Relay control circuit, energy storage device

Abstract

To reduce the number of used relay control switches to simplify a drive circuit while maintaining a malfunction suppression function of a relay.SOLUTION: A relay control circuit 110 includes a bypass circuit 120 connected in parallel with a relay 55, and a drive circuit 130 that drives the relay 55. The bypass circuit 120 includes: a first switch 121 and a second switch 123 connected in series to each other; and a diode 125 arranged between the first switch 121 and the second switch 123 so that its anode is connected with the first switch 121 and its cathode is connected with the second switch 123, using a discharge direction of a cell 60 as a forward direction. The drive circuit 130 includes: relay coils 133A and 133B connected with the cathode of the diode 125; and control switches 135A and 135B connected in series with the relay coils 133A and 133B, respectively, and connecting the relay coils 133A and 133B with a reference potential.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a relay control circuit.

Background Art

[0002] One of the battery protection devices is a circuit breaker such as a relay. When detecting abnormalities such as over-discharge or over-charge of the battery, the relay can be opened to cut off the current, thereby protecting the battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] FIG. 17 shows a drive circuit 510 of a relay 500. The drive circuit 510 includes a relay coil 520 and a switch circuit 530. The switch circuit 530 is composed of two control switches 531 and 533 connected in series.

[0005] By using two control switches 531 and 533 connected in series for the switch circuit 530, even if one of the control switches 531 and 533 closes due to malfunction, no current flows through the relay coil 520. Therefore, it is possible to avoid the unintentional operation of the relay 500 (malfunction suppression function). However, since two control switches 531 and 533 are required for one relay coil 520, the number of control switches 531 and 533 used increases. One problem of the present invention is to reduce the number of relay control switches used and simplify the drive circuit while maintaining the malfunction suppression function of the relay.

Means for Solving the Problems

[0006] The control circuit for the relay that interrupts the current to the cell includes a bypass circuit connected in parallel with the relay and a drive circuit that drives the relay.

[0007] The bypass circuit includes a first switch and a second switch connected in series, and a diode positioned between the first switch and the second switch such that its anode is connected to the first switch and its cathode to the second switch, and which directs the discharge direction of the cell forward.

[0008] The drive circuit includes a relay coil connected to the cathode of the diode and a control switch connected in series with the relay coil, which connects the relay coil to a reference potential.

[0009] This technology can be applied to energy storage devices. [Effects of the Invention]

[0010] This technology allows for a reduction in the number of switches used and simplification of the drive circuit while maintaining the relay's malfunction suppression function. [Brief explanation of the drawing]

[0011] [Figure 1] Side view of a car [Figure 2] Battery disassembled perspective view [Figure 3] Plan view of the cell [Figure 4] Cross-sectional view along line AA in Figure 3 [Figure 5] Block diagram showing the electrical configuration of the battery [Figure 6] Diagram showing a battery pack and voltage detection unit. [Figure 7] Diagram showing the current path when the relay is open. [Figure 8] Diagram showing the current path of the excitation current. [Figure 9] Diagram showing the current path of the excitation current. [Figure 10] Diagram showing the current path of the excitation current. [Figure 11]Chart summarizing the states of each switch in normal and abnormal conditions [Figure 12] Diagram showing the current path before relay opening [Figure 13] Diagram showing the current path after relay opening [Figure 14] Flowchart of the relay failure detection process [Figure 15] Diagram showing other failure detection methods (comparative example) [Figure 16] Block diagram showing the electrical configuration of the battery [Figure 17] Relay drive circuit (comparative example)

Mode for Carrying Out the Invention

[0012] The outline of the relay control circuit will be described. The relay control circuit includes a bypass circuit connected in parallel to the relay, and a drive circuit for driving the relay.

[0013] The bypass circuit includes a first switch and a second switch connected in series, and a diode disposed between the first switch and the second switch such that the anode is connected to the first switch and the cathode is connected to the second switch, and the discharge direction of the cell is in the forward direction.

[0014] The drive circuit includes a relay coil connected to the cathode of the diode, and a control switch connected in series with the relay coil and connecting the relay coil to the reference potential.

[0015] In this configuration, when two switches (the first switch or the second switch and the control switch) close, an exciting current flows through the relay coil, and even if one of the two switches closes due to malfunction, no exciting current flows through the relay coil. Therefore, malfunction of the relay can be suppressed and the reliability of the relay is high.

[0016] This configuration uses the first and second switches of the bypass circuit as switches for relay control, thereby reducing the number of switches used for relay control.

[0017] The drive circuit may include a first drive circuit for closing and a second drive circuit for opening. The relay may be switched to the closed position by closing the two switches, the first switch and the control switch of the first drive circuit, and allowing current to flow through the relay coil of the first drive circuit. The relay may be switched to the open position by closing the two switches, the second switch and the control switch of the second drive circuit, and allowing current to flow through the relay coil of the second drive circuit.

[0018] This configuration allows the relay to be switched between closed and open states.

[0019] The drive circuit may include a first drive circuit for closing and a second drive circuit for opening. The first and second switches may be FETs connected back-to-back via the diode. When an overvoltage is detected in the cell, the relay may be opened by closing the two switches, the first switch and the control switch of the second drive circuit, and allowing current to flow through the relay coil of the second drive circuit.

[0020] In this configuration, even after the relay opens, discharge current can flow from the cell to the load via the parasitic diode of the second switch until the first switch opens.

[0021] The relay control circuit described above can be applied to energy storage devices. The energy storage device may also include a configuration comprising positive and negative external terminals, cells connected to the positive and negative external terminals, a relay for interrupting the current of the cells, a current sensor for measuring the current of the cells, a management device, and a relay control circuit.

[0022] A power storage unit may be connected between the positive and negative external terminals of the power storage device. The drive circuit may include a first drive circuit for closing and a second drive circuit for opening.

[0023] The control device may close the control switches of the first switch, the second switch, and the second drive circuit, open the relay by supplying current to the relay coil of the second drive circuit, and detect an open fault of the relay based on the change in the measured value of the current sensor before and after the relay opens.

[0024] When the relay opens normally, the current path flowing through the second drive circuit switches from the path powered by the battery pack (current path L1 shown in Figure 12) to the path powered by the energy storage unit (current path L2 shown in Figure 13), causing a change in the current sensor's measurement. Specifically, before the relay opens, the current sensor is current-free, and after the relay opens, current flows through the current sensor. Therefore, an open fault in the relay can be detected based on the change in the current sensor's measurement before and after the relay opens.

[0025] The management device may calculate and record the resistance value of the second drive circuit based on the current sensor measurement value after the relay opens and the voltage of the energy storage unit, and determine the deterioration state of the second drive circuit from the change in the resistance value of the second drive circuit over time. In this configuration, the timing for replacing the second drive circuit can be determined from the deterioration state of the second drive circuit.

[0026] The control device may perform fault detection of the relay when the cell is not being charged. During charging, current flows to the current sensor not only when the relay is open, but also when it is closed. Therefore, it is difficult to determine with accuracy whether the relay is open or closed, as the measured value of the current sensor does not change easily before and after the relay opens.

[0027] Relay fault detection is preferably performed when the energy storage unit is charged and the energy storage device is discharging no current or a current below a predetermined value. An example of a situation that satisfies these conditions is when the vehicle is parked.

[0028] <Embodiment 1> 1. Battery 50 Description As shown in Figure 1, the automobile 10 is equipped with an engine 20 and a battery 50 used for starting the engine 20, etc. The battery 50 is an example of an "energy storage device". The automobile 10 may also be equipped with an energy storage device for vehicle propulsion or a fuel cell.

[0029] As shown in Figure 2, the battery 50 comprises a battery pack 60, a circuit board unit 65, and a housing 71. The housing 71 comprises a main body 73 and a lid 74 made of synthetic resin material. The main body 73 is a bottomed cylindrical shape and comprises a bottom portion 75 and four side portions 76. The four side portions 76 form an opening 77 at the upper end of the main body 73.

[0030] The housing 71 houses the battery pack 60 and the circuit board unit 65. The circuit board unit 65 is a board unit on which various components (relays 55, the relay control circuit 110 and management device 150 shown in Figure 5, etc.) are mounted on the circuit board 100, and is positioned adjacent to the battery pack 60, for example, above it, as shown in Figure 2. Alternatively, the circuit board unit 65 may be positioned adjacent to the side of the battery pack 60.

[0031] The cover 74 closes the opening 77 of the main body 73. An outer peripheral wall 78 is provided around the cover 74. The cover 74 has a projection 79 that is roughly T-shaped in plan view. A positive external terminal 51 is fixed to one corner of the front of the cover 74, and a negative external terminal 52 is fixed to the other corner. The circuit board unit 65 may be housed inside the cover 74 (for example, inside the projection 79) instead of the main body 73 of the housing 71.

[0032] The battery pack 60 is composed of multiple cells 62. As shown in Figure 4, each cell 62 houses an electrode body 83 together with a non-aqueous electrolyte within a rectangular parallelepiped (prismatic) case 82. The cell 62 is, for example, a lithium-ion secondary battery cell. The case 82 has a case body 84 and a lid 85 that closes the opening at its top.

[0033] The electrode body 83, although not shown in detail, consists of a negative electrode plate made of a copper foil substrate coated with an active material and a positive electrode plate made of an aluminum foil substrate coated with an active material, with a separator made of a porous resin film placed between them. Both are in the shape of a strip, and are wound flat so that they can be housed in the case body 84, with the negative electrode plate and positive electrode plate offset to opposite sides in the width direction relative to the separator. The electrode body 83 may be of a laminated type instead of the wound type.

[0034] A positive electrode terminal 87 is connected to the positive electrode plate via a positive electrode current collector 86, and a negative electrode terminal 89 is connected to the negative electrode plate via a negative electrode current collector 88. The positive electrode current collector 86 and the negative electrode current collector 88 each have a flat base portion 90 and legs 91 extending from the base portion 90. Through holes are formed in the base portion 90. The legs 91 are connected to the positive electrode plate or the negative electrode plate.

[0035] The positive terminal 87 and the negative terminal 89 each consist of a terminal body 92 and a shaft 93 that protrudes downward from the center of its lower surface. The terminal body 92 and shaft 93 of the positive terminal 87 are integrally molded from aluminum (a single material). In the negative terminal 89, the terminal body 92 is made of aluminum and the shaft 93 is made of copper, and these are assembled together. The terminal body 92 of the positive terminal 87 and the negative terminal 89 are positioned at both ends of the cover 85 via gaskets 94 made of insulating material, and are exposed to the outside from these gaskets 94, as shown in Figure 3.

[0036] The cover 85 has a pressure relief valve 95. The pressure relief valve 95 is located between the positive terminal 87 and the negative terminal 89. The pressure relief valve 95 is a safety valve. The pressure relief valve 95 opens when the internal pressure of the case 82 exceeds a limit, thereby reducing the internal pressure of the case 82.

[0037] Figure 5 is a block diagram showing the electrical configuration of the battery 50. The battery 50 comprises a battery pack 60, a current sensor 53, a voltage detection unit 54 (see Figure 6), a relay 55, a temperature sensor 58, a relay control circuit 110, and a management device 150.

[0038] The battery 50 is electrically connected to an on-board electrical load 170, a capacitor 180, and an alternator (not shown). The capacitor 180 is connected to the positive and negative external terminals 51 and 52 of the battery 50 and is provided to stabilize the power supply voltage of the electrical load 170. The capacitor 180 is charged to a voltage approximately the same as the terminal voltage (V1-V2) of the battery 50 as the battery 50 is charged and discharged. The capacitor 180 is an example of the energy storage unit of the present invention.

[0039] While the engine 20 is running, if the amount of power generated by the alternator (not shown in the diagram) is greater than the power consumption of the electrical load 170, the battery 50 is charged by the alternator. If the amount of power generated by the alternator is less than the power consumption of the electrical load 170, the battery 50 is discharged to compensate for the deficit.

[0040] While the engine 20 is stopped, the alternator stops generating electricity. While power generation is stopped, the battery 50 is not charged and only discharges in response to the electrical load 170.

[0041] The battery pack 60 has, for example, 12 cells 62 (see Figure 2), connected in 3 parallel and 4 series. Figure 5 shows three cells 62 connected in parallel represented by a single battery symbol. The cells are not limited to prismatic cells; they may be cylindrical cells or pouch cells with a laminated film case.

[0042] The battery pack 60, current sensor 53, and relay 55 are connected in series via power lines 57P and 57N. Power lines 57P and 55N can be busbars BSB (see Figure 2), which are plate-shaped conductors made of a metal material such as copper.

[0043] As shown in Figure 5, power line 57P connects the positive external terminal 51 to the positive terminal of the battery pack 60. Power line 57N connects the negative external terminal 52 to the negative terminal of the battery pack 60.

[0044] External terminals 51 and 52 are terminals for connecting the battery 50 to the automobile 10 (electrical load 170 and capacitor 180). The battery 50 can be electrically connected to the electrical load 170, capacitor 180 and alternator via external terminals 51 and 52.

[0045] The current sensor 53 is located on the negative power line 57N. The current sensor 53 may also be a metal plate resistor (shunt resistor). The current sensor 53 measures the current I of the battery pack 60 based on the voltage Vr across the resistor. The current sensor 53 can distinguish between discharge and charge based on the polarity (positive or negative) of the voltage Vr across its terminals.

[0046] The voltage detection unit 54 measures the cell voltage Vs of each cell 62 and the total voltage Vt of the battery pack 60 (see Figure 6). The temperature sensor 58 is attached to the battery pack 60 and detects the temperature of the battery pack 60 or its surroundings.

[0047] Relay 55 is provided on the positive power line 57P. Relay 55 is preferably a self-holding switch such as a latching relay. This embodiment uses a latching relay.

[0048] Relay 55 is held in a closed state by energizing the relay coil 133A, which will be described later, by passing current through it. It is held in an open state by energizing the relay coil 133B, which will be described later, by passing current through it. The latching relay 55 can maintain the state of its contacts even if the current to the relay coils 133A and 133B is interrupted. Alternatively, a single-winding latching relay with one coil shared for both opening and closing may be used.

[0049] Relay 55 is a normally closed type and is controlled to be closed under normal circumstances. If there is any abnormality in battery 50, the relay 55 can be switched from closed to open, thereby interrupting the current I of the battery pack 60.

[0050] The relay control circuit 110 includes a bypass circuit 120 and a drive circuit 130. The bypass circuit 120 comprises a first switch 121, a second switch 123, and a diode 125. In this embodiment, P-channel FETs (field-effect transistors) are used for the first switch 121 and the second switch 123. The first switch 121 and the second switch 123 may also be N-channel FETs.

[0051] The first switch 121 has its source S connected to one end (point A) of the relay 55. The diode 125 has its anode connected to the drain D of the first switch 121 and its cathode connected to the drain D of the second switch 123. The second switch 123 has its source S connected to the other end (point B) of the relay 55.

[0052] Diode 125 ensures that the discharge direction of the battery pack 60 is forward. The two switches 121 and 123 connect the drains together (in this example, via diode 125), forming a back-to-back connection. A back-to-back connection is a wiring configuration that connects the sources of two FETs together or the drains together.

[0053] The first switch 121 has a parasitic diode D1, and the second switch 123 has a parasitic diode D2. Parasitic diode D1 has a forward charging direction, and parasitic diode D2 has a forward discharging direction, so they are in opposite directions.

[0054] The bypass circuit 120 is connected in parallel with the relay 55. By closing the first switch 121 and the second switch 123, the battery pack 60 can discharge to the electrical load 170 while the relay is open, as shown in Figure 7. Charging while the relay is open is interrupted by the diode 125.

[0055] The drive circuit 130 comprises a first drive circuit 131A and a second drive circuit 131B. The first drive circuit 131A is for closed circuits, and the second drive circuit 131B is for open circuits.

[0056] The first drive circuit 131A includes a relay coil 133A and a control switch 135A. The relay coil 133A and the control switch 135A are connected in series.

[0057] One end of the relay coil 133A is connected to the cathode of the diode 125. The other end of the relay coil 133A is connected to one end of the control switch 135A. The other end of the control switch 135A is connected to the negative terminal (point C in Figure 5) of the battery pack 60. The negative terminal of the battery pack 60 corresponds to the reference potential of the present invention.

[0058] The second drive circuit 131B includes a relay coil 133B and a control switch 135B. The second drive circuit 131B is the same circuit as the first drive circuit 131A and is connected in parallel to the first drive circuit 131A.

[0059] The management device 150 is mounted on the circuit board 100 (see Figure 2) and includes a CPU 151 and memory 153, as shown in Figure 5.

[0060] The control device 150 monitors the status of the battery 50 based on the outputs of the current sensor 53, the voltage detection unit 54, and the temperature sensor 58. In other words, it monitors the temperature, current I, and total voltage Vt of the battery pack 60.

[0061] The control device 150 determines that the battery 50 is overvoltage if the total voltage Vt of the battery pack 60 is above the upper limit voltage. If the total voltage Vt of the battery pack 60 is below the lower limit voltage, the control device 150 determines that the battery 50 is undervoltage. Overvoltage and undervoltage may also be determined by the cell voltage Vs. The control device 150 determines that the battery 50 is overcurrent if the current I is above a threshold. The control device 150 controls the relay 55 based on the monitoring results of the battery 50.

[0062] Memory 153 stores a battery monitoring program, a relay control program, a relay fault detection program, and data necessary for the execution of these programs. The programs may be stored on a recording medium such as a CD-ROM for use, transfer, lending, etc. The programs may also be distributed via telecommunications lines.

[0063] 2. Operation of the relay control circuit <Switch Description> (A) First switch 121 of bypass circuit 120 (B) Second switch 123 of bypass circuit 120 (C) Control switch 135A of the first drive circuit 131A (D) Control switch 135B of the second drive circuit 131B

[0064] <Relay operation> By closing switches (A) and (C), an excitation current Ic flows through the battery pack 60, bypass circuit 120, and first drive circuit 131A, as shown in Figure 8, and thus the relay 55 can be closed.

[0065] By closing switches (B) and (D), an excitation current Ic flows through the battery pack 60, bypass circuit 120, and second drive circuit 131B, as shown in Figure 9, allowing relay 55 to be opened.

[0066] As shown in Figure 10, even if switch (A) is closed instead of switch (B), the excitation current Ic can still flow through the battery pack 60, bypass circuit 120, and second drive circuit 131B, thus allowing relay 55 to be opened.

[0067] When opening relay 55, the two current paths shown in Figures 9 and 10 may be used interchangeably depending on the type of malfunction.

[0068] In this embodiment, in the case of low voltage or overcurrent, an excitation current Ic is passed through the current path via the second switch 123 (path shown in Figure 9) to open the relay 55, and in the case of overvoltage, an excitation current Ic is passed through the current path via the first switch 121 (path shown in Figure 10) to open the relay 55 (see Figure 11).

[0069] In the event of overvoltage, the current path via the first switch 121 (the path shown in Figure 10) is selected. Even after the relay 55 is opened due to overvoltage detection, discharge current can still flow from the battery pack 60 to the electrical load 170 of the automobile 10 via the parasitic diode D2 of the second switch 123 until the first switch 121 is opened. However, the current carrying capacity of the bypass circuit 120 is lower than that of the relay 55. Therefore, it is preferable to limit the current to prevent the bypass circuit 120 from failing.

[0070] In this configuration, whether relay 55 is open or closed, two of the four switches (A), (B), (C), and (D) must be closed for the excitation current to flow through the relay coils 133A and 133B.

[0071] Therefore, even if one of the four switches (A), (B), (C), or (D) malfunctions, relay 55 will not be activated unintentionally.

[0072] <Fault detection for relay 55> If relay 55 experiences an open fault, it will not be able to interrupt the current I even if an abnormality occurs. Therefore, it is preferable to detect the open fault of relay 55. An open fault is a failure in which relay 55 does not open due to contact sticking or the like.

[0073] By closing the three switches (A), (B), and (D), an open fault can be detected based on whether or not a change occurs in the measured value of the current sensor 53.

[0074] After the three switches (A), (B), and (D) are closed, and before the relay 55 is opened, current I flows through the path L1 from the battery pack 60, relay 55, second switch 123, relay coil 133B, control switch 135B, and battery pack 60, as shown in Figure 12. At this time, if the battery 50 is neither charging nor discharging via the external terminals 51 and 52, almost no current I flows through the current sensor 53, and the measured value of the current sensor 53 is zero. Even if the battery 50 is discharging a dark current to the automobile 10 via the external terminals 51 and 52, only a small current of several tens of mA flows through the current sensor 53, and the measured value of the current sensor 53 is below a predetermined value. The predetermined value is, for example, 100 mA.

[0075] In the path L1 shown in Figure 12, current flows through the relay coil 133B, causing it to be energized. After the relay coil 133B is energized, if the relay 55 opens normally, the current path switches from path L1 in Figure 12 to path L2 in Figure 13.

[0076] When the current path switches to path L2, as shown in Figure 13, current I flows through the path of the automobile 10, from capacitor 180, positive external terminal 51, second switch 123, relay coil 133B, control switch 135B, current sensor 53, and negative external terminal 52.

[0077] After the relay opens, the current I flowing through the current sensor 53 increases by the amount of current flowing through the path L2 shown in Figure 13 compared to before the relay opens. Therefore, an open fault in the relay 55 can be detected based on the change in the measured value of the current sensor 53 before and after the relay opens.

[0078] If relay 55 does not open after the relay coil 133B is energized, but remains closed (in the case of a malfunction), the current path does not change and continues to flow through path L1 in Figure 12, so there is no change in the measured value of the current sensor 53.

[0079] In other words, if, after energizing the relay coil 133B, the measured value of the current sensor 53 changes from zero or below a predetermined value to an increasing current, it can be determined that an open fault has not occurred. If the measured value remains zero or below a predetermined value and there is no change in current, it can be determined that an open fault may have occurred.

[0080] Furthermore, it is desirable to perform fault detection of relay 55 at a time other than when battery 50 is being charged.

[0081] The reason for avoiding fault detection during charging is that, during charging, a current I exceeding a predetermined value flows through the current sensor 53 not only when the relay 55 is open, but also when it is closed. Therefore, it is difficult to determine with accuracy whether the relay 55 is open or closed, as the measured value of the current sensor 53 does not change easily before and after the relay opens.

[0082] The reason for closing not only the second switch 123 but also the first switch 121 during fault detection is to allow discharge to the automobile 10 even during fault detection.

[0083] Figure 14 is a flowchart of the fault detection process for relay 55. The fault detection process for relay 55 is performed, for example, when the vehicle is parked and the battery 50 is not charging, that is, when there is no current or when it is discharging a dark current.

[0084] The management device 150 detects vehicle parking and, upon confirming that it is not charging, executes a fault detection process. Vehicle parking can be determined from the measurement value of the current sensor 53. If the measurement value of the current sensor 53 remains below a predetermined value for a predetermined period of time, it can be determined that the vehicle is parked. Charging can be determined from the polarity of the measurement value of the current sensor 53.

[0085] In the state before fault detection, the first switch 121 and the second switch 123 of the bypass circuit 120, and the control switches 135A and 135B of the drive circuit 130 are all open. Relay 55 is closed, and the capacitor 180 of the automobile 10 is undischarged and charged to the same voltage as the terminal voltage (V1-V2) of the battery 50.

[0086] When the fault detection process starts, the control device 150 closes the first switch 121 and the second switch 123 of the bypass circuit 120 (S10).

[0087] Next, the control switch 135B of the second drive circuit 131B is closed (S20). The second drive circuit 131B is a drive circuit for open operation.

[0088] When the control switch 135B is closed, current I flows through the current path shown in Figure 12, and the relay coil 133B is energized. The energization of the relay coil 133B causes the relay 55 to open (S30).

[0089] When relay 55 opens, the current path switches from current path L1 shown in Figure 12 to current path L2 shown in Figure 13, and current I flows to current sensor 53.

[0090] The control device 150 detects the state of the relay 55 based on the measurement value of the current sensor 53 (S40).

[0091] The control device 150 determines that the relay 55 is normal (open) if the measured value of the current sensor 53 changes from below a predetermined value to above a threshold value before and after the excitation of the relay coil 133B (S50). The control device 150 determines that the relay 55 is faulty (closed) if the measured value of the current sensor 53 remains below a predetermined value without any change before and after the excitation of the relay coil 133B (S60). Note that the threshold value is greater than the predetermined value.

[0092] Subsequently, the control device 150 opens the control switch 135B of the second drive circuit 131B, and then closes the control switch 135A of the first drive circuit 131A (S70, S80). The first drive circuit 131A is a drive circuit for closing.

[0093] When the control switch 135A is closed, as shown in Figure 8, current I flows to the first drive circuit 131A through the battery pack 60 and the bypass circuit 120, and the relay coil 133A is energized. The relay 55 closes due to the energization of the relay coil 133A (S90).

[0094] Subsequently, the control device 150 opens the control switch 135A of the first drive circuit 131A, and further opens the first switch 121 and the second switch 123 of the bypass circuit 120 (S100, S110).

[0095] As a result, relay 55 closes, the first switch 121 and second switch 123 of the bypass circuit 120, and control switches 135A and 135B of the drive circuit 130 all open, returning to the state before fault detection.

[0096] The fault detection process for relay 55 is now complete. If a fault is detected in relay 55 during the fault detection process, the abnormality may be notified (by displaying an error message or illuminating an abnormality indicator light).

[0097] During the fault detection process, the resistance value Rc of the relay coil 133B can be determined based on the current I and capacitor voltage Vc measured after the relay opens.

[0098] Rc = Vc / I Vc is the voltage of capacitor 180. I is the current flowing through the current path L2 shown in Figure 13.

[0099] The capacitor voltage Vc is approximately equal to the terminal voltage (V1-V2) of the battery 50. Therefore, the capacitor voltage Vc can be calculated by measuring the voltages V1 and V2 at the positive and negative external terminals 51 and 52 using signal lines or the like with the control device 150.

[0100] Each time a fault is detected, the resistance value Rc of the relay coil 133B is measured, and the history is recorded in the memory 153, allowing the change in resistance value Rc over time to be determined. From the change in resistance value Rc over time, the deterioration of the relay coil 133B can be determined.

[0101] For example, if the resistance value Rc becomes smaller than the initial value, it can be determined that the relay coil 133B is more prone to current flow and its performance has deteriorated.

[0102] 3. Explanation of Effects This configuration allows the electrical load 170 of the automobile 10 to be discharged via the bypass circuit 120 even when the relay 55 is open (see Figure 7).

[0103] In this configuration, unless two of the four switches (A), (B), (C), and (D) are closed, the excitation current Ic will not flow to the relay coils 133A and 133B. Therefore, it is possible to prevent the relay 55 from operating unintentionally due to the malfunction of one switch.

[0104] This configuration uses the first switch 121 and the second switch 123 of the bypass circuit 120 as switches for relay control, thereby reducing the number of switches used for relay control.

[0105] One way to detect a fault in relay 55 is to detect the voltage drop VF across the diode. For example, as shown in Figure 15, relay 55 is opened and the voltage drop VF across diode 410 is detected.

[0106] However, with this method, if the capacitor 180 of the automobile 10 is charged, no current flows through the bypass circuit 400 even if the relay 55 is open. Therefore, the charge of the capacitor 180 must be discharged by the discharge circuit 450 before fault detection can be performed, and fault detection cannot be performed immediately after the vehicle is parked.

[0107] In this configuration, fault detection of the relay 55 can be performed without discharging the charge stored in the capacitor 180 of the automobile 10, and fault detection can be performed immediately after the vehicle is parked.

[0108] <Other Embodiments> The present invention is not limited to the embodiments described above and in the drawings, and the following embodiments, for example, are also included in the technical scope of the present invention.

[0109] (1) The cell (a rechargeable energy storage cell) 62 is not limited to a lithium-ion secondary battery cell, but may also be other non-aqueous electrolyte secondary battery cells. The cell 62 may be connected in series or parallel, or it may be connected in series or as a single cell. A capacitor can also be used instead of a secondary battery cell. Secondary battery cells and capacitors are examples of cells.

[0110] (2) In the above embodiment, the battery 50 was mounted on the automobile 10, but it may also be mounted on a mobile body other than a vehicle, such as a ship or an aircraft. Furthermore, it may not be limited to mobile bodies, but may also be used for stationary applications such as energy storage devices for absorbing fluctuations in distributed power generation systems or UPS (uninterruptible power supply).

[0111] (3) In the above embodiment, when the relay 55 is open, the fault of the relay 55 is detected by focusing on the current flowing from the capacitor 180 of the automobile 10 to the drive circuit 130. The capacitor 180 may be provided in the battery 250 as long as it is connected between the positive and negative external terminals 51 and 52, as shown in Figure 16. When the relay 55 is open, the fault of the relay 55 may also be detected by detecting the current I flowing from the capacitor 180 of the battery 250 to the drive circuit 130 with the current sensor 53. In addition, the capacitor 180 can be replaced with a backup battery or the like, except when it has a higher voltage than the battery 50.

[0112] (4) In the above embodiment, the excitation current Ic is supplied to both the first drive circuit 131A for opening and the second drive circuit 131B for closing via the bypass circuit 120. The excitation current Ic may be supplied to only one of the two drive circuits 131A and 131B via the bypass circuit 120. For example, the excitation current may be supplied only to the drive circuit 131B for opening via the bypass circuit 120. The drive circuit 131A for closing may be supplied with excitation current Ic without going through the bypass circuit 120. The drive circuit 131A for closing may consist of only one switch.

[0113] (5) In the above embodiment, the first switch 121 and the second switch 123 were FETs. The first switch 121 and the second switch 123 may be semiconductor switches other than FETs. For example, they may be bipolar transistors. Also, any switch that can be electrically controlled may be a switch other than a semiconductor.

[0114] (6) In the above embodiment, an open fault of relay 55 was detected based on the change in the measured value of the current sensor 53 before and after the excitation of relay coil 133B (S20, S30). Alternatively, a closed fault of relay 55 may be detected based on the change in the measured value of the current sensor 53 before and after the excitation of relay coil 133A (S80, S90). A closed fault is a fault in which relay 55 is stuck in the open position and does not close. Detection of a closed fault may be performed at the same time as detection of an open fault, or at a different timing. [Explanation of symbols]

[0115] 50. Battery (energy storage device) 53 Current Sensor 55 Relay 60 battery packs 62 cells 110 Relay control circuit 120 Bypass Circuit 121 Switch 1 123 Second switch 125 diodes 130 Drive Circuit 131A First drive circuit 133A Relay Coil 135A control switch 131B Second drive circuit 133B Relay Coil 135B Control Switch 150 Management device

Claims

1. A relay control circuit for interrupting the current in a cell, A bypass circuit connected in parallel to the relay, The drive circuit includes a drive circuit for driving the relay, The bypass circuit is A first switch and a second switch connected in series, A diode is positioned between the first switch and the second switch such that the anode is connected to the first switch and the cathode to the second switch, and the discharge direction of the cell is forward, The aforementioned drive circuit is A relay coil connected to the cathode of the diode, A relay control circuit, comprising: a control switch connected in series with the relay coil and connecting the relay coil to a reference potential.

2. A relay control circuit according to claim 1, The aforementioned drive circuit is A first drive circuit for closing, It includes a second drive circuit for open circuits, By closing the two switches, the first switch and the control switch of the first drive circuit, and allowing current to flow to the relay coil of the first drive circuit, the relay is switched to the closed position. A relay control circuit that opens the relay by closing the two switches, the second switch and the control switch of the second drive circuit, and allowing current to flow through the relay coil of the second drive circuit.

3. A relay control circuit according to claim 1, The aforementioned drive circuit is A first drive circuit for closing, It includes a second drive circuit for open circuits, The first switch and the second switch are FETs connected back-to-back via the diode, A relay control circuit that, when an overvoltage is detected in the cell, closes the first switch and the control switch of the second drive circuit, thereby opening the relay by allowing current to flow through the relay coil of the second drive circuit.

4. It is an energy storage device, Positive and negative external terminals, A cell connected to the positive and negative external terminals, A relay that interrupts the current in the aforementioned cell, A current sensor for measuring the current of the aforementioned cell, Management device and A power storage device comprising a relay control circuit according to any one of claims 1 to 3.

5. The energy storage device according to claim 4, The energy storage unit is connected between the positive and negative external terminals of the aforementioned energy storage device. The aforementioned drive circuit is It comprises a first drive circuit for closing and a second drive circuit for opening, The aforementioned control device is The first switch, the second switch, and the control switch of the second drive circuit are closed, and the relay is opened by allowing current to flow through the relay coil of the second drive circuit. An energy storage device that detects an open fault in the relay based on the change in the measured value of the current sensor before and after the relay opens.

6. The energy storage device according to claim 5, The aforementioned control device is Based on the measured value of the current sensor after the relay is opened and the voltage of the energy storage unit, the resistance value of the second drive circuit is calculated and recorded. A power storage device that determines the deterioration state of the second drive circuit based on the change in the resistance value of the second drive circuit over time.

7. The energy storage device according to claims 5 and 6, The aforementioned control device is A power storage device that performs fault detection of the relay when the cell is not charged.

Images