowing through the first capacitor 50 can be adjusted. Furthermore, by adjusting the resistance value of the fourth resistive element 28, 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 can be adjusted. The resistance control unit 126 can adjust the resistance value of the fourth resistive element 28 so that the current flowing through the first diode 54 is within a limit value.

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

[0084] Figure 11 This is a diagram illustrating other structural examples of the reference potential side circuit 140. The reference potential side circuit 140 in this example, besides... Figure 1 In addition to the structure of the reference potential side circuit 240 shown, a first discharge control unit 52 is also included. In this example, the first discharge control unit 52 also controls whether the first capacitor 50 is discharged. The timing of the first discharge control unit 52 discharging the first capacitor 50 is related to… Figures 2 to 10 The examples described herein are the same.

[0085] In this example, the first discharge control unit 52 is connected in parallel with the first capacitor 50. The first discharge control unit 52 in this example is a transistor that controls whether the terminals of the first capacitor 50 are connected. However, the structure of the first discharge control unit 52 is not limited to this. The first discharge control unit 52 can discharge the first capacitor 50 at any time independently of the first switching control unit 11. According to this example, it is also possible to suppress surge voltage, shorten the cutoff time, and achieve high-speed discharge of the first capacitor 50.

[0086] Figure 12 This is a diagram illustrating other structural examples of the reference potential side circuit 140. In this example, the reference potential side circuit 140... Figures 2 to 10 In the arbitrary reference potential side circuit 140 described herein, the first diode 54 is a Zener diode. The structure other than the first diode 54 is... Figures 2 to 10 The same applies to any of the examples described. According to this example, during the period when the switching element 112 is off, it is possible to suppress the gate voltage Vgs from changing in the negative direction.

[0087] When switching element 112-1 is in the off state and other switching elements 112-2 are in the on or off state, the gate voltage Vgs of switching element 112-1 may fluctuate in the positive or negative direction. If the gate voltage Vgs fluctuates in the negative direction, insulation breakdown may sometimes occur between the gate and source. Furthermore, if the gate voltage Vgs fluctuates in the positive direction, switching element 112-1 may incorrectly switch to the on state, causing a short circuit where both switching elements 112-1 and 112-2 are on.

[0088] like Figure 2 As explained above, since the first discharge control unit 52 functions as an active reflective clamping circuit, it can prevent the switching element 112-1 from erroneously switching to the on state. Furthermore, by setting the first diode 54 as a Zener diode, it can suppress negative fluctuations in the gate voltage Vgs.

[0089] Figure 13 As shown Figure 12 The equivalent circuit of the reference potential side circuit 140 and the switching element 112-1 shown. Figure 13 The capacitances Cgd, Cds, and Cgs between the terminals of the switching element 112-1 are shown in the diagram. Furthermore, Figure 13 The equivalent circuit is shown when the switching element 112 switches to the off state and is in the normal state. Both the first switching control unit 11 and the first discharge control unit 52 are in the on state. In this case, since the first capacitor 50 is in a short-circuit state with its two electrodes connected, it is not considered... Figure 13 The equivalent circuit. Under normal conditions, the gate voltage Vgs of capacitor Cgs is almost equal to the voltage Vg generated by the first power supply 31.

[0090] In this state, when other switching elements 112-2 switch on and off, and the gate voltage Vgs rises in the negative direction, the voltage Vgs-Vg corresponding to the change is applied to the first diode 54. Additionally, the first resistive element 21 is also subjected to the same voltage Vgs-Vg.

[0091] When the voltage Vgs-Vg exceeds the breakdown voltage of the first diode 54, the first diode 54 conducts, and the first power supply 31 is connected in parallel with the capacitor Cgs. At this time, the voltage applied to the first resistive element 21 drops to 0V. Furthermore, the breakdown voltage of the first diode 54 is preferably designed such that the gate voltage Vgs does not exceed the gate-source breakdown voltage.

[0092] Since the first power supply 31 is connected in parallel with the capacitor Cgs, the gate voltage Vgs is equal to the voltage Vg. This prevents the gate voltage Vgs from rising excessively in the negative direction.

[0093] Figure 14 This is a diagram illustrating an example of the structure of a power supply circuit 100 according to one embodiment of the present invention. The structure of the reference potential side circuit 140 and the high potential side circuit 130 of the drive device 110 in this example is similar to... Figure 2 The examples are different. Figure 2 The drive unit 110 shown is designed to shorten the cutoff time, while the drive unit 110 in this example is designed to shorten the turn-on time.

[0094] The reference potential side circuit 140 in this example includes a first power supply 31, a first switching control unit 11, and a first resistive element 21. The functions of the structural elements of each component are as follows: Figure 2 Same. However, the drive unit 110 may be included in Figures 2 to 13 The circuit 140 on the reference potential side is described in the diagram. In this case, the drive device 110 can simultaneously reduce the cutoff time and the on-time.

[0095] In this example, the high-potential side circuit 130, besides... Figure 2 In addition to the structure of the high-potential side circuit 130 shown, it also 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 connected in parallel with the first resistive element 22 in the path from the control terminal of the switching element 112 to the high-potential line 40. In this example, the second capacitor 60 and the first resistive element 22 are connected in parallel between the control terminal of the switching element 112 and the second switching control unit 12 (or connection point 94). Connection point 94 is the connection point between the first resistive element 22 and the second switching control unit 12.

[0096] The second discharge control unit 62 is separate from the second switching control unit 12. In this example, the second discharge control unit 62 is a high-potential side switch that switches whether the electrode on the switching element 112 side of the second capacitor 60 is connected to the high-potential line 40. The high-potential side switch can be one of a transistor element, an optocoupler, a digital isolator, a mechanical relay, or a photodiode, or other switching elements. These elements switch whether the electrode on the switching element 112 side of the second capacitor 60 is connected to the high-potential line 40 according to the input control signal. By using an insulating transmission element such as an optocoupler, the above-mentioned electrical insulation can be achieved with easy design and a small circuit size. The transistor element can be a semiconductor element formed on a silicon substrate or a semiconductor element formed on a compound semiconductor substrate such as GaN. In addition, the same structure as described in the example for the second discharge control unit 62 can also be applied to the first discharge control unit 52. When the second switching control unit 12 is in the conducting state and the second discharge control unit 62 is in the conducting state, the two ends of the second capacitor 60 are connected to the high-potential line 40. This causes the second capacitor 60 to discharge without passing through the first resistive element 22. Furthermore, the on-resistance of the second switching control unit 12 and the second discharge control unit 62 is sufficiently small compared to the first resistive element 22.

[0097] The second discharge control unit 62 enters the conducting state after a timing period following the second switching control unit 12 being in the conducting state. Thus, during a predetermined period from when the second switching control unit 12 is in the conducting state, gate charge is supplied to the switching element 112 via the second capacitor 60, causing the gate voltage to rise rapidly. Therefore, the conduction time of the switching element 112 can be shortened. Then, the second discharge control unit 62 enters the conducting state, thereby discharging the stored charge in the second capacitor 60 without passing through the first resistor element 22. Thus, the stored charge in the second capacitor 60 can be discharged rapidly, and even when the switching element 112 operates at high speed, the discharge of the second capacitor 60 can be sufficient. Furthermore, by adjusting the resistance value of the first resistor element 22, surge voltage can be suppressed.

[0098] The control circuit 114 can control the on / off state of the second discharge control unit 62. The control circuit 114 can control the second discharge control unit 62 based on a timing that puts the second switching control unit 12 into the on state. For example, the second discharge control unit 62 can be put into the on state after a predetermined time has elapsed after the second switching control unit 12 is put into the on state. Furthermore, the control circuit 114 can also control the second discharge control unit 62 based on any state of the drive device 110-1, drive device 110-2, switching element 112-1, and switching element 112-2. The state of each device and element can be an instantaneous value or time waveform of voltage or current at a predetermined location 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 connected in parallel with the first resistive element 22 between the control terminal of the switching element 112 and the second capacitor 60. The second diode 64 is configured such that the direction from the switching element 112 to the second capacitor 60 is reversed. By providing the second diode 64, the stored charge in the second capacitor 60 is prevented from discharging via the first resistive element 22. In this example, the second discharge control unit 62 is disposed between the connection point 96 of the second diode 64 and the second capacitor 60 and the high-potential line 40.

[0100] Figure 15 This is a diagram illustrating an example of the conduction operation of the switching element 112-1 and the high-potential side circuit 130. Figure 15 The horizontal axis represents time, and the vertical axis represents the magnitude of voltage or current. Furthermore, the gate voltage (gate-source voltage) of switching element 112-1 is set to Vgs, the gate current to Ig, the voltage between the main terminals to Vds, the main current to Id, and the voltage of the second capacitor to Vc'. Additionally, in... Figure 15 The diagram shows the combined return current If flowing through the return diode in switching element 112-2 and the cathode-to-cathode voltage V of the return diode. AK The waveform. In Figure 15 The middle shows Figure 14 The actions of the embodiments.

[0101] exist Figure 15 In the initial state, 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. As a result, gate current Ig flows, supplying charge to the gate of switching element 112-1 via the second capacitor 60. The gate voltage Vgs rises rapidly, and the voltage Vc of the second capacitor rises as well. Figure 15 In this configuration, the gate current Ig flowing into the control terminal of the switching element 112-1 is set to positive, and the gate current flowing out of the control terminal is set to 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 can be the same as the first threshold voltage described above. Therefore, the second capacitor 60 can be a capacitor capable of providing gate charge so that the gate voltage Vgs of the switching element 112-1 matches the threshold voltage Vth, or it can be a capacitor capable of providing gate charge until the gate voltage Vgs of the switching element 112-1 at least becomes the threshold voltage Vth.

[0102] After the gate voltage Vgs rises to the threshold voltage Vth ( Figure 15In the middle (after t8), the gate current Ig flows from the high potential line 40 to the switching element 112-1 through the first resistive element 22 and the second switching control unit 12. The gate current Ig becomes smaller due to the resistance value of the first resistive element 22. In addition, as the switching element 112-1 starts to conduct, the main current Id flowing through the drain terminal gradually increases.

[0103] In this example, during the period after the gate voltage Vgs rises to the threshold voltage Vth until the step voltage is reached ( Figure 15 In the period from t8 to t9, 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 resistor element 22, and thus the surge voltage can be adjusted.

[0104] Furthermore, when switching element 112-1 is turned on and the main current Id increases, the return current If flowing to switching element 112-2 decreases. The larger the time variation di / dt of the main current Id flowing to switching element 112-1, the larger the time variation of the return current If, and the greater the reverse recovery surge voltage V in switching element 112-2. AK(peak) The larger the value, the better. In this example, after period t8, since the gate current flows through the first resistive element 22, the time variation di / dt of the main current Id can be prevented from becoming too large. Therefore, the reverse recovery surge voltage V can be suppressed. AK(peak) Furthermore, before period t8, since the gate current flows through the second capacitor 60 instead of the first resistor element 22, the gate voltage Vgs of the switching element 112-1 can quickly reach the threshold voltage Vth. Therefore, both the reduction of conduction losses and the suppression of reverse recovery surges can be achieved.

[0105] exist Figure 14 and Figure 15 In one embodiment, at time t9 or at a predetermined time t10 after time t9, the second discharge control unit 62 discharges the second capacitor 60. Figure 15In the example, the second discharge control unit 62 is turned on when the gate voltage Vgs is above the step voltage, causing the second capacitor 60 to discharge. The second discharge control unit 62 can be turned on at the timing when the gate voltage Vgs reaches the step voltage, or it can be turned on after the timing when the gate voltage Vgs reaches the step voltage. As a result, since the capacitor voltage Vc' of the second capacitor 60 decreases rapidly, the second capacitor 60 can be fully discharged even when the switching element 112 operates at high speed, as in the embodiments up to this point. In addition, the gate current Ig of the switching element 112 also flows from the high potential line 40 to the control terminal via the second discharge control unit 62. Therefore, the gate voltage Vgs can also rise rapidly. Furthermore, 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 generated at timing t9.

[0106] As mentioned above, according to Figure 14 and Figure 15 The illustrated embodiment, and Figure 2 and Figure 3 Similar to the embodiment, it can both suppress the reverse recovery surge voltage of the switching element 112 and shorten the conduction time, thereby providing a drive device 110 that can cope even if the operating frequency of the switching element 112 is increased.

[0107] Therefore, according to Figure 14 and Figure 15 In the illustrated embodiment, the discharge of the second capacitor 60 can be completed no later than the start of the next turn-on of the switching element 112. The second discharge control unit 62 can discharge the second capacitor 60 during the period from the completion of the turn-on of the switching element 112 to the start of the next turn-off. Furthermore, the second discharge control unit 62 can also discharge the second capacitor 60 during the dead time of a pair of complementary operating switching elements 112-1 and 11-2.

[0108] The control circuit 114 can control the second discharge control unit 62 based on at least one of the gate voltage Vgs, gate current Ig, main terminal voltage Vds, and main current Id. The control circuit 114 can predict the timing t9 at which the gate voltage Vgs begins to exceed the step voltage based on at least one of these. For example, the control circuit 114 can use the timing t9 to detect the peak value of the main terminal voltage Vds of a pair of complementary switching elements 112-1 and 112-2 performing a reverse recovery operation (e.g., when 112-2 performs a conduction operation, 112-1 performs a reverse recovery operation), or it can use the timing t9 to detect when the main current Id reaches a stable value. The control circuit 114 can control the second discharge control unit 62 to be in the conducting state at a predetermined timing after timing t9.

[0109] Figure 16 This is a diagram illustrating other structural examples of the high-potential side circuit 130. In this example, the high-potential side circuit 130, besides... Figure 14 In addition to the structure of the high-potential side circuit 130 described herein, a second resistor element 74 on the high-potential side is also included. The second resistor element 74 and the second diode 64 are connected in series between the connection point 96 of the second capacitor 60 and the second discharge control unit 62 and the control terminal of the switching element 112. Figure 16 In one example, the second resistive element 74 is disposed between the second diode 64 and the connection point 96; however, in other examples, the second resistive element 74 may be disposed between the second diode 64 and the control terminal of the switching element 112. By distributing the second resistive element 74 in this way, the current flowing to the second diode 64 can be contained within the limit value of the second diode 64 without reducing the discharge rate of the second capacitor 60.

[0110] By providing the second resistor element 74, the current flowing through the second diode 64 can be adjusted. For example, by providing the second resistor element 74, it is possible to prevent current exceeding the rated current from flowing through the second diode 64. In addition, to shorten the cutoff time, it is preferable that the resistance value of the second resistor element 74 is less than the resistance value of the first resistor element 22.

[0111] Figure 17 This diagram illustrates other structural examples of the high-potential side circuit 130. In this example, the high-potential side circuit 130, besides... Figures 14 to 16 In addition to the structure of any high-potential side circuit 130 described herein, it also includes a third resistive element 76 on the high-potential side. The high-potential side circuit 130 is as follows: Figure 16 As shown, a second resistive element 74 may also be included. A third resistive element 76 is connected in series with the second discharge control unit 62 between the connection point 96 and the high-potential line 40. Figure 17 In the example, the third resistive element 76 is disposed between the second discharge control unit 62 and the connection point 96. However, in other examples, the third resistive element 76 may also be disposed between the second discharge control unit 62 and the high potential line 40. Thus, by distributing the third resistive element 76, the current flowing to the second discharge control unit 62 can be converged within the limit value of the second discharge control unit 62 without increasing the conduction time.

[0112] By providing the third resistor element 76, the current flowing through the second discharge control unit 62 can be adjusted. For example, by providing the third resistor element 76, it is possible to prevent current exceeding the rated current from flowing through the second discharge control unit 62. In addition, in order to shorten the conduction time, it is preferable that the resistance value of the third resistor element 76 is less than the resistance value of the first resistor element 22.

[0113] Furthermore, by adjusting the resistance value of the third resistor element 76, 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 can be adjusted. This allows adjustment of the time-varying 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 42 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 allows adjustment of the time-varying rate of change of the main current Id. In other words, in this example, by individually adjusting the first resistor element 22 and the third resistor element 76, the time-varying rate of change of the main terminal voltage Vds and the time-varying rate of change of the main current Id can be adjusted independently. This allows for increased switching speed without increasing surge voltage and reduced switching losses.

[0114] Figure 18 This diagram illustrates other structural examples of the high-potential side circuit 130. In this example, the high-potential side circuit 130, besides... Figures 14 to 17 In addition to the structure of the high-potential side circuit 130 described herein, it also includes a fourth resistive element 78 on the high-potential side. The high-potential side circuit 130 is as follows: Figures 16 to 17 As shown, it may include at least one of a second resistive element 74 and a third resistive element 76. A fourth resistive element 78 is configured in series with the second capacitor 60 between connection point 94 and connection point 96. Figure 18 In the example, the fourth resistor element 78 is disposed between the connection point 94 and the second capacitor 60. However, in other examples, the fourth resistor element 78 may also be disposed between the connection point 96 and the second capacitor 60. By distributing the fourth resistor element 78 in this way, the current flowing to the second capacitor 60 can be converged within the limit value of the second capacitor 60 without reducing the shortening effect of the cutoff time of the second discharge control unit 62.

[0115] By providing the fourth resistor element 78, the current flowing through the second capacitor 60 can be adjusted. For example, by providing the fourth resistor element 78, it is possible to prevent an excessive current from flowing through the second capacitor 60 or the second diode 64. In addition, to shorten the conduction time, it is preferable that the resistance value of the fourth resistor element 78 is less 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 allows for adjustment of the time-varying rate of change of the main terminal voltage Vds. Moreover, 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 allows for adjustment of the time-varying rate of change of the main current Id. In other words, in this example, by individually adjusting the first resistor element 22 and the fourth resistor element 78, the time-varying rate of change of the main terminal voltage Vds and the time-varying rate of change of the main current Id can be adjusted independently. This allows for increased switching speed without increasing surge voltage and reduced switching losses.

[0117] Figure 19 This is a diagram illustrating other structural examples of the high-potential side circuit 130. In this example, the high-potential side circuit 130... Figures 14 to 18 In the structure of any high-potential side circuit 130 described herein, the capacitance of the second capacitor 60 is variable. Furthermore, the drive device 110 may include a capacitor control unit 124 for controlling the capacitance of the second capacitor 60. The structure other than the second capacitor 60 and the capacitor control unit 124 is similar to... Figures 14 to 18 The same applies to any of the examples described.

[0118] The capacitor control unit 124 can adjust the capacitance of the second capacitor 60 so that... Figure 15 The period t7-t8 shown is close to 0. Therefore, the timing t8 at which the gate voltage Vgs reaches the threshold voltage Vth can be advanced, which can shorten the conduction time of the switching element 112.

[0119] For example, when the capacitance of the second capacitor 60 increases, more gate charge can be moved 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; 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 exceeds the threshold voltage Vth, thus increasing the reverse recovery surge voltage.

[0120] The capacitor control unit 124 can adjust the capacitance of the second capacitor 60 within a range that does not increase the reverse recovery surge voltage. The capacitor control unit 124 can 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, and second capacitor voltage Vc', etc.) or control information of the driven element (on-time or off-time of the driven element, signals input from the control circuit 114 to the drive device 110, etc.). Furthermore, the capacitance of the second capacitor 60 can be adjusted to reduce the time interval t7-t8.

[0121] Figure 20 This is a diagram illustrating other structural examples of the high-potential side circuit 130. In this example, the high-potential side circuit 130... Figure 16 In the structure of the high-potential side circuit 130 shown, the resistance value of the second resistive element 74 is variable. Furthermore, the drive device 110 may include a resistance control unit 126 that controls the resistance value of the second resistive element 74. The structure other than the second resistive element 74 and the resistance control unit 126 is similar to... Figure 16 The examples described are the same.

[0122] In this example, the current flowing through the second diode 64 can be adjusted. Furthermore, by adjusting the resistance value of the second resistive element 74, 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 can be adjusted. The resistance control unit 126 can also adjust the resistance value of the second resistive element 74 so that the current flowing through the second diode 64 is within a limit value.

[0123] Figure 21 This is a diagram illustrating other structural examples of the high-potential side circuit 130. In this example, the high-potential side circuit 130... Figure 17 In the structure of the high-potential side circuit 130 shown, the resistance value of the third resistive element 76 is variable. Furthermore, the drive device 110 may include a resistance control unit 126 that controls the resistance value of the third resistive element 76. The structure other than the third resistive element 76 and the resistance control unit 126 is similar to... Figure 17 The examples described are the same.

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

[0125] Figure 22This is a diagram illustrating other structural examples of the high-potential side circuit 130. In this example, the high-potential side circuit 130... Figure 18 In the structure of the high-potential side circuit 130 shown, the resistance value of the fourth resistive element 78 is variable. Furthermore, the drive device 110 may include a resistance control unit 126 that controls the resistance value of the fourth resistive element 78. The structure other than the fourth resistive element 78 and the resistance control unit 126 is similar to... Figure 18 The examples described are the same.

[0126] According to this example, the current flowing through the second capacitor 60 can be adjusted. Furthermore, by adjusting the resistance value of the fourth resistive element 78, 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 can be adjusted. The resistance control unit 126 can also adjust the resistance value of the fourth resistive element 78 so that the current flowing through the second diode 64 is within a limit value.

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

[0128] Figure 23 This diagram illustrates other structural examples of the high-potential side circuit 130. In this example, the high-potential side circuit 130, besides... Figure 1 In addition to the structure of the high-potential side circuit 230 shown, it also includes a second capacitor 60 and a second discharge control unit 62. In this example, the second capacitor 60 is connected in parallel with the first resistor element 22 between the connection point 94 and the high-potential line 40. In this example, the second discharge control unit 62 also controls whether the second capacitor 60 discharges. The timing of the discharge of the second capacitor 60 by the second discharge control unit 62 is... Figures 14 to 22 The examples described herein are the same.

[0129] In this example, the second discharge control unit 62 is connected in parallel with the second capacitor 60. The second discharge control unit 62 in this example is a transistor that controls whether the terminals of the second capacitor 60 are connected. However, the structure of the second discharge control unit 62 is not limited to this. The second discharge control unit 62 can discharge the second capacitor 60 at any time independently of the second switching control unit 12. According to this example, it is also possible to achieve suppression of reverse recovery surge voltage, shortening of conduction time, and high-speed discharge of the second capacitor 60.

[0130] The drive unit 110 can also be made by Figures 2 to 12The arbitrary reference potential side circuit 140 and described herein Figures 14 to 23 The high-potential side circuit 130 described herein can be appropriately combined. In this case, the drive device 110 can shorten the cutoff time and turn-on time without increasing the surge voltage or reverse recovery surge voltage.

[0131] The present invention has been described above using embodiments, but the technical scope of the present invention is not limited to the scope described in the above embodiments. Various changes or improvements can be made based on the above embodiments, which will be apparent to those skilled in the art. As will be understood from the patent claims, such changes or improvements are also included within the technical scope of the present invention. Label Explanation

[0132] 11 First switching control unit, 12 Second switching control unit, 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 unit, 54 First diode, 60 Second capacitor, 62 Second discharge control unit, 64 Second diode, 74 Second resistor element, 76 Third resistor element 78 Fourth resistor element, 91, 92, 93, 94, 95, 96, 118 connection points, 100 power supply circuit, 110, 210 drive devices, 112 switching element, 114 control circuit, 116 capacitor, 120 high potential line, 122 reference potential line, 124 capacitor control unit, 126 resistor control unit, 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, characterized in that, include: High potential line; A high-potential-side switching control unit switches whether the control terminal of the switching element is connected to the high-potential line. The first resistor element on the high potential side is configured in series with the high potential side switching control unit in the path from the control terminal of the switching element to the high potential line; A high-potential-side capacitor is provided in parallel with the first resistive element in the path from the control terminal of the switching element to the high-potential line; as well as A high-potential-side discharge control unit controls whether or not to discharge the high-potential-side capacitor. The high-potential side switching control unit is disposed between one electrode of the high-potential side capacitor and the high-potential line. The high-potential side discharge control unit is connected in parallel with the high-potential side switching control unit, and is located between the other electrode of the high-potential side capacitor and the high-potential line.

2. A driving device for driving a switching element, characterized in that, include: High potential line; A high-potential-side switching control unit switches whether the control terminal of the switching element is connected to the high-potential line. The first resistor element on the high potential side is configured in series with the high potential side switching control unit in the path from the control terminal of the switching element to the high potential line; A high-potential-side capacitor is provided in parallel with the first resistive element in the path from the control terminal of the switching element to the high-potential line; as well as A high-potential-side discharge control unit controls whether or not to discharge the high-potential-side capacitor. The first resistive element is disposed 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 resistive element.

3. A driving device for driving a switching element, characterized in that, include: High potential line; A high-potential-side switching control unit switches whether the control terminal of the switching element is connected to the high-potential line. The first resistor element on the high potential side is configured in series with the high potential side switching control unit in the path from the control terminal of the switching element to the high potential line; A high-potential-side capacitor is provided in parallel with the first resistive element in the path from the control terminal of the switching element to the high-potential line; as well as A high-potential-side discharge control unit controls whether or not to discharge the high-potential-side capacitor. The first resistive 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 configured in parallel with the first resistive element between the control terminal of the switching element and the high-potential side switching control unit. The driving device further includes a high-potential-side diode, which is configured in parallel with the first resistive element between the control terminal of the switching element and the high-potential-side capacitor.

4. The driving device as described in any one of claims 1 to 3, characterized in that, The high-potential side discharge control unit discharges the high-potential side capacitor when the control voltage at the control terminal of the switching element reaches or exceeds the step voltage.

5. The driving device as described in any one of claims 1 to 3, characterized in that, The switching element is any one of a pair of switching elements that perform complementary actions. The high-potential side discharge control unit discharges the high-potential side capacitor during the period from the completion of the conduction of the switching element that is the driving object until the start of the next cutoff.

6. The driving device as claimed in claim 1, characterized in that, The first resistive 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 connected in parallel with the first resistor element between the control terminal of the switching element and the high-potential side switching control unit.

7. The driving device as claimed in claim 6, characterized in that, Also includes: A high-potential-side diode is connected in parallel with the first resistive element between the control terminal of the switching element and the high-potential-side capacitor.

8. The driving device as described in claim 3 or 7, characterized in that, The high-potential side discharge control unit is a high-potential side switch disposed between the connection point of the high-potential side diode and the high-potential side capacitor and the high-potential line.

9. The driving device as claimed in claim 8, characterized in that, Also includes: A second resistor on the high-potential side, which is connected in series with the high-potential-side diode, is disposed between the connection point of the high-potential-side capacitor and the high-potential-side switch and the control terminal of the switching element.

10. The driving device as claimed in claim 8, characterized in that, Also includes: A third resistive element on the high-potential side is connected in series with the high-potential side switch between the connection point of the high-potential side capacitor and the high-potential side switch and the high-potential line.

11. The driving device as claimed in claim 8, characterized in that, Also includes: A fourth resistor on the high-potential side is connected in series with the high-potential side capacitor between the connection point of the high-potential side switching control unit and the first resistor and the connection point of the high-potential side diode and the high-potential side switch.

12. The driving device according to any one of claims 1 to 3, characterized in that, The capacitance of the high-potential side capacitor is variable. The driving device further includes a capacitor control unit that controls the capacitance of the high-potential side capacitor.

13. The driving device as claimed in claim 9, characterized in that, The resistance value of the second resistive element is variable. The driving device further includes a resistance control unit that controls the resistance value of the second resistive element.

14. The driving device as claimed in claim 10, characterized in that, The resistance value of the third resistive element is variable. The driving device further includes a resistance control unit that controls the resistance value of the third resistive element.

15. The driving device as claimed in claim 11, characterized in that, The resistance value of the fourth resistive element is variable. The driving device further includes a resistance control unit that controls the resistance value of the fourth resistive element.

16. The driving device according to any one of claims 1 to 3, characterized in that, Also includes: A reference potential line, the potential of which is lower than that of the high potential line; A reference potential side switching control unit switches whether the control terminal of the switching element is connected to the reference potential line. A first resistive element on the reference potential side is configured in series with the reference potential side switching control unit in the path from the control terminal of the switching element to the reference potential line; A reference potential side capacitor is provided in parallel with a first resistor element on the reference potential side in the path from the control terminal of the switching element to the reference potential line; as well as A reference potential side discharge control unit controls whether or not to discharge the reference potential side capacitor.

17. The driving device according to any one of claims 1 to 3, characterized in that, At least one of the switching element and the high-potential side discharge control unit is a wide-bandgap semiconductor element with at least one of silicon carbide, gallium nitride, gallium oxide, and diamond as its main material.

18. The driving device according to any one of claims 1 to 3, characterized in that, The high-potential side discharge control unit is any one of a transistor element, an optocoupler, a digital isolator, a mechanical relay, and a photodiode.

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