Power conversion device

Abstract

The present invention relates to a power conversion device. The power conversion device includes a power conversion unit, a relay, and a welding detection unit. The welding detection unit includes: a first resistor connected to a terminal on one side of the relay; a capacitor and a second resistor connected to a terminal on the other side of the relay; an application unit that applies a check signal to the relay via the capacitor and the second resistor; and a determination unit connected between the capacitor and the second resistor, which detects a signal based on the application of the check signal from the application unit to determine whether the relay is welded.

Description

Technical Field

[0001] The present invention relates to a power conversion device, and more particularly to a power conversion device for determining whether a relay is welded. Background Art

[0002] Conventionally, a power conversion device for determining whether a relay is welded has been known. For example, such a power conversion device is disclosed in Japanese Patent No. 3789819.

[0003] The above-mentioned Japanese Patent No. 3789819 discloses the following in-vehicle device (in-vehicle power conversion device), which includes: a relay provided in a power supply line; and a detection circuit including a plurality of optocouplers for detecting (determining) whether the relay is welded.

[0004] However, in the in-vehicle device (in-vehicle power conversion device) of the above-mentioned Japanese Patent No. 3789819, a detection circuit including a plurality of optocouplers, which are components with a relatively short service life, is used to detect (determine) whether the relay is welded. Therefore, corresponding to the use of optocouplers, which are components with a relatively short service life, the period until one of the plurality of optocouplers fails due to reaching the end of its service life becomes relatively short. Thus, there is a problem of low reliability of the detection circuit as a determination unit for determining whether the relay is welded. Summary of the Invention

[0005] The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a power conversion device capable of suppressing a decrease in the reliability of a determination unit for determining whether a relay is welded.

[0006] To achieve the above object, a power conversion device according to one aspect of the present invention includes: a power conversion unit that converts power supplied to a vehicle; a relay provided in a power supply line connected to the power conversion unit; and a welding detection unit that detects welding of the relay, wherein the welding detection unit includes: a first resistor connected to one terminal of the relay; a capacitor and a second resistor connected to the other terminal of the relay; an application unit that applies a check signal to the relay via the capacitor and the second resistor; and a determination unit connected between the capacitor and the second resistor, which detects a signal based on the application of the check signal by the application unit to determine whether the relay is welded.

[0007] In the power conversion device according to an aspect of the present invention, as described above, a welding detection unit is provided. The welding detection unit includes: a first resistor connected to a terminal on one side of the relay; a capacitor and a second resistor connected to a terminal on the other side of the relay; an application unit that applies a check signal to the relay via the capacitor and the second resistor; and a determination unit connected between the capacitor and the second resistor, which detects a signal based on the application of the check signal from the application unit to determine whether the relay is welded. Thus, a resistor and a capacitor with a relatively long service life can be used as components to determine the welding of the relay. Therefore, compared with the case where an opto-coupler with a relatively short service life is used as a component, a decrease in the reliability of the determination unit for determining whether the relay is welded can be suppressed. In addition, the applied check signal can be delayed by the first resistor and then input to the determination unit. Therefore, the determination unit can easily determine whether the relay is welded based on the delay of the signal.

[0008] In the power conversion device according to the above aspect, preferably, the other side of the relay has a first terminal and a second terminal. The relay is configured to switch the terminal to be connected to the terminal on one side between the first terminal and the second terminal. The capacitor, the second resistor, and the determination unit are respectively connected to the first terminal and the second terminal. The determination unit of the welding detection unit is configured to determine whether the relay is welded based on the signals input from both the first terminal and the second terminal due to the application of the check signal from the application unit. With this configuration, in a relay that uses the first terminal and the second terminal to switch the power supply line, a decrease in the reliability of the determination unit for determining whether welding occurs on the first terminal side or the second terminal side of the relay can be suppressed.

[0009] In this case, preferably, the determination unit of the welding detection unit is configured to determine whether the relay is welded based on the time difference between the signals input from both the first terminal and the second terminal due to the application of the check signal from the application unit. With this configuration, since the first resistor connected to the terminal on the same side as the terminal on one side of the relay is connected to the terminal on the other side of the relay where the first terminal and the second terminal are located, the applied check signal can be delayed and then input to the determination unit. Therefore, the determination unit can more easily determine whether the relay is welded based on the time difference of the input signals.

[0010] In the power conversion device according to the above aspect, preferably, the application unit of the welding detection unit is configured to apply a pulse voltage as the check signal to the relay. With this configuration, by comparing the timing of the pulse wave of the pulse voltage with the timing of the signal input to the determination unit, the determination unit can easily detect the delay of the signal caused by the first resistor connected to the relay.

[0011] In the power conversion device based on one aspect described above, preferably, the determination unit includes a control unit that performs the following control: detecting a change in the application of the inspection signal based on the application unit to determine whether the relay is welded. With this configuration, compared with the case of using a hardware circuit for determination, it is possible to more easily determine whether the relay is welded by the software-based control of the control unit.

[0012] In the power conversion device based on one aspect described above, preferably, the determination unit is connected between the capacitor and the second resistor via a binarization unit that binarizes the signal based on the application of the inspection signal of the application unit. With this configuration, it is possible to binarize the signal input to the determination unit to facilitate detection of the signal delay.

[0013] In this case, preferably, the binarization unit is configured to binarize a decreasing signal using a first threshold value and binarize an increasing signal using a second threshold value different from the first threshold value. With this configuration, it is possible to make the threshold value in the case of signal increase different from the threshold value in the case of signal decrease, and thus it is possible to binarize the signal input to the determination unit according to the threshold values suitable for signal increase and signal decrease, respectively.

[0014] In the power conversion device according to one aspect described above, preferably, the relay includes a first relay and a second relay serially provided in the power supply line. The other sides of the first relay and the second relay respectively have a first terminal and a second terminal. The first relay and the second relay are configured to switch the terminals to be connected to one side terminal between the first terminal and the second terminal. One side terminal of the first relay is connected to the first terminal on the other side of the second relay. The welding detection unit is provided with a common first resistor at one side terminal of the second relay, and capacitors and second resistors are respectively provided at the first terminal on the other side of the first relay, the second terminal on the other side of the first relay, and the second terminal on the other side of the second relay. The determination unit is configured to, in a state where one side terminal of the second relay is connected to the first terminal on the other side, determine whether the first relay is welded based on signals input from the first terminal and the second terminal on the other side of the first relay through the first resistor and the capacitors and second resistors respectively provided at the first terminal and the second terminal on the other side of the first relay, and determine whether the second relay is welded based on signals input from the first terminal and the second terminal on the other side of the second relay through the first resistor, the capacitors and second resistors provided at the first terminal or the second terminal on the other side of the first relay, and the capacitors and second resistors provided at the second terminal on the other side of the second relay. With such a configuration, a common first resistor can be provided for the first relay and the second relay, so there is no need to separately provide a first resistor for the first relay and the second relay. In addition, three sets of capacitors and second resistors are provided for the first terminal and the second terminal of the first relay and the first terminal and the second terminal of the second relay, so there is no need to separately provide four sets of capacitors and second resistors for the first terminal and the second terminal of the first relay and the first terminal and the second terminal of the second relay. Thus, an increase in the number of components of the welding detection unit can be suppressed, and the circuit structure of the welding detection unit can be simplified. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a block diagram showing a vehicle equipped with a power conversion device according to the first embodiment.

[0016] Figure 2 is a circuit diagram showing a welding detection unit of a power conversion device according to the first embodiment.

[0017] Figure 3 is a diagram showing an example of the time change of the voltage at each position of the welding detection unit during welding detection of a relay of a power conversion device according to the first embodiment.

[0018] Figure 4 is a circuit diagram showing a welding detection unit of a power conversion device according to the second embodiment.

[0019] Figure 5 This is a circuit diagram showing a first example during the welding detection of the relay of the power conversion device according to the second embodiment.

[0020] Figure 6 This is a graph showing the time variation of the voltages at respective positions of the welding detection unit in the first example during the welding detection of the relay of the power conversion device according to the second embodiment.

[0021] Figure 7 This is a circuit diagram showing a second example during the welding detection of the relay of the power conversion device according to the second embodiment.

[0022] Figure 8 This is a graph showing the time variation of the voltages at respective positions of the welding detection unit in the second example during the welding detection of the relay of the power conversion device according to the second embodiment.

[0023] Figure 9 This is a circuit diagram showing a third example during the welding detection of the relay of the power conversion device according to the second embodiment.

[0024] Figure 10 This is a graph showing the time variation of the voltages at respective positions of the welding detection unit in the third example during the welding detection of the relay of the power conversion device according to the second embodiment. Detailed Embodiment

[0025] Hereinafter, embodiments in which the present invention is embodied will be described based on the drawings.

[0026] (First Embodiment)

[0027] Refer to Figures 1 to 3 to describe the structure of the power conversion device 100 according to the first embodiment.

[0028] As Figure 1 shown, the power conversion device 100 according to the first embodiment is mounted on an electric vehicle 200. The electric vehicle 200 travels by driving a motor using the power charged in the battery 220. In addition, the electric vehicle 200 is configured to be connectable to an external power source 300 via a connector 210 to charge the battery 220 from the external power source 300. In addition, the electric vehicle 200 is configured to be able to supply the power of the battery 220 to electrical equipment in the vehicle via in-vehicle power supply 230. In addition, the electric vehicle 200 is configured to be able to supply the power of the battery 220 to a residence or the like as single-phase three-wire commercial power (100V / 200V AC power) via a power supply terminal 240. In addition, the electric vehicle 200 is an example of the "vehicle" in the present invention.

[0029] The battery 220 includes a storage battery capable of being charged with electric power. The storage battery is, for example, a lithium-ion secondary battery. The battery 220 is charged with DC power obtained by converting AC power input from an external power source 300 outside the vehicle body by the power conversion device 100. The battery 220 is configured to be able to output the stored (charged) power as DC power.

[0030] (Structure of the power conversion device)

[0031] As Figure 1 shown, the power conversion device 100 includes an AC / DC conversion circuit 11, a DC / DC conversion circuit 12, and relays 21, 22, 23, 24, and 25. In addition, as Figure 2 shown, the power conversion device 100 includes a welding detection unit 30. The welding detection unit 30 includes a CPU 31, a relay drive circuit 32, and an application unit 33. In addition, the welding detection unit 30 includes resistors R101, R102, R201, R202, R301. In addition, the welding detection unit 30 includes capacitors C101, C102, C201, C202. In addition, the welding detection unit 30 includes binarization units IC101, IC201. In addition, the AC / DC conversion circuit 11 and the DC / DC conversion circuit 12 are examples of the "power conversion unit" in the present invention, and the CPU 31 is an example of the "determination unit" and "control unit" in the present invention. In addition, the resistor R301 is an example of the "first resistor" in the present invention, and the resistors R101, R201 are examples of the "second resistor" in the present invention.

[0032] The power conversion device 100 is configured to convert the AC power supplied from the external power source 300 into DC power and then supply it to the battery 220. In addition, the power conversion device 100 is configured to convert the DC power supplied from the battery 220 into AC power and then supply it to the in-vehicle power supply 230 or the power supply terminal 240.

[0033] The relays 21 and 22 are configured to switch between the case of supplying (charging) power from the external power source 300 to the battery 220 and the case of supplying (discharging) power from the battery 220 to the in-vehicle power supply 230 or the power supply terminal 240. Specifically, in the case of supplying (charging) power from the external power source 300 to the battery 220, the relays 21 and 22 are respectively controlled such that the terminal a is connected to the terminal c. In addition, in the case of supplying (discharging) power from the battery 220 to the in-vehicle power supply 230 or the power supply terminal 240, the relays 21 and 22 are respectively controlled such that the terminal b is connected to the terminal c.

[0034] Relays 23, 24, and 25 are configured to switch between the case of supplying (releasing) power from battery 220 to in-vehicle power supply 230 and the case of supplying (releasing) power from battery 220 to power supply terminal 240. Specifically, in the case of supplying (releasing) power from battery 220 to in-vehicle power supply 230, relays 23, 24, and 25 are respectively controlled such that terminal a is connected to terminal c. Additionally, in the case of supplying (releasing) power from battery 220 to power supply terminal 240, relays 23, 24, and 25 are respectively controlled such that terminal b is connected to terminal c.

[0035] AC / DC conversion circuit 11 and DC / DC conversion circuit 12 are configured to convert the power supplied to electric vehicle 200. Specifically, AC / DC conversion circuit 11 and DC / DC conversion circuit 12 are configured to convert the alternating current power supplied from external power source 300 into direct current power and then supply it to battery 220. Additionally, AC / DC conversion circuit 11 and DC / DC conversion circuit 12 are configured to convert the direct current power supplied from battery 220 into alternating current power and then supply it to in-vehicle power supply 230 or power supply terminal 240. AC / DC conversion circuit 11 and DC / DC conversion circuit 12 include a plurality of switching elements and a plurality of capacitors, and are configured to convert the input power and then output it.

[0036] When battery 220 is being charged, AC / DC conversion circuit 11 converts the alternating current power supplied from external power source 300 into direct current power and then supplies it to DC / DC conversion circuit 12. Additionally, when battery 220 is discharging, AC / DC conversion circuit 11 converts the direct current power supplied from DC / DC conversion circuit 12 into alternating current power and then supplies it to in-vehicle power supply 230 or power supply terminal 240.

[0037] When battery 220 is being charged, DC / DC conversion circuit 12 converts the voltage of the direct current power supplied from AC / DC conversion circuit 11 and then supplies direct current power to battery 220. Additionally, when battery 220 is discharging, DC / DC conversion circuit 12 converts the voltage of the direct current power supplied from battery 220 and then supplies direct current power to AC / DC conversion circuit 11.

[0038] Relays 21 - 25 are provided on the power supply line connected to AC / DC conversion circuit 11 and DC / DC conversion circuit 12. As Figure 2 shown, relays 21 - 25 are controlled by CPU 31 via relay drive circuit 32 to switch the connections of relays 21 - 25. Additionally, terminals c are respectively provided on one side of relays 21 - 25, and terminals a and b are respectively provided on the other side. Additionally, relays 21 - 25 are configured to switch the terminal to be connected to terminal c between terminals a and b.

[0039] As Figure 2 shown, the welding detection unit 30 is configured to detect the welding of the relays 21 to 25. In addition, Figure 2 the structure in which the welding detection unit 30 is provided for the relay 21 is shown, but the same applies to the relays 22 to 25.

[0040] The capacitor C101 is connected to the terminal a of the relay 21. That is, the capacitor C101 is connected to the power supply line. The resistor R101 is connected to the capacitor C101. In addition, the resistor R101 is connected to the application unit 33. The application unit 33 is connected to the ground. A resistor R102 is connected between the resistor R101 and the capacitor C101. The resistor R102 is connected to the binarization unit IC101. The binarization unit IC101 is connected to the CPU 31. A capacitor C102 is connected between the resistor R102 and the binarization unit IC101. The capacitor C102 is connected to the ground.

[0041] The capacitor C201 is connected to the terminal b of the relay 21. That is, the capacitor C201 is connected to the power supply line. The resistor R201 is connected to the capacitor C201. In addition, the resistor R201 is connected to the application unit 33. The application unit 33 is connected to the ground. A resistor R202 is connected between the resistor R201 and the capacitor C201. The resistor R202 is connected to the binarization unit IC201. The binarization unit IC201 is connected to the CPU 31. A capacitor C202 is connected between the resistor R202 and the binarization unit IC201. The capacitor C202 is connected to the ground.

[0042] The resistor R301 is connected to the terminal c of the relay 21. In addition, the resistor R301 is connected to the ground.

[0043] The capacitors C101 and C201 are provided to prevent a large voltage from being applied from the power supply line that conducts a relatively large voltage (100 V, 200 V) to the CPU 31 that is driven by a relatively small voltage (about 5 V). The resistors R101 and R201 are provided to prevent an excessive current from flowing through the capacitors C101 and C201.

[0044] The resistor R102 and the capacitor C102 form an RC circuit and are configured to delay the applied voltage from the application unit 33. The resistor R202 and the capacitor C202 form an RC circuit and are configured to delay the applied voltage from the application unit 33. The resistor R301 is configured to delay the voltage applied to the connected terminal (terminal a or b).

[0045] That is, the welding detection unit 30 includes: a resistor R301 connected to a terminal c on one side of the relay 21; capacitors C101 (C201) and resistors R101 (R201) connected to a terminal a (b) on the other side of the relay 21; an application unit 33 that applies a check signal to the relay 21 via the capacitors C101 (C201) and the resistors R101 (R201); and a CPU 31 connected between the capacitors C101 (C201) and the resistors R101 (R201), which detects a signal change based on the application of the check signal from the application unit 33 to determine whether the relay 21 is welded.

[0046] In addition, the capacitors C101 (C201), the resistors R101 (R201), and the CPU 31 of the welding detection unit 30 are respectively connected to the terminals a and b of the relay 21 (22 to 25). In addition, the CPU 31 of the welding detection unit 30 is configured to determine whether the relay 21 (22 to 25) is welded based on the signals input from both the terminals a and b by the application of the check signal from the application unit 33.

[0047] Specifically, the CPU 31 of the welding detection unit 30 is configured to determine whether the relay 21 (22 to 25) is welded based on the time difference between the signals input from both the terminals a and b by the application of the check signal from the application unit 33. That is, since the signal of the terminal connected to the resistor 301 among the signals input from both the terminals a and b by the CPU 31 is delayed, the CPU 31 detects that the terminal of the relay 21 where the signal delay occurs is connected. Then, the CPU 31 compares the terminal a or b of the relay 21 connected by means of the control of the relay drive circuit 32 with the terminal a or b detected as being connected by the signal delay. If the terminal a or b connected by the control is the same as the terminal a or b detected as being connected, the CPU 31 determines that there is no welding. On the other hand, if the terminal a or b connected by the control is different from the terminal a or b detected as being connected, the CPU 31 determines that the relay 21 is welded at the terminal a or b detected as being connected.

[0048] The CPU 31 is connected between the capacitor C101 (C201) and the resistor R101 (R201) via a binary conversion unit IC101 (IC201), and the binary conversion unit IC101 (IC201) binary-converts the signal based on the application of the check signal from the application unit 33. As Figure 3As shown, the binarization units IC101 (IC201) are configured to binarize a decreasing signal using a first threshold value and to binarize an increasing signal using a second threshold value different from the first threshold value. For example, the first threshold value is smaller than the second threshold value. The binarization units IC101 and IC201 include, for example, Schmidt trigger ICs.

[0049] The CPU 31 includes a control unit that performs the following control: detecting a signal change based on the application of an inspection signal from the application unit 33 to determine whether the relays 21 (22 to 25) are welded. That is, the CPU 31 is configured to control the welding detection operation of the welding detection unit 30 by executing a program (software). The CPU 31 controls the driving of the relay drive circuit 32 to switch the relays 21 (22 to 25). In addition, the CPU 31 performs control to apply a signal (voltage) from the application unit 33.

[0050] The application unit 33 of the welding detection unit 30 is configured to Figure 3 apply a pulse voltage to the relays 21 (22 to 25) as an inspection signal as shown.

[0051] (Welding detection operation)

[0052] Refer to Figure 3 to describe the welding detection operation of the relays 21 (22 to 25) by the CPU 31.

[0053] In Figure 3 the example of, describe the case where the terminals a and c of the relay 21 (22 to 25) are connected as shown in Figure 2 . The CPU 31 performs control to apply a pulse voltage from the application unit 33. Since the terminal b of the relay 21 is not connected to the terminal c, the voltage Vb1 is a waveform of a first-order delay system formed by the resistors R201, R202, and the capacitor C202. On the other hand, since the terminal a of the relay 21 is connected to the terminal c, the voltage Va1 is a waveform that is affected not only by the resistors R101, R102, and the capacitor C102 but also by the capacitor C101 and the resistor R301 (a waveform with further delay). Since there is the above difference between the terminals b and a of the relay 21, a time difference is generated in the outputs of the binarization units IC101 and IC201. The waveform (voltage Va2) on the side where the relay 21 is conducting is delayed by this time difference with respect to the waveform (voltage Vb2) on the side where the relay 21 is not conducting. Through the above, it is possible to determine the currently connected terminal (a or b) of the relay 21. In addition, when the terminal b of the relay 21 is connected to the terminal c, the waveform (voltage Vb2) on the side where the relay 21 is conducting is delayed with respect to the waveform (voltage Va2) on the side where the relay 21 is not conducting.

[0054] For example, the CPU 31 applies a pulse voltage from the application unit 33 while outputting a control signal to connect the terminal a and the terminal c in the relay 21. Therefore, if the CPU 31 detects the input of a waveform in a state where the voltage Va2 is delayed with respect to the voltage Vb2, it determines that the relay 21 is normal (not welded). On the other hand, if the CPU 31 detects the input of a waveform in a state where the voltage Vb2 is delayed with respect to the voltage Va2, it determines that the relay 21 is abnormal (welded).

[0055] In addition, by monitoring the H / L states of the voltage Va2 and the voltage Vb2 through the digital input port of the CPU 31, the phase difference between the voltage Va2 and the voltage Vb2 can be detected. In addition, a pulse voltage can be realized by outputting an H / L signal with a fixed period from the digital output port of the CPU 31.

[0056] (Effect of the first embodiment)

[0057] In the first embodiment, the following effects can be obtained.

[0058] In the first embodiment, as described above, the welding detection unit 30 is provided. The welding detection unit 30 includes: a resistor R301 connected to the terminal c on one side of the relay 21 (22 to 25); capacitors C101 (C201) and resistors R101 (R201) connected to the terminal a (b) on the other side of the relay 21 (22 to 25); an application unit 33 that applies an inspection signal to the relay 21 (22 to 25) via the capacitors C101 (C201) and the resistors R101 (R201); and a CPU 31 connected between the capacitors C101 (C201) and the resistors R101 (R201), which detects a signal change based on the application of the inspection signal from the application unit 33 to determine whether the relay 21 (22 to 25) is welded. Thus, resistors and capacitors with a relatively long service life can be used as components to determine the welding of the relay 21 (22 to 25). Therefore, compared with the case where an optocoupler with a relatively short service life is used as a component, a decrease in the reliability of the determination unit (CPU 31) for determining whether the relay 21 (22 to 25) is welded can be suppressed. In addition, the applied inspection signal can be delayed by the resistor R301 and then input to the CPU 31. Therefore, it is easy for the CPU 31 to determine whether the relay 21 (22 to 25) is welded based on the signal delay.

[0059] In addition, in the first embodiment, as described above, capacitors C101 (C201), resistors R101 (R201), and the CPU 31 of the welding detection unit 30 are respectively connected to terminals a and b of the relay 21 (22 to 25). The CPU 31 of the welding detection unit 30 is configured to determine whether the relay 21 (22 to 25) is welded based on signals input from both terminals a and b by applying the inspection signal through the application unit 33. Thereby, it is possible to suppress a decrease in the reliability of the determination unit (CPU 31) that determines whether the relay 21 (22 to 25) for switching the power supply line using terminals a and b is welded on the a-side or b-side of the terminal.

[0060] In addition, in the first embodiment, as described above, the CPU 31 of the welding detection unit 30 is configured to determine whether the relay 21 (22 to 25) is welded based on the time difference between signals input from both terminals a and b by applying the inspection signal through the application unit 33. Since the resistor R301 connected to the terminal on one side of the relay 21 (22 to 25) is connected to the terminals a and b on the other side of the relay 21 (22 to 25), the applied inspection signal can be delayed and then the signal can be input to the CPU 31. Thereby, it is possible for the CPU 31 to more easily determine whether the relay 21 (22 to 25) is welded based on the time difference between the input signals.

[0061] In addition, in the first embodiment, as described above, the application unit 33 of the welding detection unit 30 is configured to apply a pulse voltage to the relay 21 (22 to 25) as an inspection signal. Thereby, it is possible for the CPU 31 to easily detect the delay of the signal caused by the resistor R301 connected to the relay 21 (22 to 25) by comparing the timing of the pulse wave of the pulse voltage with the timing of the signal input to the CPU 31.

[0062] In addition, in the first embodiment, as described above, the CPU 31 is connected between the capacitor C101 (C201) and the resistor R101 (R201) via the binary conversion unit IC101 (IC201), and the binary conversion unit IC101 (IC201) binary-converts the signal based on the application of the inspection signal by the application unit 33. Thereby, the signal input to the CPU 31 can be binary-converted to make it easier to detect the signal delay.

[0063] In addition, in the first embodiment, as described above, the binarization unit IC101 (IC201) is configured to binarize a decreasing signal using a first threshold value and binarize an increasing signal using a second threshold value different from the first threshold value. Thereby, the threshold value in the case where the signal increases can be made different from the threshold value in the case where the signal decreases. Therefore, the signal input to the CPU 31 can be binarized using threshold values that are respectively suitable for the increase and decrease of the signal.

[0064] (Second Embodiment)

[0065] Next, with reference to Figures 4 to 10 the structure of the power conversion device according to the second embodiment will be described. In the second embodiment, an example of a welding detection unit having a structure different from that of the first embodiment, in which a common resistor is used for serially arranged relays, will be described.

[0066] Here, in the second embodiment, as Figure 4 shown, the welding detection unit 40 includes a CPU 31, relay drive circuits 34 and 35 (refer to Figure 5 ), and an application unit 33. In addition, as Figure 4 shown, the welding detection unit 40 includes resistors R11, R12, R21, R22, R31, R32, R33, R41, R42, R51, R52, R61, R62, R71, R72, R81, R82, R91, R92. In addition, the welding detection unit 40 includes capacitors C11, C12, C21, C22, C41, C42, C51, C52, C61, C62, C71, C72, C81, C82, C91, C92. In addition, the welding detection unit 40 includes binarization units IC11, IC21, IC41, IC51, IC61, IC71, IC81, IC91. Further, the CPU 31 is an example of the "determination unit" and "control unit" in the present invention. In addition, the resistors R31, R32, R33 are an example of the "first resistor" in the present invention, and the resistors R11, R21, R41, R51, R61, R71, R81, R91 are an example of the "second resistor" in the present invention.

[0067] The capacitor C11 is connected to the terminal a of the relay 21. That is, the capacitor C11 is connected to the power supply line. The resistor R11 is connected to the capacitor C11. In addition, the resistor R11 is connected to the application unit 33. The application unit 33 is connected to the ground. The resistor R12 is connected between the resistor R11 and the capacitor C11. The resistor R12 is connected to the binarization unit IC11. The binarization unit IC11 is connected to the CPU 31. The capacitor C12 is connected between the resistor R12 and the binarization unit IC11. The capacitor C12 is connected to the ground. In addition, the relay 21 is an example of the "second relay" in the present invention.

[0068] The capacitor C21 is connected to the terminal a of the relay 22. That is to say, the capacitor C21 is connected to the power supply line. The resistor R21 is connected to the capacitor C21. In addition, the resistor R21 is connected to the application unit 33. A resistor R22 is connected between the resistor R21 and the capacitor C21. The resistor R22 is connected to the binarization unit IC21. The binarization unit IC21 is connected to the CPU 31. A capacitor C22 is connected between the resistor R22 and the binarization unit IC21. The capacitor C22 is connected to the ground. In addition, the relay 22 is an example of the "second relay" in the present invention.

[0069] The resistor R31 is connected to the terminal c of the relay 21. In addition, the resistor R31 is connected to the ground. The resistor R32 is connected to the terminal c of the relay 22. In addition, the resistor R32 is connected to the ground.

[0070] The capacitor C41 is connected to the terminal a of the relay 23. That is to say, the capacitor C41 is connected to the power supply line. The resistor R41 is connected to the capacitor C41. In addition, the resistor R41 is connected to the application unit 33. A resistor R42 is connected between the resistor R41 and the capacitor C41. The resistor R42 is connected to the binarization unit IC41. The binarization unit IC41 is connected to the CPU 31. A capacitor C42 is connected between the resistor R42 and the binarization unit IC41. The capacitor C42 is connected to the ground. In addition, the relay 23 is an example of the "first relay" in the present invention.

[0071] The capacitor C51 is connected to the terminal b of the relay 23. That is to say, the capacitor C51 is connected to the power supply line. The resistor R51 is connected to the capacitor C51. In addition, the resistor R51 is connected to the application unit 33. A resistor R52 is connected between the resistor R51 and the capacitor C51. The resistor R52 is connected to the binarization unit IC51. The binarization unit IC51 is connected to the CPU 31. A capacitor C52 is connected between the resistor R52 and the binarization unit IC51. The capacitor C52 is connected to the ground.

[0072] The capacitor C61 is connected to the terminal a of the relay 24. That is to say, the capacitor C61 is connected to the power supply line. The resistor R61 is connected to the capacitor C61. In addition, the resistor R61 is connected to the application unit 33. A resistor R62 is connected between the resistor R61 and the capacitor C61. The resistor R62 is connected to the binarization unit IC61. The binarization unit IC61 is connected to the CPU 31. A capacitor C62 is connected between the resistor R62 and the binarization unit IC61. The capacitor C62 is connected to the ground.

[0073] The capacitor C71 is connected to the terminal b of the relay 24. That is to say, the capacitor C71 is connected to the power supply line. The resistor R71 is connected to the capacitor C71. In addition, the resistor R71 is connected to the application unit 33. A resistor R72 is connected between the resistor R71 and the capacitor C71. The resistor R72 is connected to the binarization unit IC71. The binarization unit IC71 is connected to the CPU 31. A capacitor C72 is connected between the resistor R72 and the binarization unit IC71. The capacitor C72 is connected to the ground.

[0074] The resistor R33 is connected to the terminal c of the relay 24. In addition, the resistor R33 is connected to the ground.

[0075] The capacitor C81 is connected to the terminal a of the relay 25. That is to say, the capacitor C81 is connected to the power supply line. The resistor R81 is connected to the capacitor C81. In addition, the resistor R81 is connected to the application unit 33. A resistor R82 is connected between the resistor R81 and the capacitor C81. The resistor R82 is connected to the binarization unit IC81. The binarization unit IC81 is connected to the CPU 31. A capacitor C82 is connected between the resistor R82 and the binarization unit IC81. The capacitor C82 is connected to the ground. In addition, the relay 25 is an example of the "first relay" in the present invention.

[0076] The capacitor C91 is connected to the terminal b of the relay 25. That is to say, the capacitor C91 is connected to the power supply line. The resistor R91 is connected to the capacitor C91. In addition, the resistor R91 is connected to the application unit 33. A resistor R92 is connected between the resistor R91 and the capacitor C91. The resistor R92 is connected to the binarization unit IC91. The binarization unit IC91 is connected to the CPU 31. A capacitor C92 is connected between the resistor R92 and the binarization unit IC91. The capacitor C92 is connected to the ground.

[0077] That is to say, the terminal c on one side of the relay 23(25) is connected to the terminal b on the other side of the relay 21(22). In the welding detection unit 40, a common resistor R31(R32) is provided at the terminal c on one side of the relay 21(22), and a capacitor C41(C81) and a resistor R41(R81) are provided at the terminal a on the other side of the relay 23(25). In addition, in the welding detection unit 40, a capacitor C51(C91) and a resistor R51(R91) are provided at the terminal b on the other side of the relay 23(25), and a capacitor C11(C21) and a resistor R11(R21) are provided at the terminal a on the other side of the relay 21(22).

[0078] In addition, the CPU 31 is configured to determine whether the relay 23 (25) is fused based on signals input from the terminals a and b on the other side of the relay 23 (25) through the resistor R31 (R32) and the capacitor C41 or C51 (C81 or C91) and the resistor R41 or R51 (R81 or R91) provided at the terminal a or terminal b on the other side of the relay 23 (25) when the terminal c on one side of the relay 21 (22) is connected to the terminal b on the other side. In addition, the CPU 31 is configured to determine whether the relay 21 (22) is fused based on signals input from the terminals a and b on the other side of the relay 21 (22) through the resistor R31 (R32), the capacitor C41 or C51 (C81 or C91) and the resistor R41 or R51 (R81 or R91) provided at the terminal a or terminal b on the other side of the relay 23 (25), and the capacitor C11 (C21) and the resistor R11 (R21) provided at the terminal a on the other side of the relay 21 (22).

[0079] As Figures 5 to 10 shown, the fusion detection unit 40 is configured to detect the fusion of the relays 21, 22, 23, and 25. In addition, in Figure 5 , Figure 7 and Figure 9 is shown a structure in which the fusion detection unit 40 is provided for the relays 21 and 23, but the same applies to the relays 22 and 25. In addition, the fusion detection unit of the relay 24 is the same as that of the first embodiment.

[0080] (Fusion Detection Operation)

[0081] Refer to Figures 5 to 10 to describe the fusion detection operation of the relays 21, 23 (22, 25) by the CPU 31.

[0082] The description is as Figure 5 shown, in the case where the terminal a of the relay 21 (22) is connected to the terminal c and the terminal a of the relay 23 (25) is connected to the terminal c. The CPU 31 controls to apply a pulse voltage from the application unit 33. Since the terminal b of the relay 21 is not connected to the terminal c, as Figure 6As shown, the voltage Vd1 (Ve1) is the waveform of a first-order delay system formed by the resistor R41 (R51), the resistor R42 (R52), and the capacitor C42 (C52). On the other hand, since the terminal a of the relay 21 is connected to the terminal c, the voltage Vc1 is a waveform that is affected by the capacitor C11 and the resistor R31 in addition to being affected by the resistor R11, the resistor R12, and the capacitor C12 (it is a waveform with further delay). There is the above difference between the terminal b and the terminal a of the relay 21, so there is a time difference between the output of the binarization unit IC11 and the outputs of the binarization units IC41 and IC51. The waveform (voltage Vc2) on the side where the relay 21 is turned on is delayed by this time difference with respect to the waveform (voltages Vd2 and Ve2) on the side where the relay 21 is not turned on. Through the above, it is possible to determine the currently connected terminal (a or b) of the relay 21. In addition, no matter which of the terminals a and b of the relay 23 is connected to the terminal c, the terminal b of the relay 21 is not connected to the terminal c, so the result is the same.

[0083] For example, when the CPU 31 outputs a signal to connect the terminal a in the relay 21 to the terminal c, a pulse voltage is applied from the application unit 33. Therefore, if the CPU 31 detects the input of a waveform in a state where the voltage Vc2 is delayed with respect to the voltages Vd2 and Ve2, it determines that the relay 21 is normal (not welded). On the other hand, if the CPU 31 detects the input of a waveform in a state where one of the voltages Vd2 and Ve2 is delayed with respect to the voltage Vc2, it determines that the relay 21 is abnormal (welded).

[0084] Explanation is as Figure 7 shown, the case where the terminal b of the relay 21 (22) is connected to the terminal c and the terminal a of the relay 23 (25) is connected to the terminal c. The CPU 31 controls to apply a pulse voltage from the application unit 33. Since the terminal b of the relay 23 is not connected to the terminal c, as Figure 8 shown, the voltage Ve1 is the waveform of a first-order delay system formed by the resistor R51, the resistor R52, and the capacitor C52. On the other hand, since the terminal a of the relay 23 is connected to the terminal c, the voltage Vd1 is a waveform that is affected by the capacitor C41 and the resistor R31 in addition to being affected by the resistor R41, the resistor R42, and the capacitor C42 (it is a waveform with further delay). Since there is the above difference between the terminal b and the terminal a of the relay 23, there is a time difference between the output of the binarization unit IC41 and the output of the binarization unit IC51. The waveform (voltage Vd2) on the side where the relay 23 is turned on is delayed by this time difference with respect to the waveform (voltage Ve2) on the side where the relay 23 is not turned on. Through the above, it is possible to determine the currently connected terminal (a or b) of the relay 23.

[0085] For example, while the CPU 31 outputs a signal to connect the terminal a and the terminal c in the relay 23, a pulse voltage is applied from the application unit 33. Therefore, if the CPU 31 detects the input of a waveform in a state where the voltage Vd2 is delayed with respect to the voltages Vc2 and Ve2, it determines that the relay 23 is normal (not welded). On the other hand, if the CPU 31 detects the input of a waveform in a state where Ve2 is delayed with respect to the voltage Vd2, it determines that the relay 23 is abnormal (welded).

[0086] Description is as Figure 9 shown, the case where the terminal b and the terminal c of the relay 21 (22) are connected, and the terminal b and the terminal c of the relay 23 (25) are connected. The CPU 31 performs control to apply a pulse voltage from the application unit 33. Since the terminal a of the relay 23 is not connected to the terminal c, as Figure 10 shown, the voltage Vd1 is a waveform of a first-order delay system formed by the resistor R41, the resistor R42, and the capacitor C42. On the other hand, since the terminal b of the relay 23 is connected to the terminal c, the voltage Ve1 is a waveform that is affected by the capacitor C51 and the resistor R31 in addition to being affected by the resistor R51, the resistor R52, and the capacitor C52 (a waveform with further delay). Due to the above differences between the terminal a and the terminal b of the relay 23, there is a time difference in the outputs of the binarization unit IC41 and the binarization unit IC51. The waveform (voltage Ve2) on the conducting side of the relay 23 is delayed with respect to the waveform (voltage Vd2) on the non-conducting side of the relay 23 by this time difference. Through the above, it is possible to determine the currently connected terminal (a or b) of the relay 23.

[0087] For example, while the CPU 31 outputs a signal to connect the terminal b and the terminal c in the relay 23, a pulse voltage is applied from the application unit 33. Therefore, if the CPU 31 detects the input of a waveform in a state where the voltage Ve2 is delayed with respect to the voltages Vc2 and Vd2, it determines that the relay 23 is normal (not welded). On the other hand, if the CPU 31 detects the input of a waveform in a state where Vd2 is delayed with respect to the voltage Ve2, it determines that the relay 23 is abnormal (welded).

[0088] Other configurations of the second embodiment are the same as those of the first embodiment described above.

[0089] (Effect of the second embodiment)

[0090] In the second embodiment, similar to the first embodiment described above, it is possible to suppress a decrease in the reliability of the determination unit (CPU 31) for determining whether the relays 21 (22 to 25) are welded.

[0091] In addition, in the second embodiment, as described above, the CPU 31 is configured to determine whether the relays 21 (22) are welded based on signals input from the capacitors C41 or C51 (C81 or C91) and the resistors R41 or R51 (R81 or R91) provided at the terminals a or b on the other side of the relays 23 (25) through the resistors R31 (R32), and the capacitors C11 (C21) and the resistors R11 (R21) provided at the terminal a on the other side of the relays 21 (22). Thereby, a common resistor R31 (R32) can be provided for the relays 23 (25) and the relays 21 (22), so that there is no need to separately provide resistors for the relays 23 (25) and the relays 21 (22). In addition, three capacitors C11, C41, C51 (C21, C81, C91) and resistors R11, R41, R51 (R21, R81, R91) are provided for the terminals a and b of the relays 23 (25) and the terminals a and b of the relays 21 (22), so that there is no need to separately provide four capacitors and resistors for the terminals a and b of the relays 23 (25) and the terminals a and b of the relays 21 (22). Thereby, an increase in the number of components of the welding detection unit 40 can be suppressed, and the circuit structure of the welding detection unit 40 can be simplified.

[0092] In addition, other effects of the second embodiment are the same as those of the first embodiment.

[0093] (Modification example)

[0094] In addition, the embodiments disclosed this time should be considered illustrative in all aspects and not restrictive. The scope of the present invention is shown by the claims, rather than by the description of the above embodiments. The scope of the present invention also includes all changes (modification examples) within the meaning and scope equivalent to the claims.

[0095] For example, in the above first embodiment and second embodiment, an example in which the power conversion device is mounted on an electric vehicle is shown, but the present invention is not limited thereto. For example, the power conversion device may also be mounted on a hybrid vehicle driven by electricity and an engine, or a fuel cell vehicle powered by a fuel cell. In addition, the power conversion device may also be mounted on a tram.

[0096] In addition, in the above first embodiment and second embodiment, an example of a structure in which the power conversion device includes a plurality of relays and a welding detection unit for detecting welding is provided for the plurality of relays, but the present invention is not limited thereto. In the present invention, a welding detection unit for detecting welding may also be provided for a part of the plurality of relays.

[0097] In addition, in the above-described first and second embodiments, an example of a structure for detecting the welding of a relay for switching connection objects is shown, but the present invention is not limited thereto. In the present invention, it may also be a structure for detecting the welding of a relay for switching ON / OFF. In this case, it may be that, in a state where the relay is ON, the time length of a signal based on the application of an inspection signal by an application unit is detected, and if the time length of this signal is greater than a threshold value (if the delay is long), it is detected as ON, and if the time length of this signal is less than the threshold value (if the delay is short), it is detected as OFF.

[0098] In addition, in the above-described first and second embodiments, an example of a structure for detecting the welding of a relay for selecting and switching one from two connection objects is shown, but the present invention is not limited thereto. In the present invention, it may also be a structure for detecting the welding of a relay for selecting and switching one from three or more connection objects.

[0099] In addition, in the above-described first and second embodiments, an example of a structure for switching the connection object of a relay during the switching between charging and discharging and a structure for switching the discharge object by a relay are shown, but the present invention is not limited thereto. In the present invention, it may also be a structure for switching a charging power source by a relay.

Claims

1. A power conversion device comprising: A power conversion unit that converts the power supplied to the vehicle; A relay, which is arranged on a power supply line connected to the power conversion unit; And A welding detection unit that detects the welding of the relay, Wherein, The welding detection unit includes: a first resistor connected to one terminal of the relay; a capacitor and a second resistor, the capacitor and the second resistor being connected to the other terminal of the relay; an application unit that applies a check signal to the relay via the capacitor and the second resistor; and a determination unit connected between the capacitor and the second resistor, detecting a signal based on the application of the check signal by the application unit to determine whether the relay is welded, Wherein the other side of the relay has a first terminal and a second terminal, and the relay is configured to switch the terminal to be connected to one side terminal between the first terminal and the second terminal, and a separate capacitor and a separate second resistor are respectively connected to the first terminal and the second terminal.

2. The power conversion device according to claim 1, wherein The determination unit is respectively connected to the first terminal and the second terminal, The determination unit of the welding detection unit is configured to determine whether the relay is welded based on the signals input from both the first terminal and the second terminal due to the application of the check signal by the application unit.

3. The power conversion device according to claim 2, wherein The determination unit of the welding detection unit is configured to determine whether the relay is welded based on the time difference between the signals input from both the first terminal and the second terminal due to the application of the check signal by the application unit.

4. The power conversion device according to any one of claims 1 to 3, wherein The application unit of the welding detection unit is configured to apply a pulse voltage as the check signal to the relay.

5. The power conversion device according to any one of claims 1 to 3, wherein The determination unit includes a control unit that performs the following control: detecting a signal based on the application of the check signal by the application unit to determine whether the relay is welded.

6. The power conversion device according to any one of claims 1 to 3, wherein The determination unit is connected between the capacitor and the second resistor via a binarization unit, and the binarization unit binarizes the signal based on the application of the check signal by the application unit.

7. The power conversion device according to claim 6, wherein The binarization unit is configured to binarize a decreasing signal using a first threshold value and binarize an increasing signal using a second threshold value different from the first threshold value.

8. The power conversion device according to any one of claims 1 to 3, wherein The relay includes a first relay and a second relay connected in series to the power supply line, The other sides of the first relay and the second relay respectively have a first terminal and a second terminal, and the first relay and the second relay are configured to switch the terminals to be connected to the terminals on one side between the first terminal and the second terminal. One terminal on the side of the first relay is connected to the first terminal on the other side of the second relay. The welding detection unit is provided with the common first resistor at one terminal on the side of the second relay, and the capacitor and the second resistor are respectively provided at the first terminal on the other side of the first relay, the second terminal on the other side of the first relay, and the second terminal on the other side of the second relay. The determination unit is configured to, in a state where one terminal on the side of the second relay is connected to the first terminal on the other side, determine whether the first relay is welded based on the signals input from the first terminal and the second terminal on the other side of the first relay through the first resistor, the capacitor and the second resistor respectively provided at the first terminal and the second terminal on the other side of the first relay, and determine whether the second relay is welded based on the signals input from the first terminal and the second terminal on the other side of the second relay through the first resistor, the capacitor and the second resistor provided at the first terminal or the second terminal on the other side of the first relay, and the capacitor and the second resistor provided at the second terminal on the other side of the second relay.

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