Equipment for charging batteries.

Abstract

Invention details;

Description

Battery charging device

[0001] This application claims priority to Japanese Patent Application No. 2022-120340, filed on July 28, 2022, the contents of which are incorporated herein by reference.

[0002] In recent years, battery charging devices mounted on vehicles such as motorcycles have become known (see, for example, Patent Document 1). In such conventional battery charging devices, three-phase AC power output from a generator is rectified in a full-bridge configuration using switching elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) and converted into DC power for charging the battery.

[0003] JP 2012-120293 A

[0004] However, in conventional battery charging devices, for example, if the main switch is turned off while the generator is running (while the vehicle is running) and the supply of power from the power source (control power for the switch element) is stopped, control of the switch element stops, and the AC power generated by the generator may be rectified by the parasitic diode of the switch element. In this case, because the AC power is rectified by the high-resistance parasitic diode, the switch element may heat up, causing an abnormality in the device and potentially overcharging the battery.

[0005] The present invention has been made to solve the above problems, and its purpose is to provide a battery charging device that can suppress heat generation that occurs when the supply of power from the power source is stopped while the generator is rotating, and can also suppress overcharging of the battery.

[0006] In order to solve the above problems, one aspect of the present invention is a battery charging device comprising: a rectifier unit that rectifies three-phase AC power output by a generator and outputs DC power as charging power for a battery by conducting switch elements connected to each output signal line of the three-phase AC power in accordance with rotation of a rotor; a power supply holding switch that can hold a state in which control power from the battery can be supplied to the switch element when a main switch that supplies control power for the switch element from the battery to a power supply line is in an interrupted state in which the supply of the control power to the power supply line has been stopped; and a control unit that controls the conduction of the switch elements, so that when the main switch is in the interrupted state, the power supply holding switch is held in a state in which control power can be supplied to the switch element, and when the rotor is rotating, the control unit controls the switch element on the negative side connected to the negative terminal of the battery to an electrically conductive state.

[0007] In another aspect of the present invention, in the battery charging device described above, the switch elements are MOS (Metal Oxide Semiconductor) transistors, and the rectifier unit includes, for each of the output signal lines, a rectifier bridge having a positive-side MOS transistor connected between the output signal line and a positive-side power supply line connected to a positive terminal of the battery, and a negative-side MOS transistor connected between the output signal line and a negative-side power supply line connected to a negative terminal of the battery, and the control unit may be configured to control the negative-side MOS transistor of the rectifier bridge to a conductive state when the rotor is rotating.

[0008] In another aspect of the present invention, in the battery charging device described above, the control unit may alternately execute a rotation detection process for detecting whether the rotor is rotating by keeping the positive-side MOS transistor and the negative-side MOS transistor in a non-conductive state for a predetermined period of time, and a conduction process for controlling the negative-side MOS transistor to a conductive state.

[0009] In addition, one aspect of the present invention is that in the above-mentioned battery charging device, the control unit may detect whether the rotor is rotating based on the voltage output by the generator to the output signal line.

[0010] In addition, one aspect of the present invention may be such that, in the above-mentioned battery charging device, a rotation detection unit is provided that detects whether or not the rotor is rotating based on a DC voltage obtained by rectifying the three-phase AC power using a diode, and the control unit detects whether or not the rotor is rotating based on the detection result of the rotation detection unit.

[0011] In addition, in one aspect of the present invention, in the above-mentioned battery charging device, when the control unit detects that the rotor has stopped, it may switch the power supply holding switch to a state where the supply of control power to the switch element is stopped.

[0012] According to the present invention, when the main switch is turned off, the battery charging device uses the power supply holding switch to ensure control power for the switch element of the rectifier, and when the generator rotor is rotating, the negative side switch element is turned on to control the generator output signal line to the same potential as the negative terminal of the battery. This allows the battery charging device to suppress rectification by the parasitic diode of the switch element, thereby suppressing heat generation that occurs when the supply of power from the power source is stopped while the generator is rotating, and also suppressing overcharging (overvoltage) of the battery.

[0013] It is a block diagram showing an example of the battery charging device according to the present embodiment. It is a flowchart showing an example of the operation of the battery charging device according to the present embodiment. It is a timing chart showing an example of the operation of the battery charging device according to the present embodiment.

[0014] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A battery charging device according to an embodiment of the present invention will now be described with reference to the drawings.

[0015] 1 is a block diagram showing an example of a battery charger 1 according to this embodiment. As shown in FIG. 1, the battery charger 1 includes a power supply hold switch 11, a power supply interruption detection unit 14, an internal power supply generation unit 15, a sensor input buffer 16, a rotation detection unit 19, a rectification unit 20, a control unit 30, an FET driver unit 31, diodes (12, 13, 18, 32 to 34), and a resistor 17.

[0016] Also connected to the battery charging device 1 are an ACG 2, a battery 3, a load 4, a main switch 5, a fuse 6, and a rotational position sensor 7. The ACG (Alternating Current Generator) 2 is a generator that generates an AC signal. The ACG 2 outputs a three-phase (U-phase, V-phase, W-phase) AC signal in response to the rotation of a rotor (not shown). Here, the rotor is, for example, a crankshaft connected to the rotating shaft of an internal combustion engine of a motorcycle.

[0017] The battery 3 is, for example, a lead storage battery, and has a + (plus) electrode (positive terminal) connected to a positive power supply line L1 via a fuse 6, and a - (minus) electrode (negative terminal) connected to a ground terminal (ground line L2). The battery 3 can be charged with DC power obtained by rectifying, by a rectifier 20, three-phase (U-phase, V-phase, W-phase) AC signals generated by the ACG 2.

[0018] The load unit 4 is, for example, an electrical component of the motorcycle, such as an ECU (Engine Control Unit), a fuel pump, an injection system, various sensors, etc. The load unit 4 operates by receiving power generated by the ACG 2 or output power from the battery 3 via a main switch 5, and consumes power.

[0019] The main switch 5 is a switch disposed between the power line L1 and a node N5 (power supply line) and is used, for example, to start a motorcycle. The main switch 5 supplies control power for the switch elements (21 to 26) from the battery 3 to the power supply line (nodes N5 and N7).

[0020] The fuse 6 is disposed between the power supply line L1 and the positive electrode of the battery 3, and prevents an overcurrent in the charging current to the battery 3 or in the output current from the battery 3. The rotational position sensor 7 is a sensor that detects the rotational position of the ACG 2. The detection signal of the rotational position sensor 7 is input to a sensor input buffer 16 via the load section 4 and a diode 18.

[0021] The rectifier 20 outputs DC power obtained by rectifying the three-phase AC power as charging power for the battery 3, by turning on or off switch elements (21 to 26) connected to the output signal lines of the three-phase AC power output by the ACG 2. The rectifier 20 includes switch elements (21 to 26) and a capacitor 27.

[0022] The switch elements (21 to 26) are elements for synchronously rectifying the three-phase AC signals output by the ACG 2, and are, for example, N-channel MOS (Metal Oxide Semiconductor) transistors or FETs (Field Effect Transistors). Each of the switch elements (21 to 26) has a body diode and is connected between the power supply line L1 and the ground line L2 so that the body diode is forward-biased from the ground line L2 toward the power supply line L1.

[0023] The switch elements (21 to 23) are positive-side MOS transistors connected between the positive-side power supply line L1 connected to the positive terminal of the battery 3 and the output signal lines (nodes N1 to N3) of the three-phase AC signals, respectively.

[0024] In addition, the switch elements (24 to 26) are negative-side MOS transistors connected between the negative-side power supply line (ground line L2) connected to the negative terminal of the battery 3 and the output signal lines (nodes N1 to N3).

[0025] A rectifier bridge is formed by the positive-side MOS transistors (switch elements (21 to 23)) and the negative-side MOS transistors (switch elements (24 to 26)). That is, the rectifier unit 20 includes a rectifier bridge having the positive-side MOS transistors (switch elements (21 to 23)) and the negative-side MOS transistors (switch elements (24 to 26)).

[0026] In the rectification unit 20, the switch elements 21 and 24 are connected in series via a node N1 between the power supply line L1 and the ground line L2, the switch elements 22 and 25 are connected in series via a node N2 between the power supply line L1 and the ground line L2, and the switch elements 23 and 25 are connected in series via a node N3 between the power supply line L1 and the ground line L2.

[0027] The capacitor 27 is disposed between the positive power supply line L1 and the ground line L2 , and flattens the DC voltage rectified by the rectifier bridge of the rectifier unit 20 .

[0028] The power supply holding switch 11 is a switch that can hold the control power of the switch elements (21 to 26) from the battery 3 in a state where it can be supplied when the main switch 5 is in an interrupted state where the supply of control power to the power supply lines (nodes N5 and N7) has been stopped. The conduction of the power supply holding switch 11 is controlled by a control signal from the control unit 30, which will be described later. When the power supply holding switch 11 is in an off state (non-conductive state), the supply of control power is stopped. When the power supply holding switch 11 is in an on state (conductive state), the supply of control power is enabled.

[0029] The power supply interruption detection unit 14 detects, based on the voltage of the node N5, that the main switch 5 has been turned off and the supply of control power to the node N5 has been stopped. The power supply interruption detection unit 14 outputs the detection result to the control unit 30.

[0030] The diode 12 has an anode terminal connected to the node N5 and a cathode terminal connected to the node N7, and prevents the control power supplied via the power holding switch 11 from flowing back to the node N5.

[0031] The diode 12 has an anode terminal connected to the node N6 and a cathode terminal connected to a node N7, and prevents the control power supplied via the main switch 5 from flowing back to the node N6.

[0032] The internal power supply generating unit 15 generates a control voltage from the output power of the battery 3 supplied to the node N7 or the power rectified by the rectifying unit 20 to drive the switch elements (21 to 26) of the rectifying unit 20 and to operate the control unit 30. The control voltage generated by the internal power supply generating unit 15 is supplied to the control unit 30 and also to the FET driver unit 31.

[0033] The sensor input buffer 16 receives the detection signal from the rotational position sensor 7 via the load unit 4 and the diode 18, and converts it into a voltage that can be received by the control unit 30. The sensor input buffer 16 supplies a signal indicating the rotational position of the ACG 2 to the control unit 30.

[0034] Resistor 17 is a pull-up resistor disposed between node N7 and node N8. Diode 18 has an anode terminal connected to node N8 and a cathode terminal connected to the detection signal of rotational position sensor 7 via load section 4. Diode 18 prevents the detection signal of rotational position sensor 7 from flowing back to node N8 via load section 4.

[0035] The rotation detection unit 19 detects whether the rotor is rotating based on the DC voltage (voltage at node N4) obtained by rectifying three-phase AC power using diodes (32 to 34). The rotation detection unit 19 determines that the rotor is rotating, for example, when the voltage at node N4 is greater than the output voltage of the battery 3. The rotation detection unit 19 supplies a detection signal indicating whether the rotor is rotating to the control unit 30.

[0036] Diode 32 has an anode terminal connected to node N1 and a cathode terminal connected to node N4, and outputs a DC voltage obtained by rectifying a U-phase AC signal in a system separate from rectifier 20. Diode 33 has an anode terminal connected to node N2 and a cathode terminal connected to node N4, and outputs a DC voltage obtained by rectifying a V-phase AC signal in a system separate from rectifier 20. Diode 34 has an anode terminal connected to node N3 and a cathode terminal connected to node N4, and outputs a DC voltage obtained by rectifying a W-phase AC signal in a system separate from rectifier 20.

[0037] The FET driver unit 31 converts the control signal output by the control unit 30 into a drive signal for the switch elements (21 to 26). The FET driver unit 31 generates the drive signal for the switch elements (21 to 26) using the control voltage generated by the internal power supply generation unit 15.

[0038] The control unit 30 is, for example, a processor including a CPU (Central Processing Unit), and performs overall control of the battery charging device 1. When the main switch 5 is in the on state, the control unit 30 controls the switch elements (21 to 26) based on rotational position information detected by the rotational position sensor 7 so that the rectifier unit 20 performs synchronous rectification and the battery 3 is appropriately charged. The control unit 30 outputs control signals that control the conduction of the switch elements (21 to 26) via the FET driver unit 31.

[0039] Furthermore, when the main switch 5 is in an OFF state, the control unit 30 maintains the power supply holding switch 11 in a state in which it can supply control power to the switch elements (21 to 26), and when the rotor is rotating, controls the negative-side switch elements (24 to 26) connected to the negative terminal of the battery 3 to an ON state (conducting state). That is, when the main switch 5 is in an OFF state and the rotor is rotating, the control unit 30 controls the negative-side MOS transistors (switch elements (24 to 26)) of the rectifier bridge of the rectifier unit 20 to an ON state.

[0040] The control unit 30 detects that the main switch 5 has entered a cut-off state (off state) using the power cut-off detection unit 14. When the control unit 30 detects that the main switch 5 has entered a cut-off state (off state) using the power cut-off detection unit 14, the control unit 30 controls the power hold switch 11 to hold the power hold switch 11 in the on state.

[0041] In addition, the control unit 30 alternately executes a rotation detection process for detecting whether the rotor is rotating by turning the positive side switch elements (21 to 23) and the negative side switch elements (24 to 26) off (non-conductive state) for a predetermined period of time, and a conduction process for controlling the negative side switch elements (24 to 26) to the on state.

[0042] The control unit 30 detects whether the rotor is rotating based on the voltages output to the output signal lines (nodes N1, N2, and N3) by the ACG 2. Specifically, the control unit 30 detects whether the rotor is rotating based on the detection result of the rotation detection unit 19 described above.

[0043] Furthermore, when the control unit 30 detects that the rotor has stopped, it switches the power supply holding switch 11 to a state where the supply of control power to the switch elements (21 to 26) is stopped. That is, when the control unit 30 detects that the rotor has stopped rotating using the rotation detection unit 19, it performs control to switch the power supply holding switch 11 to the OFF state.

[0044] Next, the operation of the battery charging device 1 according to this embodiment will be described with reference to the drawings. Fig. 2 is a flowchart showing an example of the operation of the battery charging device 1 according to this embodiment. Fig. 2 illustrates the operation when the main switch 5 is changed from the ON state (control power supply state) to the OFF state (cut-off state).

[0045] 2 , the battery charging device 1 first determines whether or not the main switch 5 is in an off state (step S101). The control unit 30 of the battery charging device 1 determines whether or not the main switch 5 is in an off state based on the output of the power-off detection unit 14. The power-off detection unit 14 detects that the main switch 5 is in an off state when the voltage at node N5 is equal to or lower than a threshold voltage. If the control unit 30 detects that the main switch 5 is in an off state (step S101: YES), the control unit 30 proceeds to step S102. If the control unit 30 detects that the main switch 5 is in an on state (step S101: NO), the control unit 30 returns the process to step S101.

[0046] In step S102, the control unit 30 holds the power supply holding switch 11 in a state in which control power can be supplied. That is, the control unit 30 controls the power supply holding switch 11 to be in the on state. As a result, the power supply voltage of the power supply line L1 is supplied to the internal power supply generating unit 15 via the power supply holding switch 11 and the diode 13, thereby ensuring operating power for the control unit 30 and the FET driver unit 31.

[0047] Next, the control unit 30 detects whether or not the ACG 2 is rotating based on the output voltage of the ACG 2 (step S103). The control unit 30 first controls the positive-side switch elements (21 to 23) and the negative-side switch elements (24 to 26) to the OFF state, and the rotation detection unit 19 detects whether or not the ACG 2 is rotating based on the voltage at node N4 obtained by rectifying the three-phase AC signal using diodes (32 to 34). The control unit 30 detects whether or not the ACG 2 is rotating based on the detection result of the rotation detection unit 19.

[0048] Next, the control unit 30 determines whether the ACG2 (rotor) is rotating (step S104). If the ACG2 (rotor) is rotating (step S104: YES), the control unit 30 proceeds to step S105. If the ACG2 (rotor) is not rotating (step S104: NO), the control unit 30 proceeds to step S107.

[0049] In step S105, the control unit 30 turns on the negative-side switch elements (24 to 26) and outputs a control signal via the FET driver unit 31 to turn on the negative-side switch elements (24 to 26).

[0050] Next, the control unit 30 maintains the state for a predetermined period (step S106). This predetermined period corresponds to a cooling period during which the negative-side switch elements (24 to 26) are controlled to the ON state, allowing a large current to flow and suppressing heat generation in the negative-side switch elements (24 to 26). After processing step S106, the control unit 30 returns the process to step S103.

[0051] In step S107, the control unit 30 switches the power supply holding switch 11 to a state where the supply of control power is stopped. That is, when the rotation of the ACG 2 (rotor) has stopped, the control unit 30 performs control to switch the power supply holding switch 11 to the OFF state. After the processing of step S107, the control unit 30 ends the processing.

[0052] 3 is a timing chart showing an example of the operation of the battery charging device 1 according to this embodiment. In FIG. 3, the waveforms indicate, from top to bottom, the state of the main switch 5 (waveform W1), the output of the power interruption detector 14 (waveform W2), the state of the power hold switch 11 (waveform W3), the state of the positive-side switch elements (21-23) (waveform W4), the state of the negative-side switch elements (24-26) (waveform W5), and the output of the rotation detector 19 (waveform W6). The horizontal axis of each waveform indicates time.

[0053] As shown in FIG. 3 , when the main switch 5 is changed from the ON state to the OFF state at time T1 (see waveform W1), the output of the power interruption detection unit 14 transitions from the power supply state to the power interruption state (see waveform W2). Even if the output of the power interruption detection unit 14 detects the power interruption state, the control unit 30 maintains the power holding switch 11 in the ON state (see waveform W3). This allows the power supply voltage of the power line L1 to be supplied to the internal power generation unit 15, ensuring the operation of the control unit 30 and the FET driver unit 31. Note that in FIG. 3 , the hatched periods of the positive-side switch elements (21-23) and the negative-side switch elements (24-26) indicate the phase control state. Also, in FIG. 3 , the main switch 5 and the power holding switch 11 are both initially in the ON state.

[0054] Next, at time T2, the control unit 30 turns off the positive-side switch elements (21-23) and the negative-side switch elements (24-26) to detect rotation of the ACG 2 (see waveforms W4 and W5). Then, the control unit 30 acquires the output of the rotation detection unit 19 and, since rotation is detected, turns on the negative-side switch elements (24-26) at time T3 (see waveforms W5 and W6) while keeping the power holding switch 11 on (see waveform W3).

[0055] The control unit 30 maintains this state for a predetermined period (period TR2), and at time T4, the control unit 30 again turns off the positive side switch elements (21 to 23) and the negative side switch elements (24 to 26) in order to detect the rotation of the ACG2 (see waveforms W4 and W5).

[0056] Next, at time T5, the control unit 30 acquires the output of the rotation detection unit 19 and, since there is rotation, turns on the negative-side switch elements (24 to 26) again (see waveforms W5 and W6). The processing at times T6 and T7 is the same as the processing at times T4 and T5.

[0057] At time T8, the control unit 30 again turns off the positive-side switch elements (21 to 23) and the negative-side switch elements (24 to 26) to detect rotation of the ACG 2 (see waveforms W4 and W5). Next, at time T9, the control unit 30 acquires the output of the rotation detection unit 19 and, since there is no rotation, turns off the power holding switch 11 (see waveform W3).

[0058] 3, periods TR1 from time T2 to time T3, time T4 to time T5, time T6 to time T7, and time T8 to time T9 are periods for rotation detection processing, while periods TR2 from time T3 to time T4, time T5 to time T6, and time T7 to time T8 are periods for conduction processing, and correspond to cooling periods for the rectification unit 20.

[0059] In this embodiment, the period TR1 of the rotation detection process is set so as to be able to detect stable rotation regardless of the rotation speed of the ACG 2 (rotor), and the period TR2 (predetermined period) of the conduction process is set so as to appropriately suppress heat generation relative to the period TR1.

[0060] As described above, the battery charging device 1 according to this embodiment includes a rectifier 20, a power supply holding switch 11, and a control unit 30. The rectifier 20 outputs DC power obtained by rectifying three-phase AC power output from the ACG 2 (generator) as charging power for the battery 3 by turning on and off the switch elements (21-26) connected to the respective output signal lines (nodes N1, N2, and N3) of the three-phase AC power in response to the rotation of the rotor. The power supply holding switch 11 can maintain a state in which control power can be supplied to the switch elements (21-26) from the battery 3 when the main switch 5, which supplies control power for the switch elements (21-26) from the battery 3 to a power supply line (power supply line L1), is in an interrupted state in which the supply of control power to the power supply line is stopped. The control unit 30 controls the conduction of the switch elements (21-26). In addition, when the main switch 5 is turned off, the control unit 30 holds the power supply holding switch 11 in a state in which it can supply control power to the switch elements (21 to 26), and when the rotor is rotating, controls the negative side switch elements (24 to 26) connected to the negative terminal (ground line L2) of the battery 3 to a conductive state.

[0061] As a result, when the main switch 5 is turned off, the battery charging device 1 according to this embodiment ensures control power for the switch elements (21 to 26) of the rectifier 20 using the power supply holding switch 11, and when the rotor of the ACG 2 is rotating, turns on the negative side switch elements (24 to 26) to control the output signal line of the ACG 2 to the same potential as the negative terminal (ground line L2) of the battery 3. As a result, the battery charging device 1 according to this embodiment can suppress rectification by the parasitic diodes (body diodes) of the switch elements (21 to 26), thereby suppressing heat generation that occurs when the supply of power from the power source is stopped while the ACG 2 is rotating, and can also suppress overcharging (overvoltage) of the battery 3.

[0062] In this embodiment, the switch elements (21 to 26) are MOS transistors. The rectifier unit 20 includes a rectifier bridge. The rectifier bridge has, for each output signal line (node ​​N1, node N2, node N3), positive-side MOS transistors (switch elements (21 to 23)) connected between the output signal line and a positive-side power supply line L1 connected to the positive terminal of the battery 3, and negative-side MOS transistors (switch elements (24 to 26)) connected between the output signal line and a negative-side power supply line (ground line L2) connected to the negative terminal of the battery 3. When the rotor is rotating, the control unit 30 controls the negative-side MOS transistors (switch elements (24 to 26)) of the rectifier bridge to an on state.

[0063] As a result, the battery charging device 1 of this embodiment can rectify efficiently by having a rectifier bridge, and can easily suppress heat generation by controlling the negative side MOS transistors (switch elements (24 to 26)) of the rectifier bridge to the on state.

[0064] In addition, in this embodiment, the control unit 30 alternately executes a rotation detection process (processing for period TR1) for detecting whether the rotor is rotating by turning off the positive-side MOS transistors (switch elements (21 to 23)) and the negative-side MOS transistors (switch elements (24 to 26)) (non-conductive state) for a predetermined period, and a conduction process (processing for period TR2) for controlling the negative-side MOS transistors (switch elements (24 to 26)) to the on state.

[0065] As a result, the battery charging device 1 of this embodiment can accurately detect the rotation of the rotor while appropriately suppressing heat generation by the parasitic diodes (body diodes) of the switch elements (21 to 26) by alternately and repeatedly executing the rotation detection process (processing during period TR1) and the conduction process (processing during period TR2).

[0066] In this embodiment, the control unit 30 detects whether the rotor is rotating based on the voltages that the ACG2 outputs to the output signal lines (nodes N1, N2, and N3).

[0067] As a result, the battery charging device 1 of this embodiment uses the voltage that ACG2 outputs to the output signal lines (nodes N1, N2, and N3), and can therefore appropriately detect whether the rotor is rotating with a simple configuration.

[0068] The battery charging device 1 according to this embodiment also includes a rotation detection unit 19 that detects whether the rotor is rotating based on a DC voltage (the voltage at node N4) obtained by rectifying three-phase AC power using diodes (32 to 34). The control unit 30 detects whether the rotor is rotating based on the detection result of the rotation detection unit 19.

[0069] As a result, the battery charging device 1 of this embodiment detects whether the rotor is rotating based on the DC voltage (voltage at node N4) obtained by rectifying three-phase AC power using diodes (32 to 34), and can therefore appropriately detect whether the rotor is rotating with a simple configuration.

[0070] In addition, in this embodiment, when the control unit 30 detects that the rotor has stopped, it switches the power supply holding switch 11 to a state (for example, an OFF state) in which the supply of control power to the switch elements (21 to 26) is stopped.

[0071] As a result, the battery charging device 1 of this embodiment switches the power supply holding switch 11 to a state in which the supply of control power to the switch elements (21 to 26) is stopped (for example, to an OFF state), thereby reducing power consumption while the device is stopped (on standby). In other words, the battery charging device 1 of this embodiment can reduce dark current.

[0072] The present invention is not limited to the above-described embodiments, and modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiments, the switch elements (21 to 26) are N-channel MOS transistors, but the present invention is not limited to this, and other switch elements may be used as long as they have a parasitic diode (body diode).

[0073] In the above embodiment, an example has been described in which the ACG 2 outputs a three-phase AC signal, but this is not limited to this, and the ACG 2 may output an AC signal with two or less phases, or an AC signal with four or more phases.

[0074] In the above embodiment, the rectifier unit 20 is provided with a rectifier bridge and performs full-wave rectification on the AC signal, but this is not limited to this and other rectification methods may be used.

[0075] The battery charging device 1 described above has an internal computer system. The processes that are performed when the main switch 5 is turned off are stored in the form of a program on a computer-readable recording medium, and the computer reads and executes the program to perform the processes. Here, the computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like. Alternatively, the computer program may be distributed to a computer via a communication line, and the computer that receives the program may execute the program.

[0076] In the above embodiment, some or all of the functions of the battery charging device 1 may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each of the above functions may be implemented individually as a processor, or some or all of the functions may be integrated into a processor.

[0077] Furthermore, the integrated circuit method is not limited to LSI, and may be realized by a dedicated circuit or a general-purpose processor. Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology, an integrated circuit based on that technology may be used.

[0078] REFERENCE SIGNS LIST 1 Battery charging device 2 ACG 3 Battery 4 Load section 5 Main switch 6 Fuse 7 Rotation position sensor 11 Power supply holding switch 12, 13, 18, 32, 33, 34 Diode 14 Power supply interruption detection section 15 Internal power supply generation section 16 Sensor input buffer 19 Rotation detection section 20 Rectification section 21, 22, 23, 24, 25, 26 Switch element 27 Capacitor 30 Control section 31 FET driver section

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