Drive circuit

Abstract

The present application aims to provide a drive circuit capable of improving the accuracy of a shield time. The drive circuit includes a first diode, a first transistor and a second transistor which become off when the first diode is off and become on when the first diode is on, a first capacitor, and a control unit which controls whether to output a pulse signal to a switching element. In the case where the switching element is on and the voltage between the collector and the emitter of the switching element is equal to or greater than a first predetermined voltage value, the first diode becomes on, and the first transistor and the second transistor become on. After the shield time in which the charging of the first capacitor with current from a current source is started and the voltage across the first capacitor becomes equal to or greater than a second predetermined voltage value which is greater than the first predetermined voltage value, an abnormality detection signal is output to the control unit, and the control unit stops outputting the pulse signal to the switching element based on the abnormality detection signal.

Description

Technical Field

[0001] This invention relates to a driving circuit. Background Technology

[0002] Insulated-gate bipolar transistors (IGBTs), which handle high-voltage, high-current switching, can cause significant disruption to surrounding equipment if damaged by overcurrent due to short circuits in the connected load. Therefore, it is crucial to prevent such damage in the IGBT drive circuit. One method for detecting abnormal overcurrent flow caused by short circuits in the load is to detect the rise in Vce (collector-emitter voltage) when the IGBT is ON. In these existing methods, a certain period is sometimes set after the abnormality detection until an abnormality detection signal is sent. This period, known as the shielding time, is the time spent waiting for the abnormality detection signal to be sent. From the viewpoint of preventing false detections and preventing IGBT overload, the shielding time requires a certain level of precision.

[0003] Figure 12 This is a circuit diagram of a drive circuit for an IGBT 912 using a gate driver 900 based on existing technology. (For example...) Figure 12 As shown, the gate driver 900 includes an inverter 916, a comparator 918, a transistor Q901, and a current source Idesat. A voltage Vdd is supplied to the current source Idesat. Additionally, a capacitor Cdesat, a snubber circuit 920, a diode Ddesat, and an IGBT 912 are connected to the gate driver 900. Furthermore, a reference voltage Vdesatth is input to one end of the input terminal of the comparator 918. Additionally, an alternating high-level (Vgatehigh, VGH) and low-level (Vgatelow, VGL) pulse signal is input from the output (OUT) terminal 914 of the gate driver 900.

[0004] Here, the operation of the IGBT 912 during its normal repeated turn-on and turn-off operations is explained. During the turn-off operation of the IGBT 912, the output value of the OUT terminal 914 is low, and the transistor Q901 of the gate driver 900 is turned on, discharging the charge of the capacitor Cdesat to 0. When the IGBT 912 turns on, the value of the OUT terminal 914 is high, therefore, a low-level signal is input to the base of the transistor Q901 via the inverter 916. As a result, although the transistor Q901 turns off, since the Vce voltage of the IGBT 912 becomes the saturation voltage, the current from the current source Idesat flows to the collector terminal of the IGBT 912 via the diode Ddesat.

[0005] As a result, capacitor Cdesat is charged to a voltage equal to the sum of the forward voltage of diode Ddesat based on current source Idesat and the saturation voltage between the collector and emitter of IGBT 912. That is, the terminal voltage of capacitor Cdesat becomes the saturation voltage plus the forward voltage of diode Ddesat. Because the voltage at the short-circuit time (DESAT) terminal of gate driver 900 remains lower than the reference voltage Vdesatth, comparator 918 does not invert the value of its output signal, and therefore does not output an abnormality detection signal.

[0006] When an abnormality occurs in the load connected to IGBT 912, causing current to flow through IGBT 912 and the Vce voltage to rise to the positive-side power supply Vcc level, diode Ddesat becomes cut off. Then, current from current source Idesat flows into capacitor Cdesat, causing the voltage across capacitor Cdesat to rise to the reference voltage Vdesatth. As a result, comparator 918 inverts its output value and outputs an abnormality detection signal. Furthermore, when the voltage across capacitor Cdesat is higher than the reference voltage Vdesatth, the output signal of comparator 918 becomes high, indicating an abnormality detection signal. A shielding time Tw is set from the occurrence of an abnormality in the load connected to IGBT 912 until the gate driver 900 outputs the abnormality detection signal. The gate driver 900 outputs the abnormality detection signal to an external device (not shown). Based on the input abnormality detection signal, the external device switches the gate signal of IGBT 912 to a low level. Regarding the shielding time Tw, it is approximately 6.9 μs when the inductance of the load connected to the IGBT 912 is small (approximately 200 nH) during a short circuit, and approximately 1.0 μs when the inductance of the load is large (approximately 8 nH) during a short circuit. Furthermore, when the load is short-circuited, diode Ddesat is open, and the signal from the DESAT terminal flows to capacitor Cdesat.

[0007] [Existing technical documents]

[0008] [Patent Literature]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 2004-140891 Summary of the Invention

[0010] [The problem the invention aims to solve]

[0011] In such existing drive circuits, there is a problem that the shielding time, intended to prevent false detection, varies depending on the load conditions during a short circuit.

[0012] The present invention is made in view of the aforementioned problems, and its purpose is to provide a drive circuit that can improve the accuracy of shielding time.

[0013] [Technical means to solve the problem]

[0014] (1) In order to achieve the above objective, one embodiment of the driving circuit of the present invention is a driving circuit for driving the switching element 41 using a pulse signal, which includes: a first diode D22; a first transistor Q21 and a second transistor Q22, which are in a turned-off state when the first diode is in a turned-on state and in a turned-on state when the first diode is in a turned-on state; a first capacitor (Cdesat); and a control unit 30, which controls whether to output the pulse signal to the switching element; when the switching element is in a turned-on state and the collector-emitter voltage of the switching element is above a first predetermined voltage value, the first diode is turned on, the first transistor and the second transistor are turned on, and after a shielding time when the first capacitor is charged with current from the current source and the voltage value at both ends is above a second predetermined voltage value greater than the first predetermined voltage value, an abnormality detection signal is output to the control unit, and the control unit stops outputting the pulse signal to the switching element according to the abnormality detection signal.

[0015] (2) In order to achieve the above objective, one embodiment of the driving circuit of the present invention is a driving circuit for driving the switching element 41 using a pulse signal, which includes: a first diode D22; a first transistor Q23; a second transistor Q22C; a first capacitor (Cdesat); and a control unit 30, which controls whether to output the pulse signal to the switching element; when the switching element is in the on state and the collector-emitter voltage of the switching element is above a first predetermined voltage value, the first diode becomes in the on state, the first transistor becomes in the off state, and the second transistor becomes in the on state. After the first capacitor is charged with current from the current source and the voltage value at both ends becomes above a second predetermined voltage value greater than the first predetermined voltage value for a shielding time, an abnormality detection signal is output to the control unit, and the control unit stops outputting the pulse signal to the switching element according to the abnormality detection signal.

[0016] (3) In addition, in the driving circuit of one embodiment of the present invention, when the switching element is in the on state and the collector-emitter voltage of the switching element is less than the first predetermined voltage value, the first diode is in the off state, the first transistor and the second transistor are in the off state, and after a shielding time when the voltage value across the current from the current source reaches a third predetermined voltage value that is different from the first predetermined voltage value and the second predetermined voltage value, the abnormal detection signal is output to the control unit.

[0017] (4) In addition, in the driving circuit of one embodiment of the present invention, when the switching element is in the on state and the collector-emitter voltage of the switching element is less than the first predetermined voltage value, the first diode and the second transistor are in the off state, the first transistor is in the on state, and after the voltage value across the current from the current source reaches a third predetermined voltage value that is different from the first predetermined voltage value and the second predetermined voltage value for a shielding time, the abnormal detection signal is output to the control unit.

[0018] (5) In addition, in a driving circuit according to one embodiment of the present invention, the base of the first transistor Q21 is connected to one end of the second resistor R202 and one end of the third resistor R203, the other end of the third resistor is connected to the collector of the second transistor Q22, the emitter of the second transistor is grounded, and the base is connected to one end of the fourth resistor R204 and one end of the fifth resistor R205, the other end of the fourth resistor is grounded, the other end of the fifth resistor is connected to the anode of the first diode D22, and the cathode of the first diode is connected to one end of the sixth resistor R206 and the second diode ( The anode of the first diode (Ddesat) is connected, the other end of the sixth resistor is connected to the cathode of the third diode (D23), the emitter of the first transistor, and the other end of the second resistor. The cathode of the second diode is connected to the collector of the switching element. The pulse signal is input to the anode of the third diode. One end of the first capacitor (Cdesat) is connected to the current source (Idesat) and the anode of the fourth diode (D21), and the other end is grounded. The cathode of the fourth diode is connected to one end of the first resistor (R201) and the collector of the first transistor. The other end of the first resistor is grounded.

[0019] (6) In addition, in a driving circuit according to one embodiment of the present invention, the base of the first transistor Q21 is connected to one end of the second resistor R202 and one end of the third resistor R203, and the emitter is connected to a positive voltage (Vcc1). The other end of the second resistor is connected to the positive voltage, and the other end of the third resistor is connected to the collector of the second transistor Q22. The emitter of the second transistor is grounded, and the base is connected to one end of the fourth resistor R204 and one end of the fifth resistor R205. The other end of the fourth resistor is grounded, and the other end of the fifth resistor is connected to the first... The anode of diode D22 is connected, the cathode of the first diode is connected to one end of the sixth resistor R206 and the anode of the second diode (Ddesat), the other end of the sixth resistor is connected to the positive voltage, the cathode of the second diode is connected to the collector of the switching element 41, one end of the first capacitor (Cdesat) is connected to the current source (Idesat) and the anode of the third diode D23, and the other end is grounded, the cathode of the third diode is connected to one end of the first resistor R201 and the collector of the first transistor, and the other end of the first resistor is grounded.

[0020] (7) In addition, in a driving circuit according to one embodiment of the present invention, one end of the first capacitor (Cdesat) is connected to the current source (Idesat) and the first resistor R211, and the other end is grounded; the other end of the first resistor is connected to the collector of the first transistor Q23; the emitter of the first transistor is grounded, and the base is connected to one end of the second resistor R212 and one end of the third resistor R213; the other end of the third resistor is grounded; the emitter of the second transistor Q22C is grounded, and the base is connected to one end of the fourth resistor R204 and one end of the fifth resistor R205. The fourth resistor is connected to the ground, the other end of the fifth resistor is connected to the anode of the first diode D22, the cathode of the first diode is connected to one end of the sixth resistor R206 and the anode of the second diode (Ddesat), the other end of the sixth resistor is connected to the cathode of the third diode D23 and one end of the seventh resistor R217, the other end of the seventh resistor is connected to the other end of the second resistor and the collector of the second transistor, the cathode of the second diode is connected to the collector of the switching element, and the pulse signal is input to the anode of the third diode.

[0021] (8) In addition, in a driving circuit according to an embodiment of the present invention, one end of the first capacitor (Cdesat) is connected to the current source (Idesat) and one end of the first resistor R211, and the other end is grounded. The other end of the first resistor is connected to the collector of the first transistor Q23. The emitter of the first transistor is grounded, and the base is connected to one end of the second resistor R212 and one end of the third resistor R213. The other end of the third resistor is grounded. The emitter of the second transistor Q22C is grounded, and the base is connected to one end of the fourth resistor R204 and one end of the fifth resistor R205. The other end of the fourth resistor is grounded. The other end of the fifth resistor is connected to the anode of the first diode D22. The cathode of the first diode is connected to one end of the sixth resistor R206D and the anode of the second diode (Ddesat). The other end of the sixth resistor is connected to the positive voltage (Vcc1). One end of the seventh resistor R217D is connected to the positive voltage, and the other end is connected to the other end of the second resistor and the collector of the second transistor. The cathode of the second diode is connected to the collector of the switching element 41.

[0022] [The effects of the invention]

[0023] According to the present invention, the accuracy of shielding time can be improved. Attached Figure Description

[0024] Figure 1 This is a circuit diagram of the driving circuit for the implementation method.

[0025] Figure 2 This is a diagram illustrating an example of the operation of the drive circuit in the implementation method.

[0026] Figure 3 This is a circuit diagram of the driving circuit in the first embodiment.

[0027] Figure 4 This is a circuit diagram of the driving circuit in the second embodiment.

[0028] Figure 5 This is a diagram showing the simulated waveforms in the first and second embodiments when the inductance of the load is small during a short circuit.

[0029] Figure 6 This is a diagram showing the simulated waveforms in the first and second embodiments when the load inductance is large during a short circuit.

[0030] Figure 7 This is a circuit diagram of the driving circuit in the third embodiment.

[0031] Figure 8 This is a circuit diagram of the driving circuit in the fourth embodiment.

[0032] Figure 9 This is a diagram showing the operating states of each component in the first to fourth embodiments.

[0033] Figure 10 This is a diagram showing the simulated waveforms in the third and fourth embodiments when the inductance of the load is small during a short circuit.

[0034] Figure 11 This is a diagram showing the simulated waveforms in the third and fourth embodiments when the load inductance is large during a short circuit.

[0035] Figure 12 This is a circuit diagram of a gate driver driving IGBT based on existing technology.

[0036] [Explanation of Symbols]

[0037] 1, 1A, 1B, 1C, 1D: Drive circuits

[0038] 10: Driver

[0039] 20, 20A, 20B, 20C, 20D: DESAT circuit

[0040] Q11, Q21, Q22, Q21B, Q22C: Transistors

[0041] 12: Comparator

[0042] 13: Inverter

[0043] 14: Output terminals

[0044] Idesat: Current source

[0045] Cdesat, C21: Capacitors

[0046] D21, D22, D23, Ddesat: Diodes

[0047] R201, R202, R203, R204, R206D: Resistors

[0048] 30: Control Department

[0049] 31: Buffer

[0050] 41: Switching element Detailed Implementation

[0051] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0052] Figure 1 This is a circuit diagram of the driving circuit in this embodiment. (For example...) Figure 1As shown, the drive circuit 1 includes a driver 10, a short-circuit time limiting (DESAT) circuit 20, and a control unit 30.

[0053] The driver 10 includes a transistor Q11, a comparator 12, an inverter 13, an output terminal 14, a current source Idesat, a DESAT terminal, an OUT terminal, and a ground (GND) terminal.

[0054] DESAT circuit 20 includes capacitor Cdesat (first capacitor), diode D21 (fourth diode), transistor Q21 (first transistor), resistor R201 (first resistor), resistor R202 (second resistor), resistor R203 (third resistor), transistor Q22 (second transistor), capacitor C21, resistor R204 (fourth resistor), resistor R205 (fifth resistor), diode D22 (first diode), diode D23 (third diode), resistor R206 (sixth resistor), buffer 31, diode D32, and diode Ddesat (second diode). Circuit block 21 includes diode D21, transistor Q21, resistors R201, R202, R203, transistor Q22, capacitor C21, resistors R204, R205, diode D22, and resistor R206. Furthermore, circuit block 21 will be described later.

[0055] also, Figure 1 The circuit shown is an example; the drive circuit 1 may also include other components (such as capacitors for noise removal).

[0056] The driving circuit 1 drives the switching element 41. The switching element 41 is, for example, an IGBT. Alternatively, the switching element 41 can be other power semiconductors (e.g., metal-oxide-semiconductor field-effect transistors, MOSFETs).

[0057] The driver 10 is, for example, a driver integrated circuit (IC) that drives the switching element 41. Furthermore, in the event of an abnormality in the load connected to the switching element 41, the driver 10 outputs an abnormality detection signal to the control unit 30 after a shielding time described later. Then, the driver 10 switches the gate level of the switching element 41 to a low level according to the control of the control unit 30.

[0058] The DESAT circuit 20 is a protection circuit that cuts off the gate based on the rise in voltage between the collector and emitter of the switching element 41 when current flows due to a short circuit in the load.

[0059] The control unit 30 controls whether to output a pulse signal to the switching element 41. When an abnormality detection signal is received from the driver 10, the control unit 30 controls the driver 10 to switch the gate level of the switching element 41 to a low level. Furthermore, the driver 10 may include the control unit 30.

[0060] Next, the connection relationships of the drive circuit 1 will be explained. First, the connection relationships of the driver 10 will be explained.

[0061] In comparator 12, a reference voltage Vdesatth (a second specified voltage value) is connected to the first input terminal, and a current source Idesat, the DESAT terminal, and the collector of transistor Q11 are connected to the second input terminal. Furthermore, a voltage Vdd is supplied to the current source Idesat. The emitter of transistor Q11 is connected to the GND terminal, and its base is connected to the output terminal of inverter 13. The input terminals of inverter 13 are connected to output terminal 14 and the OUT terminal. A pulse signal alternating between high-level (VGH) and low-level (VGL) signals is input to output terminal 14. Transistor Q11 is a negative-positive-negative (NPN) type transistor.

[0062] Furthermore, the current output from the current source Idesat is, for example, several hundred (μA), and the voltage value of the reference voltage Vdesatth is, for example, several (V). Additionally, the voltage values ​​output from the OUT terminal of driver 10 are, for example, VGL is 0 (V) and VGH is in the teens (V).

[0063] Next, the connection relationship of the DESAT circuit 20 will be explained.

[0064] One end of capacitor Cdesat is connected to the DESAT terminal (current source) of driver 10 and the anode of diode D21, and the other end is grounded. The cathode of diode D21 is connected to one end of resistor R201 and the collector of transistor Q21. The other end of resistor R201 is grounded. The anode of diode D23 is connected to the OUT terminal of driver 10 and the input terminal of buffer 31. The emitter of transistor Q21 is connected to one end of resistor R202, the cathode of diode D23, and one end of resistor R206, and the base is connected to the other end of resistor R202 and one end of resistor R203. The other end of resistor R203 is connected to the collector of transistor Q22.

[0065] The emitter of transistor Q22 is grounded, and its base is connected to one end of capacitor C21, one end of resistor R204, and one end of resistor R205. The other end of capacitor C21 and the other end of resistor R204 are grounded. The other end of resistor R205 is connected to the anode of diode D22. The cathode of diode D22 is connected to the cathode of diode D32, the anode of diode Ddesat, and the other end of resistor R206. The anode of diode D32 is grounded. The cathode of diode Ddesat is connected to the collector of switching element 41.

[0066] Diode D22 is, for example, a Zener diode. Transistor Q21 is a positive-negative-positive (PNP) transistor. Transistor Q22 is an NPN transistor. Diode Ddesat can be, for example, a diode array containing multiple diodes, or multiple diodes connected in series.

[0067] Furthermore, the forward voltage VF of diode Ddesat is, for example, about 1.5 (V), and the Zener voltage of diode D22 is, for example, a dozen (V).

[0068] The gate of the switching element 41 is connected to the output terminal of the buffer 31, supplies power Vcc to the collector, and the emitter is grounded. Furthermore, the voltage value of the power supply Vcc is, for example, several hundred volts.

[0069] In addition, such as Figure 12 As shown, in the existing DESAT circuit, the DESAT terminal is directly connected to one end of the capacitor Cdesat and the anode of the diode Ddesat.

[0070] Next, the operation of drive circuit 1 will be explained.

[0071] Figure 2 This is a diagram illustrating an example of the operation of the drive circuit in this embodiment.

[0072] Diode D22 operates as a switching element based on the voltage across its terminals. Resistors R202 and R203 operate as a voltage divider circuit for the voltage applied to the base of transistor Q21. Resistors R204 and R205 operate as a voltage divider circuit for the voltage applied to the base of transistor Q22. Resistor R201 suppresses voltage to a level not exceeding the reference voltage Vdesatth of driver 10. Resistor R206 controls current to prevent excessive flow. Transistors Q21 and Q22 control the charging and discharging of capacitor Cdesat. Capacitor C21 is used for noise reduction.

[0073] During the period when switching element 41 is off (turn-off control), i.e., when the output from the OUT terminal of driver 10 is low (VGL), since the output of buffer 31 is low, switching element 41 is off, and the collector voltage of switching element 41 becomes high. Therefore, during this period, in DESAAT circuit 20, diode D22 is off, and transistors Q21 and Q22 are also off. Then, driver 10 causes current to flow from current source Idesat to transistor Q11 without outputting from the DESAAT terminal to DESAAT circuit 20. As a result, the voltage across capacitor Cdesat is approximately 0 (V) (line g11). Furthermore, during the period when switching element 41 is off (turn-off control), transistor Q11 of driver 10 is on.

[0074] Thus, in this embodiment, when the switching element 41 is on and Vce is less than the first predetermined voltage value (normal operation), diode D22 is off, and transistor Q21 is off, thereby setting the DESAT terminal to 0 (V). Furthermore, when the switching element 41 is on and Vce is less than the first predetermined voltage value (normal operation), transistor Q11 of the driver 10 is off. As a result, according to this embodiment, the initial voltage of capacitor Cdesat is fixed at 0 (V). Therefore, according to this embodiment, the initial charge of capacitor Cdesat, which determines the time constant, can be controlled, reducing variations in shielding time.

[0075] During the period when switching element 41 is turned on (conduction control), that is, during the period when the output from the OUT terminal of driver 10 is at a high level (VGH), switching element 41 is in the conducting state because the output of buffer 31 is at a high level. Additionally, during this period, a voltage is applied to the emitter of transistor Q21 and resistor R202, and a voltage is applied to resistor R206 via diode D23. During this period, when the Vce of switching element 41 is less than the first predetermined voltage value and is normal, in the DESAT circuit 20, diode D22 is in the off state, and transistors Q21 and Q22 are also off. Therefore, driver 10 outputs the current supplied from current source Idesat to the DESAT terminal. Then, the current output from the DESAT terminal of driver 10 is charged to capacitor Cdesat of DESAT circuit 20 until the third predetermined voltage value of equation (1) is reached (line g12).

[0076] [Formula 1]

[0077] Cdesat charging voltage = D21_VF + (Idesat × R201)…(1)

[0078] Furthermore, in equation (1), D21_VF is the forward voltage VF of diode D21, Idesat is the current value of current source Idesat, and R201 is the resistance value of resistor R201.

[0079] During the period when the switching element 41 is turned on, and when the voltage Vce of the switching element 41 abnormally rises above the first predetermined voltage value, in the DESAT circuit 20, due to the rise in the voltage on the anode side of the diode Ddesat, the diode D22 becomes in the conducting state, and the transistors Q21 and Q22 become in the conducting state. With the transistor Q21 in the conducting state, the diode D21 becomes in the off state. Then, the capacitor Cdesat begins to charge with the current output from the DESAT terminal of the driver 10, and when it reaches the reference voltage Vdesatth (the second predetermined voltage value) or above, the charging operation stops (line g13). In addition, when the switching element 41 is turned on and the voltage Vce abnormally rises above the first predetermined voltage value, the transistor Q11 of the driver 10 is in the off state. Then, after the shielding time Tw when the capacitor Cdesat reaches the third predetermined voltage value, the driver 10 outputs an abnormality detection signal to the control unit 30, and switches the gate level of the switching element 41 to a low level according to the control of the control unit 30. In addition, the shielding time Tw is determined by the following formula (2). Furthermore, the second specified voltage value is greater than the third specified voltage value. Additionally, the first specified voltage value is a voltage value based on the characteristics of the switching element 41.

[0080] [Formula 2]

[0081]

[0082] Furthermore, in equation (2), Vdesatth is the reference voltage value, D21_VF is the forward voltage VF of diode D21, Idesat is the current value of current source Idesat, and R201 is the resistance value of resistor R201.

[0083] As shown in equation (2), a certain shielding time Tw can be achieved according to this embodiment. Furthermore, in this embodiment, the shielding time can be arbitrarily selected based on the forward voltage VF of diode D21 and the resistance value of resistor R201. Therefore, a larger margin for false detection of noise, etc., can be achieved. Thus, according to this embodiment, the shielding time Tw from the occurrence of an abnormality in the load connected to the switching element 41 to the output of an abnormality detection signal by the driver 10 can be fixed.

[0084] Here, the function of diode D21 will be explained.

[0085] exist Figure 1In this circuit, when transistor Q21 is turned on, the voltage on the cathode side of diode D21 may sometimes become high. In this case, the voltage on the cathode side of diode D21 may exceed the withstand voltage of the DESAT terminal of driver 10. Therefore, diode D21 is used to protect the DESAT terminal of driver 10. Alternatively, if the withstand voltage of the DESAT terminal of driver 10 is high, the DESAT circuit 20 may not include diode D21.

[0086] Based on the above structure, in this embodiment, the accuracy of the shielding time can be improved through a simple circuit structure. Furthermore, the simulation results will be described later.

[0087] <First Embodiment>

[0088] Next, the first embodiment will be described. Figure 3 This is a circuit diagram of the driving circuit in the first embodiment. Figure 3 As shown, the drive circuit 1A includes a driver 10 and a DESAT circuit 20A.

[0089] The DESAT circuit 20A includes a capacitor Cdesat (first capacitor), a diode D21 (fourth diode), a transistor Q21 (first transistor), a resistor R201 (first resistor), a resistor R202 (second resistor), a resistor R203 (third resistor), a transistor Q22 (second transistor), a resistor R204 (fourth resistor), a resistor R205 (fifth resistor), a diode D22 (first diode), a diode D23 (third diode), a resistor R206 (sixth resistor), a buffer 31, and a diode Ddesat (second diode).

[0090] Figure 9 This is a diagram showing the operating states of each component in the first to fourth embodiments. Figure 3 The operation of the drive circuit 1A is as follows: Figure 9 Table g501 shows the relationship with Figure 1 The driving circuit is the same as that of 1.

[0091] like Figure 1 as well as Figure 3 As shown, the DESAT circuit 20A does not include the capacitor C21 included in the DESAT circuit 20. Therefore, the DESAT circuit 20 may also omit the capacitor C21. Furthermore, in Figure 3 A diode Ddesat is represented by a single diode, but a diode Ddesat can also contain multiple diodes.

[0092] <Second Embodiment>

[0093] Next, the second embodiment will be described. Figure 4This is a circuit diagram of the driving circuit in the second embodiment. (For example...) Figure 4 As shown, the drive circuit 1B includes a driver 10 and a DESAT circuit 20B.

[0094] The DESAT circuit 20B includes a capacitor Cdesat (first capacitor), a diode D21 (fourth diode), a transistor Q21B (first transistor), a resistor R201 (first resistor), a resistor R202B (second resistor), a resistor R203 (third resistor), a transistor Q22 (second transistor), a resistor R204 (fourth resistor), a resistor R205 (fifth resistor), a diode D22 (first diode), a resistor R206B (sixth resistor), a buffer 31, and a diode Ddesat (second diode).

[0095] like Figure 4 As shown, relative to Figure 3 The DESAT circuit 20B does not include diode D23, but a positive voltage Vcc1 is connected to the emitter of transistor Q21B and resistors R202B and R206B. Furthermore, the value of the positive voltage Vcc1 is, for example, in the tens of volts (V).

[0096] In the first embodiment, the DESAT circuit 20A applies voltage to the emitter of transistor Q21, resistor R202, and resistor R206 during the period when the pulse signal is high. However, in the second embodiment, the DESAT circuit 20B supplies voltage to the emitter of transistor Q21, resistor R202B, and resistor R206B regardless of the level of the pulse signal.

[0097] like Figure 9 As shown in Table g502, when the switching element 41 is off, in the DESAT circuit 20B of the second embodiment, diode D22 is in the on state, transistors Q21B and Q22 are in the on state, and transistor Q11 of driver 10 is in the on state.

[0098] like Figure 9 As shown in Table g502, when the switching element 41 is turned on and Vce is less than the first predetermined voltage value and is in normal condition, in the DESAT circuit 20B of the second embodiment, diode D22 is in the off state, transistors Q21B and Q22 are in the off state, and transistor Q11 of driver 10 is in the off state. Moreover, the current output from the DESAT terminal of driver 10 is charged to capacitor Cdesat of DESAT circuit 20B until the third predetermined voltage value of equation (1) is reached.

[0099] like Figure 9As shown in Table g502, when the switching element 41 is turned on and Vce abnormally rises above the first predetermined voltage value, in the DESAT circuit 20B, diode D22 becomes on, transistors Q21B and Q22 become on, and transistor Q11 of the driver 10 becomes off. Then, capacitor Cdesat begins to charge from the current output from the DESAT terminal of the driver 10, and stops charging when it reaches the reference voltage Vdesatth (the second predetermined voltage value). Then, after the shielding time Tw when capacitor Cdesat reaches the third predetermined voltage value, the driver 10 outputs an abnormality detection signal to the control unit 30, and switches the gate level of the switching element 41 to a low level according to the control of the control unit 30. Furthermore, the shielding time Tw is determined by equation (2).

[0100] Next, regarding the structures of the first and second embodiments, we will explain the simulation results of the waveforms.

[0101] Figure 5 This is a diagram showing the simulated waveforms in the first and second embodiments when the load inductance is small during a short circuit. Figure 5 In the diagram, the horizontal axis represents time (μs), and the vertical axis represents voltage (V) and current (A). Waveform g101 is the waveform of the current Ic flowing through the collector of switching element 41. Waveform g102 is the waveform of the gate voltage Vge of switching element 41. Waveform g103 is the waveform of the VDESAT voltage at the DESAT terminal. Waveform g104 is the waveform of the collector-emitter voltage Vce of switching element 41. Furthermore, the desaturation state refers to the state where switching element 41 is not saturated.

[0102] like Figure 5 As shown, the shielding time Tw1 is approximately 4.6 (μs) when the load inductance is small during a short circuit.

[0103] Figure 6 This is a diagram showing the simulated waveforms in the first and second embodiments when the load inductance is large during a short circuit. Figure 6 In the diagram, the horizontal axis represents time, and the vertical axis represents the voltage (V) and current (A). Waveform g201 is the waveform of current Ic. Waveform g202 is the waveform of gate voltage Vge. Waveform g203 is the waveform of VDESAT voltage. Waveform g204 is the waveform of voltage Vce.

[0104] like Figure 6 As shown, the shielding time Tw2 is approximately 4.5 (μs) when the load inductance is large during a short circuit.

[0105] like Figure 5 , Figure 6As shown, according to the structures of the first and second embodiments, the shielding time remains the same even if the inductance value of the load changes.

[0106] <Third Embodiment>

[0107] Next, the third embodiment will be described. Figure 7 This is a circuit diagram of the driving circuit in the third embodiment. (As shown...) Figure 7 As shown, the drive circuit 1C includes a driver 10 and a DESAT circuit 20C.

[0108] The DESAT circuit 20C includes a capacitor Cdesat (first capacitor), a resistor R211 (first resistor), a transistor Q23 (first transistor), a resistor R212 (second resistor), a resistor R213 (third resistor), a transistor Q22C (second transistor), a resistor R217 (seventh resistor), a resistor R204 (fourth resistor), a resistor R205 (fifth resistor), a diode D22 (first diode), a diode D23 (third diode), a resistor R206 (sixth resistor), a buffer 31, and a diode Ddesat (second diode).

[0109] like Figure 7 As shown, in the DESAT circuit 20C, one end of capacitor Cdesat is connected to one end of resistor R211, and the other end is grounded. Transistor Q23 is, for example, an NPN type, with its collector connected to the other end of resistor R211, its emitter grounded, and its base connected to one end of resistor R212 and one end of resistor R213. The other end of resistor R212 is connected to one end of resistor R217 and the collector of transistor Q22C. The other end of resistor R213 is grounded. The emitter of transistor Q22C is grounded, and its base is connected to one end of resistor R204 and one end of resistor R205. The other end of resistor R204 is grounded. The other end of resistor R217 is connected to the cathode of diode D23 and the other end of resistor R206. The other end of resistor R205 is connected to the anode of diode D22. The cathode of diode D22 is connected to one end of resistor R206 and the anode of diode Ddesat. The anode of diode D23 is connected to the OUT terminal of driver 10 and the input terminal of buffer 31. The cathode of diode Ddesat is connected to the collector of switching element 41. The output terminal of buffer 31 is connected to the gate of switching element 41.

[0110] like Figure 9 As shown in Table g503, when the switching element 41 is turned on, in the DESAT circuit 20C of the third embodiment, diode D22 is in the off state, transistor Q23 and transistor Q22C are in the off state, and transistor Q11 of driver 10 is in the on state.

[0111] like Figure 9 As shown in Table g503, when the switching element 41 is turned on and Vce is less than the first predetermined voltage value (normal operation), in the DESAT circuit 20C of the third embodiment, diode D22 and transistor Q22C are turned off, transistor Q23 is turned on, and transistor Q11 of the driver 10 is turned off. In the third embodiment, when the switching element 41 is turned on and Vce is less than the first predetermined voltage value (normal operation), diode D22 is turned off and transistor Q23 is turned on, thereby making the DESAT terminal 0 (V). Then, the current output from the DESAT terminal of the driver 10 is charged to the capacitor Cdesat of the DESAT circuit 20C until the third predetermined voltage value of equation (1) is reached.

[0112] like Figure 9 As shown in Table g503, when the switching element 41 is turned on and Vce abnormally rises above the first predetermined voltage value, in the DESAT circuit 20C, diode D22 and transistor Q22C are turned on, transistor Q23 is turned off, and transistor Q11 of the driver 10 is turned off. Then, capacitor Cdesat begins to charge from the current output from the DESAT terminal of the driver 10, and stops charging when it reaches the reference voltage Vdesatth (the second predetermined voltage value). Then, after the shielding time Tw when capacitor Cdesat reaches the third predetermined voltage value, the driver 10 outputs an abnormality detection signal to the control unit 30, and switches the gate level of the switching element 41 to a low level according to the control of the control unit 30. Furthermore, the shielding time Tw is determined by the following formula (3).

[0113] [Formula 3]

[0114]

[0115] In addition, in equation (3), Vdesatth is the reference voltage value, Idesat is the current value of the current source Idesat, and R211 is the resistance value of resistor R211.

[0116] As shown in equation (3), the shielding time Tw of the third embodiment does not include the term of diode D21, so the shielding time Tw of the first embodiment and the second embodiment can be set with better accuracy.

[0117] <Fourth Embodiment>

[0118] Next, the fourth embodiment will be described. Figure 8 This is a circuit diagram of the driving circuit in the fourth embodiment. (As shown...) Figure 8 As shown, the drive circuit 1D includes a driver 10 and a DESAT circuit 20D.

[0119] The DESAT circuit 20D includes capacitor Cdesat (first capacitor), resistor R211 (first resistor), transistor Q23 (first transistor), resistor R212 (second resistor), resistor R213 (third resistor), transistor Q22C (second transistor), resistor R217D (seventh resistor), resistor R204 (fourth resistor), resistor R205 (fifth resistor), diode D22 (first diode), resistor R206D (sixth resistor), buffer 31, and diode Ddesat (second diode).

[0120] like Figure 8 As shown, relative to Figure 7 The DESAT circuit 20D does not include diode D23, but a positive voltage Vcc1 is connected to resistors R217D and R206D.

[0121] In the third embodiment of the DESAT circuit 20C, voltage is applied to resistors R217 and R206 during the period when the pulse signal is high. However, in the fourth embodiment of the DESAT circuit 20D, voltage is supplied to resistors R217D and R206D regardless of the level of the pulse signal.

[0122] like Figure 9 As shown in Table g504, when the switching element 41 is off, in the DESAT circuit 20D of the fourth embodiment, diode D22 is in the on state, transistor Q23 is in the off state, transistor Q22C is in the on state, and transistor Q11 of the driver 10 is in the on state.

[0123] like Figure 9 As shown in Table g504, when the switching element 41 is turned on and Vce is less than the first predetermined voltage value (normal operation), in the DESAT circuit 20D of the fourth embodiment, diode D22 and transistor Q22C are turned off, transistor Q23 is turned on, and transistor Q11 of the driver 10 is turned off. In the fourth embodiment, when the switching element 41 is turned on and Vce is less than the first predetermined voltage value (normal operation), diode D22 is turned off and transistor Q23 is turned on, thereby making the DESAT terminal 0 (V). Then, the current output from the DESAT terminal of the driver 10 is charged to the capacitor Cdesat of the DESAT circuit 20D until the third predetermined voltage value of equation (1) is reached.

[0124] like Figure 9As shown in Table g504, when the switching element 41 is turned on and Vce abnormally rises above the first predetermined voltage value, in the DESAT circuit 20D, diode D22 and transistor Q22C are turned on, transistor Q23 is turned off, and transistor Q11 of the driver 10 is turned off. Then, capacitor Cdesat begins to charge from the current output from the DESAT terminal of the driver 10, and stops charging when it reaches the reference voltage Vdesatth (the second predetermined voltage value). Then, after the capacitor Cdesat reaches the third predetermined voltage value for a shielding time Tw, the driver 10 outputs an abnormality detection signal to the control unit 30 and switches the gate level of the switching element 41 to a low level according to the control of the control unit 30. Furthermore, the shielding time Tw is determined by equation (3). The shielding time Tw of the fourth embodiment does not include the term for diode D21, so it can be set with more precision compared to the shielding time Tw of the first and second embodiments.

[0125] In the third and fourth embodiments, the diode D21 included in the first and second embodiments is not included. The reason for not needing the diode D21 is that, in the third and fourth embodiments, even when the transistor Q23 is in the on state, no external voltage is applied to the DESAT terminal of the driver 10.

[0126] Next, regarding the structures of the third and fourth embodiments, examples of waveform simulation results will be explained.

[0127] Figure 10 This is a diagram showing the simulated waveforms in the third and fourth embodiments when the load inductance is small during a short circuit. Figure 10 In the diagram, the horizontal axis represents time (μs), and the vertical axis represents voltage (V) and current (A). Waveform g301 is the waveform of current Ic. Waveform g302 is the waveform of gate voltage Vge. Waveform g303 is the waveform of VDESAT voltage. Waveform g304 is the waveform of voltage Vce.

[0128] like Figure 10 As shown, the shielding time Tw3 is approximately 4.7 (μs) when the load inductance is small during a short circuit.

[0129] Figure 11 This is a diagram showing the simulated waveforms in the third and fourth embodiments when the load inductance is large during a short circuit. Figure 11 In the diagram, the horizontal axis represents time (μs), and the vertical axis represents voltage (V) and current (A). Waveform g401 is the waveform of current Ic. Waveform g402 is the waveform of gate voltage Vge. Waveform g403 is the waveform of VDESAT voltage. Waveform g404 is the waveform of voltage Vce.

[0130] like Figure 11 As shown, the shielding time Tw4 is approximately 4.7 (μs) when the load inductance is large during a short circuit.

[0131] like Figure 10 , Figure 11 As shown, according to the structures of the third and fourth embodiments, the shielding time remains the same even if the inductance value of the load changes.

[0132] Here, to improve the accuracy of the shielding time, for example, in Figure 1 In the DESAT circuit 20, the circuit block 21 is constructed using, for example, an open-collector comparator, resistors, capacitors, and diodes, and a threshold voltage is generated within the DESAT circuit for comparison. In this circuit structure, the comparator compares the collector-emitter voltage of the switching element with a predetermined threshold voltage. However, in this circuit structure, the number of components increases. For example, the components include one comparator, four resistors, three capacitors, and two diodes. In this circuit structure, the number of components is large, and the circuit cost is higher than in this embodiment. Furthermore, in this embodiment, diode D22 and transistor Q22 function as comparators. In addition, in this embodiment, as described above, the DESAT circuit 20 (20A, 20B, 20C, 20D) is set by the voltage across diode D22.

[0133] That is, according to the structure of this embodiment, compared with the case of using a comparator in the DESAT circuit, the cost can be reduced and the number of parts can be reduced.

[0134] Furthermore, in the described embodiments and examples, a structure in which a positive voltage is connected to the collector of the switching element 41 and the emitter is grounded has been presented, but it is not limited to this. The emitter of another switching element (not shown) may also be connected to the collector of the switching element 41, and the collector of another switching element may also be connected to the emitter.

[0135] The above describes the methods for implementing the present invention using embodiments and examples. However, the present invention is not limited to these embodiments in any way, and various modifications and substitutions can be made without departing from the spirit of the present invention.

Claims

1. A driving circuit, which uses a pulse signal to drive a switching element, comprising: First diode; The first transistor and the second transistor are in a turned-off state when the first diode is in a turned-off state and in a turned-on state when the first diode is in a turned-on state. First capacitor; In this configuration, the base of the first transistor is connected to one end of the second resistor and one end of the third resistor. The other end of the third resistor is connected to the collector of the second transistor. The emitter of the second transistor is grounded, and its base is directly connected to one end of the fourth resistor and one end of the fifth resistor. The other end of the fourth resistor is grounded. The other end of the fifth resistor is directly connected to the anode of the first diode. The cathode of the first diode is connected to one end of the sixth resistor and the anode of the second diode. The other end of the sixth resistor is connected to the cathode of the third diode, the emitter of the first transistor, and the other end of the second resistor. The cathode of the second diode is connected to the collector of the switching element. In the third diode, the pulse signal is input to the anode. One end of the first capacitor is connected to the current source and the anode of the fourth diode, and the other end is grounded. The cathode of the fourth diode is connected to one end of the first resistor and the collector of the first transistor. The other end of the first resistor is grounded; and The control unit controls whether to output the pulse signal to the switching element; When the switching element is in the ON state and the collector-emitter voltage of the switching element is above a first predetermined voltage value, the first diode becomes ON, the first transistor and the second transistor become ON, the second diode becomes OFF, and the first capacitor begins charging. After a shielding time when charging of the first capacitor with current from the current source begins and the voltage values ​​at one end and the other end of the first capacitor reach a second predetermined voltage value greater than the first predetermined voltage value, an abnormality detection signal is output to the control unit. The control unit stops outputting the pulse signal to the switching element based on the abnormality detection signal.

2. The driving circuit according to claim 1, wherein, When the switching element is in the ON state and the collector-emitter voltage of the switching element is less than the first predetermined voltage value, the first diode becomes the OFF state, the first transistor and the second transistor become the OFF state, and after a shielding time when the voltage across the current from the current source reaches a third predetermined voltage value that is different from the first predetermined voltage value and the second predetermined voltage value, the abnormal detection signal is output to the control unit.

3. A driving circuit, which uses a pulse signal to drive a switching element, comprising: First diode; The first transistor and the second transistor are in a turned-off state when the first diode is in a turned-off state and in a turned-on state when the first diode is in a turned-on state. First capacitor; In this configuration, the base of the first transistor is connected to one end of the second resistor and one end of the third resistor, and the emitter is connected to a positive voltage. The other end of the second resistor is connected to the positive voltage. The other end of the third resistor is connected to the collector of the second transistor. The emitter of the second transistor is grounded, and its base is directly connected to one end of the fourth resistor and one end of the fifth resistor. The other end of the fourth resistor is grounded. The other end of the fifth resistor is directly connected to the anode of the first diode. The cathode of the first diode is connected to one end of the sixth resistor and the anode of the second diode. The other end of the sixth resistor is connected to the positive voltage. The cathode of the second diode is connected to the collector of the switching element. One end of the first capacitor is connected to the current source and the anode of the third diode, and the other end is grounded. The cathode of the third diode is connected to one end of the first resistor and the collector of the first transistor. The other end of the first resistor is grounded; and The control unit controls whether to output the pulse signal to the switching element; When the switching element is in the ON state and the collector-emitter voltage of the switching element is above a first predetermined voltage value, the first diode becomes ON, the first transistor and the second transistor become ON, the second diode becomes OFF, and the first capacitor begins charging. After a shielding time when charging of the first capacitor with current from the current source begins and the voltage values ​​at one end and the other end of the first capacitor reach a second predetermined voltage value greater than the first predetermined voltage value, an abnormality detection signal is output to the control unit. The control unit stops outputting the pulse signal to the switching element based on the abnormality detection signal.

4. The driving circuit according to claim 3, wherein, When the switching element is in the ON state and the collector-emitter voltage of the switching element is less than the first predetermined voltage value, the first diode becomes the OFF state, the first transistor and the second transistor become the OFF state, and after a shielding time when the voltage across the current from the current source reaches a third predetermined voltage value that is different from the first predetermined voltage value and the second predetermined voltage value, the abnormal detection signal is output to the control unit.

5. A driving circuit, which uses a pulse signal to drive a switching element, comprising: First diode; First transistor; Second transistor; First capacitor; In this configuration, one end of the first capacitor is connected to the current source and the first resistor, and the other end is grounded. The other end of the first resistor is connected to the collector of the first transistor. The emitter of the first transistor is grounded, and its base is connected to one end of the second resistor and one end of the third resistor. The other end of the third resistor is grounded. The emitter of the second transistor is grounded, and its base is directly connected to one end of the fourth resistor and one end of the fifth resistor. The other end of the fourth resistor is grounded. The other end of the fifth resistor is directly connected to the anode of the first diode. The cathode of the first diode is connected to one end of the sixth resistor and the anode of the second diode. The other end of the sixth resistor is connected to the cathode of the third diode and one end of the seventh resistor. The other end of the seventh resistor is connected to the other end of the second resistor and the collector of the second transistor. The cathode of the second diode is connected to the collector of the switching element. In the third diode, the pulse signal is input to the anode; and The control unit controls whether to output the pulse signal to the switching element; When the switching element is in the ON state and the collector-emitter voltage of the switching element is above a first predetermined voltage value, the first diode becomes ON, the first transistor becomes OFF, the second transistor becomes ON, the second diode becomes OFF, and the first capacitor begins charging. After a shielding time when charging of the first capacitor with current from the current source begins and the voltage values ​​at one end and the other end of the first capacitor reach a second predetermined voltage value greater than the first predetermined voltage value, an abnormality detection signal is output to the control unit. The control unit stops outputting the pulse signal to the switching element based on the abnormality detection signal.

6. The driving circuit according to claim 5, wherein, When the switching element is in the ON state and the collector-emitter voltage of the switching element is less than the first predetermined voltage value, the first diode and the second transistor are in the OFF state, and the first transistor is in the ON state. After a shielding time when the voltage across the current from the current source reaches a third predetermined voltage value that is different from the first predetermined voltage value and the second predetermined voltage value, the abnormal detection signal is output to the control unit.

7. A driving circuit, which uses a pulse signal to drive a switching element, comprising: First diode; First transistor; Second transistor; First capacitor; In this configuration, one end of the first capacitor is connected to the current source and one end of the first resistor, while the other end is grounded. The other end of the first resistor is connected to the collector of the first transistor. The emitter of the first transistor is grounded, and its base is connected to one end of the second resistor and one end of the third resistor. The other end of the third resistor is grounded. The emitter of the second transistor is grounded, and its base is directly connected to one end of the fourth resistor and one end of the fifth resistor. The other end of the fourth resistor is grounded. The other end of the fifth resistor is directly connected to the anode of the first diode. The cathode of the first diode is connected to one end of the sixth resistor and the anode of the second diode. The other end of the sixth resistor is connected to a positive voltage. One end of the seventh resistor is connected to the positive voltage, and the other end is connected to the other end of the second resistor and the collector of the second transistor. The cathode of the second diode is connected to the collector of the switching element; and The control unit controls whether to output the pulse signal to the switching element; When the switching element is in the ON state and the collector-emitter voltage of the switching element is above a first predetermined voltage value, the first diode becomes ON, the first transistor becomes OFF, the second transistor becomes ON, the second diode becomes OFF, and the first capacitor begins charging. After a shielding time when charging of the first capacitor with current from the current source begins and the voltage values ​​at one end and the other end of the first capacitor reach a second predetermined voltage value greater than the first predetermined voltage value, an abnormality detection signal is output to the control unit. The control unit stops outputting the pulse signal to the switching element based on the abnormality detection signal.

8. The driving circuit according to claim 7, wherein, When the switching element is in the ON state and the collector-emitter voltage of the switching element is less than the first predetermined voltage value, the first diode and the second transistor are in the OFF state, and the first transistor is in the ON state. After a shielding time when the voltage across the current from the current source reaches a third predetermined voltage value that is different from the first predetermined voltage value and the second predetermined voltage value, the abnormal detection signal is output to the control unit.

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