Control device, semiconductor cutoff system, control method, and control program

Abstract

To provide a control device, etc., capable of also suppressing an increase of a surge voltage while suppressing a flow of overcurrent / short-circuit current to a load side when cutting off the overcurrent / short-circuit current.SOLUTION: A control device (1) comprises a control section (10) which sets a gate voltage, and a semiconductor switch driver circuit (5) which applies the gate voltage which is set in the control section to a semiconductor switch (2). When cutting off overcurrent / short-circuit current, on the basis of a current value which is obtained from a detection result inputted from a current sensor, the control section reduces the gate voltage at high speed until the current value flowing to the semiconductor switch is not increased and, after the current value flowing to the semiconductor switch is not increased, reduces the gate voltage at low speed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a control device for a semiconductor switch that performs a cutoff operation. [Background technology]

[0002] 2. Description of the Related Art In power converters, semiconductor circuit breakers, and the like, surge voltages that occur when semiconductor switches are turned off are suppressed.

[0003] For example, Patent Document 1 discloses a gate driver configuration in which a gate voltage pattern generator 101, a gate voltage drive amplifier 102, and a switching element 103 which is an IGBT are connected in series, as shown in Fig. 7. Fig. 7 is a diagram showing a conventional gate driver configuration.

[0004] The switching element 103 is controlled by the gate voltage pattern generator 101. Figure 8 shows the gate drive pattern of the switching element 103. As shown in Figure 8, when the switching element is turned on, the gate-emitter voltage rises from negative to positive without any control. When the switching element is turned off, the gate-emitter voltage is given a gradient in each of periods A, B, and C.

[0005] During period A, the gate-emitter voltage is rapidly reduced to the voltage immediately before switching begins. This effectively prevents overcurrent and short-circuit current from flowing to the load side. During period B, the gate-emitter voltage is gradually reduced to the voltage at which switching begins. This makes it possible to suppress surge voltages. During period C, the gate-emitter voltage is rapidly reduced to a negative value, turning the switching element 103 completely off. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 3692740 Summary of the Invention [Problem to be solved by the invention]

[0007] However, in the conventional gate driver configuration described above, the speed at which the gate-emitter voltage is reduced is fixed during periods A, B, and C. Therefore, when cutting off overcurrents and short-circuit currents, the drain current changes rapidly due to the gate-emitter voltage being rapidly reduced during period A, which may cause the gate-emitter voltage to reach the threshold voltage and increase the surge voltage.

[0008] The present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a control device, etc. that, when an overcurrent or short-circuit current is interrupted, prevents the overcurrent or short-circuit current from flowing to the load side while also preventing an increase in surge voltage. [Means for solving the problem]

[0009] In order to solve the above problem, a control device according to one aspect of the present disclosure is a semiconductor interruption system including a semiconductor switch having one end connected to a power source and the other end connected to a load, for interrupting a current from the power source to the load, and a current sensor for detecting a current flowing from the power source to the semiconductor switch, the control device applying a gate voltage to the semiconductor switch to control it, and including a control unit that sets the gate voltage, and a driver circuit that applies the gate voltage set by the control unit to the semiconductor switch, and when interrupting an overcurrent or short-circuit current, the control unit quickly reduces the gate voltage until the value of the current flowing to the semiconductor switch stops increasing based on the current value obtained from the detection result input from the current sensor, and after the value of the current flowing to the semiconductor switch stops increasing, the control unit slowly reduces the gate voltage.

[0010] Moreover, a semiconductor shutoff system according to one aspect of the present disclosure includes a semiconductor switch having one end connected to a power source and the other end connected to a load, for shutting off current from the power source to the load, a current sensor for detecting current flowing from the power source to the semiconductor switch, and the above-mentioned control device.

[0011] Moreover, a control method according to one aspect of the present disclosure is a control method for applying a gate voltage to a semiconductor switch in a semiconductor shutoff system including a semiconductor switch having one end connected to a power source and the other end connected to a load, for shutting off a current from the power source to the load, and a current sensor for detecting a current flowing from the power source to the semiconductor switch, the control method including a shutoff necessity determination step for determining whether or not shutoff of an overcurrent or short-circuit current is necessary, a first shutoff processing step for, when it is determined that shutoff of an overcurrent or short-circuit current is necessary, rapidly reducing the gate voltage until the value of the current flowing in the semiconductor switch no longer increases based on the current value obtained from the detection result input from the current sensor, and a second shutoff processing step for slowly reducing the gate voltage after the value of the current flowing in the semiconductor switch no longer increases.

[0012] In addition, a control device according to one aspect of the present disclosure may be realized by a computer, in which case the control program of the control device that causes the computer to operate as each part (software element) of the control device to realize the control device on the computer, and the computer-readable recording medium on which it is recorded, also fall within the scope of the present disclosure. [Effects of the Invention]

[0013] According to one aspect of the present disclosure, it is possible to provide a control device, etc., that, when an overcurrent or short-circuit current is interrupted, prevents the overcurrent or short-circuit current from flowing to the load side while also preventing an increase in surge voltage. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram illustrating a control device according to an embodiment of the present disclosure and a semiconductor shutdown system including the control device; [Figure 2] 4 is a flowchart showing an example of the operation of a control unit of the control device. [Figure 3]10 is a graph showing an example of an attenuation constant setting function used by the attenuation constant setting unit of the control unit to set the attenuation constant according to the current flow. [Figure 4] 10 is a graph showing an example of an attenuation constant setting function used by an attenuation constant setting unit of the control unit to set an attenuation constant depending on a gate-source voltage. [Figure 5] FIG. 10 is a waveform diagram of gate-source voltages illustrating an example of operation of the control device when the cutoff current is small. [Figure 6] FIG. 10 is a waveform diagram of gate-source voltages illustrating an example of operation of the control device when the cutoff current is large. [Figure 7] FIG. 1 is a diagram illustrating a configuration of a conventional gate driver. [Figure 8] 8 is a diagram showing gate drive patterns of switching elements in the conventional gate driver configuration shown in FIG. 7. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Embodiment] An embodiment of the present disclosure will be described in detail below.

[0016] (Configuration of a power system to which the semiconductor circuit breaker system 50 is applied) 1 is a schematic configuration diagram showing a control device 1 according to an embodiment of the present disclosure and a semiconductor shutdown system 50 including the control device 1. As shown in FIG. 1, the semiconductor shutdown system 50 of this embodiment has a power supply 51 electrically connected to its input side and a load 52 electrically connected to its output side.

[0017] The semiconductor interruption system 50 of this embodiment is a system that appropriately interrupts DC power from the power source 51 side, and the semiconductor interruption system 50 is a semiconductor circuit breaker that interrupts current from the power source 51 to the load 52. Note that the power source 51 is not limited to a DC power source, but may be an AC power source. However, if the power source 51 is an AC power source, an AC-DC converter is installed between the power source 51 and the semiconductor interruption system 50, and the AC power from the power source 51 is converted into DC power by the AC-DC converter and supplied to the semiconductor interruption system 50.

[0018] The load 52 is a device that operates on DC power. The load 52 has an LC filter consisting of a capacitor and a coil on its input side to stabilize the input power and to provide noise suppression. The load 52 also has a capacitor or other power storage device on its input side, which is configured to compensate for the operating voltage in the event of a momentary interruption in the supply of DC power. In addition to the above description, a load 52 that operates on AC power can also be used. In this case, for example, a DC-AC converter that converts the DC power from the semiconductor interruption system 50 into AC power is installed inside the load 52.

[0019] (Configuration of semiconductor shutdown system 50) 1, the semiconductor interruption system 50 of this embodiment includes a first line L1, a second line L2, a semiconductor switch 2, a current sensor 3, and a control device 1. The first line L1 connects a positive electrode (not shown) of a power supply 51 to a load 52. The second line L2 connects a negative electrode (not shown) of the power supply 51 to the load 52.

[0020] The semiconductor switch 2 is located on the first line L1 between the power supply 51 and the load 52, with one end connected to the power supply 51 and the other end connected to the load 52. In this embodiment, a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) is exemplified as the semiconductor switch 2. The semiconductor switch 2 may be any gate voltage controlled switching element, and may also be an IGBT (Insulated Gate Bipolar Transistor) or the like.

[0021] The current sensor 3 is configured using an ammeter such as a known current transformer, and detects the current flowing from the power supply 51 to the semiconductor switch 2. The current sensor 3 outputs the detection result to the control device 1. As shown in FIG. 1, the current sensor 3 is provided between the power supply 51 and the semiconductor switch 2.

[0022] The control device 1 uses the detection result of the current sensor 3 to apply a gate voltage (gate drive voltage) to the semiconductor switch 2, as will be described later, to control the semiconductor switch 2.

[0023] (Configuration of control device 1) The control device 1 includes a current measurement unit 4, a semiconductor switch driver circuit (driver circuit) 5, and a control unit 10. The current measurement unit 4 measures the current value Iin of the current (energizing current) flowing through the semiconductor switch 2 from the detection result of the current flowing through the semiconductor switch 2 input from the current sensor 3. The current measurement unit 4 outputs the measured current value Iin to the control unit 10.

[0024] The semiconductor switch driver circuit 5 drives the semiconductor switch 2 with a gate-source voltage (gate voltage) Vgs input from the control unit 10 , and cuts off the path through which overcurrent and short-circuit current flow to the load 52 .

[0025] The control unit 10 sets the gate-source voltage Vgs. When interrupting an overcurrent or short-circuit current, the control unit 10 quickly reduces the gate-source voltage Vgs until the current value Iin flowing through the semiconductor switch 2 stops increasing, based on the current value Iin obtained from the detection result input from the current sensor 3, and then slowly reduces the gate-source voltage Vgs after the current value Iin flowing through the semiconductor switch 2 stops increasing.

[0026] Specifically, the control unit 10 includes an overcurrent determination unit 11, a first current value memory processing unit 12, an attenuation constant setting unit 13, a gate voltage setting unit 14, a second current value memory processing unit 15, a cut-off current comparison processing unit 16, a voltage value memory processing unit 17, and a voltage comparison processing unit 18.

[0027] The overcurrent determination unit 11 determines whether or not there is an overcurrent based on the current value Iin input from the current measurement unit 4. The overcurrent determination unit 11 has a predetermined cutoff threshold value, and determines that there is an overcurrent when the current value Iin exceeds the cutoff threshold value.

[0028] The first current value memory processing unit 12, the attenuation constant setting unit 13, the gate voltage setting unit 14, the second current value memory processing unit 15, the cut-off current comparison processing unit 16, the voltage value memory processing unit 17, and the voltage comparison processing unit 18 operate when the overcurrent determination unit 11 determines that an overcurrent has occurred.

[0029] The first current value storage processing unit 12 stores the current value Iin input from the current measurement unit 4 in a storage unit (not shown) as a set current value Iin_set, which is a variable of the first attenuation constant Am0.

[0030] The attenuation constant setting unit 13 sets the attenuation constant when the gate-source voltage Vgs is reduced. The attenuation constant setting unit 13 sets the attenuation constant (first attenuation constant) to be large when the current value Iin is small and to be small when the current value Iin is large until the current value Iin stops increasing. After the current value Iin stops increasing, the attenuation constant setting unit 13 sets the attenuation constant (second attenuation constant) to be small until the gate-source voltage Vgs reaches a threshold voltage and to be large after the gate-source voltage Vgs reaches the threshold voltage.

[0031] In this embodiment, until the current value Iin stops increasing, the attenuation constant setting unit 13 sets the first attenuation constant Am0 based on the set current value Iin_set stored by the first current value storage processing unit 12. Specifically, the attenuation constant setting unit 13 sets the first attenuation constant Am0 using a function graph shown in Fig. 3 (described in detail later).

[0032] After the current value Iin stops increasing, the attenuation constant setting unit 13 sets the second attenuation constant Am1 based on the set voltage value Vgs_set stored by the voltage value storage processing unit 17. Specifically, the attenuation constant setting unit 13 sets the second attenuation constant Am1 using a graph of a function shown in FIG. 4 (to be described later in detail).

[0033] That is, the attenuation constant setting unit 13 uses a first attenuation constant Am0 that is set to be large when the current value Iin is small and to be small when the current value Iin is large, until the instantaneous current value (first current value) Iina, which will be described later, becomes smaller than the pre-measurement current value (second current value) Iinb as a result of comparison by the interruption current comparison processing unit 16. After the instantaneous current value (first current value) Iina becomes smaller than the pre-measurement current value (second current value) Iinb, the attenuation constant setting unit 13 uses a second attenuation constant Am1 that is set to be small until the gate-source voltage Vgs reaches a threshold voltage and to be large after the gate-source voltage Vgs reaches the threshold voltage.

[0034] The gate voltage setting unit 14 sets the gate-source voltage Vgs using the attenuation constant set by the attenuation constant setting unit 13 .

[0035] In this embodiment, the gate voltage setting unit 14 sets the gate-source voltage Vgs using the attenuation constant as a variable.

[0036] Specifically, the gate voltage setting unit 14 sets the output value of the gate-source voltage Vgs(Am0) with the first attenuation constant Am0 set by the attenuation constant setting unit 13 as a variable, or the gate-source voltage Vgs(Am1) with the second attenuation constant Am1 as a variable (details will be described later).

[0037] The gate voltage setting unit 14 outputs the output value of the set gate-source voltage Vgs (Am0) or gate-source voltage Vgs (Am1) to the semiconductor switch driver circuit 5 (details will be described later).

[0038] When the driving of the semiconductor switch 2 is completed at the gate-source voltage Vgs (Am0) set by the gate voltage setting unit 14, the second current value storage processing unit 15 stores the instantaneous current value Iina and a pre-measurement current value Iinb, which is the current value before measuring the instantaneous current value Iina, in a storage unit (not shown). The instantaneous current value Iina is the current value Iin at the moment the semiconductor switch 2 is driven, and the pre-measurement current value Iinb is the current value Iin before measuring the instantaneous current value Iina.

[0039] The interruption current comparison processing unit 16 compares the instantaneous current value (first current value) Iina stored by the second current value storage processing unit with the pre-measurement current value (second current value) Iinb, and determines whether the instantaneous current value Iina has become smaller than the pre-measurement current value Iinb.

[0040] In other words, the cutoff current comparison processing unit 16 compares the instantaneous current value (first current value) Iina, which is the current value flowing through the semiconductor switch 2 and is the value at the moment when the gate-source voltage Vgs (Am0) set by the gate voltage setting unit 14 is applied from the semiconductor switch driver circuit 5 to the semiconductor switch 2, with the pre-measurement current value Iinb before application.

[0041] The voltage value storage processor 17 stores the gate-source voltage Vgs(Am0) when the overcurrent starts to decrease in a storage unit (not shown) as a set voltage value Vgs_set, which is a variable of the second attenuation constant Am1. After the gate-source voltage Vgs(Am1) using the second attenuation constant Am1 as a variable has been set once, the voltage value storage processor 17 stores the gate-source voltage Vgs(Am1) in a storage unit (not shown) as the set voltage value Vgs_set.

[0042] When driving of the semiconductor switch 2 is completed at the gate-source voltage Vgs(Am1) set by the gate voltage setting unit 14, the voltage comparison processing unit 18 determines whether the gate-source voltage Vgs(Am1) output to the semiconductor switch driver circuit 5 is Vgs_min, which is the minimum value of the gate-source voltage.

[0043] (Operation of control device 1) Next, an example of the operation of the control device 1 of this embodiment will be described in detail with reference to Fig. 2 to Fig. 6. Fig. 2 is a flowchart showing an example of the operation of the control unit 10 of the control device 1. Fig. 3 is an example of a graph of an attenuation constant setting function used by the attenuation constant setting unit 13 of the control unit 10 to set the attenuation constant depending on the current flow. Fig. 4 is an example of a graph of an attenuation constant setting function used by the attenuation constant setting unit 13 of the control unit 10 to set the attenuation constant depending on the gate-source voltage.

[0044] Once the semiconductor switch 2 is in a conductive state, the current sensor 3 and the current measurement unit 4 of the control device 1 constantly monitor the current (energizing current) flowing through the semiconductor switch 2. That is, the current sensor 3 detects the current flowing through the semiconductor switch 2, and the detection result is input to the current measurement unit 4. The current measurement unit 4 measures the current value Iin of the energizing current flowing through the semiconductor switch 2 and outputs it to the control unit 10 (see FIG. 1).

[0045] As shown in FIG. 2, when the power supply enters a conducting state, the control unit 10 stores the current value Iin of the conducting current in a storage unit (not shown) (S1: first current value storage step). The overcurrent determination unit 11 determines whether or not there is an overcurrent based on the current value Iin stored in S1 (S2: overcurrent detection step). If it is determined in S2 that there is no overcurrent (NO in S2), the process returns to S1. If no short circuit or the like has occurred, S1 and S2 are repeated. S1 and S2 correspond to a cutoff necessity determination step that determines whether or not there is a need to cut off the overcurrent / short-circuit current.

[0046] On the other hand, if a short circuit or the like occurs and it is determined in S2 that there is an overcurrent (YES in S2), the process proceeds to S3, where the control unit 10 executes an overcurrent / short-circuit current interruption. In S3, the first current value storage processing unit 12 stores the current value Iin of the energized current as a set current value Iin_set in a storage unit (not shown) (S3: second current value storage step).

[0047] Next, the attenuation constant setting unit 13 sets the first attenuation constant Am0(Iin_set) according to the set current value Iin_set using a function that uses the set current value Iin_set as a variable (S4: first attenuation constant setting step).

[0048] The (Iin_set) in the first attenuation constant Am0(Iin_set) indicates that the first attenuation constant Am0 is a function with the set current value Iin_set as a variable. Therefore, the first attenuation constant Am0(Iin_set) may be simply referred to as the first attenuation constant Am0. The first attenuation constant Am0 is set between the minimum value, the first attenuation constant Am0_min, and the maximum value, the first attenuation constant Am0_max.

[0049] In this embodiment, as shown in Fig. 3, the first attenuation constant Am0_max is set to a maximum value when the set current value Iin_set is 0, and as the set current value Iin_set increases, it approaches a minimum value Am0_min at a constant gradient. In this embodiment, the first attenuation constant Am0_min is set to "1." In other words, the first attenuation constant Am0 is set to approach a minimum value from a maximum value as the current value Iin increases.

[0050] Returning to the flowchart of FIG. 2, once the first attenuation constant Am0 is set in S4, the gate voltage setting unit 14 sets the output value of the gate-source voltage Vgs(Am0) using the first attenuation constant Am0 as a variable (S5: first gate voltage setting step).

[0051] In the gate-source voltage Vgs(Am0), (Am0) indicates that the gate-source voltage Vgs is a function with the first attenuation constant Am0 as a variable. Therefore, the gate-source voltage Vgs(Am0) is sometimes simply referred to as the gate-source voltage Vgs.

[0052] The output value of the gate-source voltage Vgs(Am0) set in S5 is output to the semiconductor switch driver circuit 5 of the control device 1 (see FIG. 1). As a result, the semiconductor switch driver circuit 5 drives the semiconductor switch 2 with the set gate-source voltage Vgs(Am0), making it difficult for a current (overcurrent) to flow through the semiconductor switch 2.

[0053] When S5 is completed, the second current value storage processing unit 15 stores the instantaneous current value Iina and the pre-measurement current value Iinb before measuring the instantaneous current value Iina in a storage unit (not shown) (S6: third current value storage step).

[0054] Next, the breaking current comparison processing unit 16 compares the instantaneous current value Iina stored by the second current value storage processing unit 15 in S6 with the pre-measurement current value Iinb, and determines whether Iinb > Iina (S7: current value comparison step). If it is determined in S7 that Iinb > Iina is not the case (NO in S7), the process returns to S3. On the other hand, if it is determined in S7 that Iinb > Iina is the case (YES in S7), the process proceeds to S8.

[0055] That is, in steps S3 to S5, the gate-source voltage Vgs(Am0) is set using a first attenuation constant Am0 corresponding to the current value Iin of the conduction current flowing through the semiconductor switch 2, and the semiconductor switch driver circuit 5 drives the semiconductor switch 2. Then, in steps S6 and S7, the instantaneous current value Iina is compared with the pre-measurement current value Iinb, and if the instantaneous current value Iina becomes smaller than the pre-measurement current value Iinb, it is determined that the overcurrent (interrupt current) passing through the semiconductor switch 2 has started to decrease (reduced) (the current value Iin no longer increases). Steps S3 to S7 are repeated until S7 determines YES.

[0056] Steps S3 to S7 correspond to the first shutoff processing step in which, when it is determined that the current / short-circuit current needs to be shut off, the gate-source voltage Vgs is rapidly reduced until the current value flowing through the semiconductor switch 2 no longer increases, based on the current value Iin obtained from the detection results input from the current sensor 3.

[0057] In S8, the voltage value storage processing unit 17 stores the gate-source voltage Vgs(Am0) when the determination in S7 is YES as the set voltage value Vgs_set in a storage unit (not shown) (S8: voltage value storage step). The gate-source voltage Vgs(Am0) when the determination in S7 is YES is the transformer voltage Vgs_trans of the gate-source voltage Vgs.

[0058] Next, the attenuation constant setting unit 13 sets the second attenuation constant Am1(Vgs_set) according to the set voltage value Vgs_set using a function that uses the set voltage value Vgs_set as a variable (S9: second attenuation constant setting step).

[0059] The (Vgs_set) in the second attenuation constant Am1(Vgs_set) indicates that the second attenuation constant Am1 is a function with the set voltage value Vgs_set as a variable. Therefore, the second attenuation constant Am1(Vgs_set) may be simply referred to as the second attenuation constant Am1. The second attenuation constant Am1 is set between the minimum value Am1_min and the maximum value Am1_max. In this embodiment, Am1_min is "1."

[0060] 4, the set voltage value Vgs_set is set to "1" at the minimum value Am1_min from the transformer voltage Vgs_trans to the threshold voltage Vgs_th. Between the threshold voltage Vgs_th and Vgs_min, which is the minimum value of the gate-source voltage, the set voltage value Vgs_set is set to increase at a constant slope up to Am1_max.

[0061] In other words, the second attenuation constant Am1 is set to a minimum value until the gate-source voltage Vgs reaches the threshold voltage Vgs_th, and is set to a maximum value at the minimum value of the gate-source voltage Vgs after the gate-source voltage Vgs reaches the threshold voltage Vgs_th.

[0062] Returning to the flowchart of FIG. 2, once the second attenuation constant Am1 is set in S9, the gate voltage setting unit 14 sets the output value of the gate-source voltage Vgs(Am1) with the second attenuation constant Am1 as a variable (S10: second gate voltage setting step).

[0063] In the gate-source voltage Vgs(Am1), (Am1) indicates that the gate-source voltage Vgs is a function with the second attenuation constant Am1 as a variable. Therefore, the gate-source voltage Vgs(Am1) is sometimes simply referred to as the gate-source voltage Vgs.

[0064] The output value of the gate-source voltage Vgs(Am1) set in S10 is output to the semiconductor switch driver circuit 5 of the control device 1 (see FIG. 1). As a result, the semiconductor switch driver circuit 5 drives the semiconductor switch 2 with the set gate-source voltage Vgs(Am1), thereby reducing the current (overcurrent) flowing through the semiconductor switch 2.

[0065] When S10 is completed, the voltage comparison processing unit 18 compares the gate-source voltage Vgs(Am1) set in S10 with Vgs_min which is the minimum value of the gate-source voltage, and determines whether Vgs(Am1) < Vgs_min (S11: voltage value comparison step). In S11, if it is determined that Vgs(Am1) < Vgs_min is not true (NO in S11), the process returns to S8. On the other hand, in S11, if it is determined that Vgs(Am1) < Vgs_min is true (YES in S11), the process ends.

[0066] That is, in S8 to S11, from the transformer voltage Vgs_trans to the threshold voltage Vgs_th, with the second attenuation constant Am1 as the minimum value Am1_min, the gate-source voltage Vgs(Am1) is gradually decreased to reduce the conduction current. This suppresses the increase in the surge voltage. When the threshold voltage Vgs_th is exceeded, almost no current flows through the semiconductor switch 2. Therefore, from the threshold voltage Vgs_th to Vgs_min which is the minimum value of the gate-source voltage, the second attenuation constant Am1 is immediately increased to approach the maximum value Am1_max, and the gate-source voltage Vgs(Am1) is rapidly decreased.

[0067] S8 to S11 correspond to the second cutoff processing step of slowly decreasing the gate-source voltage Vgs after the current value flowing through the semiconductor switch 2 stops increasing.

[0068] (Waveform diagram of the gate-source voltage Vgs during overcurrent and short-circuit current cutoff) FIG. 5 is a waveform diagram of the gate-source voltage for explaining an operation example when the cutoff current is small in the control device 1. FIG. 6 is a waveform diagram of the gate-source voltage for explaining an operation example when the cutoff current is large in the control device 1.

[0069] As described above, the first attenuation constant Am0 is set to be larger as the cutoff current (overcurrent) is smaller (see FIG. 3). Therefore, as shown in FIGS. 5 and 6, the waveform of the gate-source voltage Vgs varies depending on the magnitude of the cutoff current.

[0070] When the breaking current is small, the transformer voltage Vgs_trans of the gate-source voltage Vgs at which the current value Iin of the current flowing through the semiconductor switch 2 starts to decrease (reduced) is low and is far from Vgs_max, which is the gate-source voltage during the on-period. Therefore, if the rate at which the gate-source voltage Vgs is reduced is slow, the amount of current flowing to the load 52 increases.

[0071] 5, by increasing the value of the first attenuation constant Am0, the voltage can be quickly reduced to the transformer voltage Vgs_trans, thereby reducing the amount of current flowing to the load 52.

[0072] Conversely, when the interruption current is large, the transformer voltage Vgs_trans is high and close to Vgs_max, which is the gate-source voltage during the on-period. Therefore, if the gate-source voltage Vgs is reduced too quickly, a surge voltage will occur.

[0073] As shown in Figure 6, by reducing the value of the first attenuation constant Am0, the rate at which the voltage is reduced to the transformer voltage Vgs_trans is slower than in the case of Figure 5, thereby reducing the amount of current flowing to the load 52 while also suppressing the occurrence of surge voltage.

[0074] As shown in FIGS. 5 and 6, regardless of the magnitude of the interruption current, once the gate-source voltage Vgs has been reduced to the transformer voltage Vgs_trans, it is gradually reduced so as to suppress the surge voltage.

[0075] (Description of effects) 7 and 8, if the interruption current is large, the gate-emitter voltage changes rapidly during period A, making it more likely that a surge voltage will occur. In contrast, as shown in Fig. 6, control device 1 rapidly reduces the current until just before the increase in the current flow is suppressed, and then gradually reduces the current thereafter to prevent the generation of a surge voltage, thereby effectively suppressing the generation of a surge voltage during interruption.

[0076] 7 and 8, when the breaking current is small, the rate of decrease during period A is fixed, so there is a concern that a faster decrease may increase the amount of current flowing to load 52. In contrast, as shown in FIG. 5, in control device 1, the breaking current is rapidly decreased at a rate faster than when the breaking current is large until just before the increase in the conducting current is suppressed, so the amount of current flowing to load 52 can be minimized.

[0077] 7 and 8, the rate at which the gate-emitter voltage is reduced is fixed within each period A and B, regardless of the magnitude of the interruption current, which could result in periods A and B during which the short-circuit current can increase. In contrast, the control device 1 switches the rate of reduction to a rate that can suppress the generation of surge voltage once the short-circuit current begins to decrease, thereby reducing this unnecessary increase in interruption current. Compared to the prior art, once the short-circuit current has been reduced to a point where it no longer increases, the source voltage is gradually reduced during period B, which suppresses the surge voltage, thereby reducing the unnecessary increase in interruption current.

[0078] [Software implementation example] The functions of the control device 1 (hereinafter referred to as the "device") can be realized by a program that causes a computer to function as the device, and a program that causes a computer to function as each control block of the device (particularly each part included in the control unit 10).

[0079] In this case, the device includes a computer having at least one control device (e.g., a processor) and at least one storage device (e.g., a memory) as hardware for executing the program. The control device and storage device execute the program, thereby realizing the functions described in each of the above embodiments.

[0080] The program may be non-transitory and may be recorded on one or more computer-readable recording media. The recording media may or may not be included in the device. In the latter case, the program may be supplied to the device via any wired or wireless transmission medium.

[0081] [Additional Notes] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention. [Explanation of symbols]

[0082] 1. Control device 2. Semiconductor switches 3 Current Sensor 4 Current measurement section 5. Semiconductor switch driver circuit 10 Control Unit 13 Attenuation constant setting section 14 Gate voltage setting section 50 Semiconductor Interrupter System 51 Power supply 52 Load Am0 First damping constant (damping constant) Am1 Second damping constant (damping constant) Iin current value Iina Instantaneous current value (first current value) Iinb Current value before measurement (second current value) t time Vgs Gate-source voltage (gate voltage) Vgs_th threshold voltage

Claims

1. In a semiconductor shutoff system including a semiconductor switch having one end connected to a power source and the other end connected to a load, for shutting off a current from the power source to the load, and a current sensor for detecting a current flowing from the power source to the semiconductor switch, a control device is provided that applies a gate voltage to the semiconductor switch to control it, a control unit that sets the gate voltage; a driver circuit that applies the gate voltage set by the control unit to the semiconductor switch, The control device, when interrupting an overcurrent or short-circuit current, based on the current value obtained from the detection result input from the current sensor, quickly reduces the gate voltage until the value of the current flowing through the semiconductor switch no longer increases, and then slowly reduces the gate voltage after the value of the current flowing through the semiconductor switch no longer increases.

2. The control unit an attenuation constant setting unit that sets an attenuation constant when the gate voltage is reduced; a gate voltage setting unit that sets the gate voltage using the attenuation constant set by the attenuation constant setting unit; a breaking current comparison processing unit that compares a first current value at the moment when the gate voltage set by the gate voltage setting unit is applied from the driver circuit to the semiconductor switch with a second current value before the application, the first current value being a current value flowing through the semiconductor switch; The attenuation constant setting unit As a result of the comparison by the breaking current comparison processing unit, until the first current value becomes smaller than the second current value, a first attenuation constant is used that is set to be large when the current value is small and to be small when the current value is large, 2. The control device according to claim 1, wherein a second attenuation constant is set to be small after the first current value becomes smaller than the second current value until the gate voltage reaches a threshold voltage, and to be large after the gate voltage reaches the threshold voltage.

3. the first attenuation constant is set so as to approach a minimum value from a maximum value as the current value increases, 3. The control device according to claim 2, wherein the second attenuation constant is set to a minimum value until the gate voltage reaches a threshold voltage, and to a maximum value at the minimum value of the gate voltage after the gate voltage reaches the threshold voltage.

4. a semiconductor switch having one end connected to a power source and the other end connected to a load, the semiconductor switch cutting off current from the power source to the load; a current sensor that detects a current flowing from the power supply to the semiconductor switch; A semiconductor shutdown system comprising: a control device according to any one of claims 1 to 3.

5. In a semiconductor shutoff system including a semiconductor switch having one end connected to a power supply and the other end connected to a load, for shutting off a current from the power supply to the load, and a current sensor for detecting a current flowing from the power supply to the semiconductor switch, a control method for controlling the semiconductor switch by applying a gate voltage to the semiconductor switch, comprising: a disconnection necessity determination step for determining whether or not an overcurrent / short circuit current needs to be disconnected; a first cutoff processing step of rapidly reducing the gate voltage until the value of the current flowing through the semiconductor switch no longer increases, based on the current value obtained from the detection result input from the current sensor, when it is determined that the overcurrent or short-circuit current needs to be cut off; a second cutoff process step of slowly reducing the gate voltage after the current value flowing through the semiconductor switch stops increasing.

6. A control program for causing a computer to function as the control device according to any one of claims 1 to 3, the control program causing the computer to function as the control unit.

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