Battery charging device, protection device, and protection method

Abstract

To protect a switching element when the supply of a power supply voltage stops during power generation.SOLUTION: A battery charging device includes: switching elements, conduction states of which are controlled so as to rectify an AC voltage generated by a generator and supply a charging voltage to a battery; a control signal generation unit that generates a control signal for the switching elements using a control voltage obtained by boosting a power supply voltage output from the battery; and a protection processing unit that stops the supply of the control voltage to the control signal generation unit to bring the switching elements into a non-conducting state when a differential voltage indicating the control voltage with reference to a voltage of a power line connected to the battery and connected to terminals of the switching elements on the battery side is less than or equal to a predetermined threshold voltage.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a battery charging device, a protection device, and a protection method. [Background technology]

[0002] When switching a voltage higher than the power supply voltage, the power supply voltage is boosted and used as a control signal for switching a switching element such as a metal oxide semiconductor field effect transistor (MOSFET) (see, for example, Patent Document 1). For example, in a conventional battery charging device, a switching element for converting an AC voltage generated by a generator into a charging voltage for a battery is controlled by a control power supply that is boosted from the power supply voltage output from the battery. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-246293 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, for example, in a battery charging device mounted on a motorcycle or the like, the main switch may be turned off during power generation by the generator, cutting off the power supply voltage to the battery. In this way, in a conventional battery charging device, when the supply of power supply voltage is stopped during power generation, the control voltage drops and switching elements such as MOSFETs are switched in an unsaturated region that is outside the saturated region. In this case, the resistance of the switching elements increases due to the drop in the control voltage, which may cause the switching elements to heat up and deteriorate or break down.

[0005] The present invention has been made to solve the above problems, and its object is to provide a battery charging device, a protection device, and a protection method that can protect a switching element when the supply of power supply voltage is stopped during power generation. [Means for solving the problem]

[0006] In order to solve the above problems, one aspect of the present invention is a battery charging device comprising: a switching element whose conductive state is controlled to rectify the AC voltage generated by a generator and supply a charging voltage to a battery; a control signal generating unit that generates a control signal for the switching element using a control voltage that is a boosted power supply voltage output from the battery; and a power supply line connected to the battery, which is a protection processing unit that stops the supply of the control voltage to the control signal generating unit and puts the switching element into a non-conductive state when a differential voltage indicating the control voltage based on the voltage of the power supply line connected to the battery side terminal of the switching element becomes equal to or lower than a predetermined threshold voltage.

[0007] Moreover, one aspect of the present invention is characterized in that, in the above-mentioned battery charging device, the protection processing unit includes a cut-off switch connected between a signal line to which the control voltage is supplied and the control signal generating unit, and cuts off conduction of the cut-off switch when the differential voltage becomes equal to or lower than the predetermined threshold voltage.

[0008] Moreover, one aspect of the present invention is characterized in that, in the above-mentioned battery charging device, the predetermined threshold voltage includes a first threshold voltage and a second threshold voltage lower than the first threshold voltage, and the protection processing unit cuts off the conduction of the cut-off switch when the differential voltage becomes equal to or lower than the second threshold voltage, and makes the cut-off switch conductive when the differential voltage becomes higher than the first threshold voltage.

[0009] Moreover, one aspect of the present invention is characterized in that, in the above-mentioned battery charging device, the protection processing unit cuts off the conduction of the cutoff switch when the differential voltage on the supply side of the control voltage of the cutoff switch becomes equal to or lower than the first threshold voltage and when the differential voltage on the control signal generating unit side of the cutoff switch becomes equal to or lower than the second threshold voltage, and makes the cutoff switch conductive when the differential voltage on the supply side of the control voltage of the cutoff switch becomes higher than the first threshold voltage or when the differential voltage on the control signal generating unit side of the cutoff switch becomes higher than the second threshold voltage.

[0010] In addition, one aspect of the present invention is characterized in that, in the battery charging device, the protection processing unit detects, by using a Zener diode, that the differential voltage has become equal to or lower than the predetermined threshold voltage.

[0011] Moreover, one aspect of the present invention is a protection device that protects a switching element that rectifies an AC voltage generated by a generator and supplies it to a high-potential power line by controlling the conductive state, and is characterized in that, when a differential voltage indicating a control voltage obtained by boosting a power supply voltage based on the voltage of the high-potential power line connected to the switching element becomes equal to or lower than a predetermined threshold voltage, the protection device includes a control signal generating unit that generates a control signal for the switching element using the control voltage, and a protection processing unit that stops supplying the control voltage to the control signal generating unit to bring the switching element into a non-conductive state.

[0012] Another aspect of the present invention is a protection method for a battery charging device including a switching element that rectifies an AC voltage generated by a generator by controlling its conductive state to supply a charging voltage to a battery, and a control signal generating unit that generates a control signal for the switching element using a control voltage that is a boosted power supply voltage output from the battery, wherein the protection processing unit includes a protection processing step that stops the supply of the control voltage to the control signal generating unit and brings the switching element into a non-conductive state when a differential voltage indicating the control voltage based on the voltage of a power supply line connected to the battery and connected to the battery side terminal of the switching element becomes equal to or lower than a predetermined threshold voltage. Effect of the Invention

[0013] According to the present invention, when a differential voltage indicating a control voltage based on the voltage of the power line connected to the battery side terminal of the switching element becomes equal to or lower than a predetermined threshold voltage, the protection processing unit stops the supply of the control voltage to the control signal generating unit to put the switching element into a non-conducting state. This allows the battery charging device to prevent the switching element from going into a conducting state in an unsaturated region that is a region outside the saturated region, and reduces heat generation of the switching element. Therefore, the battery charging device can protect the switching element when the supply of the power source voltage is stopped during power generation. [Brief description of the drawings]

[0014] [Figure 1] 1 is a block diagram showing an example of a battery charging device according to an embodiment of the present invention; [Diagram 2] 4 is a circuit diagram illustrating an example of the configuration of a protection processing unit in the present embodiment. FIG. [Diagram 3] 5 is a flowchart showing an example of the operation of the battery charging device according to the present embodiment. [Figure 4] 6 is a timing chart illustrating an example of the operation of the protection processing unit according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A battery charging device, a protection device, and a protection method according to an embodiment of the present invention will now be described with reference to the drawings.

[0016] FIG. 1 is a block diagram showing an example of a battery charging device 1 according to this embodiment. As shown in FIG. 1, the battery charging device 1 includes a diode 11, capacitors (12, 15-17), a DC / DC converter 13, a regulator 14, switching elements (21-23, 31-33), a gate driver 40, resistors (18, 42-44), and a protection processing unit 50.

[0017] The battery charging device 1 is connected to a generator 2, and is also connected to a battery 3 via a main switch unit 6. The battery charging device 1 is mounted on a vehicle such as a motorcycle, and rectifies AC power generated by the generator 2 and charges the battery 3. The main switch unit 6 includes a main switch 4 and a main relay 5, and controls the supply of the voltage (power supply voltage) of the battery 3 to the battery charging device 1.

[0018] The generator 2 is, for example, an ACG starter in which a starter motor and an ACG (alternating current generator) are integrated and directly connected to a crank. Here, the crankshaft is, for example, a rotor connected to the rotating shaft of an internal combustion engine of a motorcycle.

[0019] The battery 3 is, for example, a lead storage battery, with a negative (-) electrode connected to a ground terminal (ground line L1) and a positive (+) electrode connected to a power supply line L2. The positive electrode of the battery 3 is connected to a main switch 4 and a main relay 5 via the power supply line L2. In this embodiment, the output voltage of the battery 3 is defined as a voltage VBAT.

[0020] The main switch 4 is, for example, a main switch of a vehicle such as a motorcycle, and has a first end connected to the positive electrode (power line L2) of the battery 3 and a second end connected to a node N1 that supplies internal power. The main switch 4 is manually switched between an on state (connected state) and an off state (disconnected state) by a user.

[0021] A main relay 5 (an example of a main switch) is connected between the power supply line L2 and the power supply line L3. When the main switch 4 is turned on and the node N1 becomes the voltage VBAT, the main relay 5 is turned on and the power supply line L2 and the power supply line L3 are connected. When the main switch 4 is turned off, the main relay 5 is turned off and the power supply line L2 and the power supply line L3 are disconnected. In this embodiment, the voltage of the power supply line L3 is defined as a voltage VP. In this way, the main switch unit 6 controls the connection between the battery 3 and the power line L3 (switching elements 21 to 23 described later) and the connection between the battery 3 and the node N1 (DC / DC converter 13 described later).

[0022] The diode 11 has an anode terminal connected to the node N1 and a cathode terminal connected to the node N2. The diode 11 supplies the output voltage VBAT of the battery 3 to the DC / DC converter 13 and prevents a reverse current from flowing from the DC / DC converter 13 to the battery 3.

[0023] The capacitor 12 is a smoothing capacitor that is connected between the node N1 and the ground line L1 and smoothes the output voltage VBAT of the battery 3 that is supplied to the DC / DC converter 13.

[0024] The DC / DC converter 13 is, for example, a power supply device that generates a high voltage and a low voltage from the output voltage VBAT of the battery 3. The DC / DC converter 13 boosts the output voltage VBAT of the battery 3 to generate a voltage VH higher than the voltage VBAT as a control voltage, and outputs it to a signal line L4. The DC / DC converter 13 also generates a voltage lower than the voltage VH from the output voltage VBAT of the battery 3, and outputs it to a node N3. The voltage VBAT (power supply voltage) is supplied to the DC / DC converter 13 via the main switch 4.

[0025] The regulator 14 is, for example, a step-down regulator that generates a voltage VL for an ECU (Engine Control Unit). The regulator 14 supplies the generated voltage VL as an internal power supply for the ECU or the like.

[0026] The capacitor 15 is a smoothing capacitor that is connected between the node N3 and the ground line L1 and smoothes the output voltage that the DC / DC converter 13 outputs. The capacitor 16 is a smoothing capacitor that is connected between the output line of the regulator 14 and the ground line L1 and smoothes the output voltage VL that is output by the regulator 14.

[0027] The capacitor 17 is connected between the power supply line L3 and the ground line L1, and is a smoothing capacitor that smoothes the voltage VP, which is the output voltage of the battery or the voltage obtained by rectifying the AC voltage generated by the generator 2.

[0028] The switching elements 21 to 23 are, for example, N-type MOSFETs, and are high-side switching elements that drive a starter motor when the generator 2 is used as a starter motor. In this embodiment, the switching elements 21 to 23 will be described as the switching element 20 when indicating any high-side switching element provided in the battery charging device 1 or when no particular distinction is made. The switching element 20 rectifies the AC voltage generated by the generator 2 by controlling the ON state, and supplies the charging voltage to the battery 3.

[0029] In addition, since the switching element 20 is an N-type MOSFET, in order to reduce the on-resistance, the voltage of the control signal supplied to the gate terminal needs to be higher than the source-drain voltage, which is the voltage between the source terminal and the drain terminal. When the gate voltage drops compared to the source-drain voltage, the switching element 20 operates in a conductive state in the saturation region (unsaturated operation), and the on-resistance of the switching element 20 increases, causing heat generation.

[0030] The switching element 21 has a drain terminal connected to the power line L3 (high potential side power line), a source terminal connected to a node N6, and a control terminal (gate terminal) connected to a node N5. The node N6 is a signal line for a drive signal W when driving the generator 2 as a starter motor. The node N5 is a signal line for a control signal output by the gate driver 40 and driven by a control voltage VH.

[0031] The switching element 22 has a drain terminal connected to the power line L3, a source terminal connected to a node N7, and a control terminal (gate terminal) connected to an output line of a control signal of the gate driver 40 similar to the node N5. The node N7 is a signal line of a drive signal V when the generator 2 is driven as a starter motor. The gate terminal of the switching element 22 is driven by a control voltage VH in response to a control signal output by the gate driver 40.

[0032] The switching element 23 has a drain terminal connected to the power line L3, a source terminal connected to a node N8, and a control terminal (gate terminal) connected to an output line of a control signal of the gate driver 40 similar to the node N5. The node N8 is a signal line of a drive signal U when driving the generator 2 as a starter motor. The gate terminal of the switching element 23 is driven by a control voltage VH in response to a control signal output by the gate driver 40.

[0033] The switching elements 31 to 33 are, for example, N-type MOSFETs, and are low-side switching elements that drive the starter motor when the generator 2 is used as a starter motor. In this embodiment, the switching elements 31 to 33 will be described as the switching element 30 when indicating any low-side switching element provided in the battery charging device 1 or when no particular distinction is made.

[0034] The switching element 31 has a drain terminal connected to the node N6, a source terminal connected to the ground line L1 (low potential power supply line) via the resistor 18, and a control terminal (gate terminal) connected to an output line of a control signal from the gate driver 40. The node N6 is a signal line for a drive signal W when the generator 2 is driven as a starter motor.

[0035] The switching element 32 has a drain terminal connected to the node N7, a source terminal connected to the ground line L1 via the resistor 18, and a control terminal (gate terminal) connected to an output line of a control signal of the gate driver 40. The node N7 is a signal line for a drive signal V when the generator 2 is driven as a starter motor.

[0036] The switching element 33 has a drain terminal connected to the node N8, a source terminal connected to the ground line L1 via the resistor 18, and a control terminal (gate terminal) connected to an output line of a control signal of the gate driver 40. The node N8 is a signal line for a drive signal U when the generator 2 is driven as a starter motor.

[0037] The switching elements 20 (21-23) and the switching elements 30 (31-33) function as an inverter circuit when the generator 2 is driven as a starter motor. In addition, the switching elements 20 (21-23) and the switching elements 30 (31-33) function as a rectifier circuit that rectifies the AC voltage generated by the generator 2 when the battery 3 is charged from the generator 2.

[0038] The resistor 18 is connected between the switching element 30 (31 to 33) and the ground line L1. The resistor 18 is, for example, a shunt resistor, and is used to detect the current flowing through the inverter circuit when the generator 2 is driven as a starter motor.

[0039] The gate driver 40 (an example of a control signal generating unit) generates a control signal for the switching element 20 from a control voltage (voltage VH) obtained by boosting a power supply voltage (voltage VBAT) output from the battery 3. Although not shown for convenience of explanation, the gate driver 40 outputs control signals to the gate terminals of the switching element 22, the switching element 23, and the switching elements 31 to 33. The gate driver 40 generates the control signal for the switching element 20 based on control by a control unit (not shown). The gate driver 40 also includes a control switch 41 and resistors 42 to 44.

[0040] The resistor 42 has a first terminal connected to an output signal line (a control signal line of a control voltage VH) of a protection processing unit 50 described later, and a second terminal connected to a node N4. The resistor 43 has a first terminal connected to the node N4, and a second terminal connected to a node N5 (a gate terminal of the switching element 21). The resistor 44 has a first terminal connected to the node N5, and a second terminal connected to a signal line of a drive signal W. The resistors 42, 43, and 44 are connected in series between an output signal line (a control signal line for the control voltage VH) of the protection processing unit 50 and a signal line for the drive signal W.

[0041] The control switch 41 is a switch that controls the switching element 21, and is, for example, an N-type MOSFET. The control switch 41 has a source terminal connected to a node N6, a drain terminal connected to a node N4, and a gate terminal connected to a control signal line in the gate driver 40. When the control switch 41 is in an on state, it sets a node N5, which is the gate terminal of the switching element 21, to the same potential as the node N6, which is the signal line of the drive signal W, to turn the switching element 21 into an off state. When the control switch 41 is in an off state, it sets a node N5, which is the gate terminal of the switching element 21, to a high voltage to turn the switching element 21 into an on state.

[0042] The battery charging device 1 according to this embodiment includes a protection device 10 that protects a switching element 20 that is controlled in an on state to rectify the AC voltage generated by the generator 2 and supply a charging voltage to the battery 3. The protection device 10 includes a protection processing unit 50.

[0043] When a differential voltage (e.g., differential voltage ΔV1) indicating a control voltage based on the voltage of the power supply line L3 becomes equal to or lower than a predetermined threshold voltage (e.g., equal to or lower than threshold voltage Vth1), the protection processing unit 50 stops supplying the control voltage VH to the gate driver 40 and turns off the switching element 21. Here, the power supply line L3 is a power supply line connected to the battery 3 via the main switch unit 6 (main relay 5), and is connected to a terminal (drain terminal) of the switching element 21 on the battery 3 side. The differential voltage ΔV1 and the threshold voltage Vth1 will be described in detail later.

[0044] Now, with reference to FIG. 2, a detailed configuration of the protection processing unit 50 will be described. FIG. 2 is a circuit diagram illustrating an example of the configuration of the protection processing unit 50 in this embodiment.

[0045] As shown in FIG. 2, the protection processing unit 50 includes a cutoff switch 51, switches (52, 61, 63), resistors (53 to 56, 59, 60, 64, 65, 68), diodes (58, 62, 67), and Zener diodes (57, 66).

[0046] The cutoff switch 51 is, for example, a PNP bipolar transistor, and is connected between a signal line L4 to which a control voltage VH is supplied and the gate driver 40. The cutoff switch 51 has an emitter terminal connected to the signal line L4, a collector terminal connected to a signal line L5, and a base terminal connected to a node N14.

[0047] The switch 52 is, for example, a PNP bipolar transistor with an emitter terminal connected to the signal line L4, a collector terminal connected to a node N12, and a base terminal connected to a node N11.

[0048] The resistors 53 and 54 are connected in series between the node N12 and the node N16. The resistor 53 has a first terminal connected to the node N12 and a second terminal connected to a node N13 (the base terminal of the switch 61). The resistor 54 has a first terminal connected to the node N13 and a second terminal connected to the node N16.

[0049] The resistors 55 and 56 are connected in series between the power supply line L3 and the signal line L4 via a Zener diode 57 and a diode 58. The resistor 55 has a first terminal connected to the signal line L4 and a second terminal connected to a node N11. The resistor 56 has a first terminal connected to the node N11 and a second terminal connected to the cathode terminal of the Zener diode 57.

[0050] The Zener diode 57 is turned on when the differential voltage ΔV1 becomes higher than a threshold voltage Vth1 (first threshold voltage), and is turned off when the differential voltage ΔV1 becomes equal to or lower than the threshold voltage Vth1. The Zener diode 57 has an anode terminal connected to the anode terminal of the diode 58 and a cathode terminal connected to the second end of the resistor 56. Here, the differential voltage ΔV1 is a differential voltage indicating the control voltage VH based on the voltage of the power supply line L3 connected to the terminal of the switching element 20 on the battery 3 side, and is a value obtained by subtracting the voltage VH from the voltage VP of the signal line L4 (voltage VP-voltage VH). In other words, the differential voltage ΔV1 is a differential voltage on the DC / DC converter 13 side of the cutoff switch 51.

[0051] When the Zener diode 57 is in an on state, the switch 52 described above is in an on state, and when the Zener diode 57 is in an off state, the switch 52 described above is in an off state.

[0052] The diode 58 has an anode terminal connected to the anode terminal of the Zener diode 57 and a cathode terminal connected to the power supply line L3. The diode 58 prevents the voltage VP of the power supply line L3 from flowing back to the signal line L4.

[0053] The switch 63 is, for example, a PNP bipolar transistor with an emitter terminal connected to the signal line L5, a collector terminal connected to a node N12, and a base terminal connected to a node N17.

[0054] The resistors 64 and 65 are connected in series between the power supply line L3 and the signal line L5 via a Zener diode 66 and a diode 67. The resistor 64 has a first terminal connected to the signal line L5 and a second terminal connected to a node N17. The resistor 65 has a first terminal connected to the node N17 and a second terminal connected to the cathode terminal of the Zener diode 66.

[0055] The Zener diode 66 is turned on when the differential voltage ΔV2 becomes higher than a threshold voltage Vth2 (second threshold voltage), and is turned off when the differential voltage ΔV2 becomes equal to or lower than the threshold voltage Vth2. The Zener diode 66 has an anode terminal connected to the anode terminal of the diode 67 and a cathode terminal connected to the second end of the resistor 65. Here, the differential voltage ΔV2 is a differential voltage indicating the control voltage VH based on the voltage of the power supply line L3 connected to the terminal of the switching element 20 on the battery 3 side, and is a value obtained by subtracting the voltage VH from the voltage VP of the signal line L5 (voltage VP-voltage VH). That is, the differential voltage ΔV2 is a differential voltage on the gate driver 40 side of the cutoff switch 51. The threshold voltage Vth2 is lower (smaller) than the threshold voltage Vth1.

[0056] When the Zener diode 66 is in an on state, the switch 63 described above is in an on state, and when the Zener diode 66 is in an off state, the switch 63 described above is in an off state.

[0057] The diode 67 has an anode terminal connected to the anode terminal of the Zener diode 66 and a cathode terminal connected to the power supply line L3. The diode 67 prevents the voltage VP of the power supply line L3 from flowing back to the signal line L5.

[0058] The resistor 59 has a first terminal connected to the signal line L4 and a second terminal connected to a node N14. The resistor 60 has a first end connected to the node N14 and a second end connected to a node N15.

[0059] The switch 61 is, for example, an NPN bipolar transistor, with an emitter terminal connected to node N16, a collector terminal connected to node N15, and a base terminal connected to node N13. The switch 61 is turned on when either the switch 52 or the switch 63 is turned on, and is turned off when both the switch 52 and the switch 63 are turned off.

[0060] When the switch 61 is in the on state, the above-mentioned cutoff switch 51 is in the on state. When the switch 61 is in the off state, the above-mentioned cutoff switch 51 is in the off state and stops the supply of the control voltage VH to the gate driver 40.

[0061] The diode 62 has an anode terminal connected to the node N16 and a cathode terminal connected to the ground line L1. The diode 67 prevents the voltage VP of the ground line L1 from flowing back to the signal line L4.

[0062] The resistor 68 is connected between the signal line L5 and the ground line L1. When the cutoff switch 51 is turned off, the resistor 68 functions as a pull-down resistor that fixes the gate terminal of the switching element 20 to the potential of the ground line L1. By fixing the gate terminal to the potential of the ground line L1, the switching element 20 is turned off.

[0063] Next, the operation of the battery charger 1 according to this embodiment will be described with reference to the drawings. First, an example of the operation of the battery charger 1 in this embodiment will be described with reference to FIG.

[0064] 3 is a flowchart showing an example of the operation of the battery charger 1 according to this embodiment. Here, an overview of the processing of the protection processing unit 50 of the battery charger 1 will be described. The protection processing unit 50 of the battery charging device 1 in this embodiment stops supplying the control voltage VH to the gate driver 40 and turns off the switching element 20 when the differential voltage indicating the control voltage VH based on the voltage VP of the power line L3 becomes equal to or lower than a predetermined threshold voltage.

[0065] Here, the differential voltage includes a differential voltage ΔV1 based on a signal line L4 on the DC / DC converter 13 side of the shutoff switch 51 and a differential voltage ΔV1 based on a signal line L5 on the gate driver 40 side of the shutoff switch 51. In addition, the predetermined threshold voltage includes a threshold voltage Vth1 (first threshold voltage) by the Zener diode 57 and a threshold voltage Vth2 (second threshold voltage) by the Zener diode 66.

[0066] The predetermined threshold voltage is set so that the switching element 20 does not conduct in a saturated region (non-saturated operation). The threshold voltage Vth1 is set higher than the threshold voltage Vth2 (Vth1>Vth2).

[0067] 3, in the process of protecting the switching element 20, the protection processing unit 50 first determines whether or not the differential voltage ΔV1 is equal to or less than the threshold voltage Vth1 (step S101). The protection processing unit 50 determines whether or not the differential voltage ΔV1 is equal to or less than the threshold voltage Vth1 by using the Zener diode 57. If the differential voltage ΔV1 is equal to or less than the threshold voltage Vth1 (step S101: YES), the protection processing unit 50 advances the process to step S102. If the differential voltage ΔV1 is higher than the threshold voltage Vth1 (step S101: NO), the protection processing unit 50 advances the process to step S104.

[0068] In step S102, the protection processing unit 50 determines whether the differential voltage ΔV2 is equal to or less than the threshold voltage Vth2. The protection processing unit 50 determines whether the differential voltage ΔV2 is equal to or less than the threshold voltage Vth2 by the Zener diode 66. If the differential voltage ΔV2 is equal to or less than the threshold voltage Vth2 (step S102: YES), the protection processing unit 50 advances the process to step S103. If the differential voltage ΔV2 is higher than the threshold voltage Vth2 (step S102: NO), the protection processing unit 50 advances the process to step S104.

[0069] In step S103, the protection processing unit 50 changes the cutoff switch 51 from an on state to an off state. By changing the cutoff switch 51 from an on state to an off state, the protection processing unit 50 stops the supply of the control voltage VH to the gate driver 40 and turns off the switching element 20. After the process of step S103, the protection processing unit 50 returns the process to step S101.

[0070] Furthermore, in step S104, the protection processing unit 50 switches the shutoff switch 51 from an off state to an on state. By switching the shutoff switch 51 from an off state to an on state, the protection processing unit 50 supplies the control voltage VH to the gate driver 40 and releases the off state of the switching element 20. After the process of step S104, the protection processing unit 50 returns the process to step S101.

[0071] Next, the operation of the protection processing unit 50 will be described in detail with reference to FIG. In this embodiment, the protection processing unit 50 realizes the above-mentioned processing shown in Fig. 3 by the circuit shown in Fig. 2. Therefore, the details of the operation of the protection processing unit 50 will be described with reference to Fig. 4.

[0072] FIG. 4 is a timing chart illustrating an example of the operation of the protection processing unit 50 according to this embodiment. 4, waveforms W1 to W9 indicate, from top to bottom, the control voltage VH, power supply voltage VP, the state of the main switch 4, differential voltage ΔV1, differential voltage ΔV2, the state of switch 52, the state of switch 63, the state of switch 61, and the state of the cutoff switch 51. The horizontal axis of each waveform indicates time.

[0073] As shown in FIG. 4, at time T1, for example, when the main switch 4 is turned off while a vehicle such as a motorcycle is moving (see waveform W3), the supply of the output voltage VBAT of the battery 3 to the DC / DC converter 13 is stopped and the main relay 5 is turned off, cutting off the connection between the power supply line L3 and the battery 3.

[0074] This causes the operation of the DC / DC converter 13 to stop, and the control voltage VH drops (see waveform W1). Also, because the generator 2 is generating electricity, the power supply voltage VP of the power supply line L3 is no longer clamped by the output voltage VBAT of the battery 3, and rises (see waveform W2). As a result, the differential voltages ΔV1 and ΔV2 drop (see waveforms W4 and W5).

[0075] Next, at time T2, when the differential voltage ΔV1 becomes equal to or lower than the threshold voltage Vth1, the Zener diode 57 turns off, the node N11 becomes the control voltage VH, and the switch 52 turns from the on state to the off state (see waveform W6).

[0076] Next, at time T3, when the differential voltage ΔV2 becomes equal to or lower than the threshold voltage Vth2, the Zener diode 66 turns off, the node N17 becomes the control voltage VH, and the switch 63 turns from the on state to the off state (see waveform W7). As a result, both the switch 52 and the switch 63 turn off, so that the node N13 becomes the potential of the ground line L1, and as a result, the switch 61 turns from the on state to the off state (see waveform W8).

[0077] As a result, node N14 becomes the control voltage VH, and the shutoff switch 51 changes from the on state to the off state (see waveform W9). When the shutoff switch 51 changes to the off state, the supply of the control voltage VH to the gate driver 40 stops, and the signal line L5 is fixed to the potential of the ground line L1 by the resistor 68. As a result, the node N5 which is the gate terminal of the switching element 20 is fixed to the potential of the ground line L1, and the switching element 20 is turned off.

[0078] Furthermore, at time T4, when the main switch 4 is turned on (see waveform W3), the supply of the output voltage VBAT of the battery 3 to the DC / DC converter 13 begins, and the main relay 5 is turned on to connect the power supply line L3 and the battery 3.

[0079] This causes the DC / DC converter 13 to start operating, and the control voltage VH rises (see waveform W1). Also, the power supply voltage VP of the power supply line L3 rises and is clamped at the output voltage VBAT of the battery 3 (see waveform W2). As a result, the differential voltages ΔV1 and ΔV2 rise (see waveforms W4 and W5).

[0080] Next, at time T5, when the differential voltage ΔV1 becomes higher than the threshold voltage Vth1, the Zener diode 57 turns on, the voltage at the node N11 drops, the base current flows, and the switch 52 changes from the off state to the on state (see waveform W6). This causes the voltage at the node N13 to rise, and as a result, the base current flows and the switch 61 changes from the off state to the on state (see waveform W8).

[0081] As a result, the voltage at node N14 drops, and the shutoff switch 51 changes from an off state to an on state (see waveform W9). When the shutoff switch 51 changes to an on state, the supply of the control voltage VH to the gate driver 40 begins, the node N5 which is the gate terminal of the switching element 20 can be supplied with the control voltage VH, and the switching element 20 enters a normal operable state (a state in which the switching element 20 is not in a desaturated operation state).

[0082] At time T6, when the differential voltage ΔV2 becomes higher than the threshold voltage Vth2, the Zener diode 66 turns on, the voltage of the node N17 drops, the base current flows, and the switch 63 turns from the off state to the on state (see waveform W7).

[0083] As described above, the battery charging device 1 according to this embodiment includes the switching element 20, the gate driver 40 (control signal generating unit), and the protection processing unit 50. The switching element 20 rectifies the AC voltage generated by the generator 2 by controlling the conductive state, and supplies the charging voltage to the battery 3. The gate driver 40 generates a control signal for the switching element 20 by a control voltage VH obtained by boosting the power supply voltage VBAT output from the battery 3. The protection processing unit 50 stops the supply of the control voltage VH to the gate driver 40 and turns off the switching element 20 when a differential voltage (differential voltage ΔV2) indicating the control voltage VH based on the voltage VP of the power supply line L3 connected to the terminal of the switching element 20 on the battery 3 side, which is a power supply line L3 connected to the battery 3, becomes equal to or lower than a predetermined threshold voltage (equal to or lower than a threshold voltage Vth2).

[0084] As a result, the battery charging device 1 according to this embodiment can prevent the switching element 20 from being turned on in a non-saturated region that is a region outside the saturated region, and can reduce heat generation of the switching element 20. Therefore, the battery charging device 1 according to this embodiment can protect the switching element 20 when the supply of the power source voltage VBAT is stopped while the generator 2 is generating power.

[0085] In addition, in the switching element 20 in the unsaturated region, the on-resistance increases due to a low gate voltage, causing the switching element 20 to generate abnormal heat and resulting in a breakdown. The battery charging device 1 according to this embodiment can prevent such breakdowns caused by abnormal heat generation of the switching element 20.

[0086] Moreover, in this embodiment, the protection processing unit 50 includes a cutoff switch 51 connected between a signal line L4 to which the control voltage VH is supplied and the gate driver 40. The protection processing unit 50 cuts off the conduction of the cutoff switch 51 when the differential voltage (differential voltage ΔV2) becomes equal to or lower than a predetermined threshold voltage (equal to or lower than a threshold voltage Vth2).

[0087] As a result, the battery charger 1 according to the present embodiment can easily and quickly stop the supply of the control voltage VH to the gate driver 40 by controlling the cutoff switch 51, and can turn the switching element 20 into the OFF state.

[0088] In this embodiment, the above-mentioned predetermined threshold voltage includes a threshold voltage Vth1 (first threshold voltage) and a threshold voltage Vth2 (second threshold voltage) lower than the threshold voltage Vth1. The protection processing unit 50 cuts off the conduction of the cutoff switch 51 when the differential voltage ΔV2 becomes equal to or lower than the threshold voltage Vth2, and makes the cutoff switch 51 conductive (on state) when the differential voltage ΔV1 becomes higher than the threshold voltage Vth1.

[0089] As a result, the battery charging device 1 according to this embodiment can impart hysteresis to the control of the cut-off switch 51 to the off state and the control of the cut-off switch 51 to the on state, thereby reducing malfunctions due to noise, for example, near a predetermined threshold voltage.

[0090] In this embodiment, the protection processing unit 50 cuts off the conduction of the cutoff switch 51 when the differential voltage ΔV1 on the supply side of the control voltage VH of the cutoff switch 51 becomes equal to or lower than the threshold voltage Vth1 (first threshold voltage) and when the differential voltage ΔV2 on the gate driver 40 side (control signal generating unit side) of the cutoff switch 51 becomes equal to or lower than the threshold voltage Vth2 (second threshold voltage). The protection processing unit 50 also makes the cutoff switch 51 conductive when the differential voltage ΔV1 on the supply side of the control voltage VH of the cutoff switch 51 becomes higher than the threshold voltage Vth1 or when the differential voltage ΔV2 on the gate driver 40 side of the cutoff switch 51 becomes higher than the threshold voltage Vth2 (second threshold voltage).

[0091] As a result, the battery charging device 1 of this embodiment cuts off the conduction of the cut-off switch 51 using the differential voltage (differential voltage ΔV1 and differential voltage ΔV2) across the cut-off switch 51, and turns on the cut-off switch 51 using the differential voltage ΔV1 on the supply side of the control voltage VH of the cut-off switch 51 or the differential voltage ΔV2 on the gate driver 40 side of the cut-off switch 51, so that the cut-off switch 51 can be reliably controlled with a simple configuration.

[0092] Furthermore, in this embodiment, the protection processing unit 50 detects, by using the Zener diodes (57, 66), that the differential voltages (the differential voltages ΔV1 and ΔV2) have become equal to or lower than predetermined threshold voltages (the threshold voltages Vth1 and Vth2).

[0093] Thus, the battery charging device 1 according to the present embodiment can simplify the configuration for detecting that the differential voltage has become equal to or lower than a predetermined threshold voltage by utilizing the Zener diodes (57, 66).

[0094] Moreover, the protection device 10 according to the present embodiment is a protection device that protects the switching element 20, which rectifies the AC voltage generated by the generator 2 and supplies it to a high-potential power line (for example, power line L3) by controlling the conductive state, and includes a protection processing unit 50. When a differential voltage indicating a control voltage obtained by boosting the power supply voltage VBAT based on the voltage of the high-potential power line (for example, power line L3) connected to the switching element 20 becomes equal to or lower than a predetermined threshold voltage, the protection processing unit 50 stops supplying the control voltage to a gate driver 40 that generates a control signal for the switching element 20 using the control voltage, thereby putting the switching element 20 into a non-conductive state.

[0095] As a result, the protection device 10 according to the present embodiment has the same effect as the battery charging device 1 described above, and can protect the switching element 20 when the supply of the power supply voltage VBAT is stopped while the generator 2 is generating electricity.

[0096] Moreover, the protection method according to the present embodiment is a protection method for a battery charging device 1 including a switching element 20 that rectifies an AC voltage generated by a generator 2 by controlling a conduction state to supply a charging voltage to the battery 3, and a gate driver 40 that generates a control signal for the switching element 20 by a control voltage VH obtained by boosting a power supply voltage VBAT output from the battery 3, and includes a protection processing step. In the protection processing step, when a differential voltage indicating the control voltage VH based on the voltage of a power supply line L3 that is a power supply line connected to the battery 3 via a main switch unit 6 (main relay 5) and is connected to a terminal on the battery 3 side of the switching element 20 becomes equal to or lower than a predetermined threshold voltage, a protection processing unit 50 stops supplying the control voltage VH to the gate driver 40 to turn off the switching element 20.

[0097] As a result, the protection method according to the present embodiment has the same effect as the battery charging device 1 described above, and can protect the switching element 20 when the supply of the power supply voltage VBAT is stopped while the generator 2 is generating electricity.

[0098] The present invention is not limited to the above-described embodiment, and can be modified without departing from the spirit of the present invention. For example, in the above embodiment, an example has been described in which two types of differential voltages, the differential voltage ΔV1 and the differential voltage ΔV2, are used for control, but this is not limited to this, and either one of them may be used.

[0099] In the above embodiment, the protection processing unit 50 uses the cutoff switch 51 to stop the supply of the control voltage VH to the gate driver 40 to turn off the switching element 20, but the present invention is not limited to this. The protection processing unit 50 may use, for example, another logic circuit to control the gate voltage of the switching element 20 to turn off the switching element 20.

[0100] In the above embodiment, the generator 2 is an ACG starter in which the starter motor and the ACG (alternating current generator) are integrated and directly connected to the crank, but the present invention is not limited to this. The generator 2 may be a standalone generator such as a single-phase magneto type AC generator, or may be a generator of another type.

[0101] In the above embodiment, the battery charging device 1 and the protection device 10 are described as being used for vehicle applications such as motorcycles, but the present invention is not limited to this and may be applied to other applications.

[0102] In the above embodiment, the protection processing unit 50 detects that the differential voltage (differential voltage ΔV1 and differential voltage ΔV2) is equal to or lower than the predetermined threshold voltage (threshold voltage Vth1 and threshold voltage Vth2) by using the Zener diodes (57, 66), but the present invention is not limited to this. The protection processing unit 50 may detect that the differential voltage is equal to or lower than the predetermined threshold voltage by using other means such as a comparator or an ADC.

[0103] In addition, in the above embodiment, an example has been described in which the protection processing unit 50 is realized by a circuit configuration such as that shown in FIG. 2, but this is not limited to this, and the protection processing unit 50 may be realized, for example, by software processing that causes a computer to execute processing such as that shown in FIG. 3.

[0104] In addition, in the above embodiment, an example has been described in which the high-potential side power supply line L3 connected to the switching element 20 is connected to the battery 3 via the main relay 5 of the main switch unit 6, but this is not limited to this, and the power supply line L3 may be directly connected to the battery without including the main relay 5.

[0105] In addition, in the above embodiment, an example has been described in which the protection device 10 is applied to a battery charging device 1 (for charging the battery 3), but this is not limited to this, and the protection device 10 may be applied to, for example, a purpose that does not include a battery.

[0106] The battery charging device 1 described above has a computer system inside. The processing steps of the protection processing unit 50 described above are stored in a computer-readable recording medium in the form of a program, and the computer reads and executes this program to perform the above processing. The computer-readable recording medium here refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, etc. Also, the computer program may be distributed to a computer via a communication line, and the computer that receives the program may execute the program. [Explanation of symbols]

[0107] 1 Battery charging device 2. Generator 3 Battery 4 Main switch 5 Main Relay 6 Main switch section 10 Protective devices 11, 58, 62, 67 Diodes 12, 15, 16, 17 Capacitors 13 DC / DC converter 14 Regulator 20, 21, 22, 23, 30, 31, 32, 33 Switching elements 40 Gate Driver 41 Control Switch 18, 42, 43, 44, 53, 54, 55, 56, 59, 60, 64, 65, 68 Resistance 50 Protection Processing Unit 51 Cut-off switch 52, 61, 63 Switches 57, 66 Zener diode

Claims

1. a switching element that, by controlling a conductive state, rectifies the AC voltage generated by the generator and supplies a charging voltage to the battery; a control signal generating unit that generates a control signal for the switching element based on a control voltage obtained by boosting a power supply voltage output from the battery; a protection processing unit that stops supplying the control voltage to the control signal generating unit and brings the switching element into a non-conducting state when a differential voltage indicating the control voltage based on a voltage of a power supply line connected to a terminal of the switching element on the battery side, the differential voltage being a power supply line connected to the battery, becomes equal to or lower than a predetermined threshold voltage; A battery charging device comprising:

2. The protection processing unit includes: a cutoff switch connected between a signal line to which the control voltage is supplied and the control signal generating unit, When the differential voltage becomes equal to or lower than the predetermined threshold voltage, the cutoff switch is turned off.

2. The battery charging device according to claim 1 .

3. the predetermined threshold voltages include a first threshold voltage and a second threshold voltage lower than the first threshold voltage; The protection processing unit includes: When the differential voltage becomes equal to or lower than the second threshold voltage, the cutoff switch is turned off, and when the differential voltage becomes higher than the first threshold voltage, the cutoff switch is turned on.

3. The battery charging device according to claim 2.

4. The protection processing unit includes: When the differential voltage on the supply side of the control voltage of the cutoff switch becomes equal to or lower than the first threshold voltage and when the differential voltage on the control signal generating unit side of the cutoff switch becomes equal to or lower than the second threshold voltage, the conduction of the cutoff switch is interrupted; When the differential voltage on the supply side of the control voltage of the cutoff switch becomes higher than the first threshold voltage, or when the differential voltage on the control signal generating unit side of the cutoff switch becomes higher than the second threshold voltage, the cutoff switch is made conductive.

4. The battery charging device according to claim 3.

5. The protection processing unit includes: A Zener diode is used to detect when the differential voltage falls below the predetermined threshold voltage.

5. The battery charging device according to claim 1, wherein the charging voltage is set to 0.5 V.

6. A protection device that protects a switching element that rectifies an AC voltage generated by a generator and supplies the AC voltage to a high-potential power line by controlling a conductive state, and a protection processing unit that stops supplying a control voltage to a control signal generating unit that generates a control signal for the switching element based on the control voltage when a differential voltage indicating a control voltage obtained by boosting a power supply voltage with respect to the voltage of the high-potential side power supply line connected to the switching element becomes equal to or lower than a predetermined threshold voltage, thereby bringing the switching element into a non-conducting state. A protection device comprising:

7. A method for protecting a battery charging device including a switching element that rectifies an AC voltage generated by a generator by controlling a conductive state to supply a charging voltage to a battery, and a control signal generating unit that generates a control signal for the switching element using a control voltage that is a boosted power supply voltage output from the battery, comprising: The protection processing unit includes a protection processing step of stopping the supply of the control voltage to the control signal generating unit and putting the switching element into a non-conducting state when a differential voltage indicating the control voltage based on a voltage of a power supply line connected to the battery and connected to a terminal of the switching element on the battery side becomes equal to or lower than a predetermined threshold voltage. A protection method comprising:

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