Protection device, load driving system, and protection method

Abstract

To provide a protective device capable of protecting a load driving system at a proper timing according to temperature of a power semiconductor.SOLUTION: A protective device comprises: a capacitor outputting a voltage according to electric charge accumulated by a first current; and a protection circuit r determining whether a voltage output from the capacitor exceeds a constant threshold or not, generating a second current with a magnitude corresponding to information on temperature of a power semiconductor driving a load, and changing the magnitude of the first current based on the generated second current.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a protection device, a load driving system, and protection method and the like.

Background Art

[0002] In a load driving system that drives a load using a power semiconductor, when the power semiconductor is short-circuited, a large current exceeding the allowable value may flow. Therefore, some load driving systems are provided with a protection device that prevents a large current from flowing through the load driving system when a short circuit of the power semiconductor is detected.

[0003] Patent Document 1 describes a technique related to a protection device that protects a load driving system at an appropriate timing according to the temperature of a power semiconductor by changing a threshold value for determining overcurrent in the load driving system according to the temperature of the power semiconductor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Incidentally, the short-circuit withstand of a power semiconductor decreases as the junction temperature increases. Therefore, in a load driving system, when the junction temperature of the power semiconductor is high, it is necessary to perform a protection operation in a shorter time than when the junction temperature is low. Therefore, there is a need for a technique (different from Patent Document 1) that can protect a load driving system at an appropriate timing according to the temperature of a power semiconductor.

[0006] The present disclosure can solve the above problems, a protection device, a load driving system,and protection method It aims to provide...

Means for Solving the Problem

[0007] To solve the above problems, the protection device according to the present disclosure is... A protection device for protecting a power semiconductor that drives a load from a short circuit, comprising: a capacitor that outputs a voltage corresponding to the charge accumulated by a first current, which is a current that changes according to the presence or absence of a short circuit in the power semiconductor; and a protection circuit that determines whether the voltage output by the capacitor exceeds a certain threshold value, generates a second current having a magnitude corresponding to information related to the temperature of the power semiconductor, and changes the magnitude of the first current based on the generated second current. The protection circuit includes a current generation circuit that generates the second current, and the current generation circuit includes a voltage generation circuit that generates a voltage whose value changes according to the temperature of the power semiconductor, a first operational amplifier, a second operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor. The non-inverting input terminal of the first operational amplifier is connected to the voltage generation circuit, the inverting input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier and the first terminal of the first resistor, the non-inverting input terminal of the second operational amplifier is connected to the first terminal of the third resistor and the first terminal of the fourth resistor, the inverting input terminal of the second operational amplifier is connected to the second terminal of the first resistor and the first terminal of the second resistor, the output terminal of the second operational amplifier is connected to the second terminal of the second resistor and the first terminal of the fifth resistor, the second terminal of the fourth resistor is connected to the second terminal of the fifth resistor and the capacitor, and the second terminal of the third resistor is connected to the ground terminal .

[0008] The load driving system according to the present disclosure includes the above protection device and a driving device including a power semiconductor to be protected by the protection device.

[0009] The protection method according to the present disclosure is... A protection device comprising a capacitor and a protection circuit, and a protection method executed by the protection device for protecting a power semiconductor that drives a load from a short circuit, wherein the capacitor outputs a voltage corresponding to the charge accumulated by a first current that is a current that changes according to the presence or absence of a short circuit of the power semiconductor; the protection circuit determines whether or not the voltage output by the capacitor exceeds a certain threshold value, generates a second current having a magnitude corresponding to information related to the temperature of the power semiconductor, and changes the magnitude of the first current based on the generated second current; the protection circuit includes a current generation circuit that generates the second current, the current generation circuit includes a voltage generation circuit that generates a voltage whose value changes according to the temperature of the power semiconductor, a first operational amplifier, a second operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor; a non-inverting input terminal of the first operational amplifier is connected to the voltage generation circuit; an inverting input terminal of the first operational amplifier is connected to an output terminal of the first operational amplifier and a first terminal of the first resistor; a non-inverting input terminal of the second operational amplifier is connected to a first terminal of the third resistor and a first terminal of the fourth resistor; an inverting input terminal of the second operational amplifier is connected to a second terminal of the first resistor and a first terminal of the second resistor; an output terminal of the second operational amplifier is connected to a second terminal of the second resistor and a first terminal of the fifth resistor; a second terminal of the fourth resistor is connected to a second terminal of the fifth resistor and the capacitor; and a second terminal of the third resistor is connected to a ground terminal .

Advantages of the Invention

[0011] According to the protection device, load driving system, protection method, and program according to the embodiments of the present disclosure, the load driving system can be protected at an appropriate timing according to the temperature of the power semiconductor.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0013] <Embodiment> Hereinafter, a load driving system according to an embodiment of the present disclosure will be described. (Configuration of Load Driving System) FIG. 1 is a diagram showing a first example of the configuration of a load driving system 1 according to an embodiment of the present disclosure. As shown in FIG. 1, the load driving system 1 includes a driving device 10 and a protection device 20. Note that FIG. 1 shows a load 30 to be driven by the driving device 10. FIG. 2 is a diagram showing a second example of the configuration of the load driving system 1 according to an embodiment of the present disclosure. The load driving system 1 shown in FIG. 2 is one of the specific examples of the load driving system 1 shown in FIG. 1.

[0014] The driving device 10 is a device that drives the load 30 using a power semiconductor. The driving device 10 includes, for example, N-channel MOS (Metal Oxide Semiconductor) transistors (hereinafter referred to as NMOS) 101 and 102 as shown in FIG. 2. The NMOSs 101 and 102 are power semiconductors. When the NMOS 101 is in the on state, the NMOS 102 is in the off state, and a current flows from the NMOS 101 toward the load 30. When the NMOS 101 is in the off state, the NMOS 102 is in the on state, and a current is drawn from the load 30 toward the NMOS 102. However, a dead time may be provided so that the NMOS 101 and the NMOS 102 are not simultaneously in the on state (that is, so that a through current does not flow). A power supply 40 is connected between the source of the NMOS 101 and the drain of the NMOS 102. The voltage output by the power supply 40 is, for example, several hundred volts.

[0015] The protection device 20 is a device that protects the load driving system at a timing according to the temperature of the power semiconductor included in the driving device 10. As shown in FIG. 2, the protection device 20 includes protection circuits 20a and 20b. Each of the protection circuits 20a and 20b has terminals A, B, C, and D. And for each of the protection circuits 20a and 20b, a power supply 50 is connected between terminal C and terminal A. The voltage output by the power supply 50 is, for example, several tens of volts. Specific examples of terminals A, B, C, and D will be described later.

[0016] FIG. 3 is a diagram showing an example of the configuration of the protection circuits 20a and 20b according to an embodiment of the present disclosure. As shown in FIG. 3, each of the protection circuits 20a and 20b includes an operational amplifier (hereinafter referred to as an op-amp) 201, 202, a thermistor 203 (an example of a voltage generation circuit), resistors 204, 205, 206, 207, 208, 209, 210, 211, a diode 212, a capacitor 213, and a detection device 214.

[0017] The non-inverting input terminal of the op-amp 201 is connected to the first terminal of the thermistor 203 and the first terminal of the detection device 214. The inverting input terminal of the op-amp 201 is connected to the output terminal of the op-amp 201 and the first terminal of the resistor 207.

[0018] The non-inverting input terminal of the op-amp 202 is connected to the first terminal of the resistor 209 and the first terminal of the resistor 210. The inverting input terminal of the op-amp 202 is connected to the second terminal of the resistor 207 and the first terminal of the resistor 208. The output terminal of the op-amp 202 is connected to the second terminal of the resistor 208 and the first terminal of the resistor 211.

[0019] The second terminal of the thermistor 203 is connected to the ground terminal. The first terminal of the resistor 204 is connected to the power supply terminal. The second terminal of the resistor 204 is connected to the first terminal of the resistor 205 and the anode of the diode 212. The second terminal of the resistor 205 is connected to the first terminal of the resistor 206, the second terminal of the resistor 210, the second terminal of the resistor 211, the first terminal of the capacitor 213, and the second terminal of the detection device 214. The second terminal of the resistor 206, the second terminal of the resistor 209, the second terminal of the capacitor 213, the third terminal of the detection device 214, and the fourth terminal of the detection device 214 are connected to the ground terminal. Note that the power supply terminal is a specific example of the terminal A of the protection circuits 20a and 20b. Also, the cathode of the diode 212 is a specific example of the terminal B of the protection circuits 20a and 20b. Also, the ground terminal is a specific example of the terminal C of the protection circuits 20a and 20b. Also, the fifth terminal of the detection device 214 is a specific example of the terminal D of the protection circuits 20a and 20b.

[0020] The detection device 214 is a device that detects a short circuit between the NMOSs 101 and 102 in the drive device 10. FIG. 4 is a diagram showing an example of the configuration of the detection device 214 according to an embodiment of the present disclosure. As shown in FIG. 4, the detection device 214 includes a determination unit 2141, a current generation unit 2142, and a drive unit 2143. Note that the detection device 214 may be implemented within an IC (Integrated Circuit).

[0021] The determination unit 2141 detects the voltage output by the capacitor 213 according to the charge accumulated by the current (an example of the first current) flowing through the capacitor 213. The determination unit 2141 determines whether the voltage output by the capacitor 213 exceeds a predetermined constant threshold value. Then, when the determination unit 2141 determines that the voltage output by the capacitor 213 exceeds the threshold value, it determines that the power semiconductor is short-circuited. That is, the determination unit 2141 determines that the power semiconductor is short-circuited when the potential at the second terminal of the detection device 214 exceeds the threshold value with respect to the ground terminal. When the drive unit 2143 does not output an on command to the power semiconductor, the second terminal of the detection device 214 is short-circuited to the ground terminal inside the detection device 214 so that the potential of the second terminal of the detection device 214 does not rise. Specific examples of the short circuit of the power semiconductor will be described later.

[0022] The current generation unit 2142 (an example of a voltage generation circuit) generates a current and causes the generated current to flow through the thermistor 203. Thereby, the protection circuits 20a and 20b generate a current (an example of the second current) having a magnitude corresponding to the information related to the temperature of the NMOSs 101 and 102 (an example of a power semiconductor) provided in the drive device 10 that drives the load 30. Then, the protection circuits 20a and 20b change the magnitude of the current flowing through the capacitor 213 based on the generated current.

[0023] For example, the current generation unit 2142 passes a constant current I through the thermistor 203 provided near the power semiconductor whose temperature changes. As a result, the protection circuits 20a and 20b generate a voltage Vt having temperature characteristics. Then, a current Iout that changes according to the voltage value is generated from the voltage Vt. This current Iout acts to prevent the charging of the capacitor 213 as shown in FIG. 3. Generally, the resistance value of the thermistor 203 decreases as the temperature rises. Therefore, as will be described in detail later, as the power semiconductor becomes hotter (i.e., as the thermistor 203 becomes hotter), the current Iout decreases. That is, the current that charges the capacitor 213 increases as the power semiconductor becomes hotter. As a result, the voltage applied to the capacitor 213 rises in a shorter time when the power semiconductor is hot than when it is cold. Since the threshold value used by the determination unit 2141 at the time of determination is a constant value, the determination unit 2141 can determine a short circuit earlier when the power semiconductor is hot than when it is cold.

[0024] Here, referring to FIG. 3, the current Iout is derived. Let the potential of the positive input terminal of the operational amplifier 201 be Vt. Also, let the potential of the positive input terminal of the operational amplifier 202 be V1. Also, let the potential of the output terminal of the operational amplifier 202 be V2. Also, let the potential of the second terminal of the detection device 214 be V3. Also, let the resistance values of the resistors 204, 205, 206, 207, 208, 209, 210, 211 be R1, R2, R3, R4, R5, R6, R7, R8, respectively. Also, let the resistance value of the thermistor 203 be Rt. Also, let the current flowing through the resistor 207 be I1. Also, let the current flowing through the resistor 209 be I2. Also, let the current flowing through the resistor 211 be I3.

[0025] The potential V1 of the positive input terminal of the operational amplifier 202 can be expressed by Equation (1).

[0026]

Equation

[0027] Since the potential of the non-inverting input terminal of the operational amplifier 202 is V1, considering virtual ground for the operational amplifier 202, the potential of the inverting input terminal of the operational amplifier 202 becomes V1. Therefore, Equation (2) holds for the current I1.

[0028]

Number

[0029] Since the current flowing through the resistor 208 is I1, the potential V2 can be expressed by Equation (3).

[0030]

Number

[0031] Also, the current I3 can be expressed by Equation (4).

[0032]

Number

[0033] Also, Equation (5) holds for the current I2.

[0034]

Number

[0035] The sum of the current I2 and the current I3 is the current Iout. Therefore, the current Iout can be expressed by Equation (6).

[0036]

Number

[0037] Here, if R4·(R7 + R8) = R5·R6, Equation (7) holds.

[0038]

Number

[0039] Here, the voltage Vt in Equation (7) is obtained by multiplying the constant current I output by the current generation unit 2142 by the resistance value Rt of the thermistor 203 having a temperature characteristic. Therefore, by adjusting so that R4·(R7 + R8)=R5·R6 holds, and adjusting the ratio of R5 to R4·R8 and the voltage Vt (that is, the current generated by the current generation unit 2142), the protection circuits 20a and 20b can generate a current Iout whose current value decreases as the power semiconductor becomes hot.

[0040] FIG. 5 is a diagram for explaining the effect of the current Iout in one embodiment of the present disclosure. Next, with reference to FIG. 5, the effect of the current Iout will be described. In FIG. 5, the horizontal axis represents the junction temperature or the thermistor temperature. The vertical axis represents time. The line (A) in FIG. 5 is the short-circuit withstand capacity, indicating that if the protection operation is not executed by this time, a problem will occur in the power semiconductor. The line (B) in FIG. 5 indicates the time required for the power semiconductor to switch. That is, when the protection circuit operates at a timing exceeding the line (A), a problem occurs in the power semiconductor, and when the protection circuit operates at a timing less than the line (B), since the switching of the power semiconductor is not completed, it is erroneously determined that there is a short circuit. Therefore, the timing for operating the protection circuit must be between the line (A) and the line (B). However, in a conventional protection circuit that operates when a certain condition is satisfied regardless of the temperature without using the current Iout, it is often set so that the protection circuit operates on a line (C) that is longer than the time required for switching at low temperatures shown in FIG. 5 and can ensure a margin with respect to the short-circuit withstand capacity. In this case, the difference between the line (A) and the line (B) becomes large at high temperatures, and although there is a situation where a margin can be provided with respect to the short-circuit withstand capacity at high temperatures, a margin cannot be provided.

[0041] On the one hand, in one embodiment of the present disclosure, by using the current Iout having temperature characteristics, it becomes possible to adjust the timing for operating the protection circuit as shown by line (D) in FIG. 5. Therefore, a margin can be provided for the short-circuit withstand at high temperatures.

[0042] The drive unit 2143 drives the power semiconductor (i.e., NMOS) of the drive device 10. For example, while turning on the NMOS, the drive unit 2143 outputs an on command to the gate of the NMOS. Also, while turning off the NMOS, the drive unit 2143 does not output an on command to the gate of the NMOS. That is, the drive unit 2143 outputs an on command to the gate of the NMOS only while the NMOS is in the on state.

[0043] (Operation of the protection circuit) Next, the operation of the protection circuits 20a and 20b according to one embodiment of the present disclosure will be described with reference to FIGS. 2 and 3. The protection circuits 20a and 20b according to one embodiment of the present disclosure are circuits that generate a voltage Vt having temperature characteristics by flowing the current I generated by the current generation unit 2142 through the thermistor 203, and generate a current Iout (a current having a magnitude according to information related to temperature) that changes according to the value of the voltage Vt, thereby changing the current for charging the capacitor 213 according to the temperature change of the power semiconductor and changing the charging time.

[0044] It is assumed that the voltage output by the power supply 40 is, for example, several hundred volts. Also, it is assumed that the voltage output by the power supply 50 is, for example, several tens of volts. That is, the voltage output by the power supply 40 is sufficiently larger than the voltage output by the power supply 50.

[0045] First, the operation of protection circuits 20a and 20b when NMOSs 101 and 102, which are power semiconductors, are not short-circuited together will be described. When NMOSs 101 and 102 shown in FIG. 2 are not short-circuited together, each of NMOSs 101 and 102 turns on when receiving an on command. In that case, the voltage applied between the source and drain of the on-state NMOS (NMOS101 or NMOS102) is a voltage (e.g., 1 volt) that is sufficiently lower than the voltage output by power supply 50. Therefore, diode 212 shown in FIG. 3 becomes forward-biased and conducts current. In this case, current flows from power supply 50 through diode 212 to the on-state NMOS (NMOS101 or NMOS102). As a result, when diode 212 is in the on state, the voltage between the anode of diode 212 and the ground terminal (terminal C) is the sum of the source-drain voltage in the linear region of the static characteristics of the NMOS (NMOS101 or NMOS102) and the forward voltage of diode 212. Note that the static characteristics in this case are the characteristics showing the relationship between the source-drain voltage and the drain current. Therefore, the current flowing through resistors 205 and 206 and capacitor 213 is smaller than when diode 212 is in the off state, and the potential at the second terminal of detection device 214 remains low. As a result, determination unit 2141 determines that the voltage output by capacitor 213 does not exceed the threshold value, that is, the power semiconductor is not short-circuited.

[0046] Next, the operation of the protection circuit 20a when the power semiconductor is short-circuited will be described. Here, the operation of the protection circuit 20a when the NMOS 102 is short-circuited will be described with reference to FIGS. 2 and 3. When the NMOS 102 shown in FIG. 2 is short-circuited, the potential of the ground terminal of the protection circuit 20a drops to the potential of the ground terminal of the protection circuit 20b. As a result, the voltage output by the power supply 40 is applied between the source and drain of the NMOS 101. Therefore, the diode 212 included in the protection circuit 20a is reverse-biased and does not conduct current. As a result, current flows through the resistors 205 and 206 and the capacitor 213. The current flowing at this time is a current having temperature characteristics depending on the current Iout as described above, and the current increases as the power semiconductor becomes hot. As a result, the voltage output by the capacitor 213 exceeds the threshold value earlier as the temperature rises. Therefore, the determination unit 2141 can detect a short circuit of the power semiconductor at an appropriate timing according to the temperature of the power semiconductor. Then, according to the timing when the determination unit 2141 detects a short circuit of the power semiconductor, the driving unit 2143 controls the NMOS (for example, stops outputting an on command), so that the protection circuit 20a can actually be operated and the load driving system 1 can be protected. Note that the operation of the protection circuit 20b when the NMOS 101 is short-circuited can be considered in the same manner in consideration of the symmetry of the circuit.

[0047] (Function, Effect) As described above, the load driving system 1 according to an embodiment of the present disclosure has been described. In the protection device 20 of the load driving system 1, the capacitor 213 outputs a voltage corresponding to the charge accumulated by the first current. Further, the protection circuits 20a and 20b determine whether or not the voltage output by the capacitor 213 exceeds a certain threshold value. The protection circuits 20a and 20b generate a second current (Iout) having a magnitude corresponding to information related to the temperature of the power semiconductors (NMOS 101 and 102) that drive the load 30, and change the magnitude of the first current based on the generated second current. By doing so, the protection device 20 can protect the load driving system 1 at an appropriate timing according to the temperature of the power semiconductors (NMOS101, 102).

[0048] In one embodiment of the present disclosure, the control of the switching of NMOS101 and 102 (i.e., the control of the voltage applied to the gates of NMOS101 and 102) has been described as being performed by the protection device 20. However, in another embodiment of the present disclosure, the control of the switching of NMOS101 and 102 may be performed by a control device (not shown).

[0049] In one embodiment of the present disclosure, the load driving system 1 has been described as having a temperature characteristic in the current Iout by utilizing the temperature characteristic of the thermistor 203. However, in another embodiment of the present disclosure, a temperature characteristic other than that of the thermistor 203 may be utilized to give the current Iout a temperature characteristic. For example, by utilizing the temperature characteristic of a diode provided near the power semiconductor, the current Iout may be given a temperature characteristic. Specifically, as shown in FIG. 6, by passing the constant current I generated by the current generation unit 2142 through the diode 215, the voltage Vt is given a temperature characteristic, and as a result, the current Iout may be given a temperature characteristic. Also, for example, temperature detection means using the temperature characteristic of a PN junction is provided near the power semiconductor, and the voltage corresponding to the detected temperature is AD-converted to generate a digital value of the voltage corresponding to the temperature. Using this digital value, as shown in FIG. 7, the current generation unit 2142 generates a current having a temperature characteristic, and by passing the generated current through the resistor 216, the voltage Vt may be given a temperature characteristic, or the first current may be directly given a temperature characteristic.

[0050] In another embodiment of the present disclosure, the protection device 20 may supply current to the power semiconductor from the second terminal of the detection device 214 via the diode 212 without passing through a resistor, for example, as shown in FIG. 7. And the current Iout may be used to give the current supplied to the power semiconductor temperature characteristics. Even when the protection device 20 supplies current to the power semiconductor from the second terminal of the detection device 214 via the diode 212 without passing through a resistor, the method of giving the current Iout temperature characteristics is not limited to the case where the current generation unit 2142 generates a current having temperature characteristics and causes the generated current to flow through the resistor 216, and any of the above-described methods may be used.

[0051] Note that, in the embodiments of the present disclosure, the order of the processes may be interchanged within the range where appropriate processes are performed.

[0052] Each of the storage unit and other storage devices in the embodiments of the present disclosure may be provided anywhere within the range where appropriate information transmission and reception are performed. Also, each of the storage unit and other storage devices may exist in plural and store data in a distributed manner within the range where appropriate information transmission and reception are performed.

[0053] Although the embodiments of the present disclosure have been described, the above-described protection device 20, detection device 214, and other control devices may have a computer system inside. And the processes described above are stored in a computer-readable recording medium in the form of a program, and the above processes are performed by the computer reading and executing this program. Specific examples of the computer are shown below.

[0054] FIG. 8 is a schematic block diagram showing the configuration of a computer according to at least one embodiment. As shown in FIG. 8, the computer 5 includes a CPU 6, a main memory 7, a storage 8, and an interface 9. For example, each of the above-described protection device 20, detection device 214, and other control devices is implemented in computer 5. The operations of the above-described respective processing units are stored in storage 8 in the form of a program. CPU 6 reads the program from storage 8, expands it in main memory 7, and executes the above processing according to the program. Further, CPU 6 secures a storage area corresponding to each of the above-described storage units in main memory 7 according to the program.

[0055] Examples of storage 8 include HDD (Hard Disk Drive), SSD (Solid State Drive), magnetic disk, magneto-optical disk, CD-ROM (Compact Disc Read Only Memory), DVD-ROM (Digital Versatile Disc Read Only Memory), semiconductor memory, and the like. Storage 8 may be an internal medium directly connected to the bus of computer 5, or may be an external medium connected to computer 5 via interface 9 or a communication line. Further, when this program is distributed to computer 5 via a communication line, computer 5 that has received the distribution may expand the program in main memory 7 and execute the above processing. In at least one embodiment, storage 8 is a non-transitory tangible storage medium.

[0056] Also, the above program may implement a part of the above-described functions. Further, the above program may be a file, so-called differential file (differential program), that can implement the above-described functions in combination with a program already recorded in the computer system.

[0057] In other embodiments, each of the protection device 20, the detection device 214, and the other control devices may include, in addition to or instead of the above configuration, a custom LSI (Large Scale Integrated Circuit) such as a PLD (Programmable Logic Device), an ASIC (Application Specific Integrated Circuit), a GPU (Graphics Processing Unit), and similar processing devices. Examples of PLDs include PAL (Programmable Array Logic), GAL (Generic Array Logic), CPLD (Complex Programmable Logic Device), and FPGA (Field Programmable Gate Array). In this case, some or all of the functions realized by the processor may be realized by the integrated circuit.

[0058] Although some embodiments of the present disclosure have been described, these embodiments are examples and do not limit the scope of the disclosure. Various additions, omissions, replacements, and changes may be made without departing from the gist of the disclosure.

[0059] <Appendix> The protection device 20, the load driving system 1 protection method, and the program described in each embodiment of the present disclosure are understood as follows, for example.

[0060] (1) The protection device (20) according to the first aspect includes a capacitor (213) that outputs a voltage according to the charge accumulated by the first current, determines whether the voltage output by the capacitor (213) exceeds a certain threshold value, and generates a second current (Iout) having a magnitude according to information related to the temperature of the power semiconductors (101, 102) that drive the load (30), and a protection circuit (20a, 20b) that changes the magnitude of the first current based on the generated second current (Iout).

[0061] This protection device (20) can detect a short circuit of the power semiconductors (101, 102) at a timing corresponding to the temperature of the power semiconductors (101, 102). As a result, the protection device (20) can protect the load driving system (1) at an appropriate timing according to the temperature of the power semiconductors (101, 102).

[0062] (2) The protection device (20) according to the second aspect is the protection device (20) of (1), wherein the protection circuits (20a, 20b) output an on command when turning on the power semiconductors (101, 102), and may stop outputting the on command when it is determined that the voltage output by the capacitor (213) exceeds the threshold value.

[0063] This protection device (20) can detect a short circuit of the power semiconductors (101, 102) at a timing corresponding to the temperature of the power semiconductors (101, 102). As a result, the protection device (20) can protect the load driving system (1) at an appropriate timing according to the temperature of the power semiconductors (101, 102).

[0064] (3) The protection device (20) according to the third aspect is the protection device (20) of (1) or (2), wherein the protection circuits (20a, 20b) include a current generation circuit that generates the second current, and the current generation circuit includes a voltage generation circuit (203, 215, 216, 2142) that generates a voltage whose value changes according to the temperature of the power semiconductors (101, 102), a first operational amplifier (201), a second operational amplifier (202), a first resistor (204), a second resistor (205), a third resistor (206), and a fourth resistor (207), and a fifth resistor (208). The non-inverting input terminal of the first operational amplifier (201) is connected to the voltage generation circuit (203, 215, 216, 2142), the inverting input terminal of the first operational amplifier (201) is connected to the output terminal of the first operational amplifier (201) and the first terminal of the first resistor (207), the non-inverting input terminal of the second operational amplifier (202) is connected to the first terminal of the third resistor (209) and the first terminal of the fourth resistor (210), the inverting input terminal of the second operational amplifier (202) is connected to the second terminal of the first resistor (207) and the first terminal of the second resistor (208), the output terminal of the second operational amplifier (202) is connected to the second terminal of the second resistor (208) and the first terminal of the fifth resistor (211), the second terminal of the fourth resistor (210) is connected to the second terminal of the fifth resistor (211) and the capacitor (213), and the second terminal of the third resistor (209) may be connected to the ground terminal.

[0065] With this protection device (20), it is possible to detect a short circuit of the power semiconductors (101, 102) at a timing according to the temperature of the power semiconductors (101, 102). As a result, the protection device (20) can protect the load driving system (1) at an appropriate timing according to the temperature of the power semiconductors (101, 102).

[0066] (4) The protection device (20) according to the fourth aspect is the protection device (20) of (3), wherein the voltage generation circuit (203, 2142) includes a thermistor (203) provided near the power semiconductor (101, 102) and a constant current source (2142), and when the current generated by the constant current source (2142) flows through the thermistor (203), the voltage generated in the thermistor (203) may be applied to the positive input terminal of the first operational amplifier (201).

[0067] With this protection device (20), a second current corresponding to the temperature characteristics of the thermistor (203) can be generated, and a short circuit of the power semiconductor (101, 102) can be detected at a timing corresponding to the temperature of the power semiconductor (101, 102). As a result, the protection device (20) can protect the load driving system (1) at an appropriate timing according to the temperature of the power semiconductor (101, 102).

[0068] (5) The protection device (20) according to the fifth aspect is the protection device (20) of (3), wherein the voltage generation circuit (215, 2142) includes a diode (215) provided near the power semiconductor (101, 102) and a constant current source (2142), and when the current generated by the constant current source (2142) flows through the diode (215), the voltage generated in the diode (215) may be applied to the positive input terminal of the first operational amplifier (201).

[0069] With this protection device (20), a second current corresponding to the temperature characteristics of the PN junction of the diode (215) can be generated, and a short circuit of the power semiconductor (101, 102) can be detected at a timing corresponding to the temperature of the power semiconductor (101, 102). As a result, the protection device (20) can protect the load driving system (1) at an appropriate timing according to the temperature of the power semiconductor (101, 102).

[0070] (6) The protection device (20) according to the sixth aspect is the protection device (20) of (3), wherein the voltage generation circuit (216, 2142) includes a current source (2142) that generates a current according to the temperature change of the power semiconductor (101, 102), and a sixth resistor (216). When the current generated by the current source (2142) flows through the sixth resistor (216), the voltage generated across the sixth resistor (216) may be applied to the positive input terminal of the first operational amplifier (201).

[0071] With this protection device (20), a second current can be generated by flowing a temperature-dependent current through the resistor (216), and a short circuit of the power semiconductor (101, 102) can be detected at a timing corresponding to the temperature of the power semiconductor (101, 102). As a result, the protection device (20) can protect the load driving system (1) at an appropriate timing according to the temperature of the power semiconductor (101, 102).

[0072] (7) The load driving system (1) according to the seventh aspect includes the protection device (20) of (1) to (6) and a driving device (10) including the power semiconductors (101, 102) to be protected by the protection device (20).

[0073] With this load driving system (1), a short circuit of the power semiconductors (101, 102) can be detected at a timing corresponding to the temperature of the power semiconductors (101, 102). As a result, the load driving system (1) can protect the load driving system (1) at an appropriate timing according to the temperature of the power semiconductors (101, 102).

[0074] (8) The protection method according to the eighth aspect includes outputting a voltage according to the charge accumulated by the first current, determining whether the output voltage exceeds a certain threshold value, generating a second current (Iout) having a magnitude corresponding to information related to the temperature of the power semiconductor (101, 102) that drives the load (30), and changing the magnitude of the first current based on the generated second current (Iout).

[0075] With this protection method, it is possible to detect a short circuit of the power semiconductors (101, 102) at a timing corresponding to the temperature of the power semiconductors (101, 102). As a result, the protection method can protect the load driving system (1) at an appropriate timing according to the temperature of the power semiconductors (101, 102).

[0076] (9) The program according to the ninth aspect causes a computer to output a voltage corresponding to the charge accumulated by the first current, determine whether the output voltage exceeds a certain threshold value, and generate a second current (Iout) having a magnitude corresponding to information related to the temperature of the power semiconductors (101, 102) that drive the load (30), and change the magnitude of the first current based on the generated second current (Iout).

[0077] With this program, it is possible to detect a short circuit of the power semiconductors (101, 102) at a timing corresponding to the temperature of the power semiconductors (101, 102). As a result, the program can protect the load driving system (1) at an appropriate timing according to the temperature of the power semiconductors (101, 102).

Description of Reference Numerals

[0078] 1 ··· Load driving system 5 ··· Computer 6 ··· CPU 7 ··· Main memory 8 ··· Storage 9 ··· Interface 10 ··· Driving device 20 ··· Protection device 20a, 20b ··· Protection circuit 30 ··· Load 40, 50 ··· Power supply 101, 102 ··· NMOS 201, 202 ··· Operational amplifier 203 ··· Thermistor 204, 205, 206, 207, 208, 209, 210, 211, 216 ··· Resistor 212, 215... Diodes 213... Capacitor 214... Detection device 2141... Judgment unit 2142... Current generation unit 2143... Driving unit

Claims

**Claim 1**: A protection device for protecting a power semiconductor that drives a load from a short circuit, comprising: a capacitor that outputs a voltage corresponding to the charge accumulated by a first current, which is a current that changes according to the presence or absence of a short circuit in the power semiconductor; a protection circuit that determines whether the voltage output by the capacitor exceeds a certain threshold value, generates a second current having a magnitude corresponding to information related to the temperature of the power semiconductor, and changes the magnitude of the first current based on the generated second current; and comprising: The protection circuit: comprises a current generation circuit that generates the second current; The current generation circuit: comprises a voltage generation circuit that generates a voltage whose value changes according to the temperature of the power semiconductor, a first operational amplifier, a second operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor; The non-inverting input terminal of the first operational amplifier is connected to the voltage generation circuit, the inverting input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier and the first terminal of the first resistor, the non-inverting input terminal of the second operational amplifier is connected to the first terminal of the third resistor and the first terminal of the fourth resistor, the inverting input terminal of the second operational amplifier is connected to the second terminal of the first resistor and the first terminal of the second resistor, the output terminal of the second operational amplifier is connected to the second terminal of the second resistor and the first terminal of the fifth resistor, the second terminal of the fourth resistor is connected to the second terminal of the fifth resistor and the capacitor, and the second terminal of the third resistor is connected to a ground terminal; A protection device. **Claim 2**: The protection circuit: outputs an on command when turning on the power semiconductor, and stops outputting the on command when it is determined that the voltage output by the capacitor exceeds the threshold value. The protection device according to claim 1. **Claim 3**: The voltage generation circuit: comprises a thermistor provided near the power semiconductor and a constant current source, and applies the voltage generated in the thermistor to the non-inverting input terminal of the first operational amplifier when the current generated by the constant current source flows through the thermistor. The protection device according to claim 1. **Claim 4**: The voltage generation circuit: comprises a diode provided near the power semiconductor and a constant current source, and applies the voltage generated in the diode to the non-inverting input terminal of the first operational amplifier when the current generated by the constant current source flows through the diode. The protection device according to claim 1.

5. The voltage generation circuit includes: a current source that generates a current corresponding to a temperature change of the power semiconductor, and a sixth resistor, and when the current generated by the current source flows through the sixth resistor, a voltage generated across the sixth resistor is applied to the non-inverting input terminal of the first operational amplifier. The protection device according to claim 1.

6. The protection device according to any one of claims 1 to 5, a drive device including the power semiconductor to be protected by the protection device, and a load drive system including the same.

7. A protection method executed by a protection device including a capacitor and a protection circuit for protecting a power semiconductor that drives a load from a short circuit, wherein the capacitor outputs a voltage corresponding to the charge accumulated by a first current that is a current that changes according to the presence or absence of a short circuit of the power semiconductor, the protection circuit determines whether or not the voltage output by the capacitor exceeds a certain threshold value, generates a second current having a magnitude corresponding to information related to the temperature of the power semiconductor, and changes the magnitude of the first current based on the generated second current, including: the protection circuit includes: a current generation circuit that generates the second current, the current generation circuit includes: a voltage generation circuit that generates a voltage whose value changes according to the temperature of the power semiconductor, a first operational amplifier, a second operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor, the non-inverting input terminal of the first operational amplifier is connected to the voltage generation circuit, the inverting input terminal of the first operational amplifier is connected to the output terminal of the first operational amplifier and the first terminal of the first resistor, the non-inverting input terminal of the second operational amplifier is connected to the first terminal of the third resistor and the first terminal of the fourth resistor, the inverting input terminal of the second operational amplifier is connected to the second terminal of the first resistor and the first terminal of the second resistor, the output terminal of the second operational amplifier is connected to the second terminal of the second resistor and the first terminal of the fifth resistor, the second terminal of the fourth resistor is connected to the second terminal of the fifth resistor and the capacitor, and the second terminal of the third resistor is connected to a ground terminal, a protection method.

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