Control circuit for on-board charger

Abstract

To maintain normal operation of an onboard charger.SOLUTION: A control circuit for an onboard charger is used in an onboard charger that includes a charging circuit that charges a first power storage device mounted on a vehicle with power from a main power source outside the vehicle, and an auxiliary power supply circuit that receives power from a second power storage device mounted on the vehicle and has a lower rated voltage than the first power storage device, and outputs the input power to the charging circuit after converting its voltage. When the voltage at the input terminal of the auxiliary power supply circuit to which power is input falls below a threshold, the control circuit adjusts the voltage at the input terminal such that the voltage at the input terminal is equal to or greater than a threshold, thereby maintaining normal operation of the on-board charger.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a control circuit for an on-board charger. [Background technology]

[0002] Conventionally, an overvoltage protection circuit for use in a vehicle power supply system has been proposed (see, for example, Patent Document 1). This overvoltage protection circuit includes a switching element interposed between the input terminal and output terminal of a power supply, an input voltage detection unit that detects the input voltage, and a processor that adjusts the duty value of a signal that turns the switching element on and off based on the input voltage. The processor controls the duty value of the switching element based on the input voltage detected by the input voltage detection unit so that the voltage output from the output terminal does not exceed a set value corresponding to the withstand voltage of the power supply system. In this way, the vehicle's power supply system is protected from overvoltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-291025 Summary of the Invention [Problem to be solved by the invention]

[0004] Recently, an on-board charger has been proposed that charges a first power storage device mounted on a vehicle with power from a main power supply installed outside the vehicle. The on-board charger includes a charging circuit and an auxiliary power supply circuit. The charging circuit charges the first power storage device with power from the main power supply installed outside the vehicle. The auxiliary power supply circuit receives power from a second power storage device mounted on the vehicle that has lower power than the first power storage device, converts the voltage of the input power, and outputs the power to the charging circuit. In this on-board charger, if the voltage from the auxiliary power supply drops for some reason, the voltage conversion circuit may stop, making it impossible to output power to the power supply circuit. In this case, the on-board charger may stop operating, or some abnormality may occur in the on-board charger, making it impossible to maintain normal operation of the on-board charger.

[0005] The main purpose of the control circuit for an on-board charger of the present disclosure is to maintain normal operation of the on-board charger. [Means for solving the problem]

[0006] The control circuit for an on-board charger of the present disclosure employs the following means to achieve the above-mentioned main object.

[0007] The control circuit for an on-board charger of the present disclosure includes: a charging circuit that charges a first power storage device mounted on the vehicle with electric power from a main power supply outside the vehicle; an auxiliary power supply circuit that receives power from a second power storage device that is mounted on a vehicle and has a lower rated voltage than the first power storage device, and that converts the voltage of the input power before outputting it to the charging circuit; A control circuit for an on-board charger that is used in an on-board charger and controls the auxiliary power supply circuit, When the voltage at the input terminal to which power is input in the auxiliary power supply circuit falls below a threshold, the voltage at the input terminal is adjusted so that the voltage at the input terminal becomes equal to or greater than the threshold. The gist of this is as follows.

[0008] In the control circuit for an on-board charger disclosed herein, when the voltage at the input terminal to which power is input in the auxiliary power supply circuit falls below a threshold, the voltage at the input terminal is adjusted so that the voltage at the input terminal is equal to or greater than the threshold. This prevents the voltage at the input terminal from dropping and causing the auxiliary power supply circuit to become inoperable, and allows the output of power to the charging circuit to be continued. This prevents the on-board charger from stopping or malfunctioning, and maintains normal operation of the on-board charger. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing an outline of the configuration of an on-board charger 20 including a control circuit 30 of the present embodiment. [Figure 2] 2 is a diagram showing the schematic configuration of an auxiliary power supply circuit 24 and a control circuit 30. FIG. [Figure 3] FIG. 10 is a diagram showing an outline of the configuration of an auxiliary power supply circuit 124 and a control circuit 130 according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a schematic diagram illustrating the configuration of an on-board charger 20 including a control circuit 30 according to this embodiment. FIG. 2 is a schematic diagram illustrating the configurations of an auxiliary power supply circuit 24 and the control circuit 30. The on-board charger 20 is mounted on a vehicle 10 equipped with a driving motor, and is configured as a device for charging a high-voltage battery 12 serving as a first power storage device with a high rated voltage (e.g., 400 V) that supplies power to the motor using power from an AC power source PS serving as a main power source outside the vehicle. In addition to the motor and the high-voltage battery 12, the vehicle 10 also includes a low-voltage battery 16 serving as a second power storage device with a lower rated voltage (e.g., 12 V) than the high-voltage battery 12 and that supplies power to auxiliary machinery 14. Examples of the vehicle 10 include an electric vehicle powered by the motor and a hybrid vehicle powered by both an engine and the motor. A household power source or a commercial power source is used as the AC power source PS. A lithium-ion secondary battery, a nickel-metal hydride secondary battery, or the like is used as the high-voltage battery 12. The low-voltage battery 16 may be a lead storage battery or the like.

[0011] The on-board charger 20 includes a charging circuit 22 , an auxiliary power supply circuit 24 , and a control circuit 30 .

[0012] 1, the charging circuit 22 includes an AC / DC converter that includes a power factor correction (PFC) circuit and converts AC power to DC power, and a DC / DC converter that converts the voltage of the power output from the AC / DC converter and outputs it to the high-voltage battery 12. When an external power supply side connector CNs, to which an AC power supply PS outside the vehicle is connected, is connected to a vehicle side connector CNv on the vehicle 10 side, the charging circuit 22 converts the AC power from the AC power supply PS into DC power with a voltage suitable for charging the high-voltage battery 12, and charges the high-voltage battery 12 with the converted power.

[0013] As shown in FIG. 2, the auxiliary power supply circuit 24 is configured as a flyback converter that converts voltage from power input to a power line L1 connected to the positive and negative electrodes of a capacitor C10 and outputs the converted power to power lines L2, L3, and Lfb connected to the positive and negative electrodes of capacitors C2, C3, and Cfb. The auxiliary power supply circuit 24 includes a transformer TR1, a switching element Q1, capacitors C10, C2, C3, and Cfb, diodes D2, D3, and Dfb, and a PWM control circuit 26. The switching element Q1 may be, for example, a MOSFET or an IGBT. A primary winding Co1 of the transformer TR1 and the switching element Q1 are connected in series between the positive and negative buses of the power line L1. A diode D11, a capacitor C11, and a resistor R1, which form a snubber circuit, are connected to the winding Co1. The secondary windings Co2, Co3, and Cofb of the transformer TR1 are connected to the positive and negative buses of the power lines L2, L3, and Lfb. Diodes D2, D3, and Dfb are attached to the positive buses of the power lines L2, L3, and Lfb closer to the windings Co2, Co3, and Cofb than the capacitors C2, C3, and Cfb. The power line L1 is connected to the positive bus of the power line from the low-voltage battery 16 via a diode Din and a switching element Qin. The switching element Qin may be, for example, a MOSFET or an IGBT. The gate voltage of the switching element Qin is adjusted by a gate adjustment circuit (not shown) so that it is turned on when the external power supply connector CNs and the vehicle connector CNv are connected. The power lines L2 and L3 are connected to the power line of the low-voltage system (e.g., 16 V) of the charging circuit 22. The PWM control circuit 26 receives a voltage VFB1 from the positive bus of the power line Lfb and a voltage at an input terminal VA between the switching element Qin and the winding Co1. The PWM control circuit 26 generates a PWM control signal so that the voltage VFB1 becomes the voltage at the input terminal VA, and controls the switching of the switching element Q1 using the generated PWM control signal. This suppresses fluctuations in the output on the secondary side of the transformer TR1.When the external power supply side connector CNs and the vehicle side connector CNv are connected, the auxiliary power supply circuit 24 configured in this manner functions as an auxiliary power supply that converts the power from the low-voltage battery 16 into a power supply voltage for a control circuit (not shown) built into the charging circuit 22 and a voltage (e.g., 16 V) required for the housekeeping function of the charging circuit 22 during standby, and outputs the converted voltage to the charging circuit 22.

[0014] The control circuit 30 is configured as a flyback converter that converts the voltage of power input to a power line L4 connected to the positive and negative electrodes of a capacitor C40 and outputs the converted power to a power line L5 connected to the positive and negative electrodes of a capacitor C5. As shown in FIG. 2, the control circuit 30 includes a transformer TR2, a switching element Q4, capacitors C40 and C5, diodes D42 and D5, and a PWM control circuit 32. The switching element Q4 may be, for example, a MOSFET or an IGBT. The primary winding Co4 of the transformer TR2 and the switching element Q4 are connected in series between the positive and negative bus bars of the power line L4. A snubber circuit including a diode D41, a capacitor C41, and a resistor R41 is connected to the winding Co4. The capacitor C40 is connected in parallel to the positive and negative bus bars of the power line L4. The secondary winding Co5 of the transformer TR2 has both ends connected to the positive and negative bus bars of the power line L5. Capacitor C5 is connected in parallel to the positive and negative bus bars of power line L5. Diode D5 is attached to the positive bus bar of power line L5 closer to winding Co5 than capacitor C5. Power line L4 is connected to a power line from charging circuit 22 (e.g., a power line connecting an AC / DC converter and a DC / DC converter) via diode D42. Power line L5 is connected to input terminal VA of charging circuit 22. PWM control circuit 32 receives the voltage at input terminal VA of charging circuit 22 via photocoupler FC, enable signal EN from comparator COMP, and voltage Vcc obtained by dividing the voltage of the power line from charging circuit 22 by resistors R42 and R43. Comparator COMP outputs enable signal EN, which rises, to PWM control circuit 32 when the voltage at input terminal VA is less than threshold value Vref (e.g., 13 V). The threshold value Vref is the lower limit of the voltage at which the auxiliary power supply circuit 24 can operate or a voltage slightly higher than this lower limit, and the resistors R42 and R43 are adjusted so that the voltage Vcc is equal to or higher than the threshold value Vref.The PWM control circuit 32 stops operation when the enable signal EN is rising, and controls the switching element Q4 so that the voltage at the input terminal VA is equal to or higher than the voltage Vcc, i.e., the threshold value Vref, when the enable signal EN is falling.

[0015] In the onboard charger 20 configured as described above, when the external power supply connector CNs and the vehicle connector CNv are connected, the charging circuit 22 converts AC power from the AC power supply PS into DC power with a voltage suitable for charging the high-voltage battery 12 and charges the high-voltage battery 12 with the converted power. During this charging, if the voltage from the low-voltage battery 16 drops for some reason and the voltage at the input terminal VA falls below the threshold Vref, the enable signal EN rises in the control circuit 30. When the enable signal EN rises, the PWM control circuit 32 controls the switching element Q4 to adjust the voltage at the input terminal VA so that the voltage at the input terminal VA becomes Vcc (a voltage equal to or greater than the threshold Vref). This prevents the voltage at the input terminal VA of the auxiliary power supply circuit 24 from falling below the threshold Vref, preventing the auxiliary power supply circuit 24 from becoming inoperable due to a drop in the voltage at the input terminal VA. This allows the auxiliary power supply circuit 24 to continue operating, thereby enabling the output of power to the charging circuit 22 to continue. Therefore, it is possible to prevent the occurrence of operational stoppages or abnormalities in the on-board charger 20, and to maintain normal operation of the on-board charger 20.

[0016] In the control circuit for the vehicle charger 20 of this embodiment described above, when the voltage at the input terminal VA of the auxiliary power supply circuit 24 is below the threshold Vref, the input terminal VA is adjusted so that the voltage at the input terminal VA is equal to or greater than the threshold Vref, thereby maintaining normal operation of the vehicle charger 20.

[0017] In the above-described embodiment, the auxiliary power supply circuit 24 includes a transformer TR1, and the control circuit 30 includes a transformer TR2. However, the auxiliary power supply circuit 124 and the control circuit 130 may be configured using a single transformer. FIG. 3 is a configuration diagram showing an example of the configuration of the auxiliary power supply circuit 124 and the control circuit 130 of another embodiment. In FIG. 3, the same components as those in the charging circuit 22 and the control circuit 30 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0018] The auxiliary power supply circuit 124 has the same configuration as the charging circuit 22, except that it includes a PWM control circuit 126 instead of the PWM control circuit 26, that a Zener diode ZD11 is connected to the winding Co1 instead of the capacitor C11 and the resistor R1, that the positive bus of the power line Lfb is connected to the input of the PWM control circuit 126 and the positive bus (input terminal VA) of the power line L1, and that an enable signal EN is input to the PWM control circuit 126 from the control circuit 30. The PWM control circuit 126 is configured to stop operating when the enable signal EN rises and to operate when the enable signal EN falls.

[0019] The control circuit 130 has the same configuration as the control circuit 30, except that it includes a PWM control circuit 132 instead of the PWM control circuit 32, does not include the winding Co5, diode D5, capacitor C5, and power line L5, a Zener diode ZD4 is connected to the winding Co4 instead of the capacitor C41 and resistor R41, the output of the comparator COMP is input to the PWM control circuit 126 of the charging circuit 22 as the enable signal EN, the output of the comparator COMP is input to the PWM control circuit 132 via a photocoupler FC as the enable signal EN, and the positive bus of the power line L2 is input to the PWM control circuit 132. When the PWM control circuit 126 stops operating, the control circuit 130 forms a flyback converter in combination with a secondary-side circuit formed of the winding Cofb, diode Dfb, and capacitor Cfb of the charging circuit 22. The PWM control circuit 132 is configured to operate when the enable signal EN rises and to stop operating when the enable signal EN falls. During operation, the PWM control circuit 132 generates a PWM control signal so that the voltage of the power line L2 becomes the voltage Vcc1 obtained by dividing the voltage input to the power line L4 from the charging circuit by resistors R42 and R43, and controls the switching of the switching element Q4 using the generated PWM control signal.

[0020] In the onboard charger including the auxiliary power supply circuit 124 and the control circuit 130 configured as described above, when the voltage at the input terminal VA is equal to or greater than the threshold Vref, the enable signal EN falls, causing the PWM control circuit 126 of the auxiliary power supply circuit 124 to operate and the PWM control circuit 132 of the control circuit 130 to stop operating. The PWM control circuit 126 generates a PWM control signal so that the voltage FB1 becomes the voltage at the input terminal VA and controls the switching of the switching element Q1 using the generated PWM control signal. This suppresses fluctuations in the output from the secondary side of the transformer TR1. As a result, the charging circuit 22 converts AC power from the AC power supply PS into DC power with a voltage suitable for charging the high-voltage battery 12 and charges the high-voltage battery 12 with the converted power. If the voltage from the low-voltage battery 16 drops for some reason and the voltage at the input terminal VA falls below the threshold Vref, the enable signal EN rises, causing the PWM control circuit 126 of the auxiliary power supply circuit 124 to stop operating and the PWM control circuit 132 of the control circuit 130 to operate. The PWM control circuit 132 controls the switching of the switching element Q4 so that the voltage of the power line L2 becomes equal to the voltage Vcc1 obtained by dividing the voltage of the power line L4 by resistors R42 and R43. This suppresses fluctuations in the output from the secondary side of the transformer TR1. The operation of the PWM control circuit 132 increases the voltage of the power line Lfb, preventing the voltage at the input end VA of the auxiliary power supply circuit 24 from falling below the threshold Vref. This prevents the voltage at the input end VA from dropping and causing the auxiliary power supply circuit 24 to become inoperable. This allows the auxiliary power supply circuit 24 to continue operating, allowing the output of power to the charging circuit 22 to continue. This also prevents the on-board charger 20 from stopping or becoming abnormal, maintaining normal operation of the on-board charger 20.

[0021] The above-described embodiments use the auxiliary power supply circuits 24, 124 shown in Figures 2 and 3. However, the auxiliary power supply circuit may have any circuit configuration as long as it adjusts the input terminal VA of the auxiliary power supply circuit 24 so that the voltage at the input terminal VA becomes equal to or greater than the threshold value Vref when the voltage at the input terminal VA is less than the threshold value Vref.

[0022] The correspondence between the main elements of the embodiment and the main elements of the invention described in the "Means for Solving the Problems" section will be explained below. In the embodiment, the charging circuit 22 corresponds to the "charging circuit," the auxiliary power supply circuit 24 corresponds to the "auxiliary power supply circuit," the on-board charger 20 corresponds to the "on-board charger," and the control circuit 30 corresponds to the "control circuit."

[0023] The correspondence between the main elements of the embodiments and the main elements of the invention described in the "Means for Solving the Problem" section does not limit the elements of the invention described in the "Means for Solving the Problem" section, since the embodiments are examples for specifically explaining the mode for implementing the invention described in the "Means for Solving the Problem" section. In other words, the interpretation of the invention described in the "Means for Solving the Problem" section should be based on the description in that section, and the embodiments are merely specific examples of the invention described in the "Means for Solving the Problem" section.

[0024] The above describes embodiments for implementing the present disclosure, but the present disclosure is not limited to these embodiments and can, of course, be implemented in various forms within the scope that does not deviate from the gist of the present disclosure. [Industrial Applicability]

[0025] The present disclosure is applicable to industries such as the manufacturing of control circuits for on-board chargers. [Explanation of symbols]

[0026] 10 vehicle, 12 high-voltage battery, 16 low-voltage battery, 20, 120 on-board charger, 22 charging circuit, 24, 124 auxiliary power circuit, 26, 32, 126, 132 PWM control circuit, 30, 130 control circuit.

Claims

[Claim 1] a charging circuit that charges a first power storage device mounted on the vehicle with electric power from a main power supply outside the vehicle; an auxiliary power supply circuit that receives power from a second power storage device mounted on a vehicle and having a lower rated voltage than the first power storage device, and that converts the voltage of the input power before outputting it to the charging circuit; A control circuit for an on-board charger that is used in an on-board charger and controls the auxiliary power supply circuit, When the voltage at the input terminal to which power is input in the auxiliary power supply circuit falls below a threshold, the voltage at the input terminal is adjusted so that the voltage at the input terminal becomes equal to or greater than the threshold. Control circuit for on-board charger.

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