Semiconductor switching device

Abstract

The invention provides a semiconductor switching device which reduces resources related to accurate estimation of wire temperature and performs square accumulation of load current and wire temperature estimation at low cost and high precision. A semiconductor switching device (200) according to one or more embodiments includes: switching units (206, 201, 202) that are connected between a power source (300) connected from the outside of the semiconductor switching device (200) and a load (400) via an electric wire, and that turn on / off the supply of power to the load; load current detection units (203, 204) that detect a load current flowing through the switching units (206, 201, 202); and a square calculation unit (205) that outputs a square value of the load current value detected by the current detection units (203, 204). The switching unit (206) receives a control command from the outside, and turns on / off the supply of power to the load in accordance with the control command.

Description

Technical Field

[0001] The present disclosure relates to a semiconductor switch device, and more particularly to a semiconductor switch device that protects electric wires, loads, a semiconductor switch body, etc. from excessive heat caused by overcurrent. Background Art

[0002] The number of electronic devices installed in vehicles and the like has been increasing in recent years. Electronic devices installed in vehicles and the like are often electrically connected to the battery via wiring such as wiring harnesses. Since the heating of the wiring can cause serious accidents such as smoke and fire, the temperature management of the wiring is very important. In electronic devices, on / off control is sometimes performed by a semiconductor switch with a current detection circuit. For the load current detected by the current detection circuit, the load current value is discretely detected by an MCU (MicroController Unit) or the like that is separately set for control, and the detected current value is multiplied and added according to a pre-set heating model of the wire, thereby protecting the wire from overheating.

[0003] Japanese Patent No. 5097229 (Patent Document 1) discloses an overheat protection device that can accurately determine the temperature of an electric wire without performing a square operation process using a microcomputer or the like. The disclosure includes the following: when the voltage exceeds a triangular wave signal, the overheat protection device outputs a sense current to a thermal equivalent circuit, and accumulates a charge corresponding to the current value and the time the current flows in the capacitor of the thermal equivalent circuit; further, when the voltage becomes n times, the time the voltage exceeds the triangular wave signal becomes n times, so the charge accumulated in the capacitor becomes proportional to the square of the sense current; therefore, the voltage generated in the thermal equivalent circuit becomes proportional to the square of the load current, which can be regarded as the estimated temperature of the load / electric wire circuit; therefore, the temperature of the load / electric wire circuit can be estimated without using a microcomputer or the like for square operation.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent No. 5097229 Summary of the invention

[0007] Problems to be solved by the invention

[0008] As the number of electronic devices mounted on vehicles and the like increases, the load on the MCU that performs various controls on the electronic devices mounted on vehicles and the like increases. In particular, when the MCU performs overheat protection control of all the wires electrically connected to the electronic devices, the computing load increases explosively. In particular, against the background of the increase in electronic devices mounted on vehicles and the like in recent years, 1) when the number of outputs of the MCU semiconductor switch increases, the computing load increases, and 2) the resources used by the MCU for analog-to-digital conversion (A / D conversion) of the load current increase. As a result, the electronic equipment increases and the cost increases. In addition, since the load current is detected discretely, it is impossible to fully detect the short-term increase and surge-like changes in the load current, and the error becomes larger.

[0009] Furthermore, in the technique disclosed in Patent Document 1, the amount of heat generated in the load is estimated, and the overheat state of the load and the electric wire is monitored using the estimated amount of heat. In this technique, a large amount of circuits are required for overheat determination.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a semiconductor switch device that reduces resources associated with accurate estimation of wire temperature and performs square integration of load current and estimation of wire temperature at low cost and with high accuracy.

[0011] Means for solving problems

[0012] The semiconductor switch device of one or more embodiments comprises: a switch unit, which is connected between a power source connected from the outside of the semiconductor switch device and a load via an electric wire, and turns on / off the power supply to the load; a load current detection unit, which detects the load current flowing through the switch unit; and a square operation unit, which outputs the square value of the load current detected by the current detection unit. The switch unit receives a control instruction from the outside, and turns on / off the power supply to the load according to the control instruction.

[0013] Effects of the Invention

[0014] According to this configuration, it is possible to provide a semiconductor switch device that reduces resources related to accurate estimation of the electric wire temperature and performs square integration of the load current and estimation of the electric wire temperature at low cost and with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A is a cross-sectional view showing a temperature model of an electric wire used in a semiconductor switch device according to one or more embodiments, Figure 1B It is shown that, for example Figure 1A A diagram of an equivalent circuit 150 of a temperature model of an electrical wire is shown.

[0016] Figure 2It is a graph showing the relationship between the electric wire current and the electric wire temperature.

[0017] Figure 3 is a diagram showing a semiconductor switching device 200 and peripheral circuits according to one or more embodiments.

[0018] Figure 4 is a diagram illustrating squaring circuit 205 in accordance with one or more embodiments.

[0019] Figure 5 2 is a diagram showing a semiconductor switch device 220 and peripheral circuits according to one or more embodiments.

[0020] Figure 6 2 is a diagram showing a semiconductor switch device 210 and peripheral circuits according to one or more embodiments.

[0021] Figure 7 2 is a diagram showing an example of a signal output by the charge and discharge circuit 217 .

[0022] Figure 8 2 is a diagram showing a semiconductor switch device 250 and peripheral circuits according to one or more embodiments.

[0023] Fig. 9 2 is a diagram showing a semiconductor switch device 230 and peripheral circuits according to one or more embodiments. DETAILED DESCRIPTION

[0024] A semiconductor switch device according to one or more embodiments will be described with reference to the drawings.

[0025] Figure 1A 1 is a cross-sectional view showing a temperature model of an electric wire used in a semiconductor switch device of one or more embodiments. In this figure, for the sake of convenience, a cross-sectional view of an electric wire is shown. The electric wire 100 includes: a conductor 101 that supplies current and transmits electrical signals; and an insulator 102 that covers the conductor 101 in a manner that insulates the conductor 101 from the outside. When current flows through the electric wire 100, a resistance value R of the conductor 101 is generated. W The loss is obtained by multiplying the square of the current value Iw flowing through the conductor 101. Most of this loss becomes heat energy, and the wire 100 generates heat. A part of the generated loss is first transferred to the insulator 102 after a predetermined delay (Rthwc), and then dissipated into the space as heat (Rthca). Here, the wire is a wire that transmits electricity, and refers to a linear component that electrically connects electronic components to electronic components. In addition to general wires, it also includes wiring in a printed circuit board.

[0026] Figure 1B It is shown that, for example Figure 1A The equivalent circuit 150 of the temperature model of the electric wire shown in the figure. The equivalent circuit 150 of the temperature model of the electric wire mentioned above has a thermal resistance Rthwc of the insulator 102 and a thermal resistance Rthca radiated from the insulator 102 to the space between the current source Iw as the loss generating source and the voltage source Vat which becomes the ambient temperature. The equivalent circuit shown in the figure has: a current source 152, which generates a current Iw; a circuit 154, which receives the current Iw and outputs Rw×Iw^2; a thermal resistance Rthwc and a thermal resistance Rthca, which are electrically connected in series with the circuit 154; a thermal capacitance Cthc, which is connected in parallel with the thermal resistance Rthwc and the thermal resistance Rthca; and a voltage source Vat. Figure 1B In the calculation, the equivalent circuit representing the temperature model of the electric wire is calculated using the conductor 101. In many cases, there is a time difference between the radiation of heat from the insulator 102 to space and the generation of heat due to loss. Therefore, the heat capacity Cthc of the electric wire 100 is included in the equivalent circuit of the temperature model. By including the heat capacity Cthc, it is possible to provide an equivalent circuit of the temperature model with higher accuracy.

[0027] Since the loss of the wire is proportional to the square of the current flowing through the wire, when the current becomes larger, the heat sometimes increases significantly. In this case, when the temperature of the conductor rises and reaches the smoking temperature of the insulator, it is possible to cause a fault such as smoking. In order to protect the wire from excessive heat, it is necessary to manage and protect the wire temperature as needed by estimating the wire temperature using the temperature model of the wire. On the other hand, in order to accurately estimate the wire temperature, it is necessary to implement the accuracy of various parameters of the model and temperature estimation calculations in real time, but when the interval of load current detection is shortened, the load of calculation processing of the MCU (MicroController Unit: microcontroller unit) etc. increases, so the calculation load becomes more, so it is necessary to reduce the calculation load of this part.

[0028] Figure 2: is a diagram showing the relationship between the wire current and the wire temperature. Generally speaking, when the state where no current flows through the wire continues for a certain period of time, the wire temperature reaches the ambient temperature Ta. The semiconductor switch device is turned on, and the output voltage rises to the input voltage level (t1). Then, the current is supplied to the load, and an inrush current flows in the load current, and the wire temperature rises rapidly. When the load current decreases and is maintained at the nominal current (t2), the wire loss decreases, so the wire temperature gradually decreases and becomes a temperature in which the temperature rise due to self-heating is added to the ambient temperature Ta. Next, when an overload current flows through the wire (t3), the wire temperature rises again. When the wire temperature exceeds a certain value due to the rise in ambient temperature and overload (t4), the temperature rises above the limit of the usable temperature of the insulator 102 covering the conductor 101, and there is a possibility of wire damage such as smoke. Therefore, at the stage before the wire temperature reaches the smoke temperature, for example, a protection temperature lower than the smoke temperature is set in advance, and when the protection temperature is reached, it is necessary to cut off the load current supplied to the load. When the load current is cut off, the load voltage drops and the wire temperature decreases.

[0029] Figure 3 1 is a diagram showing a semiconductor switch device 200 and a peripheral circuit of one or more embodiments. As shown in the figure, the semiconductor switch device 200 is electrically connected between a voltage source 300 and a load 400 provided outside the semiconductor switch device 200. The semiconductor switch device 200 includes: a load current detection circuit, which includes a buffer circuit 204 and a transistor 203, and detects a load current from the load 400; and a square operation circuit, which receives a current from the transistor 203 and outputs a square value of the received current signal. In addition, the semiconductor switch device 200 has a switch unit, which includes: a control circuit 206, which receives a control instruction from an MCU (Micro Controller Unit: microcontroller unit) 500; and a transistor 201 and a transistor 202, and the control circuit 206 controls the transistor 201 and the transistor 202 to be turned on / off. The voltage source 300 supplies a predetermined voltage to the semiconductor switch device 200. The voltage source 300 includes, for example, a device capable of supplying voltage, such as a battery mounted on a vehicle. The load 400 is, for example, mounted on a vehicle and includes various electronic devices supplied with power from the battery via a wire. When a voltage is supplied from the voltage source 300, a load current is supplied to the load 400 via the semiconductor switch device 200. When the load current is supplied, the load 400 performs various operations.

[0030] As shown in the figure, the gates of transistor 201 and transistor 202 are electrically connected to control circuit 206. The drains of transistor 201 and transistor 202 are electrically connected to voltage source 300. The source of transistor 201 is electrically connected to load 400 and buffer circuit 204, and the source of transistor 202 is electrically connected to buffer circuit 204. The gate of transistor 203 is electrically connected to buffer circuit 204, the source of transistor 203 is electrically connected to the source of transistor 202, and the drain of transistor 203 is electrically connected to square operation circuit 205. Resistor 601 is electrically connected to square operation circuit 205 and the drain of transistor 203, and resistor 602 is electrically connected to square operation circuit 205 and MCU 500. Semiconductor switch device 200 can also be sealed in a resin package.

[0031] Next, the operation of the semiconductor switch device 200 is described. First, the control circuit 206 receives a control instruction from the MCU 500 and performs various switch controls. The control circuit 206 outputs a drive voltage to the gates of the transistor 201 and the transistor 202 according to the control instruction. When the gates of the transistors 201 and 202 receive the drive voltage, they become conductive. Thus, the voltage output by the voltage source 300 is supplied to the load 400. Thus, a load current is supplied to the load 400. When the load current is supplied, the load 400 performs various operations.

[0032] The buffer circuit 204 receives the outputs of the transistor 201 and the transistor 202. The buffer circuit 204 outputs a voltage corresponding to the difference between the voltages output by the transistor 201 and the transistor 202 to the transistor 203. The transistor 203 supplies a current to the square operation circuit 205 according to the voltage output by the buffer circuit 204. The square operation circuit 205 performs a square operation according to the supplied current signal. Here, the square operation circuit 205 may also supply a voltage signal proportional to the current level output by the transistor 203. In this case, the resistor 601 is connected from the outside of the semiconductor switch device 200. The square operation circuit 205 may also receive the voltage value output by the transistor 203 and perform a square operation according to the voltage signal. The resistor 602 may also be provided inside the semiconductor switch device 200. The MCU 500 performs analog-to-digital conversion (A / D conversion) on the current value output by the square operation circuit 205, and calculates the loss of the wire electrically connecting the voltage source 300 and the load 400 according to the digitized current value. MCU 500 estimates the temperature of the wire based on the calculated loss of the wire, determines whether the wire has reached the protection temperature based on the estimated temperature, and outputs the current cutoff voltage to the control circuit 206 when it is determined that the wire has reached the protection temperature. Transistor 201 and transistor 202 are turned off according to the current cutoff voltage. Thus, the current supply to load 400 is cut off. Here, MCU 500 is sometimes unable to read the current value. In this case, resistor 602 is connected from the outside of semiconductor switch device 200. MCU 500 can also receive the voltage value output by semiconductor switch device 200, perform A / D conversion on the voltage value, and calculate the loss of the wire that electrically connects voltage source 300 and load 400 based on the digitized current value. Resistor 602 can also be set inside semiconductor switch device 200.

[0033] As mentioned above, Figure 3 The semiconductor switch device 200 shown can integrate the square of the load current required for calculating the loss of the wire electrically connecting the load 400 with a simple circuit configuration. This can reduce the load on the MCU 500 and integrate the square of the load current at low cost and with high accuracy.

[0034] Figure 4 is a diagram illustrating a square operation circuit according to one or more embodiments. Figure 4In the embodiment, the base and collector of the transistor Q20 are electrically connected to the power supply VREG, and the emitter of the transistor Q20 is electrically connected to the input terminal Iin1 and the base of the transistor Q21. The collector of the transistor Q21 is electrically connected to the power supply VREG, and the emitter is electrically connected to the input terminal Iin2 and the base of the transistor Q22. The emitter of the transistor Q22 is electrically connected to the emitter of the transistor Q23 and one end of the current source I20. The collector of the transistor Q22 is electrically connected to the base of the transistor Q24 and the emitter of the transistor Q25.

[0035] The base of transistor Q23 is electrically connected to current source Ik and the emitter of transistor Q24, and the collector of transistor Q23 is electrically connected to output terminal Iout. The collector of transistor Q24 is electrically connected to power supply VREG, and the base and collector of transistor Q25 are electrically connected to power supply VREG. Transistors Q20, Q21, Q22, Q23, Q24, and Q25 include NPN transistors, but may be formed of other transistors to form a multiplication and division circuit.

[0036] Next, explain Figure 4 The operation of the square operation circuit shown in the figure. First, input current Iin1 to input terminal Iin1. Input current Iin2 to input terminal Iin2. Current source Ik outputs current Ik. In this case, (Iin1×Iin2) / Ik is output to output terminal Iout. If Iin1 and Iin2 are Iin, the current Ik output by current source Ik is set to a fixed value, for example, Ik=1 / K, then Iout=K·Iin 2 , it is possible to output a current that is the square of the input current. However, the current output from the output terminal Iout is limited to be less than the bias current of the current source I20. The entire contents of U.S. Patent Application No. 12 / 428,587, especially the description of the square operation circuit, are incorporated into this specification by reference.

[0037] Figure 5 1 is a diagram showing a semiconductor switch device 220 and a peripheral circuit according to one or more embodiments. As shown in the figure, the semiconductor switch device 220 is electrically connected between a voltage source 320 provided outside the semiconductor switch device 220 and a load 420. The semiconductor switch device 220 includes: a load current detection circuit supplied to the load 420, which includes a buffer circuit 224 and a transistor 223; an analog-to-digital converter (ADC) 227, which performs analog-to-digital conversion (A / D conversion) on the load current detected by the load current detection circuit; and a square operation circuit 225, which receives the signal converted by the ADC 227 and outputs the square value of the squared load current.

[0038] In addition, the semiconductor switch device 220 has a switch portion, which includes: a control circuit 226 that receives a control instruction from an MCU (Micro Controller Unit) 520; and a transistor 221 and a transistor 222, and the control circuit 226 controls the transistor 221 and the transistor 222 to be turned on / off. The voltage source 320 supplies a specified voltage to the semiconductor switch device 220. The voltage source 320 includes, for example, a device capable of supplying voltage, such as a battery mounted on a vehicle. The load 420 is mounted on a vehicle, for example, and includes various electronic devices that are supplied with power from the battery via wires. When a voltage is supplied from the voltage source 320, a load current is supplied to the load 420 via the semiconductor switch device 220. When the load current is supplied, the load 420 performs various operations. The resistor 621 is electrically connected to the ADC 227 and the drain of the transistor 223.

[0039] Next, the operation of the semiconductor switch device 220 is described. First, the control circuit 226 receives a control instruction from the MCU 520 and performs various switch controls. The control circuit 226 outputs a drive voltage to the gates of the transistor 221 and the transistor 222 according to the control instruction. When the gates of the transistors 221 and 222 receive the drive voltage, they become conductive. Thus, the voltage output by the voltage source 320 is supplied to the load 420. Thus, a load current is supplied to the load 420. When the load current is supplied, the load 420 performs various operations.

[0040] The buffer circuit 224 receives the outputs of the transistor 221 and the transistor 222. The buffer circuit 224 outputs a voltage corresponding to the difference between the voltages output by the transistor 221 and the transistor 222 to the transistor 223. The transistor 223 supplies a current to the ADC 227 according to the voltage output by the buffer circuit 224. The ADC 227 performs analog-to-digital conversion (A / D conversion) according to the supplied current signal, and outputs a digital signal corresponding to the supplied current signal. Here, a current proportional to the load current of the transistor 221 is supplied to the resistor 621. Alternatively, the ADC 227 reads the current signal converted into a voltage by the resistor 621. The square operation circuit 225 receives the digital signal output from the ADC 227, and performs a square operation according to the digital signal. The square operation circuit 225 outputs the result of the square operation to the MCU 520 as a digital signal. The MCU 520 receives the digital signal output by the square operation circuit 225, and calculates the loss of the wire that electrically connects the voltage source 320 and the load 420 according to the digital signal. The MCU 520 estimates the temperature of the electric wire based on the calculated loss of the electric wire, determines whether the electric wire has reached the protection temperature based on the estimated temperature, and outputs a current cut-off instruction to the control circuit 226 when it is determined that the electric wire has reached the protection temperature. The control circuit 226 turns off the transistor 221 and the transistor 222 based on the current cut-off instruction, thereby cutting off the current supply to the load 420.

[0041] As mentioned above, in Figure 5 In the semiconductor switch device 220 shown, the MCU 520 receives the result of the digitized square operation, so the MCU 520 does not need to perform A / D conversion. As a result, the square accumulation of the load current required for calculating the loss of the wire electrically connected to the load 420 can be performed with a simple circuit structure, which can reduce the load of the MCU 520 and perform the square accumulation of the load current at a low cost and with high accuracy.

[0042] Figure 61 is a diagram showing a semiconductor switch device 210 and a peripheral circuit according to one or more embodiments. As shown in the figure, the semiconductor switch device 210 is electrically connected between a voltage source 310 and a load 410 provided outside the semiconductor switch device 210. The semiconductor switch device 210 includes: a load current detection circuit supplied to the load 410, which includes a buffer circuit 214 and a transistor 213; and a square operation circuit 215, which outputs the square value of the detected load current. In addition, the semiconductor switch device 210 has a switch unit, which includes: a control circuit 216, which receives a control instruction from an MCU (Micro Controller Unit: microcontroller unit) 510; and a transistor 211 and a transistor 212, and the control circuit 216 performs on / off control on the transistor 211 and the transistor 212. The voltage source 310 supplies a predetermined voltage to the semiconductor switch device 210. The voltage source 310 includes, for example, a device capable of supplying voltage, such as a battery mounted on a vehicle. The load 410 is, for example, mounted on a vehicle and includes various electronic devices supplied with power from the battery via a wire. When a voltage is supplied from the voltage source 310, a load current is supplied to the load 410 via the semiconductor switch device 210. When the load current is supplied, the load 410 performs various operations.

[0043] As shown in the figure, Figure 6 The semiconductor switch device 210 shown includes a charge and discharge circuit 217, which is electrically connected to the square operation circuit 215 and the MCU 510. The charge and discharge circuit 217 is electrically connected to a capacitor 611 connected from the outside of the semiconductor switch device 210, and charges and discharges the capacitor 611 within a predetermined voltage range.

[0044] Next, the operation of the semiconductor switch device 210 is described. First, the control circuit 216 receives a control instruction from the MCU 510 and performs various switch controls. The control circuit 216 outputs a drive voltage to the gates of the transistor 211 and the transistor 212 according to the control instruction. When the gates of the transistors 211 and 212 receive the drive voltage, they become conductive. Thus, the voltage output by the voltage source 310 is supplied to the load 410. Thus, a load current is supplied to the load 410. When the load current is supplied, the load 410 performs various operations.

[0045] The buffer circuit 214 receives the outputs of the transistor 211 and the transistor 212. The buffer circuit 214 outputs a voltage corresponding to the difference between the voltages output by the transistor 211 and the transistor 212 to the transistor 213. The transistor 213 supplies a current to the square operation circuit 215 according to the voltage output by the buffer circuit 214. The square operation circuit 215 performs a square operation according to the supplied current signal. Next, the charge and discharge circuit 217 converts the current signal output by the square operation circuit 215 into a pulse signal by charging and discharging the capacitor 611. The MCU 510 receives the pulse signal, thereby making it easier to receive the signal from the semiconductor switch device 200. Here, the cycle of the pulse signal can be changed by adjusting the capacitance of the capacitor 611. Here, the capacitor 611 can also correct the square operation of the wire loss. In many cases, there is a time difference between the radiation of heat from the insulator of the wire model to the space and the generation of heat due to the loss. Therefore, the heat capacity Cthc of the wire of the equivalent circuit of the temperature model can be considered by charging and discharging the capacitor 611. By considering the heat capacity Cthc, the load of the MCU 510 can be reduced, and the load current can be calculated with higher accuracy. In addition, the charge and discharge circuit 217 can also perform A / D conversion on the corrected square operation result after correction considering the heat capacity Cthc and output it to the MCU 510. The MCU 510 calculates the loss of the wire that electrically connects the voltage source 310 and the load 410 based on the current value digitized by the charge and discharge circuit 217. The MCU 510 estimates the temperature of the wire based on the calculated loss of the wire, determines whether the wire reaches the protection temperature based on the estimated temperature, and outputs the current cut-off instruction to the control circuit 216 when it is determined that the wire reaches the protection temperature. The control circuit 216 turns the transistor 211 and the transistor 212 into the off state according to the current cut-off instruction. Thus, the current supply to the load 410 is cut off. Here, the capacitor 611 can also be set externally in a manner that can be replaced by the semiconductor switch device 210. By being able to replace the capacitor 611, it is possible to cope with voltage sources 310 with different output voltages and loads 410 with different thermal characteristics.

[0046] As mentioned above, Figure 6 The semiconductor switch device 210 shown can perform square integration related to the load current required for calculating the loss of the wire electrically connected to the load 410 with a simple circuit configuration. Here, the charge and discharge circuit 217 generates a pulse signal by using the capacitor 611, and the MCU 510 can simply receive the signal from the semiconductor switch device 210. Thus, the MCU 510 can receive the signal from the semiconductor switch device 210 with a simple circuit configuration. In addition, the charge and discharge circuit 217 can perform square integration of the time difference in which heat is radiated from the insulator of the wire thermal model to the space.

[0047] Figure 6 The embodiment of the semiconductor switching device shown is similar to Figure 3 Compared with the embodiment of the semiconductor switch device shown in FIG. 1 , the square operation result of the load current is output as a current and the capacitor is charged and discharged so that the multiplication and accumulation operation of the power line loss is taken into the switching element side. Here, the charge and discharge circuit 217 can also output a pulse signal synchronized with the switching of the charge and discharge of the capacitor 611 to the MCU 510.

[0048] Figure 7 2 is a diagram showing an example of a signal output by the charge and discharge circuit 217. The MCU 510 receives the square operation result shown in the figure from the semiconductor switch device 210. Figure 6 As shown, the charge and discharge circuit 217 outputs a pulse signal of the square operation result synchronized with the switching of the charge and discharge of the capacitor 603. By outputting the pulse signal to the MCU 510, a low-frequency pulse signal is output when the wire current is small, and a high-frequency pulse signal is output when the wire current becomes large. With this configuration, since the MCU 510 can continuously monitor the load current as an analog value, it is possible to obtain information including the influence of the short-pulse surge current. Therefore, the calculation load of the MCU 510 can be suppressed, and accurate wire temperature estimation can be performed.

[0049] Figure 8 1 is a diagram showing a semiconductor switch device 250 and a peripheral circuit according to one or more embodiments. As shown in the figure, the semiconductor switch device 250 is electrically connected between a voltage source 340 and a load 440 provided outside the semiconductor switch device 250. The semiconductor switch device 250 includes: a load current detection circuit including a buffer circuit 254 and a transistor 253, which detects a load current from the load 440; and a square operation circuit 255, which outputs a square value of a received current signal. In addition, the semiconductor switch device 250 has a switch portion, which includes: a control circuit 256, which receives a control instruction from an MCU (MicroController Unit) 540; and a transistor 251 and a transistor 252, and the control circuit 256 performs on / off control on the transistor 251 and the transistor 252. The voltage source 340 supplies a predetermined voltage to the semiconductor switch device 250. The voltage source 340 includes, for example, a device capable of supplying voltage, such as a battery mounted on a vehicle. The load 440 is, for example, mounted on a vehicle and includes various electronic devices supplied with power from the battery via a wire. When a voltage is supplied from the voltage source 340, a load current is supplied to the load 440 via the semiconductor switch device 250. When the load current is supplied, the load 440 performs various operations.

[0050] As shown in the figure, Figure 8 The semiconductor switch device 250 shown in the figure has a buffer circuit 257, a transistor 258, and a comparator circuit 259. In addition, a capacitor 641 and a resistor 642 are electrically connected to the buffer circuit 257, the square circuit 255, and the comparator circuit 259. The capacitor 641 and the resistor 642 may be provided outside the semiconductor switch device 250, or may be provided inside the semiconductor switch device 250.

[0051] Next, the operation of the semiconductor switch device 250 is described. First, the control circuit 256 receives a control instruction from the MCU 540 and performs various switch controls. The control circuit 256 outputs a drive voltage to the gates of the transistor 251 and the transistor 252 according to the control instruction. When the gates of the transistors 251 and 252 receive the drive voltage, they become conductive. Thus, the voltage output by the voltage source 340 is supplied to the load 440. Thus, a load current is supplied to the load 440. When the load current is supplied, the load 440 performs various operations.

[0052] The buffer circuit 254 receives the outputs of the transistor 251 and the transistor 252. The buffer circuit 254 outputs a voltage corresponding to the difference between the voltages outputted by the transistor 251 and the transistor 252 to the transistor 253. The transistor 253 supplies a current signal to the square operation circuit 255 according to the voltage outputted by the buffer circuit 254. The square operation circuit 255 performs a square operation according to the supplied current signal. The buffer circuit 257 receives information related to the ambient temperature from the MCU 540 and outputs a voltage corresponding thereto. The comparator circuit 259 outputs a comparison result between an estimated wire temperature signal obtained by adding a current signal of a square operation result of the capacitor 641 and the resistor 642 to the output of the buffer circuit 257 and a voltage outputted by the reference voltage source 261 to the output transistor 258. Here, when the control circuit 256 receives a voltage higher than a predetermined value from the comparator circuit 259, the control circuit 256 turns off the transistor 251 and the transistor 252. Thus, the current supply to the load 440 is cut off. When receiving a voltage higher than a predetermined value from the comparator circuit 259 , the transistor 258 notifies the MCU 540 of fault information (Fault).

[0053] exist Figure 8 In the semiconductor switch device 250 shown in FIG. Figure 3Compared with the semiconductor switch device 200 shown in the figure, a parallel circuit of a resistor 642 and a capacitor 641 reflecting the heat model of the electric wire is electrically connected between a buffer circuit 257 that receives an input of a voltage signal reflecting the ambient temperature and performs buffering and a square operation circuit 255, and a control circuit 256 is provided. When the output side voltage (estimated wire temperature) of the square operation circuit 255 becomes greater than a specified value, the control circuit 256 cuts off the transistor 251 and the transistor 252. The semiconductor switch device 250 estimates and protects the wire temperature by obtaining ambient temperature information from the MCU 540, so that the wire protection can be realized with less resources. In addition, by accurately estimating the wire temperature, the melting characteristics of the fuse used in the protection of the wire in the past can be more accurately estimated, so that the resource saving brought about by the optimization of the wire diameter and the reduction effect of the transportation cost brought about by the weight reduction can be obtained. In addition, the semiconductor switch device 250 can realize the wire temperature protection by receiving the ambient temperature information from the MCU 540. Therefore, with the increase in vehicle-mounted electronic devices in recent years, the control processing of the MCU has increased, but by using the semiconductor switch device 250 to perform the above-mentioned processing, control can be performed with a cheaper MCU.

[0054] Fig. 9 1 is a diagram showing a semiconductor switch device 230 and a peripheral circuit according to one or more embodiments. As shown in the figure, the semiconductor switch device 230 is electrically connected between a voltage source 330 and a load 430 provided outside the semiconductor switch device 230. The semiconductor switch device 230 includes: a load current detection circuit supplied to the load 430, which includes a buffer circuit 234 and a transistor 233; and a square operation circuit 235, which outputs the square value of the detected load current. In addition, the semiconductor switch device 230 has a switch unit, which includes: a control circuit 236, which receives a control instruction from an MCU (Micro Controller Unit: microcontroller unit) 530; and a transistor 231 and a transistor 232, and the control circuit 236 controls the transistor 231 and the transistor 232 to be turned on / off. The voltage source 330 includes, for example, a device capable of supplying voltage, such as a battery mounted on a vehicle. The load 430 is, for example, mounted on a vehicle and includes various electronic devices supplied with power from the battery via electric wires. When a voltage is supplied from the voltage source 330, a load current is supplied to the load 430 via the semiconductor switch device 230. When the load current is supplied, the load 430 performs various operations.

[0055] As shown in the figure, Fig. 9The semiconductor switch device 230 shown has: ADC 237, which receives current from transistor 233 and performs A / D conversion on the received current signal; a square operation circuit 235, which receives the output of ADC 237 and performs a square operation; a communication interface (I / F) 238, which communicates with MCU 530; ADC 239, which receives ambient temperature information from MCU 530, performs A / D conversion on the received ambient information and outputs an ambient temperature signal; an operation circuit 241, which receives the operation result of the square operation circuit 235 and the ambient temperature signal from ADC 239, and performs various operations; and an overheat protection circuit 243, which determines whether it is necessary to protect the wires electrically connecting the voltage source 330 and the load 430 from overheating based on the operation result from the operation circuit.

[0056] Next, the operation of the semiconductor switch device 230 is described. First, the control circuit 236 receives a control instruction from the MCU 530 and performs various switch controls. The control circuit 236 outputs a drive voltage to the gates of the transistor 231 and the transistor 232 according to the control instruction. When the gates of the transistors 231 and 232 receive the drive voltage, they become conductive. Thus, the voltage output by the voltage source 330 is supplied to the load 430. Thus, a load current is supplied to the load 430. When the load current is supplied, the load 430 performs various operations.

[0057] The buffer circuit 234 receives the outputs of the transistor 231 and the transistor 232. The buffer circuit 234 outputs a voltage corresponding to the difference between the voltages output by the transistor 231 and the transistor 232 to the transistor 233. The transistor 233 supplies the load current signal to the ADC 237 according to the voltage output by the buffer circuit 234. The ADC 237 performs A / D conversion on the received load current signal. The square operation circuit 235 performs a square operation on the current signal after the A / D conversion. The ADC 239 receives the ambient temperature information from the MCU 530, performs A / D conversion on the received ambient information, and outputs the ambient temperature signal. The communication interface 238 receives various information from the MCU 530. The operation circuit 241 receives the current signal after the square operation, the signal from the communication interface 238, and the ambient temperature signal. The operation circuit 241 has, for example, a function for implementing Figure 1B The circuit of the wire thermal model is shown in Figure 1. Specifically, based on the ambient temperature signal, the Figure 1BThe voltage source Vat shown is shown. In addition, the thermal resistance Rthwc as a coefficient of heat transfer to the insulator 102, the thermal resistance Rthca as a coefficient of heat dissipation to the space, and the thermal capacitance Cthc as a delay coefficient are pre-loaded into the circuit. The operation circuit estimates the wire temperature by using these. Here, the operation circuit 241 can realize the thermal resistance Rthwc, the thermal resistance Rthca, and the thermal capacitance Cthc by hardware operation, and can also be realized by software that estimates the wire temperature using various coefficients. The overheat protection circuit 243 receives information related to the wire temperature estimated by the operation circuit 241, and determines whether to cut off the current flowing through the wire in order to protect the wire from overheating. In the case of determining that the current flowing through the wire is cut off, an overheat protection signal is output. The control circuit 236 outputs a current cutoff signal based on the overheat protection signal from the overheat protection circuit 243. Here, when the control circuit 236 receives the overheat protection signal from the overheat protection circuit 243, it performs on / off control of the transistor 231 and the transistor 232 with a higher priority than the instruction from the MCU 530. In addition, the control circuit 236 may also receive an overheat protection signal from the overheat protection circuit 243 through an interrupt process. The transistor 231 and the transistor 232 are turned off according to the current cutoff signal. Thus, the current supply to the load 400 is cut off. On the other hand, the information related to the wire temperature is output to the MCU 530 via the communication interface 238.

[0058] exist Fig. 9The semiconductor switch device 230 shown can be implemented by a logic circuit (hardware) formed in an integrated circuit (IC chip) or the like, or can be implemented by software. In the latter case, the semiconductor switch device 230 has a computer that executes commands of a program as software that implements each function. The computer has, for example, one or more processors and a computer-readable recording medium storing the program. In addition, in the computer, the processor reads the program from the recording medium and executes it, thereby implementing the semiconductor switch device 230. As the processor, for example, a CPU (Central Processing Unit) can be used. As the recording medium, in addition to "non-temporary tangible media" such as ROM (Read Only Memory), a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, etc. can also be used. In addition, a RAM (Random Access Memory) or the like that expands the program can also be provided. In addition, the program can be provided to the computer via any transmission medium (communication network or broadcast wave, etc.) that can transmit the program. In addition, in one or more embodiments, the above program can also be implemented in the form of a data signal embedded in a carrier wave that is embodied by electronic transmission. In addition, the ambient temperature signal supplied from the MCU 530 via the ADC 239 can also be supplied from the MCU 530 via the communication interface 238 .

[0059] As described above, according to the semiconductor switch device of one or more of the above-mentioned embodiments, by installing a load current square operation circuit on the semiconductor switch side, the wire temperature caused by the load current can be estimated inexpensively and accurately, so that the system can be safely driven by the semiconductor switch device.

[0060] Industrial Applicability

[0061] The present invention can be used, for example, for protecting wiring such as a wire harness equipped in a vehicle.

[0062] Description of symbols

[0063] 100: electric wire; 101: conductor; 102: insulator; 150: equivalent circuit of temperature model of electric wire; 152: current source; 154: Rw×Iw^2 output circuit; 200, 210, 220, 230, 250: semiconductor switch device; 201, 202, 203, 211, 212, 213, 221, 222, 223, 231, 232, 233, 251, 252, 253, 258: transistor; 204, 214, 224, 234, 254, 257: buffer circuit; 205, 215, 225, 235, 255: square operation circuit; 206, 216, 226, 236, 256: control circuit; 217: charging and discharging circuit; 227, 237, 239: analog-to-digital converter (ADC); 238: communication interface; 241: operation circuit; 243: overheat protection circuit; 259: comparator circuit; 261: reference voltage source; 300, 310, 320, 330, 340: voltage source; 400, 410, 420, 430, 440: load; 500, 510, 520, 530, 540: MCU; 601, 602, 621, 631, 642: resistor; 611, 641: capacitor; Q20, Q21, Q22, Q23, Q24, Q25: transistor; I20: current source; Ik: current source; VREG: power supply.

Claims

1. A semiconductor switch device, characterized in that: The semiconductor switch device has: a switch unit connected between a power source connected from outside the semiconductor switch device and a load via a wire, and turning on / off power supply to the load; a load current detection unit that detects a load current flowing through the switch unit; and a square operation unit that outputs a square value of the value of the load current detected by the current detection unit, The switch unit receives a control command from the outside, and turns on / off the power supply to the load according to the control command.

2. The semiconductor switch device according to claim 1, characterized in that: The semiconductor switch device further comprises: a charge-discharge unit that charges and discharges a capacitor connected from outside the semiconductor switch device within a predetermined voltage range based on a result of the square operation; as well as A pulse output unit outputs a pulse signal synchronized with the switching of the charge and discharge.

3. The semiconductor switch device according to claim 1, characterized in that: The semiconductor switch device further comprises: an ambient temperature information acquisition unit, which acquires the ambient temperature; and A calculation unit calculates electric wire heat generation based on the information on the ambient temperature and the output of the square calculation result unit.

4. The semiconductor switch device according to claim 3, characterized in that: The semiconductor switch device further includes an overheat protection circuit that determines whether the electric wire needs to be protected based on the heating temperature of the electric wire calculated by the calculation unit, and opens the switch unit when the temperature reaches a predetermined temperature or above.

5. The semiconductor switch device according to any one of claims 1 to 4, characterized in that: The semiconductor switch device is sealed in a resin package.

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