Gate driver device

Abstract

The object of the invention is to provide a gate driver device capable of reducing noise more than conventional ones. A gate driver device (100) comprises: a command generation circuit (20) that generates and outputs a gate driver command based on an input signal (Vin); a constant output circuit (10) connected in parallel to the command generation circuit (20) and outputs a constant voltage signal based on the input signal (Vin); a complementary emitter follower circuit (30) that amplifies the gate driver command; and a current limiting element (82) that is arranged on the input side or the output side of the complementary emitter follower circuit (30) and that suppresses the reverse flow of the current.The gate driving device (100) applies a gate driving voltage obtained by combining the gate driving command and the constant voltage signal to the gate terminal of a semiconductor switching element (92).

Description

Technical field

[0001] The present invention relates to a gate driver device. State of the art

[0002] Some voltage-driven elements included in a semiconductor power conversion device are controlled to be turned on or off by a gate driver device.In some conventional gate driving devices, a waveform shaping circuit that shapes an input voltage signal that changes stepwise to obtain a voltage waveform having a predetermined rate of voltage change, and a complementary emitter follower circuit or a complementary source follower circuit whose input side is connected to the output of the waveform shaping circuit and whose output side is connected to the gate terminal of the voltage-driven element are provided, and the emitter terminal or the source terminal of the voltage-driven element is connected to an intermediate connection point between a forward bias power supply for supplying a forward bias voltage and a reverse bias power supply for supplying a reverse bias voltage (see, for example, Patent Document 1).

[0003] A waveform shaping circuit of a gate driving device disclosed in Patent Document 1 is configured such that a resistor and a capacitor are connected in an inverted L shape, and outputs a waveform with a first-order delay based on the time constant for the resistor and the capacitor. BibliographyPatent document

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. JP 2004-48959 A Summary of the inventionProblem to be solved by the invention

[0005] In the gate driving device disclosed in Patent Document 1, noise (switching noise) caused by the change of current with respect to time (dI / dt) in the current rise before the Miller period can be suppressed by appropriately setting the time constant for the waveform shaping circuit.

[0006] Meanwhile, since only a time constant can be set for the waveform shaping circuit, the gate drive current increases in the Miller period when a voltage drop occurs, and a change in voltage with respect to time (dV / dt) in the voltage decrease becomes steeper, so that noise caused by the change in voltage with respect to time may be increased.

[0007] The present invention was conceived to solve the problems described above. It is therefore an object of the present invention to provide a gate drive device capable of reducing noise more than conventional ones. Ways to solve the problem

[0008] A gate driving device according to the present invention comprises: a command generating circuit that generates and outputs a gate driving command based on an input signal; a constant output circuit connected in parallel to the command generating circuit and outputs a constant voltage signal or a constant current signal based on the input signal; an amplifying circuit that amplifies the gate driving command; and a current limiting element arranged on the input side or the output side of the amplifying circuit and that suppresses the backflow of the current, wherein the gate driving device applies a gate driving voltage obtained by combining the gate driving command and the constant voltage signal or the constant current signal to the gate terminal of a semiconductor switching element. Effect of the invention

[0009] The gate driving device according to the present invention can reduce noise more than conventional ones. Short description of the drawings Fig. 1 is a circuit diagram showing a gate driving device according to Embodiment 1. Fig. 2A is a configuration diagram showing an example in which the gate driving device according to Embodiment 1 is applied. Fig. 2B is a configuration diagram showing an example in which the gate driving device according to Embodiment 1 is applied and MOSFETs are used as semiconductor switching elements. Fig. 3 schematically shows operation waveforms in the gate driving device according to Embodiment 1. Fig. Figure 4A schematically shows operating waveforms when a main circuit carries rated current. Fig. Figure 4B schematically shows operating waveforms when the main circuit carries a small current. Fig. 5A schematically shows operation waveforms according to a comparative example when a main circuit carries a large current. Fig. 5B shows operation waveforms according to Embodiment 1 when the main circuit carries a large current. Fig. 5C shows operation waveforms according to the comparative example when the main circuit carries a small current. Fig. 5D shows operation waveforms according to Embodiment 1 when the main circuit carries a large current. Fig. 6 is a circuit diagram showing a gate driving device according to Embodiment 2. Fig. 7A shows operation waveforms according to Embodiment 2 when the main circuit carries a large current. Fig. 7B shows operation waveforms according to Embodiment 2 when the main circuit carries a small current. Fig. 8 is a circuit diagram showing a gate driving device according to Embodiment 3. Fig. 9 is a circuit diagram showing a modification of the gate driving device according to Embodiment 3. Fig. 10 is a circuit diagram showing a gate driving device according to Embodiment 4. Fig. 11 shows operation waveforms according to Embodiment 4 when the main circuit carries a large current. Description of embodimentsEmbodiment 1

[0010] Embodiment 1 will be described with reference to Fig. 1 to Fig. 5D described. Fig. 1 is a circuit diagram showing a gate driving device according to Embodiment 1. A gate driving device 100 has an input side connected to an interface circuit 91 and an output side connected to a semiconductor switching element 92. Based on an input signal Vin input via the interface circuit 91, the gate driving device 100 generates a gate driving signal, that is, a gate driving voltage, and outputs the gate driving signal to the gate terminal of the semiconductor switching element 92.

[0011] The gate driver device 100 comprises the following: a constant output circuit 10, a command generation circuit 20, a current limiting element 82 and a complementary emitter follower circuit 30, ie, an amplifying circuit, and the constant output circuit 10 and the command generation circuit 20 are connected in parallel to each other.

[0012] The constant output circuit 10 is connected to the input side of the complementary emitter follower circuit 30 via a diode 81 and a connection point 83. The connection point 83 is arranged between the current limiting element 82 and the complementary emitter follower circuit 30. The command generation circuit 20 is connected to the input side of the complementary emitter follower circuit 30 via the current limiting element 82 and the connection point 83.

[0013] The constant output circuit 10 includes a resistor 11 disposed between an electrical path L1 on the ground side and an electrical path L2 on the high-potential side, and is a constant-voltage output circuit that outputs a constant-voltage signal. The output terminal of the constant output circuit 10 is connected to the anode of the diode 81. The cathode of the diode 81 is connected to the connection point 83.

[0014] The command generation circuit 20 includes an RC resonance circuit formed by a resistor 21 and a capacitor 23. The command generation circuit 20 shapes the input signal Vin, which is a stepped voltage signal, into a command waveform with a predetermined voltage change rate and outputs the shaped signal as a gate drive command. The command generation circuit 20 is formed by a series circuit arrangement of the resistor 21 and a Zener diode 22, a diode 29, and the capacitor 23, which are connected in parallel with each other.

[0015] Resistor 21 is arranged between electrical path L1 on the ground side and electrical path L3 on the high-potential side, and is connected to the cathode of Zener diode 22 on the high-potential side. Zener diode 22 and diode 29 are arranged so that the direction from electrical path L3 on the high-potential side to electrical path L1 on the ground side is the forward direction.

[0016] One end of capacitor 23 is grounded, and the other end is connected to the high-potential side electrical path L3. The output of command generation circuit 20 is input to complementary emitter follower circuit 30 via current limiting element 82 and connection point 83.

[0017] The Zener diode 22 is an example of a constant-voltage element, and it clamps the voltage at a predetermined breakdown voltage so that the gate drive command is maintained at the breakdown voltage, as described below. Furthermore, according to Embodiment 1, the breakdown voltage of the Zener diode 22 and the Miller voltage of the semiconductor switching element 92 are set to be equal to each other.

[0018] The complementary emitter follower circuit 30 is a circuit of an NPN transistor 31 and a PNP transistor 32 connected in series, and a connection point 33 between the emitter of the NPN transistor 31 and the emitter of the PNP transistor 32, as an output end of the complementary emitter follower circuit 30, is connected to the gate terminal of the semiconductor switching element 92.

[0019] Furthermore, a connection point 34 between the base of NPN transistor 31 and the base of PNP transistor 32 is an input end of complementary emitter follower circuit 30. The collector of NPN transistor 31 is connected to an external power supply having a power supply voltage of Vcc via a resistor. The collector of PNP transistor 32 is grounded via a resistor. In Embodiment 1, the output of complementary emitter follower circuit 30 is the output of gate driver 100.

[0020] The complementary emitter follower circuit 30 functions as an amplification circuit, amplifying at least the gate drive command output from the command generation circuit 20. The complementary emitter follower circuit 30 described above is used in Embodiment 1, but a complementary source follower circuit composed of an N-channel metal-oxide-semiconductor field-effect transistor (MOSFET) and a P-channel MOSFET may be used instead of the complementary emitter follower circuit 30.

[0021] The current limiting element 82 is arranged between the command generation circuit 20 and the connection point 83 on the electrical path L3, and by means of the electromotive voltage, it prevents current from flowing inversely from the output side and entering the command generation circuit 20. In Embodiment 1, a resistor is used as the current limiting element 82, but a coil may also be used instead of the resistor.

[0022] The semiconductor switching element 92 according to Embodiment 1 is an insulated gate bipolar transistor (IGBT) with a diode connected in anti-parallel, but it may also be a MOSFET with a diode connected between the source and drain, or a cascode-type high mobility gallium nitride transistor (GaN-HEMT). The semiconductor switching element 92 is not particularly limited.

[0023] A constant voltage signal, which is the output of the constant output circuit 10, and the gate drive command, which is the output of the command generation circuit 20, are combined at the connection point 83. The combined signal is amplified by the complementary emitter follower circuit 30 and then output as a gate drive voltage, which is the output of the gate drive device 100. The gate drive voltage is applied to the gate terminal of the semiconductor switching element 92.

[0024] Fig. 2A is a configuration diagram showing an example in which the gate driving device according to Embodiment 1 is applied to, for example, a chopper circuit of a power converter. In Fig. 2A, the semiconductor switching elements 92 and gate driving devices 100 are each illustrated as a semiconductor switching element 92A on the upper side and a gate driving device 100A on the positive side (high level side) and a semiconductor switching element 92B on the lower side and a gate driving device 100B on the negative side (low level side), respectively.

[0025] In Fig. 2A, V1 denotes the potential difference between the ground side and the high potential side of the chopper circuit. Fig. 2B is a diagram in which the semiconductor switching element 92A on the upper side and the semiconductor switching element 92B on the lower side are arranged in Fig. 2A are each replaced by MOSFETs. The circuit configurations in Fig. 2A and Fig. 2B are for a chopper circuit.

[0026] However, embodiment 1 can also be applied to a circuit in which two semiconductor switching elements are connected in series and form one leg, as in Fig. 2A and Fig. 2B. For example, Embodiment 1 can be applied to an inverter circuit composed of six elements, or it can be applied to a full-bridge circuit composed of four elements. Furthermore, both elements connected in series do not need to be semiconductor switching elements, and one of them may also be a diode element.

[0027] Next, the turn-on operation of the semiconductor switching element 92 by gate driving the gate driver 100 will be described. The input signal Vin as a gate signal is input to the gate driver 100 via the interface circuit 91. The input signal Vin is a voltage signal that changes in steps. The constant output circuit 10 and the command generation circuit 20 are connected in parallel to each other, and thus the input signal Vin is input to the respective circuits, whose outputs are combined at the connection point 83.

[0028] The constant voltage signal output from the constant output circuit 10 is determined by the input signal Vin and the resistance of the resistor 11. The command generation circuit 20 functions as a low-impedance power supply with a combination of the Zener diode 22 and the RC circuit formed by the resistor 21 and the capacitor 23. The gate drive command waveform output from the command generation circuit 20 becomes a voltage waveform with first-order delay characteristics. The specific waveform is determined by the input signal Vin and the circuit constants for the resistor 21 and the capacitor 23.

[0029] As described above, the output of the constant output circuit 10 and the output output from the command generation circuit 20 are combined at the connection point 83, and they are input to the complementary emitter follower circuit 30, and thus, the signal input to the complementary emitter follower circuit 30 and a signal transmitted from the complementary emitter follower circuit 30 to the semiconductor switching element 92 usually has the waveform of a signal with a larger output.

[0030] In Embodiment 1, a circuit constant is set so that the output of the command generation circuit 20 is larger. Consequently, the waveform of a signal input to the complementary emitter follower circuit 30 and the waveform of the drive signal transmitted to the semiconductor switching element 92 are approximately the same as the waveform of the gate drive command output from the command generation circuit 20.

[0031] In addition, as described above, the Zener diode 22 arranged in the command generation circuit 20 clamps the voltage to the predetermined breakdown voltage, and thus the output current of the constant output circuit 10 and the output current of the command generation circuit 20 satisfy the relation given by the following inequality (1). Mathematical Expression 1 {Iact>Iconst(VZ≥Vgate)Iconst≥Iact(Vgate>VZ)

[0032] In the inequality (1), Iconst denotes the output current of the constant output circuit 10, and Iact denotes the output current of the command generation circuit 20. Vgate denotes the output voltage of the gate drive device 100, and it is a gate drive voltage. Vz denotes the breakdown voltage of the Zener diode 22. Furthermore, according to Embodiment 1, as described above, the breakdown voltage of the Zener diode 22 and the Miller voltage of the semiconductor switching element 92 are set to be equal to each other. Therefore, in the case where Vmiller denotes the Miller voltage of the semiconductor switching element 92, the following equation (2) is also satisfied in Embodiment 1. Vz=Vmiller

[0033] According to inequality (1) and equation (2), when the gate drive voltage Vgate is greater than the Miller voltage Vmiller of the semiconductor switching element 92, the output current Iconst of the constant output circuit 10 becomes equal to or greater than the output current Iact of the command generation circuit 20. Even in such a case, the reverse flow of the current is suppressed by the action of the electromotive voltage of the current limiting element 82, so that the output current Iconst of the constant output circuit 10 is prevented from entering the command generation circuit 20.

[0034] That is, all the output current Iconst of the constant output circuit 10 is input to the complementary emitter follower circuit 30, so that a gate current flows to the semiconductor switching element 92, and gate driving by the constant output circuit 10 is not hindered.

[0035] Although the breakdown voltage of the Zener diode 22 and the Miller voltage Vmiller are equal to each other according to Embodiment 1, the breakdown voltage of the Zener diode 22 may be different from the power supply voltage Vcc of the external power supply for the complementary emitter follower circuit 30, more specifically, a certain voltage lower than the power supply voltage Vcc, and it does not need to be equal to the Miller voltage Vmiller.

[0036] During the turn-on operation by the gate driver 100, the output of the command generation circuit 20 causes a large current change with respect to time (dI / dt) at the start of the turn-on operation, and dI / dt gradually decreases. Consequently, the current rise is rapid, and an increase in switching loss at the start of the turn-on operation is suppressed.

[0037] After the Miller period is reached, the voltage drop is inhibited by the output of the constant output circuit 10, preventing the voltage change with respect to time (dV / dt) from becoming steeper in the voltage decrease. Accordingly, noise (noise caused by the change in the recovery voltage with respect to time) can be prevented from being generated in a pair of semiconductor switching elements in the chopper circuit or the like.

[0038] As described above, the gate drive is performed using a signal having a combination of gate drive command and constant voltage signal, so that an increase in switching loss in the turn-on process and generation of noise can be suppressed.

[0039] Next, operation waveforms in the gate driving device according to Embodiment 1 will be described. Fig. 3 schematically shows the respective operation waveforms in the gate driving device according to Embodiment 1, and the operation waveforms show a behavior in a case where the semiconductor switching element 92B is arranged on the lower side of the chopper circuit as shown in Fig. 2A is switched on.

[0040] In Fig. 3, the horizontal axis indicates time, and schematic waveforms of the input signal Vin, the output current IG1 (equal to Iact in inequality (1)) of the command generation circuit 20, the output current IG2 (equal to Iconst in inequality (1)) of the constant output circuit 10, the gate drive voltage Vgate, the voltage (collector-emitter voltage) VCE_L of the lower-side semiconductor switching element 92B, the current (collector current) IC_L of the lower-side semiconductor switching element 92B, the voltage (collector-emitter voltage) VCE_H of the upper-side semiconductor switching element 92A, and the current (collector current) IC_H of the upper-side semiconductor switching element 92A are shown.

[0041] In Fig. 3, the time when the input signal Vin rises is referred to as time t0. That is, before time t0, the input signal Vin indicates zero, or it is in a negative bias state. At this time, the semiconductor switching element 92B on the lower side is in an off state, and the semiconductor switching element 92A on the upper side is in an on state. In addition, the constant output circuit 10, the command generation circuit 20, and the gate driver 100 do not output anything.

[0042] The input signal Vin becomes positive at time t0, and consequently, the output current IG1 of the command generation circuit 20, the output current IG2 of the constant output circuit 10, and the gate drive voltage Vgate increase. Consequently, the semiconductor switching element 92B on the lower side begins the turn-on operation. At the same time, the semiconductor switching element 92A on the upper side begins the turn-off operation.

[0043] The period from time t0 to time t1 is before the Miller period. During this period, the output of the command generation circuit 20 is large, and the gate drive voltage Vgate assumes a voltage waveform with first-order delay characteristics, similar to the output of the command generation circuit 20.

[0044] In addition, during the period from time t0 to time t1, a large gate current flows in the semiconductor switching element 92B on the lower side, and the gate drive voltage Vgate exceeds the gate threshold voltage (not shown), and consequently, the current IC_L of the semiconductor switching element 92B on the lower side starts to increase sharply.

[0045] When the gate drive voltage Vgate reaches the Miller voltage Vmiller, the Zener diode 22 clamps the voltage, preventing the gate drive voltage Vgate from increasing beyond the Miller voltage. Furthermore, the output current IG1 of the command generation circuit 20 is also inhibited, and the gate current for the semiconductor switching element 92B on the lower side is also inhibited.

[0046] The period from time t1 to time t2 is the Miller period. Here, the output of the command generation circuit 20 is limited by the Zener diode 22. During this period, the output current IG2 of the constant output circuit 10 is greater than the output current IG1 of the command generation circuit 20, and gate driving is achieved primarily using the output of the constant output circuit 10. Here, the output of the constant output circuit 10 is low, and consequently, gradual gate driving is performed, and the voltage VCE_L also decreases with a gentle slope.

[0047] The period from time t2 to time t3 is after the Miller period. Here, the gate drive voltage Vgate rises to Vcc (the power supply voltage of the external power supply) solely by the output of the constant output circuit 10, and the turn-on operation of the semiconductor switching element 92B on the lower side is completed.

[0048] When time t3 is reached, the semiconductor switching element 92B on the lower side starts the turn-off operation. The turn-off operation in Embodiment 1 is the same as that in the normal constant-voltage drive.

[0049] As described above, according to Embodiment 1, in an initial period of power-on start, the gate drive is performed using the large output of the command generation circuit 20 to suppress occurrence of switching losses, and in and after the Miller period, the gate drive is performed by gradual output of the constant output circuit 10 so as to prevent the voltage change with respect to time from becoming steep in the voltage decrease and also to prevent the generation of noise.

[0050] In other words, in Embodiment 1, the generation of noise caused by the voltage change with respect to time in the voltage decrease is prevented, so that noise can be suppressed more than in the conventional configuration, and further, the occurrence of switching loss can also be suppressed.

[0051] In Embodiment 1, robustness with respect to a current change in a main circuit is also improved. A detailed description follows. Fig. 4A schematically shows operating waveforms when a main circuit carries rated current, and Fig. Figure 4B schematically shows operating waveforms when the main circuit carries a small current.

[0052] Here, "small current" refers to a current smaller than the rated current, for example, 10 A. When the main circuit carries a small current, the gate charge is small and the Miller voltage is low. That is, the Miller voltage Vmiller2 when carrying a small current is lower than the Miller voltage Vmiller1 when carrying the rated current.

[0053] Under a condition having such characteristics, in gate driving using a first-order delay driving command based on an RC oscillation circuit in a conventional configuration or a constant voltage driving, if a circuit constant is set to correspond to the case where the main circuit carries the rated current, the gate driving capability is excessively increased when the small current is carried, so that the gate driving voltage Vgate can be increased to Vcc before the Miller period is reached.

[0054] Furthermore, if the gate drive voltage Vgate is increased to Vcc before the Miller period is reached, the gate current will increase excessively during the Miller period, resulting in an increase in the voltage drop (dV / dt) of the voltage VCE_L and an increase in the voltage rise (dV / dt) of the voltage VCE_H for the paired semiconductor switching element. This increase in the voltage change over time leads to noise generation.

[0055] If the circuit constant is set to correspond to a small current, the generation of noise is suppressed, but when the rated current is carried and when a large current is carried, the gate drive capability decreases and the current rise is delayed, so that switching losses may be increased. As described above, in the conventional configuration, a change in the current in the main circuit greatly changes the gate drive capability, and it is difficult to suppress both the switching losses when the rated current is carried and when the large current is carried, and the generation of noise when the small current is carried. Here, "large current" refers to a current greater than the rated current, and it may be, for example, 50A.

[0056] In the gate driving device 100 according to Embodiment 1, the voltage of the RC oscillation circuit of the command generation circuit 20 is clamped to the Miller voltage Vmiller using the Zener diode 22. Consequently, the output current IG1 of the command generation circuit 20 is limited, and an increase in the gate driving capability is inhibited. On the other hand, the gradual output of the constant output circuit 10 is combined, so that a certain degree of gate driving capability is ensured.

[0057] Therefore, in the gate driving device 100, a change in the gate driving capability due to a change in the current in the main circuit is inhibited, and suppression of both the switching losses and the noise is achieved, so that robustness with respect to a change in the current in the main circuit is improved.

[0058] In order to achieve the above-described improved robustness, a conventional gate driving device having the RC oscillation circuit is used as a comparative example, and the differences between the operation waveforms in the comparative example and the operation waveforms in Embodiment 1 are described.

[0059] Fig. 5A shows operation waveforms according to the comparative example when a main circuit carries the large current. Fig. Fig. 5B shows operation waveforms according to Embodiment 1 when the main circuit carries the large current. Fig. 5C Operation waveforms according to the comparative example when the main circuit carries the small current. Fig. 5D shows operation waveforms according to Embodiment 1 when the main circuit carries the small current. Fig. 5A to Fig. 5D each show an analysis result obtained by analyzing the operation waveforms.

[0060] In each of Fig. 5A to Fig. 5D, operating waveforms are shown when the semiconductor switching element 92B on the lower side is in Fig. 2A and Fig. 2B is turned on, and "gate current IG" denotes a current flowing in the gate terminal of the lower-side semiconductor switching element 92B. "Gate drive command VGC" and "gate voltage VG" denote the output of the gate drive device 100 and the gate voltage (voltage between gate and emitter) of the lower-side semiconductor switching element 92B, respectively, and the gate drive command VGC corresponds to the gate drive voltage Vgate.

[0061] “High-side element voltage VH” and “high-side element current IH” denote a voltage (collector-emitter voltage) of the high-side semiconductor switching element 92A and a current (collector current) of the high-side semiconductor switching element 92A, respectively, and they correspond to VCE_H and IC_H in Fig. 3 to Fig. 4B. “Low-side element voltage VL” and “Low-side element current IL” denote the voltage (collector-emitter voltage) of the low-side semiconductor switching element 92B and the current (collector current) of the low-side semiconductor switching element 92B, respectively, and they correspond to VCE_L and IC_L in Fig. 3 to Fig. 4B.

[0062] As a condition in the above-described analysis, both the circuit constant for the RC oscillation circuit in the comparative example and the circuit constant for the RC oscillation circuit of the command generation circuit 20 in Embodiment 1 are set to correspond to the case where the main circuits carry the large current.

[0063] When looking at the waveforms in the comparison example in Fig. 5A and Fig. 5C, in the comparative example, it can be seen that the increase rate of the gate current IG when a large current is carried and the increase rate when a small current is carried are different from each other during the Miller period, and the gate drive capability is increased when a small current is carried. Therefore, in the comparative example, the change in the recovery voltage with respect to time is increased, and noise is increased, as described above.

[0064] As can be seen by comparing Fig. 5C and Fig. As can be seen from Figure 5D, in Embodiment 1, the gate current IG during the Miller period when the small current is carried can be more strongly inhibited than in the comparative example, and a change in the recovery voltage with respect to time can also be inhibited. As described above, the differences between the conventional gate drive device and that in Embodiment 1 can also be confirmed from the analysis result.

[0065] Even if a plurality of targeted semiconductor switching elements are connected in parallel to each other, the gate driving device 100 can be structured to have the same circuit configuration as that shown in Fig. 1, with respect to the gate driving means for each switching element. Embodiment 2

[0066] Next, Embodiment 2 will be described with reference to Fig. 6 to Fig. 7B. Fig. 6 is a circuit diagram showing a gate driving device according to Embodiment 2. Components that are the same as or corresponding to those shown in Fig. 1 to Fig. 5D are denoted by the same reference numerals, and their repeated description will be omitted.

[0067] A gate driver 200 includes a constant output circuit 40 different from the constant output circuit 10 of the gate driver 100. The constant output circuit 40 of the gate driver 200 includes a constant current diode 41, a constant current element, and a capacitor 42 connected in parallel, and is a constant current output circuit that outputs a constant current signal.

[0068] One end of each of the constant current diode 41 and the capacitor 42 is connected to the electrical path L1 on the ground side, and the other end is connected to the electrical path L2 on the high-potential side. The other configurations are the same as those of the gate driving device 100.

[0069] Next, the operation of the gate driving device 200 in Embodiment 2 will be described. Fig. Fig. 7A shows operation waveforms according to Embodiment 2 when the main circuit carries the large current. Fig. 7B shows the operation waveforms according to Embodiment 2 when the main circuit carries the small current. The basic operations are the same as those in Embodiment 1, and after the gate drive is mainly performed using the command generation circuit 20, the gate drive is switched to be performed using the output of the constant output circuit 40.

[0070] The constant output circuit 40 in Embodiment 2 is a constant-current output circuit, and thus the gate current IG is constant even after the gate drive is switched to be performed using the constant output circuit 40. Accordingly, the rise rate of the gate voltage VG is also constant. Since the constant output circuit 10 in Embodiment 1 is a constant-voltage output circuit, the gate current IG changes without becoming constant, especially when a small current is carried.

[0071] For example, if Fig. 5D and Fig. 7B with respect to the gate current IG during the period from 0.8 µs to 1.2 µs, in the embodiment 1 according to Fig. 5D, the gate current IG is a swell in the case of small current, but in the embodiment 2 in Fig. 7B the gate current IG remains almost the same.

[0072] When the gate current IG is constant, as in Embodiment 2, the gate drive capability is more strongly maintained, and robustness to a change in the main circuit current is high. Therefore, the robustness with respect to the main circuit current can be further improved in Embodiment 2.

[0073] Furthermore, the constant-current diode has a characteristic of small temperature dependence. This means that a change in gate drive capability due to a temperature change can also be inhibited, so the robustness with respect to temperature change is also improved in Embodiment 2. Embodiment 3

[0074] Next, Embodiment 3 will be described with reference to Fig. 8 described. Fig. Fig. 8 is a circuit diagram showing a gate driving device according to Embodiment 3. Components that are the same as or corresponding to those shown in Fig. 1 to Fig. 7B are denoted by the same reference numerals, and their descriptions are omitted. The gate drive device 300 differs from that in Embodiment 2 in that an output terminal of the constant output circuit 40 is connected to the output side of the complementary emitter follower circuit 30.

[0075] In the gate driver device 300, a current limiting element 821 and a connection point 831 are arranged on the output side of the complementary emitter follower circuit 30, in contrast to the gate driver device 100 and the gate driver device 200, in which the current limiting element 82 and the connection point 83 are arranged between the command generating circuit 20 and the complementary emitter follower circuit 30.

[0076] Connection point 831 is arranged between current limiting element 821 and the gate terminal of semiconductor switching element 92. At connection point 831, constant output circuit 40 is connected to the output side of complementary emitter follower circuit 30.

[0077] In Embodiment 3, a resistor is used as the current limiting element 821. The other configurations are the same as those of the gate driving device 200. Between Embodiments 1 and 2 and Embodiment 3, the difference is whether the output of the constant output circuit 10 or the constant output circuit 40 and the output of the command generation circuit 20 are combined on the input side or the output side of the complementary emitter follower circuit 30, but the basic operations are similar to each other.

[0078] In the gate drive device 300, since the output terminal of the constant output circuit 40 is connected between the gate terminal of the semiconductor switching element 92 and the current limiting element 821 of the complementary emitter follower circuit 30, after the gate drive voltage Vgate becomes greater than the Miller voltage Vmiller of the semiconductor switching element 92, the reverse flow of current is suppressed by the action of the electromotive voltage of the current limiting element 821, and thus the complementary emitter follower circuit 30 can be prevented from absorbing current. Consequently, the constant output circuit 40 can maintain normal operation, and the effect of Embodiment 1 and Embodiment 2 can be achieved.

[0079] In Embodiment 3, the resistor is used as the current limiting element, but a coil may also be used as the current limiting element, as in a modification of Embodiment 3, as shown in Fig. 9. In a gate driver device 301, the current limiting element 821 of the gate driver device 300 is replaced by a current limiting element 822, which is a coil. Embodiment 4

[0080] Next, Embodiment 4 will be described with reference to Fig. 10 and Fig. 11 described. Fig. 10 is a circuit diagram showing a gate driving device according to Embodiment 4. Components that are the same as or corresponding to those shown in Fig. 1 to Fig. 9 are denoted by the same reference numerals, and their repeated description will be omitted. The gate driver device 400 includes a command generation circuit 50 that is different from the command generation circuit 20 of the gate driver device 200.

[0081] That is, the command generation circuit 20 includes the RC oscillation circuit formed by a resistor and a capacitor, but the command generation circuit 50 includes a constant current output circuit formed by a constant current element and a capacitor. The command generation circuit 50 is formed by a series circuit arrangement of a Zener diode 22 and a constant current diode 51, the diode 29, and the capacitor 23, which are connected in parallel with each other.

[0082] The constant current diode 51 is arranged between the ground-side electrical path L1 and the high-potential-side electrical path L3, and is connected to the cathode of the high-potential-side Zener diode 22. The capacitor 23 and the diode 29 are the same as those in Embodiment 2. The output of the command generation circuit 50 is input to the complementary emitter follower circuit 30 via the current limiting element 82 and the connection point 83, as in Embodiment 2. The other configurations are the same as those of the gate drive device 200.

[0083] Next, the operation of the gate driving device 400 according to Embodiment 4 will be described. Fig. Figure 11 shows operation waveforms according to Embodiment 4 when a main circuit carries a large current. The basic operations are the same as those in Embodiment 2. However, when the gate drive command VGC and the gate voltage VG increase, the rising waveform in Embodiment 2 is a parabola as shown in Fig. 7A, but the gate drive command VGC and the gate voltage VG increase linearly in Embodiment 4.

[0084] In the case where the gate drive command VGC and the gate voltage VG increase linearly, even if the Miller voltage changes due to a change in the main circuit current, a certain gate drive capability is maintained. Consequently, the robustness to a change in the main circuit current is improved more in Embodiment 4 than in Embodiment 2.

[0085] In addition, the constant-current diode has a smaller temperature dependence than the resistor. Consequently, robustness to temperature changes is also further improved.

[0086] Although the invention described above is described in terms of various exemplary embodiments and implementations, it should be understood that various features, aspects, and functions described in one or more of the individual embodiments are not limited in their applicability to the particular embodiment with which they are described, but instead are applied alone or in various combinations to one or more embodiments of the invention.

[0087] It should therefore be understood that numerous modifications not described by way of example may be employed without departing from the technical scope of the description of the present invention. For example, at least one of the components may be modified, added, or omitted. At least one of the components described in at least one of the preferred embodiments may be selected and combined with the components explained in another preferred embodiment. List of reference symbols 10, 40 Constant output circuit 11, 21 Resistance 20, 50 Command generation circuit 22 Zener diode 23, 42 capacitor 30 complementary emitter follower circuit 83, 831 connection point 41, 51 constant current diode 29, 81 Diode 82 Current limiting element 821, 822 current limiting element 92 semiconductor switching element 92A semiconductor switching element on the upper side 92B Semiconductor switching element on the lower side 100, 100A, 100B, 200, 300, 301, 400 Gate driver device Vin input signal QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2004

[0004] JP 48 959 A

[0004]

Claims

[1] Gate driver device comprising: a command generation circuit that generates and outputs a gate drive command based on an input signal; a constant output circuit connected in parallel with the command generation circuit and outputting a constant voltage signal or a constant current signal based on the input signal; an amplification circuit that amplifies the gate drive command; and a current limiting element arranged on the input side or the output side of the amplifying circuit and suppressing the reverse flow of the current, wherein the gate driving means applies a gate driving voltage obtained by combining the gate driving command and the constant voltage signal or the constant current signal to the gate terminal of a semiconductor switching element. [2] The gate driving device according to claim 1, wherein the command generating circuit includes a constant voltage element to clamp a voltage at a certain voltage lower than a power supply voltage of the boosting circuit so that the gate driving command is maintained at the certain voltage. [3] A gate driving device according to claim 1 or 2, wherein the command generating circuit comprises an RC oscillation circuit formed of a capacitor and a resistor connected in parallel with each other. [4] A gate driving device according to claim 1 or 2, wherein, when a gate voltage of the semiconductor switching element increases, the command generating circuit controls the change of the gate voltage with respect to time to be constant. [5] A gate driving device according to claim 1 or 2, wherein the command generating circuit comprises a constant current element and a capacitor connected in parallel with each other. [6] A gate driving device according to any one of claims 1 to 5, wherein the current limiting element is arranged between the command generating circuit and the input side of the amplifying circuit, and wherein a connection point to which an output end of the constant output circuit is connected is arranged between the current limiting element and the input side of the amplifying circuit. [7] A gate driving device according to any one of claims 1 to 5, wherein the current limiting element is arranged between the output side of the amplifying circuit and the gate terminal, and a connection point to which an output end of the constant output circuit is connected is arranged between the current limiting element and the gate terminal. [8] A gate driver device according to any one of claims 1 to 7, wherein the current limiting element comprises at least one of a resistor or a coil. [9] A gate driving device according to claim 2, wherein in a case where the output current of the constant output circuit is denoted by Iconst, the output current of the command generating circuit is denoted by Iact, the gate driving voltage is denoted by Vgate, and the certain voltage is denoted by Vz, the inequality (1) is satisfied. Mathematical Expression 1 {Iact>Iconst(VZ≥Vgate)Iconst≥Iact(Vgate>VZ) [10] A gate driving device according to claim 2 or 9, wherein the constant voltage element is a Zener diode whose breakdown voltage is the certain voltage. [11] A gate driving device according to any one of claims 2, 9 and 10, wherein the certain voltage is equal to the Miller voltage of the semiconductor switching element. [12] A gate driving device according to any one of claims 1 to 11, wherein the amplifying circuit is a complementary emitter follower circuit or a complementary source follower circuit.

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