Control and switching devices

Abstract

To solve the following problem: conventionally, when a switching element for on-control is simply turned off to an off state until an element current is under a short-circuit threshold value, turning-on of a main switching element is delayed.SOLUTION: A controller includes: a detection section which outputs a short-circuit detection signal according to the fact that a short-circuit of the main switching element is detected during the turning-on period of the main switching element by a switching element for on-control; a protection operation control section which outputs an instruction signal of a short-circuit protection operation at the timing delayed more than the short-circuit detection signal; and a protection section which turns off the switching element for on-control according to an instruction signal. The protection operation control section outputs an instruction signal according to that the short-circuit detection signal is continued beyond a first reference time.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a control device and a switching device. [Background technology]

[0002] Conventionally, when the element current flowing through the main switching element turned on by the on-control switching element becomes transiently large during the turn-on period and exceeds the short-circuit threshold, the on-control switching element is kept in the off state until the element current falls below the short-circuit threshold (see, for example, Patent Document 1). Patent Document 1: Japanese Patent Application Laid-Open No. 2011-259223 Patent Document 2 Japanese Patent Application Laid-Open No. 11-4150 Summary of the Invention [Problem to be solved by the invention]

[0003] However, if the switching element for on-control is simply kept in the off state until the element current falls below the short-circuit threshold, the turn-on of the main switching element will be delayed. [Means for solving the problem]

[0004] To solve the above problems, a first aspect of the present invention provides a control device. The control device may include a detection unit that outputs a short-circuit detection signal in response to detection of a short circuit in the main switching element during a turn-on period of the main switching element by the on-control switching element. The control device may include a protection operation control unit that outputs an instruction signal for short-circuit protection operation with a timing delayed from the short-circuit detection signal. The control device may include a protection unit that turns off the on-control switching element in response to the instruction signal.

[0005] The protection operation control unit may output the instruction signal in response to the short circuit detection signal continuing for more than a first reference time.

[0006] The protection operation control unit may include a delay unit that delays the short circuit detection signal by a first reference time, and a logical product operation unit that takes a logical product of the short circuit detection signal and the short circuit detection signal delayed by the delay unit.

[0007] The detection unit may output a short circuit detection signal when a parameter corresponding to a current flowing through the main switching element exceeds a first threshold, and the protection operation control unit may output an instruction signal when the parameter exceeds a second threshold higher than the first threshold.

[0008] The protective operation control unit may delay the short circuit detection signal until after the turn-on of the main switching element is completed, and output the signal as the instruction signal.

[0009] The protection unit may include a clamp unit that clamps the gate voltage of the main switching element to a reference voltage that is lower than the gate voltage when the main switching element is in a steady on-state, in response to the short-circuit detection signal.

[0010] The protection unit may include a cutoff unit that turns off the main switching element in response to the short circuit detection signal continuing for more than a second reference time.

[0011] The control device may further include a drive control section that controls the drive of the main switching element in response to the drive signal.

[0012] In a second aspect of the present invention, there is provided a switching device. The switching device may include the control device of the first aspect. The switching device may include a main switching element that is drive-controlled by a drive control unit.

[0013] The above summary of the invention does not list all of the necessary features of the present invention, and subcombinations of these features may also constitute inventions. [Brief explanation of the drawings]

[0014] [Figure 1]1 shows a switching device 1 according to a first embodiment. [Figure 2] 2 shows the operating waveforms of the switching device 1. [Figure 3] 1 shows a switching device 1A according to a second embodiment. [Figure 4] 10 shows a switching device 1B according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] The present invention will be described below through embodiments of the invention, but the following embodiments do not limit the scope of the invention according to the claims. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0016] [1. First embodiment] [1.1. Switching device 1] FIG. 1 shows a switching device 1 according to this embodiment. The switching device 1 may be a device used for driving a motor or supplying power, and may be, for example, a power conversion device such as an inverter that converts DC power supplied from a positive terminal 101 and a negative terminal 102 into AC power and outputs the AC power from a power supply output terminal 105. The switching device 1 may also be an IPM (intelligent power module) that automatically performs protection operations in the event of an abnormality. The switching device 1 may include positive and negative main switching elements 2 and 3, and positive and negative control devices 4 and 5. The negative terminal 102 may be connected to ground, for example. In addition to the positive terminal 101, the negative terminal 102, and the power supply output terminal 105, the switching device 1 may also be provided with an input terminal 103 to which a drive signal Vin is input.

[0017] [1.1.1. Main switching elements 2 and 3] The main switching elements 2 and 3 are connected in series between the positive terminal 101 and the negative terminal 102. For example, the collector terminals of the main switching elements 2 and 3 are connected to the positive terminal 101 side, and the emitter terminals are connected to the negative terminal 102 side. The main switching elements 2 and 3 may form upper and lower arms of a switching device, and a power supply output terminal 105 may be connected to the midpoint of the main switching elements 2 and 3.

[0018] The main switching elements 2, 3 may be provided with sense emitter terminals connected to the corresponding control devices 4, 5. For example, current detection switching elements 20, 30 may be provided in parallel to the main switching elements 2, 3. The emitter terminals of the switching elements 20, 30 may be sense emitter terminals for the main switching elements 2, 3, and a current corresponding to the current flowing through the main switching elements 2, 3 (also referred to as a sense emitter current) may be passed to the control devices 4, 5. In this embodiment, as an example, the main switching elements 2, 3 may be IGBTs, and the current detection switching elements 20, 30 may be IGBTs smaller than the main switching elements 2, 3. The switching elements 20, 30 may be provided on the same chip as the main switching elements 2, 3.

[0019] The main switching elements 2 and 3 may have a parasitic diode (not shown) whose cathode is on the side of the positive terminal 101. In addition to this, or instead of this, a freewheeling diode (not shown) may be connected in antiparallel to each of the main switching elements 2 and 3 so that its cathode is on the side of the positive terminal 101. The main switching elements 2 and 3 may also be semiconductor elements of other structures, such as MOSFETs or bipolar transistors.

[0020] [1.1.2. Control devices 4, 5] The control devices 4 and 5 control the main switching elements 2 and 3. The positive-side control device 4 may control the main switching element 2, and the negative-side control device 5 may control the main switching element 3. Since the control devices 4 and 5 have the same configuration, in this embodiment, only the negative-side control device 5 will be described, and a description of the positive-side control device 4 will be omitted.

[0021] The control device 5 controls the main switching element 3. The control device 5 has a drive control unit 50, a detection unit 51, a protection operation control unit 6, and a protection unit .

[0022] [1.1.2(1). Drive control unit 50] The drive control unit 50 controls the drive of the main switching element 3 in response to the drive signal Vin. The drive signal Vin may be input to the control device 5 from the outside via the input terminal 103. The drive signal Vin may include an ON command signal that turns the main switching element 3 ON and an OFF command signal that turns the main switching element 3 OFF. For example, the drive signal Vin may cause the main switching elements 2 and 3 to perform switching using a synchronous rectification method. For example, the drive signal Vin may be set to selectively (for example, alternately) turn on the main switching elements 2 and 3 with a dead time in between, where both the main switching elements 2 and 3 are OFF. The drive signal Vin may control the main switching elements 2 and 3 using PWM control. Note that in this embodiment, as an example, the drive signal Vin instructs the main switching element 3 to be turned on when it is at a low level and instructs the main switching element 3 to be turned off when it is at a high level. The drive control unit 50 includes a switching element 504 and a switching element 505 .

[0023] The switching element 504 is connected between the power supply of the control voltage Vcc and the gate of the main switching element 3. The switching element 504 is an ON control switching element, and by establishing conduction between the power supply of the control voltage Vcc and the gate of the main switching element 3, it sets the output signal Vout to the gate terminal of the main switching element 3 to high level, thereby turning on the main switching element 3. The switching element 504 may be turned on when the drive signal Vin supplied via a later-described OR gate 70 in the protection unit 7 is at low level. Note that, as an example, in this embodiment, the switching element 504 is a P-type MOSFET, but it may also be a semiconductor element of another structure.

[0024] The switching element 505 is connected between the gate of the main switching element 3 and the negative terminal 102. The switching element 505 is an OFF control switching element, and by bringing the gate of the main switching element 3 and the negative terminal 102 into conduction, the output signal Vout to the gate terminal of the main switching element 3 becomes low level, thereby turning off the main switching element 3. The switching element 505 may be turned on when the drive signal Vin is at high level. Note that, as an example, in this embodiment, the switching element 505 is an N-type MOSFET, but it may also be a semiconductor element with another structure.

[0025] [1.1.2(2).Detection unit 51] The detection unit 51 outputs a short circuit detection signal in response to detecting a short circuit in the main switching element 3. The detection unit 51 may detect a short circuit in the main switching element 3 while the main switching element 3 is being turned on by the on-control switching element 504, but may also detect a short circuit during other periods in addition to this. The detection unit 51 may detect that a short circuit has occurred in response to a parameter corresponding to the current flowing through the main switching element 3 exceeding a first threshold value. The detection unit 51 has a measurement unit 510 and a determination unit 515.

[0026] [1.1.2(2-1).Measurement section 510] The measuring section 510 measures a parameter according to the current flowing through the main switching element 3. The current flowing through the main switching element 3 may be an instantaneous value of the current flowing through the main switching element 3.

[0027] In this embodiment, as an example, the measurement unit 510 may have two resistors 511, 512 connected in series between the sense emitter terminal of the main switching element 3 (the emitter terminal of the switching element 30, as an example in this embodiment) and ground. The measurement unit 510 may supply a voltage (also referred to as a sense voltage) Vc1 detected in response to the sense emitter current flowing through the resistor 512 on the ground side to the determination unit 515 as a parameter corresponding to the current flowing through the main switching element 3.

[0028] [1.1.2(2-2).Determination unit 515] The determination unit 515 compares the parameter measured by the measurement unit 510 (in this embodiment, the sense voltage Vc1 as an example) with a first threshold. The determination unit 515 may detect that a short circuit has occurred in the main switching element 3 in response to the sense voltage Vc1 exceeding the first threshold. In this embodiment, as an example, the determination unit 515 is a comparator, and a non-inverting input terminal of the determination unit 515 is connected to the connection point between the resistors 511 and 512 of the measurement unit 510, and a first reference potential Vref1 is connected to an inverting input terminal of the determination unit 515.

[0029] The first reference potential Vref1 is an example of a first threshold and is used as a threshold for determining whether a short circuit has occurred. The first reference potential Vref1 may be higher than the sense voltage Vc1 when the main switching element 3 is not in a short-circuit state, or may be lower than the sense voltage Vc1 when the main switching element 3 is in a short-circuit state. As a result, when the main switching element 3 is in a short-circuit state, the output signal V1 of the determination unit 515 becomes high level, serving as a short-circuit detection signal indicating that a short circuit has been detected. The determination unit 515 may supply the output signal V1 to the protection operation control unit 6.

[0030] Note that the sense voltage Vc1 transiently increases during the turn-on period of the main switching element 3. The first reference potential Vref1 may be lower than the peak potential of the sense voltage Vc1 during the turn-on period of the main switching element 3. As a result, if the current flowing through the main switching element 3 transiently increases during the turn-on period of the main switching element 3, a short circuit may be erroneously detected.

[0031] [1.1.2(3). Protective operation control unit 6] The protection operation control unit 6 is connected to the output terminal of the detection unit 51. When a short circuit is detected by the detection unit 51, the protection operation control unit 6 may cause the protector 7 to perform a short circuit protection operation. The protection operation control unit 6 has a voltage control unit 60, an ON-side switch control unit 61, and a cutoff control unit 62, each connected to the output terminal of the detection unit 51.

[0032] [1.1.2(3-1). Voltage control unit 60] The voltage control unit 60 outputs to the protection unit 7 an instruction signal for short-circuit protection operation that limits the level of the signal Vout supplied to the gate terminal of the main switching element 3. As an example in the present embodiment, the voltage control unit 60 may supply the output signal V1 output from the detection unit 51 to the protection unit 7 as an on / off signal for an operational amplifier 725, which will be described later.

[0033] [1.1.2(3-2). On-side switch control unit 61] The ON-side switch control unit 61 outputs to the protection unit 7 an instruction signal (also referred to as a first instruction signal) for short-circuit protection operation that turns off the switching element 504 for controlling the main switching element 3 to be ON.

[0034] The ON-side switch control unit 61 outputs the first indication signal at a timing delayed from the short-circuit detection signal (high-level output signal V1 in this embodiment as an example). For example, the ON-side switch control unit 61 may output the first indication signal at a timing delayed from the rising edge of the short-circuit detection signal. The ON-side switch control unit 61 according to this embodiment may output the first indication signal in response to the short-circuit detection signal continuing beyond a first reference time.

[0035] Here, outputting an indication signal in response to the short circuit detection signal continuing beyond a reference time (for example, a first reference time) may mean outputting an indication signal for the period during which the short circuit detection signal continues beyond the reference time, or in other words, when the short circuit detection signal continues beyond the reference time, continuing to output the indication signal as long as the output of the short circuit detection signal does not end.

[0036] The first reference time may be set to any length of time in advance. For example, the first reference time may be the time from the rising edge of the short circuit detection signal to the occurrence of an event that occurs after the rising edge of the short circuit detection signal.

[0037] For example, the first reference time may be the time from the rising edge to the falling edge of the short-circuit detection signal when the main switching element 3 is turned on without being short-circuited. The falling edge of the short-circuit detection signal may be the timing at which the sense voltage Vc1 falls below the first reference potential Vref1.

[0038] The first reference time may be the time from the rising edge of the short-circuit detection signal to the end of the mirror period when the main switching element 3 is turned on without being short-circuited. The mirror period may be a period during which the change in the gate-source voltage becomes flat as a result of the charge flowing into the gate of the main switching element 3 during the turn-on period being used mainly to charge the gate-drain capacitance of the main switching element 3. The end of the mirror period may be the timing at which the gate-source voltage starts to rise after becoming flat.

[0039] The on-side switch control unit 61 includes a delay unit 610 , a logical product operation unit 611 , and a buffer circuit unit 612 .

[0040] The delay unit 610 is connected to the output terminal of the detection unit 51 and delays the short-circuit detection signal included in the output signal V1 of the detection unit 51 by a first reference time. In the present embodiment, as an example, the delay unit 610 may be an RC integration circuit. The delay unit 610 may supply the delayed short-circuit detection signal to the AND operation unit 611.

[0041] The AND operation unit 611 is connected to the output terminal of the detection unit 51 and the output terminal of the delay unit 610, and performs a logical AND operation on the short-circuit detection signal and the short-circuit detection signal delayed by the delay unit 610. In the present embodiment, as an example, the AND operation unit 611 is a NAND gate, and may invert and output the result of the logical AND operation. As a result, the output signal of the AND operation unit 611 becomes low level when the short-circuit detection signal continues beyond the first reference time. The AND operation unit 611 may supply the output signal to the buffer circuit unit 612.

[0042] The buffer circuit unit 612 is connected to the output terminal of the AND operation unit 611 and corrects the signal strength of the output signal of the AND operation unit 611. In the present embodiment, as an example, the buffer circuit unit 612 is a NOT gate and cooperates with the NOT gate portion of the NAND gate serving as the AND operation unit 611 to output an output signal V2 indicating double negation of the operation result of the AND operation in the AND operation unit 611. A high-level signal included in the output signal V2 may be an example of a first instruction signal that instructs the ON-control switching element 504 to turn off, and the buffer circuit unit 612 may output the first instruction signal by outputting the high-level output signal V2. The buffer circuit unit 612 may supply the output signal V2 to the protection unit 7.

[0043] [1.1.2(3-3).Shutoff control unit 62] The shutdown control unit 62 outputs an instruction signal (also referred to as a second instruction signal) for short-circuit protection operation to turn off the main switching element 3 and the off-control switching element 505 to the protection unit 7, regardless of the drive signal Vin. The shutdown control unit 62 may output the second instruction signal in response to the short-circuit detection signal continuing beyond a second reference time. In this embodiment, as an example, the second instruction signal may be a low-level signal. Note that the shutdown control unit 62 may have a configuration similar to that of the on-side switch control unit 61. For simplification, the second instruction signal for the off-control switching element 505 is not shown in FIG. 1.

[0044] The second reference time may be preset to a time length longer than the first reference time. The second reference time may be the time from the rising edge of the short circuit detection signal to any time before the main switching device 3 is destroyed when the device is short-circuited. As an example, the second reference time may be 1 μs.

[0045] [1.1.3.Protection part 7] The protection unit 7 performs various short-circuit protection operations in response to signals from the protection operation control unit 6. The protection unit 7 includes an OR gate 70, a switching element 71, and a clamp unit 72.

[0046] [1.1.3(1).OR gate 70] The OR gate 70 is connected to the input terminal 103 and the on-side switch control unit 61 of the protection operation control unit 6. The OR gate 70 may take a logical sum of the drive signal Vin and a first instruction signal included in the output signal V2 from the protection operation control unit 6. The OR gate 70 may supply the calculation result to the switching element 504 for controlling the on-state of the main switching element 3. As a result, the switching element 504 is turned off in response to the drive signal Vin going high, and is also turned off in response to the output signal V2 going high, i.e., in response to the output of the first instruction signal.

[0047] [1.1.3(2).Switching element 71] The switching element 71 is connected in parallel with the switching element 505 for OFF control, between the gate of the main switching element 3 and the negative terminal 102. The switching element 71 may turn off the main switching element 3 by bringing the gate of the main switching element 3 and the negative terminal 102 into conduction. The switching speed of the switching element 71 may be lower than the switching speed of the switching element 505.

[0048] The switching element 71 is an example of a cutoff unit, and may turn off the main switching element 3 in response to the short-circuit detection signal continuing for more than a second reference time. As an example in this embodiment, the switching element 71 may turn off the main switching element 3 in response to a low-level second instruction signal being supplied from the cutoff control unit 62. Note that, as an example in this embodiment, the switching element 71 is a P-type MOSFET, but may be a semiconductor element of another structure.

[0049] [1.1.3(3). Clamp part 72] The clamp unit 72 clamps the gate voltage of the main switching device 3 to a reference voltage in response to the short-circuit detection signal. The reference voltage may be a voltage lower than the gate voltage when the main switching device 3 is in a steady on-state. The clamp unit 72 has resistors 721 and 722 and an operational amplifier 725.

[0050] Resistors 721 and 722 are connected in series between the gate and negative terminal of the main switching element 3. The midpoint of the resistors 721 and 722 may be connected to the inverting input terminal of an operational amplifier 725. As a result, a voltage corresponding to the gate voltage of the main switching element 3 is supplied to the inverting input terminal.

[0051] The operational amplifier 725 has a non-inverting input terminal connected to a reference voltage and an output terminal connected to the gate of the main switching element 3. This allows the operational amplifier 725 and resistors 721 and 722 to cooperate to clamp the gate voltage to the reference voltage. The operational amplifier 725 may be turned on by an on signal output from the voltage control unit 60, and turned off by an off signal.

[0052] According to the above-described switching device 1, the on-control switching element 504 is turned off after a short circuit is detected, so the timing of turning off the switching element 504 is delayed compared to when the switching element 504 is turned off simultaneously with the detection of a short circuit. Therefore, if the current flowing through the main switching element 3 becomes transiently large during the turn-on period of the main switching element 3 and is erroneously detected as a short circuit, the timing of interrupting charging of the gate of the main switching element 3 can be delayed. This makes it possible to prevent the turn-on of the main switching element 3 from being delayed due to the interruption of gate charging.

[0053] Furthermore, since the first indication signal for turning off the switching element 504 is output in response to the short-circuit detection signal continuing beyond the first reference time, if the current flowing through the main switching element 3 during the turn-on period transiently increases and a short circuit is erroneously detected, the output of the first indication signal starts with a delay from the start of the erroneous detection and ends at the end of the erroneous detection. Therefore, the output period of the first indication signal is shorter than when the first indication signal is output over the period during which a short circuit is erroneously detected. This shortens the period during which gate charging of the main switching element 3 is interrupted by the turn-off of the on-control switching element 504, and enables the main switching element 3 to be turned on earlier.

[0054] Furthermore, the protection operation control unit 6 performs a logical AND operation between the short circuit detection signal and a signal obtained by delaying the short circuit detection signal by a first reference time, and therefore can output a first instruction signal in response to the short circuit detection signal continuing beyond the first reference time.

[0055] Furthermore, in response to the short circuit detection signal, the gate voltage of the main switching element 3 is maintained at a reference voltage lower than the voltage in the steady on state, thereby reducing the current flowing through the main switching element 3 and preventing element breakdown.

[0056] Furthermore, since the main switching element 3 is turned off in response to the short circuit detection signal continuing for more than the second reference time, it is possible to more reliably prevent element destruction due to a short circuit.

[0057] [1.2.Operating waveform] FIG. 2 shows the operating waveforms of the switching device 1. As an example, this figure shows the sense voltage Vc1, gate voltage Vout, and collector current Ic when a short circuit occurs after the main switching element 3 is turned on without a short circuit. The vertical axis in the figure represents voltage or current, and the horizontal axis represents time. Note that the collector current Ic may be the current flowing through the main switching element 3.

[0058] First, during period t0, when the main switching element 3 is turned on without a short circuit, the sense voltage Vc1 exhibits a voltage waveform that transiently rises and falls (also called a transient sense voltage), and then is maintained at the voltage in the steady-state on state (also called a steady-state sense voltage).

[0059] Because the transient sense voltage temporarily exceeds the first reference voltage Vref1, the detector 51 erroneously detects a short circuit in the main switching element 3 and outputs a short-circuit detection signal. This causes the clamper 72 to clamp the gate voltage Vout to the reference voltage. However, at the start of this operation, the first instruction signal is not output from the ON-side switch controller 61, the ON-control switching element 504 is maintained in the ON state, and charging of the gate of the main switching element 3 continues. This causes the gate voltage to gradually decrease. Next, when the short-circuit detection signal continues beyond the first reference time, the ON-side switch controller 61 outputs the first instruction signal, which turns off the ON-control switching element 504 and interrupts charging of the gate of the main switching element 3. This causes the clamper 72 to maintain the gate voltage Vout at the reference voltage. Furthermore, if the mirror period has already started, the mirror period is extended (not shown). Next, when the transient sense voltage of sense voltage Vc1 falls below reference voltage Vref1 and the output of the short circuit detection signal ends, the output of the first indication signal ends, turning on switching element 504 for on-control, restarting charging of the gate of main switching element 3, and completing the turn-on of main switching element 3.

[0060] Subsequently, when a short circuit occurs in the main switching element 3 during period t1, the collector current Ic and the sense voltage Vc1 increase rapidly. Next, when the sense voltage Vc1 exceeds the first reference voltage Vref1, the detector 51 detects the short circuit in the main switching element 3 and outputs a short circuit detection signal. As a result, the clamper 72 clamps the gate voltage Vout to the reference voltage and turns off the ON-control switching element 504, just as in period t0. As a result, the gate voltage Vout is maintained at the reference voltage during period t2. When the short circuit detection signal continues beyond the second reference time, the cutoff controller 62 outputs a second instruction signal during period t3. As a result, the OFF-control switching element 505 is turned off and the main switching element 3 is turned off by the switching element 71.

[0061] [2. Second Embodiment] 3 shows a switching device 1A according to a second embodiment. A control device 5A of the switching device 1A includes a protection operation control unit 6A, which in turn includes an on-side switch control unit 61A. In this embodiment and other embodiments described later, components that are substantially the same as those in the switching device 1 shown in FIG. 1 are designated by the same reference numerals, and descriptions thereof will be omitted.

[0062] The ON-side switch control unit 61A outputs a first instruction signal for short-circuit protection operation, which turns off the ON-control switching element 504, to the protection unit 7 at a timing delayed from the short-circuit detection signal (high-level output signal V1 in this embodiment, as an example). The ON-side switch control unit 61A may output the first instruction signal at a timing delayed from the rising edge of the short-circuit detection signal. The ON-side switch control unit 61A according to this embodiment may output the first instruction signal in response to a parameter according to the current flowing through the main switching element 3 exceeding a second threshold value higher than the first threshold value used for short-circuit detection in the detection unit 51. The ON-side switch control unit 61A has a determination unit 615A.

[0063] The determination unit 615A compares a parameter (sense voltage Vc1 in this embodiment, as an example) measured by the measurement unit 510 of the detection unit 51 with a second threshold. The determination unit 615A may detect a timing delayed from the short-circuit detection signal in response to the sense voltage Vc1 exceeding the second threshold. In this embodiment, as an example, the determination unit 615A is a comparator, and a non-inverting input terminal of the determination unit 615A is connected to the connection point between the resistors 511 and 512 of the measurement unit 510, and a second reference potential Vref2 is connected to an inverting input terminal of the determination unit 615A.

[0064] The second reference potential Vref2 is an example of a second threshold and is set higher than the first reference potential Vref1. The second reference potential Vref2 may be lower than the sense voltage Vc1 when the main switching element 3 is short-circuited. As a result, when the main switching element 3 is short-circuited, the output signal V1 of the determination unit 515 in the detection unit 51 goes high, and then the output signal V3 of the determination unit 615A goes high, indicating that a timing delayed from the short-circuit detection signal has been detected.

[0065] The determination unit 615A may supply the output signal V3 to the protection unit 7. The high-level signal included in the output signal V3 is an example of a first instruction signal, and may instruct the switching element 504 for ON control to be turned off.

[0066] According to the above-described switching device 1A, a first indication signal for turning off switching element 504 is output in response to a parameter corresponding to the current flowing through main switching element 3 exceeding a second threshold higher than the first threshold for short-circuit detection. Therefore, if the current flowing through main switching element 3 transiently increases during the turn-on period, causing a false short circuit to be detected, output of the indication signal starts later than the start of the false short circuit detection and ends earlier than the end of the false detection. Therefore, the output period of the first indication signal is shorter than when the first indication signal is output over the entire period during which a short circuit is falsely detected. This shortens the period during which gate charging of main switching element 3 is interrupted by turning off on-control switching element 504, thereby enabling the main switching element 3 to be turned on earlier.

[0067] 3. Third Embodiment 4 shows a switching device 1B according to a third embodiment. A control device 5B of the switching device 1B includes a protection operation control unit 6B, and the protection operation control unit 6B has an ON-side switch control unit 61B.

[0068] The ON-side switch control unit 61B outputs a first instruction signal for short-circuit protection operation, which turns off the ON-control switching element 504, to the protection unit 7 at a timing delayed from the short-circuit detection signal (high-level output signal V1 in this embodiment, as an example). The ON-side switch control unit 61B may delay the short-circuit detection signal to output it as the first instruction signal after the timing at which the main switching element 3 is completely turned on. The ON-side switch control unit 61B according to this embodiment has a delay unit 610B.

[0069] The delay unit 610B is connected to the output terminal of the detection unit 51, and delays the short-circuit detection signal included in the output signal V1 of the detection unit 51 until after the timing at which the main switching element 3 is turned on. As an example, in this embodiment, the delay unit 610 may be an RC integration circuit.

[0070] The delay unit 610B may delay the short-circuit detection signal by a third reference time. The third reference time may be preset to any length of time. For example, the third reference time may be the time from the rising edge of the short-circuit detection signal to the completion of turn-on of the main switching element 3. Completion of turn-on of the main switching element 3 may mean that the main switching element 3 is in a steady on-state, for example, that the sense voltage Vc1 becomes a steady on-voltage during the turn-on period. As an example, the third reference time may be 50 to 100 ns.

[0071] The delay unit 610B may supply the output signal V3 to the protection unit 7. The high-level signal included in the output signal V3 may be an example of a first instruction signal that instructs the on-control switching element 504 to turn off, and the delay unit 610B may output the first instruction signal by outputting the high-level output signal V3.

[0072] According to the above switching device 1B, the short-circuit detection signal is delayed until after the timing at which turn-on of main switching element 3 is completed, and is output as the first instruction signal for turning off switching element 504, so that turn-on of main switching element 3 has already been completed by the timing at which the first instruction signal is output. Therefore, even if the current flowing through main switching element 3 becomes transiently large during the turn-on period and a short circuit is erroneously detected, it is possible to prevent the gate charging of main switching element 3 from being interrupted by the turn-off of on-control switching element 504, and to hasten the turn-on of main switching element 3.

[0073] [4. Modifications] In the above embodiment, the protection operation control units 6, 6A, 6B have been described as including the voltage control unit 60 and the cutoff control unit 62, but they may not include at least one of these.

[0074] In addition, although the voltage detected as the sense emitter current of the main switching element 3 flows through resistors 511 and 512 has been described as being used as the parameter corresponding to the current flowing through the main switching element 3, other parameters may also be used, such as the voltage detected as the emitter current of the main switching element 3 flows through a resistor.

[0075] Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It will be apparent to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included within the technical scope of the present invention.

[0076] It should be noted that the execution order of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically stated as "before," "prior to," etc., and that the processes can be performed in any order unless the output of a previous process is used in a subsequent process. Even if the operational flow in the claims, specifications, and drawings is described using "first," "next," etc. for convenience, this does not mean that the processes must be performed in this order. [Explanation of symbols]

[0077] 1 Switching device 2 Main switching element 3 Main switching element 4. Control device 5. Control device 6 Protection operation control section 7 Protective part 20 Switching element 30 Switching element 50 Drive control unit 51 Detection unit 60 Voltage control section 61 On-side switch control section 62 Shutdown control section 70 OR gate 71 Switching element 72 Clamp section 101 Positive terminal 102 Negative terminal 103 Input terminal 105 Power output terminal 504 Switching element 505 Switching element 510 Measuring section 511 Resistance 512 Resistance 515 Judgment section 610 Delay Section 611 Logical product operation unit 612 Buffer circuit section 721 Resistance 722 Resistance 725 Operational Amplifier

Claims

1. a detection unit that outputs a short circuit detection signal indicating that a short circuit has been detected when a parameter corresponding to a current flowing through a main switching element exceeds a threshold value during a turn-on period of the main switching element by an on-control switching element; a protection operation control unit that outputs a signal instructing a short circuit protection operation at a timing delayed from the short circuit detection signal; a protection unit that turns off the switching element for ON control in response to the instruction signal; Equipped with the protection operation control unit outputs the instruction signal in response to the short circuit detection signal continuing for more than a first reference time; the threshold value is lower than the peak value of the parameter during a turn-on period when the main switching element is not short-circuited, The control device, wherein the first reference time is preset to the time from the rising edge of the short circuit detection signal to the end of a mirror period when the main switching element is turned on in a non-short circuit state.

2. a detection unit that outputs a short circuit detection signal in response to detecting a short circuit in the main switching element during a turn-on period of the main switching element by the on-control switching element; a protection operation control unit that outputs a signal instructing a short circuit protection operation at a timing delayed from the short circuit detection signal; a protection unit that turns off the switching element for ON control in response to the instruction signal; Equipped with the protection operation control unit outputs the instruction signal in response to the short circuit detection signal continuing beyond a first reference time, and outputs another signal in response to the short circuit detection signal continuing beyond a second reference time that is longer than the first reference time; The protection unit is a control device having a cutoff unit that turns off the main switching element in response to the other signal.

3. The protection operation control unit a delay unit that delays the short circuit detection signal by the first reference time; 3. The control device according to claim 2, further comprising a logical product calculation unit that calculates a logical product of the short circuit detection signal and the short circuit detection signal delayed by the delay unit.

4. 4. The control device according to claim 1, wherein the protection unit includes a clamp unit that clamps the gate voltage of the main switching element to a reference voltage that is lower than the gate voltage when the main switching element is in a steady on state, in response to the short-circuit detection signal.

5. The control device according to claim 1 , further comprising a drive control section that controls the driving of the main switching element in response to a drive signal.

6. The control device according to claim 5 ; a main switching element that is drive-controlled by the drive control unit; A switching device comprising:

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