Charger for electric vehicle

Abstract

To enable an operation permission prohibition signal on an electric vehicle side to be surely detected in a charger for an electric vehicle.SOLUTION: When an operation permission prohibition switch 6 of an electric vehicle is on, a current flows from a power source of a charger through an operation permission prohibition line 2. A voltage change detection part 20 outputs a signal corresponding to a voltage of a node a of a limiting resistor 4 to an output node b. In a photocoupler 1, an anode of a light-emitting diode is connected to a power source, and the cathode is connected to the output node b. In the voltage change detection part 20, at least one reference voltage is set, the voltage of the node a is compared with the reference voltage, and the output node b is set in high impedance or low is output to the output node b according to a comparison result.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a charger for an electric vehicle. [Background technology]

[0002] In recent years, electric vehicles (EVs) have become popular as a way to reduce carbon dioxide emissions from automobiles. Electric vehicles are equipped with large-capacity storage batteries that store the electricity used when driving. The storage batteries of electric vehicles are charged by a charger. The charger's connector is connected to a charging port provided on the electric vehicle, and the charger charges the storage battery installed in the electric vehicle.

[0003] The CHAdeMO Association has established the standard specifications for electric vehicle quick charging stations, CHAdeMO 1.0.1 (hereinafter referred to as the CHAdeMO specifications). CHAdeMO (registered trademark) is a DC quick charging standard for EVs, and provides a unified interface between EVs and quick chargers globally.

[0004] Patent Document 1 discloses a charging system that uses an interface configuration between a charger and an electric vehicle that complies with the CHAdeMO specifications. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-85898 A (Fig. 2,

[0040] ) Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, FIG. 2 shows a sequence circuit shown in the CHAdeMO specification, and this sequence circuit includes a circuit configuration in which the charging / discharging device receives a charging permission signal from the vehicle via an operation permission / prohibition line.

[0007] FIG. 5 shows the circuit configuration (operation permission / prohibition signal circuit) described above. This operation permission / prohibition signal circuit detects the vehicle-side operation permission / prohibition signal (corresponding to the charging permission signal in Patent Document 1) based on the current flowing through the operation permission / prohibition line. Specifically, the ON / OFF state of switch "k" on the vehicle side is transmitted to the light-receiving transistor of photocoupler "j" on the charger side. When switch "k" is ON, current flows from the charger's power supply to switch "k" via limiting resistors R2 and R4. At this time, the voltage at point a drops. On the other hand, when switch "k" is OFF, no current flows, so the voltage at point a does not drop. The operation permission / prohibition line is provided in a connector connected to the charging port of the electric vehicle.

[0008] However, the CHAdeMO specification allows leakage current when switch "k" is OFF. Therefore, even when switch "k" is OFF, leakage current flows through switch "k", causing the voltage at point a to drop. This may result in the ON / OFF state of switch "k" being misrecognized.

[0009] The CHAdeMO specifications also specify the range of power supply voltage for chargers. It is desirable to stop charging when the charger's power supply voltage deviates from this specified voltage range. However, with the sequence circuit configuration shown in Figure 5, the operation permission / prohibition signal circuit may enter a normal judgment state even when the charger's power supply voltage deviates from the specified voltage range. This can lead to the problem of the charger continuing charging even when the power supply voltage is abnormal.

[0010] An object of the present invention is to enable an electric vehicle charger to reliably detect an operation permission / prohibition signal from the vehicle side. [Means for solving the problem]

[0011] In one aspect of the present invention, a charger that charges a storage battery of an electric vehicle includes an operation enable / disable line provided on a connector that is connected to a charging port of the electric vehicle; a limiting resistor having one end connected to a power source and the other end connected to the operation enable / disable line; a voltage change detection unit that receives a first voltage that is the voltage at the other end of the limiting resistor and outputs a signal corresponding to the first voltage to an output node; and a photocoupler that has a light-emitting diode and a light-receiving transistor, the anode of the light-emitting diode being connected to a power source and the cathode being connected to the output node; when the connector is connected to the charging port of the electric vehicle, the operation enable / disable line is connected to an operation enable / disable switch that the electric vehicle has; and when the operation enable / disable switch is on, current flows from the power source of the charger through the operation enable / disable line, and the voltage change detection unit has at least one reference voltage set thereto, compares the first voltage with the at least one reference voltage, and sets the output node to high impedance or outputs a low signal to the output node depending on the comparison result.

[0012] According to this configuration, a voltage change detection unit is provided that receives a first voltage, which is the voltage at the other end of the limiting resistor, and outputs a signal corresponding to the first voltage to an output node. The voltage change detection unit is set to at least one reference voltage, compares the first voltage with the reference voltage, and sets the output node to high impedance or low depending on the comparison result. When the voltage change detection unit outputs a low signal to the output node, current flows through the photocoupler, and when the voltage change detection unit sets the output node to high impedance, no current flows through the photocoupler. Here, when the operation enable / disable switch of the electric vehicle is on, the first voltage decreases due to a voltage drop across the limiting resistor. On the other hand, when the operation enable / disable switch is off, the first voltage does not decrease as much as when it is on, but it does decrease slightly due to leakage current through the operation enable / disable switch. Therefore, by setting the reference voltage in the voltage change detection unit to a voltage that takes into account the leakage current through the operation enable / disable switch, it is possible to avoid erroneously recognizing the operation enable / disable switch as on when it is off. Therefore, the operation enable / disable signal of the electric vehicle can be reliably detected by the on / off switching of the photocoupler.

[0013] In the above aspect, the voltage change detection unit has a lower reference voltage and an upper reference voltage set, the upper reference voltage is set to the upper limit of a predetermined voltage range, and the lower reference voltage is set to a voltage obtained by subtracting the voltage drop in the limiting resistor due to leakage current of the operation enable / disable switch from the lower limit of the predetermined voltage range, and when the first voltage is between the lower reference voltage and the upper reference voltage, the output node is set to high impedance, and when the first voltage is lower than the lower reference voltage or higher than the upper reference voltage, a low signal is output to the output node.

[0014] With this configuration, the lower reference voltage in the voltage change detection unit is set to a voltage obtained by subtracting the voltage drop across the limiting resistor due to leakage current from the operation enable / disable switch from the lower limit of the predetermined voltage range. Therefore, when the operation enable / disable switch is off, even if the first voltage drops slightly due to leakage current, the output node is set to high impedance. This prevents the photocoupler from being erroneously turned on.

[0015] Furthermore, when the operation enable / disable switch is off, if the charger's power supply voltage is too low and is lower than the lower reference voltage, or too high and is higher than the upper reference voltage, the voltage change detection unit outputs a low signal to the output node, which turns on the photocoupler, making it possible to detect abnormalities in the charger's power supply voltage.

[0016] Furthermore, in the above aspect, the voltage change detection unit may include first, second, and third reference voltage resistors connected in series between a stabilized power supply and ground, a first comparator having a positive input terminal connected to a connection node between the first reference voltage resistor and the second reference voltage resistor and a negative input terminal receiving the first voltage, and a second comparator having a positive input terminal receiving the first voltage and a negative input terminal connected to the connection node between the second reference voltage resistor and the third reference voltage resistor, and the output terminals of the first and second comparators are connected to the output node.

[0017] This allows the voltage change detector to set the voltage between the first reference voltage resistor and the second reference voltage resistor to the upper reference voltage, and the voltage between the second reference voltage resistor and the third reference voltage resistor to the lower reference voltage.

[0018] In addition, in the above aspect, the specified voltage range may be the range of power supply voltages of the charger specified in the CHAdeMO specifications, and the lower reference voltage may be a voltage obtained by subtracting from the lower limit of the specified voltage range the voltage drop in the limiting resistor due to the maximum leakage current of the operation enable / disable switch specified in the CHAdeMO specifications.

[0019] Alternatively, in the above aspect, the voltage change detection unit may have a reference voltage set to a voltage obtained by subtracting a predetermined voltage from a power supply voltage of the electric vehicle charger, the predetermined voltage being smaller than the voltage drop across the limiting resistor when the operation enable / disable switch is on and larger than the voltage drop across the limiting resistor due to a leakage current of the operation enable / disable switch, and may set the output node to high impedance when the first voltage is higher than the reference voltage, and may output a low signal to the output node when the first voltage is lower than the reference voltage.

[0020] According to this configuration, the reference voltage in the voltage change detection unit is set to a voltage obtained by subtracting a predetermined voltage from the power supply voltage of the electric vehicle charger. The predetermined voltage is smaller than the voltage drop across the limiting resistor when the activation enable / disable switch is on, but is larger than the voltage drop across the limiting resistor due to leakage current from the activation enable / disable switch. Therefore, when the activation enable / disable switch is off, even if the first voltage drops slightly due to leakage current, the output node is set to high impedance. This prevents the photocoupler from being erroneously turned on. [Effects of the Invention]

[0021] According to the present invention, an electric vehicle charger can reliably detect an operation permission / prohibition signal from the vehicle, and can also detect when the power supply voltage of the charger deviates from a specified voltage range. [Brief explanation of the drawings]

[0022] [Figure 1] Circuit configuration related to the operation permission / prohibition line in the electric vehicle charger according to the embodiment [Figure 2] A diagram for explaining the operation when the operation enable / disable switch is off [Figure 3] A diagram to explain the operation when the operation enable / disable switch is on [Figure 4]Circuit configuration related to an operation permission / prohibition line in an electric vehicle charger according to another example [Figure 5] Circuit configuration related to the operation enable / disable signal circuit extracted from the CHAdeMO specifications DETAILED DESCRIPTION OF THE INVENTION

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the accompanying drawings. The following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present invention, its scope of application, or its uses.

[0024] (Embodiment) Figure 1 shows the circuit configuration of an electric vehicle charger according to an embodiment. Figure 1 shows only the configuration related to the operation permission / prohibition line, and other configurations are omitted from the illustration. An electric vehicle charger (hereinafter simply referred to as a charger, as appropriate) connects a connector (not shown) to a charging port provided on an electric vehicle, and charges a storage battery mounted on the electric vehicle.

[0025] <Configuration> An electric vehicle is provided with a limiting resistor 5 and an operation enable / disable switch 6. Note that the limiting resistor 5 may not be provided. In a charger, an operation enable / disable line 2 is provided in the connector. One end of the limiting resistor 4 is connected to a power source (e.g., 12 V), and the other end is connected to the operation enable / disable line 2. When the connector is connected to the charging port of the electric vehicle, the operation enable / disable line 2 is connected to the operation enable / disable switch 6 of the electric vehicle. When the operation enable / disable switch 6 is on, current flows from the charger's power source to the operation enable / disable switch 6 via the operation enable / disable line 2. When the operation enable / disable switch 6 is off, no current flows in the operation enable / disable line 2. When the operation enable / disable switch 6 is on, the voltage of node a on the other end of the limiting resistor 4 drops significantly due to a voltage drop in the limiting resistor 4 caused by the current flowing through the operation enable / disable line 2.

[0026] The voltage change detection unit 20 receives the voltage at node a on the other end of the limiting resistor 4, and outputs a signal corresponding to the voltage at node a to output node b. Hi-Z (high impedance) or Low is output to output node b. An upper reference voltage and a lower reference voltage are set in the voltage change detection unit 20. When the voltage at node a is between the lower reference voltage and the upper reference voltage, the voltage change detection unit 20 sets output node b to Hi-Z. When the voltage at node a is lower than the lower reference voltage or higher than the upper reference voltage, it outputs Low to the output node. The configuration of the voltage change detection unit 20 will be described in detail later.

[0027] The photocoupler 1 has a light-emitting diode and a light-receiving transistor. The anode of the light-emitting diode is connected to a power supply via a limiting resistor 12. The cathode of the light-emitting diode is connected to an output node b of the voltage change detection unit 20. When Hi-Z is output to the output node b, the photocoupler 1 is turned off. When Low is output to the output node b, the photocoupler 1 is turned on. A parallel resistor 3 is provided to prevent malfunction of the photocoupler 1. Note that the parallel resistor 3 is not necessarily provided.

[0028] The configuration of voltage change detection unit 20 will be described. Voltage change detection unit 20 includes reference voltage resistors 9, 10, and 11 connected in series between stabilized power supply 15 and ground, and comparators 7 and 8. Comparator 7 has a positive input terminal connected to the connection node between reference voltage resistor 9 and reference voltage resistor 10, and a negative input terminal receiving the voltage at node a. Comparator 8 has a positive input terminal receiving the voltage at node a, and a negative input terminal connected to the connection node between reference voltage resistor 10 and reference voltage resistor 11. The output terminals of comparators 7 and 8 are both connected to output node b. The voltage at the connection node between reference voltage resistor 9 and reference voltage resistor 10, which is input to the positive input terminal of comparator 7, is the upper reference voltage. The voltage at the connection node between reference voltage resistor 10 and reference voltage resistor 11, which is input to the negative input terminal of comparator 8, is the lower reference voltage.

[0029] Here, the upper reference voltage is set to the upper limit of the voltage range for the charger's power supply voltage as specified in the CHAdeMO specifications. The lower reference voltage is set a predetermined voltage lower than the lower limit of the voltage range for the charger's power supply voltage as specified in the CHAdeMO specifications. This predetermined voltage corresponds to the voltage drop across the limiting resistor 4 caused by leakage current when the operation enable / disable switch 6 is off. The leakage current here is the maximum value specified in the CHAdeMO specifications.

[0030] <Operation: When operation enable / disable switch 6 is off> FIG. 2 is a diagram illustrating operation when the operation enable / disable switch 6 is off. In FIG. 2, Vsp is a voltage corresponding to the range of power supply voltages of the charger specified in the CHAdeMO specifications. Vleak is a voltage corresponding to the voltage drop across the limiting resistor 4 caused by the maximum leakage current of the operation enable / disable switch 6 specified in the CHAdeMO specifications. The upper reference voltage applied to the positive input terminal of comparator 7 is set to the upper limit of the voltage range specified for the power supply voltage of the charger. The lower reference voltage applied to the negative input terminal of comparator 8 is set to the voltage obtained by subtracting Vleak from the lower limit of the range specified for the power supply voltage of the charger.

[0031] (Section 1) The charger's power supply voltage is within the specified range (normal) The voltage at node a is the charger's power supply voltage minus the voltage drop across limiting resistor 4 due to leakage current. However, in voltage change detection unit 20, the lower reference voltage is set to a voltage that assumes the maximum leakage current, as described above. Therefore, the voltage at node a is equal to or lower than the upper reference voltage and equal to or higher than the lower reference voltage, so the outputs of comparators 7 and 8 both become Hi-Z. As a result, output node b becomes Hi-Z, and photocoupler 1 turns off. In other words, the charger correctly recognizes that operation enable / disable switch 6 is off.

[0032] Furthermore, the lower limit reference voltage in the voltage change detection unit 20 is set to a voltage obtained by subtracting the voltage drop across the limiting resistor 4 caused by the maximum leakage current of the operation enable / disable switch 6 from the lower limit of the range specified for the power supply voltage of the charger. This makes it possible to prevent the operation enable / disable switch 6 from being mistakenly recognized as being on when it is off, even if the voltage at node a drops due to leakage current when the operation enable / disable switch 6 is off.

[0033] (Section 2) The charger's power supply voltage exceeds the specified voltage range (abnormality detected) In voltage change detection unit 20, the voltage at node a becomes higher than the upper reference voltage, so the output of comparator 7 becomes Low. Also, the voltage at node a becomes higher than the lower reference voltage, so the output of comparator 8 becomes Hi-Z. As a result, output node b becomes Low, and photocoupler 1 turns on.

[0034] (Section 3) The charger's power supply voltage falls below the specified voltage range (abnormality detected) In voltage change detection unit 20, the voltage at node a becomes lower than the upper reference voltage, so the output of comparator 7 becomes Hi-Z. Also, the voltage at node a becomes lower than the lower reference voltage, so the output of comparator 8 becomes Low. As a result, output node b becomes Low, and photocoupler 1 turns on.

[0035] That is, when the connector is connected to the charging port of the electric vehicle, the operation enable / disable switch 6 is off, so the photocoupler 1 is off as shown in section 1 of Figure 2. However, in this embodiment, when the power supply voltage of the charger deviates from the specified voltage range, as shown in section 2 or section 3, the photocoupler 1 is on. Therefore, it is possible to detect an abnormality in the power supply voltage of the charger.

[0036] <Operation: When operation enable / disable switch 6 is on> 3 is a diagram illustrating operation when the operation enable / disable switch 6 is on. When the operation enable / disable switch 6 is on, current flows from the charger's power supply to the electric vehicle via limiting resistors 4 and 5 and the operation enable / disable switch 6. As a result, the voltage at node a becomes the voltage obtained by subtracting the voltage drop across limiting resistor 4 caused by the current flowing through the operation enable / disable line 2 from the charger's power supply voltage.

[0037] Therefore, in the voltage change detection unit 20, the voltage at node a becomes lower than the upper reference voltage, and the output of the comparator 7 becomes Hi-Z. Also, the voltage at node a becomes lower than the lower reference voltage, and the output of the comparator 8 becomes Low. Therefore, the output node b becomes Low, and the photocoupler 1 turns on. In other words, the charger correctly recognizes that the operation enable / disable switch 6 is on.

[0038] As described above, according to this embodiment, when the electric vehicle's operation permission / prohibition switch 6 is on, the voltage at node a drops due to the voltage drop across the limiting resistor 4. When the voltage at node a falls below the lower reference voltage in the voltage change detection unit 20, the voltage change detection unit 20 outputs Low to the output node b. This turns on the photocoupler 1. On the other hand, when the electric vehicle's operation permission / prohibition switch 6 is off, the output node b is set to Hi-Z, and the photocoupler 1 turns off. Therefore, the on / off status of the electric vehicle's operation permission / prohibition switch 6 can be detected by the on / off status of the photocoupler 1.

[0039] The lower reference voltage in the voltage change detection unit 20 is set to a voltage obtained by subtracting the voltage drop across the limiting resistor 4 caused by the maximum leakage current of the operation enable / disable switch 6. Therefore, when the operation enable / disable switch 6 is off, even if the voltage at node a drops slightly due to the leakage current, the output node b is set to Hi-Z. This prevents the photocoupler 1 from being turned on erroneously.

[0040] Furthermore, when the operation enable / disable switch 6 is off, if the power supply voltage of the charger is too low and is lower than the lower reference voltage, or too high and is higher than the upper reference voltage, the voltage change detection unit 20 outputs Low to the output node b. This turns on the photocoupler 1, making it possible to detect an abnormality in the power supply voltage of the charger.

[0041] In the above embodiment, the upper and lower reference voltages in the voltage change detector 20 are set based on the range of power supply voltages for the charger specified in the CHAdeMO specifications, but this is not necessarily the case. For example, the upper and lower reference voltages may be set based on a voltage range narrower than the range specified in the CHAdeMO specifications.

[0042] Furthermore, the leakage current of the operation enable / disable switch 6 assumed when setting the lower reference voltage is set based on the maximum value of the leakage current specified in the CHAdeMO specifications. However, this is not necessarily the case. For example, the lower reference voltage may be set assuming a current value slightly larger than the maximum value of the leakage current specified in the CHAdeMO specifications.

[0043] (Other examples) Fig. 4 shows the circuit configuration of another example of a charger for an electric vehicle. In the configuration of Fig. 4, voltage change detection unit 21 includes reference voltage resistors 9 and 10 connected in series between a stabilized power supply and ground, and comparator 7. Comparator 7 has a negative input terminal connected to the connection node between reference voltage resistors 9 and 10, and a positive input terminal receiving the voltage at node a.

[0044] In this example, the voltage at the connection node between reference voltage resistor 9 and reference voltage resistor 10, i.e., the reference voltage, is set to a voltage obtained by subtracting a predetermined voltage from the power supply voltage of the charger (e.g., 12 V). The predetermined voltage subtracted here is a voltage that is smaller than the voltage drop across limiting resistor 4 when operation enable / disable switch 6 is on, and is larger than the voltage drop across limiting resistor 4 caused by leakage current from operation enable / disable switch 6.

[0045] When the operation enable / disable switch 6 is on, current flows from the charger's power supply to the electric vehicle via the limiting resistors 4 and 5 and the operation enable / disable switch 6. As a result, the voltage at node a becomes the voltage obtained by subtracting the voltage drop at limiting resistor 4 caused by the current flowing through the operation enable / disable line 2 from the power supply voltage of the charger. Therefore, the voltage at node a becomes lower than the reference voltage, so that in the voltage change detection unit 21, the output node b goes low and the photocoupler 1 turns on. In other words, the charger correctly recognizes that the operation enable / disable switch 6 is on.

[0046] When the operation enable / disable switch 6 is off, the voltage at node a is the voltage obtained by subtracting the voltage drop across limiting resistor 4 caused by the leakage current of the operation enable / disable switch 6 from the power supply voltage of the charger. Therefore, the voltage at node a becomes higher than the reference voltage, so that in the voltage change detection unit 21, output node b becomes Hi-Z and photocoupler 1 is turned off. In other words, the charger correctly recognizes that the operation enable / disable switch 6 is off.

[0047] The configuration of the voltage change detection unit in the present invention is not limited to the configurations of the voltage change detection units 20 and 21 shown in the above-described embodiment and other examples. In the present invention, the voltage change detection unit may be configured to have at least one reference voltage, compare the voltage at node a with the reference voltage, and set output node b to Hi-Z or output a low signal to output node b depending on the comparison result. By setting the reference voltage in the voltage change detection unit to a voltage that takes into account the leakage current of the operation enable / disable switch 6, it is possible to avoid erroneously recognizing the operation enable / disable switch 6 as being on when it is actually off. Therefore, the operation enable / disable signal of the electric vehicle can be reliably detected by the on / off state of the photocoupler 1. [Industrial Applicability]

[0048] The present invention is useful for improving the safety of chargers for electric vehicles. [Explanation of symbols]

[0049] 1. Photocoupler 2 Operation permission prohibition line 4 limiting resistors 6 Operation enable / disable switch 7,8 Comparator 9,10,11 Reference voltage resistor 20, 21 Voltage change detection section

Claims

1. A charger that charges a storage battery of an electric vehicle, an operation permission / prohibition line provided in a connector connected to a charging port of the electric vehicle; a limiting resistor having one end connected to a power source and the other end connected to the operation enable / disable line; a voltage change detection unit that receives a first voltage, which is the voltage at the other end of the limiting resistor, and outputs a signal corresponding to the first voltage to an output node; a photocoupler having a light-emitting diode and a light-receiving transistor, the anode of the light-emitting diode being connected to a power supply and the cathode being connected to the output node; when the connector is connected to a charging port of the electric vehicle, the operation enable / disable line is connected to an operation enable / disable switch of the electric vehicle, and when the operation enable / disable switch is on, a current flows from a power source of the charger through the operation enable / disable line; The voltage change detection unit At least one reference voltage is set, the first voltage is compared with the at least one reference voltage, and the output node is set to high impedance or a low level is output to the output node according to the comparison result. Electric vehicle charger.

2. The charger for an electric vehicle according to claim 1, The voltage change detection unit a lower reference voltage and an upper reference voltage are set, the upper reference voltage is set to an upper limit of a predetermined voltage range, and the lower reference voltage is set to a voltage obtained by subtracting a voltage drop across the limiting resistor due to a leakage current of the operation enable / disable switch from the lower limit of the predetermined voltage range, When the first voltage is between the lower reference voltage and the upper reference voltage, the output node is set to high impedance, and when the first voltage is lower than the lower reference voltage or higher than the upper reference voltage, a low signal is output to the output node. Electric vehicle charger.

3. 3. The charger for an electric vehicle according to claim 2, The voltage change detection unit first, second and third reference voltage resistors connected in series between the regulated power supply and ground; a first comparator having a positive input terminal connected to a connection node between the first reference voltage resistor and the second reference voltage resistor and a negative input terminal receiving the first voltage; a second comparator having a positive input terminal receiving the first voltage and a negative input terminal connected to a connection node between the second reference voltage resistor and the third reference voltage resistor; The output terminals of the first and second comparators are connected to the output node. Electric vehicle charger.

4. The charger for an electric vehicle according to claim 2 or 3, the predetermined voltage range is the range of power supply voltages of the charger specified in the CHAdeMO specifications, The lower reference voltage is a voltage obtained by subtracting the voltage drop across the limiting resistor due to the maximum leakage current of the operation enable / disable switch defined in the CHAdeMO specifications from the lower limit of the predetermined voltage range. Electric vehicle charger.

5. The charger for an electric vehicle according to claim 1, The voltage change detection unit a reference voltage is set to a voltage obtained by subtracting a predetermined voltage from a power supply voltage of the electric vehicle charger, the predetermined voltage being smaller than a voltage drop across the limiting resistor when the operation permission / prohibition switch is on, and larger than a voltage drop across the limiting resistor due to a leakage current of the operation permission / prohibition switch; When the first voltage is higher than the reference voltage, the output node is set to a high impedance, and when the first voltage is lower than the reference voltage, a low signal is output to the output node. Electric vehicle charger.

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