Battery Charging Device

Abstract

This battery charging device comprises: a rectifying unit which outputs, as charging power for a battery, direct-current power obtained by rectifying three-phase alternating-current power by means of conduction of switch elements connected to respective output signal lines of the three-phase alternating-current power, the three-phase alternating-current power being output by an electric power generator in accordance with the rotation of a rotor; a power source maintaining switch capable of maintaining a state in which control power for the switch elements, from the battery, can be supplied when a main switch is in an interrupting state stopping the supply of the control power to a power source supply line; and a control unit which controls the conduction of the switch elements and which, if the main switch is turned to the interrupting state, maintains the power source maintaining switch in a state in which the control power for the switch elements can be supplied, and if the rotor is rotating, controls negative electrode side switch elements connected to a negative electrode of the battery to a conducting state.

Description

Technical Field

[0001] The present invention relates to a battery charging device. This application claims priority based on Japanese Patent Application No. 2022-120340 filed in Japan on July 28, 2022, the content of which is incorporated herein by reference.

Background Art

[0002] In recent years, battery charging devices mounted on vehicles such as motorcycles have been known (see, for example, Patent Document 1). In such a conventional battery charging device, three-phase AC power output from a generator is rectified by a full-bridge configuration using a switching element such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) to convert it into DC power for charging the battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in a conventional battery charging device, for example, when the main switch is turned off and the supply of power (control power of the switching element) is stopped while the generator is rotating (while the vehicle is running), the control of the switching element stops. Therefore, the AC power generated by the generator may be rectified by the parasitic diode of the switching element. In this case, since it is rectified by a high-resistance parasitic diode, the switching element may generate heat and an abnormality may occur in the device, and there is a possibility of overcharging the battery.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a battery charging device capable of suppressing heat generation that occurs when the supply of power source power stops during the rotation of a generator and suppressing overcharging of a battery.

Means for Solving the Problems

[0006] To solve the above problems, one aspect of the present invention includes a rectifying unit that outputs, as charging power for a battery, DC power obtained by rectifying three-phase AC power output by a generator through conduction of switch elements connected to respective output signal lines of the three-phase AC power in response to rotation of a rotor, a main switch that supplies control power for the switch elements from the battery to a power supply line, a power holding switch capable of holding the control power for the switch elements from the battery in a state where it can be supplied when the main switch is in an off state in which the supply of the control power to the power supply line is stopped, and a control unit that controls conduction of the switch elements. The control unit holds the power holding switch in a state where it can supply the control power for the switch elements when the main switch enters the off state, and controls the negative-side switch element connected to the negative terminal of the battery to be in a conducting state when the rotor is rotating. The battery charging device includes the above components.

[0007] Also, in one aspect of the present invention, in the above battery charging device, the switch element is a MOS (Metal Oxide Semiconductor) transistor, the rectifying unit includes a positive-side MOS transistor connected between a positive-side power supply line connected to the positive terminal of the battery and the output signal line for each of the output signal lines, and a negative-side MOS transistor connected between a negative-side power supply line connected to the negative terminal of the battery and the output signal line, and forms a rectifying bridge. The control unit may control the negative-side MOS transistor included in the rectifying bridge to be in a conducting state when the rotor is rotating.

[0008] Also, in one aspect of the present invention, in the battery charging device described above, the control unit may alternately and repeatedly execute a rotation detection process of detecting whether the rotor is rotating by turning off the MOS transistor on the positive electrode side and the MOS transistor on the negative electrode side for a predetermined period, and a conduction process of controlling the MOS transistor on the negative electrode side to be in a conductive state.

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

[0010] Also, in one aspect of the present invention, in the battery charging device described above, a rotation detection unit that detects whether the rotor is rotating based on the DC voltage obtained by rectifying the three-phase AC power by a diode is provided, and the control unit may detect whether the rotor is rotating based on the detection result of the rotation detection unit.

[0011] Also, in one aspect of the present invention, in the battery charging device described above, when the control unit detects the stop of the rotor, the control unit may switch the power supply holding switch to a state where the control power of the switch element is not supplied.

Advantages of the Invention

[0012] According to the present invention, when the main switch is in an off state, the battery charging device secures the control power of the switch element of the rectifying unit by the power supply holding switch, and when the rotor of the generator is rotating, the switch element on the negative electrode side is turned on to control the output signal line of the generator to the same potential as the negative electrode terminal of the battery. As a result, the battery charging device can suppress rectification by the parasitic diode of the switch element, so that it is possible to suppress heat generation that occurs when the supply of power stops during the rotation of the generator, and it is also possible to suppress overcharging (overvoltage) of the battery.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0014] Hereinafter, a battery charging device according to an embodiment of the present invention will be described with reference to the drawings.

[0015] FIG. 1 is a block diagram showing an example of a battery charging device 1 according to the present embodiment. As shown in FIG. 1, the battery charging device 1 includes a power supply holding switch 11, a power supply cutoff 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] Further, an ACG 2, a battery 3, a load unit 4, a main switch 5, a fuse 6, and a rotation position sensor 7 are connected to the battery charging device 1. The ACG (Alternating Current Generator) 2 is a generator that generates an alternating current signal. The ACG 2 outputs a three-phase (U-phase, V-phase, W-phase) alternating current signal in response to the rotation of a rotor (not shown). Here, the rotor is, for example, a crankshaft connected to the rotation shaft of an internal combustion engine (engine) of a motorcycle.

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

[0018] The load unit 4 is, for example, electrical components of a motorcycle, such as an ECU (Engine Control Unit), a fuel pump, an injection device, and various sensors. The load unit 4 is supplied with the generated power of the ACG 2 or the output power of the battery 3 via the main switch 5 and operates to consume power.

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

[0020] The fuse 6 is arranged between the power line L1 and the + electrode of the battery 3 to prevent overcurrent of the charging current to the battery 3 or the output current of the battery 3. The rotation position sensor 7 is a sensor that detects the rotation position of the ACG 2. The detection signal of the rotation position sensor 7 is input to the sensor input buffer 16 via the load unit 4 and the diode 18.

[0021] The rectifying unit 20 outputs the DC power obtained by rectifying the three-phase AC power as the charging power of the battery 3 by the conduction of the switch elements (21 to 26) connected to the respective output signal lines of the three-phase AC power output by the ACG 2. The rectifying unit 20 includes the switch elements (21 to 26) and the 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). The switch elements (21 to 26) have body diodes and are connected between the power supply line L1 and the ground line L2 so that the body diodes are forward oriented 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] The switch elements (24 to 26) are negative-side MOS transistors connected between a negative-side power supply line (ground line L2) connected to the negative terminal of the battery 3 and output signal lines (nodes N1 to N3).

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

[0026] In the rectification unit 20, the switch element 21 and the switch element 24 are connected in series via a node N1 between the power supply line L1 and the ground line L2, the switch element 22 and the switch element 25 are connected in series via a node N2 between the power supply line L1 and the ground line L2, and the switch element 23 and the switch element 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 power supply line L1 on the positive electrode side and the ground line L2, and flattens the DC voltage rectified by the rectifier bridge of the rectifying section 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 off state in which the supply of control power to the power supply lines (nodes N5 and N7) of the control power is stopped. The conduction of the power supply holding switch 11 is controlled by a control signal from the control section 30 described later. When the power supply holding switch 11 is in an off state (non-conducting state), the supply of control power is stopped. Also, when the power supply holding switch 11 is in an on state (conducting state), the control power can be supplied.

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

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

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

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

[0033] The sensor input buffer 16 receives the detection signal of 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 ACG2 to the control unit 30.

[0034] The resistor 17 is a pull-up resistor arranged between the node N7 and the node N8. The anode terminal of the diode 18 is connected to the node N8, and the cathode terminal is connected to the detection signal of the rotational position sensor 7 via the load unit 4. The diode 18 prevents the reverse flow of the detection signal of the rotational position sensor 7 to the node N8 via the load unit 4.

[0035] The rotation detection unit 19 detects whether the rotor is rotating based on the DC voltage (the voltage of the node N4) obtained by rectifying the three-phase AC power by the diodes (32 to 34). For example, the rotation detection unit 19 determines that the rotor is rotating when the voltage of the 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] The anode terminal of the diode 32 is connected to the node N1, and the cathode terminal is connected to the node N4, and outputs a DC voltage obtained by rectifying the U-phase AC signal in a system different from the rectifying unit 20. The anode terminal of the diode 33 is connected to the node N2, and the cathode terminal is connected to the node N4, and outputs a DC voltage obtained by rectifying the V-phase AC signal in a system different from the rectifying unit 20. The anode terminal of the diode 34 is connected to the node N3, and the cathode terminal is connected to the node N4, and outputs a DC voltage obtained by rectifying the W-phase AC signal in a system different from the rectifying unit 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) by the control voltage generated by the internal power supply generation unit 15.

[0038] The control unit 30 is a processor including, for example, a CPU (Central Processing Unit), and comprehensively controls 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 the rotation position information detected by the rotation position sensor 7 so that the rectifying unit 20 performs synchronous rectification and the battery 3 is appropriately charged. The control unit 30 outputs a control signal for controlling the conduction of the switch elements (21 to 26) via the FET driver unit 31.

[0039] Further, when the main switch 5 is turned off, the control unit 30 holds the power holding switch 11 in a state where it can supply the control power of 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 be in the on state (conducting state). That is, when the main switch 5 is in the off state and the rotor is rotating, the control unit 30 controls the negative-side MOS transistors (switch elements (24 to 26)) of the rectifying bridge of the rectifying unit 20 to be in the on state.

[0040] Note that the control unit 30 detects that the main switch 5 has been turned off (in the off state) using the power-off detection unit 14. Further, when the control unit 30 detects using the power-off detection unit 14 that the main switch 5 has been turned off (in the off state), it performs control to hold the power holding switch 11 in the on state.

[0041] Also, the control unit 30 alternately and repeatedly executes a rotation detection process of turning off the positive-side switch elements (21 to 23) and the negative-side switch elements (24 to 26) for a predetermined period to detect whether the rotor is rotating, and a conduction process of controlling the negative-side switch elements (24 to 26) to be in the on state.

[0042] Note that the control unit 30 detects whether the rotor is rotating based on the voltage output by the ACG 2 to the output signal lines (node N1, node N2, node N3). 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] Further, when the control unit 30 detects the stop of the rotor, the control unit 30 switches the power holding switch 11 to a state where the control power supply to the switch elements (21 to 26) is stopped. That is, when the control unit 30 detects the stop of the rotation of the rotor using the rotation detection unit 19, the control unit 30 performs control to switch the power holding switch 11 to the off state.

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

[0045] As shown in FIG. 2, the battery charging device 1 first determines whether it has detected the off state of the main switch 5 (step S101). The control unit 30 of the battery charging device 1 determines whether it has detected the off state of the main switch 5 based on the output of the power-off detection unit 14. Note that the power-off detection unit 14 detects that the main switch 5 is in the off state when the voltage of node N5 becomes equal to or lower than the threshold voltage. When the control unit 30 detects the off state of the main switch 5 (step S101: YES), the process proceeds to step S102. Further, when the control unit 30 detects the on state of the main switch 5 (step S101: NO), the process returns to step S101.

[0046] In step S102, the control unit 30 holds the power supply holding switch 11 in a state where the supply of control power is possible. That is, the control unit 30 controls the power supply holding switch 11 to be in the on state. Thereby, the power supply voltage of the power supply line L1 is supplied to the internal power supply generation unit 15 via the power supply holding switch 11 and the diode 13, ensuring the operating power of the control unit 30 and the FET driver unit 31.

[0047] Next, the control unit 30 detects the presence or absence of rotation of the ACG2 based on the output voltage of the ACG2 (step S103). First, the control unit 30 controls the positive-side switch elements (21 to 23) and the negative-side switch elements (24 to 26) to be in the off state, and the rotation detection unit 19 detects the presence or absence of rotation of the ACG2 based on the voltage of the node N4 obtained by rectifying the three-phase AC signal by the diodes (32 to 34). The control unit 30 detects the presence or absence of rotation of the ACG2 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). When the ACG2 (rotor) is rotating (step S104: YES), the control unit 30 proceeds with the process to step S105. Also, when the ACG2 (rotor) is not rotating (step S104: NO), the control unit 30 proceeds with the process to step S107.

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

[0050] Next, the control unit 30 maintains the state for a predetermined period (step S106). Note that this predetermined period corresponds to a cooling period during which a large current can flow because the negative-side switch elements (24 to 26) are controlled to be in the on state, and heat generation of the negative-side switch elements (24 to 26) is suppressed. After the process of step S106, the control unit 30 returns the process to step S103.

[0051] Also, in step S107, the control unit 30 switches the power - holding switch 11 to a state where the supply of control power is stopped. That is, when the rotation of the ACG2 (rotor) has stopped, the control unit 30 performs control to switch the power - holding switch 11 to the off state. After the process of step S107, the control unit 30 ends the process.

[0052] Also, FIG. 3 is a timing chart showing an example of the operation of the battery charging device 1 according to the present embodiment. In FIG. 3, each waveform shows, in order from the top, the state of the main switch 5 (waveform W1), the output of the power - off detection unit 14 (waveform W2), the state of the power - holding switch 11 (waveform W3), the states of the switch elements (21 - 23) on the positive - electrode side (waveform W4), the states of the switch elements (24 - 26) on the negative - electrode side (waveform W5), and the output of the rotation detection unit 19 (waveform W6). Also, the horizontal axis of each waveform indicates time.

[0053] As shown in FIG. 3, at time T1, when the main switch 5 is changed from the on state to the off state (see waveform W1), the output of the power - off detection unit 14 transitions from the power - supply state to the power - off state (see waveform W2). Also, even when the control unit 30 detects that the output of the power - off detection unit 14 has become the power - off state, the control unit 30 maintains the on state of the power - holding switch 11 (see waveform W3). Thereby, the power supply voltage of the power line L1 is supplied to the internal power generation unit 15 to secure the operating power of the control unit 30 and the FET driver unit 31. Note that, in FIG. 3, the hatched periods of the switch elements (21 - 23) on the positive - electrode side and the switch elements (24 - 26) on the negative - electrode side indicate the phase - control state. Also, in FIG. 3, it is assumed that the initial states of the main switch 5 and the power - holding switch 11 are both in the on state.

[0054] Next, at time T2, in order to detect the rotation of the ACG2, the control unit 30 turns off the positive-side switch elements (21 to 23) and the negative-side switch elements (24 to 26) (see waveforms W4 and W5). Then, the control unit 30 acquires the output of the rotation detection unit 19. Since rotation is detected, at time T3, while maintaining the power holding switch 11 in the on state (see waveform W3), the control unit 30 turns on the negative-side switch elements (24 to 26) (see waveforms W5 and W6).

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

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

[0057] Also, at time T8, again, in order to detect the rotation of the ACG2, the control unit 30 turns off the positive-side switch elements (21 to 23) and the negative-side switch elements (24 to 26) (see waveforms W4 and W5). Next, at time T9, the control unit 30 acquires the output of the rotation detection unit 19. Since no rotation is detected, the control unit 30 switches the power holding switch 11 to the off state (see waveform W3).

[0058] Note that in FIG. 3, the periods TR1 from time T2 to time T3, from time T4 to time T5, from time T6 to time T7, and from time T8 to time T9 are periods of rotation detection processing. Also, the periods TR2 from time T3 to time T4, from time T5 to time T6, and from time T7 to time T8 are periods of conduction processing and correspond to the cooling period of the rectifying unit 20.

[0059] In addition, in the present embodiment, the rotation detection processing period TR1 is set so as to be able to detect that the ACG2 (rotor) is rotating stably regardless of its rotation speed. Further, the conduction processing period TR2 (predetermined period) is set so as to appropriately suppress heat generation with respect to the period TR1.

[0060] As described above, the battery charging device 1 according to the present embodiment includes a rectifying unit 20, a power supply holding switch 11, and a control unit 30. The rectifying unit 20 rectifies three-phase AC power by turning on switch elements (21 to 26) connected to the output signal lines (node N1, node N2, node N3) of the three-phase AC power output by the ACG2 (generator) according to the rotation of the rotor, and outputs the rectified DC power as charging power for the battery 3. The power supply holding switch 11 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 that supplies the control power of the switch elements (21 to 26) from the battery 3 to the power supply line (power supply line L1) is in an off state where the supply to the control power supply line is stopped. The control unit 30 controls the conduction of the switch elements (21 to 26). Further, when the main switch 5 is turned off, the control unit 30 holds the power supply holding switch 11 in a state where it can supply the control power of 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 be in a conductive state.

[0061] As a result, when the main switch 5 of the battery charging device 1 according to the present embodiment is in the off state, the power holding switch 11 secures the control power of the switch elements (21 to 26) of the rectifying unit 20. When the rotor of the ACG2 is rotating, the switch elements (24 to 26) on the negative electrode side are turned on, and the output signal line of the ACG2 is controlled to the same potential as the negative electrode terminal (ground line L2) of the battery 3. Thereby, since the battery charging device 1 according to the present embodiment can suppress rectification by the parasitic diodes (body diodes) of the switch elements (21 to 26), it is possible to suppress heat generation that occurs when the supply of power is stopped during the rotation of the ACG2, and it is also possible to suppress overcharging (overvoltage) of the battery 3.

[0062] Also, in the present embodiment, the switch elements (21 to 26) are MOS transistors. The rectifying unit 20 includes a rectifying bridge. The rectifying bridge includes a positive electrode side MOS transistor (switch elements (21 to 23)) connected between the positive electrode side power line L1 connected to the positive electrode terminal of the battery 3 and the output signal line for each output signal line (node N1, node N2, node N3), and a negative electrode side MOS transistor (switch elements (24 to 26)) connected between the negative electrode side power line (ground line L2) connected to the negative electrode terminal of the battery 3 and the output signal line. The control unit 30 controls the negative electrode side MOS transistors (switch elements (24 to 26)) included in the rectifying bridge to be in the on state when the rotor is rotating.

[0063] Thereby, the battery charging device 1 according to the present embodiment can rectify efficiently by having the rectifying bridge, and can easily suppress heat generation by controlling the negative electrode side MOS transistors (switch elements (24 to 26)) included in the rectifying bridge to be in the on state.

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

[0065] As a result, the battery charging device 1 according to 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 the 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 (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 according to 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 therefore can appropriately detect whether the rotor is rotating with a simple configuration.

[0070] Also, in the present embodiment, when the control unit 30 detects the stop of the rotor, the power holding switch 11 is switched to a state where the control power supply to the switch elements (21 to 26) is stopped (for example, the off state).

[0071] Thereby, the battery charging device 1 according to the present embodiment switches the power holding switch 11 to a state where the control power supply to the switch elements (21 to 26) is stopped (for example, the off state), so that the power consumption during the stop (standby) of the device itself can be reduced. That is, the battery charging device 1 according to the present embodiment can reduce the dark current.

[0072] Note that the present invention is not limited to the above-described embodiment, and can be modified without departing from the gist of the present invention. For example, in the above-described embodiment, an example where the switch elements (21 to 26) are N-channel MOS transistors has been described, but the present invention is not limited to this, and other switch elements may be used as long as they are switch elements having parasitic diodes (body diodes).

[0073] Also, in the above-described embodiment, an example where the ACG2 outputs a three-phase AC signal has been described, but the present invention is not limited to this, and an AC signal of two phases or less or an AC signal of four phases or more may be output.

[0074] Also, in the above-described embodiment, an example where the rectifying unit 20 includes a rectifying bridge and full-wave rectifies an AC signal has been described, but the present invention is not limited to this, and other rectifying methods may be used.

[0075] Incidentally, the above-described battery charging device 1 has a computer system inside. And each process when the main switch 5 described above is turned off is stored in a computer-readable recording medium in the form of a program, and the above process is performed by the computer reading and executing this program. Here, the computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, etc. Also, this computer program may be distributed to the computer via a communication line, and the computer that has received this distribution may execute the program.

[0076] Also, in the above embodiment, part 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-described functions may be made into a processor individually, or part or all of them may be integrated and made into a processor.

[0077] Also, the method of integrating into a circuit is not limited to LSI, and it may be realized by a dedicated circuit or a general-purpose processor. Also, when a circuit integration technology that replaces LSI appears due to the progress of semiconductor technology, an integrated circuit using such technology may be used.

Explanation of Reference Numerals

[0078] 1 Battery charging device 2 ACG 3 Battery 4 Load section 5 Main switch 6 Fuse 7 Rotation position sensor 11 Power holding switch 12, 13, 18, 32, 33, 34 Diode 14 Power-off detection section 15 Internal power 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 Unit 31 FET Driver Unit

Claims

1. A rectifying unit that outputs, as charging power for the battery, DC power obtained by rectifying three-phase AC power output by a generator through conduction of a switching element connected to each output signal line of the three-phase AC power output according to the rotation of the rotor; A power holding switch capable of holding the control power of the switching element from the battery in a state where it can be supplied, when a main switch that supplies the control power of the switching element from the battery to a power supply line is in an off state in which the supply of the control power to the power supply line is stopped; A control unit that controls conduction of the switching element, and that holds the power holding switch in a state where it can supply the control power of the switching element when the main switch enters the off state, and that controls the switching element on the negative electrode side connected to the negative electrode terminal of the battery to be in a conductive state when the rotor is rotating; A battery charging device comprising the above.

2. The switching element is a MOS (Metal Oxide Semiconductor) transistor, The rectifying unit includes a rectifying bridge having a positive electrode side MOS transistor connected between a positive electrode side power supply line connected to the positive electrode terminal of the battery and the output signal line, and a negative electrode side MOS transistor connected between a negative electrode side power supply line connected to the negative electrode terminal of the battery and the output signal line, for each of the output signal lines; The control unit controls the negative electrode side MOS transistor included in the rectifying bridge to be in a conductive state when the rotor is rotating. The battery charging device according to Claim 1.

3. The control unit alternately and repeatedly executes a rotation detection process of detecting whether or not the rotor is rotating by turning off the positive electrode side MOS transistor and the negative electrode side MOS transistor for a predetermined period, and a conduction process of controlling the negative electrode side MOS transistor to be in a conductive state. The battery charging device according to Claim 2.

4. The control unit detects whether or not the rotor is rotating based on the voltage output by the generator to the output signal line. The battery charging device according to Claim 1.

5. A rotation detection unit that detects whether or not the rotor is rotating based on a DC voltage obtained by rectifying the three-phase AC power with a diode is provided. Based on the detection result of the rotation detection unit, the control unit detects whether the rotor is rotating or not. The battery charging device according to claim 4. **Claim 6** When the control unit detects the stop of the rotor, the control unit switches the power supply holding switch to a state where the control power of the switch element is not supplied. The battery charging device according to any one of claims 1 to 5.

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