Patent Description:
A power conversion device that determines whether or not a relay is welded is known in general, as disclosed in <CIT>, for example.

<CIT> discloses an in-vehicle device (in-vehicle power conversion device) including a relay provided in a power supply line and a detection circuit that includes a plurality of photocouplers and detects (determines) whether or not the relay is welded.

In the in-vehicle device (in-vehicle power conversion device) disclosed in <CIT>, the detection circuit including the plurality of photocouplers, which are components having a relatively short life, is used to detect (determine) whether or not the relay is welded. Therefore, the photocouplers, which are components having a relatively short life, are used, and thus a period until one of the plurality of photocouplers fails due to the life is short. Thus, the reliability of the detection circuit as a determiner that determines whether or not the relay is welded is low.

<CIT> describes a feed control device including a contact device, an output detector, a contact weld sensor, and an alarm device. The output detector is configured to detect the presence of power feeding into the side of an electrically-powered car from an external power supply. The contact weld sensor is configured to sense that the contact device is welded based on a detection result of the output detector if detecting the presence of power feeding from the external power supply to a feed line for the contact device when a state signal representing charge permission is not entered. The alarm device is configured, if the contact weld sensor senses that the contact device is welded, to indicate the occurrence of weld to the outside.

<CIT> describes an electronic control unit. When the electronic control unit disconnects a second power storage device from a drive device while a hybrid vehicle is traveling, the electronic control unit disconnects one of a contact point and a contact point of a system main relay and causes the vehicle to continue traveling using electric power supplied from a first power storage device to drive device. After the vehicle finishes traveling, the electronic control unit performs a discharging operation for discharging a charge remaining in a first capacitor and a second capacitor with the one contact point of system main relay being disconnected. If the charge is not discharged appropriately, the electronic control unit determines that welding occurs in at least one of system main relay and system main relay.

The present invention has been proposed in order to solve the aforementioned problem, and an object of the present invention is to provide a power conversion device capable of significantly reducing or preventing a decrease in the reliability of a determiner that determines whether or not a relay is welded.

The aforementioned object is attained by a power conversion device according to claim <NUM>. Claims <NUM> to <NUM> refer to specifically advantageous realizations of the power conversion device according to claim <NUM>.

In order to attain the aforementioned object, a power conversion device according to an aspect of the present invention includes a power converter configured to convert power supplied to a vehicle, a relay provided in a power supply line connected to the power converter, and a welding detector configured to detect welding of the relay. The welding detector includes a first resistor connected to a terminal of the relay on a first side, a capacitor and a second resistor, both of which are connected to a terminal of the relay on a second side, an application unit configured to apply an inspection signal to the relay via the capacitor and the second resistor, and a determiner connected between the capacitor and the second resistor, the determiner configured to detect a signal based on application of the inspection signal by the application unit to determine whether or not the relay is welded.

As described above, the power conversion device according to this aspect of the present invention includes the welding detector including the first resistor connected to the terminal of the relay on the first side, the capacitor and the second resistor, both of which are connected to the terminal of the relay on the second side, the application unit to apply the inspection signal to the relay via the capacitor and the second resistor, and the determiner connected between the capacitor and the second resistor, the determiner detecting the signal based on the application of the inspection signal by the application unit to determine whether or not the relay is welded. Accordingly, welding of the relay can be determined using the resistors and the capacitor having a relatively long life as components, and thus as compared with a case in which photocouplers having a relatively short life are used as components, a decrease in the reliability of the determiner that determines whether or not the relay is welded can be significantly reduced or prevented. Furthermore, the applied inspection signal is delayed by the first resistor, and a signal is input to the determiner such that the determiner can easily determine whether or not the relay is welded based on the signal delay.

In the aforementioned power conversion device according to this aspect, the relay includes, on the second side, a first terminal and a second terminal, and is configured to switch a terminal connected to the terminal on the first side between the first terminal and the second terminal. The capacitor, the second resistor, and the determiner are preferably connected to each of the first terminal and the second terminal, and the determiner of the welding detector is preferably configured to determine whether or not the relay is welded based on signals input from both the first terminal and the second terminal by the application of the inspection signal by the application unit. Accordingly, a decrease in the reliability of the determiner that determines whether or not the relay that switches the power supply line between the first terminal and the second terminal is welded to the first terminal side or the second terminal side can be significantly reduced or prevented.

In this case, the determiner of the welding detector is preferably configured to determine whether or not the relay is welded based on a time difference between the signals input from both the first terminal and the second terminal by the application of the inspection signal by the application unit. Accordingly, the first resistor connected to the terminal on the first side is connected to the terminal connected to the terminal of the relay on the first side among the first terminal and the second terminal of the relay on the second side such that the applied inspection signal is delayed, and a signal is input to the determiner. Thus, the determiner can more easily determine whether or not the relay is welded based on the time difference between the input signals.

In the aforementioned power conversion device according to this aspect, the application unit of the welding detector is preferably configured to apply a pulse voltage as the inspection signal to the relay. Accordingly, the determiner can easily detect signal delay caused by the first resistor connected to the relay by comparing the timing of the pulse wave of the pulse voltage with the timing of the signal input to the determiner.

In the aforementioned power conversion device according to this aspect, the determiner preferably includes a controller configured to perform a control to detect the signal based on the application of the inspection signal by the application unit to determine whether or not the relay is welded. Accordingly, as compared with a case in which a determination is made using a hardware circuit, it is possible to more easily determine whether or not the relay is welded under software control of the controller.

In the aforementioned power conversion device according to this aspect, the determiner is preferably connected between the capacitor and the second resistor via a binarization unit configured to binarize the signal based on the application of the inspection signal by the application unit. Accordingly, the signal input to the determiner can be binarized to facilitate detection of signal delay.

In this case, the binarization unit is preferably configured to binarize a decreasing signal using a first threshold, and to binarize an increasing signal using a second threshold different from the first threshold. Accordingly, the threshold in a case in which the signal increases and the threshold in a case in which the signal decreases can be different from each other, and thus the signal input to the determiner can be binarized using the threshold suitable for each of the increase and decrease of the signal.

In the aforementioned power conversion device according to this aspect, the relay preferably includes a first relay and a second relay provided in series in the power supply line, each of the first relay and the second relay preferably includes, on the second side, a first terminal and a second terminal, and is preferably configured to switch a terminal connected to the terminal on the first side between the first terminal and the second terminal, the terminal of the first relay on the first side is preferably connected to the first terminal of the second relay on the second side, the welding detector preferably includes a common first resistor provided at the terminal of the second relay on the first side, and the capacitor and the second resistor, both of which are provided at each of the first terminal of the first relay on the second side, the second terminal of the first relay on the second side, and the second terminal of the second relay on the second side, and the determiner is preferably configured to, in a state in which the terminal of the second relay on the first side and the first terminal of the second relay on the second side are connected to each other, determine whether or not the first relay is welded based on signals input from the first terminal and the second terminal of the first relay on the second side via the first resistor, and the capacitor and the second resistor, both of which are provided at each of the first terminal and the second terminal of the first relay on the second side, and determine whether or not the second relay is welded based on signals input from the first terminal and the second terminal of the second relay on the second side via the first resistor, the capacitor and the second resistor, both of which are provided at the first terminal or the second terminal of the first relay on the second side, and the capacitor and the second resistor, both of which are provided at the second terminal of the second relay on the second side. Accordingly, the common first resistor is provided for the first relay and the second relay, and thus it is not necessary to separately provide first resistors for the first relay and the second relay. Furthermore, the three capacitors and the three 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, and thus it is not necessary to separately provide four capacitors and four 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 detector can be significantly reduced or prevented, and the circuit configuration of the welding detector can be simplified.

Embodiments of the present invention are hereinafter described with reference to the drawings.

The configuration of a power conversion device <NUM> according to a first embodiment is now described with reference to <FIG>.

As shown in <FIG>, the power conversion device <NUM> according to the first embodiment is mounted on an electric vehicle <NUM>. The electric vehicle <NUM> runs by driving a motor with power charged in a battery <NUM>. The electric vehicle <NUM> is connected to an external power supply <NUM> via a connector <NUM> such that the battery <NUM> can be charged from the external power supply <NUM>. The electric vehicle <NUM> can supply the power of the battery <NUM> to electric equipment in the vehicle via an in-vehicle power supply <NUM>. The electric vehicle <NUM> can supply the power of the battery <NUM> to a house or the like via a power supply terminal <NUM> for single-phase three-wire commercial power (100V/200V AC power). The electric vehicle <NUM> is an example of a "vehicle" in the claims.

The battery <NUM> includes a storage battery capable of charging power. The storage battery is a lithium-ion secondary battery, for example. The battery <NUM> charges DC power converted by the power conversion device <NUM> from AC power input from the external power supply <NUM> outside a vehicle body. The battery <NUM> can output the stored (charged) power as DC power.

As shown in <FIG>, the power conversion device <NUM> includes an AC/DC conversion circuit <NUM>, a DC/DC conversion circuit <NUM>, and relays <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. As shown in <FIG>, the power conversion device <NUM> includes a welding detector <NUM>. The welding detector <NUM> includes a CPU <NUM>, a relay drive circuit <NUM>, and an application unit <NUM>. The welding detector <NUM> includes resistors R101, R102, R201, R202, and R301. The welding detector <NUM> includes capacitors C101, C102, C201, and C202. The welding detector <NUM> includes binarization units IC101 and IC201. The AC/DC conversion circuit <NUM> and the DC/DC conversion circuit <NUM> are examples of a "power converter" in the claims, and the CPU <NUM> is an example of a "determiner" or a "controller" in the claims. The resistor R301 is an example of a "first resistor" in the claims, and the resistors R101 and R201 are examples of a "second resistor" in the claims.

The power conversion device <NUM> converts AC power supplied from the external power supply <NUM> into DC power and supplies the DC power to the battery <NUM>. Furthermore, the power conversion device <NUM> converts the DC power supplied from the battery <NUM> into AC power and supplies the AC power to the in-vehicle power supply <NUM> or the power supply terminal <NUM>.

The relays <NUM> and <NUM> switch between supplying (charging) power from the external power supply <NUM> to the battery <NUM> and supplying (discharging) power from the battery <NUM> to the in-vehicle power supply <NUM> or the power supply terminal <NUM>. Specifically, when power is supplied (charged) from the external power supply <NUM> to the battery <NUM>, each of the relays <NUM> and <NUM> is controlled such that terminals a and c are connected to each other. When power is supplied (discharged) from the battery <NUM> to the in-vehicle power supply <NUM> or the power supply terminal <NUM>, each of the relays <NUM> and <NUM> is controlled such that terminals b and c are connected to each other.

The relays <NUM>, <NUM>, and <NUM> switch between supplying (discharging) power from the battery <NUM> to the in-vehicle power supply <NUM> and supplying (discharging) power from the battery <NUM> to the power supply terminal <NUM>. Specifically, when power is supplied (discharged) from the battery <NUM> to the in-vehicle power supply <NUM>, each of the relays <NUM>, <NUM>, and <NUM> is controlled such that terminals a and c are connected to each other. When power is supplied (discharged) from the battery <NUM> to the power supply terminal <NUM>, each of the relays <NUM>, <NUM>, and <NUM> is controlled such that terminals b and c are connected to each other.

The AC/DC conversion circuit <NUM> and the DC/DC conversion circuit <NUM> convert power supplied to the electric vehicle <NUM>. Specifically, the AC/DC conversion circuit <NUM> and the DC/DC conversion circuit <NUM> convert the AC power supplied from the external power supply <NUM> into DC power and supply the DC power to the battery <NUM>. The AC/DC conversion circuit <NUM> and the DC/DC conversion circuit <NUM> convert the DC power supplied from the battery <NUM> into AC power and supply the AC power to the in-vehicle power supply <NUM> or the power supply terminal <NUM>. The AC/DC conversion circuit <NUM> and the DC/DC conversion circuit <NUM> include a plurality of switching elements and a plurality of capacitors, and convert and output the input power.

The AC/DC conversion circuit <NUM> converts the AC power supplied from the external power supply <NUM> into DC power and supplies the DC power to the DC/DC conversion circuit <NUM> when the battery <NUM> is charged. The AC/DC conversion circuit <NUM> converts the DC power supplied from the DC/DC conversion circuit <NUM> into AC power and supplies the AC power to the in-vehicle power supply <NUM> or the power supply terminal <NUM> when the battery <NUM> is discharged.

The DC/DC conversion circuit <NUM> converts the voltage of the DC power supplied from the AC/DC conversion circuit <NUM> and supplies the DC power to the battery <NUM> when the battery <NUM> is charged. The DC/DC conversion circuit <NUM> converts the voltage of the DC power supplied from the battery <NUM> and supplies the DC power to the AC/DC conversion circuit <NUM> when the battery <NUM> is discharged.

The relays <NUM> to <NUM> are provided in a power supply line connected to the AC/DC conversion circuit <NUM> and the DC/DC conversion circuit <NUM>. As shown in <FIG>, the relays <NUM> to <NUM> are controlled by the CPU <NUM> via the relay drive circuit <NUM> such that the connections can be switched. Each of the relays <NUM> to <NUM> includes the terminal c on a first side and the terminals a and b on a second side. The relays <NUM> to <NUM> switch a terminal connected to the terminal c between the terminals a and b.

As shown in <FIG>, the welding detector <NUM> detects welding of the relays <NUM> to <NUM>. Although <FIG> shows the configuration in which the welding detector <NUM> is provided for the relay <NUM>, the same applies to the relays <NUM> to <NUM>.

The capacitor C101 is connected to the terminal a of the relay <NUM>. That is, the capacitor C101 is connected to the power supply line. The resistor R101 is connected to the capacitor C101. Furthermore, the resistor R101 is connected to the application unit <NUM>. The application unit <NUM> is connected to a ground. The resistor R102 is connected between the resistor R101 and the capacitor C101. The binarization unit IC101 is connected to the resistor R102. The CPU <NUM> is connected to the binarization unit IC101. The capacitor C102 is connected between the resistor R102 and the binarization unit IC101. The capacitor C102 is connected to the ground.

The capacitor C201 is connected to the terminal b of the relay <NUM>. That is, the capacitor C201 is connected to the power supply line. The resistor R201 is connected to the capacitor C201. Furthermore, the resistor R201 is connected to the application unit <NUM>. The application unit <NUM> is connected to the ground. The resistor R202 is connected between the resistor R201 and the capacitor C201. The binarization unit IC201 is connected to the resistor R202. The CPU <NUM> is connected to the binarization unit IC201. The capacitor C202 is connected between the resistor R202 and the binarization unit IC201. The capacitor C202 is connected to the ground.

The resistor R301 is connected to the terminal c of the relay <NUM>. Furthermore, the resistor R301 is connected to the ground.

The capacitors C101 and C201 are provided such that a high voltage is not applied to the CPU <NUM> driven by power having a relatively low voltage (about 5V) from the power supply line in which power having a relatively high voltage (100V, 200V) is conducted. The resistors R101 and R201 are provided such that an excessive current does not flow through the capacitors C101 and C201.

The resistor R102 and the capacitor C102 form an RC circuit and delay an applied voltage from the application unit <NUM>. The resistor R202 and the capacitor C202 form an RC circuit and delay an applied voltage from the application unit <NUM>. The resistor R301 delays a voltage applied to the connected terminal (terminal a or b).

That is, the welding detector <NUM> includes the resistor R301 connected to the terminal c of the relay <NUM> on the first side, the capacitor C101 (C201) and the resistor R101 (R201) connected to the terminal a (b) of the relay <NUM> on the second side, the application unit <NUM> that applies an inspection signal to the relay <NUM> via the capacitor C101 (C201) and the resistor R101 (R201), and the CPU <NUM> connected between the capacitor C101 (C201) and the resistor R101 (R201) and configured to detect a signal change based on application of the inspection signal by the application unit <NUM> to determine whether or not the relay <NUM> is welded.

In the welding detector <NUM>, the capacitor C101 (C201), the resistor R101 (R201), and the CPU <NUM> are connected to each of the terminals a and b of the relay <NUM> (<NUM> to <NUM>). The CPU <NUM> of the welding detector <NUM> determines whether or not the relay <NUM> (<NUM> to <NUM>) is welded based on signals input from both the terminals a and b by application of the inspection signal by the application unit <NUM>.

Specifically, the CPU <NUM> of the welding detector <NUM> determines whether or not the relay <NUM> (<NUM> to <NUM>) is welded based on a time difference between the signals input from both the terminals a and b by application of the inspection signal by the application unit <NUM>. That is, the signal of the terminal connected to the resistor <NUM> among the signals input from both the terminals a and b is delayed, and thus the CPU <NUM> detects that the terminal with the delayed signal of the relay <NUM> is connected. Then, the CPU <NUM> compares the terminal a or b of the relay <NUM> connected by control via the relay drive circuit <NUM> with the terminal a or b, the connection of which has been detected due to the signal delay. When the terminal a or b connected by control and the terminal a or b, the connection of which has been detected match, the CPU <NUM> determines that the relay <NUM> is not welded. On the other hand, when the terminal a or b connected by control and the terminal a or b, the connection of which has been detected are different, the CPU <NUM> determines that the relay <NUM> is welded to the terminal a or b, the connection of which has been detected.

The CPU <NUM> is connected between the capacitor C101 (C201) and the resistor R101 (R201) via the binarization unit IC101 (IC201) that binarizes a signal based on application of the inspection signal by the application unit <NUM>. As shown in <FIG>, the binarization unit IC101 (IC201) binarizes a decreasing signal using a first threshold, and binarizes an increasing signal using a second threshold different from the first threshold. For example, the first threshold is smaller than the second threshold. Each of the binarization units IC101 and IC201 includes a Schmitt trigger IC, for example.

The CPU <NUM> includes a controller configured to perform a control to detect a signal change based on application of the inspection signal by the application unit <NUM> to determine whether or not the relay <NUM> (<NUM> to <NUM>) is welded. That is, the CPU <NUM> controls the welding detection operation of the welding detector <NUM> by executing a program (software). The CPU <NUM> controls driving of the relay drive circuit <NUM> to switch the relay <NUM> (<NUM> to <NUM>). Furthermore, the CPU <NUM> controls the application unit <NUM> to apply a signal (voltage).

As shown in <FIG>, the application unit <NUM> of the welding detector <NUM> applies a pulse voltage as an inspection signal to the relay <NUM> (<NUM> to <NUM>).

The welding detection operation for the relay <NUM> (<NUM> to <NUM>) by the CPU <NUM> is now described with reference to <FIG>.

In an example of <FIG>, a case in which the terminal a of the relay <NUM> (<NUM> to <NUM>) is connected to the terminal c as shown in <FIG> is described. The CPU <NUM> controls the application unit <NUM> to apply a pulse voltage. The terminal b of the relay <NUM> is not connected to the terminal c, and thus a voltage Vb1 has a first-order lag waveform due to the resistor R201, the resistor R202, and the capacitor C202. On the other hand, the terminal a of the relay <NUM> is connected to the terminal c, and thus a voltage Va1 has a waveform (further delayed waveform) influenced by the capacitor C101 and the resistor R301 in addition to the resistor R101, the resistor R102, and the capacitor C102. There is the above difference between the terminals b and a of the relay <NUM>, and thus there is a time difference between the outputs of the binarization units IC101 and IC201. This time difference causes a waveform (voltage Va2) on the side with which the relay <NUM> is conducting to be delayed with respect to a waveform (voltage Vb2) on the side not conducting with the relay <NUM>. From the above, it is possible to determine the connected terminal (a or b) of the relay <NUM>. When the terminal b of the relay <NUM> is connected to the terminal c, the waveform (voltage Vb2) on the side with which the relay <NUM> is conducting is delayed with respect to the waveform (voltage Va2) on the side not conducting with the relay <NUM>.

For example, the CPU <NUM> applies a pulse voltage from the application unit <NUM> while outputting a control signal such that in the relay <NUM>, the terminal a is connected to the terminal c. When detecting an input of the waveform in which the voltage Va2 is delayed with respect to the voltage Vb2, the CPU <NUM> determines that the relay <NUM> is normal (not welded). On the other hand, when detecting an input of the waveform in which the voltage Vb2 is delayed with respect to the voltage Va2, the CPU <NUM> determines that the relay <NUM> is abnormal (welding has occurred).

A phase difference between the voltage Va2 and the voltage Vb2 can be detected by monitoring each H/L state with a digital input port of the CPU <NUM>. Furthermore, the pulse voltage can be achieved by outputting an H/L signal having a fixed cycle from a digital output port of the CPU <NUM>.

According to the first embodiment, the following advantageous effects are achieved.

According to the first embodiment, as described above, the power conversion device <NUM> includes the welding detector <NUM> including the resistor R301 connected to the terminal c of the relay <NUM> (<NUM> to <NUM>) on the first side, the capacitor C101 (C201) and the resistor R101 (R201) connected to the terminal a (b) of the relay <NUM> (<NUM> to <NUM>) on the second side, the application unit <NUM> that applies an inspection signal to the relay <NUM> (<NUM> to <NUM>) via the capacitor C101 (C201) and the resistor R101 (R201), and the CPU <NUM> connected between the capacitor C101 (C201) and the resistor R101 (R201) and configured to detect a signal change based on application of the inspection signal by the application unit <NUM> to determine whether or not the relay <NUM> (<NUM> to <NUM>) is welded. Accordingly, welding of the relay <NUM> (<NUM> to <NUM>) can be determined using the resistors and the capacitor having a relatively long life as components, and thus as compared with a case in which photocouplers having a relatively short life are used as components, a decrease in the reliability of the determiner (CPU <NUM>) that determines whether or not the relay <NUM> (<NUM> to <NUM>) is welded can be significantly reduced or prevented. Furthermore, the applied inspection signal is delayed by the resistor R301, and a signal is input to the CPU <NUM> such that the CPU <NUM> can easily determine whether or not the relay <NUM> (<NUM> to <NUM>) is welded based on the signal delay.

According to the first embodiment, as described above, the capacitor C101 (C201), the resistor R101 (R201), and the CPU <NUM> are connected to each of the terminals a and b of the relay <NUM> (<NUM> to <NUM>), and the CPU <NUM> of the welding detector <NUM> determines whether or not the relay <NUM> (<NUM> to <NUM>) is welded based on the signals input from both the terminals a and b by application of the inspection signal by the application unit <NUM>. Accordingly, a decrease in the reliability of the determiner (CPU <NUM>) that determines whether or not the relay <NUM> (<NUM> to <NUM>) that switches the power supply line between the terminals a and b is welded to the terminal a side or the terminal b side can be significantly reduced or prevented.

According to the first embodiment, as described above, the CPU <NUM> of the welding detector <NUM> determines whether or not the relay <NUM> (<NUM> to <NUM>) is welded based on the time difference between the signals input from both the terminals a and b by application of the inspection signal by the application unit <NUM>. Accordingly, the resistor R301 connected to the terminal on the first side is connected to the terminal connected to the terminal of the relay <NUM> (<NUM> to <NUM>) on the first side among the terminals a and b of the relay <NUM> (<NUM> to <NUM>) on the second side such that the applied inspection signal is delayed, and a signal is input to the CPU <NUM>. Thus, the CPU <NUM> can more easily determine whether or not the relay <NUM> (<NUM> to <NUM>) is welded based on the time difference between the input signals.

According to the first embodiment, as described above, the application unit <NUM> of the welding detector <NUM> applies a pulse voltage as an inspection signal to the relay <NUM> (<NUM> to <NUM>). Accordingly, the CPU <NUM> can easily detect signal delay caused by the resistor R301 connected to the relay <NUM> (<NUM> to <NUM>) by comparing the timing of the pulse wave of the pulse voltage with the timing of the signal input to the CPU <NUM>.

According to the first embodiment, as described above, the CPU <NUM> is connected between the capacitor C101 (C201) and the resistor R101 (R201) via the binarization unit IC101 (IC201) that binarizes the signal based on application of the inspection signal by the application unit <NUM>. Accordingly, the signal input to the CPU <NUM> can be binarized to facilitate detection of signal delay.

According to the first embodiment, as described above, the binarization unit IC101 (IC201) binarizes the decreasing signal using the first threshold, and binarizes the increasing signal using the second threshold different from the first threshold. Accordingly, the threshold in a case in which the signal increases and the threshold in a case in which the signal decreases can be different from each other, and thus the signal input to the CPU <NUM> can be binarized using the threshold suitable for each of the increase and decrease of the signal.

The configuration of a power conversion device according to a second embodiment is now described with reference to <FIG>. In the second embodiment, an example of a welding detector having a configuration using common resistors for relays provided in series unlike the first embodiment is described.

In the second embodiment, as shown in <FIG>, a welding detector <NUM> includes a CPU <NUM>, relay drive circuits <NUM> and <NUM> (see <FIG>), and an application unit <NUM>. Furthermore, as shown in <FIG>, the welding detector <NUM> includes resistors R11, R12, R21, R22, R31, R32, R33, R41, R42, R51, R52, R61, R62, R71, R72, R81, R82, R91, and R92. The welding detector <NUM> includes capacitors C11, C12, C21, C22, C41, C42, C51, C52, C61, C62, C71, C72, C81, C82, C91, and C92. The welding detector <NUM> includes binarization units IC11, IC21, IC41, IC51, IC61, IC71, IC81, and IC91. The CPU <NUM> is an example of a "determiner" or a "controller" in the claims. The resistors R31, R32, and R33 are examples of a "first resistor" in the claims, and the resistors R11, R21, R41, R51, R61, R71, R81, and R91 are examples of a "second resistor" in the claims.

The capacitor C11 is connected to a terminal a of a relay <NUM>. That is, the capacitor C11 is connected to a power supply line. The resistor R11 is connected to the capacitor C11. Furthermore, the resistor R11 is connected to the application unit <NUM>. The application unit <NUM> is connected to a ground. The resistor R12 is connected between the resistor R11 and the capacitor C11. The binarization unit IC11 is connected to the resistor R12. The CPU <NUM> is connected to the binarization unit IC11. The capacitor C12 is connected between the resistor R12 and the binarization unit IC11. The capacitor C12 is connected to the ground. The relay <NUM> is an example of a "second relay" in the claims.

The capacitor C21 is connected to a terminal a of a relay <NUM>. That is, the capacitor C21 is connected to the power supply line. The resistor R21 is connected to the capacitor C21. Furthermore, the resistor R21 is connected to the application unit <NUM>. The resistor R22 is connected between the resistor R21 and the capacitor C21. The binarization unit IC21 is connected to the resistor R22. The CPU <NUM> is connected to the binarization unit IC21. The capacitor C22 is connected between the resistor R22 and the binarization unit IC21. The capacitor C22 is connected to the ground. The relay <NUM> is an example of a "second relay" in the claims.

The resistor R31 is connected to a terminal c of the relay <NUM>. Furthermore, the resistor R31 is connected to the ground. The resistor R32 is connected to a terminal c of the relay <NUM>. Furthermore, the resistor R32 is connected to the ground.

The capacitor C41 is connected to a terminal a of a relay <NUM>. That is, the capacitor C41 is connected to the power supply line. The resistor R41 is connected to the capacitor C41. Furthermore, the resistor R41 is connected to the application unit <NUM>. The resistor R42 is connected between the resistor R41 and the capacitor C41. The binarization unit IC41 is connected to the resistor R42. The CPU <NUM> is connected to the binarization unit IC41. The capacitor C42 is connected between the resistor R42 and the binarization unit IC41. The capacitor C42 is connected to the ground. The relay <NUM> is an example of a "first relay" in the claims.

The capacitor C51 is connected to a terminal b of the relay <NUM>. That is, the capacitor C51 is connected to the power supply line. The resistor R51 is connected to the capacitor C51. Furthermore, the resistor R51 is connected to the application unit <NUM>. The resistor R52 is connected between the resistor R51 and the capacitor C51. The binarization unit IC51 is connected to the resistor R52. The CPU <NUM> is connected to the binarization unit IC51. The capacitor C52 is connected between the resistor R52 and the binarization unit IC51. The capacitor C52 is connected to the ground.

The capacitor C61 is connected to a terminal a of a relay <NUM>. That is, the capacitor C61 is connected to the power supply line. The resistor R61 is connected to the capacitor C61. Furthermore, the resistor R61 is connected to the application unit <NUM>. The resistor R62 is connected between the resistor R61 and the capacitor C61. The binarization unit IC61 is connected to the resistor R62. The CPU <NUM> is connected to the binarization unit IC61. The capacitor C62 is connected between the resistor R62 and the binarization unit IC61. The capacitor C62 is connected to the ground.

The capacitor C71 is connected to a terminal b of the relay <NUM>. That is, the capacitor C71 is connected to the power supply line. The resistor R71 is connected to the capacitor C71. Furthermore, the resistor R71 is connected to the application unit <NUM>. The resistor R72 is connected between the resistor R71 and the capacitor C71. The binarization unit IC71 is connected to the resistor R72. The CPU <NUM> is connected to the binarization unit IC71. The capacitor C72 is connected between the resistor R72 and the binarization unit IC71. The capacitor C72 is connected to the ground.

The resistor R33 is connected to a terminal c of the relay <NUM>. Furthermore, the resistor R33 is connected to the ground.

The capacitor C81 is connected to a terminal a of a relay <NUM>. That is, the capacitor C81 is connected to the power supply line. The resistor R81 is connected to the capacitor C81. Furthermore, the resistor R81 is connected to the application unit <NUM>. The resistor R82 is connected between the resistor R81 and the capacitor C81. The binarization unit IC81 is connected to the resistor R82. The CPU <NUM> is connected to the binarization unit IC81. The capacitor C82 is connected between the resistor R82 and the binarization unit IC81. The capacitor C82 is connected to the ground. The relay <NUM> is an example of a "first relay" in the claims.

The capacitor C91 is connected to a terminal b of the relay <NUM>. That is, the capacitor C91 is connected to the power supply line. The resistor R91 is connected to the capacitor C91. Furthermore, the resistor R91 is connected to the application unit <NUM>. The resistor R92 is connected between the resistor R91 and the capacitor C91. The binarization unit IC91 is connected to the resistor R92. The CPU <NUM> is connected to the binarization unit IC91. The capacitor C92 is connected between the resistor R92 and the binarization unit IC91. The capacitor C92 is connected to the ground.

That is, a terminal c of the relay <NUM> (<NUM>) on a first side is connected to a terminal b of the relay <NUM> (<NUM>) on a second side. In the welding detector <NUM>, the common resistor R31 (R32) is provided at the terminal c of the relay <NUM> (<NUM>) on the first side, and the capacitor C41 (C81) and the resistor R41 (R81) are provided at the terminal a of the relay <NUM> (<NUM>) on the second side. Furthermore, in the welding detector <NUM>, the capacitor C51 (C91) and the resistor R51 (R91) are provided at the terminal b of the relay <NUM> (<NUM>) on the second side, and the capacitor C11 (C21) and the resistor R11 (R21) are provided at the terminal a of the relay <NUM> (<NUM>) on the second side.

The CPU <NUM> determines whether or not the relay <NUM> (<NUM>) is welded based on signals input from the terminals a and b of the relay <NUM> (<NUM>) on the second side via 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 b of the relay <NUM> (<NUM>) on the second side in a state in which the terminal c of the relay <NUM> (<NUM>) on the first side and the terminal b of the relay <NUM> (<NUM>) on the second side are connected to each other. Furthermore, the CPU <NUM> determines whether or not the relay <NUM> (<NUM>) is welded based on signals input from the terminals a and b of the relay <NUM> (<NUM>) on the second side via 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 b of the relay <NUM> (<NUM>) on the second side, and the capacitor C11 (C21) and the resistor R11 (R21) provided at the terminal a of the relay <NUM> (<NUM>) on the second side.

As shown in <FIG>, the welding detector <NUM> detects welding of the relays <NUM>, <NUM>, <NUM>, and <NUM>. Although <FIG>, <FIG>, and <FIG> show the configuration in which the welding detector <NUM> is provided for the relays <NUM> and <NUM>, the same applies to the relays <NUM> and <NUM>. The welding detector for the relay <NUM> is the same as or similar to that of the first embodiment.

The welding detection operation for the relays <NUM> and <NUM> (<NUM> and <NUM>) by the CPU <NUM> is now described with reference to <FIG>.

A case in which the terminal a of the relay <NUM> (<NUM>) is connected to the terminal c, and the terminal a of the relay <NUM> (<NUM>) is connected to the terminal c as shown in <FIG> is described. The CPU <NUM> controls the application unit <NUM> to apply a pulse voltage. As shown in <FIG>, the terminal b of the relay <NUM> is not connected to the terminal c, and thus a voltage Vd1 (Ve1) has a first-order lag waveform due to the resistor R41 (R51), the resistor R42 (R52), and the capacitor C42 (C52). On the other hand, the terminal a of the relay <NUM> is connected to the terminal c, and thus a voltage Vc1 has a waveform (further delayed waveform) influenced by the capacitor C11 and the resistor R31 in addition to the resistor R11, the resistor R12, and the capacitor C12. There is the above difference between the terminals b and a of the relay <NUM>, and thus there is a time difference between the output of the binarization unit IC11 and the outputs of the binarization units IC41 and IC51. This time difference causes a waveform (voltage Vc2) on the side with which the relay <NUM> is conducting to be delayed with respect to a waveform (voltages Vd2 and Ve2) on the side not conducting with the relay <NUM>. From the above, it is possible to determine the connected terminal (a or b) of the relay <NUM>. Regardless of whether the terminal a or b of the relay <NUM> is connected to the terminal c, the same result is obtained because the terminal b of the relay <NUM> is not connected to the terminal c.

For example, the CPU <NUM> applies a pulse voltage from the application unit <NUM> in a state in which the relay <NUM> connects the terminal a to the terminal c to output a signal. When detecting an input of the waveform in which the voltage Vc2 is delayed with respect to the voltages Vd2 and Ve2, the CPU <NUM> determines that the relay <NUM> is normal (not welded). On the other hand, when detecting an input of the waveform in which one of the voltages Vd2 and Ve2 is delayed with respect to the voltage Vc2, the CPU <NUM> determines that the relay <NUM> is abnormal (welding has occurred).

A case in which the terminal b of the relay <NUM> (<NUM>) is connected to the terminal c, and the terminal a of the relay <NUM> (<NUM>) is connected to the terminal c as shown in <FIG> is described. The CPU <NUM> controls the application unit <NUM> to apply a pulse voltage. As shown in <FIG>, the terminal b of the relay <NUM> is not connected to the terminal c, and thus the voltage Ve1 has a first-order lag waveform due to the resistor R51, the resistor R52, and the capacitor C52. On the other hand, the terminal a of the relay <NUM> is connected to the terminal c, and thus the voltage Vd1 has a waveform (further delayed waveform) influenced by the capacitor C41 and the resistor R31 in addition to the resistor R41, the resistor R42, and the capacitor C42. There is the above difference between the terminals b and a of the relay <NUM>, and thus there is a time difference between the outputs of the binarization unit IC41 and the binarization unit IC51. This time difference causes a waveform (voltage Vd2) on the side with which the relay <NUM> is conducting to be delayed with respect to a waveform (voltage Ve2) on the side not conducting with the relay <NUM>. From the above, it is possible to determine the connected terminal (a or b) of the relay <NUM>.

For example, the CPU <NUM> applies a pulse voltage from the application unit <NUM> in a state in which the relay <NUM> connects the terminal a to the terminal c to output a signal. When detecting an input of the waveform in which the voltage Vd2 is delayed with respect to the voltages Vc2 and Ve2, the CPU <NUM> determines that the relay <NUM> is normal (not welded). On the other hand, when detecting an input of the waveform in which the voltage Ve2 is delayed with respect to the voltage Vd2, the CPU <NUM> determines that the relay <NUM> is abnormal (welding has occurred).

A case in which the terminal b of the relay <NUM> (<NUM>) is connected to the terminal c, and the terminal b of the relay <NUM> (<NUM>) is connected to the terminal c as shown in <FIG> is described. The CPU <NUM> controls the application unit <NUM> to apply a pulse voltage. As shown in <FIG>, the terminal a of the relay <NUM> is not connected to the terminal c, and thus the voltage Vd1 has a first-order lag waveform due to the resistor R41, the resistor R42, and the capacitor C42. On the other hand, the terminal b of the relay <NUM> is connected to the terminal c, and thus the voltage Ve1 has a waveform (further delayed waveform) influenced by the capacitor C51 and the resistor R31 in addition to the resistor R51, the resistor R52, and the capacitor C52. There is the above difference between the terminals a and b of the relay <NUM>, and thus there is a time difference between the outputs of the binarization unit IC41 and the binarization unit IC51. This time difference causes a waveform (voltage Ve2) on the side with which the relay <NUM> is conducting to be delayed with respect to a waveform (voltage Vd2) on the side not conducting with the relay <NUM>. From the above, it is possible to determine the connected terminal (a or b) of the relay <NUM>.

For example, the CPU <NUM> applies a pulse voltage from the application unit <NUM> in a state in which the relay <NUM> connects the terminal b to the terminal c to output a signal. When detecting an input of the waveform in which the voltage Ve2 is delayed with respect to the voltages Vc2 and Vd2, the CPU <NUM> determines that the relay <NUM> is normal (not welded). On the other hand, when detecting an input of the waveform in which the voltage Vd2 is delayed with respect to the voltage Ve2, the CPU <NUM> determines that the relay <NUM> is abnormal (welding has occurred).

The remaining configurations of the second embodiment are similar to those of the first embodiment.

According to the second embodiment, similarly to the first embodiment, a decrease in the reliability of the determiner (CPU <NUM>) that determines whether or not the relay <NUM> (<NUM> to <NUM>) is welded can be significantly reduced or prevented.

According to the second embodiment, as described above, the CPU <NUM> determines whether or not the relay <NUM> (<NUM>) is welded based on the signals input from the terminals a and b of the relay <NUM> (<NUM>) on the second side via 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 b of the relay <NUM> (<NUM>) on the second side, and the capacitor C11 (C21) and the resistor R11 (R21) provided at the terminal a of the relay <NUM> (<NUM>) on the second side. Accordingly, the common resistor R31 (R32) can be provided for the relay <NUM> (<NUM>) and the relay <NUM> (<NUM>), and thus it is not necessary to separately provide resistors for the relay <NUM> (<NUM>) and the relay <NUM> (<NUM>). Furthermore, the three capacitors C11, C41, and C51 (C21, C81, and C91) and the three resistors R11, R41, and R51 (R21, R81, and R91) are provided for the terminals a and b of the relay <NUM> (<NUM>) and the terminals a and b of the relay <NUM> (<NUM>), and thus it is not necessary to separately provide four capacitors and four resistors for the terminals a and b of the relay <NUM> (<NUM>) and the terminals a and b of the relay <NUM> (<NUM>). Thus, an increase in the number of components of the welding detector <NUM> can be significantly reduced or prevented, and the circuit configuration of the welding detector <NUM> can be simplified.

The remaining advantageous effects of the second embodiment are similar to those of the first embodiment.

The embodiments disclosed above must be considered as illustrative and not restrictive. The scope of the present invention is not shown by the above description of the embodiments but is defined by the claims.

For example, while the power conversion device is mounted on the electric vehicle in each of the aforementioned first and second embodiments, the present invention is not restricted to this. For example, the power conversion device may alternatively be mounted on a hybrid vehicle driven by electricity and an engine or a fuel-cell vehicle that generates power by a fuel cell. Furthermore, the power conversion device may alternatively be mounted on a train.

While the power conversion device includes a plurality of relays, and the welding detector that detects welding of the plurality of relays is provided in each of the aforementioned first and second embodiments, the present invention is not restricted to this. In the present invention, a welding detector that detects welding of some of the plurality of relays may alternatively be provided.

While welding of the relays that switch connection destinations is detected in each of the aforementioned first and second embodiments, the present invention is not restricted to this. In the present invention, welding of each relay that switches between an on-state and an off-state may alternatively be detected. In this case, with each relay turned on, the time length of a signal based on application of an inspection signal by an application unit may be detected, it may be detected that the relay is in the on-state when the time length of the signal is longer than a threshold (when the delay is large), and it may be detected that the relay is in the off-state when the time length of the signal is shorter than the threshold (when the delay is small).

While welding of the relays that select one from two connection destinations and switch connection destinations is detected in each of the aforementioned first and second embodiments, the present invention is not restricted to this. In the present invention, welding of each relay that selects one from three or more connection destinations and switches a connection destination may alternatively be detected.

Claim 1:
A power conversion device (<NUM>) configured to be mounted on a vehicle (<NUM>), the power conversion device (<NUM>) comprising:
a power converter (<NUM>, <NUM>) configured to convert power supplied to the vehicle (<NUM>);
a relay (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) provided in a power supply line connected to the power converter; and
a welding detector (<NUM>) configured to detect welding of the relay;
wherein the welding detector includes:
a first resistor (R301, R31, R32, R33) connected to a terminal of the relay on a first side; characterised in that the welding detector further includes:
a capacitor (C101, C201, C11, C21, C41, C51, C61, C71, C81, C91) and a second resistor (R101, R201, R11, R21, R41, R51, R61, R71, R81, R91), both of which are connected to a terminal of the relay on a second side;
an application unit (<NUM>) configured to apply an inspection signal to the relay via the capacitor and the second resistor; and
a determiner (<NUM>) connected between the capacitor and the second resistor, the determiner configured to detect a signal based on application of the inspection signal by the application unit to determine whether or not the relay is welded;
and wherein the relay includes, on the second side, a first terminal and a second terminal, and the relay is configured to switch a terminal connected to the terminal on the first side between the first terminal and the second terminal.