Step-up / step-down circuit

Abstract

To provide a step-up / step-down circuit capable of reducing the charging time in cold regions.SOLUTION: The step-up / step-down circuit includes: a DC-DC converter circuit in which a first bridge circuit and a second bridge circuit are connected via a transformer; and a pass-through circuit. The step-up / step-down circuit converts the electric power into a predetermined voltage when charging an on-vehicle battery from an external power source. When charging the on-vehicle battery from the external power source, the step-up / step-down circuit connects the DC-DC converter circuit and the pass-through circuit in parallel for input and in series for output. The step-up / step-down circuit is configured to simultaneously control the boost charging, which boosts the output voltage of the external power source to the voltage of the on-vehicle battery, and the power conversion of the temperature rise operation using the internal resistance of the on-vehicle battery and set the current of the DC-DC converter circuit to the sum of the DC and AC components.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a buck-boost circuit.

Background Art

[0002] Patent Document 1 discloses a power conversion circuit in which a DCDC converter circuit in which a first bridge circuit and a second bridge circuit are connected via a transformer and a chopper circuit are connected in series.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When performing external charging from an external power source to an in-vehicle battery, a power conversion circuit is used to convert the power supplied from a rapid charging stand (DC stand) to a desired voltage and output it to the in-vehicle battery. Due to the characteristics of the in-vehicle battery, it is necessary to limit the input / output current at low temperatures, so the charging time becomes long. Therefore, the rapid charging time at low temperatures becomes long, and the charging time in cold regions becomes long. Thus, a method of heating the in-vehicle battery using an external heat source or a method of heating the in-vehicle battery by self-heating by repeatedly charging and discharging the power conversion circuit can be considered. However, since a conventional power conversion circuit cannot perform a temperature-raising operation for self-heating of the in-vehicle battery, it is necessary to provide another power conversion circuit for temperature-raising, resulting in an increase in size and cost.

[0005] The present invention has been made in view of the above circumstances, and an object thereof is to provide a buck-boost circuit capable of shortening the charging time in cold regions.

Means for Solving the Problems

[0006] The present invention is a buck-boost circuit that includes a DCDC converter circuit in which a first bridge circuit and a second bridge circuit are connected via a transformer, and a pass-through circuit, and that converts power to a predetermined voltage when charging from an external power source to an in-vehicle battery. When charging from the external power source to the in-vehicle battery, the DCDC converter circuit and the pass-through circuit are connected in input parallel and output series, and boost charging for boosting the output voltage of the external power source to the voltage of the in-vehicle battery and power conversion of a temperature-rising operation using the internal resistance of the in-vehicle battery are simultaneously controlled, and the current of the DCDC converter circuit is set to the sum of a DC component and an AC component.

Effect of the Invention

[0007] In the present invention, the charging time in a cold region can be shortened.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0009] Hereinafter, the buck-boost circuit according to an embodiment of the present invention will be specifically described. Note that the present invention is not limited to the embodiments described below.

[0010] FIG. 1 is a schematic diagram showing a buck-boost circuit according to an embodiment. The buck-boost circuit 1 includes a DCDC converter circuit 2 and a pass-through circuit 3. In the buck-boost circuit 1, the DCDC converter circuit 2 is configured in the upper stage, and the pass-through circuit 3 is configured in the lower stage. The buck-boost circuit 1 has a basic circuit structure in which the DCDC converter circuit 2 and the pass-through circuit 3 are connected in parallel at the input and in series at the output.

[0011] The DCDC converter circuit 2 is an isolated bidirectional DCDC converter circuit configured by a dual active bridge method (DAB circuit). The DCDC converter circuit 2 includes a first bridge circuit 11, a second bridge circuit 12, a transformer 13, a first smoothing capacitor C1, a second smoothing capacitor C2, and a reactor L.

[0012] The first bridge circuit 11 is a full-bridge circuit connected to one winding of the transformer 13. The first bridge circuit 11 includes four switching elements SW1 to SW4. The first bridge circuit 11 has a first upper and lower arm in which the first switching element SW1 and the second switching element SW2 are connected in series, and a second upper and lower arm in which the third switching element SW3 and the fourth switching element SW4 are connected in series. The first upper and lower arm and the second upper and lower arm are connected in parallel. Diodes are connected in anti-parallel to each of the switching elements SW1 to SW4. Each of the switching elements SW1 to SW4 is composed of a MOSFET or an IGBT. Each of the switching elements SW1 to SW4 performs a switching operation according to a control signal from a control device.

[0013] One end of one winding of the transformer 13 is connected to the connection point between the first switching element SW1 and the second switching element SW2. The other end of one winding of the transformer 13 is connected to the connection point between the third switching element SW3 and the fourth switching element SW4. A reactor L is provided between the connection point between the first switching element SW1 and the second switching element SW2 and one end of one winding of the transformer 13. The reactor L is provided on the AC side of the first bridge circuit 11. A first smoothing capacitor C1 is provided on the DC side of the first bridge circuit 11.

[0014] The second bridge circuit 12 is a full-bridge circuit connected to the other winding of the transformer 13. The second bridge circuit 12 includes four switching elements SW5 to SW8. The second bridge circuit 12 has a third upper and lower arm in which the fifth switching element SW5 and the sixth switching element SW6 are connected in series, and a fourth upper and lower arm in which the seventh switching element SW7 and the eighth switching element SW8 are connected in series. The third upper and lower arm and the fourth upper and lower arm are connected in parallel. Diodes are connected in anti-parallel to each of the switching elements SW5 to SW8. Each of the switching elements SW5 to SW8 is constituted by a MOSFET or an IGBT. Each of the switching elements SW5 to SW8 performs a switching operation in response to a control signal from the control device.

[0015] One end of the other winding of the transformer 13 is connected to the connection point between the fifth switching element SW5 and the sixth switching element SW6. The other end of the other winding of the transformer 13 is connected to the connection point between the seventh switching element SW7 and the eighth switching element SW8. A second smoothing capacitor C2 is provided on the DC side of the second bridge circuit 12.

[0016] The transformer 13 includes a primary winding and a secondary winding. In the transformer 13, the turns ratio between one winding and the other winding is 1:1. The first bridge circuit 11 and the second bridge circuit 12 transmit power via the transformer 13.

[0017] The buck-boost circuit 1 transmits power between the charging stand 20 and the battery 30. The buck-boost circuit 1 converts the DC power supplied from the charging stand 20 into a desired voltage and outputs it to the battery 30.

[0018] The charging stand 20 is a rapid charging stand (DC stand) that supplies the power of the external power supply 21 to the battery 30. The external power supply 21 is a DC power supply. The output voltage of the charging stand 20 is about 400V.

[0019] The battery 30 is an in-vehicle battery mounted on an electric vehicle. The battery 30 is composed of, for example, a lithium-ion battery. The battery 30 is a battery pack in which a first battery 31 and a second battery 32 are connected in series. The voltage of the battery 30 is about 800V.

[0020] The buck-boost circuit 1 connects the DC-DC converter circuit 2 in the upper stage circuit and the pass-through circuit 3 in the lower stage circuit in input parallel and output series. The output terminals of the buck-boost circuit 1 are connected to both ends of the first battery 31 and the second battery 32, respectively. The charging stand 20 is directly connected to the second battery 32. The output voltage of the charging stand 20 becomes the voltage value of the second battery 32. The DC-DC converter circuit 2 has a voltage adjustment function between different input and output voltages. The DC-DC converter circuit 2 is capable of buck-boost operation. Also, the DC-DC converter circuit 2 can control the current in either the positive or negative current direction. The DC-DC converter circuit 2 is capable of bidirectional power conversion.

[0021] The buck-boost circuit 1 configured in this way can simultaneously control the step-up charging from the charging stand 20 with an output voltage of about 400V to the electric vehicle with a battery 30 voltage of about 800V and the power conversion of the temperature-rising operation using the internal resistance of the battery 30. By simultaneously performing the step-up charging and the power conversion of the temperature-rising operation by the buck-boost circuit 1, it becomes possible to shorten the charging time in cold regions. The output terminals of the buck-boost circuit 1 are connected to both ends of the battery 30 and the three terminals of the internal battery. The buck-boost circuit 1 is driven by the current control of the DC-DC converter circuit 2, and by adding an arbitrary frequency component to the current command value, a temperature-rising operation is realized by the internal resistance loss due to the power conversion between battery cells.

[0022] Referring to FIGS. 2 to 6, the simultaneous operation mode of boost charging and temperature increase will be described. The simultaneous operation mode includes a first mode M1, a second mode M2, a third mode M3, and a fourth mode M4. In the simultaneous operation mode, it transitions from the first mode M1 to the second mode M2, from the second mode M2 to the third mode M3, and from the third mode M3 to the fourth mode M4.

[0023] As shown in FIG. 2, the first mode M1 is an operation mode in which when storing the power supplied from the external power source 21 in the battery 30, the first battery 31 discharges and the second battery 32 is charged. When operating in the first mode M1, a current of 100 A flows from the external power source 21 to the input terminal of the buck-boost circuit 1, a current of 100 A flows from the positive electrode side of the first battery 31 to the buck-boost circuit 1, and a current of 200 A flows from the buck-boost circuit 1 to the positive electrode side of the second battery 32. As shown in FIG. 6, in the first mode M1, the current I1 of the first battery 31 becomes -100 A, and the current I2 of the second battery 32 becomes 200 A. The current of the battery 30 is represented such that charging is a positive value and discharging is a negative value.

[0024] As shown in FIG. 3, the second mode M2 is an operation mode in which when storing the power supplied from the external power source 21 in the battery 30, the first battery 31 does not charge or discharge, and the second battery 32 is charged. When operating in the second mode M2, a current of 100 A flows from the external power source 21 to the input terminal of the buck-boost circuit 1, no current flows between the first battery 31 and the buck-boost circuit 1, and a current of 100 A flows from the buck-boost circuit 1 to the positive electrode side of the second battery 32. As shown in FIG. 6, in the second mode M2, the current I1 of the first battery 31 becomes 0 A, and the current I2 of the second battery 32 becomes 100 A.

[0025] As shown in FIG. 4, the third mode M3 is an operation mode in which, when storing the power supplied from the external power source 21 in the battery 30, the first battery 31 is charged and the second battery 32 is not charged or discharged. When operating in the third mode M3, a current of 100 A flows from the external power source 21 to the input terminal of the buck-boost circuit 1, no current flows between the second battery 32 and the buck-boost circuit 1, and a current of 100 A flows from the buck-boost circuit 1 to the positive electrode side of the first battery 31. As shown in FIG. 6, in the third mode M3, the current I1 of the first battery 31 becomes 100 A, and the current I2 of the second battery 32 becomes 0 A.

[0026] As shown in FIG. 5, the fourth mode M4 is an operation mode in which, when storing the power supplied from the external power source 21 in the battery 30, the first battery 31 is charged and the second battery 32 discharges. When operating in the fourth mode M4, a current of 100 A flows from the external power source 21 to the input terminal of the buck-boost circuit 1, a current of 200 A flows from the buck-boost circuit 1 to the positive electrode side of the first battery 31, and a current of 100 A flows from the positive electrode side of the second battery 32 to the buck-boost circuit 1. As shown in FIG. 6, in the fourth mode M4, the current I1 of the first battery 31 becomes 200 A, and the current I2 of the second battery 32 becomes -100 A.

[0027] In the simultaneous operation mode, the DCDC converter circuit 2 operates with current control, and the current is set to the sum of the DC component (charging) and the AC component (temperature rise). The DC component of the current is the power distribution amount between the upper circuit and the lower circuit. The AC component of the current is the temperature rise amount of the battery 30. The current control of the DCDC converter circuit 2 can be controlled by the phase difference Φ of the full-bridge drive between the primary side and the secondary side. The DCDC converter circuit 2 performs power conversion in the forward direction with a positive phase difference Φ. The DCDC converter circuit 2 performs power conversion in the reverse direction with a negative phase difference Φ.

[0028] As described above, according to the embodiment, while charging the battery 30 with the power supplied from the external power supply 21, the temperature of the battery 30 can be increased, so the charging time is shortened. The buck-boost circuit 1 is driven by the current control of the DCDC converter circuit 2, and by adding an arbitrary frequency component to the current command value, the battery 30 can be heated by the internal resistance loss due to the power conversion between the battery cells. As a result, it is not necessary to provide another power conversion circuit for heating the battery 30, and an increase in size and cost can be suppressed.

[0029] Further, the buck-boost circuit 1 is not limited to the circuit shown in FIG. 1. For example, a relay may be provided between the input terminal of the buck-boost circuit 1 and the charging stand 20. A relay may be provided between the connection point of the first battery 31 and the second battery 32 and the output terminal of the buck-boost circuit 1. These relays are closed during external charging.

[0030] As a modification of the buck-boost circuit 1, the lower circuit may be replaced with an arbitrary bidirectional power conversion circuit. Even when the lower circuit is a two-way power conversion circuit, simultaneous control of boost charging and heating is possible. For example, the lower circuit can be configured by a non-inverting buck-boost chopper circuit or a CLLC circuit.

[0031] When the lower circuit is configured by a non-inverting buck-boost chopper circuit, since there is a voltage adjustment function between the charging stand 20 and the second battery 32, it can operate even if the voltage of the second battery 32 is outside the output range of the charging stand 20. By opening the output relay between the buck-boost circuit 1 and the battery 30, the heating operation becomes impossible, but high-efficiency boosting is possible in a wide output voltage range.

[0032] When the lower circuit is configured by a CLLC circuit, since there is a voltage adjustment function between the charging stand 20 and the second battery 32, it can operate even if the voltage of the second battery 32 is outside the output range of the charging stand 20. Since the primary side and the secondary side are insulated, a high-voltage cutoff circuit required in a non-insulated topology becomes unnecessary. Since the primary side and the secondary side are insulated, noise propagation to the charging stand 20 can be suppressed.

Description of Reference Numerals

[0033] 1 Buck - Boost Circuit 2 DC - DC Converter Circuit 3 Pass - Through Circuit 11 First Bridge Circuit 12 Second Bridge Circuit 13 Transformer 20 Charging Stand 21 External Power Supply 30 Battery 31 First Battery 32 Second Battery

Claims

【Claim 1】 A DC-DC converter circuit in which a first bridge circuit and a second bridge circuit are connected via a transformer, A pass-through circuit, Comprising, A buck-boost circuit that converts power to a predetermined voltage when charging from an external power source to an in-vehicle battery, When charging from the external power source to the in-vehicle battery, the DC-DC converter circuit and the pass-through circuit are connected in input parallel and output series, Simultaneously control step-up charging to boost the output voltage of the external power source to the voltage of the in-vehicle battery and power conversion of a temperature-rising operation using the internal resistance of the in-vehicle battery, Set the current of the DC-DC converter circuit to the sum of the DC component and the AC component A buck-boost circuit characterized by the above.

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