Driving device, semiconductor device, and driving method

Abstract

To provide a drive device, a semiconductor apparatus, and a drive system capable of suppressing vibration of a semiconductor element with a low loss even when switching the semiconductor element at a high speed.SOLUTION: In a semiconductor apparatus 115, a drive device 130 has: a drive unit 500 that drives a control terminal of a semiconductor element 120 depending on a control signal input from the exterior, the semiconductor element 120 having a first main terminal, a second main terminal, and the control terminal that controls a connection state between the first and second main terminals, the first and second main terminals being connected in parallel with a snubber; and a drive control unit 530 that, during a time period where a voltage between the first and second main terminals changes only by a predetermined reference voltage difference with switching of the semiconductor element, reduces a drive capability of the drive unit compared with the other at least partial time period.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to a drive device, a semiconductor device, and a drive method. [Background technology]

[0002] In a power device such as a voltage-type inverter equipped with a semiconductor switching element (hereinafter also referred to as "semiconductor element") such as a metal oxide semiconductor field effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT), high-frequency voltage and current vibrations occur due to high-speed switching of the semiconductor element. Patent Document 1 discloses a vibration suppression circuit 20 that is added to the outside of a housing 10 of a semiconductor device 100 (paragraph 0018, Figs. 1A, 1B, and 2, etc.). Patent Document 2 describes that the resistance value between the control electrode of the semiconductor switching element and the output node is switched to different values ​​when the semiconductor switching element is turned on and when it is turned off (claim 1). [Prior art document] [Patent documents] [Patent Document 1] Patent No. 6597902 [Patent Document 2] International Publication No. 2017 / 026367 Summary of the Invention [Problem to be solved by the invention]

[0003] In recent years, the performance of semiconductor elements has improved, and semiconductor elements capable of high-speed switching, such as SiC-MOSFETs, have also been realized. Therefore, it is desirable to realize a driving method that can suppress the vibration of a semiconductor element with low loss even when the semiconductor element is switched at high speed. [Means for solving the problem]

[0004] In a first aspect of the present invention, there is provided a drive device. The drive device may include a drive unit having a first main terminal and a second main terminal, and a control terminal for controlling a connection state between the first main terminal and the second main terminal, and driving the control terminal of a semiconductor element, the first main terminal and the second main terminal of which are connected in parallel to a snubber, in response to a control signal input from outside. The drive device may include a drive control unit that reduces the drive capability of the drive unit during a period in which the main terminal voltage between the first main terminal and the second main terminal changes by a predetermined reference voltage difference due to switching of the semiconductor element, compared to at least a part of other periods.

[0005] The drive control unit may cause the drive unit to drive the control terminal at a first drive capability while the voltage across the main terminals is less than a first threshold during a period in which the semiconductor element is turned off. The drive control unit may cause the drive unit to drive the control terminal at a second drive capability higher than the first drive capability when the voltage across the main terminals becomes equal to or greater than the first threshold during a period in which the semiconductor element is turned off.

[0006] The drive control unit may cause the drive unit to drive the control terminal at a third drive capability while the voltage across the main terminals is equal to or higher than the second threshold during a period in which the semiconductor element is turned on. The drive control unit may cause the drive unit to drive the control terminal at a fourth drive capability lower than the third drive capability when the voltage across the main terminals becomes less than the second threshold during a period in which the semiconductor element is turned on.

[0007] The first threshold value and the second threshold value may be equal to or greater than 60% and less than 100% of the voltage between the main terminals in a steady state in which the semiconductor element is off.

[0008] The first threshold value and the second threshold value may be equal to or greater than 80% and less than 95% of the voltage between the main terminals in a steady state in which the semiconductor element is off.

[0009] The first threshold and the second threshold may be the same value.

[0010] The drive control unit may change the drive capability of the control terminal by changing at least one of the magnitude of a resistor connected between the control terminal and a reference potential, or the capacitance of a capacitor connected between the control terminal and the first main terminal or the second main terminal.

[0011] The drive unit may have a plurality of drive circuits, each of which has a resistor or capacitor and a drive switch connected in series between a reference potential and the control terminal, and the drive control unit may change the drive capability of the drive unit by switching the drive switches of each of the plurality of drive circuits.

[0012] The semiconductor element may be a SiC-MOSFET or a SiC-IGBT.

[0013] In a second aspect of the present invention, there is provided a semiconductor device, which may include a semiconductor element and a drive device that drives a control terminal of the semiconductor element.

[0014] In a third aspect of the present invention, there is provided a driving method. The driving method may include driving, by a driving unit, the control terminal of a semiconductor element having a first main terminal and a second main terminal and a control terminal for controlling a connection state between the first main terminal and the second main terminal, the control terminal being connected in parallel to a snubber, in response to a control signal input from outside. The driving method may include reducing the driving capability of the driving unit during a period in which a main terminal voltage between the first main terminal and the second main terminal changes by a predetermined reference voltage difference due to switching of the semiconductor element, compared to at least a part of other periods.

[0015] The above summary of the invention does not list all of the features of the present invention. Also, subcombinations of these features may also be inventions. [Brief description of the drawings]

[0016] [Figure 1] The configuration of a power device 100 according to this embodiment is shown together with a load 140. [Diagram 2]The configuration of a power device 100 according to a modified example of this embodiment is shown together with a load 140. [Diagram 3] 1 shows an example of transient changes in current and voltage when a semiconductor element is turned on. [Figure 4] 1 shows an example of transient changes in current and voltage when a semiconductor element is turned off. [Diagram 5] 1 shows the configuration of a semiconductor device 115 according to the present embodiment. [Figure 6] 4 shows operational waveforms when a semiconductor element is turned off. [Figure 7] 4 shows the operating waveforms when the semiconductor element is turned on. [Figure 8] 1 shows an example of transient changes in current and voltage when a semiconductor element is turned off. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0018] 1 shows a configuration of a power device 100 according to this embodiment together with a load 140. The load 140 is a motor, an electric device, or any other device that consumes power and operates by receiving power supplied from the power device 100. The power device 100 includes an electrolytic capacitor 110, a semiconductor device 115, an inductor 150, and a snubber 180.

[0019] The electrolytic capacitor 110 is connected between the positive and negative bus bars of the power device 100, and the semiconductor device 115 and load The electrolytic capacitor 110 functions as a voltage source for the semiconductor device 115. The electrolytic capacitor 110 accumulates a power supply voltage supplied between a positive bus bar and a negative bus bar from a power supply (not shown), and supplies the power supply voltage to the semiconductor device 115.

[0020] The semiconductor device 115 has one or more semiconductor elements 120a-b (also referred to as "semiconductor elements 120") and one or more driving devices 130a-b (also referred to as "driving devices 130"). In this embodiment, for convenience of explanation, a case will be described in which the semiconductor device 115 has two semiconductor elements 120 and two driving devices 130, but the semiconductor device 115 may have one semiconductor element 120 and one or three or more driving devices 130. The semiconductor device 115 may be a semiconductor module in which one or more semiconductor elements 120 and one or more driving devices 130 are integrated by resin sealing or the like.

[0021] Each semiconductor element 120 is a semiconductor switch element such as a MOSFET or an IGBT. Each semiconductor element 120 may be a SiC-MOSFET or a SiC-IGBT capable of faster switching. Each semiconductor element 120 has a first main terminal and a second main terminal, and a control terminal for controlling a connection state between the first main terminal and the second main terminal. When the semiconductor element 120 is a MOSFET, the semiconductor element 120 has a drain and a source as the first main terminal and the second main terminal, and has a gate as the control terminal. When the semiconductor element 120 is an IGBT, the semiconductor element 120 has a collector and an emitter as the first main terminal and the second main terminal, and has a gate as the control terminal. In this embodiment, for convenience of explanation, a case where the semiconductor element 120 is a MOSFET is shown. The semiconductor elements 120a to 120b are connected in series between the positive busbar and the negative busbar in this order.

[0022] Driving devices 130a-b are provided corresponding to semiconductor elements 120a-b, respectively. Each driving device 130 is connected to a control terminal of the corresponding semiconductor element 120, and drives the control terminal in response to a control signal input from outside. In this figure, a driving device 130 is provided individually for each semiconductor element 120, but multiple driving devices 130 may be collectively referred to as a "driving device."

[0023] The inductor 150 is connected in series with the load 140 between the positive bus and an intermediate terminal between the semiconductor elements 120a and 120b. The snubber 180 is connected between the positive bus and the negative bus outside the semiconductor device 115. Thus, the snubber 180 is connected in parallel with the first main terminal and the second main terminal of each semiconductor element 120 between the positive bus and the negative bus. The snubber 180 suppresses the oscillation of the voltage and current caused by the switching of the semiconductor elements 120. In this embodiment, the snubber 180 is, for example, an RC snubber, and may have a resistor 185 and a capacitor 190 connected in series between the positive bus and the negative bus.

[0024] The operation of the power device 100 in this figure is as follows. First, the drivers 130a-b receive a control signal from the outside and drive the semiconductor element 120a to turn off and the semiconductor element 120b to turn on. As a result, a current flows from the positive side of the electrolytic capacitor 110 to the negative side of the electrolytic capacitor 110 via the inductor 150, the load 140, and the semiconductor element 120b, supplying power to the load 140 and storing energy in the inductor 150.

[0025] Next, the drivers 130a-b receive a control signal from the outside and drive the semiconductor element 120a to ON and the semiconductor element 120b to OFF. The inductor 150 continues to pass a current due to the stored energy, and performs a freewheel operation in which the current output from the inductor 150 flows back to the inductor 150 via the load 140 and the semiconductor element 120a. When the power supplied to the load 140 decays, the drivers 130a-b receive a control signal from the outside and turn the semiconductor element 120a OFF and the semiconductor element 120b ON again.

[0026] Fig. 2 shows the configuration of a power device 100 according to a modified example of this embodiment, together with a load 140. The power device 100 in Fig. 2 is similar to the power device 100 in Fig. 1 except that it includes a plurality of snubbers 280a-b (also referred to as "snubbers 280") instead of snubber 180. Therefore, members having the same or similar functions and configurations are denoted by the same reference numerals, and descriptions thereof will be omitted except for the differences.

[0027] In this modification, each snubber 280 is provided corresponding to each semiconductor element 120 and is connected between the main terminals of the corresponding semiconductor element 120. Thus, each snubber 280 is connected in parallel with the first main terminal and the second main terminal of the corresponding semiconductor element 120. In this modification, snubber 280a is, for example, an RC snubber, and may have a resistor 285a and a capacitor 290a connected in series between the main terminals of the corresponding semiconductor element 120. Similarly, snubber 280b is, for example, an RC snubber, and may have a resistor 285b and a capacitor 290b connected in series between the main terminals of the corresponding semiconductor element 120.

[0028] 1 and 2, a rectifier diode with a cathode on the positive bus side and an anode on the intermediate terminal side may be used instead of the semiconductor element 120a. As an example, the rectifier diode may be a SiC diode capable of high speed switching.

[0029] Fig. 3 shows an example of transient changes in current and voltage when a semiconductor element is turned on. This figure is an excerpt from Fig. 5 of Patent Document 1. "Comparative Example", "Example 1", and "Example 2" in this figure refer to the Comparative Example, Example 1, and Example 2 in Patent Document 1, and do not refer to the Comparative Example and Example in this specification.

[0030] The "Comparative Example" is a comparison of the collector current I C (i.e. the current flowing between the main terminals) and the collector-emitter voltage V CE The "Example 1" shows a transient change in the current (i.e., the voltage between the main terminals) when the "semiconductor device 100" of Patent Document 1 is equipped with the "vibration suppression circuit 20" having the same connection relationship as the snubber 180 in FIG. 1 of the present application. I c and voltage V CE"Example 2" shows a transient change in the current I C and voltage V CE This shows a transient change (paragraph 0049 of Patent Document 1).

[0031] As shown in the figure, in the "comparative example" in which the "vibration suppression circuit 20" is not added to the "semiconductor device 100", when the "semiconductor element 14a" is turned on, a current I C and voltage V CE In contrast, in the "first embodiment" and the "second embodiment" in which the "vibration suppression circuit 20" is added to the "semiconductor device 100", when the "semiconductor element 14a" is turned on, the current I C and voltage V CE The "vibration suppression circuit 20" of Patent Document 1 also suppresses the current I C and voltage V CE In FIG. 5 of Patent Document 1, the voltage V CE indicates the voltage between the main terminals of the opposing "semiconductor element 15a" when the "semiconductor element 14a" is turned on (see paragraph 0049).

[0032] Fig. 4 shows an example of transient changes in current and voltage when the semiconductor element 120b is turned off. This figure shows changes in drain current Id and drain-source voltage Vds when a SiC-MOSFET is used as an example of the semiconductor element 120b in the power device 100 of Fig. 1. In the example of this figure, a 1200V / 200A semiconductor module is targeted, and the wiring inductance Ls1 between the electrolytic capacitor 110 and the snubber 180 in Fig. 1 is 20nH, the wiring inductance Ls2 between the snubber 180 and the semiconductor elements 120a-b in the semiconductor device 115 is 5nH, the resistance Rs of the resistor 185 is 0.5Ω, the capacitance Cs of the capacitor 190 is 50nF, and the resistance (gate resistance) between the driver 130b and the semiconductor element 120b is 0.1Ω, all of which are constant.

[0033] There is a wiring inductance Ls2 between the semiconductor elements 120a-b and the snubber 180. Also, each semiconductor element 120 has a junction capacitance (denoted as "Cos") between the drain and source. Therefore, the semiconductor device 115 includes an LC circuit in which the inductance Ls2 and the junction capacitance Cos are connected in series on the side closer to the semiconductor device 115 than the snubber 180. Here, if the snubber 180 is placed as close as possible to the semiconductor elements 120a-b and the wiring is shortened, the wiring inductance Ls2 can be reduced. However, since the snubber 180 is provided outside the package of the semiconductor device 115 and the semiconductor elements 120a-b have a certain size, there is a limit to suppressing the wiring inductance Ls2.

[0034] Such an LC circuit formed by inductance Ls2 and junction capacitance Cos generates local fluctuations in current Id and voltage Vds that cannot be sufficiently suppressed by snubber 180 or snubber 280 that is farther away from semiconductor elements 120a-b. In this figure, semiconductor element 120b is turned off at the time point of 15.0 μs on the horizontal axis, and at this timing, large current and voltage oscillations at relatively high frequencies occur for a short period of time compared to the current and voltage oscillations in FIG.

[0035] Here, in order to suppress the local vibrations caused by the LC circuit consisting of the inductance Ls2 and the junction capacitance Cos as shown in Figure 3, we consider providing a damping resistor Rd in series with this LC circuit. The damping coefficient ζ when such a damping resistor Rd is provided is expressed by the following equation (1). ζ=Rd / 2 √(Cos / Ls2) (1)

[0036] The larger the damping coefficient ζ is, the more the vibration caused by the LC circuit can be damped. From this viewpoint, the damping coefficient ζ may be 0.8 to 1.0 or more. Even if the snubber 180 or 280 is provided outside the semiconductor device 115, the power device 100 places the snubber 180 or 280 as close to the semiconductor device 115 as possible. Therefore, the inductance Ls1 can be several times to several tens of times or more than the inductance Ls2. As is clear from the formula (1), the damping coefficient ζ is proportional to the −1 / 2 power of the inductance. Therefore, in order to suppress the resonance of the LC circuit caused by the inductance Ls1+Ls2 and the junction capacitance Cos by the damping resistor Rd without providing the snubber 180 or 280, it is necessary to make the damping resistor Rd several times to several tens of times or more in order to realize the same magnitude of the damping coefficient ζ. For example, if Ls1+Ls2 is 16 times Ls2, then the damping resistance Rd must be four times larger to achieve the same damping coefficient ζ.

[0037] Here, the switching loss Psw, which is the energy (or power) lost during switching of the semiconductor element 120b, is the product of the current (e.g., drain current) Id flowing between the main terminals of the semiconductor element 120b during switching, the voltage (e.g., drain-source voltage) Vds between the main terminals of the semiconductor element 120b, and the switching time Tsw. If the switching loss Psw is generated by a damping resistor Rd, then Psw=Vd×Id=Rd×Id 2 × Tsw. Therefore, the damping resistance Rd is expressed by the following equation (2). Rd=Psw / (Id 2 ) / Tsw (2)

[0038] It can be seen from formula (2) that increasing the damping resistance Rd increases the switching loss Psw of the semiconductor element 120b. Therefore, when the resonance of the LC circuit is suppressed by the damping resistance Rd without providing the snubbers 180 and 280, the switching loss Psw increases as the damping resistance Rd increases.

[0039] Therefore, the power device 100 uses a snubber such as the snubber 180 in FIG. 1 and the snubber 280 in FIG. 2 to suppress the vibrations as shown in FIG. 3, and generates a switching loss Psw by the semiconductor element 120 to generate a damping resistance Rd that realizes a certain degree of damping coefficient ζ to suppress the local vibrations caused by the LC circuit formed by the inductance Ls2 and the junction capacitance Cos.

[0040] 5 shows the configuration of a semiconductor device 115 according to this embodiment together with an electrolytic capacitor 110. The semiconductor device 115 suppresses local vibrations caused by an LC circuit due to an inductance Ls2 and a junction capacitance Cos in a power device 100 to which a snubber such as the snubber 180 in FIG. 1 or the snubber 280 in FIG. 2 is added.

[0041] In this figure, components with the same reference numerals as those in Figure 1 or Figure 2 have the same functions and configurations as the corresponding components in Figure 1 or Figure 2, and therefore will not be described below except for the differences. As shown in Figures 1 and 2, the semiconductor device 115 has one or more semiconductor elements 120 and one or more driving devices 130. In this figure, the description will focus on one semiconductor element 120 (e.g., semiconductor element 120b) and one driving device 130 (e.g., driving device 130b).

[0042] The driving device 130 includes a driving section 500 and a driving control section 530. The driving section 500 receives control from the driving control section 530 according to a control signal input from the outside, and drives the control terminal of the semiconductor element 120 according to the control signal. The driving section 500 has a driving circuit in which a resistor 510a and a driving switch 520a are connected in series between a negative side bus bar serving as a negative reference potential and the control terminal of the semiconductor element 120, and a driving circuit (negative side driving circuit) in which a resistor 510b and a driving switch 520b are connected in series. The driving section 500 also has a driving circuit in which a resistor 510c and a driving switch 520c are connected in series between a positive side bus bar serving as a positive reference potential and the control terminal of the semiconductor element 120, and a driving circuit (positive side driving circuit) in which a resistor 510d and a driving switch 520d are connected in series. In the example shown in the figure, the driving switches 520a-b are p-channel MOSFETs, and the driving switches 520c-d are n-channel MOSFETs. Alternatively, each of the driving switches 520a-d (also referred to as "driving switch 520") may be any switching element that can connect or disconnect between the control terminal of the semiconductor element 120 and the positive bus or the negative bus via each of resistors 510a-d (also referred to as "resistor 510").

[0043] The drive control unit 530 controls the drive unit 500 in response to a control signal input from the outside. Here, the drive control unit 530 performs control to reduce the drive capability of the drive unit 500 during a period in which the main terminal voltage between the first main terminal and the second main terminal of the semiconductor element 120 changes by a predetermined reference voltage difference due to switching of the semiconductor element 120, compared to at least a part of other periods. In this embodiment, the drive control unit 530 changes the drive capability of the drive unit 500 by switching the drive switches 510 of each of the multiple drive circuits.

[0044] The drive control unit 530 includes a plurality of voltage dividing resistors 540a-b, a buffer 545, voltage sources 550a-b (also referred to as "voltage sources 550"), and a plurality of drivers 560a-d (also referred to as "drivers 560"). The voltage dividing resistors 540a-b are connected in series between the first main terminal and the second main terminal of the semiconductor element 120, and divide the voltage between the main terminals of the semiconductor element 120 by a resistance ratio of a resistance value R1 of the voltage dividing resistor 540a to a resistance value R2 of the voltage dividing resistor 540b, thereby outputting a detection signal proportional to the voltage between the main terminals. Here, if the voltage between the main terminals of the semiconductor element 120 (the drain-source voltage in this figure) is Vds, the detection signal is R2 / (R1+R2)·Vds.

[0045] The buffer 545 buffers and outputs a control signal input from the outside. The buffer 545 may amplify and output the control signal to drive the drivers 560a-d. In this embodiment, the control signal instructs the semiconductor element 120 to be turned off when it is at a low level and to be turned on when it is at a high level. The voltage source 550a outputs a threshold voltage Vth1 to be compared with a detection value of the voltage between the main terminals. The voltage source 550b outputs a threshold voltage Vth2 to be compared with a detection value of the voltage between the main terminals.

[0046] The driver 560a is connected between the voltage dividing resistors 540a-b, to the buffer 545, and to the voltage source 550a. The driver 560a is a driver with a comparator, and when the control signal input via the buffer 545 is at a low level, the driver 560a sets the control terminal of the drive switch 520a to a low level to turn on the drive switch 520a on condition that the detection signal of the voltage between the main terminals is equal to or higher than the threshold voltage Vth1. When the control signal is at a high level or when the detection signal of the voltage between the main terminals is less than the threshold voltage Vth1, the driver 560a sets the control terminal of the drive switch 520a to a high level to turn off the drive switch 520a. Here, since the detection signal is a resistive voltage division of the voltage between the main terminals of the semiconductor element 120, the driver 560a is essentially comparing the voltage between the main terminals with a first threshold Th1 which is (R1+R2) / R2 times the threshold voltage Vth1.

[0047] The driver 560b is connected between the voltage dividing resistors 540a-b and to the buffer 545. When the control signal is at a low level, the driver 560b sets the control terminal of the driving switch 520b to a low level to turn on the driving switch 520b. When the control signal is at a high level, the driver 560b sets the control terminal of the driving switch 520b to a high level to turn off the driving switch 520b.

[0048] As a result, during a period in which the drivers 560a-b turn off the semiconductor element 120 in response to the control terminal switching from a high level to a low level, while the voltage across the main terminals starts from a state of approximately 0 and is less than the first threshold value Th1, the drivers 560a-b turn off the driving switch 520a and turn on the driving switch 520b to drive the control terminal at the first driving capability by the driving unit 500. When the voltage across the main terminals becomes equal to or greater than the first threshold value Th1, the drivers 560a-b turn on the driving switches 520a-b to drive the control terminal at the second driving capability.

[0049] Here, when the driving switch 520a is off and the driving switch 520b is on, the magnitude of the gate resistance is the resistance value Rg2 of the resistor 510b, whereas when the driving switches 520a-b are on, the magnitude of the gate resistance is the combined resistance value Rg1·Rg2 / (Rg1+Rg2) of the parallel connection of the resistance values ​​Rg1 and Rg2 of the resistors 510a-b, which is smaller than the resistance value Rg2. Therefore, the second driving capability when the driving switches 520a-b are on is higher than the first driving capability when the driving switch 520a is off and the driving switch 520b is on.

[0050] The driver 560c is connected between the voltage dividing resistors 540a-b and to the buffer 545. When the control signal is at a high level, the driver 560c sets the control terminal of the driving switch 520c to a high level to turn on the driving switch 520c. When the control signal is at a low level, the driver 560c sets the control terminal of the driving switch 520c to a low level to turn off the driving switch 520c.

[0051] The driver 560d is connected between the voltage dividing resistors 540a-b, to the buffer 545, and to the voltage source 550b. The driver 560d is a driver with a comparator, and when the control signal input via the buffer 545 is at a high level, the driver 560d sets the control terminal of the drive switch 520d to a high level to turn on the drive switch 520d on condition that the detection signal of the voltage between the main terminals is equal to or higher than the threshold voltage Vth2. When the control signal is at a low level or when the detection signal of the voltage between the main terminals is less than the threshold voltage Vth2, the driver 560d sets the control terminal of the drive switch 520d to a low level to turn off the drive switch 520d. Here, since the detection signal is a resistive voltage division of the voltage between the main terminals of the semiconductor element 120, the driver 560d is essentially comparing the voltage between the main terminals with a second threshold Th2, which is (R1+R2) / R2 times the threshold voltage Vth2.

[0052] As a result, during a period in which the drivers 560c-d turn on the semiconductor element 120 in response to the control terminal switching from a low level to a high level, while the voltage across the main terminals is equal to or higher than the second threshold Th2, the drivers 560c-d turn on the driving switches 520c-d and drive the control terminals with the third driving capability by the driving unit 500. When the voltage across the main terminals becomes less than the second threshold Th2, the drivers 560c-d turn on the driving switch 520c and turn off the driving switch 520d and drive the control terminals with the fourth driving capability by the driving unit 500. Here, the gate resistance when the driving switch 520c is on and the driving switch 520d is off is larger than the gate resistance when the driving switches 520c-d are on, and therefore the fourth driving capability is lower than the third driving capability.

[0053] In this way, the drive control section 530 can change the drive capability of the control terminal by changing the magnitude of the control resistor (gate resistor) connected between the control terminal and the reference potential, i.e., the magnitude of the combined resistance. Instead of the configuration shown in this figure, the drive section 500 may have a control resistor based on a variable resistor, and the drive control section 530 may change the resistance value of the variable resistor of the drive section 500 to change the drive capability of the control terminal.

[0054] Furthermore, the driving section 500 may have a configuration including a plurality of driving circuits, each having a capacitor and a driving switch 510 connected in series between a reference potential and a control terminal. In this case, the driving control section 530 changes the driving capability of the control terminal by changing the capacitance of the capacitor connected between the control terminal and the first main terminal or the second main terminal.

[0055] Here, when the same gate current is applied, the more the combined capacitance of the capacitors connected between the control terminal and the main terminal of the semiconductor element 120 increases, the more the change in the gate voltage is suppressed, and the lower the driving ability of the driving unit 500 becomes. Therefore, when a capacitor is used instead of the resistor 510a, the driver 560a sets the control terminal of the driving switch 520a to a low level and turns on the driving switch 520a on condition that the detection signal of the voltage between the main terminals is less than the threshold voltage Vth1 when the control signal input via the buffer 545 is at a low level. Also, when a capacitor is used instead of the resistor 510d, the driver 560d sets the control terminal of the driving switch 520d to a high level and turns on the driving switch 520d on condition that the detection signal of the voltage between the main terminals is less than the threshold voltage Vth2 when the control signal input via the buffer 545 is at a high level.

[0056] 6 shows operational waveforms at the time of turning off the semiconductor element 120. Specifically, this figure shows the changes over time along the horizontal axis for the control signal, the connection state of the drive switch 520a, the connection state of the drive switch 520b, the control voltage (gate voltage) of the semiconductor element 120, the voltage VDS between the main terminals, and the current (drain current) ID flowing through the semiconductor element 120.

[0057] In a steady state where the semiconductor element 120 is on, the control signal is at a high level, the drive switches 520a-b are off, and the drive switches 520c-d are on. In this state, the voltage VDS between the main terminals of the semiconductor element 120 is approximately 0 V, and a current ID required by the load 140 flows through the semiconductor element 120.

[0058] When the control signal changes from high level to low level, the driving device 130 starts the turn-off operation of the semiconductor element 120. The driver 560a turns off the driving switch 520a during a period t1 in which the main terminal voltage VDS is less than the first threshold Th1. The driver 560b turns on the driving switch 520b as the control signal changes to low level. In addition, the drivers 560c-d turn off the driving switches 520c-d. As a result, the driving control unit 530 drives the control terminal of the semiconductor element 120 with the first driving capability to drop the control voltage of the control terminal.

[0059] When the control voltage drops to a certain level, the semiconductor element 120 starts to turn off. In response to this, the voltage VDS between the main terminals rises and becomes equal to or greater than the first threshold Th1 after a period t1 from when the control signal changes to a low level. In response to the voltage VDS between the main terminals becoming equal to or greater than the first threshold Th1, the driver 560a turns on the driving switch 520a. In response to the start of turning off, the semiconductor element 120 reduces the current ID as shown by the solid line in the figure, and the current ID becomes 0 after a period t1+t2 from when the control signal changes to a low level, turning off the semiconductor element 120.

[0060] According to the driving device 130 of this embodiment, in the turn-off operation of the semiconductor element 120, during the period in which the main terminal voltage VDS changes from approximately 0 to the first threshold Th1 (i.e., during the period in which the main terminal voltage VDS changes by approximately the voltage difference of the first threshold Th1), the driving ability of the driving unit 500 is reduced compared to the period after the main terminal voltage VDS becomes equal to or greater than the first threshold. Here, if the driving device 130 does not have a driving circuit including the resistor 510a and the driving switch 520a and drives the control terminal of the semiconductor element 120 only by the driving switch 520b even after the main terminal voltage VDS becomes equal to or greater than the first threshold Th1, the current ID decreases slowly as shown by the dashed line in the figure. In this case, compared to the case in which the control terminal of the semiconductor element 120 is driven using both the driving switch 520a and the driving switch 520b when the main terminal voltage VDS becomes equal to or greater than the first threshold Th1, the turn-off period becomes longer as shown by t11+t22 in the figure, and switching loss increases.

[0061] In contrast, according to the driving device 130 of this embodiment, the driving capability of the driving unit 500 is reduced during period t1 when the main terminal voltage VDS changes by the reference voltage difference, whereas the driving capability of the driving unit 500 is increased during period t2 when the main terminal voltage VDS is relatively unchanged. Here, the greater the rate of change of the main terminal voltage VDS, the greater the vibration accompanying turn-off of the semiconductor element 120. However, the driving device 130 reduces the driving capability of the driving unit 500 during period t1 when the main terminal voltage VDS changes significantly, thereby suppressing the rate of change of the voltage VDS, thereby efficiently suppressing the occurrence of vibration.

[0062] 7 shows operational waveforms at the time of turning on the semiconductor element 120. Specifically, this figure shows the change over time in the horizontal axis direction for each of the control signal, the connection state of the drive switch 520d, the connection state of the drive switch 520c, the control voltage (gate voltage) of the semiconductor element 120, the voltage VDS between the main terminals, and the current (drain current) ID flowing through the semiconductor element 120.

[0063] In a steady state where the semiconductor element 120 is off, the control signal is at a low level, the drive switches 520a-b are on, and the drive switches 520c-d are off. In this state, the voltage VDS between the main terminals of the semiconductor element 120 is approximately the power supply voltage generated by the electrolytic capacitor 110, and no current flows through the semiconductor element 120.

[0064] When the control signal changes from low level to high level, the drive device 130 starts the turn-on operation of the semiconductor element 120. The drivers 560c-d turn on the drive switches 520c-d while the main terminal voltage VDS is equal to or higher than the second threshold Th2. In addition, the drivers 560a-b turn off the drive switches 520a-b. As a result, the drive control unit 530 drives the control terminal of the semiconductor element 120 with the third drive capability to increase the control voltage of the control terminal.

[0065] When the control voltage rises to a certain level, the semiconductor device 120 starts to turn on. Accordingly, the voltage VDS across the main terminals drops, and becomes less than the second threshold Th2 after a period t3 from when the control signal changes to a high level. In response to the voltage VDS across the main terminals becoming less than the second threshold Th2, the driver 560d turns off the drive switch 520d. In response to the start of the turn-on, the semiconductor device 120 lowers the voltage VDS across the main terminals as shown by the solid line in the figure, and makes the voltage VDS across the main terminals almost 0 after a period t3+t4 from when the control signal changes to a high level. In addition, in response to the start of the turn-on, the semiconductor device 120 raises the current ID as shown by the solid line in the figure, and makes the current ID a steady current near the time when the period t3+t4 has elapsed since the control signal changed to a high level.

[0066] According to the driving device 130 of this embodiment, during the period in which the main terminal voltage VDS changes from the second threshold Th2 to approximately 0 in the turn-on operation of the semiconductor element 120 (i.e., during the period in which the main terminal voltage VDS changes approximately by the voltage difference of the second threshold Th2), the driving capability of the driving unit 500 is reduced compared to the period in which the main terminal voltage VDS is equal to or greater than the second threshold. If the driving device 130 did not have a driving circuit including the resistor 510d and the driving switch 520d and drove the control terminal of the semiconductor element 120 only by the driving switch 520bc even while the main terminal voltage VDS was equal to or greater than the second threshold Th2, the decrease in the main terminal voltage VDS and the increase in the current ID would be slower, as shown by the dashed lines in the figure. In this case, compared to the case where the control terminal of the semiconductor element 120 is driven using both the driving switch 520c and the driving switch 520d while the main terminal voltage VDS is equal to or higher than the second threshold value Th2, the turn-on period becomes longer as shown by t33+t44 in the figure, resulting in increased switching loss.

[0067] In contrast, according to the driving device 130 of this embodiment, the driving capability of the driving unit 500 is reduced during period t4 when the main terminal voltage VDS changes by the reference voltage difference, whereas the driving capability of the driving unit 500 is increased during period t3 when the main terminal voltage VDS is relatively unchanged. Here, the greater the rate of change of the main terminal voltage VDS, the greater the vibration accompanying turn-off of the semiconductor element 120. However, the driving device 130 reduces the driving capability of the driving unit 500 during period t4 when the main terminal voltage VDS changes significantly to suppress the rate of change of the voltage VDS, and suppresses the rate of decrease in the resistance value of the semiconductor element 120 to increase the damping resistance Rd, thereby efficiently suppressing the occurrence of vibration.

[0068] At least one of the first threshold value Th1 to be compared with the main terminal voltage VDS during the turn-off period and the second threshold value Th2 to be compared with the main terminal voltage VDS during the turn-on period may be 60% or more and less than 100%, or 80% or more and less than 95%, of the main terminal voltage in the steady state when the semiconductor element 120 is off. The first threshold value Th1 and the second threshold value Th2 may be the same value or different values.

[0069] Fig. 8 shows an example of the transient changes in current and voltage when the semiconductor element is turned off. In this figure, the same conditions as in Fig. 4 are applied, except that the resistance (gate resistance) between the driver 130b and the semiconductor element 120b is increased from 0.1 Ω to 2 Ω during the period in which the main terminal voltage changes by the reference voltage difference.

[0070] In Fig. 4, at the timing of turning off the semiconductor element 120b at 15.0 μs on the horizontal axis, local high-frequency oscillations of the current Id and voltage Ids due to the LC circuit formed by the inductance Ls2 and the junction capacitance Cos are observed. In contrast, in this figure, such high-frequency oscillations can be suppressed. The driver 130 only needs to increase the gate resistance during the period in which the main terminal voltage changes by the reference voltage difference, and may increase the gate resistance by, for example, two or more times.

[0071] Note that the extent to which the driving capability of the driving device 130 is reduced during the period in which the voltage between the main terminals changes by the reference voltage difference, i.e., the extent to which the gate resistance is increased, for example, may vary depending on the magnitude of the wiring inductance Ls2, etc. Therefore, the manufacturer of the semiconductor device 115 or the user of the semiconductor device 115 may determine the driving capability of the driving device 130 using the results of simulating the semiconductor device 115 or the results of testing the semiconductor device 115. Furthermore, the driving device 130 may have a setting memory or the like that can externally set the driving capability of the driving device 130 during the period in which the voltage between the main terminals changes by the reference voltage difference, and the driving capability of the driving device 130 may be switched according to the set value.

[0072] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the description of the claims that such modifications and improvements can also be included in the technical scope of the present invention.

[0073] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and may be realized in any order unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is essential to perform the process in this order. [Explanation of symbols]

[0074] 100 Power equipment 110 Electrolytic capacitor 115 Semiconductor Devices 120a~b Semiconductor element 130a~b Driving device 140 Load 150 Inductor 180 Snubber 185 Resistance 190 Capacitor 280a~b snubber 285a~b Resistance 290a~b Capacitor 500 Drive unit 510a~d resistance 520a~d Drive switch 530 Drive control unit 540a~b Voltage divider resistor 545 Buffer 550a~b Voltage source 560a~d Driver

Claims

1. a drive unit which drives the control terminal of a semiconductor element having a first main terminal and a second main terminal and a control terminal for controlling on / off between the first main terminal and the second main terminal, the control terminal being connected in parallel to a snubber and which drives the control terminal in response to a control signal input from outside; a drive control unit that drives the control terminal by the drive unit at a first drive capability while a main terminal voltage between the first main terminal and the second main terminal is less than a first threshold during a period in which the semiconductor element is turned off, and drives the control terminal by the drive unit at a second drive capability higher than the first drive capability when the main terminal voltage becomes equal to or greater than the first threshold; A drive unit comprising:

2. The driving device of claim 1, wherein during a period in which the semiconductor element is turned on, the driving control unit drives the control terminal at a third driving capacity while the voltage between the main terminals is equal to or higher than a second threshold value, and when the voltage between the main terminals becomes less than the second threshold value, the driving control unit drives the control terminal at a fourth driving capacity lower than the third driving capacity.

3. The drive device according to claim 2 , wherein the first threshold value and the second threshold value are equal to or greater than 60% and less than 100% of the voltage between the main terminals in a steady state in which the semiconductor element is off.

4. 4. The drive device according to claim 2, wherein the first threshold value and the second threshold value are equal to or greater than 80% and less than 95% of the voltage between the main terminals in a steady state in which the semiconductor element is off.

5. The drive device according to claim 2 , wherein the first threshold value and the second threshold value are the same value.

6. A drive unit which has a first main terminal and a second main terminal, and a control terminal which controls on / off between the first main terminal and the second main terminal, and drives the control terminal of a semiconductor element in which the first main terminal and the second main terminal are connected in parallel with a snubber in response to a control signal input from outside; a drive control unit that drives the control terminal by the drive unit at a third drive capability while a main terminal voltage between the first main terminal and the second main terminal is equal to or higher than a second threshold during a period in which the semiconductor element is turned on, and drives the control terminal by the drive unit at a fourth drive capability lower than the third drive capability when the main terminal voltage becomes lower than the second threshold; A drive unit comprising:

7. 7. The drive device according to claim 1, wherein the drive control unit changes the drive capability of the control terminal by changing at least one of a magnitude of a resistor connected between the control terminal and a reference potential, or a capacitance of a capacitor connected between the control terminal and the first main terminal or the second main terminal.

8. the drive unit includes a plurality of drive circuits, each of which has a resistor or a capacitor and a drive switch connected in series between a reference potential and the control terminal; The drive control unit changes the drive capacity of the drive unit by switching the drive switches of the plurality of drive circuits. A drive arrangement according to any one of claims 1 to 7.

9. 9. The drive device according to claim 1, wherein the semiconductor element is a SiC-MOSFET or a SiC-IGBT.

10. The semiconductor element; The driving device according to claim 1 , which drives a control terminal of the semiconductor element; A semiconductor device comprising:

11. a semiconductor element including a first main terminal and a second main terminal, and a control terminal for controlling on / off between the first main terminal and the second main terminal, the control terminal being connected in parallel with a snubber, the control terminal being driven by a drive unit in response to a control signal input from outside; during a period in which the semiconductor element is turned off, while a main terminal voltage between the first main terminal and the second main terminal is less than a first threshold, the control terminal is driven by the drive unit at a first drive capability, and when the main terminal voltage becomes equal to or greater than the first threshold, the control terminal is driven by the drive unit at a second drive capability higher than the first drive capability; A driving method comprising:

12. A semiconductor element having a first main terminal and a second main terminal, and a control terminal for controlling on / off between the first main terminal and the second main terminal, the control terminal of which is connected in parallel with a snubber, the control terminal being driven by a drive unit in response to a control signal input from outside; during a period in which the semiconductor element is turned on, while a main terminal voltage between the first main terminal and the second main terminal is equal to or higher than a second threshold, the control terminal is driven by the drive unit at a third drive capability, and when the main terminal voltage becomes less than the second threshold, the control terminal is driven by the drive unit at a fourth drive capability lower than the third drive capability; A driving method comprising:

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