semiconductor switch device

Abstract

Provided is a semiconductor switch device which performs square integration of load current and wire temperature estimation at low cost and with high precision, while reducing resources required for accurate wire temperature estimation. A semiconductor switch device 200 according to one or more examples of the present invention includes: switch units 206, 201, and 202 that are connected between a power source 300 connected from the outside of the semiconductor switch device 200 and a load 400 through a wire, and that turn on / off power supply to the load; load current detection units 203 and 204 that detect load current flowing through the switch units 206, 201, and 202; and a square operation unit 205 that outputs a squared value of a load current value detected by the current detection units 203 and 204. The switch unit 206 receives a control command from outside and turns on / off power supply to the load on the basis of 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, a load, a semiconductor switch body, and the like from excessive heat generation due to an overcurrent. [Background technology]

[0002] The number of electronic devices installed in vehicles and other devices has been increasing in recent years. Electronic devices installed in vehicles and other devices are often electrically connected to the battery via wiring such as harnesses. Heat generated by wiring can lead to serious accidents such as smoke and fire, so temperature management of the wiring is extremely important. Electronic devices may be controlled on / off by semiconductor switches equipped with current detection circuits. The load current detected by the current detection circuit is discretely detected by a separate control device such as an MCU (Micro Controller Unit), and the detected current value is subjected to product-sum calculations based on a pre-set heat generation model for the wire to protect 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 using a microcomputer or other device to perform squaring operations. When the voltage exceeds a triangular wave signal, this overheat protection device outputs a sense current to a thermal equivalent circuit, and accumulates a charge in a capacitor in the thermal equivalent circuit that corresponds to the current value and the time the current flows. Furthermore, when the voltage increases n times, the time during which the voltage exceeds the triangular wave signal also increases n times, so the charge accumulated in the capacitor is proportional to the square of the sense current. Therefore, the voltage generated in the thermal equivalent circuit is proportional to the square of the load current and can be considered as an estimated temperature of the load-wire circuit. Therefore, the temperature of the load-wire circuit can be estimated without using a microcomputer or other device for squaring operations. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent No. 5097229 Summary of the Invention [Problem to be solved by the invention]

[0005] As the number of electronic devices installed in vehicles and other devices increases, the load on MCUs, which control various types of electronic devices installed in vehicles, is also increasing. In particular, when an MCU performs overheat protection control for all the electrical wires that electrically connect the electronic devices, the computational load increases explosively. In particular, with the recent increase in the number of electronic devices installed in vehicles and other devices, 1) the computational load increases as the number of outputs from the MCU semiconductor switch increases, and 2) the resources required for analog-to-digital conversion (A / D conversion) by the MCU to capture the load current increase. These factors lead to an increase in the number of electronic devices and an increase in costs. Furthermore, because the load current is detected discretely, it is not possible to adequately detect short-term increases in load current or surge-like fluctuations, resulting in large errors.

[0006] In addition, the technology disclosed in Patent Document 1 estimates the amount of heat generated in the load and uses this estimated amount of heat to monitor the overheating state of the load and electric wires. This technology requires many circuits to determine overheating.

[0007] The present invention has been made in consideration of the above circumstances, and its purpose is to provide a semiconductor switch device that performs square integration of load current and wire temperature estimation at low cost and with high accuracy while reducing the resources required for accurate wire temperature estimation. [Means for solving the problem]

[0008] A semiconductor switch device according to one or more embodiments includes a switch unit connected between a power source connected from outside the semiconductor switch device and a load via an electric wire, for turning on and off a power supply to the load, a load current detection unit for detecting a load current flowing in the switch unit, and a square calculation unit for outputting a square value of the load current detected by the load current detection unit. an environmental temperature information acquiring unit that acquires environmental temperature information from an external source; and a calculation unit that calculates a heat generation temperature of the electric wire from the environmental temperature information and an output of the square calculation unit;The power supply circuit includes a power supply unit that receives a control command from an external device and that turns on and off the power supply to the load based on the control command. [Effects of the Invention]

[0009] According to the above configuration, it is possible to provide a semiconductor switch device that performs square integration of load current and wire temperature estimation at low cost and with high accuracy while reducing resources required for accurate wire temperature estimation. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 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, and FIG. 1B is a diagram showing an equivalent circuit 150 of the temperature model of the electric wire shown in FIG. 1A, for example. [Figure 2] FIG. 2 is a diagram showing the relationship between the wire current and the wire temperature. [Figure 3] FIG. 3 is a diagram illustrating a semiconductor switch device 200 and peripheral circuitry according to one or more embodiments. [Figure 4] FIG. 4 is a diagram illustrating a square calculation circuit 205 according to one or more embodiments. [Figure 5] FIG. 5 is a diagram illustrating a semiconductor switch device 220 and peripheral circuitry according to one or more embodiments. [Figure 6] FIG. 6 is a diagram illustrating a semiconductor switch device 210 and peripheral circuitry according to one or more embodiments. [Figure 7] FIG. 7 is a diagram showing an example of a signal output by the charge / discharge circuit 217. As shown in FIG. [Figure 8] FIG. 8 is a diagram illustrating a semiconductor switch device 250 and peripheral circuitry according to one or more embodiments. [Figure 9] FIG. 9 is a diagram illustrating a semiconductor switch device 230 and peripheral circuitry according to one or more embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0011] A semiconductor switch device according to one or more embodiments will be described with reference to the drawings.

[0012] FIG. 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. For ease of explanation, this figure shows a cross-sectional view of the electric wire. The electric wire 100 includes a conductor 101 that supplies current and transmits electric signals, and an insulator 102 that covers the conductor 101 to insulate the conductor 101 from the outside. When a current flows through the electric wire 100, the resistance value R of the conductor 101 increases. W A loss occurs when the current Iw multiplied by the square of the current Iw flowing through the conductor 101. Most of this loss becomes thermal energy and the electric wire 100 generates heat. A portion of the generated loss is first transferred to the insulator 102 after a certain delay (Rthwc), and then dissipated as heat into space (Rthca). Here, an electric wire is a line that transmits electricity and refers to a linear component that electrically connects electronic components. In addition to general electric wires, it also includes wiring within a printed circuit board.

[0013] 1B is a diagram showing an equivalent circuit 150 of the temperature model of the electric wire shown in FIG. 1A, for example. The equivalent circuit 150 of the temperature model of the electric wire described above has a thermal resistance Rthwc of the insulator 102 and a thermal resistance Rthca of radiation from the insulator 102 to space between a current source Iw as a loss generating source and a voltage source Vat at the ambient temperature. The equivalent circuit shown in the figure has a current source 152 that generates a current Iw, and a thermal resistance Rthca of radiation from the insulator 102 to space that receives the current Iw and calculates Rw x Iw^2 The circuit 154 includes a circuit 154 that outputs a thermal resistance Rthwc and a thermal resistance Rthca that are electrically connected in series with the circuit 154, a thermal capacitance Cthc that is connected in parallel with the thermal resistance Rthwc and the thermal resistance Rthca, and a voltage source Vat. In FIG. 1B, an equivalent circuit showing a temperature model of an electric wire is calculated using a conductor 101. Here, there is often a time lag between the radiation of heat from the insulator 102 to the space and the generation of heat due to loss. For this reason, the equivalent circuit of this temperature model includes the thermal capacitance Cthc of the electric wire 100. By including this thermal capacitance Cthc, it is possible to provide an equivalent circuit of a temperature model with high accuracy.

[0014] Because the loss in an electric wire is proportional to the square of the current flowing through it, heat generation can increase significantly as the current increases. In this case, if the conductor temperature rises and reaches the insulator's smoking temperature, problems such as smoking may occur. To protect the electric wire from excessive heat generation, it is necessary to estimate the temperature of the electric wire using a temperature model, manage the temperature, and protect the wire as needed. On the other hand, to accurately estimate the temperature of the electric wire, the various parameters of the model must be accurate and the temperature estimation calculation must be performed in real time. However, shortening the interval between load current detection increases the load on the calculation processing of the MCU (Micro Controller Unit), etc., which increases the calculation load, so it is necessary to reduce the calculation load in this area.

[0015] Figure 2 shows the relationship between wire current and wire temperature. Generally, if no current flows through a wire for a certain period of time, the wire temperature will reach the ambient temperature Ta. The semiconductor switch device turns on, and the output voltage rises to the input voltage level (t1). Then, current is supplied to the load, and an inrush current flows in the load current, causing the wire temperature to rise rapidly. When the load current decreases and remains at the nominal current (t2), the wire loss decreases, and the wire temperature gradually drops to the ambient temperature Ta plus the temperature rise due to self-heating. Next, when an overload current flows through the wire (t3), the wire temperature rises again. If the ambient temperature rises or the wire temperature exceeds a certain value due to an overload (t4), the temperature will rise beyond the usable temperature limit of the insulator 102 covering the conductor 101, which may cause the wire to smoke or other damage. Therefore, it is necessary to preset a protection temperature below the smoke-generating temperature, for example, a temperature just before the smoke-generating temperature, and to cut off the load current when the protection temperature is reached. When the load current is cut off, the load voltage drops and the wire temperature drops.

[0016] FIG. 3 illustrates a semiconductor switch device 200 and its peripheral circuits according to one or more embodiments. As illustrated, the semiconductor switch device 200 is electrically connected between a voltage source 300 external to the semiconductor switch device 200 and a load 400. The semiconductor switch device 200 includes a load current detection circuit including a buffer circuit 204 and a transistor 203, which detects a load current from the load 400, and a squaring circuit that receives a current from the transistor 203 and outputs the square of the received current signal. The semiconductor switch device 200 also includes a control circuit 206 that receives a control command from an MCU (Micro Controller Unit) 500, and a switch unit including transistors 201 and 202 that are turned on and off by the control circuit 206. The voltage source 300 supplies a predetermined voltage to the semiconductor switch device 200. The voltage source 300 may be, for example, a device capable of supplying voltage, such as a battery mounted on a vehicle. The load 400 may be, for example, various electronic devices mounted on a vehicle and powered by a battery via an electric 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 a load current is supplied to the load 400, the load 400 performs various operations.

[0017] As shown in the figure, the gates of the transistors 201 and 202 are electrically connected to the control circuit 206. The drains of the transistors 201 and 202 are electrically connected to the voltage source 300. The source of the transistor 201 is electrically connected to the load 400 and the buffer circuit 204, and the source of the transistor 202 is electrically connected to the buffer circuit 204. The gate of the transistor 203 is electrically connected to the buffer circuit 204, the source of the transistor 203 is electrically connected to the source of the transistor 202, and the drain of the transistor 203 is electrically connected to the squaring circuit 205. The resistor 601 is electrically connected to the squaring circuit 205 and the drain of the transistor 203, and the resistor 602 is electrically connected to the squaring circuit 205 and the MCU 500. The semiconductor switch device 200 may be sealed in a single resin package.

[0018] Next, the operation of the semiconductor switch device 200 will be described. First, the control circuit 206 receives a control command from the MCU 500 and performs various switch controls. The control circuit 206 outputs a drive voltage to the gates of the transistors 201 and 202 based on the control command. When the drive voltage is received at the gates of the transistors 201 and 202, they are turned on. This causes the voltage output by the voltage source 300 to be supplied to the load 400. This causes a load current to be supplied to the load 400. When the load current is supplied, the load 400 performs various operations.

[0019] The buffer circuit 204 receives the outputs of the transistors 201 and 202. The buffer circuit 204 outputs a voltage corresponding to the difference between the voltages output by the transistors 201 and 202 to the transistor 203. The transistor 203 supplies a current to the squaring circuit 205 in accordance with the voltage output by the buffer circuit 204. The squaring circuit 205 performs a squaring operation based on the supplied current signal. Here, the squaring circuit 205 may supply a voltage signal proportional to the current level output by the transistor 203. In this case, a resistor 601 is connected from outside the semiconductor switch device 200. The squaring circuit 205 may receive the voltage value output by the transistor 203 and perform a squaring operation based on the voltage signal. The resistor 602 may be provided inside the semiconductor switch device 200. The MCU 500 performs analog-to-digital (A / D) conversion on the current value output by the squaring circuit 205 and calculates the loss in the wire electrically connecting the voltage source 300 and the load 400 based on the digitized current value. The MCU 500 estimates the temperature of the wire based on the calculated wire loss, determines whether the wire has reached a protection temperature based on the estimated temperature, and outputs a current cut-off voltage to the control circuit 206 if it determines that the wire has reached the protection temperature. The transistors 201 and 202 are turned off based on the current cut-off voltage, thereby cutting off the current supply to the load 400. Here, the MCU 500 may be unable to read the current value. In such a case, a resistor 602 is connected from outside the semiconductor switch device 200. The MCU 500 may receive the voltage value output by the semiconductor switch device 200, A / D convert the voltage value, and calculate the loss in the wire electrically connecting the voltage source 300 and the load 400 based on the digitized current value. The resistor 602 may be provided inside the semiconductor switch device 200 .

[0020] 3 can perform, with a simple circuit configuration, the square integration of the load current required to calculate the loss in the electric wires electrically connecting the load 400. This reduces the load on the MCU 500 and enables inexpensive and highly accurate square integration of the load current.

[0021] FIG. 4 illustrates a squaring circuit according to one or more embodiments. In FIG. 4, the base and collector of transistor Q20 are electrically connected to power supply VREG, and the emitter of transistor Q20 is electrically connected to input terminal Iin1 and the base of transistor Q21. The collector of transistor Q21 is electrically connected to power supply VREG, and the emitter is electrically connected to input terminal Iin2 and the base of transistor Q22. The emitter of transistor Q22 is electrically connected to the emitter of transistor Q23 and one end of current source I20. The collector of transistor Q22 is electrically connected to the base of transistor Q24 and the emitter of transistor Q25.

[0022] 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 composed of other transistors, and form a multiplication / division circuit.

[0023] Next, the operation of the square calculation circuit shown in Figure 4 will be explained. First, current Iin1 is input to input terminal Iin1. Current Iin2 is input to input terminal Iin2. Current source Ik outputs current Ik. In this case, (Iin1 x Iin2) / Ik is output to output terminal Iout. If Iin1 and Iin2 are Iin, and the current Ik output by current source Ik is a fixed value, for example, Ik = 1 / K, then Iout = K Iin 2 and can output a current that is the square of the input current. However, the current output from the output terminal Iout is limited to be equal to or less than the bias current of the current source I20. The entire contents of U.S. patent application Ser. No. 12 / 428,587, particularly the description of the squaring circuit, are incorporated herein by reference.

[0024] 5 is a diagram illustrating a semiconductor switch device 220 and peripheral circuits according to one or more embodiments. As illustrated, the semiconductor switch device 220 is electrically connected between a voltage source 320 provided external to the semiconductor switch device 220 and a load 420. The semiconductor switch device 220 includes a load current detection circuit that includes a buffer circuit 224 and a transistor 223 and supplies a current to the load 420, an analog-to-digital converter (ADC) 227 that performs analog-to-digital conversion (A / D conversion) on the load current detected by the load current detection circuit, and a squaring circuit 225 that receives the signal converted by the ADC 227 and outputs the square value of the squared load current.

[0025] The semiconductor switch device 220 also has a switch section including a control circuit 226 that receives control commands from an MCU (Micro Controller Unit) 520 and transistors 221 and 222 that are turned on and off by the control circuit 226. A voltage source 320 supplies a predetermined voltage to the semiconductor switch device 220. The voltage source 320 includes a device capable of supplying voltage, such as a battery mounted on a vehicle. The load 420 includes, for example, various electronic devices mounted on a vehicle and supplied with power from the battery via electric 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. A resistor 621 is electrically connected to the ADC 227 and the drain of the transistor 223.

[0026] Next, the operation of the semiconductor switch device 220 will be described. First, the control circuit 226 receives a control command from the MCU 520 and performs various switch controls. The control circuit 226 outputs a drive voltage to the gates of the transistors 221 and 222 based on the control command. When the drive voltage is received at the gates of the transistors 221 and 222, they are turned on. This causes the voltage output by the voltage source 320 to be supplied to the load 420. This causes a load current to be supplied to the load 420. When the load current is supplied, the load 420 performs various operations.

[0027] The buffer circuit 224 receives the outputs of the transistors 221 and 222. The buffer circuit 224 outputs a voltage corresponding to the difference between the voltages output by the transistors 221 and 222 to the transistor 223. The transistor 223 supplies a current to the ADC 227 in accordance with the voltage output by the buffer circuit 224. The ADC 227 performs analog-to-digital conversion (A / D conversion) on 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. The ADC 227 may read the current signal converted into a voltage by the resistor 621. The squaring circuit 225 receives the digital signal output from the ADC 227 and performs squaring on the digital signal. The squaring circuit 225 outputs the result of the squaring to the MCU 520 as a digital signal. MCU 520 receives the digital signal output by square calculation circuit 225 and calculates the loss in the wire electrically connecting voltage source 320 and load 420 based on the digital signal. MCU 520 estimates the temperature of the wire based on the calculated wire loss, determines whether the wire has reached a protection temperature based on the estimated temperature, and if it determines that the wire has reached the protection temperature, outputs a current cut-off instruction to control circuit 226. Based on the current cut-off instruction, control circuit 226 turns transistors 221 and 222 off. This cuts off the current supply to load 420.

[0028] 5, the MCU 520 receives the digitized result of the squaring operation, eliminating the need for A / D conversion by the MCU 520. This allows the square integration of the load current required to calculate the loss in the wires electrically connecting the load 420 to be performed with a simple circuit configuration, reducing the load on the MCU 520 while enabling inexpensive and highly accurate square integration of the load current.

[0029] FIG. 6 illustrates a semiconductor switch device 210 and its peripheral circuits according to one or more embodiments. As illustrated, the semiconductor switch device 210 is electrically connected between a voltage source 310 external to the semiconductor switch device 210 and a load 410. The semiconductor switch device 210 includes a load current detection circuit including a buffer circuit 214 and a transistor 213, which supplies a current to the load 410, and a square calculation circuit 215 that outputs the square of the detected load current. The semiconductor switch device 210 also includes a control circuit 216 that receives control commands from an MCU (Micro Controller Unit) 510, and a switch unit including transistors 211 and 212 that are turned on and off by the control circuit 216. The voltage source 310 supplies a predetermined voltage to the semiconductor switch device 210. The voltage source 310 may be, for example, a device capable of supplying voltage, such as a battery mounted on a vehicle. The load 410 may be, for example, various electronic devices mounted on a vehicle and receiving power from the battery via an electric 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 a load current is supplied, the load 410 performs various operations.

[0030] 6 includes a charging / discharging circuit 217 electrically connected to a square calculation circuit 215 and an MCU 510. The charging / discharging circuit 217 is electrically connected to a capacitor 611 connected from the outside of the semiconductor switching device 210, and charges and discharges the capacitor 611 within a predetermined voltage range.

[0031] Next, the operation of the semiconductor switch device 210 will be described. First, the control circuit 216 receives a control command from the MCU 510 and performs various switch controls. The control circuit 216 outputs a drive voltage to the gates of the transistors 211 and 212 based on the control command. When the drive voltage is received at the gates of the transistors 211 and 212, they are turned on. This causes the voltage output by the voltage source 310 to be supplied to the load 410. This causes a load current to be supplied to the load 410. When the load current is supplied, the load 410 performs various operations.

[0032] The buffer circuit 214 receives the outputs of the transistors 211 and 212. The buffer circuit 214 outputs a voltage corresponding to the difference between the voltages output by the transistors 211 and 212 to the transistor 213. The transistor 213 supplies a current to the squaring circuit 215 in accordance with the voltage output by the buffer circuit 214. The squaring circuit 215 performs a squaring operation based on the supplied current signal. Next, the charging / discharging circuit 217 converts the current signal output by the squaring circuit 215 into a pulse signal by charging / discharging a capacitor 611. Receiving the pulse signal simplifies the reception of signals from the semiconductor switch device 200 for the MCU 510. The period of the pulse signal can be changed by adjusting the capacitance of the capacitor 611. The capacitor 611 may also be configured to perform corrections to the squaring operation of the wire loss. There is often a time lag between the radiation of heat from the insulator of the wire model into space and the generation of heat due to loss. Therefore, by charging and discharging the capacitor 611, the heat capacitance Cthc of the electric wire in the equivalent circuit of the temperature model can be taken into account. By taking this heat capacitance Cthc into account, the load on the MCU 510 can be calculated with high accuracy. Furthermore, the charge / discharge circuit 217 may correct the square calculation taking the heat capacitance Cthc into account, then A / D convert the corrected square calculation result and output it to the MCU 510. The MCU 510 calculates the loss of the electric wire electrically connecting the voltage source 310 and the load 410 based on the current value digitized by the charge / discharge circuit 217. The MCU 510 estimates the temperature of the electric wire based on the calculated wire loss, determines whether the electric wire has reached a protection temperature based on the estimated temperature, and outputs a current cut-off instruction to the control circuit 216 if it determines that the electric wire has reached the protection temperature. Based on the current cut-off instruction, the control circuit 216 turns off the transistors 211 and 212. This cuts off the current supply to the load 410. Here, capacitor 611 may be provided externally and replaceably to semiconductor switch device 210. By making capacitor 611 replaceable, it is possible to accommodate voltage sources 310 having different output voltages and loads 410 having different thermal characteristics.

[0033] 6 can perform square integration of the load current required to calculate the loss in the wire electrically connecting the load 410 with a simple circuit configuration. Here, the charge / discharge circuit 217 generates a pulse signal using the capacitor 611, which allows the MCU 510 to easily receive a signal from the semiconductor switch device 210. This allows the MCU 510 to receive a signal from the semiconductor switch device 210 with a simple circuit configuration. Furthermore, the charge / discharge circuit 217 can perform square integration taking into account the time difference in heat radiation from the insulator of the wire thermal model to space.

[0034] 6 realizes a configuration in which even the product-sum calculation of the wire loss is incorporated into the switch element side by outputting the result of the square calculation of the load current as a current and charging / discharging the capacitor, as compared with the embodiment of the semiconductor switch device shown in Fig. 3. Here, the charge / discharge circuit 217 may output a pulse signal to the MCU 510 in synchronization with switching between charging and discharging of the capacitor 611.

[0035] FIG. 7 is a diagram showing an example of a signal output by the charge / discharge circuit 217. The MCU 510 receives the squared calculation result as shown in the figure from the semiconductor switch device 210. As shown in FIG. 6, the charge / discharge circuit 217 outputs a pulse signal representing the squared calculation result, synchronized with the switching of the charge and discharge of the capacitor 603. By outputting this pulse signal to the MCU 510, a low-frequency pulse signal is output when the wire current is low, and a high-frequency pulse signal is output when the wire current is high. This configuration allows the MCU 510 to continuously monitor the load current as an analog value, thereby obtaining information including the influence of short-pulse surge currents. This allows accurate wire temperature estimation while reducing the calculation load on the MCU 510.

[0036] FIG. 8 illustrates a semiconductor switch device 250 and its peripheral circuits according to one or more embodiments. As illustrated, the semiconductor switch device 250 is electrically connected between a voltage source 340 and a load 440, both of which are external to 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) that detects a load current from the load 440, and a square calculation circuit 255 that outputs the square of the received current signal. The semiconductor switch device 250 also includes a control circuit 256 that receives control commands from an MCU (Micro Controller Unit) 540, and a switch unit including transistors 251 and 252 that are turned on and off by the control circuit 256. The voltage source 340 supplies a predetermined voltage to the semiconductor switch device 250. The voltage source 340 may be, for example, a device capable of supplying voltage, such as a battery mounted on a vehicle. The load 440 may be, for example, various electronic devices mounted on a vehicle that receive power from the battery via an electric 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 a load current is supplied, the load 440 performs various operations.

[0037] 8 includes a buffer circuit 257, a transistor 258, and a comparator circuit 259. A capacitor 641 and a resistor 642 are electrically connected to the buffer circuit 257, the squaring circuit 255, and the comparator circuit 259. The capacitor 641 and the resistor 642 may be provided outside the semiconductor switch device 250 or inside the semiconductor switch device 250.

[0038] Next, the operation of the semiconductor switch device 250 will be described. First, the control circuit 256 receives a control command from the MCU 540 and performs various switch controls. The control circuit 256 outputs a drive voltage to the gates of the transistors 251 and 252 based on the control command. When the drive voltage is received at the gates of the transistors 251 and 252, they are turned on. This causes the voltage output by the voltage source 340 to be supplied to the load 440. This causes a load current to be supplied to the load 440. When the load current is supplied, the load 440 performs various operations.

[0039] The buffer circuit 254 receives the outputs of the transistors 251 and 252. The buffer circuit 254 outputs a voltage corresponding to the difference between the voltages output by the transistors 251 and 252 to the transistor 253. The transistor 253 supplies a current signal to the squaring circuit 255 in accordance with the voltage output by the buffer circuit 254. The squaring circuit 255 performs a squaring operation based on the supplied current signal. The buffer circuit 257 receives information related to the ambient temperature from the MCU 540 and outputs a voltage corresponding to the information. The comparator circuit 259 compares the estimated wire temperature signal, which is obtained by adding the current signal resulting from the squaring operation to the capacitor 641 and the resistor 642, to the output of the buffer circuit 257, with the voltage output by the reference voltage source 261, and outputs the result 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 transistors 251 and 252. This cuts off the current supply to the load 440. Furthermore, when the transistor 258 receives a voltage equal to or higher than a predetermined voltage from the comparator circuit 259, it notifies the MCU 540 of fault information (Fault).

[0040] The semiconductor switch device 250 shown in FIG. 8 differs from the semiconductor switch device 200 shown in FIG. 3 in that it includes a buffer circuit 257 that receives an input voltage signal reflecting the ambient temperature and a control circuit 256 that electrically connects a parallel circuit of a resistor 642 and a capacitor 641 that reflects a wire thermal model between the buffer circuit 257 and the square calculation circuit 255. The control circuit 256 shuts off transistors 251 and 252 when the output voltage of the square calculation circuit 255 (estimated wire temperature) exceeds a predetermined value. By obtaining ambient temperature information from the MCU 540, the semiconductor switch device 250 can estimate and protect the wire temperature, thereby achieving wire protection with fewer resources. Accurate wire temperature estimation also enables more accurate temperature estimation compared to the melting characteristics of fuses, which have traditionally been used to protect wires. This saves resources by optimizing the wire diameter and reduces transportation costs by reducing weight. Furthermore, by receiving ambient temperature information from the MCU 540, the semiconductor switch device 250 can achieve wire temperature protection. Therefore, with the recent increase in electronic devices mounted on vehicles, the control processing of the MCU increases, but by having the semiconductor switch device 250 perform the above processing, it becomes possible to perform control with a cheaper MCU.

[0041] FIG. 9 illustrates a semiconductor switch device 230 and its peripheral circuits according to one or more embodiments. As illustrated, the semiconductor switch device 230 is electrically connected between a voltage source 330 external to the semiconductor switch device 230 and a load 430. The semiconductor switch device 230 includes a load current detection circuit including a buffer circuit 234 and a transistor 233, which supplies a current to the load 430, and a square calculation circuit 235 that outputs the square of the detected load current. The semiconductor switch device 230 also includes a control circuit 236 that receives control commands from an MCU (Micro Controller Unit) 530, and a switch unit including transistors 231 and 232 that are turned on and off by the control circuit 236. The voltage source 330 may be a device capable of supplying a voltage, such as a battery mounted on a vehicle. The load 430 may be, for example, various electronic devices mounted on a vehicle that receive power from the battery via an electric wire. 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 a load current is supplied to the load 430, the load 430 performs various operations.

[0042] As shown in the figure, the semiconductor switch device 230 shown in FIG. 9 includes: an ADC 237 that receives a current from a transistor 233 and A / D converts the received current signal; a squaring circuit 235 that receives the output of the ADC 237 and performs a squaring operation; a communication interface (I / F) 238 that communicates with an MCU 530; an ADC 239 that receives environmental temperature information from the MCU 530, A / D converts the received environmental information, and outputs an environmental temperature signal; an arithmetic circuit 241 that receives the calculation result of the squaring circuit 235 and the environmental temperature signal from the ADC 239 and performs various calculations; and an overheat protection circuit 243 that determines whether or not overheat protection is required for the wires electrically connecting the voltage source 330 and the load 430, based on the calculation result from the arithmetic circuit.

[0043] Next, the operation of the semiconductor switch device 230 will be described. First, the control circuit 236 receives a control command from the MCU 530 and performs various switch controls. The control circuit 236 outputs a drive voltage to the gates of the transistors 231 and 232 based on the control command. When the drive voltage is received at the gates of the transistors 231 and 232, they are turned on. This causes the voltage output by the voltage source 330 to be supplied to the load 430. This causes a load current to be supplied to the load 430. When the load current is supplied, the load 430 performs various operations.

[0044] The buffer circuit 234 receives the outputs of the transistors 231 and 232. The buffer circuit 234 outputs a voltage corresponding to the difference between the voltages output by the transistors 231 and 232 to the transistor 233. The transistor 233 supplies a load current signal to the ADC 237 in accordance with the voltage output by the buffer circuit 234. The ADC 237 A / D converts the received load current signal. The squaring circuit 235 performs a squaring operation on the A / D converted current signal. The ADC 239 receives environmental temperature information from the MCU 530, A / D converts the received environmental information, and outputs an environmental temperature signal. The communication interface 238 receives various information from the MCU 530. The arithmetic circuit 241 receives the squared current signal, a signal from the communication interface 238, and an environmental temperature signal. The arithmetic circuit 241 has, for example, a circuit for implementing the wire thermal model shown in FIG. 1B. Specifically, the voltage source Vat shown in FIG. 1B is calculated based on the environmental temperature signal. Additionally, the thermal resistance Rthwc, which is the coefficient of heat transfer to the insulator 102; the thermal resistance Rthca, which is the coefficient of heat dissipation into the air; and the thermal capacitance Cthc, which is the delay coefficient, are pre-integrated into the circuit. Using these, the calculation circuit estimates the wire temperature. The calculation circuit 241 can implement the thermal resistance Rthwc, the thermal resistance Rthca, and the thermal capacitance Cthc through hardware calculations, or it can be implemented as software that estimates the wire temperature using various coefficients. The overheat protection circuit 243 receives information about the wire temperature estimated by the calculation circuit 241 and determines whether to interrupt the current flowing through the wire to protect the wire from overheating. If it is determined that the current flowing through the wire should be interrupted, it outputs an overheat protection signal. The control circuit 236 outputs a current interruption signal in response to the overheat protection signal from the overheat protection circuit 243. Here, when the control circuit 236 receives an overheat protection signal from the overheat protection circuit 243, it may control the on / off of the transistors 231 and 232 with a higher priority than a command from the MCU 530. Alternatively, the control circuit 236 may receive the overheat protection signal from the overheat protection circuit 243 by interrupt processing. The transistors 231 and 232 are turned off based on the current cutoff signal. This cuts off the current supply to the load 400.On the other hand, information relating to the wire temperature is output to the MCU 530 via the communication interface 238.

[0045] The semiconductor switch device 230 shown in FIG. 9 may be realized by a logic circuit (hardware) formed on an integrated circuit (IC chip) or the like, or by software. In the latter case, the semiconductor switch device 230 includes a computer that executes instructions of a program, which is software that realizes each function. This computer includes, for example, one or more processors and a computer-readable recording medium storing the program. The processor in the computer reads and executes the program from the recording medium, thereby implementing the semiconductor switch device 230. The processor may be, for example, a CPU (Central Processing Unit). The recording medium may be a "non-transitory tangible medium," such as a ROM (Read Only Memory), a tape, a disk, a card, a semiconductor memory, or a programmable logic circuit. The semiconductor switch device 230 may also include a RAM (Random Access Memory) for expanding the program. The program may be supplied to the computer via any transmission medium capable of transmitting the program (such as a communication network or broadcast waves). Note that one or more embodiments may also be realized in the form of a data signal embedded in a carrier wave, in which the program is embodied by electronic transmission. Furthermore, the environmental temperature signal supplied from the MCU 530 via the ADC 239 may be supplied from the MCU 530 via the communication interface 238 .

[0046] As described above, according to the semiconductor switch device according to one or more of the above-mentioned embodiments, by incorporating a load current square calculation circuit on the semiconductor switch side, it is possible to inexpensively and accurately estimate the wire temperature caused by the load current, and therefore the system can be safely driven by the semiconductor switch device. [Industrial Applicability]

[0047] The present invention can be used, for example, to protect wiring such as harnesses mounted on a vehicle. [Explanation of symbols]

[0048] 100 wire 101 Conductors 102 Insulator 150 Equivalent circuit of temperature model of electric wire 152 Current source 154 Rw x Iw^2 output circuit 200, 210, 220, 230, 250 Semiconductor switch devices 201,202,203,211,212,213,221,222,223,231,232,233,251,252,253,258 transistors 204,214,224,234,254,257 Buffer circuit 205,215,225,235,255 Square operation circuit 206,216,226,236,256 Control circuit 217 Charge / discharge circuit 227,237,239 Analog-to-Digital Converter (ADC) 238 Communication Interface 241 Arithmetic 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 Resistance 611,641 Capacitors Q20, Q21, Q22, Q23, Q24, Q25 transistors I20 current source Ik current source VREG power supply

Claims

1. In a semiconductor switch device, a switch section connected between a power source connected from outside the semiconductor switch device and a load via an electric wire, for turning on and off the power supply to the load; a load current detection unit that detects a load current flowing in the switch unit; a square calculation unit that outputs a square value of the load current detected by the load current detection unit; an environmental temperature information acquisition unit that acquires environmental temperature information from the outside; a calculation unit that calculates a heat generation temperature of the electric wire from the environmental temperature information and an output of the square calculation unit; Including, A semiconductor switch device, characterized in that it receives a control command from an external device, and the switch unit turns on / off the power supply to the load based on the control command.

2. The semiconductor switch device is a charge / discharge unit that charges / discharges a capacitor connected from outside the semiconductor switch device within a predetermined voltage range based on the square calculation result; a pulse output unit that outputs a pulse signal synchronized with the switching of the charging and discharging; 2. The semiconductor switch device according to claim 1, further comprising:

3. The semiconductor switch device is 2. The semiconductor switch device according to claim 1, further comprising an overheat protection circuit that determines whether protection of the electric wire is necessary based on the electric wire heat generation temperature calculated by the calculation unit, and turns off the switch unit when the temperature reaches a predetermined temperature or higher.

4. A semiconductor switch device, a switch section connected between a power source connected from outside the semiconductor switch device and a load via an electric wire, for turning on and off the power supply to the load; a load current detection unit that detects a load current flowing in the switch unit; a square calculation unit that outputs a square value of the load current detected by the load current detection unit; Including, receiving a control command from an external device, and the switch unit turns on / off the power supply to the load based on the control command; The square calculation unit Power supply and a first transistor including a base and a collector, the base and the collector electrically connected to the power supply; a second transistor including a base and a collector, the base electrically connected to the emitter of the first transistor and the first input terminal, and the collector electrically connected to the power supply; a third transistor including a base electrically connected to the emitter of the second transistor and to a second input terminal; a fourth transistor including an emitter and a collector, the emitter electrically connected to the emitter of the third transistor and a current source, and the collector connected to an output terminal; a fifth transistor including an emitter and a collector, the emitter electrically connected to the base of the fourth transistor and the collector electrically connected to the current source; a sixth transistor including an emitter and a collector, the emitter being electrically connected to the collector of the third transistor and the base of the fifth transistor, and the collector being electrically connected to the current source; 1. A semiconductor switch device comprising:

5. In a semiconductor switch device, a switch unit connected between a power source connected from outside the semiconductor switch device and a load via an electric wire, for turning on and off the power supply to the load; a load current detection unit that detects a load current flowing in the switch unit; a first analog-to-digital conversion unit that receives the load current detected by the load current detection unit and performs analog-to-digital conversion; a square calculation circuit that receives the digitally converted load current signal and outputs a square value; a second analog-to-digital conversion unit that receives the environmental temperature signal and performs analog-to-digital conversion; an arithmetic circuit that receives the digitally converted environmental temperature signal and the squared value, and estimates the electric wire temperature based on the digitally converted environmental temperature signal and the squared value; an overheat protection circuit that receives information about the estimated electric wire temperature and outputs an overheat protection signal when it determines to cut off the current flowing through the electric wire; a control unit that receives a control command from an external device and switches the switch unit based on the control command and the overheat protection signal; 1. A semiconductor switch device comprising:

6. the arithmetic circuit includes an electric wire thermal model circuit that models the electric wire with a conductor and an insulator that insulates the conductor from the outside, the electric wire thermal model circuit includes a first thermal resistance that is a thermal resistance model of the insulator, a second thermal resistance that is a model of radiation from the insulator to space, and a thermal capacitance that is a heat capacity model of the conductor; 6. The semiconductor switch device according to claim 5, wherein the arithmetic circuit estimates the wire temperature based on the squared value, the wire thermal model circuit, and a voltage source modeled based on the environmental temperature signal.

7. A semiconductor switch device, a switch unit connected between a power source connected from outside the semiconductor switch device and a load via an electric wire, for turning on and off the power supply to the load; a load current detection unit that detects a load current flowing in the switch unit; a first analog-to-digital conversion unit that receives the load current detected by the load current detection unit and performs analog-to-digital conversion; a square calculation circuit that receives the digitally converted load current signal and outputs a square value; an arithmetic circuit that receives an environmental temperature signal and the squared value and estimates a wire temperature based on the environmental temperature signal and the squared value; an overheat protection circuit that receives information about the estimated electric wire temperature and outputs an overheat protection signal when it determines to cut off the current flowing through the electric wire; a control unit that receives a control command from an external device and switches the switch unit based on the control command and the overheat protection signal; 1. A semiconductor switch device comprising:

8. The arithmetic circuit includes an electric wire thermal model circuit that models the electric wire using a conductor and an insulator that insulates the conductor from the outside, the electric wire thermal model circuit includes a first thermal resistance that is a thermal resistance model of the insulator, a second thermal resistance that is a model of radiation from the insulator to space, and a thermal capacitance that is a heat capacity model of the conductor; 8. The semiconductor switch device according to claim 7, wherein the arithmetic circuit estimates the wire temperature based on the squared value, the wire thermal model circuit, and a voltage source modeled based on the environmental temperature signal.

9. The semiconductor switch device is 9. The semiconductor switch device according to claim 1, wherein the semiconductor switch device is sealed in a single resin package.

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