Control and switching devices

Abstract

[Problem] When a protection operation is simply cancelled in accordance with the resolution of a short-circuit, there is a risk that the short-circuit could occur again and cause device breakdown. [Solution] Provided is a control device comprising: a protection unit that, in accordance with a short-circuit occurring in a main switching element, limits current flowing to the main switching element; and a protection operation control unit that causes the protection unit to continue the protection operation until the supply of power to a drive control unit controlling driving of the main switching element in accordance with a drive signal is stopped. The protection operation control unit has a first holding unit that holds information indicating that the protection operation should be executed until a first cancellation condition is satisfied, which includes resolution of a short-circuit when a short-circuit has occurred, and stopping of the supply of power.

Description

[Technical field]

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

[0002] Conventionally, when a short circuit occurs in a main switching element, a protective operation such as limiting the gate voltage of the main switching element is performed, and the protective operation is released when the short circuit is eliminated (see, for example, Patent Documents 1 and 2). Patent Document 1: JP 2011-259233 A Patent Document 2: Japanese Patent Application Laid-Open No. 11-4150 Problems to be Solved

[0003] However, simply canceling the protection operation when the short circuit is eliminated may cause a new short circuit, resulting in destruction of the element.

[0004] In order to solve the above problems, a first aspect of the present invention provides a control device. The control device may include a protection unit that performs a protection operation to limit a current flowing through a main switching element in response to a short circuit occurring in the main switching element. The control device may include a protection operation control unit that causes the protection unit to continue the protection operation until power supply to a drive control unit that drives and controls the main switching element in response to a drive signal is stopped.

[0005] The protection operation control unit may have a first holding unit that holds information indicating that protection operation should be performed when a short circuit occurs until a first release condition is satisfied, including that the short circuit has been eliminated and that the power supply has been stopped.

[0006] The protection operation control unit may have a first holding unit that holds information indicating that protection operation should be executed when a short circuit occurs until a first release condition is satisfied, including that the short circuit has been eliminated and that a standard operation for resuming power supply has been performed.

[0007] The protective operation control unit may include a reset unit that resets the first holding unit in response to the first release condition being satisfied.

[0008] The first release condition may further include that a drive signal for turning on the main switching element is not being supplied, and that a reference time or more has elapsed since the start of the protection operation.

[0009] The protection unit may also perform a protective operation in response to at least one of the following abnormalities: the main switching element has reached a temperature higher than a reference temperature, a current larger than a reference current flows through the main switching element, and a voltage supplied by the power supply has dropped below a reference voltage. The protective operation control unit may have a second holding unit that holds information indicating that the protective operation should be performed when at least one abnormality occurs, until a second release condition is satisfied, the second release condition including that the abnormality is eliminated, that a drive signal for turning on the main switching element is not being supplied, and that a reference time or more has elapsed since the start of the protective operation, but that does not include that the power supply is stopped.

[0010] The protective operation control unit may be supplied with power from a power source separate from that of the drive control unit.

[0011] The protective operation control unit may include a third holding unit that holds information on whether or not to continue the protective operation in response to receiving power from a power source common to the drive control unit.

[0012] The control device may include a measurement unit that measures a parameter corresponding to a current flowing through the main switching element, and a detection unit that detects the occurrence of a short circuit in the main switching element according to the measured parameter.

[0013] The control device may further include an output section that outputs an alarm signal when a protective action is performed.

[0014] The control device may further include a drive control unit.

[0015] 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.

[0016] The above summary of the invention does not list all of the necessary features of the present invention. Also, subcombinations of these features may also be inventions. [Brief description of the drawings]

[0017] [Figure 1] 1 shows a switching device 1 according to a first embodiment. [Diagram 2] 1 shows a switching device 1A according to a second embodiment. [Diagram 3] 1 shows a switching device 1B according to a third embodiment. [Figure 4] 1 shows a switching device 1C according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] 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.

[0019] [1. First embodiment] [1.1. Switching device] FIG. 1 shows a switching device 1 according to the present 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 device that converts DC power supplied from a positive terminal 101 and a negative terminal 102 into AC power and outputs it from a power supply output terminal 105. The switching device 1 may also be an IPM (intelligent power module) that automatically performs a protective operation 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 be provided with an input terminal 103 to which a drive signal Vin is input, an alarm terminal 104 to which an alarm signal ALM is output, and the like.

[0020] [1.1.1. Main switching elements 2 and 3] The main switching elements 2 and 3 are sequentially connected in series between a positive terminal 101 and a 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 an upper arm and a lower arm in a switching device, and a power supply output terminal 105 may be connected to a midpoint of the main switching elements 2 and 3.

[0021] The main switching elements 2, 3 may have sense emitter terminals connected to the corresponding control devices 4, 5. In addition, thermal diodes 20, 30 for detecting overheating of the main switching elements 2, 3 may be disposed near the main switching elements 2, 3 (in the same chip as the main switching elements 2, 3, as an example in this embodiment), and the anode terminals and cathode terminals of the thermal diodes 20, 30 may be connected to the control devices 4, 5.

[0022] In this embodiment, as an example, the main switching elements 2 and 3 are IGBTs and may have a parasitic diode (not shown) whose cathode is on the positive terminal 101 side. In addition to this, or instead of this, a free wheel diode (not shown) may be connected in anti-parallel to each of the main switching elements 2 and 3 so that the positive terminal 101 side becomes the cathode. The main switching elements 2 and 3 may be semiconductor elements of other structures, such as MOSFETs or bipolar transistors.

[0023] [1.1.2. Control devices 4, 5] The controllers 4 and 5 control the main switching elements 2 and 3. The positive side controller 4 may control the main switching element 2, and the negative side controller 5 may control the main switching element 3. Since the controllers 4 and 5 have the same configuration, in this embodiment, the negative side controller 5 will be described, and the description of the positive side controller 4 will be omitted.

[0024] The control device 5 controls the main switching element 3. The control device 5 includes a drive control unit 50, an abnormality detection unit 6, a protection operation control unit 56, an alarm output unit 57, and a protection unit 58. The drive control unit 50 and the protection operation control unit 56 may receive power from different power sources. For example, among the components in the control device 5, the drive control unit 50 and the other components may receive power from different power sources. In the present embodiment, as an example, the drive control unit 50 may receive power supply of a voltage (also referred to as a control voltage) Vcc(1) from one power source, and the other components in the control device 5 may receive power supply of a voltage (also referred to as a control voltage) Vcc(2) from another power source. The voltages Vcc(1) and Vcc(2) may be the same voltage or different voltages.

[0025] [1.1.2(1). Drive control unit 50] The drive control unit 50 drives and controls the main switching element 3 in response to a drive signal Vin input to the input terminal 103. The drive signal Vin may be input from the outside and may include a signal for turning the main switching element 3 on and a signal for turning it off. For example, the drive signal Vin may cause the main switching elements 2 and 3 to perform switching using a synchronous rectification method, and may be set to alternatively (alternately, for example) turn the main switching elements 2 and 3 into a connected state with a dead time in which both the main switching elements 2 and 3 are turned off sandwiched therebetween. 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.

[0026] The drive control unit 50 includes a current source 500 , a Zener diode 501 , an inverting Schmitt trigger circuit 502 , a NOT gate 503 , a switching element 504 , and a switching element 505 .

[0027] The current source 500 maintains the potential of the input terminal 103 at a high level when the drive signal Vin that turns the main switching element 3 on is not input to the input terminal 103. The Zener diode 501 is connected between the input terminal 103 and ground with its cathode terminal facing the input terminal 103 side, and prevents an overvoltage from being applied from the input terminal 103 to the control device 5. The inverting Schmitt trigger circuit 502 is connected to the input terminal 103, and inverts the high level / low level of the drive signal Vin with hysteresis. The inverting Schmitt trigger circuit 502 may supply the inverted drive signal Vin to a NOT gate 503 and a switching element 505 via AND gates 581, 582 in a protection unit 58 described later.

[0028] The NOT gate 503 is provided between the AND gate 581 of the protection unit 58 and the switching element 504. The NOT gate 503 may further invert the output signal from the AND gate 581 and supply the inverted signal to the switching element 504.

[0029] The switching element 504 is connected between the power supply of the control voltage Vcc(1) and the gate of the main switching element 3. The switching element 504 is a turn-on switching element, and turns on the main switching element 3 by establishing conduction between the power supply of the control voltage Vcc(1) and the gate of the main switching element 3. The switching element 504 may be turned on when the signal supplied from the NOT gate 503 is at a low level. Note that, as an example, in this embodiment, the switching element 504 is a P-type MOSFET, but may be a semiconductor element of another structure.

[0030] 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 a turn-off switching element, and turns off the main switching element 3 by establishing electrical continuity between the gate of the main switching element 3 and the negative terminal 102. The switching element 505 may be turned on when the signal supplied from the AND gate 582 is at a high level. Note that, as an example, the switching element 505 is an N-type MOSFET in this embodiment, but may be a semiconductor element of another structure.

[0031] [1.1.2(2). Anomaly detection unit 6] The abnormality detection unit 6 detects an abnormality that requires a protective operation. In the present embodiment, as an example, the abnormality includes a short circuit of the main switching element 3, overheating of the main switching element 3, an overcurrent of the main switching element 3, and a control voltage drop. Overheating of the main switching element 3 may be a temperature higher than a reference temperature of the main switching element 3. An overcurrent of the main switching element 3 may be a current flowing through the main switching element 3 that is higher than a reference current. A control voltage drop may be a voltage Vcc(1) supplied by power to the drive control unit 50 that is lower than the reference voltage. The abnormality detection unit 6 has an overheat detection unit 61, a measurement unit 62, an overcurrent detection unit 63, a short circuit detection unit 64, and a control voltage drop detection unit 65.

[0032] [1.1.2(2-1).Overheat detection unit 61] The overheat detection unit 61 detects overheating of the main switching element 3. The overheat detection unit 61 includes a current source 610, a comparator 611, a low-pass filter 612, and a hysteresis buffer 613.

[0033] The current source 610 is connected between the anode terminal of the thermal diode 30 and the inverting input terminal of the comparator 611, and causes a forward current to flow through the thermal diode 30. When the thermal diode 30 is at a temperature higher than the reference temperature, the forward voltage of the thermal diode 30 may be lower than when the thermal diode 30 is at the reference temperature. As a result, when the main switching element 3 is in an overheated state, a voltage lower than when the main switching element 3 is not in an overheated state is applied to the inverting input terminal of the comparator 611. A reference potential is connected to the non-inverting input terminal of the comparator 611. The reference potential of the comparator 611 may be equal to the potential of the inverting input terminal when the main switching element 3 is at the reference temperature. As a result, the output signal of the comparator 611 becomes high level in response to the main switching element 3 being in an overheated state. The comparator 611 may supply an output signal to the protection operation control unit 56 via a low-pass filter 612 and a hysteresis buffer 613.

[0034] The low-pass filter 612 may remove high-frequency components contained in the output signal from the comparator 611. The hysteresis buffer 613 may buffer the output signal from the comparator 611 with hysteresis to prevent fluctuations in the output signal.

[0035] [1.1.2(2-2).Measurement section 62] The measurement unit 62 measures a parameter corresponding 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 switching element 3. In the present embodiment, as an example, the measurement unit 62 may have two resistors 620, 621 connected in series between the sense emitter terminal of the main switching element 3 and ground. The measurement unit 62 may supply to the overcurrent detection unit 63 a voltage detected in response to the sense emitter current flowing through both the resistors 620, 621, and may supply to the short-circuit detection unit 64 a voltage detected in response to the sense emitter current flowing through the resistor 621 on the ground side.

[0036] [1.1.2(2-3).Overcurrent detection unit 63] The overcurrent detection unit 63 detects an overcurrent in the main switching element 3. The overcurrent detection unit 63 may detect that an overcurrent has flowed through the main switching element 3 according to the parameters measured by the measurement unit 62. The overcurrent may be a current larger than a reference current (for example, the rated current of the main switching element 3) and may be a current smaller than the current that flows when the main switching element 3 is short-circuited. The overcurrent detection unit 63 has a comparator 630 and a low-pass filter 631.

[0037] The non-inverting input terminal of the comparator 630 is connected to a connection point between the resistor 620 of the measuring unit 62 and the sense emitter terminal of the main switching element 3, and the inverting input terminal of the comparator 630 is connected to a reference potential. The reference potential of the comparator 630 may be equal to the potential of the non-inverting input terminal when the current flowing through the main switching element 3 is the above-mentioned reference current. This causes the output signal of the comparator 630 to go high level in response to the main switching element 3 going into an overcurrent state. The comparator 630 may supply an output signal to the protection operation control unit 56 via a low-pass filter 631. The low-pass filter 631 may remove high-frequency components included in the output signal from the comparator 630.

[0038] [1.1.2(2-4). Short circuit detection unit 64] The short circuit detection unit 64 detects a short circuit in the main switching element 3. The short circuit detection unit 64 may detect that a short circuit has occurred in the main switching element 3 based on the parameters measured by the measurement unit 62. The short circuit detection unit 64 has a comparator 640 and a low pass filter 641.

[0039] The non-inverting input terminal of the comparator 640 is connected to the connection point between the resistors 620 and 621 of the measuring unit 62, and the inverting input terminal of the comparator 640 is connected to a reference potential. The reference potential of the comparator 640 may be higher than the potential of the non-inverting input terminal when the main switching element 3 is not in a short-circuit state, and may be lower than the potential of the non-inverting input terminal when the main switching element 3 is in a short-circuit state. As a result, the output signal of the comparator 640 becomes high level in response to the main switching element 3 being in a short-circuit state. The comparator 640 may supply an output signal to the protection operation control unit 56 via a low-pass filter 641. The low-pass filter 641 may remove high-frequency components included in the output signal from the comparator 640.

[0040] [1.1.2(2-5). Control voltage drop detection unit 65] The control voltage drop detection unit 65 detects a drop in the control voltage. In the present embodiment, as an example, the control voltage drop detection unit 65 may detect that the control voltage Vcc(1) has dropped. The control voltage drop detection unit 65 includes resistors 655 and 656, a comparator 651, a low-pass filter 652, and a hysteresis buffer 653.

[0041] The resistors 655 and 656 are connected in series between the control voltage Vcc(1) and ground. The connection point between the resistors 655 and 656 may be connected to the inverting input terminal of the comparator 651, and the non-inverting input terminal of the comparator 651 may be connected to a reference potential. The reference potential of the comparator 651 may be equal to the potential of the inverting input terminal when the control voltage Vcc(1) is the reference voltage. As an example, the reference voltage may be the minimum voltage of the control voltage Vcc(1) at which the drive control unit 50 operates normally. As a result, the output signal of the comparator 651 becomes high level in response to the control voltage Vcc(1) decreasing below the reference voltage. The comparator 651 may supply an output signal to the protection operation control unit 56 via a low-pass filter 652 and a hysteresis buffer 653.

[0042] The low-pass filter 652 and the hysteresis buffer 653 may be similar to the low-pass filter 612 and the hysteresis buffer 613 of the overheating detection unit 61 .

[0043] [1.1.2(3).Protection operation control unit 56] The protection operation control unit 56 causes the protection unit 58 to perform a protection operation in response to the occurrence of any of the following abnormalities: a short circuit of the main switching element 3, overheating of the main switching element 3, an overcurrent of the main switching element 3, and a drop in the control voltage. The protection operation control unit 56 may cause the protection unit 58 to perform a protection operation by setting a protection control signal SG supplied to the protection unit 58 to a high level. The protection operation control unit 56 has an OR gate 560, an SR flip-flop 561, a delay circuit 562, an AND gate 563, an SR flip-flop 564, a delay circuit 565, an AND gate 566, and an OR gate 569.

[0044] [1.1.2(3-1).OR gate 560] The OR gate 560 is connected to the output terminals of the overheat detection unit 61, the overcurrent detection unit 63, and the control voltage drop detection unit 65. The OR gate 560 may take a logical OR of the output signals from the overheat detection unit 61, the overcurrent detection unit 63, and the control voltage drop detection unit 65. The OR gate 560 may supply the operation result to an SR flip-flop 561.

[0045] [1.1.2(3-2).SR type flip-flop561] The SR flip-flop 561 is connected to the output terminal of the OR gate 560. The SR flip-flop 561 is an example of a second holding unit, and holds information indicating that a protective operation should be performed when at least one of the following abnormalities occurs: overheating of the main switching element 3, an overcurrent in the main switching element 3, and a drop in the control voltage, until a second release condition described below is satisfied. The SR flip-flop 561 may hold information indicating that a protective operation should be performed by being set, and reset the information by being reset.

[0046] The output terminal of the OR gate 560 may be connected to the set terminal of the SR flip-flop 561, and the SR flip-flop 561 may be set in response to the signal from the OR gate 560 going to a high level. As a result, the SR flip-flop 561 is set in response to the occurrence of at least one abnormality among overheating of the main switching element 3, an overcurrent in the main switching element 3, and a drop in the control voltage.

[0047] An output terminal of an AND gate 563 described below may be connected to a reset terminal of the SR flip-flop 561, and the SR flip-flop 561 may be reset in response to the output signal from the AND gate 563 going high.

[0048] The SR flip-flop 561 may output a high-level signal in the set state and may output a low-level signal in the reset state. The SR flip-flop 561 may supply an output signal to an OR gate 569 and a delay circuit 562.

[0049] [1.1.2(3-3). Delay circuit 562] The delay circuit 562 is connected to the output terminal of the SR flip-flop 561. The delay circuit 562 may output a signal that becomes high level when a reference time or more has elapsed since the start of the high level signal output by the SR flip-flop 561. In the present embodiment, as an example, the delay circuit 562 may output a signal that becomes high level when the high level output signal by the SR flip-flop 561 continues for a reference time or more, and takes a logical product of the output signal of the SR flip-flop 561 and a signal obtained by delaying the output signal of the SR flip-flop 561 by the reference time. The delay circuit 562 may supply an output signal to the AND gate 563. The reference time may be a time that is arbitrarily set for the delay circuit 562. As an example, the reference time may be a minimum time for which the alarm output unit 57 should output the alarm signal ALM.

[0050] [1.1.2(3-4).AND gate 563] The AND gate 563 is provided between the OR gate 560, the delay circuit 562, the inverting Schmitt trigger circuit 502, and the reset terminal of the SR flip-flop 561. The AND gate 563 resets the SR flip-flop 561 in response to the second release condition being satisfied.

[0051] The second release condition includes that the abnormality that occurred among the overheating of the main switching element 3, the overcurrent of the main switching element 3, and the drop in the control voltage has been resolved, that the drive signal Vin that turns the main switching element 3 to the ON state is not being supplied, and that a reference time or more has elapsed since the start of the protection operation. Here, unlike the first release condition described below, the second release condition does not include the condition that the power supply to the drive control unit 50 is stopped. The fact that the abnormality has been resolved may mean that no abnormality is occurring. The fact that the drive signal Vin that turns the main switching element 3 to the ON state is not being supplied may mean that the supply of the drive signal Vin is stopped, or that the drive signal Vin that turns the main switching element 3 to the OFF state is being supplied.

[0052] In this embodiment, as an example, the AND gate 563 may detect whether the second release condition is satisfied by calculating the logical product of an inverted signal of an output signal from the OR gate 560 (as an example in this embodiment, the logical sum of output signals from the overheat detection unit 61, the overcurrent detection unit 63, and the control voltage drop detection unit 65), an inverted signal of an output signal from the inverting Schmitt trigger circuit 502 (as an example in this embodiment, the inverted drive signal Vin), and an output signal from the delay circuit 562. The AND gate 563 may supply the calculation result to the reset terminal of the SR flip-flop 561.

[0053] [1.1.2(3-5).SR type flip-flop564] The SR flip-flop 564 is connected to the output terminal of the short-circuit detection unit 64. The SR flip-flop 564 is an example of a first holding unit, and when a short circuit occurs, holds information that a protective operation should be performed until a first release condition described below is satisfied. The SR flip-flop 564 may hold information that a protective operation should be performed by being in a set state, and reset the information by being reset.

[0054] The output terminal of the short circuit detection unit 64 may be connected to the set terminal of the SR flip-flop 564, and the SR flip-flop 564 may be set in response to the signal from the short circuit detection unit 64 going to a high level. As a result, the SR flip-flop 564 is set when a short circuit occurs in the main switching element 3.

[0055] An output terminal of an AND gate 566, which will be described later, may be connected to the reset terminal of the SR flip-flop 564, and the SR flip-flop 564 may be reset in response to the output signal from the AND gate 566 going high.

[0056] The SR flip-flop 564 may output a high-level signal in the set state and may output a low-level signal in the reset state. The SR flip-flop 564 may supply an output signal to an OR gate 569 and a delay circuit 565.

[0057] [1.1.2(3-6). Delay circuit 565] The delay circuit 565 is connected to the output terminal of the SR flip-flop 564. The delay circuit 565 may output a signal that becomes high level when a reference time or more has elapsed since the start of the high level signal output by the SR flip-flop 564. In the present embodiment, as an example, the delay circuit 565 may output a signal that becomes high level when the high level output signal by the SR flip-flop 564 continues for a reference time or more, and takes a logical product of the output signal of the SR flip-flop 564 and a signal obtained by delaying the output signal of the SR flip-flop 564 by the reference time. The delay circuit 565 may supply an output signal to an AND gate 566. The reference time may be a time that is arbitrarily set for the delay circuit 565. As an example, the reference time may be a minimum time for which the alarm output unit 57 should output the alarm signal ALM.

[0058] [1.1.2(3-7).AND gate 566] The AND gate 566 is provided between the short circuit detection unit 64, the control voltage drop detection unit 65, the delay circuit 565, the inverting Schmitt trigger circuit 502, and the reset terminal of the SR flip-flop 564. The AND gate 566 is an example of a reset unit, and resets the SR flip-flop 564 in response to the first release condition being satisfied.

[0059] The first release condition includes that the short circuit has been eliminated and that the power supply to the drive control unit 50 has been stopped. As a result, if a short circuit occurs, the protection operation of the protection unit 58 continues until the power supply to the drive control unit 50 is stopped. The elimination of the short circuit may mean that no short circuit has occurred. The power supply being stopped may mean that the power supply is stopped, or may mean that the power supply has been temporarily stopped. The first release condition may further include that the drive signal Vin that turns the main switching element 3 to an on state is not being supplied, and that a reference time or more has elapsed since the start of the protection operation.

[0060] In the present embodiment, as an example, the AND gate 566 may take a logical product of an inverted signal of an output signal from the short circuit detection unit 64, an inverted signal of a voltage signal detected by the resistors 655 and 656 of the control voltage drop detection unit 65, an inverted signal of an output signal from the inverting Schmitt trigger circuit 502 (as an example in the present embodiment, the inverted drive signal Vin), and an output signal from the delay circuit 565. Here, the voltage signal detected by the resistors 655 and 656 of the control voltage drop detection unit 65 may be at a high level unless the power supply to the drive control unit 50 is stopped, and may be at a low level when the power supply is stopped. The AND gate 566 may supply the calculation result to a reset terminal of the SR flip-flop 564.

[0061] [1.1.2(3-8).OR gate 569] The OR gate 569 is connected to the output terminals of the SR flip-flops 561 and 564. The OR gate 569 may take the logical sum of the output signals of the SR flip-flops 561 and 564. The OR gate 569 may supply a signal resulting from the calculation to the protection unit 58 and the alarm output unit 57 as a protection control signal SG.

[0062] [1.1.2(4).Alarm output section 57] The alarm output unit 57 is an example of an output unit, and outputs an alarm signal ALM from the alarm terminal 104 when a protective operation is performed. The alarm signal ALM may be at a high level when a protective operation is not performed, and may be at a low level when a protective operation is performed to alert an operator. A resistor 571 may be connected to the alarm terminal 104. The alarm output unit 57 has a current source 572, a switching element 573, and an inverting Schmitt trigger circuit 574.

[0063] The current source 572 is connected to the alarm terminal 104, and maintains the alarm signal ALM output from the alarm terminal 104 at a high level by flowing a current from the alarm terminal 104 to the outside via the resistor 571. The switching element 573 is connected between the connection point between the current source 572 and the alarm terminal 104 and the ground. The switching element 573 is normally off, and is turned on in response to a protection control signal SG from the protection operation control unit 56 going to a high level when a protection operation is to be performed, and flows a current from the current source 572 to the ground. As a result, the alarm signal ALM output from the alarm terminal 104 goes to a low level. The switching element 573 may be an N-type MOSFET, for example. The inverting Schmitt trigger circuit 574 is connected to the alarm terminal 104, and inverts the high level / low level of the alarm signal ALM with hysteresis. The first threshold when the alarm signal ALM switches from a low level to a high level may be higher than the second threshold when the alarm signal ALM switches from a high level to a low level. As a result, even if the protection control signal SG from the protection operation control unit 56 switches from a high level to a low level, the output of the inverting Schmitt trigger circuit 574 is maintained at a high level until the alarm signal ALM exceeds the second threshold and becomes reliably at a high level. The inverting Schmitt trigger circuit 574 may supply an inverted alarm signal ALM to the protection unit 58.

[0064] [1.1.2(5).Protection section 58] The protection unit 58 performs a protection operation to limit the current flowing through the main switching element 3 in response to detection of an abnormality such as overheating, overcurrent, short circuit, or control voltage drop. The protection unit 58 may perform the protection operation in response to detection of an abnormality by the overheating detection unit 61, the overcurrent detection unit 63, the short circuit detection unit 64, or the control voltage drop detection unit 65. The protection unit 58 has an OR gate 580, AND gates 581 and 582, a NOT gate 583, and a switching element 584.

[0065] The OR gate 580 is connected to the output terminals of the protection operation control unit 56 and the alarm output unit 57. The OR gate 580 may take a logical sum of the protection control signal SG from the protection operation control unit 56 and an inverted signal of the alarm signal ALM from the inverting Schmitt trigger circuit 574 of the alarm output unit 57. The OR gate 580 may supply the calculation result to an AND gate 582 and a NOT gate 583.

[0066] The AND gate 581 is connected to the output terminal of the inverting Schmitt trigger circuit 502 of the drive control unit 50, the protection operation control unit 56, and the alarm output unit 57. The AND gate 581 may take a logical AND of the drive signal Vin inverted by the inverting Schmitt trigger circuit 502 of the drive control unit 50, an inverted signal of the protection control signal SG from the protection operation control unit 56, and a further inverted signal of the inverted signal of the alarm signal ALM by the inverting Schmitt trigger circuit 574 of the alarm output unit 57.

[0067] As a result, when the protection control signal SG commands the execution of a protection operation and / or when an alarm is issued by the alarm signal ALM, the output of the AND gate 581 becomes low level regardless of the output signal of the inverting Schmitt trigger circuit 502, and further regardless of the drive signal Vin. In addition, when the protection control signal SG does not command the execution of a protection operation and an alarm is not issued by the alarm signal ALM, the output of the AND gate 581 matches the output of the inverting Schmitt trigger circuit 502.

[0068] The AND gate 581 may supply an output signal to a switching element 504 for turning on the main switching element 3 via the NOT gate 503. As a result, when the protection control signal SG instructs execution of a protection operation and / or when an alarm is issued by the alarm signal ALM, the switching element 504 is maintained in an off state regardless of the drive signal Vin. Also, when the protection control signal SG does not instruct execution of a protection operation and when an alarm is not issued by the alarm signal ALM, the switching element 504 is controlled in response to the drive signal Vin. AND gate 581 may also provide an output signal to AND gate 582 .

[0069] The AND gate 582 is connected to the output terminals of the AND gate 581 and the OR gate 580. The AND gate 582 may take a logical AND of an inverted signal of the output signal of the AND gate 581 and an inverted signal of the output signal of the OR gate 580.

[0070] As a result, when the protection control signal SG commands the execution of a protection operation and / or when an alarm is issued by the alarm signal ALM, the output of the AND gate 582 becomes low level regardless of the output signal of the AND gate 581, and therefore the output signal of the inverting Schmitt trigger circuit 502 and the drive signal Vin. Also, when the protection control signal SG does not command the execution of a protection operation and no alarm is issued by the alarm signal ALM, the output of the AND gate 582 matches the inverted signal of the output signal of the AND gate 581, and therefore the inverted signal of the output of the inverting Schmitt trigger circuit 502 and the drive signal Vin.

[0071] The AND gate 582 may supply an output signal to the switching element 505 for turning off the main switching element 3. As a result, when the protection control signal SG instructs execution of a protection operation and / or when an alarm is issued by the alarm signal ALM, the switching element 505 is maintained in the off state regardless of the drive signal Vin. Also, when the protection control signal SG does not instruct execution of a protection operation and when an alarm is not issued by the alarm signal ALM, the switching element 505 is controlled according to the drive signal Vin.

[0072] The NOT gate 583 is connected to the output terminal of the OR gate 580, and inverts the output signal of the OR gate 580. The NOT gate 583 may provide an output signal to a switching element 584.

[0073] The switching element 584 is connected in parallel with the switching element 505 between the gate of the main switching element 3 and the negative terminal 102. The switching element 584 is a switching element for soft-shutdown of the main switching element 3, and turns off the main switching element 3 by conducting between the gate of the main switching element 3 and the negative terminal 102. The switching speed of the switching element 584 may be lower than the switching speed of the switching element 505. The switching element 505 may be turned on when the signal supplied from the NOT gate 583 is at a low level. Note that, as an example, the switching element 505 is a P-type MOSFET in this embodiment, but may be a semiconductor element of another structure.

[0074] According to the above switching device 1, the protective operation performed in response to the occurrence of a short circuit continues until the power supply to the drive control unit 50 is stopped. This prevents the protective operation from being released without removing the cause of the short circuit, and prevents secondary damage to the element due to the release of the protective operation.

[0075] Furthermore, when a short circuit occurs, information indicating that a protective operation should be performed is held in the SR flip-flop 564 until the first release condition, which includes that the short circuit is eliminated and the power supply is stopped, is satisfied. This makes it possible to reliably prevent the protective operation from being released without removing the cause of the short circuit.

[0076] Furthermore, since the SR flip-flop 564 is reset in response to the first release condition being satisfied, when the first release condition is satisfied, the protective operation can be released and normal operation can be resumed.

[0077] The first release condition further includes that the drive signal Vin that turns the main switching element 3 to the ON state is not being supplied, so that the protective operation can be released in a state in which the main switching element 3 is OFF, and operation can be resumed. The first release condition also includes that a reference time or more has elapsed since the start of the protective operation, so that it is possible to prevent short circuits from occurring consecutively within the reference time. Furthermore, the protective operation is not released until at least the reference time has elapsed, so that the alarm signal ALM can be output continuously over the reference time.

[0078] Furthermore, if at least one of the abnormalities of overheating of the main switching element 3, overcurrent of the main switching element 3, and a drop in the control voltage occurs, information indicating that a protective operation should be performed is held in the SR flip-flop 561 until the second release condition is satisfied. The second release condition includes that the abnormality has been resolved, that the drive signal Vin that turns the main switching element 3 into the on state is not being supplied, and that a reference time or more has elapsed since the start of the protective operation, but does not include that the power supply is stopped. Therefore, in the protective operation due to overheating or overcurrent of the main switching element 3 or a drop in the control voltage Vcc(1), the protective operation can be quickly released without requiring that the power supply be stopped, and normal operation can be resumed.

[0079] Furthermore, when a protective operation is performed, an alarm signal ALM is output, so that an abnormality can be notified and the cause of the abnormality can be removed or the power supply can be stopped.

[0080] Furthermore, since the protective operation control section 56 receives power from a power source separate from that of the drive control section 50, the protective operation control section 56 can continue to perform control even if the power supply to the drive control section 50 is stopped.

[0081] [2. Second embodiment] Fig. 2 shows a switching device 1A according to a second embodiment. A control device 5A of the switching device 1A includes an abnormality detection unit 6A and a protection operation control unit 56A. Note that the main switching element 2 and its control device are not shown in Fig. 2 and Figs. 3 and 4 described later. 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 given the same reference numerals, and descriptions thereof will be omitted.

[0082] The abnormality detection unit 6A has an OR gate 66A connected to the output terminals of the overcurrent detection unit 63 and the short circuit detection unit 64. The OR gate 66A may take a logical OR of the output signals of the overcurrent detection unit 63 and the short circuit detection unit 64, and supply the calculation result to the protection operation control unit 56A.

[0083] The protective operation control unit 56A may have an OR gate 560A, an SR flip-flop 564A, an AND gate 563A, and an SR flip-flop 561A.

[0084] The OR gate 560A is connected to the output terminals of the overheat detection unit 61, the OR gate 66A, and the control voltage drop detection unit 65. The OR gate 560A may take a logical OR of the output signals from the overheat detection unit 61, the OR gate 66A, and the control voltage drop detection unit 65. The OR gate 560A may supply the calculation result to a set terminal of the SR flip-flop 561A. As a result, a logical OR is taken of the output signals from the overheat detection unit 61, the overcurrent detection unit 63, the short circuit detection unit 64, and the control voltage drop detection unit 65, and the SR flip-flop 561A is set in response to any one of the output signals becoming high level.

[0085] The SR flip-flop 564A is connected to the output terminal of the short circuit detection unit 64 and the AND gate 566. As with the SR flip-flop 564 in the first embodiment described above, the SR flip-flop 564A may be set in response to the signal from the short circuit detection unit 64 going to a high level, and may be reset in response to the output signal from the AND gate 566 going to a high level. The SR flip-flop 564A may supply a high level signal in the set state and a low level signal in the reset state to the delay circuit 565 and the AND gate 563A.

[0086] The AND gate 563A is provided between the OR gate 560, the delay circuit 562, the inverting Schmitt trigger circuit 502, the SR flip-flop 564A, and the reset terminal of the SR flip-flop 561A. The AND gate 563A resets the SR flip-flop 561A in response to the third release condition being satisfied.

[0087] The third release condition does not include the condition that the power supply to the drive control unit 50 is stopped, and includes the above-mentioned second release condition as well as the output of the SR flip-flop 564A being at a low level. As a result, if no short circuit has occurred, the output signal of the SR flip-flop 564A is at a low level, so the AND gate 563A resets the SR flip-flop 561A in response to the remaining condition of the third release condition, that is, the second release condition, being satisfied. On the other hand, once a short circuit has occurred, the output signal of the SR flip-flop 564A is at a high level until the first release condition is satisfied, so the AND gate 563A does not reset the SR flip-flop 561A regardless of whether the remaining condition of the third release condition, that is, the second release condition, is satisfied. Once a short circuit occurs and the first release condition is satisfied, the output signal of the SR flip-flop 564A is at a low level, so that the AND gate 563A resets the SR flip-flop 561A in response to the remaining condition of the third release condition, i.e., the second release condition, being satisfied.

[0088] In the present embodiment, as an example, the AND gate 563A may detect whether the third release condition is satisfied by calculating the logical product of an inverted signal of the output signal from the OR gate 560A, an inverted signal of the output signal from the inverting Schmitt trigger circuit 502, an output signal from the delay circuit 562, and an inverted signal of the output signal from the SR flip-flop 564A. The AND gate 563A may supply the calculation result to the reset terminal of the SR flip-flop 561A.

[0089] The SR flip-flop 561A is connected to the output terminals of the OR gate 560A and the AND gate 562A. As with the SR flip-flop 561 in the first embodiment described above, the SR flip-flop 561A may be set in response to a signal from the OR gate 560A going to a high level, and may be reset in response to an output signal from the AND gate 566A going to a high level. The SR flip-flop 561A may supply a high level signal in a set state and a low level signal in a reset state to the delay circuit 562 and the drive control unit 50.

[0090] The above switching device 1A can also provide the same effects as the switching device 1 in the first embodiment.

[0091] [3. Third embodiment] 3 shows a switching device 1B according to a third embodiment. The switching device 1B includes an operation detection terminal 108 and a control device 5B.

[0092] The operation detection terminal 108 detects the input of a reference operation when power supply is resumed. The reference operation may be an operation to instruct the drive control unit 50 to start power supply (for example, an operation on the power button), an operation to instruct initialization to be performed after startup of the switching device 1B or the control device 5B, or the like. When the reference operation is performed, a high-level signal may be supplied from the operation detection terminal 108 to the control device 5B.

[0093] The control device 5B includes an SR flip-flop 564B and an AND gate 566B. The SR flip-flop 564B is connected to the output terminal of the short circuit detection unit 64. The SR flip-flop 564B holds information indicating that a protective operation should be performed until the first release condition according to this embodiment is satisfied.

[0094] Here, the first release condition in this embodiment includes, when a short circuit occurs, that the short circuit has been eliminated and that a reference operation for resuming power supply has been performed. As a result, when a short circuit occurs, the protection operation of the protection unit 58 continues until the reference operation for resuming power supply is performed. The first release condition may further include that the drive signal Vin for turning on the main switching element 3 is not being supplied and that a reference time or more has elapsed since the start of the protection operation.

[0095] An AND gate 566B may be connected to a reset terminal of the SR flip-flop 564B, and the SR flip-flop 564B may be reset in response to an output signal from the AND gate 566B going to a high level. The SR flip-flop 564B may supply an output signal to a delay circuit 565 and an OR gate 569.

[0096] The AND gate 566B is provided between the short circuit detection unit 64, the operation detection terminal 108, the delay circuit 565, the inverting Schmitt trigger circuit 502, and the reset terminal of the SR flip-flop 564B. The AND gate 566B resets the SR flip-flop 564B in response to the first release condition being satisfied. In the present embodiment, as an example, the AND gate 566B may take a logical product of an inverted signal of the output signal from the short circuit detection unit 64, a signal from the operation detection terminal 108, an inverted signal of the output signal from the inverting Schmitt trigger circuit 502 (in the present embodiment, as an example, the inverted drive signal Vin), and an output signal from the delay circuit 565. The AND gate 566 may supply the operation result to the reset terminal of the SR flip-flop 564B.

[0097] According to the above switching device 1B, when a short circuit occurs, information indicating that a protective operation should be performed is held in the SR flip-flop 564B until the first release condition is satisfied, including that the short circuit is eliminated and that the reference operation for resuming power supply is performed. Therefore, it is possible to reliably prevent the protective operation from being released without removing the cause of the short circuit.

[0098] Furthermore, since the SR flip-flop 564B is reset in response to the first release condition being satisfied, when the first release condition is satisfied, the protective operation can be released and normal operation can be resumed.

[0099] In this embodiment, the SR flip-flop 564B has been described as supplying an output signal to the OR gate 569, but the output signal may be supplied to the AND gate 563 in the same manner as the SR flip-flop 564A in the second embodiment.

[0100] [4. Fourth embodiment] FIG. 4 shows a switching device 1C according to a fourth embodiment.

[0101] A protection operation control unit 56C of the control device 5C in the switching device 1C is supplied with power from a power source common to the drive control unit 50. For example, each component in the control device 5C may be supplied with power of a voltage Vcc from a common power source. The protection operation control unit 56C has an OR gate 568C, an SR flip-flop 561C, and an AND gate 563C.

[0102] The OR gate 568C is provided between the short circuit detection unit 64 and the AND gate 563C, and latches a high-level output signal when a short circuit is detected by the short circuit detection unit 64. The OR gate 568C may take a logical OR of the output signal of the short circuit detection unit 64 and the output signal of the OR gate 568C itself. As a result, once the output signal from the short circuit detection unit 64 becomes high level, the output signal of the OR gate 568C is maintained at high level. The OR gate 568C may supply an output signal to the AND gate 563C.

[0103] The SR flip-flop 561C is connected to the output terminals of the OR gate 560 and the AND gate 563C. The SR flip-flop 561C is an example of a third holding unit, and holds information on whether or not to continue the protection operation in response to the protection operation control unit 56C receiving power from a power supply common to the drive control unit 50. The SR flip-flop 561C may hold information indicating that the protection operation should be performed by being in a set state, and reset the information by being reset.

[0104] The SR flip-flop 561C may be set in response to the signal from the OR gate 560 going high, and may be reset in response to the output signal from the AND gate 563C going high, similar to the SR flip-flop 561 in the first embodiment described above. The SR flip-flop 561C may supply an output signal to the OR gate 569 and the delay circuit 562.

[0105] The AND gate 563C is provided between the OR gate 560, the delay circuit 562, the inverting Schmitt trigger circuit 502, and the OR gate 568C, and the reset terminal of the SR flip-flop 561C. The AND gate 563C resets the SR flip-flop 561C in response to the fourth release condition being satisfied.

[0106] The fourth release condition includes, in addition to the second release condition described above, the output of the OR gate 568C being at a low level. As a result, if no short circuit has occurred, the output signal of the OR gate 568C is at a low level, so the AND gate 563C resets the SR flip-flop 561C in response to the remaining condition of the fourth release condition, that is, the second release condition, being satisfied. On the other hand, once a short circuit has occurred, the output signal of the OR gate 568C is maintained at a high level, so the AND gate 563C does not reset the SR flip-flop 561C regardless of whether the remaining condition of the fourth release condition, that is, the second release condition, is satisfied. Therefore, once a short circuit has occurred, the SR flip-flop 561C is maintained in a set state as long as the power supply is maintained, and is reset in response to the power supply being stopped.

[0107] In the present embodiment, as an example, the AND gate 563C may detect whether the fourth release condition is satisfied by calculating a logical product of an inverted signal of the output signal from the OR gate 560, an inverted signal of the output signal from the inverting Schmitt trigger circuit 502, an output signal from the delay circuit 562, and an inverted signal of the output signal from the OR gate 568C. The AND gate 563C may supply the calculation result to the reset terminal of the SR flip-flop 561C.

[0108] According to the above switching device 1C, information on whether or not to continue the protective operation is held in the SR flip-flop 561C in response to the protective operation control unit 56C receiving power from a power source common to the drive control unit 50. Therefore, the protective unit 58 can be made to continue the protective operation reliably until the power supply to the drive control unit 50 is stopped. In addition, since the information is reset when the power supply is stopped, the protective operation can be released and normal operation can be resumed.

[0109] [5. Modifications] In the above embodiment, the control device 5 has been described as having the drive control unit 50 and the alarm output unit 57, but it is not necessary to have at least one of them. Also, the abnormality detection unit 6 has been described as having the overheat detection unit 61, the overcurrent detection unit 63, and the control voltage drop detection unit 65, but it is not necessary to have at least one of them.

[0110] In addition, although the above description has been given of using the voltage detected in response to the sense emitter current of the main switching element 3 flowing through resistors 620 and 621 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 in response to the emitter current of the main switching element 3 flowing through a resistor.

[0111] In addition, the protection unit 58 has been described as soft-shutting down the main switching element 3 when an abnormality such as a short circuit or overcurrent occurs, but the gate voltage of the main switching element 3 may be reduced to and maintained at a reference voltage that is lower than the gate voltage in the steady on state.

[0112] Although the present invention has been described above using the embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various modifications and improvements can be made to the above embodiments. It is clear from the claims that such modifications and improvements can also be included in the technical scope of the present invention.

[0113] It should be noted that the order of execution of each process, such as operations, procedures, steps, and stages, in the devices, systems, programs, and methods shown in the claims, specifications, and drawings is not specifically indicated as "before," "prior to," etc., and may be realized in any order unless the output of a previous process is used in a later process. Even if the operational flow in the claims, specifications, and drawings is explained using "first," "next," etc. for convenience, it does not mean that it is essential to perform the process in this order. [Explanation of symbols]

[0114] 1 Switching device 2 Main switching element 3 Main switching element 4. Control device 5. Control device 6. Anomaly detection section 20 Thermal Diode 30 Thermal Diode 50 Drive control unit 56 Protection operation control section 57 Alarm output section 58 Protection Department 61 Overheat detection unit 62 Measuring part 63 Overcurrent detection section 64 Short circuit detection section 65 Control voltage drop detection unit 66 OR Gate 101 Positive terminal 102 Negative terminal 103 Input terminal 104 Alarm terminal 105 Power output terminal 108 Operation detection terminal 500 current source 501 Zener Diode 502 Inverting Schmitt Trigger Circuit 503 NOT Gate 504 Switching element 505 Switching element 560 OR Gate 561 SR type flip-flop 562 Delay Circuit 563 AND Gate 564 SR type flip-flop 565 Delay Circuit 566 AND Gate 568 OR Gate 569 OR Gate 571 Resistance 572 Current source 573 Switching Elements 574 Inverting Schmitt Trigger Circuit 580 OR Gate 581 AND Gate 582 AND Gate 583 NOT Gate 584 Switching Elements 610 Current source 611 Comparator 612 Low-pass filter 613 Hysteresis Buffer 620 Resistance 621 Resistance 630 Comparator 631 Low-pass filter 640 Comparator 641 Low-pass filter 651 Comparator 652 Low-pass filter 653 Hysteresis Buffer 655 Resistance

Claims

1. a protection unit that performs a protection operation to limit a current flowing through a main switching element in response to a short circuit occurring in the main switching element; a protection operation control unit that stops power supply to a drive control unit that drives and controls the main switching element in response to a drive signal and causes the protection unit to continue a protection operation until the short circuit that has occurred in the main switching element is eliminated; A control device comprising:

2. The protection operation control unit is 2. The control device according to claim 1, further comprising a first holding unit that holds information indicating that the protective operation should be performed when the short circuit occurs until a first release condition is satisfied, the first release condition including that the short circuit is eliminated and that the power supply is stopped.

3. The protection operation control unit is 2. The control device according to claim 1, further comprising a first holding unit that holds information indicating that the protective operation should be executed when the short circuit occurs until a first release condition is satisfied, the first release condition including that the short circuit is eliminated and that a standard operation for resuming the power supply is performed.

4. The control device according to claim 2 , wherein the protection operation control unit includes a reset unit that resets the first holding unit in response to the first release condition being satisfied.

5. 3. The control device according to claim 2, wherein the first release condition further includes that the drive signal for turning on the main switching element is not being supplied, and that a reference time or more has elapsed since the start of the protection operation.

6. the protection unit also performs the protection operation in response to at least one abnormality occurring, that is, the main switching element becomes hotter than a reference temperature, a current larger than a reference current flows through the main switching element, and a voltage supplied by the power supply becomes lower than a reference voltage; 3. The control device according to claim 2, wherein the protection operation control unit has a second holding unit that holds information indicating that the protection operation should be executed when the at least one abnormality occurs, until a second release condition is satisfied, the second release condition including that the abnormality that occurred has been resolved, that the drive signal that turns on the main switching element is not being supplied, and that a reference time or more has elapsed since the start of the protection operation, but that does not include that the power supply is stopped.

7. The control device according to claim 2 , wherein the protection operation control unit is supplied with power from a power source separate from that of the drive control unit.

8. The control device according to claim 1 , wherein the protection operation control unit has a third storage unit that stores information on whether or not to continue the protection operation in response to receiving power from a power source common to the drive control unit.

9. a measurement unit for measuring a parameter corresponding to a current flowing through the main switching element; a detection unit that detects that a short circuit has occurred in the main switching element in response to a measured parameter; The control device of claim 1 further comprising:

10. The control device according to claim 1 , further comprising an output unit that outputs an alarm signal when the protective operation is performed.

11. The control device according to claim 1 , further comprising the drive control unit.

12. A switching device comprising the control device according to claim 11 and the main switching element.

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