Power supply system and control method thereof

Abstract

To provide a power supply system that does not require a high-precision voltage sensor to avoid inrush current and measure the timing for turning on a contactor.SOLUTION: A power supply system 1 includes: a positive electrode side contactor 7 interposed in a positive electrode power line 6; a negative electrode side contactor 9 interposed in a negative electrode power line 8; a pre-charge circuit (12); a potential difference detection circuit 13 for detecting a potential difference between both ends of the positive electrode side contactor 7; and a contactor control circuit 14 for receiving an output of the potential difference detection circuit 13 and controlling the positive electrode side contactor 7 and the negative electrode side contactor 9. The contactor control circuit 14 temporarily turns on the positive electrode side contactor 7 in a state where the negative electrode side contactor 9 is turned off at start-up of the power supply system 1, holds the output of the potential difference detection circuit 13 at the time of the turning-on as a correction value, turns off the positive electrode side contactor 7 after the holding, turns on the negative electrode side contactor 9, and turns on the positive electrode side contactor 7 when the output of the potential difference detection circuit 13 reaches the correction value.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a power supply system and a control method thereof. [Background technology]

[0002] In recent years, efforts to realize a low-carbon or carbon-free society have been gaining momentum, and research and development into electric vehicles is being conducted to reduce CO2 emissions and improve energy efficiency in vehicles. In electric vehicles, the electric load, including the drive motor, and the battery as a power source are connected via a main contactor.

[0003] A smoothing capacitor that stabilizes the power supply voltage is provided in a circuit that supplies power from a power supply to drive a load. The smoothing capacitor needs to be precharged when power is supplied to the load. In this case, it is necessary to reduce the inrush current when the smoothing capacitor in a discharged state is precharged to avoid welding of the main contactor. A common method for achieving this is to connect a precharge circuit, which is a series connection of a precharge resistor and a relay, in parallel with the main contactor, and to charge the smoothing capacitor in advance with a certain charging time constant in the precharge circuit system. The inrush current is suppressed by turning on the main contactor after this charging time constant has elapsed (see, for example, Patent Document 1).

[0004] Meanwhile, in recent years, a method has been adopted in which the voltage on the secondary side of the main contactor as seen from the power supply side is raised to the voltage on the primary side in advance using a bidirectional DC-DC converter. The secondary side voltage and the primary side voltage are monitored, and when the two voltages become approximately equal, the main contactor is turned on to suppress the inrush current (for example, see Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6048363 [Patent Document 2] Patent No. 6394368 Summary of the Invention [Problem to be solved by the invention]

[0006] In order to suppress the inrush current when the contactor is closed, the voltage across the contactor is detected and the contactor is turned on when there is no longer a potential difference across the contactor. To effectively apply this method, it is possible to use highly accurate voltage sensors to detect the voltage across the contactor. However, using highly accurate voltage sensors significantly increases the hurdles in terms of production management and cost management for this type of power supply system, which in turn becomes an obstacle to the widespread use of electric vehicles.

[0007] The present invention aims to provide a power supply system and a control method thereof that does not require a high-precision voltage sensor in order to avoid inrush current and determine the timing to turn on the contactor. Achieving this aim will reduce the cost of this type of power supply system, eliminating one of the obstacles to the spread of electric vehicles, and ultimately contributing to improving overall energy efficiency. [Means for solving the problem]

[0008] (1) A power supply system (e.g., the power supply system 1 described later) that supplies power from a DC power supply (e.g., a battery 2 described later) to a load side provided with a smoothing capacitor (e.g., a smoothing capacitor 5 described later), the power supply system including: a precharge circuit (e.g., a bidirectional DC-DC converter 12 described later) that precharges the smoothing capacitor; a first polarity side contactor (e.g., a positive side contactor 7 described later) that is inserted in a power line of a first polarity (e.g., a positive power line 6 described later) that connects the DC power supply side and the load side; a second polarity side contactor (e.g., a negative side contactor 9 described later) that is inserted in a power line of a second polarity opposite to the first polarity (e.g., a negative power line 8 described later) that connects the DC power supply side and the load side; and a potential difference detection circuit (e.g., a potential difference detection circuit 13 described later) that detects a potential difference between both ends of the first polarity side contactor.

[0009] (2) The power supply system of (1), further comprising a contactor control circuit (e.g., contactor control circuit 14 described later) that receives an output of the potential difference detection circuit and controls the first polarity side contactor and the second polarity side contactor, wherein, when the power supply system is started, the contactor control circuit temporarily turns on the first polarity side contactor with the negative side contactor turned off and holds the output of the potential difference detection circuit when it is on as a correction value, turns off the first polarity side contactor after holding the output, turns on the second polarity side contactor, monitors the output of the potential difference detection circuit, and turns on the first polarity side contactor when the output of the potential difference detection circuit being monitored reaches the correction value.

[0010] (3) The power supply system of (1), wherein the precharge circuit is mainly composed of a bidirectional DC-DC converter (for example, a bidirectional DC-DC converter 12 described later).

[0011] (4) The power supply system of (1), wherein the precharge circuit is composed of a series connection of a resistor and a contactor, and the series connection is connected in parallel to the first polarity side contactor.

[0012] (5) A power supply circuit is configured to supply power from a DC power source (e.g., a battery 2 described later) to a load side provided with a smoothing capacitor (e.g., a smoothing capacitor 5 described later), and includes a first polarity side contactor (e.g., a positive side contactor 7 described later) inserted in a power line of a first polarity (e.g., a positive power line 6 described later) connecting the DC power source side and the load side, a second polarity side contactor (e.g., a negative side contactor 9 described later) inserted in a power line of a second polarity opposite to the first polarity (e.g., a negative power line 8 described later) connecting the DC power source side and the load side, a precharge circuit (e.g., a bidirectional DC-DC converter 12 described later) that precharges the smoothing capacitor, and a potential difference detection circuit (e.g., a power supply system control method including: a correction value holding step of temporarily turning on the first polarity side contactor with the second polarity side contactor turned off and holding an output of the potential difference detection circuit at the on time as a correction value, when the power supply system is started up; a potential difference monitoring step of turning off the first polarity side contactor after the correction value holding step, turning on the second polarity side contactor, and monitoring the output of the potential difference detection circuit; and a power supply starting step of turning on the positive side contactor when the output of the potential difference detection circuit being monitored in the potential difference monitoring step reaches the correction value.

[0013] (6) The method for controlling a power supply system according to (5), wherein the potential difference monitoring step precharges the smoothing capacitor by a bidirectional DC-DC converter that constitutes the precharge circuit.

[0014] (7) The power supply system of (1), further comprising a contactor control circuit (e.g., contactor control circuit 14 described later) that receives an output of the potential difference detection circuit and controls the first polarity side contactor and the second polarity side contactor, the contactor control circuit having a correction value readout unit that reads out, as a correction value, a value that is previously stored as a detection value of the potential difference detection circuit when the first polarity side contactor is temporarily turned on with the second polarity side contactor turned off, and at the beginning of startup of the power supply system, the second polarity side contactor is turned on with the first polarity side contactor turned off to monitor the output of the potential difference detection circuit, and when the output of the potential difference detection circuit being monitored reaches the correction value readout by the correction value readout unit, the first polarity side contactor is turned on.

[0015] (8) The power supply system according to (7), wherein the precharge circuit is mainly composed of a bidirectional DC-DC converter.

[0016] (9) The power supply system of (7), wherein the precharge circuit is composed of a series connection of a resistor and a contactor, and the series connection is connected in parallel to the first polarity side contactor.

[0017] (10) A power supply circuit is configured to supply power from a DC power source (e.g., a battery 2 described later) to a load side provided with a smoothing capacitor (e.g., a smoothing capacitor 5 described later), and includes a first polarity side contactor (e.g., a positive side contactor 7 described later) inserted in a first polarity power line (e.g., a positive power line 6 described later) connecting the DC power source side and the load side, a second polarity side contactor (e.g., a negative side contactor 9 described later) inserted in a second polarity power line (e.g., a negative power line 8 described later) connecting the DC power source side and the load side, the second polarity side contactor being opposite to the first polarity, a precharge circuit (e.g., a bidirectional DC-DC converter 12 described later) that precharges the smoothing capacitor, a potential difference detection circuit (e.g., a potential difference detection circuit 13 described later) that detects a potential difference between both ends of the first polarity side contactor, and a second polarity side contactor (e.g., a negative side contactor 9 described later). a correction value reading unit (e.g., a correction value reading unit 16 described later) that reads out, as a correction value, a detection value of the potential difference detection circuit when the first polarity side contactor is temporarily turned on with a second polarity side contactor turned off from a correction value holding circuit (e.g., a correction value holding circuit 15 described later) in which the detection value is stored in advance, the detection value being detected when the first polarity side contactor is turned off and the first polarity side contactor is temporarily turned on, the control method for a power supply system comprising: a potential difference monitoring step of turning on the second polarity side contactor with the first polarity side contactor turned off and monitoring an output of the potential difference detection circuit at the beginning of startup of the power supply system; and a power supply starting step of turning on the first polarity side contactor when the output of the potential difference detection circuit being monitored in the potential difference monitoring step reaches the correction value read out by the correction value reading unit.

[0018] (11) The method for controlling a power supply system according to (10), wherein the potential difference monitoring step precharges the smoothing capacitor by a bidirectional DC-DC converter that constitutes the precharge circuit. Effect of the Invention

[0019] In the power supply system of (1), the potential difference detection circuit detects the potential difference between both ends of the first polarity contactor (positive contactor in the example of Fig. 1). Therefore, it is possible to detect the timing when the voltage on the secondary side of the positive contactor becomes equal to the voltage on the primary side without measuring the voltage on the secondary side of the first polarity contactor with a high-precision voltage sensor with a wide measurement range. In other words, a high-precision voltage sensor with a wide measurement range is not required to detect the timing when precharging of the smoothing capacitor on the load side is completed, and the cost of this type of power supply system can be reduced, eliminating one of the obstacles to the spread of electric vehicles and ultimately contributing to improving overall energy efficiency.

[0020] In the power supply system (2), when the power supply system is started, the contactor control circuit temporarily turns on the first polarity side contactor while turning off the second polarity side contactor (negative side contactor in the example of FIG. 1), and holds the output of the potential difference detection circuit at the time of turning on as a correction value. This correction value is a reference value that is treated as a value equivalent to zero of the potential difference between the primary side and the secondary side of the first polarity side contactor, regardless of the detection accuracy of the potential difference detection circuit. By turning off the first polarity side contactor and turning on the second polarity side contactor after holding the correction value, the precharge by the precharge circuit is enabled, and the secondary side voltage, which is the voltage of the smoothing capacitor, gradually increases. In this state, the output of the potential difference detection circuit is monitored, and when the output of the potential difference detection circuit being monitored reaches the correction value, that is, when the potential difference between the primary side and the secondary side of the first polarity side contactor becomes zero, the first polarity side contactor is turned on. This makes it possible to turn on the first polarity side contactor at an appropriate timing to avoid an inrush current, without detecting the voltages on the primary and secondary sides of the first polarity side contactor with high accuracy.

[0021] In the power supply system (3), the precharge circuit is mainly composed of a bidirectional DC-DC converter. This eliminates the need for a circuit consisting of a series connection of a precharge resistor and a contactor and connected in parallel to the positive contactor, thereby reducing the cost of the power supply system.

[0022] In the power supply system of (4), the precharge circuit is composed of a series connection of a resistor and a contactor, and this series connection is connected in parallel to the first polarity side contactor. Therefore, the smoothing capacitor is charged with a charging time constant determined by its capacitance value and the resistance value of the precharge circuit. Therefore, after the charging time constant has elapsed, the voltage on the secondary side of the first polarity side contactor naturally reaches a voltage close to the primary side voltage. Therefore, even without specifically detecting the voltage of the first polarity side contactor, it is possible to avoid an inrush current and measure the timing to turn on the positive polarity side contactor, but a means for timing the charging time constant is required. In the power supply system of the present disclosure, the timing to turn on the first polarity side contactor is appropriately measured by the output of the contactor control circuit without having a means for timing the charging time constant.

[0023] In the power supply system control method of (5), in a correction value holding step, when starting up the power supply system, the first polarity side contactor is temporarily turned on with the second polarity side contactor turned off, and the output of the potential difference detection circuit when the first polarity side contactor is on is held as a correction value. This correction value is a reference value that is treated as a zero equivalent value of the potential difference between the primary side and the secondary side of the first polarity side contactor, regardless of the detection accuracy of the potential difference detection circuit. In a subsequent potential difference monitoring step, the first polarity side contactor is turned off, the second polarity side contactor is turned on, and the output of the potential difference detection circuit is monitored. In a power supply starting step, when the output of the potential difference detection circuit being monitored reaches the correction value, the first polarity side contactor is turned on. This makes it possible to turn on the first polarity side contactor at an appropriate timing to avoid inrush current, without detecting the voltages of the primary side and secondary side of the first polarity side contactor with high accuracy.

[0024] In the power supply system control method of (6), in the potential difference monitoring step, the smoothing capacitor is precharged by the bidirectional DC-DC converter constituting the precharge circuit. This eliminates the need for a circuit composed of a series connection of a precharge resistor and a contactor and connected in parallel to the first polarity side contactor, thereby reducing the cost of the power supply system.

[0025] In the power supply system of (7), a contactor control circuit has a correction value readout unit that reads out as a correction value a value previously stored as a detection value of the potential difference detection circuit when the first polarity side contactor is temporarily turned on with the second polarity side contactor turned off, and at the beginning of startup of the power supply system, the second polarity side contactor is turned on with the first polarity side contactor turned off to monitor the output of the potential difference detection circuit, and when the output of the potential difference detection circuit being monitored reaches the correction value readout by the correction value readout unit, the first polarity side contactor is turned on. This makes it possible to turn on the first polarity side contactor at an appropriate timing to avoid inrush current, without detecting the voltages on the primary and secondary sides of the first polarity side contactor with high accuracy.

[0026] In the power supply system (8), the precharge circuit is mainly composed of a bidirectional DC-DC converter. This eliminates the need for a circuit consisting of a series connection of a precharge resistor and a contactor and connected in parallel to the positive contactor, thereby reducing the cost of the power supply system.

[0027] In the power supply system of (9), the precharge circuit is composed of a series connection of a resistor and a contactor, and this series connection is connected in parallel to the first polarity side contactor. Therefore, the smoothing capacitor is charged with a charging time constant determined by its capacitance value and the resistance value of the precharge circuit. Therefore, after the charging time constant has elapsed, the voltage on the secondary side of the first polarity side contactor naturally reaches a voltage close to the voltage on the primary side. Therefore, even without specifically detecting the voltage of the first polarity side contactor, it is possible to avoid an inrush current and measure the timing to turn on the positive polarity side contactor, but a means for timing the charging time constant is required. In the power supply system of the present disclosure, the timing to turn on the first polarity side contactor is appropriately measured by the output of the contactor control circuit without having a means for timing the charging time constant.

[0028] In the power supply system control method of (10), in a potential difference monitoring step, at the beginning of startup of the power supply system, the second polarity side contactor is turned on while the first polarity side contactor is turned off and the output of the potential difference detection circuit is monitored. Also, in a power supply starting step, the first polarity side contactor is turned on when the output of the potential difference detection circuit being monitored in the potential difference monitoring step reaches the correction value read by the correction value reading unit. This makes it possible to turn on the first polarity side contactor at an appropriate timing to avoid inrush current, without detecting the voltages on the primary and secondary sides of the first polarity side contactor with high accuracy.

[0029] In the power supply system control method of (11), a circuit composed of a series connection of a precharge resistor and a contactor and connected in parallel to the first polarity side contactor is thus not required, thereby reducing the cost of the power supply system. [Brief description of the drawings]

[0030] [Figure 1] 1 is a circuit diagram illustrating an example of a power supply system according to the present disclosure. [Diagram 2] 2 is a timing diagram illustrating the operation of the power supply system of FIG. 1. [Diagram 3] FIG. 11 is a circuit diagram showing another example of a power supply system according to the present disclosure. [Figure 4] FIG. 11 is a timing diagram illustrating the operation of yet another example of the power supply system of the present disclosure. [Diagram 5] FIG. 13 is a conceptual diagram showing a contactor control circuit in yet another example of a power supply system according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] The power supply system of the present disclosure will now be described with reference to the drawings, in which: Figure 1 is a circuit diagram showing a power supply system 1 of the present disclosure.

[0032] The power supply system 1 is inserted into a circuit that supplies power from a battery 2, which is a DC power supply, to a PDU (Power Drive Unit) 4 in a DU (Driving Unit) 3 of a vehicle (not shown), which is a load. The DU 3 is composed of a traction motor (not shown) driven by the PDU 4, and a gear box, a differential gear, and the like mechanically connected to the traction motor. The PDU 4 converts the DC voltage supplied from the battery 2 into an AC voltage and applies it to the traction motor. The PDU 4 also converts the AC voltage input during regenerative operation of the traction motor, which is a motor generator, into a DC voltage. The PDU 4 is provided with a smoothing capacitor 5 that smoothes the DC voltage supplied from the battery 2.

[0033] A positive contactor 7 as a first polarity contactor is inserted into a positive power line 6 as a power line of a first polarity connecting the battery 2 and the PDU 4. A negative contactor 9 as a second polarity contactor is inserted into a negative power line 8 as a power line of a second polarity opposite to the first polarity connecting the battery 2 and the PDU 4. Hereinafter, the battery 2 side of the positive contactor 7 will be referred to as the primary side, and the load side including the PDU 4 will be referred to as the secondary side, as appropriate. Similarly, the battery 2 side of the negative contactor 9 will be referred to as the primary side, and the load side including the PDU 4 will be referred to as the secondary side. The battery 2 is a high-voltage battery that is a series connection of many cells, and is managed by a high-voltage battery control unit 10. That is, the high-voltage battery control unit 10 monitors the voltage of each cell constituting the battery 2 to manage charging and discharging, and includes a cell voltage sensor 11 that monitors the voltage of each cell.

[0034] A bidirectional DCDC converter 12 is connected between the positive power line 6 and the negative power line 8. The bidirectional DCDC converter 12 precharges the smoothing capacitor 5 when the power supply system 1 is started. That is, the bidirectional DCDC converter 12 boosts the voltage of a power source such as a low-voltage battery (not shown) and supplies it to the smoothing capacitor 5, thereby boosting the voltage between its terminals (the potential of the positive power line 6). When the positive contactor 7 is in the on state and the PDU 4 is operating, the bidirectional DCDC converter 12 reduces the high voltage between the positive power line 6 and the negative power line 8 and supplies it to low-voltage auxiliary devices and the like.

[0035] In the power supply system 1 of the present disclosure, a potential difference detection circuit 13 and a contactor control circuit 14 are provided in the high-voltage battery control unit 10. The potential difference detection circuit 13 detects the potential difference between both ends of the positive contactor 7. The output of the potential difference detection circuit 13 is input to the contactor control circuit 14. In addition, the contactor control circuit 14 supplies control signals to the positive contactor 7 and the negative contactor 9 to control their on / off operations.

[0036] In detail, when the power supply system 1 is started, the contactor control circuit 14 temporarily turns on the positive contactor 7 while keeping the negative contactor 9 off, holds the output of the potential difference detection circuit 13 at this on time as a correction value, and turns off the positive contactor 7 after holding the correction value. After turning off the positive contactor 7, the contactor control circuit 14 turns on the negative contactor 9 and monitors the output of the potential difference detection circuit 13. During this monitoring period, the smoothing capacitor 5 is precharged by the bidirectional DC-DC converter 12, and the potential on the secondary side of the positive contactor 7 gradually approaches the potential on the primary side. When the output of the potential difference detection circuit 13 reaches the held correction value, the positive contactor 7 is turned on.

[0037] Next, the details of the operation of the power supply system 1 and the control method of the power supply system of the present disclosure will be described with reference to Fig. 2. Fig. 2 is a timing diagram showing the operation of the power supply system 1. In the following description, the positive contactor 7 and the negative contactor 9 operate under the control of a contactor control circuit 14. The contactor control circuit 14 also samples, holds, and monitors the output of the potential difference detection circuit 13. The bidirectional DC-DC converter 12 operates under the control of an ECU of a vehicle (not shown) having the power supply system 1 of the present disclosure.

[0038] Before the start command IG-SW is generated in response to the user's operation, both the positive contactor 7 and the negative contactor 9 are in the OFF state. Since the negative contactor 9 is OFF, the precharge function of the bidirectional DC-DC converter 12 is disabled, and the smoothing capacitor 5 is in a discharged state. Also, since the positive contactor 7 is OFF, the primary side of the positive contactor 7 is at approximately the same potential as the positive side of the battery 2 (V B volts), and the secondary side is approximately the same potential as the positive side of the smoothing capacitor 5 (V LK volts).

[0039] When a start command IG-SW is generated in response to a user's operation, a correction value acquisition preparation command is issued from the ECU in response to this. In response to the correction value acquisition preparation command, the positive contactor 7 is temporarily turned on, and the output of the potential difference detection circuit 13, which is the potential difference between the primary side and the secondary side of the positive contactor 7 when it is temporarily on, is sampled. The sampled output of the potential difference detection circuit 13 is held as a correction value in the contactor control circuit 14 (correction value holding step).

[0040] When the positive contactor 7 is on, the potential difference between the primary side and the secondary side is not strictly 0 volts due to a small voltage drop caused by the contact resistance of the main contact of the positive contactor 7 and the slight resistance of other conductors, but it is an appropriate value to regard as 0 volts for handling purposes. Such a value that is appropriate to regard as 0 volts is the correction value in this disclosure. That is, the potential difference between the primary side and the secondary side of the positive contactor 7 can be measured by a voltage sensor with a relatively narrow measurement range. With this measurement value, which is the correction value, the timing to turn on the positive contactor 7 can be appropriately determined with sufficient accuracy to avoid inrush current.

[0041] If it is attempted to measure the voltage on the secondary side of the positive contactor 7 individually, for example, it is necessary to measure the voltage with high accuracy in a wide measurement range of about 0 volts to 600 volts. For this reason, a high-accuracy voltage sensor with a sufficiently small measurement error in a relatively wide measurement range is required. Such a voltage sensor is composed only of parts extracted from lots with very high accuracy and small variation, and is very expensive. Therefore, it increases the cost of this type of power supply system, which in turn becomes an obstacle to the spread of electric vehicles. According to the power supply system 1 of the present disclosure, a high-accuracy voltage sensor with a wide measurement range is not required to measure the potential difference between the primary side and the secondary side of the positive contactor 7, so that such problems can be eliminated.

[0042] After the correction value is held in the correction value holding step described above, the positive contactor 7 is turned off, and then the negative contactor 9 is turned on to enable the precharge function of the bidirectional DC-DC converter 12. In this state, the output of the potential difference detection circuit 13 is monitored (potential difference monitoring step).

[0043] In the potential difference monitoring step, since the negative contactor 9 is on, the precharge function of the bidirectional DC-DC converter 12 is enabled, and the potential on the positive side of the smoothing capacitor 5 (V LK volts) gradually increases. As mentioned above, this V LKThe voltage V is the potential on the secondary side of the positive contactor 7. The bidirectional DC-DC converter 12 converts the voltage of a low-voltage source such as a low-voltage battery (not shown) into the normal voltage V of the positive power line 6. B The boost operation is performed with a target voltage of V volts, and the smoothing capacitor 5 is precharged. LK V B It is approximately expressed as a linear increase towards

[0044] In the potential difference monitoring step, the potential V of the positive electrode of the smoothing capacitor 5 LK Volts, i.e., the potential V of the secondary side of the positive contactor 7 LK The voltage gradually increases. Accordingly, the potential difference between the primary side and the secondary side of the positive contactor 7, which is the output of the potential difference detection circuit 13 being monitored, gradually decreases. When the potential differences between the primary side and the secondary side of the positive contactor 7 become substantially equal and the output of the potential difference detection circuit 13 reaches the above-mentioned correction value, the contactor control circuit 14 outputs V LK =V B The timing signal is sent to the positive contactor 7, and the positive contactor 7 turns on. The time when the output of the potential difference detection circuit 13 reaches the above-mentioned correction value means that the potential difference detection value, which is the output of the potential difference detection circuit 13, does not have to strictly match the correction value, but only needs to reach a value within an allowable range taking into account the current withstand strength of the positive contactor 7. The positive contactor 7 is provided with a self-holding circuit (not shown), which maintains the positive contactor 7 in the on state. As a result, both the positive contactor 7 and the negative contactor 9 turn on, and the power supply system 1 transitions to a regular operating state in which the power of the battery 2 is supplied to the PDU 4 (power supply start step).

[0045] In the above description, a circuit mainly composed of the bidirectional DC-DC converter 12 is used as the precharge circuit for the smoothing capacitor 5. However, the precharge circuit may be configured in such a way that a series connection of a precharge resistor and a precharge contactor is connected in parallel to the positive electrode side contactor 7, which is a known configuration.

[0046] As a modification of the power supply system 1 described above with reference to FIGS. 1 and 2, a power supply system in which the functions of the positive contactor 7 and the negative contactor 9 are interchanged can be realized.

[0047] FIG. 3 is a circuit diagram showing a power supply system in which the functions of the positive contactor 7 and the negative contactor 9 in FIG. 1 are interchanged. In FIG. 3, parts corresponding to those in FIG. 1 are given the same reference numerals. In the power supply system 1 in FIG. 3, the potential difference between both ends of the negative contactor 9 is detected by a potential difference detection circuit 13. Therefore, if the "negative contactor" is read as "positive" and the "positive contactor" is read as "negative contactor" in the timing diagram in FIG. 2, the timing diagram for the operation of the power supply system 1 in FIG. 3 is obtained. Therefore, the explanation in FIG. 2 is used to explain the details of the operation of the power supply system 1 in FIG. 3 and the control method of the power supply system related to the power supply system 1 in FIG. 3.

[0048] In the power supply system 1 and the control method for the power supply system of the present disclosure described with reference to Fig. 1, Fig. 2, and Fig. 3, the detection value of the potential difference detection circuit 13 is sampled once and stored as a correction value every time the power supply system is started up, in the procedure described with reference to Fig. 2. Thereafter, the first polarity side contactor (in one example, the positive electrode side contactor) is turned off, and when the detection value of the potential difference detection circuit 13 reaches the correction value, the first polarity side contactor is turned on to transition the power supply system to an operating state. However, the manner in which the correction value is acquired and stored is not limited to the manner described above with reference to Figs. 1, 2, and 3.

[0049] The power supply system of the present disclosure, which differs in the manner of acquiring and holding the correction value, is similar to the power supply system of Figs. 1 and 3 in terms of conceptual circuit diagram. Here, for convenience of explanation, a case will be explained in which the first polarity is positive and the second polarity is negative, but the positive / negative correspondence relationship between the first polarity and the second polarity may be reversed. The power supply system is configured to supply power from the battery 2 side as a DC power supply to a load side provided with a smoothing capacitor 5. A positive power line 6 as a power line of the first polarity and a negative power line 8 as a power line of the second polarity are provided to connect the battery 2 side and the load side.

[0050] A positive contactor 7 as a first polarity side contactor is inserted in a power line of a first polarity, and a negative contactor 9 as a second polarity side contactor is inserted in a power line of a second polarity. Also provided are a bidirectional DC-DC converter 12 as a precharge circuit that precharges the smoothing capacitor 5, and a potential difference detection circuit 13 that detects a potential difference between both ends of the positive contactor 7. Also provided is a contactor control circuit 14 that receives an output of the potential difference detection circuit and controls the first polarity side contactor and the second polarity side contactor.

[0051] In this case, the contactor control circuit 14 is different from the embodiment described above with reference to Figures 1, 2 and 3. That is, as in the contactor control circuit 14 of Figure 5, a correction value holding circuit 15 is provided inside or outside the contactor control circuit 14, which holds in advance the detection value of the potential difference detection circuit 13 when the positive contactor 7 is temporarily turned on with the negative contactor 9 turned off. The correction value holding circuit 15 can be composed of an EEPROM, a flash memory, or the like. Meanwhile, the contactor control circuit 14 has a correction value reading unit 16 that reads out the value held in the correction value holding circuit 15 as a correction value.

[0052] Fig. 4 is a timing diagram showing the operation of still another example of the power supply system of the present disclosure. As shown in the sequence diagram of Fig. 4, at the beginning of the start-up of the power supply system, the contactor control circuit 14 turns on the negative contactor 9 while turning off the positive contactor 7, monitors the output of the potential difference detection circuit 13, and turns on the positive contactor 7 when the output of the potential difference detection circuit 13 being monitored reaches the correction value read by the correction value reading unit.

[0053] Even in the example described with reference to Figures 4 and 5, the first polarity side contactor (positive side contactor 7 in one example) can be turned on at an appropriate timing to avoid inrush current, without detecting the primary and secondary voltages of the first polarity side contactor (positive side contactor 7 in one example) with high accuracy.

[0054] Incidentally, various aspects are possible for the timing at which the above-mentioned correction values ​​are stored in advance in a storage element such as an EEPROM or a flash memory used as the correction value storage circuit 15. Examples of such timing are as follows: (a) When the operation of the power supply system 1 is terminated, the sequence of sampling the output of the potential difference detection circuit 13 in FIG. 2 is repeated, and the correction value as the sampling result is stored in the storage element. (b) When power supply system 1 is manufactured to be mounted on a vehicle, in the final process of the vehicle production line, the sequence of sampling the output of potential difference detection circuit 13 in FIG. 2 is completed, and the correction value resulting from this sampling is stored in a memory element. (c) When the power supply system 1 is installed in a vehicle, a sequence of sampling the output of the potential difference detection circuit 13 in Figure 2 is completed at regular intervals based on time data from a device that can emit clock information, such as a GPS, and the correction value resulting from this sampling is stored in a memory element. (d) Focusing on the temperature dependency of the characteristic fluctuations of the power supply system 1, the potential difference detection circuit 13 or a portion nearby is used as the detection point, temperature information is acquired by a temperature detection element, and a sequence of sampling the output of the potential difference detection circuit 13 in Figure 2 is completed in accordance with the fluctuation range of the acquired temperature, and a correction value as a result of this sampling is stored in a memory element.

[0055] The power supply system 1 and the control method thereof disclosed herein provide the following advantages.

[0056] In the power supply system 1 of (1), the potential difference between both ends of the positive contactor 7 is detected by the potential difference detection circuit 13. Therefore, it is possible to detect the timing when the voltage on the secondary side of the positive contactor 7 becomes equal to the voltage on the primary side, without measuring the voltage on the secondary side of the positive contactor 7 with a highly accurate voltage sensor with a wide measurement range. In other words, a highly accurate voltage sensor with a wide measurement range is not required to detect the timing when precharging of the smoothing capacitor 5 on the load side is completed, and the cost of this type of power supply system can be reduced, eliminating one of the obstacles to the spread of electric vehicles and ultimately contributing to improving overall energy efficiency.

[0057] In the power supply system 1 of (2), when the power supply system 1 is started, the contactor control circuit 14 temporarily turns on the positive contactor 7 with the negative contactor 9 turned off, and holds the output of the potential difference detection circuit 13 at the time of turning on as a correction value. This correction value is a reference value that is treated as a zero-equivalent value of the potential difference between the primary side and the secondary side of the positive contactor 7, regardless of the detection accuracy of the potential difference detection circuit 13. After holding the correction value, under the control of the contactor control circuit 14, the positive contactor 7 is turned off and the negative contactor 9 is turned on. By turning on the negative contactor 9, the precharge function of the bidirectional DC-DC converter 12, which is a precharge circuit, is enabled. That is, the smoothing capacitor 5 is precharged by the high voltage generated by the boost operation of the bidirectional DC-DC converter 12. As a result, the potential V of the secondary side of the positive contactor 7, which is the voltage of the smoothing capacitor 5, is LKgradually increases. In this state, the contactor control circuit 14 monitors the output of the potential difference detection circuit 13, and when the output of the potential difference detection circuit 13 being monitored reaches a correction value, that is, when the potential difference between the primary side and the secondary side of the positive contactor 7 becomes a value equivalent to zero, the contactor control circuit 14 turns on the positive contactor 7. Therefore, the positive contactor 7 can be turned on at an appropriate timing to avoid an inrush current without detecting the voltages of the primary side and the secondary side of the positive contactor 7 with high accuracy. According to the power supply system 1 of the present disclosure, since a high-accuracy voltage sensor is not required to measure the potential difference between the primary side and the secondary side of the positive contactor 7, it is possible to avoid an increase in costs related to voltage measurement, which occurs when the voltages of the primary side and the secondary side of the positive contactor 7 are individually measured by a high-accuracy voltage sensor in a relatively wide measurement range, while maintaining the quality of the product. This leads to the promotion of the spread of electric vehicles.

[0058] In the power supply system 1 of (3), the precharge circuit is mainly composed of the bidirectional DC-DC converter 12. This eliminates the need for a circuit composed of a series connection of a precharge resistor and a contactor and connected in parallel to the positive contactor 7, thereby reducing the cost of the power supply system 1.

[0059] In the power supply system (4), the precharge circuit is composed of a series connection of a resistor and a contactor, and this series connection is connected in parallel to the positive contactor. Therefore, the smoothing capacitor 5 is charged with a charging time constant determined by its capacitance value and the resistance value of the precharge circuit. Therefore, after the charging time constant has elapsed, the voltage on the secondary side of the positive contactor 7 naturally reaches the vicinity of the voltage on the primary side. Therefore, even without specifically detecting the voltage of the positive contactor 7, it is possible to avoid an inrush current and determine the timing to turn on the positive contactor 7. However, in this embodiment, a means for performing a timing operation of about the charging time constant is required. In the power supply system of the present disclosure, the timing to turn on the positive contactor 7 is appropriately determined by the output of the contactor control circuit 14 that operates by monitoring the output of the potential difference detection circuit 13 without having a means for performing a timing operation.

[0060] In the power supply system control method of (5), in a correction value holding step, when starting up the power supply system 1, the positive contactor 7 is temporarily turned on with the negative contactor 9 turned off, and the output of the potential difference detection circuit 13 at this on time is held as a correction value. This correction value is a reference value that is treated as a zero equivalent value of the potential difference between the primary side and the secondary side of the positive contactor 7, regardless of the detection accuracy of the potential difference detection circuit 13. In a subsequent potential difference monitoring step, the positive contactor 7 is turned off, the negative contactor 9 is turned on, and the output of the potential difference detection circuit 13 is monitored. In a power supply start step, when the output of the potential difference detection circuit 13 being monitored reaches the correction value, the positive contactor 7 is turned on. This makes it possible to turn on the positive contactor 7 at an appropriate timing to avoid inrush current, without detecting the voltages of the primary side and secondary side of the positive contactor 7 with high accuracy. According to the power supply system control method of the present disclosure, since a high-precision voltage sensor is not required to measure the potential difference between the primary and secondary sides of the positive contactor 7, it is possible to avoid the increased costs associated with voltage measurement that would arise when the voltages of the primary and secondary sides of the positive contactor 7 are measured individually with high-precision voltage sensors, while maintaining the quality of the product, which in turn promotes the spread of electric vehicles.

[0061] In the power supply system control method (6), in the potential difference monitoring step, the bidirectional DC-DC converter 12 constituting the precharge circuit precharges the smoothing capacitor 5. This eliminates the need for a circuit composed of a series connection of a precharge resistor and a contactor and connected in parallel to the positive contactor, thereby reducing the cost of the power supply system.

[0062] In the power supply system 1 of (7), the contactor control circuit 14 has a correction value reading unit 16 that reads out, as a correction value, a value previously stored in the correction value holding circuit 15 as a detection value of the potential difference detection circuit 13 when the first polarity side contactor (positive polarity side contactor 7) is temporarily turned on with the second polarity side contactor (negative polarity side contactor 9) turned off, and at the beginning of startup of the power supply system, the second polarity side contactor is turned on with the first polarity side contactor turned off to monitor the output of the potential difference detection circuit 13, and when the output of the potential difference detection circuit 13 being monitored reaches the correction value read out by the correction value reading unit 16, the first polarity side contactor is turned on. This makes it possible to turn on the first polarity side contactor at an appropriate timing to avoid inrush current, without detecting the voltages on the primary and secondary sides of the first polarity side contactor with high accuracy.

[0063] In the power supply system (8), the precharge circuit is mainly composed of the bidirectional DC-DC converter 12. This eliminates the need for a circuit composed of a series connection of a precharge resistor and a contactor and connected in parallel to the positive contactor, thereby reducing the cost of the power supply system 1.

[0064] In the power supply system of (9), the precharge circuit is composed of a series connection of a resistor and a contactor, and this series connection is connected in parallel to the first polarity side contactor. Therefore, the smoothing capacitor 5 is charged with a charging time constant determined by its capacitance value and the resistance value of the precharge circuit. Therefore, after the charging time constant has elapsed, the voltage on the secondary side of the first polarity side contactor naturally reaches a voltage close to the primary side voltage. Therefore, even without specifically detecting the voltage of the first polarity side contactor, it is possible to avoid an inrush current and measure the timing to turn on the positive polarity side contactor, but a means for timing the charging time constant is required. In the power supply system of the present disclosure, the timing to turn on the first polarity side contactor 7 is appropriately measured by the output of the contactor control circuit 14 without having a means for timing the charging time constant.

[0065] In the power supply system control method of (10), in a potential difference monitoring step, at the beginning of startup of the power supply system, the second polarity side contactor 9 is turned on while the first polarity side contactor 7 is turned off, and the output of the potential difference detection circuit 13 is monitored. Also, in a power supply start step, the first polarity side contactor 7 is turned on when the output of the potential difference detection circuit 13 being monitored in the potential difference monitoring step reaches the correction value read by the correction value reading unit 16. This makes it possible to turn on the positive polarity side contactor at an appropriate timing to avoid an inrush current, without detecting the voltages on the primary and secondary sides of the first polarity side contactor 7 with high accuracy.

[0066] In the power supply system control method of (11), in the potential difference monitoring step, the bidirectional DC-DC converter 12 constituting the precharge circuit precharges the smoothing capacitor 5. This eliminates the need for a circuit composed of a series connection of a precharge resistor and a contactor and connected in parallel to the positive contactor, thereby reducing the cost of the power supply system.

[0067] Although one embodiment of the power supply system and its control method of the present disclosure has been described above, the present invention is not limited to this. The detailed configuration may be changed as appropriate within the scope of the spirit of the present invention. For example, instead of providing the potential difference detection circuit 13 and the contactor control circuit 14 in the high voltage battery control unit 10, a separate unit such as another ECU may be configured to have functional parts equivalent to the potential difference detection circuit 13 and the contactor control circuit 14. [Explanation of symbols]

[0068] 1. Power supply system 2. Battery 3…DU 4…PDU 5…Smoothing capacitor 6…Positive power line 7…Positive contactor 8…Negative power line 9…Negative contactor 10...High voltage battery control unit 11...Cell voltage sensor 12...Bidirectional DC / DC converter 12 13... Potential difference detection circuit 14...Contactor control circuit 15...Correction value holding circuit 16...Correction value readout section

Claims

1. A power supply system that supplies power from a DC power supply side to a load side provided with a smoothing capacitor, a precharge circuit for precharging the smoothing capacitor; a first polarity side contactor inserted in a power line of a first polarity connecting the DC power supply side and the load side; a second polarity side contactor inserted in a power line of a second polarity opposite to the first polarity connecting the DC power source side and the load side; a potential difference detection circuit that detects a potential difference between both ends of the first polarity side contactor; a contactor control circuit that receives an output of the potential difference detection circuit and controls the first polarity side contactor and the second polarity side contactor, the contactor control circuit, upon startup of the power supply system, temporarily turns on the first polarity side contactor with the second polarity side contactor turned off, and holds the output of the potential difference detection circuit when it is on as a correction value, turns off the first polarity side contactor after holding the output, turns on the second polarity side contactor, monitors the output of the potential difference detection circuit, and turns on the first polarity side contactor when the output of the potential difference detection circuit being monitored reaches the correction value.

2. A power supply system that supplies power from a DC power supply side to a load side provided with a smoothing capacitor, a precharge circuit for precharging the smoothing capacitor; a first polarity side contactor inserted in a power line of a first polarity connecting the DC power supply side and the load side; a second polarity side contactor inserted in a power line of a second polarity opposite to the first polarity connecting the DC power source side and the load side; a potential difference detection circuit that detects a potential difference between both ends of the first polarity side contactor; a contactor control circuit that receives an output of the potential difference detection circuit and controls the first polarity side contactor and the second polarity side contactor, The contactor control circuit has a correction value reading unit that reads out, as a correction value, a value that is pre-stored as a detection value of the potential difference detection circuit when the first polarity side contactor is temporarily turned on with the second polarity side contactor turned off, and at the beginning of startup of the power supply system, turns on the second polarity side contactor with the first polarity side contactor turned off to monitor an output of the potential difference detection circuit, and when the output of the potential difference detection circuit being monitored reaches the correction value read out by the correction value reading unit, turns on the first polarity side contactor.

3. 3. The power supply system according to claim 1, wherein the precharge circuit is mainly composed of a bidirectional DC-DC converter.

4. 3. The power supply system according to claim 1, wherein the precharge circuit is formed of a series connection of a resistor and a contactor, and the series connection is connected in parallel to the first polarity side contactor.

5. A control method for a power supply system configured to supply power from a DC power supply side to a load side provided with a smoothing capacitor, the power supply system including a first polarity side contactor inserted in a power line of a first polarity connecting the DC power supply side and the load side, a second polarity side contactor inserted in a power line of a second polarity opposite to the first polarity connecting the DC power supply side and the load side, a precharge circuit that precharges the smoothing capacitor, and a potential difference detection circuit that detects a potential difference between both ends of the first polarity side contactor, a correction value holding step of temporarily turning on the first polarity side contactor while keeping the second polarity side contactor off, and holding an output of the potential difference detection circuit at the time of turning on the first polarity side contactor as a correction value, when starting up the power supply system; a potential difference monitoring step of turning off the first polarity side contactor and turning on the second polarity side contactor after the correction value holding step, and monitoring an output of the potential difference detection circuit; a power supply starting step of turning on the first polarity side contactor when the output of the potential difference detection circuit being monitored in the potential difference monitoring step reaches the correction value; A method for controlling a power supply system comprising:

6. A control method for a power supply system configured to supply power from a DC power supply side to a load side provided with a smoothing capacitor, the control method comprising: a first polarity side contactor inserted in a power line of a first polarity connecting the DC power supply side and the load side; a second polarity side contactor inserted in a power line of a second polarity opposite to the first polarity connecting the DC power supply side and the load side; a precharge circuit for precharging the smoothing capacitor; a potential difference detection circuit for detecting a potential difference between both ends of the first polarity side contactor; and a correction value reading unit for reading out, as a correction value, a detection value of the potential difference detection circuit when the first polarity side contactor is temporarily turned on with the second polarity side contactor turned off from a correction value holding circuit in which the detection value is prestored, a potential difference monitoring step of, at the beginning of startup of the power supply system, turning on the second polarity side contactor while keeping the first polarity side contactor off, and monitoring an output of the potential difference detection circuit; a power supply starting step of turning on the first polarity side contactor when an output of the potential difference detection circuit being monitored in the potential difference monitoring step reaches the correction value read by the correction value reading unit; A method for controlling a power supply system comprising:

7. A control method for a power supply system as described in claim 5 or 6, wherein, in the potential difference monitoring step, the smoothing capacitor is precharged by a bidirectional DC-DC converter that constitutes the precharge circuit.

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