Inrush current suppression circuit

Abstract

To detect a failure such as deposition in which a relay is kept in a closed state in an inrush current suppression circuit.SOLUTION: An inrush current suppression circuit 1 includes: a resistor, which is inserted into a path from a power source to a load, for suppressing an inrush current; a first relay, which is connected in parallel to the resistor, for turning on / turning off power supply from the power source to the load; a first temperature sensor for acquiring a temperature of the resistor; and a determination section for determining an abnormality of the first relay on the basis of the temperature acquired by the first temperature sensor while an OFF signal for turning off the first relay is inputted.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to an inrush current suppression circuit. [Background technology]

[0002] Conventionally, circuits that use a thermistor to suppress inrush current are known. For example, in Patent Document 1, a thermistor is used to suppress inrush current. Also, in Patent Document 1, a fault in which the relay contacts cannot be closed (so-called an open fault) is detected by a detection circuit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-099178 Summary of the Invention [Problem to be solved by the invention]

[0004] The technology described in Patent Document 1 can detect an open fault in which the relay remains open, but cannot detect a fault in which the relay remains closed, such as a welded relay.

[0005] The present invention has been made in view of the above, and an object of the present invention is to provide an inrush current suppression circuit that can detect a fault such as welding that causes the relay to remain closed. [Means for solving the problem]

[0006] An inrush current suppression circuit according to one aspect of the present disclosure includes a resistor inserted in a path from a power source to a load to suppress inrush current, a first relay connected in parallel to the resistor to turn on and off the power supply from the power source to the load, a first temperature sensor that acquires the temperature of the resistor, and a determination unit that determines an abnormality in the first relay based on the temperature acquired by the first temperature sensor when an off signal to turn off the first relay is input.

[0007] It is preferable that the determination unit determines that the first relay is abnormal if the temperature acquired by the first temperature sensor is rising when a signal to turn on the first relay is input.

[0008] It is preferable that the power supply further includes a second temperature sensor that detects the temperature around the first relay, and the determination unit corrects the temperature acquired by the first temperature sensor based on the temperature acquired by the second temperature sensor.

[0009] It is preferable that the power supply further includes a second relay connected in series to the first relay, and when the determination unit determines that the first relay is abnormal, the second relay turns on and off the power supply from the power source to the load instead of the first relay.

[0010] It is preferable that the determination unit has a memory unit that stores abnormality information indicating that the first relay is abnormal when the determination unit determines that the first relay is abnormal, and that the memory unit turns off the second relay when the abnormality information is stored.

[0011] It is preferable that the apparatus further includes an alarm unit that outputs an alarm when the determination unit determines that the first relay is abnormal. [Effects of the Invention]

[0012] According to the present disclosure, in an inrush current suppression circuit, a fault such as welding that causes a relay to remain closed can be detected. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a diagram showing the configuration of a first embodiment of an inrush current suppression circuit according to the present disclosure. [Figure 2] FIG. 2 is a diagram showing an example of the configuration of the control circuit in FIG. [Figure 3] FIG. 3 is a diagram illustrating the operation of the inrush current suppression circuit according to the first embodiment. [Figure 4] FIG. 4 is a diagram illustrating the operation of the inrush current suppression circuit according to the first embodiment. [Figure 5] FIG. 5 is a flowchart illustrating an example of the operation of the inrush current suppression circuit. [Figure 6] FIG. 6 is a diagram showing the configuration of a second embodiment of an inrush current suppression circuit according to the present disclosure. [Figure 7] FIG. 7 is a diagram showing an example of temperatures acquired by the temperature sensor. [Figure 8] FIG. 8 is a flowchart illustrating an example of the operation of the inrush current suppression circuit. [Figure 9] FIG. 9 is a diagram illustrating a configuration of a third embodiment of an inrush current suppression circuit according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the following description of each embodiment, components that are the same as or equivalent to those in other embodiments will be given the same reference numerals, and their description will be simplified or omitted. The present disclosure is not limited to each embodiment. Furthermore, the components of each embodiment include those that are easily replaceable by those skilled in the art, or those that are substantially the same. The configurations described below can be combined as appropriate. Omissions, substitutions, or modifications of the configurations can be made within the scope of the invention.

[0015] (First embodiment) (composition) Fig. 1 is a diagram showing the configuration of a first embodiment of an inrush current suppression circuit according to the present disclosure. In Fig. 1, an inrush current suppression circuit 1 of the first embodiment is provided between a power supply 9 and a load 6. The inrush current suppression circuit 1 suppresses inrush current when power input from the power supply 9 is supplied to the load 6. In this example, a fuse 2, a rectifier circuit 3, the inrush current suppression circuit 1, and a capacitor 5 are provided between the power supply 9 and the load 6, and the inrush current suppression circuit 1 is provided between the rectifier circuit 3 and the capacitor 5.

[0016] The fuse 2 is provided in series between the power supply 9 and the rectifier circuit 3. The fuse 2 melts when a large current flows, thereby protecting the inrush current suppression circuit.

[0017] The rectifier circuit 3 is configured by, for example, a diode bridge, and full-wave rectifies the AC voltage input from the power supply 9 and outputs the rectified voltage.

[0018] The inrush current suppression circuit 1 includes a thermistor 4, a relay 71, a temperature sensor 81, and a control circuit 10.

[0019] The thermistor 4 has a predetermined resistance value. The resistance value of the thermistor 4 decreases as the temperature increases. In other words, the thermistor 4 is generally called a "power thermistor" or "NTC (Negative Temperature Coefficient) thermistor," a thermistor whose resistance value decreases as the temperature increases. The thermistor 4 corresponds to the resistor of the present disclosure.

[0020] The relay 71 is connected in parallel to the thermistor 4. An on / off command 100a transmitted from the control circuit 10 turns on or off the current flowing through a coil (not shown) of the relay 71, causing the relay 71 to be in an on state (contacts closed) or an off state (contacts open). If the relay 71 is operating normally, it will be in an on state when an on signal is input by the on / off command 100a from the control circuit 10. If the relay 71 is operating normally, it will be in an off state when an off signal is input by the on / off command 100a from the control circuit 10. In other words, the relay 71 is in an on state when an on signal to turn it on is input, and is in an off state when an off signal to turn it off is input. The relay 71 corresponds to the first relay of the present disclosure.

[0021] The temperature sensor 81 acquires the temperature of the thermistor 4. The temperature sensor 81 is preferably installed in close contact with the thermistor 4. By placing the temperature sensor 81 in close contact with the thermistor 4, the temperature sensor 81 can acquire the temperature of the thermistor 4 accurately. A signal 810 corresponding to the temperature of the thermistor 4 acquired by the temperature sensor 81 is input to the control circuit 10. The temperature sensor 81 corresponds to the first temperature sensor of the present disclosure.

[0022] The capacitor 5 is connected in parallel to the load 6. The capacitor 5 is, for example, an electrolytic capacitor. The capacitor 5 is charged and discharged by the full-wave rectified output from the rectifier circuit 3. Therefore, a DC voltage or a voltage close to DC is applied to the load 6.

[0023] The load 6 is, for example, but is not limited to, an electric motor. It may be any other power device that uses smoothed DC current. When the load 6 is an electric motor, the entire configuration of FIG. 1 can be said to be an AC motor. The load 6 may also include an inverter.

[0024] (Control circuit) Fig. 2 is a diagram showing an example of the configuration of the control circuit 10 in Fig. 1. In Fig. 2, the control circuit 10 includes a determination unit 11, an input / output unit 12, a storage unit 13, an alarm unit 14, a control unit 15, and an internal bus 16.

[0025] The determining unit 11 determines whether the relay 71 is normal or abnormal based on a signal 810 corresponding to the temperature of the thermistor 4 acquired by the temperature sensor 81.

[0026] The input / output unit 12 is an interface for transmitting and receiving signals between the control circuit 10 and other units. The input / output unit 12 receives temperature information from the temperature sensor 81. The input / output unit 12 outputs an on / off command 100a to the relay 71.

[0027] The storage unit 13 stores programs and data necessary for the operation of the control circuit 10. The storage unit 13 stores temperature information acquired by the temperature sensor 81, for example.

[0028] The alarm unit 14 outputs an alarm signal 101 based on the determination result by the determination unit 11. The alarm signal 101 is sent to a higher-level device (not shown), which can prevent the device from being powered on again.

[0029] The control unit 15 realizes a predetermined operation by reading and executing a program stored in the storage unit 13. The control unit 15 controls each unit in the control circuit 10. The control unit 15 can store temperature information in the storage unit 13. The control unit 15 can read out the temperature information stored in the storage unit 13.

[0030] The internal bus 16 interconnects the various components within the control circuit 10. The various components within the control circuit 10 can exchange signals via the internal bus 16.

[0031] (operation) 1 functions as a power conversion circuit that rectifies and smoothes AC power supplied from a power source 9 and supplies the rectified power to a load 6.

[0032] The relay 71 is placed in a state where the contacts are closed (i.e., an ON state) or a state where the contacts are open (i.e., an OFF state) in response to an ON / OFF command 100a from the control circuit 10. When the relay 71 is in the OFF state, the relay 71 does not pass current. Therefore, current flows through the thermistor 4 connected in parallel to the relay 71.

[0033] On the other hand, when the relay 71 is in the on state, a current flows through the parallel circuit of the thermistor 4 and the relay 71. When the relay 71 is in the on state, most of the current flows through the relay 71, and only a small amount of current flows through the thermistor 4.

[0034] 3 and 4 are diagrams illustrating the operation of the inrush current suppression circuit 1 according to the first embodiment. Fig. 3 is a diagram illustrating an example of the operation of the inrush current suppression circuit 1 when the relay 71 is operating normally. In Fig. 3, the horizontal axis represents time and the vertical axis represents temperature. Line S1 in Fig. 3 shows changes in temperature information acquired by the temperature sensor 81.

[0035] In this example, if relay 71 is in the on state from time t1 to time t2, the temperature information acquired by temperature sensor 81 remains constant without change. That is, current flows through relay 71 in the on state, but no current flows through the thermistor 4, so the temperature of the thermistor 4 does not rise.

[0036] Thereafter, at time t2, relay 71 changes from the ON state to the OFF state in response to ON / OFF command 100a. If relay 71 remains in the OFF state from time t2 to time t4, the temperature information acquired by temperature sensor 81 increases. That is, no current flows through relay 71 in the OFF state, but current flows through the thermistor 4, causing the temperature of the thermistor 4 to increase. The temperature of the thermistor 4 is acquired by temperature sensor 81 up to a predetermined temperature value.

[0037] After that, at time t5, when relay 71 changes from the OFF state to the ON state, current flows through relay 71 but not through the thermistor 4, so the temperature of thermistor 4 does not rise but begins to drop. After that, at time t7, relay 71 turns OFF, and the temperature of thermistor 4 stops dropping.

[0038] 4 is a diagram illustrating the operation of the inrush current suppression circuit 1 when the operation of the relay 71 is abnormal. In FIG. 4, the horizontal axis represents time and the vertical axis represents temperature. Line S2 in FIG. 4 represents temperature information acquired by the temperature sensor 81.

[0039] If an abnormality occurs in which the contacts of relay 71 remain closed, such as welding, relay 71 cannot be turned on or off by on / off command 100a sent from control circuit 10, and relay 71 remains on. Therefore, even if an attempt is made to turn relay 71 off by on / off command 100a at time t2, relay 71 remains on. As a result, current flows through relay 71 but not through thermistor 4, and the temperature information of thermistor 4 acquired by temperature sensor 81 does not increase. Thereafter, relay 71 remains on at times t5 and t7, and the temperature information of thermistor 4 acquired by temperature sensor 81 does not increase.

[0040] Relay welding occurs due to chattering, i.e., repeated on-off switching. Chattering occurs when the voltage that operates the relay coil becomes unstable. Relay welding can also occur if, for some reason, a current greater than the rated current flows through the relay.

[0041] Fig. 5 is a flowchart illustrating an example of the operation of the inrush current suppression circuit 1. Fig. 5 mainly shows the content of the processing by the control circuit 10. In this example, the case of a device having a normal operation mode and a determination operation mode will be described.

[0042] 5, first, power is applied to a device including the inrush current suppression circuit 1 (step S101). When power is applied, the thermistor 4 suppresses the inrush current. As described above, the resistance value of the thermistor 4 decreases as the temperature rises. After a predetermined time, the relay 71 is turned on (step S102), and the temperature sensor 81 acquires the temperature of the thermistor 4 (step S103). The control unit 15 stores the acquired temperature information in the memory unit 13 (step S105).

[0043] Thereafter, it is determined whether or not the normal operation of the device including the inrush current suppression circuit 1 has ended (step S106). If the normal operation has not ended, the process returns to step S103 (No in step S106), and acquisition of the temperature of the thermistor 4 continues (step S103).

[0044] On the other hand, if normal operation has ended in step S106 (Yes in step S106), the process proceeds to a determination operation mode (step S107). In the determination operation mode, first, relay 71 is turned off (step S108), and the temperature of thermistor 4 is acquired by temperature sensor 81 (step S109). The temperature of thermistor 4 acquired in step S109 is compared with the temperature information stored in memory unit 13 (step S112), and it is determined whether the temperature has increased (step S113).

[0045] In step S113, if the comparison result shows that the temperature has risen compared to the temperature acquired in the normal operation mode (Yes in step S113), it is determined that there is no abnormality in relay 71 (step S114), and the process ends.

[0046] On the other hand, if the comparison result in step S113 shows that the temperature has not risen compared to the temperature acquired in the normal operation mode (No in step S113), abnormality information indicating that relay 71 is abnormal is stored in storage unit 13 (step S115). Then, alarm unit 14 outputs alarm signal 101 (step S116), and the process ends.

[0047] As described above, in the determination operation mode, if the temperature rises even when the relay 71 is turned off, it can be determined that an abnormality that cannot be turned off, such as welding, has occurred in the relay 71. Therefore, an alarm signal 101 is output so that power is not turned on via the relay 71 in which the abnormality has occurred.

[0048] If power is turned on when an abnormality that cannot be turned off occurs in relay 71, a large inrush current may occur. As described above, outputting alarm signal 101 prevents power from being turned on. If power is turned on again while the relay is still welded, the inrush current suppression circuit may not function, which may lead to the fuse blowing or damage to the electrolytic capacitor. To avoid such an event, if an abnormality such as relay welding is determined, this is stored in memory unit 13 and alarm signal 101 is output. This prevents deterioration or damage to the fuse, electrolytic capacitor, etc. due to the inrush current caused by relay welding when power is turned on again, and the equipment can be quickly restored by simply replacing the relay.

[0049] Although the above description has been given for a device having a normal operation mode and a judgment operation mode, it is also possible to have a device that does not have such modes, and to acquire the temperature of thermistor 4 while relay 71 is on, and perform the processing from step S107 onwards at any timing.

[0050] (Second embodiment) (composition) Fig. 6 is a diagram showing the configuration of a second embodiment of the inrush current suppression circuit of the present disclosure. In Fig. 6, the inrush current suppression circuit 1a of the second embodiment is configured by adding a temperature sensor 82 to the inrush current suppression circuit 1 of the first embodiment. The temperature sensor 82 acquires the temperature at a position distant from the thermistor 4, i.e., the temperature around the thermistor 4. A signal 820 corresponding to the ambient temperature acquired by the temperature sensor 82 is input to the control circuit 10. The temperature sensor 82 corresponds to the second temperature sensor of the present disclosure.

[0051] (operation) In the normal operation mode, the inrush current suppression circuit 1a acquires the temperature of the thermistor 4 using the temperature sensor 81 and stores it in the memory unit 13, and also acquires the ambient temperature using the temperature sensor 82 and stores it in the memory unit 13. Then, in the judgment operation mode, the temperature information stored in the memory unit 13 is used.

[0052] Fig. 7 is a diagram showing an example of temperatures acquired by the temperature sensor 82. Fig. 7 shows changes in temperature. The horizontal axis of Fig. 7 represents time, and the vertical axis represents temperature. The solid line S11 in Fig. 7 shows an example of temperatures acquired by the temperature sensor 82 at an air temperature of 25°C.

[0053] In this example, if relay 71 is in the ON state from time t1 to time t2, the ambient temperature information acquired by temperature sensor 82 remains constant and does not change. That is, because current flows through relay 71 in the ON state and no current flows through the thermistor 4, the temperature around the thermistor 4 does not rise and the ambient temperature information does not change.

[0054] Thereafter, at time t2, relay 71 changes from the ON state to the OFF state in response to ON / OFF command 100a. If relay 71 remains in the OFF state from time t2 to time t4, the ambient temperature information acquired by temperature sensor 82 will rise. That is, no current flows through relay 71 in the OFF state, but current flows through the thermistor 4, causing the temperature of the thermistor 4 to rise, and the ambient temperature will also rise.

[0055] When relay 71 changes from the OFF state to the ON state at time t5, current flows through relay 71 but not through the thermistor 4, so the temperature of thermistor 4 and the surrounding temperature begin to drop. After that, at time t7, relay 71 turns OFF, and the temperature of thermistor 4 stops dropping, and the surrounding temperature also stops dropping.

[0056] 7, the dashed-dotted line S21 indicates an example of the temperature acquired by the temperature sensor 82 at an ambient temperature of 30°C. The temperature also changes for the dashed-dotted line S21 in the same way as for the solid line S11. That is, whether the ambient temperature is relatively low (i.e., in the case of the solid line S11) or relatively high (i.e., in the case of the dashed-dotted line S21), the ambient temperature information acquired by the temperature sensor 82 changes in response to changes in the temperature of the thermistor 4. Therefore, if the temperature information acquired by the temperature sensor 81 is corrected based on the temperature information acquired by the temperature sensor 82, a more accurate temperature can be determined. Specifically, the influence of the ambient temperature can be eliminated by calculating the difference between the temperature acquired by the temperature sensor 82 and the stored temperature acquired by the temperature sensor 82 and subtracting this difference from the temperature acquired by the temperature sensor 81. That is, the temperature information acquired by the temperature sensor 81 is corrected based on the temperature information acquired by the temperature sensor 82. This allows a more accurate temperature to be determined.

[0057] The temperature sensor 81 is a necessary component for acquiring the temperature of the thermistor 4. In contrast, the temperature sensor 82 is an optional component that is provided to improve the accuracy of temperature detection.

[0058] 8 is a flowchart illustrating an example of the operation of the inrush current prevention circuit 1a. In the processing by the inrush current prevention circuit 1a of the second embodiment, steps S104, S110, and S111 are added, unlike the case of FIG. 5 described above.

[0059] 8, after the temperature of thermistor 4 is acquired by temperature sensor 81 in step S103, the ambient temperature is acquired by temperature sensor 82 (step S104). The temperatures acquired by temperature sensor 81 and temperature sensor 82 are stored in storage unit 13 (step S105).

[0060] Furthermore, in step S109, the temperature of the thermistor 4 is acquired by temperature sensor 81, and then the ambient temperature is acquired by temperature sensor 82 (step S110). Then, the difference between the temperature acquired by temperature sensor 82 and the temperature stored in step S105 is subtracted from the temperature acquired by temperature sensor 81 (step S111). In this way, the temperature acquired by temperature sensor 81 is corrected based on the ambient temperature acquired by temperature sensor 82. The temperature corrected in step S111 is compared with the stored temperature information (step S112), and it is determined whether the temperature has risen (step S113).

[0061] The operations from step S113 onwards are the same as those of the first embodiment described with reference to Fig. 5. That is, in step S113, if the comparison result shows that the temperature has risen compared to the temperature acquired in the normal operation mode (Yes in step S113), it is determined that there is no abnormality in relay 71 (step S114), and the process ends.

[0062] On the other hand, if the comparison result in step S113 shows that the temperature has not risen compared to the temperature acquired in the normal operation mode (No in step S113), the fact that relay 71 is abnormal is stored in memory unit 13 (step S115), and alarm unit 14 outputs alarm signal 101 (step S116).

[0063] As described above, according to this embodiment, it is possible to correct the influence of the ambient temperature. That is, even if a temperature rise can be detected from the temperature acquired by temperature sensor 81, which is the first temperature sensor, it may be difficult to distinguish whether the cause of the rise is a rise in the ambient temperature or a relay malfunction. Even in such a case, it is possible to correctly detect a relay malfunction by correcting the temperature acquired by temperature sensor 81 using the ambient temperature acquired by temperature sensor 82, which is the second temperature sensor, as described above.

[0064] (Third embodiment) (composition) Fig. 9 is a diagram showing the configuration of a third embodiment of the inrush current suppression circuit of the present disclosure. In Fig. 6, the inrush current suppression circuit 1b of the third embodiment has a configuration in which a relay 72 is added to the inrush current suppression circuit 1a of the second embodiment. The relay 72 is connected in series to the relay 71. The series circuit of the relay 71 and the relay 72 is connected in parallel to the thermistor 4. The relay 72 corresponds to the second relay of the present disclosure.

[0065] The control circuit 10 of this embodiment outputs on / off commands 100a and 100b. The on / off command 100a transmitted from the control circuit 10 turns the relay 71 on or off. If the relay 71 is operating normally, it turns on when an on signal is input by the on / off command 100a from the control circuit 10. If the relay 71 is operating normally, it turns off when an off signal is input by the on / off command 100a from the control circuit 10.

[0066] Furthermore, the relay 72 is turned on or off in response to an on / off command 100b sent from the control circuit 10. If the relay 72 is operating normally, it will be turned on when an on signal is input by the on / off command 100b from the control circuit 10. If the relay 72 is operating normally, it will be turned off when an off signal is input by the on / off command 100b from the control circuit 10.

[0067] (operation) In the inrush current suppression circuit 1b, the relay 71 and the relay 72 are used alternatively. When the relay 71 is used, the relay 72 is kept in the ON state. In this state, by performing the same operation as in the first embodiment, it is possible to determine whether or not an abnormality has occurred in which the contacts of the relay 71 remain in the closed state, such as welding. Furthermore, when the relay 72 is used, the relay 71 is kept in the ON state. In this state, by performing the same operation as in the first embodiment, it is possible to determine whether or not an abnormality has occurred in which the contacts of the relay 72 remain in the closed state, such as welding.

[0068] If it is determined that an abnormality such as welding has occurred in relay 71 while it is in use, relay 72 can be used instead of relay 71, which remains closed, allowing the device to continue operating. In the first and second embodiments, if an abnormality in relay 71 is detected, alarm signal 101 is output, and the entire device becomes unusable thereafter. On the other hand, in this embodiment, relay 71 continues to be used in the on state, and thereafter relay 72 is used to turn relay 71 on and off, allowing the device to continue operating. Note that in this embodiment, two relays 71 and 72 are connected in series, but three or more relays may be connected in series and used alternatively.

[0069] With respect to the claims, the present disclosure may take the following forms. (1) a resistor inserted in a path from the power supply to the load to suppress inrush current; a first relay connected in parallel to the resistor for turning on and off the power supply from the power source to the load; a first temperature sensor that acquires the temperature of the resistor; a determination unit that determines whether the first relay has an abnormality based on the temperature acquired by the first temperature sensor when an OFF signal for turning off the first relay is input; An inrush current suppression circuit including: (2) The determination unit When a signal for turning on the first relay is input, if the temperature acquired by the first temperature sensor increases, it is determined that the first relay is abnormal. The inrush current suppression circuit according to (1). (3) a second temperature sensor for detecting a temperature around the first relay; The determination unit The temperature acquired by the first temperature sensor is corrected based on the temperature acquired by the second temperature sensor. An inrush current suppression circuit according to (1) or (2). (4) further comprising a second relay connected in series with the first relay; When the determination unit determines that the first relay is abnormal, the second relay turns on and off the power supply from the power source to the load instead of the first relay. An inrush current suppression circuit according to any one of (1) to (3). (5) a storage unit that stores abnormality information indicating that the first relay is abnormal when the determination unit determines that the first relay is abnormal; and a storage unit that turns off the second relay when the abnormality information is stored in the storage unit. (4) An inrush current suppression circuit according to the present invention. (6) The control unit further includes an alarm unit that outputs an alarm when the determination unit determines that the first relay is abnormal. An inrush current suppression circuit according to any one of (1) to (5). [Explanation of symbols]

[0070] 1, 1a, 1b Inrush current suppression circuit 2 fuses 3 Rectifier circuit 4 Thermistor 5. Capacitors 6 Load 9 Power supply 10 Control circuit 11 Judgment section 12 Input / output section 13 Storage section 14 Alarm section 15 Control Unit 16 Internal Bus 71 and 72 Relays 81, 82 Temperature sensors

Claims

1. a resistor inserted in a path from the power supply to the load to suppress inrush current; a first relay connected in parallel to the resistor for turning on and off the power supply from the power source to the load; a first temperature sensor for acquiring a temperature of the resistor; a determination unit that determines whether the first relay has an abnormality based on the temperature acquired by the first temperature sensor when an OFF signal for turning off the first relay is input; An inrush current suppression circuit including:

2. The determination unit When a signal for turning on the first relay is input, if the temperature acquired by the first temperature sensor increases, it is determined that the first relay is abnormal.

2. The inrush current suppression circuit according to claim 1.

3. a second temperature sensor for detecting a temperature around the first relay; The determination unit The temperature acquired by the first temperature sensor is corrected based on the temperature acquired by the second temperature sensor.

3. The inrush current suppression circuit according to claim 1.

4. further comprising a second relay connected in series with the first relay; When the determination unit determines that the first relay is abnormal, the second relay turns on and off the power supply from the power source to the load instead of the first relay.

3. The inrush current suppression circuit according to claim 1.

5. a storage unit that stores abnormality information indicating that the first relay is abnormal when the determination unit determines that the first relay is abnormal; and turns off the second relay when the storage unit stores the abnormality information.

5. The inrush current suppression circuit according to claim 4.

6. The control unit further includes an alarm unit that outputs an alarm when the determination unit determines that the first relay is abnormal.

3. The inrush current suppression circuit according to claim 1.

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