CN109075705B

CN109075705B - Charger for vehicle

Info

Publication number: CN109075705B
Application number: CN201680084472.7A
Authority: CN
Inventors: 大林雄一郎
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2016-04-15
Filing date: 2016-04-15
Publication date: 2020-09-01
Anticipated expiration: 2036-04-15
Also published as: JPWO2017179200A1; DE112016006573T5; WO2017179200A1; JP6362812B2; CN109075705A

Abstract

The invention provides an on-vehicle charger capable of finding out the fault of a direct current converter as soon as possible and inhibiting the secondary fault caused by overcurrent. An in-vehicle charger (100) is provided with: a DC/DC converter (16) having a switching output circuit (12); and a control unit (17) that can freely switch between a switching mode that executes an output operation by the switching output circuit (12) and a failure determination mode that determines whether there is a failure in the switching output circuit (12) in a state in which the output operation is stopped, wherein, when charging of a drive battery (4) provided in the vehicle (2) is started, the control unit operates in the failure determination mode earlier than the switching mode, and switches to the switching mode when it is determined that there is no failure in the switching output circuit (12).

Description

Charger for vehicle

Technical Field

The present invention relates to a vehicle-mounted charger.

Background

Converters, so-called "inverters", have been developed which convert direct current into alternating current. The inverter uses a so-called "switching output circuit" that has a plurality of switching elements and turns on and off an output in accordance with on and off of the switching elements.

In general, when a short-circuit fault occurs in any of a plurality of switching elements included in a switching output circuit, an overcurrent flows into the switching output circuit. Due to the overcurrent, the temperature of the other switching element in which the short-circuit failure has not occurred rises, and a short-circuit failure, that is, a secondary failure, of the other switching element occurs. Patent document 1 discloses a technique for detecting and displaying an overcurrent flowing to a switching element in an inverter.

Documents of the prior art

Patent document

Patent document 1:

japanese patent laid-open No. Hei 10-215578

Disclosure of Invention

Technical problem to be solved by the invention

In Electric vehicles such as EVs (Electric vehicles), HEVs (Hybrid Electric vehicles), PHEVs (Plug-in Hybrid Electric vehicles), and the like, a Charger, so-called "OBC (On Board Charger"), is mounted, which charges a battery for driving by an external power source such as a household power source or a dedicated charging station. The OBC includes a converter (hereinafter referred to as a "dc-dc converter") that converts dc power into dc power. When the external power source is an ac power source, the OBC includes a converter (hereinafter, referred to as an "ac-dc converter") for converting ac power into dc power.

The dc-dc converter for OBC uses a switching output circuit similar to the inverter. Specifically, for example, a bridge circuit including 4 switching elements, that is, a so-called "full bridge circuit" is used. In addition, for example, a bridge circuit including 2 switching elements, that is, a so-called "half-bridge circuit" is used. The dc-dc converter for OBC is provided with a circuit for detecting an overcurrent flowing through these switching output circuits.

Since the OBC is an important component in a charging system of an electric vehicle, reliable detection of a fault is required. On the other hand, since OBC conversion costs are high, it is required to prevent false detection of a failure. Therefore, in the conventional OBC, when an overcurrent is detected in a switching output circuit of the dc-dc converter, the charging operation is once stopped and then restarted, and when the overcurrent is continuously detected a predetermined number of times (for example, 3 times), it is determined that the dc-dc converter has failed. This prevents the dc-dc converter from being erroneously determined to be faulty when the cause of the overcurrent is temporary, that is, when the dc-dc converter is not faulty, and also determines that the dc-dc converter is faulty when the cause of the overcurrent is a short-circuit fault in the switching element.

Here, when the dc/dc converter for OBC starts charging the drive battery, the initial value of the duty ratio of the output operation by the switching output circuit is set to a small value (for example, several%) and then the value of the duty ratio is set to a gradually large value, from the viewpoint of stabilizing the charging operation immediately after the start of charging. Since each of the on times of several tens to several hundreds of times after the start of charging is short, even if an overcurrent flows to the switching output circuit, the overcurrent cannot be detected.

That is, in the conventional OBC, when a short-circuit failure occurs in any one of a plurality of switching elements included in a switching output circuit of a dc-dc converter, there is a problem that: it takes time until it is determined that the dc-dc converter has failed by detecting the overcurrent a predetermined number of times, and the failure of the dc-dc converter cannot be detected as soon as possible. In addition, during this time, an overcurrent corresponding to the number obtained by multiplying a predetermined number by several tens to several hundreds of times flows to the switching output circuit of the dc-dc converter. This overcurrent causes a temperature rise in another switching element in which a short-circuit failure has not occurred, and thus has a problem in that a secondary failure occurs.

The present invention has been made to solve the above-described problems, and an object of the present invention is to detect a failure of a dc/dc converter as early as possible in an in-vehicle charger and suppress a secondary failure caused by an overcurrent.

Technical scheme for solving technical problem

The charger for vehicle of the invention includes: a DC-DC converter having a switching output circuit; and a control unit that freely switches a switching mode that performs an output operation by the switching output circuit and a failure determination mode that determines whether or not there is a failure in the switching output circuit in a state in which the output operation is stopped, operates in the failure determination mode earlier than the switching mode when charging of a drive battery provided in the vehicle is started, switches to the switching mode when it is determined that there is no failure in the switching output circuit, and switches from the switching mode to the failure determination mode when an abnormal state of the switching output circuit is detected in the operation performed in the switching mode to determine whether or not there is a failure in the switching output circuit.

Effects of the invention

The on-vehicle charger of the present invention has a failure determination mode independent of the switching mode, and operates in the failure determination mode prior to the switching mode when starting charging of the drive battery. Thus, a failure of the DC/DC converter is detected as early as possible, and a secondary failure due to an overcurrent is suppressed.

Drawings

Fig. 1 is an explanatory diagram showing a main part of an in-vehicle charger according to embodiment 1 of the present invention.

Fig. 2 is an explanatory diagram showing a main part of a switching output circuit and a control unit according to embodiment 1 of the present invention.

Fig. 3A is a flowchart showing the operation of the control unit according to embodiment 1 of the present invention.

Fig. 3B is a flowchart showing the operation of the control unit according to embodiment 1 of the present invention.

Fig. 3C is a flowchart showing the operation of the control unit according to embodiment 1 of the present invention.

Fig. 4 is a timing chart showing an example of an operation in a case where a short-circuit fault does not occur in the switching element during the operation of the switching output circuit and the control unit according to embodiment 1 of the present invention.

Fig. 5 is a timing chart showing an example of an operation in the case where a short-circuit fault occurs in the switching element during the operations of the switching output circuit and the control unit according to embodiment 1 of the present invention.

Fig. 6 is a flowchart showing the operation of the control unit according to embodiment 2 of the present invention.

Fig. 7 is a timing chart showing an example of an operation in a case where a short-circuit fault does not occur in the switching element during the operation of the switching output circuit and the control unit according to embodiment 2 of the present invention.

Fig. 8 is a timing chart showing an example of an operation in a case where a short-circuit fault occurs in a switching element during operations of the switching output circuit and the control unit according to embodiment 2 of the present invention.

Detailed Description

Hereinafter, embodiments for carrying out the present invention will be described in more detail with reference to the accompanying drawings.

Embodiment mode 1

Fig. 1 is an explanatory diagram showing a main part of an in-vehicle charger according to embodiment 1 of the present invention. Referring to fig. 1, an in-vehicle charger 100 according to embodiment 1 will be described.

In the figure, 1 is an external power supply. The external power supply 1 is constituted by an ac power supply. Specifically, the external power supply 1 is constituted by, for example, a household power supply or a dedicated charging station.

The vehicle 2 is formed of an electric vehicle such as an EV, HEV, or PHEV. The vehicle 2 includes a charging terminal 3 to which the external power supply 1 is freely connected, and a driving battery 4. The driving battery 4 is constituted by, for example, a lithium ion secondary battery or a nickel hydrogen secondary battery.

An ac/dc converter 11 is provided between the charging terminal 3 and the driving battery 4. The AC/DC converter 11 is constituted by, for example, an AC/DC converter using a full-bridge circuit, so-called "full-bridge AC/DC converter".

A switching output circuit 12, a transformer circuit 13, a rectifier circuit 14, and a filter circuit 15 are connected in this order between the ac/dc converter 11 and the driving battery 4. The dc/dc converter 16 includes a switching output circuit 12, a transformer circuit 13, a rectifier circuit 14, and a filter circuit 15. Further, a control unit 17 for the switching output circuit 12 is provided.

The switching output circuit 12 is constituted by, for example, a full-bridge circuit. The transformer circuit 13 is constituted by, for example, a transformer in which a primary winding and a secondary winding are wound around an iron core. The rectifier circuit 14 is formed of, for example, a diode. The filter circuit 15 is constituted by, for example, an LC filter including a coil (L) formed by winding a coil around a core and an electric storage device (C). That is, the DC/DC converter 16 is a so-called "full-bridge type DC/DC converter". The control unit 17 is constituted by a Processor such as a microcontroller or a DSP (Digital signal Processor).

The main parts of the in-vehicle charger 100 are constituted by an ac/dc converter 11, a dc/dc converter 16, and a controller 17. The in-vehicle charger 100 is an OBC, which is mounted on the vehicle 2 and charges the drive battery 4 using the external power supply 1.

Next, the switching output circuit 12 and the control unit 17 will be described with reference to fig. 2.

The full-bridge circuit 21 includes 4 switching elements Q1 to Q4. Each of the switching elements Q1 to Q4 is formed of an N-channel MOSFET (Metal-oxide-semiconductor Field Effect Transistor).

The drive circuit 22 sets the switching elements Q1 to Q4 to an on state by supplying a drive voltage of a predetermined value (for example, 5V) to the gate terminals of the switching elements Q1 to Q4 in accordance with a drive signal input from the control unit 17. The drive circuit 22 stops supplying the drive voltage, thereby setting the switching elements Q1 to Q4 to the off state.

The current detection circuit 23 detects a current value of the current flowing to the full bridge circuit 21. The current detection circuit 23 is formed by, for example, a current transformer in which a primary winding and a secondary winding are wound around a core.

The overcurrent detection circuit 24 detects an overcurrent flowing to the full-bridge circuit 21. That is, the overcurrent detection circuit 24 is preset with a threshold value to be compared with the current value detected by the current detection circuit 23. The overcurrent detection circuit 24 compares the current value detected by the current detection circuit 23 with a threshold value. When the current value exceeds the threshold value, the overcurrent detection circuit 24 outputs a signal indicating this to the control unit 17, and outputs a gate cut signal to the drive circuit 22. The overcurrent detection circuit 24 is constituted by a comparator using an operational amplifier, for example.

When the gate-off signal is input from the overcurrent detection circuit 24, the drive circuit 22 stops supplying the drive voltage to all of the switching elements Q1 to Q4 regardless of whether the drive signal is input from the control unit 17.

The switching output circuit 12 is mainly composed of a full-bridge circuit 21, a drive circuit 22, a current detection circuit 23, and an overcurrent detection circuit 24.

Here, dc/dc converter 16 has 4 operation modes, i.e., a charge start mode, a switching mode, a charge stop mode, and a failure determination mode.

The charge start mode is an operation mode that is set first each time charging of the drive battery 4 is started. In the charge start mode, the drive circuit 22 stops supplying the drive voltage to all the switching elements Q1 to Q4.

The switching mode is an operation mode in which the driving battery 4 is charged by performing an output operation (hereinafter, may be simply referred to as an "output operation") by the switching output circuit 12. In the switching mode, the drive circuit 22 alternately supplies a drive voltage to 2 switching elements Q2 and Q3 among the 4 switching elements Q1 to Q4 included in the full bridge circuit 21 and the remaining switching elements Q1 and Q4. The cycle of the output operation in the switching mode is set to 13 microseconds, for example.

The switching mode includes a slow start mode in which the duty ratio gradually increases in the output operation, and a steady switching mode in which the duty ratio is switched from the slow start mode and the duty ratio is a fixed value. For example, the lower limit value (i.e., the initial value) of the duty ratio in the slow start mode is set to a value greater than 0% and less than 10%, and the upper limit value (i.e., the final value) is set to a value greater than 40% and less than 50%. The duty ratio in the steady switching mode is set to a value equivalent to the upper limit value in the slow start mode.

The charge stop mode is an operation mode for stopping charging of the drive battery 4. In the charge stop mode, the drive circuit 22 stops supplying the drive voltage to all of the switching elements Q1 to Q4.

The failure determination mode is an operation mode for determining whether or not there is a failure in the switching output circuit 12 in a state where the output operation is stopped. Specifically, for example, it is determined whether or not there is a short-circuit failure in 2 switching elements Q1 and Q3 connected to the high potential side among 4 switching elements Q1 to Q4 included in the full-bridge circuit 21, and it is determined whether or not there is a short-circuit failure in 2 switching elements Q2 and Q4 connected to the low potential side among 4 switching elements Q1 to Q4 included in the full-bridge circuit 21.

That is, in the failure determination mode, the drive circuit 22 alternately supplies the drive voltage to the switching elements Q2, Q4 on the low potential side and the switching elements Q1, Q3 on the high potential side once. When the overcurrent detection circuit 24 detects an overcurrent when the drive voltage is supplied to the switching elements Q2 and Q4 on the low potential side, it is determined that a short-circuit fault has occurred in at least one of the switching elements Q1 and Q3 on the high potential side. When the overcurrent detection circuit 24 detects an overcurrent when the drive voltage is supplied to the high-potential-side switching elements Q1, Q3, it is determined that a short-circuit fault has occurred in at least one of the low-potential-side switching elements Q2, Q4.

Here, when an overcurrent flows to the full-bridge circuit 21 due to a short-circuit failure occurring in any of the switching elements Q1 to Q4, the on time of each of the switching elements Q1 to Q4 in the failure determination mode is set to a large value to the extent that the overcurrent can be detected by the overcurrent detection circuit 24. The on time is set to a small value, which is equal to or less than a predetermined reference value, of the temperature increase values of the switching elements Q1 to Q4 caused by the overcurrent in the failure determination mode for a predetermined number of times (for example, 3 times). The reference value is obtained by subtracting a predicted value or a measured value of the ambient temperature in the in-vehicle charger 100 during charging from an upper limit value (for example, 150 degrees to 175 degrees) of the heat-resistant temperature of the switching elements Q1 to Q4. Specifically, for example, the on time of the low-side switching devices Q2 and Q4 is set to 50 milliseconds, and the on time of the high-side switching devices Q1 and Q3 is also set to 50 milliseconds.

Operation mode setting unit 31 sets the operation mode of dc/dc converter 16. The drive signal output unit 32 outputs drive signals corresponding to the respective switching elements Q1 to Q4 to the drive circuit 22 at a timing corresponding to the operation mode set by the operation mode setting unit 31.

When starting charging of the drive battery 4, the operation mode setting unit 31 first sets the operation mode of the dc/dc converter 16 to the charge start mode, and then switches to the failure determination mode. When it is determined in the failure determination mode that there is no failure in the switching output circuit 12, the operation mode setting unit 31 switches the operation mode to the switching mode.

During the operation in the switching mode, the abnormality detector 33 monitors the output of the overcurrent detection circuit 24 and detects an abnormal state of the switching output circuit 12. The abnormal state is a state in which an overcurrent flows to the full bridge circuit 21.

When abnormality detection unit 33 detects an abnormal state, operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the switching mode to the charge stop mode, and then switches the operation mode to the charge start mode and the failure determination mode in this order.

During the operation in the failure determination mode, the failure determination unit 34 monitors the output of the overcurrent detection circuit 24 and determines whether or not there is a failure in the switch output circuit 12. Specifically, for example, when an overcurrent is detected when the drive signals corresponding to the low-potential-side switching elements Q2 and Q4 are output, the failure determination unit 34 determines that a short-circuit failure has occurred in at least one of the high-potential-side switching elements Q1 and Q3. When an overcurrent is detected when the drive signals corresponding to the high-side switching elements Q1 and Q3 are output, the fault determination unit 34 determines that a short-circuit fault has occurred in at least one of the low-side switching elements Q2 and Q4.

When the failure determination unit 34 determines that a short-circuit failure has occurred in at least one of the high-side switching devices Q1, Q3 and the low-side switching devices Q2, Q4, the operation mode setting unit 31 switches the operation mode of the dc/dc converter 16 from the failure determination mode to the charge stop mode. When the failure determination unit 34 determines that the short-circuit failure has continuously occurred for at least one of the high-side switching devices Q1 and Q3 and the low-side switching devices Q2 and Q4 a predetermined number of times (for example, 3 times), the operation mode setting unit 31 fixes the operation mode of the dc/dc converter 16 to the charge stop mode and does not change the operation mode thereafter. At this time, operation mode setting unit 31 issues an instruction to failure signal transmitting unit 35 to transmit a signal indicating that in-vehicle charger 100 has failed (hereinafter referred to as a "failure signal").

The failure signal transmitting unit 35 transmits a failure signal to an external device not shown. The external device is, for example, a control device for an instrument panel provided in the vehicle 2. Upon receiving the failure signal, the control device turns on a warning lamp provided in the instrument panel, the warning lamp indicating that the charging system of the drive battery 4 has failed.

The main part of the control unit 17 is constituted by an operation mode setting unit 31, a drive signal output unit 32, an abnormality detection unit 33, a failure determination unit 34, and a failure signal transmission unit 35.

Next, the operation of the control unit 17 will be described mainly with reference to the flowchart of fig. 3, with the operations of the operation mode setting unit 31, the abnormality detection unit 33, the failure determination unit 34, and the failure signal transmission unit 35 being described. The number of failure determinations by the failure determination unit 34, which is a reference for fixing the operation mode and transmitting the failure signal, is set to 3. When the charging terminal 3 is connected to the external power supply 1 or when the start of charging of the driving battery 4 is instructed by an operation of an input device not shown, the control unit 17 starts the process of step ST 1.

First, in step ST1, operation mode setting unit 31 sets the operation mode of dc/dc converter 16 to the charge start mode. Next, in step ST2, operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the charge start mode to the failure determination mode. Further, operation mode setting unit 31 notifies failure determination unit 34 of the switching to the failure determination mode. The operation mode setting unit 31 notifies the failure determination unit 34 of the timing at which the drive signals corresponding to the low-potential-side switching elements Q2, Q4 are output and the timing at which the drive signals corresponding to the high-potential-side switching elements Q1, Q3 are output.

Next, in step ST3, during the operation in the failure determination mode, the failure determination unit 34 monitors the output of the overcurrent detection circuit 24 and determines whether or not there is a failure in the switch output circuit 12. That is, the failure determination unit 34 determines whether or not a short-circuit failure has occurred in the high-side switching devices Q1, Q3, and also determines whether or not a short-circuit failure has occurred in the low-side switching devices Q2, Q4. Failure determination unit 34 outputs the determination result to operation mode setting unit 31.

When it is determined by the failure determination unit 34 that a short-circuit failure has occurred in at least one of the high-side switching elements Q1, Q3 and the low-side switching elements Q2, Q4 (yes at step ST 3), the operation mode setting unit 31 switches the operation mode of the dc/dc converter 16 from the failure determination mode to the charge stop mode at step ST 4.

Next, at step ST5, operation mode setting unit 31 refers to the determination result of failure determination unit 34 at step ST3 the last 3 times. When the failure determination unit 34 determines that the number of times of short-circuit failure occurrence in the high-side switching elements Q1, Q3 is less than 3 times and that the number of times of short-circuit failure occurrence in the low-side switching elements Q2, Q4 is less than 3 times (no in step ST 5), the operation mode setting unit 31 returns to step ST1 to set the operation mode of the dc/dc converter 16 to the charge start mode.

On the other hand, when the failure determination unit 34 determines that the number of times of short-circuit failure has occurred in at least one of the high-side switching elements Q1 and Q3 and the low-side switching elements Q2 and Q4 is 3 or more (yes in step ST 5), the operation mode setting unit 31 fixes the operation mode of the dc/dc converter 16 to the charge stop mode in step ST 6. Further, the operation mode setting unit 31 gives an instruction to transmit a failure signal to the failure signal transmitting unit 35.

Next, in step ST7, the failure signal transmitting unit 35 transmits a failure signal to the external device.

When it is determined by the failure determination unit 34 that the short-circuit failure has not occurred in any of the high-side switching elements Q1 and Q3 and the low-side switching elements Q2 and Q4 (no in step ST 3), the operation mode setting unit 31 switches the operation mode of the dc/dc converter 16 from the failure determination mode to the slow start mode in step ST 11. Further, the operation mode setting unit 31 notifies the abnormality detection unit 33 of the switching to the switching mode.

Next, in step ST12, the abnormality detection unit 33 monitors the output of the overcurrent detection circuit 24 during the operation by the slow start. When detecting an abnormal state of the switch output circuit 12, that is, a state in which an overcurrent flows to the full-bridge circuit 21 (yes in step ST 12), the abnormality detector 33 notifies the operation mode setting unit 31 of the abnormality.

Upon receiving the notification at step ST12, operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the slow start mode to the charge stop mode at step ST 13. Next, the operation mode setting unit 31 returns to step ST1 to set the dc/dc converter 16 to the charge start mode.

On the other hand, when the slow start mode is ended without receiving the notification of the detection of the abnormal state (no in step ST 12), in step ST21, operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the slow start mode to the steady switch mode.

Next, in step ST22, the abnormality detector 33 monitors the output of the overcurrent detection circuit 24 during the operation in the steady switching mode. When detecting an abnormal state of the switch output circuit 12, that is, a state in which an overcurrent flows to the full-bridge circuit 21 (yes in step ST 22), the abnormality detector 33 notifies the operation mode setting unit 31 of the abnormality.

Upon receiving the notification at step ST22, operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the steady switching mode to the charge stop mode at step ST 23. Next, the operation mode setting unit 31 returns to step ST1 to set the dc/dc converter 16 to the charge start mode.

On the other hand, if the steady switch mode is ended without receiving the notification of the detection of the abnormal state (no in step ST 22), the control unit 17 ends the processing. The stationary switching mode is terminated when the charging of the driving battery 4 is completed, when the connection between the charging terminal 3 and the external power supply 1 is released, or when the end of the charging of the driving battery 4 is instructed by an operation of an input device, not shown.

Next, an example of detailed operations of the switching output circuit 12 and the control unit 17 will be described with reference to fig. 4 and 5.

Fig. 4 is a timing chart showing drive signals corresponding to the switching elements Q1 to Q4, on/off states of the switching elements Q1 to Q4, flags indicating the determination result obtained by the failure determination unit 34, and a gate-off signal in the case where no short-circuit failure occurs in any of the switching elements Q1 to Q4.

First, operation mode setting unit 31 sets the operation mode of dc/dc converter 16 to the charge start mode. In the charge start mode, the drive signal output section 32 stops outputting the drive signals corresponding to all of the switching elements Q1 to Q4. Therefore, the supply of the drive voltage to all of the switching elements Q1 to Q4 is stopped, and all of the switching elements Q1 to Q4 are in the off state.

Next, operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the charge start mode to the failure determination mode. In the failure determination mode, the drive signal output unit 32 first outputs drive signals corresponding to the switching elements Q2, Q4 on the low potential side, and then outputs drive signals corresponding to the switching elements Q1, Q3 on the high potential side. In accordance with the drive signal, the drive voltage is first supplied to the switching elements Q2, Q4, and then to the switching elements Q1, Q3. As a result, the switching elements Q2 and Q4 are turned on first, and then the switching elements Q1 and Q3 are turned on. The on times of the switching elements Q2 and Q4 and the on times of the switching elements Q1 and Q3 are set to 50 milliseconds.

Since no short-circuit fault occurs in any of the switching elements Q1 to Q4, an overcurrent does not flow to the full-bridge circuit 21, and the overcurrent is not detected by the overcurrent detection circuit 24. As a result, the failure determination unit 34 determines that there is no failure in the switch output circuit 12. Operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the failure determination mode to the slow start mode.

In the slow start mode, the drive signal output section 32 alternately outputs drive signals corresponding to 2 switching elements Q2, Q3 and drive signals corresponding to the remaining switching elements Q1, Q4. The switching elements Q2, Q3 and the switching elements Q1, Q4 are alternately supplied with a drive voltage in accordance with a drive signal. As a result, the switching elements Q2, Q3 and the switching elements Q1, Q4 are alternately brought into the on state. Thereby, the output operation of the switching output circuit 12 is performed, and the drive battery 4 is charged.

In the slow start mode, the period of the output operation is set to 13 μ sec. The lower limit value (i.e., the initial value) of the duty ratio of the output operation is set to a value greater than 0% and less than 10%, specifically 1%, and the upper limit value (i.e., the final value) is set to a value greater than 40% and less than 50%, specifically 48%. In the slow start mode, the on/off operation is repeated over, for example, several hundred cycles while gradually increasing the duty ratio within a set range. For simplicity and ease of description, fig. 4 shows that the duty ratio rapidly increases over 3 cycles.

When the slow start mode is completed, the control unit 17 then switches the operation mode of the dc/dc converter unit 16 from the slow start mode to the steady switch mode. The cycle of the output operation in the steady switching mode is set to a value (13 μ sec) equivalent to that in the slow start mode. The duty ratio in the steady switching mode is set to a value (48%) equivalent to the upper limit value in the slow start mode.

Fig. 5 is a timing chart showing drive signals corresponding to the switching elements Q1 to Q4, on/off states of the switching elements Q1 to Q4, flags indicating a determination result by the failure determination unit 34, and a gate-off signal in the case where a short-circuit failure has occurred in the switching element Q2.

First, operation mode setting unit 31 sets the operation mode of dc/dc converter 16 to the charge start mode. Next, operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the charge start mode to the failure determination mode.

At this time, since a short-circuit fault occurs in the switching element Q2, the switching element Q2 becomes equivalent to a state of being always on regardless of whether the driving voltage is supplied. Therefore, when the drive signal output unit 32 outputs the drive signals corresponding to the switching elements Q1 and Q3, an overcurrent flows to the switching element Q1 which is turned on by the supply of the drive voltage and the switching element Q2 in which the short-circuit failure has occurred. The overcurrent detection circuit 24 detects the overcurrent and outputs a gate cut signal to the drive circuit 22. As a result, the drive circuit 22 stops supplying the drive voltage to the switching elements Q1 and Q3, and the switching elements Q1 and Q3 are turned off. The failure determination unit 34 turns on the flag of the determination result, and determines that a short-circuit failure has occurred in at least one of the switching elements Q2 and Q4 on the low potential side.

Thus, when the short-circuit fault occurs in the switching element Q2, the overcurrent detection circuit 24 outputs the gate cut-off signal, so that the time during which the overcurrent flows to the other switching element Q1 can be made shorter than the predetermined on time (50 msec) in each fault determination mode. This can suppress a temperature rise of the switching element Q1, and more reliably prevent occurrence of a secondary failure.

Next, operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the failure determination mode to the charge stop mode. At this time, the operation mode setting unit 31 resets the flag of the failure determination unit 34. Then, operation mode setting unit 31 sequentially switches the operation mode of dc/dc converter 16 to the charge start mode and the failure determination mode. When the operation mode is switched to the charge start mode, operation mode setting unit 31 cancels the output of the gate cut signal obtained by overcurrent detection circuit 24. In fig. 1, a connection line between operation mode setting unit 31 and overcurrent detection circuit 24 is not shown.

Next, an effect of the in-vehicle charger 100 according to embodiment 1 will be described.

The conventional in-vehicle charger does not have an operation mode corresponding to the failure determination mode of embodiment 1, and when an abnormal state (i.e., a state in which an overcurrent flows) is detected during the operation in the switching mode, the charging mode is switched to the switching mode again after the charging stop mode and the charging start mode. At this time, when the overcurrent is continuously detected a predetermined number of times in the switching mode, it is determined that the dc/dc converter has failed, and the operation mode is fixed to the charge stop mode and a failure signal is transmitted.

Here, the switching mode includes a slow start mode. Each on time in the second half including the first half in the slow start mode is 1% to 40% of the time corresponding to several tens of microseconds, and is shorter than the response time of a current detection circuit using a current transformer or the like. Therefore, even if a short-circuit failure occurs in any of the switching elements and an overcurrent flows, the overcurrent cannot be detected in the over half including the first half in the slow start mode.

As a result, the conventional in-vehicle charger has the following problems when a short-circuit failure occurs in any of the plurality of switching elements included in the switching output circuit of the dc/dc converter: it takes time until it is determined that the dc-dc converter has failed due to the detection of the predetermined number of times of overcurrent, and the failure of the dc-dc converter cannot be detected as soon as possible. In addition, during this time, an overcurrent corresponding to the number obtained by multiplying a predetermined number by several tens to several hundreds of times flows to the switching output circuit of the dc-dc converter. Due to this overcurrent, there are the following problems: the temperature of the other switching elements which do not have the short-circuit failure increases, and a secondary failure occurs.

In response to this problem, the in-vehicle charger 100 according to embodiment 1 has a failure determination mode different from the switching mode, and when starting charging of the drive battery 4, the in-vehicle charger operates in the failure determination mode earlier than in the switching mode. In the failure determination mode, the on time of each of the switching elements Q1 to Q4 is set to a large value to the extent that the overcurrent flowing through the full-bridge circuit 21 can be detected by the overcurrent detection circuit 24, and is set to a small value to the extent that the temperature rise value of the switching elements Q1 to Q4 due to the overcurrent is equal to or smaller than a reference value.

Thus, the overcurrent flowing through the full-bridge circuit 21 can be reduced during the period from the occurrence of the short-circuit fault in any one of the switching elements Q1 to Q4 until the fault determination unit 34 determines that the short-circuit fault has occurred a predetermined number of times (3 times), and the occurrence of a secondary fault due to the overcurrent can be suppressed. In addition, with respect to the conventional in-vehicle charger that does not have the failure determination mode, it is possible to shorten the time from when a short-circuit failure occurs in any one of the switching elements Q1 to Q4 until the failure determination unit 34 determines that a short-circuit failure has occurred a predetermined number of times (3 times), and to detect a failure of the dc/dc converter unit 16 as soon as possible.

Further, the external power supply 1 may be constituted by a direct current power supply. In this case, the in-vehicle charger 100 may be configured by the dc/dc converter 16 and the controller 17, excluding the ac/dc converter 11 shown in fig. 1.

The AC/DC converter 11 is not limited to a full-bridge AC/DC converter. The AC/DC converter 11 may be formed of, for example, an AC/DC converter using a half-bridge circuit, so-called "half-bridge AC/DC converter".

The circuit configurations of the transformer circuit 13, the rectifier circuit 14, and the filter circuit 15 are not limited to the example shown in fig. 1. Any circuit configuration may be used as long as it is a circuit configuration for transforming, rectifying, and filtering the output of the switching output circuit 12.

The switching elements Q1 to Q4 may be so-called "power semiconductors", and are not limited to N-channel MOSFETs. For the switching elements Q1 to Q4, for example, a P-channel MOSFET or an IGBT (Insulated gate bipolar transistor) can be used.

In addition, the switching output circuit 12 may be designed as a half-bridge circuit instead of the full-bridge circuit 21. That is, the DC/DC converter 16 is not limited to the full-bridge type DC/DC converter, and may be configured by a so-called "half-bridge type DC/DC converter". However, when a half-bridge circuit is used for the switching

output circuit

12, 2 switching elements are alternately turned on in the failure determination mode, similarly to the switching mode. Therefore, a circuit for stopping the output operation in the failure determination mode needs to be added to the output side of the switching output circuit 12. From the viewpoint of cost reduction by omitting such an additional circuit and coping with high power of the OBC, it is more preferable to use the full-bridge circuit 21 for the switching output circuit 12.

The current detection circuit 23 may be configured to detect a current value, and is not limited to a current transformer. The current detection circuit 23 may be formed of, for example, a shunt formed by connecting a resistor to a shunt element, or a dedicated IC (integrated circuit).

The number of failure determinations by the failure determination unit 34, which is a reference for fixing the operation mode and transmitting the failure signal, is not limited to 3. The number of times may be set to any number of times of 2 or more. From the viewpoint of more reliably preventing occurrence of the secondary failure, it is preferable to set the number of times as small as possible. In particular, when the overcurrent detection circuit 24 is configured as a circuit that does not output a gate-off signal to the drive circuit 22, it is required to reduce the number of times.

In addition, the on time of each of the switching elements Q1 to Q4 in the failure determination mode is not limited to 50 milliseconds. The on time is a large value to the extent that the overcurrent detection circuit 24 can detect the overcurrent flowing through the full-bridge circuit 21, and is a small value to the extent that the temperature rise value of the switching elements Q1 to Q4 due to the overcurrent becomes equal to or smaller than the reference value, and may be set to any value.

In addition, the period in the steady switching mode is not limited to 13 microseconds, and may be an arbitrary value. The duty ratio in the steady switching mode may be a value smaller than 50%, not limited to 48%.

The cycle in the slow start mode is not limited to 13 microseconds, and may be a value equivalent to that in the steady switch mode. The upper limit value of the duty ratio in the slow start mode may be equal to or lower than the duty ratio in the steady switching mode, and is not limited to 48%. The lower limit of the duty ratio in the slow start mode may be smaller than the upper limit, and is not limited to 1%.

As described above, the in-vehicle charger 100 according to embodiment 1 includes: a dc-dc converter 16, the dc-dc converter 16 having a switching output circuit 12; and a control unit 17, the control unit 17 being configured to freely switch between a switching mode for performing an output operation by the switching output circuit 12 and a failure determination mode for determining whether or not there is a failure in the switching output circuit 12 in a state in which the output operation is stopped, and to switch to the switching mode when it is determined that there is no failure in the switching output circuit 12, the failure determination mode being configured to operate in the failure determination mode earlier than the switching mode when charging of the drive battery 4 provided in the vehicle 2 is started. By setting the failure determination mode independent of the switching mode, the failure determination mode is operated earlier at the start of charging than the switching mode, and the failure of the dc/dc converter 16 can be detected as soon as possible. In addition, by setting the on-time of each of the switching elements Q1 to Q4 in the failure determination mode to an appropriate value, it is possible to reduce the overcurrent flowing to the full-bridge circuit 21 and suppress the occurrence of a secondary failure in the period from when a short-circuit failure occurs in any one of the switching elements Q1 to Q4 until the failure determination unit 34 determines that a short-circuit failure has occurred a predetermined number of times in the dc-dc converter 16 having the slow start mode.

When the abnormal state of the switching output circuit 12 is detected during the operation in the switching mode, the in-vehicle charger 100 switches from the switching mode to the failure determination mode to determine whether or not there is a failure in the switching output circuit 12. This can suppress the occurrence of a secondary failure due to an overcurrent as described above.

When it is determined that there is a failure in the switch output circuit 12 in the failure determination mode, the in-vehicle charger 100 switches again to the failure determination mode to determine whether there is a failure in the switch output circuit 12. Thus, when a short-circuit fault does not occur in any of the switching elements Q1 to Q4, it is possible to prevent a fault in the dc/dc converter 16 from being erroneously detected due to a short overcurrent.

In the failure determination mode, the presence or absence of a failure in the switching elements Q1 and Q3 connected to the high potential side and the presence or absence of a failure in the switching elements Q2 and Q4 connected to the low potential side among the plurality of switching elements Q1 to Q4 included in the switching output circuit 12 are determined. This makes it possible to determine whether the failure point in the switching output circuit 12 is the high-side switching elements Q1 and Q3 or the low-side switching elements Q2 and Q4.

Embodiment 2.

In the failure determination mode, the in-vehicle charger 100 according to embodiment 1 determines whether or not there is a short-circuit failure in the high-side switching devices Q1 and Q3, and determines whether or not there is a short-circuit failure in the low-side switching devices Q2 and Q4. In embodiment 2, the description will be given of the in-vehicle charger 100 for determining whether or not there is a short-circuit fault in each of the switching elements Q1 to Q4 in the fault determination mode. Since the circuit configuration and the like of the in-vehicle charger 100 according to embodiment 2 are the same as those of embodiment 1, the description will be made with reference to fig. 1 and 2. The same components as those in embodiment 1 are denoted by the same reference numerals, and description thereof is omitted.

In the failure determination mode of embodiment 2, the drive circuit 22 supplies the switching elements Q1 to Q4 with the primary drive voltages, respectively. Specifically, for example, the drive circuit 22 sequentially supplies a drive voltage to the switching element Q4, the switching element Q3, the switching element Q2, and the switching element Q1.

During the operation in the failure determination mode, the failure determination unit 34 monitors the output of the overcurrent detection circuit 24 and determines whether or not there is a failure in the switch output circuit 12. Specifically, when an overcurrent is detected when the drive signal corresponding to the switching element Q1 is output, the failure determination unit 34 determines that a short-circuit failure has occurred in the switching element Q2. When an overcurrent is detected when the drive signal corresponding to the switching element Q2 is output, the failure determination unit 34 determines that a short-circuit failure has occurred in the switching element Q1. When an overcurrent is detected when the drive signal corresponding to the switching element Q3 is output, the failure determination unit 34 determines that a short-circuit failure has occurred in the switching element Q4. When an overcurrent is detected when the drive signal corresponding to the switching element Q4 is output, the failure determination unit 34 determines that a short-circuit failure has occurred in the switching element Q3.

When failure determination unit 34 determines that a short-circuit failure has occurred in at least one of switching elements Q1 to Q4, operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the failure determination mode to the charge stop mode. When failure determination unit 34 determines that there are short-circuit failures occurring a predetermined number of consecutive times (3 times) for the same switching elements Q1 to Q4, operation mode setting unit 31 fixes the operation mode of dc/dc converter 16 to the charge stop mode, and instructs failure signal transmission unit 35 to transmit a failure signal.

Next, the operation of the control unit 17 will be described with reference to the flowchart of fig. 6. In fig. 6, the same steps as those in the flowchart of embodiment 1 shown in fig. 3A are denoted by the same reference numerals, and description thereof is omitted.

Next, in step ST2, in step ST3a, the failure determination unit 34 monitors the output of the overcurrent detection circuit 24 during the operation in the failure determination mode, and determines whether or not there is a failure in the switch output circuit 12. That is, the failure determination unit 34 determines whether or not a short-circuit failure has occurred for each of the switching elements Q1 to Q4. Failure determination unit 34 outputs the determination result to operation mode setting unit 31.

When failure determination unit 34 determines that a short-circuit failure has occurred in at least one of switching elements Q1 to Q4 (yes in step ST3 a), operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the failure determination mode to the charge stop mode in step ST 4.

Next, in step ST5a, operation mode setting unit 31 refers to the determination result of failure determination unit 34 in step ST3a last 3 times. In the following cases, the operation mode setting unit 31 returns to step ST 1: that is, it is determined by the failure determination unit 34 that the number of times of short-circuit failure occurrence in the switching element Q1 is less than 3, the number of times of short-circuit failure occurrence in the switching element Q2 is less than 3, the number of times of short-circuit failure occurrence in the switching element Q3 is less than 3, and the number of times of short-circuit failure occurrence in the switching element Q4 is less than 3 (no in step ST5 a).

On the other hand, when the failure determination unit 34 determines that the number of times of occurrence of the short-circuit failure is 3 or more with respect to at least one of the switching elements Q1 to Q4 (yes at step ST5 a), the operation mode setting unit 31 proceeds to step ST 6.

Note that, the operation when the failure determination unit 34 determines that no short-circuit failure has occurred in any of the switching elements Q1 to Q4 (no at step ST3 a) is the same as the operation described with reference to fig. 3B and 3C in embodiment 1, and therefore, illustration and description thereof are omitted.

Next, an example of detailed operations of the switching output circuit 12 and the control unit 17 will be described with reference to fig. 7 and 8.

Fig. 7 is a timing chart showing drive signals corresponding to the switching elements Q1 to Q4, on/off states of the switching elements Q1 to Q4, flags showing determination results obtained by the failure determination unit 34, and a gate-off signal in the case where no short-circuit failure occurs in any of the switching elements Q1 to Q4. Note that the timing chart in the operation mode other than the failure determination mode is the same as the timing chart in embodiment 1 shown in fig. 4, and therefore, the description thereof is omitted.

In the failure determination mode, the drive signal output section 32 first outputs a drive signal corresponding to the switching element Q4, and then sequentially outputs a drive signal corresponding to the switching element Q3, a drive signal corresponding to the switching element Q2, and a drive signal corresponding to the switching element Q1. In accordance with the drive signal, a drive voltage is sequentially supplied to the switching element Q4, the switching element Q3, the switching element Q2, and the switching element Q1. As a result, the switching element Q4, the switching element Q3, the switching element Q2, and the switching element Q1 are sequentially turned on. The on time of each of the switching elements Q1 to Q4 is set to, for example, 50 milliseconds.

Since no short-circuit fault occurs in any of the switching elements Q1 to Q4, an overcurrent does not flow to the full-bridge circuit 21, and the overcurrent is not detected by the overcurrent detection circuit 24. As a result, failure determination unit 34 determines that there is no failure in switching output circuit 12. Operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the failure determination mode to the slow start mode.

Fig. 8 is a timing chart showing drive signals corresponding to the switching elements Q1 to Q4, on/off states of the switching elements Q1 to Q4, flags showing determination results by the failure determination unit 34, and a gate-off signal in the case where a short-circuit failure has occurred in the switching element Q2. Note that the timing chart in the operation mode other than the failure determination mode is the same as the timing chart in embodiment 1 shown in fig. 5, and therefore, the description thereof is omitted.

Since a short-circuit fault occurs in the switching element Q2, the switching element Q2 is equivalent to a state in which it is always on regardless of whether a drive voltage is supplied. Therefore, in the failure determination mode, when the drive signal output unit 32 outputs the drive signal corresponding to the switching element Q1, an overcurrent flows to the switching element Q1 which is turned on by the supply of the drive voltage and the switching element Q2 in which the short-circuit failure has occurred. The overcurrent detection circuit 24 detects the overcurrent and outputs a gate cut signal to the drive circuit 22. As a result, the drive circuit 22 stops supplying the drive voltage to the switching element Q1, and turns off the switching element Q1. The failure determination unit 34 turns on the flag of the determination result, and determines that a short-circuit failure has occurred in the switching element Q2.

Next, operation mode setting unit 31 switches the operation mode of dc/dc converter 16 from the failure determination mode to the charge stop mode. At this time, the operation mode setting unit 31 resets the flag of the failure determination unit 34. Then, operation mode setting unit 31 sequentially switches the operation mode of dc/dc converter 16 to the charge start mode and the failure determination mode. When the operation mode is switched to the charge start mode, operation mode setting unit 31 cancels the output of the gate cut signal by overcurrent detection circuit 24.

Thus, the in-vehicle charger 100 according to embodiment 2 has a failure determination mode independent of the switching mode, as in the in-vehicle charger 100 according to embodiment 1, and when starting charging the drive battery 4, the in-vehicle charger operates in the failure determination mode earlier than in the switching mode. Thus, the overcurrent flowing through the full-bridge circuit 21 can be reduced during the period from the occurrence of the short-circuit fault in any one of the switching elements Q1 to Q4 until the fault determination unit 34 determines that the short-circuit fault has occurred a predetermined number of times (3 times), and the occurrence of a secondary fault due to the overcurrent can be suppressed. Further, compared to a conventional in-vehicle charger that does not have a failure determination mode, it is possible to shorten the time from when a short-circuit failure occurs in any one of the switching elements Q1 to Q4 to when the failure determination unit 34 determines that a short-circuit failure has occurred a predetermined number of times (3 times), and to detect a failure of the dc/dc converter unit 16 as soon as possible.

In addition, various modifications similar to the example described in embodiment 1 can be adopted in the in-vehicle charger 100 of embodiment 2.

As described above, the failure determination mode according to embodiment 2 determines whether or not a failure has occurred in each of the switching elements Q1 to Q4 included in the plurality of switching elements Q1 to Q4 of the switching output circuit 12. This allows the switching elements Q1 to Q4 that have failed to be identified.

In the present invention, the embodiments may be freely combined, any component of the embodiments may be modified, or any component of the embodiments may be omitted within the scope of the invention.

Industrial applicability of the invention

The charger for vehicles according to the present invention can be used for an OBC for electric vehicles.

Description of the reference symbols

1 external power supply

2 vehicle

3 charging terminal

4 drive battery

11 AC-DC converter

12 switch output circuit

13 transformation circuit

14 rectification circuit

15 filter circuit

16 DC/DC converter

17 control part

21 full bridge circuit

22 drive circuit

23 Current detection circuit

24 overcurrent detection circuit

31 operation mode setting unit

32 drive signal output part

33 abnormality detection unit

34 failure determination unit

35 fault signal transmitting part

100 charger for vehicle

Q1, Q2, Q3, Q4 switching elements

Claims

1. An in-vehicle charger, comprising:

a DC-DC converter having a switching output circuit; and

a control unit that freely switches a switching mode that executes an output operation by the switching output circuit and a failure determination mode that determines whether or not there is a failure in the switching output circuit in a state where the output operation is stopped,

when starting charging of a drive battery provided in a vehicle, the vehicle is operated in the failure determination mode more than in the switching mode, and when it is determined that there is no failure in the switching output circuit, the vehicle is switched to the switching mode,

when an abnormal state of the switching output circuit is detected in the operation performed in the switching mode, the switching mode is switched to the failure determination mode, and it is determined whether or not a failure has occurred in the switching output circuit.

2. The vehicle-mounted charger according to claim 1,

when it is determined that there is a failure in the switching output circuit in the failure determination mode, the switching is again switched to the failure determination mode, and whether there is a failure in the switching output circuit is determined.

3. The vehicle-mounted charger according to claim 1,

the failure determination mode determines whether or not a failure occurs in the switching element connected to the high potential side among the plurality of switching elements included in the switching output circuit, and determines whether or not a failure occurs in the switching element connected to the low potential side among the plurality of switching elements included in the switching output circuit.

4. The vehicle-mounted charger according to claim 1,

the failure determination mode determines whether or not a failure occurs in each of a plurality of switching elements included in the switching output circuit.

5. The vehicle-mounted charger according to claim 1,

the switching mode includes a slow start mode in which a value of a duty ratio gradually increases in the output operation, and a steady switching mode in which the switching is performed from the slow start mode and the value of the duty ratio is a fixed value.

6. The vehicle-mounted charger according to claim 5,

the lower limit value of the duty ratio in the slow start mode is set to a value greater than 0% and less than 10%, and the upper limit value is set to a value greater than 40% and less than 50%.

7. The vehicle-mounted charger according to claim 1,

in the failure determination mode, the on time of each switching element included in the switching output circuit is set to a value that can detect an overcurrent flowing to the switching output circuit and that allows a temperature rise value of the switching element due to the overcurrent to be equal to or lower than a reference value.

8. The vehicle-mounted charger according to claim 7,

the on time is set to 50 milliseconds.