Battery charging device, control device, and protection method

Abstract

This battery charging device comprises: a switching element of which conduction state is controlled to rectify an AC voltage generated by an electric generator, and supply a charging voltage to a battery; a control signal generation unit that outputs a control signal for the switching element, using a control voltage obtained by boosting a power supply voltage output from the battery; and a control unit that controls the control signal to bring the switching element into a non-conducting state when a differential voltage is equal to or less than a predetermined threshold voltage, the differential voltage indicating the control voltage with respect to a voltage of a power supply line that is connected to the battery, and is connected to a terminal on the battery side of the switching element.

Description

Technical Field

[0001] The present invention relates to a battery charging device, a control device, and a protection method. This application claims priority based on Japanese Patent Application No. 2022-198502 filed in Japan on December 13, 2022, and incorporates its content herein by reference.

Background Art

[0002] When performing switching at a voltage higher than the power supply voltage, the power supply voltage is boosted and used for a control signal for switching a switching element such as a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) (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 of a battery is controlled using a control power supply boosted from a power supply voltage output from the battery.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, for example, in a battery charging device mounted on a two-wheeled vehicle or the like, during power generation by the generator, the main switch may be turned off and the power supply voltage of the battery may be interrupted. Thus, when the supply of the power supply voltage stops during power generation, in a conventional battery charging device, the control voltage decreases, and a switching element such as a MOSFET is switched in an unsaturated region, which is a region outside the saturation region. In this case, due to the decrease in the control voltage, the resistance of the switching element increases, so that the switching element generates heat, and there is a possibility that the switching element deteriorates or malfunctions.

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

[0006] To solve the above problem, one aspect of the present invention includes: a switching element that rectifies the AC voltage generated by a generator and supplies a charging voltage to a battery by controlling its conduction state; a control signal generation unit that outputs a control signal for the switching element using a control voltage obtained by boosting the power supply voltage output from the battery; a control unit that controls the control signal to put the switching element into a non-conducting state when the differential voltage, which is the voltage of a power line connected to the battery and connected to the battery-side terminal of the switching element, falls below a predetermined threshold voltage; a memory for storing a program; a CPU (Central Processing Unit) that executes the program stored in the memory; and an analog-to-digital converter that detects the voltage of the power line and the control voltage. The control unit is realized by causing the CPU to execute the program stored in the memory, and includes the processes of detecting the voltage of the power line and the control voltage using the analog-to-digital converter, calculating the differential voltage based on the voltage of the power line and the control voltage, and when the differential voltage falls below a predetermined threshold voltage, The control signal generation unit is output a signal to connect the signal line of the control signal of the switching element to the ground line. The battery charging device is characterized by causing the CPU to perform a process of controlling the control signal so that the switching element is in a non-conductive state.

[0009] Furthermore, in one aspect of the present invention, in the above-described battery charging device, the predetermined threshold voltage includes a first threshold voltage and a second threshold voltage higher than the first threshold voltage, and the control unit controls the control signal to put the switching element into a non-conducting state when the differential voltage becomes less than or equal to the first threshold voltage, and controls the conduction state of the switching element to rectify the AC voltage when the differential voltage becomes higher than the second threshold voltage.

[0010] Furthermore, one aspect of the present invention is a control device for a battery charging device comprising: a switching element that rectifies an AC voltage generated by a generator and supplies a charging voltage to a battery by controlling its conduction state; a control signal generation unit that outputs a control signal for the switching element using a control voltage obtained by boosting the power supply voltage output from the battery, wherein the control device controls the control signal to put the switching element into a non-conducting state when the differential voltage, which indicates the control voltage based on the voltage of a power line connected to the battery terminal of the switching element and is connected to the power line connected to the battery, falls below a predetermined threshold voltage; a memory for storing a program; a CPU (Central Processing Unit) for executing the program stored in the memory; and an analog-to-digital converter for detecting the voltage of the power line and the control voltage, wherein the control device is implemented by causing the CPU to execute the program stored in the memory, and includes the processes of detecting the voltage of the power line and the control voltage using the analog-to-digital converter, calculating the differential voltage based on the voltage of the power line and the control voltage, and when the differential voltage falls below a predetermined threshold voltage, The control signal generation unit is output a signal to connect the signal line of the control signal of the switching element to the ground line. The control device is characterized by causing the CPU to perform a process of controlling the control signal so that the switching element is in a non-conductive state.

[0011] Furthermore, one aspect of the present invention is a protection method for a battery charging device comprising: a switching element that rectifies an AC voltage generated by a generator and supplies a charging voltage to a battery by controlling its conduction state; and a control signal generation unit that outputs a control signal for the switching element using a control voltage obtained by boosting the power supply voltage output from the battery, wherein the control unit includes a control step of controlling the control signal to put the switching element into a non-conducting state when the differential voltage indicating the control voltage, based on the voltage of a power line connected to the battery and connected to the battery-side terminal of the switching element, falls below a predetermined threshold voltage, and the battery charging device comprises a memory for storing a program and a CPU (Central Processing Unit) for executing the program stored in the memory. The control unit comprises an analog-to-digital converter that detects the voltage of the power line and the control voltage, and the control unit is realized by causing the CPU to execute the program stored in the memory, and in the control step, the control unit performs the following: a process of detecting the voltage of the power line and the control voltage using the analog-to-digital converter, a process of calculating the difference voltage based on the voltage of the power line and the control voltage, and when the difference voltage falls below a predetermined threshold voltage, The control signal generation unit is output a signal to connect the signal line of the control signal of the switching element to the ground line. The protection method is characterized by causing the CPU to execute a process that controls the control signal so that the switching element is in a non-conductive state. [Effects of the Invention]

[0012] According to the present invention, the control unit controls a control signal to put the switching element into a non-conducting state when the differential voltage, which is a control voltage based on the voltage of the power line connected to the battery-side terminal of the switching element, falls below a predetermined threshold voltage. As a result, the battery charging device can suppress the switching element from becoming conductive in the unsaturated region, which is a region outside the saturation region, and can reduce the heat generated by the switching element. Therefore, the battery charging device can protect the switching element when the supply of power voltage is interrupted during power generation. [Brief explanation of the drawing]

[0013] [Figure 1] A block diagram showing an example of a battery charging device according to the first embodiment. [Figure 2] This figure illustrates an example of the configuration of the main parts of a battery charging device according to the first embodiment. [Figure 3] This flowchart shows an example of the operation of a battery charging device according to the first embodiment. [Figure 4] This flowchart shows an example of the operation of a battery charging device according to the second embodiment. [Modes for carrying out the invention]

[0014] Hereinafter, a battery charging device, a control device, and a protection method according to one embodiment of the present invention will be described with reference to the drawings.

[0015] [First Embodiment] Figure 1 is a block diagram showing an example of a battery charging device 1 according to the first embodiment. As shown in Figure 1, the battery charging device 1 comprises a diode 11, capacitors (12, 19), a voltage conversion unit 13, a control signal generation unit 14, resistors (15, 16, 18), a control unit 17, and switching elements (21-23, 31-33).

[0016] The battery charging device 1 is connected to the generator 2 and also to the battery 3 via the main switch unit 6. The battery charging device 1 is mounted on a vehicle such as a motorcycle and rectifies the AC power generated by the generator 2 to charge the battery 3. The main switch unit 6 comprises a main switch 4 and a main relay 5, and controls the supply of voltage (power supply voltage) from the battery 3 to the battery charging device 1.

[0017] 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 the crank. Here, the crankshaft is, for example, a rotor connected to the rotating shaft of an internal combustion engine (engine) of a motorcycle.

[0018] The battery 3 is, for example, a lead-acid battery, and its - (minus) electrode (negative electrode) is connected to the ground terminal (ground wire L1), and its + (plus) electrode (positive electrode) is connected to the power supply wire L2. The + electrode of the battery 3 is connected to the main switch 4 and the main relay 5 via the power supply wire L2. In this embodiment, the output voltage of the battery 3 is defined as the power supply voltage VBAT.

[0019] The main switch 4 is, for example, the main switch of a vehicle such as a motorcycle. Its first end is connected to the + electrode (power supply wire L2) of the battery 3, and its second end is connected to the node N1 that supplies the internal power supply. The main switch 4 can be switched between an on state (connected state) and an off state (non-connected state) manually by the user.

[0020] The main relay 5 (an example of a main switch) is connected between the power supply wire L2 and the power supply wire L3. When the main switch 4 is turned on and the node N1 becomes the power supply voltage VBAT, the main relay 5 is turned on, and the power supply wire L2 and the power supply wire L3 are connected. Also, when the main switch 4 is turned off, the main relay 5 is turned off, and the power supply wire L2 and the power supply wire L3 are disconnected. In this embodiment, the voltage of the power supply wire L3 is defined as the voltage VP.

[0021] Thus, the main switch unit 6 controls the connection between the battery 3 and the power supply wire L3 (switching elements 21 to 23 described later), and the connection between the battery 3 and the node N1 (voltage conversion unit 13 described later).

[0022] The anode terminal of the diode 11 is connected to the node N1, and the cathode terminal is connected to the node N2, respectively. The diode 11 supplies the output voltage (power supply voltage VBAT) of the battery 3 to the voltage conversion unit 13 and prevents the reverse flow of current from the voltage conversion unit 13 to the battery 3.

[0023] The capacitor 12 is connected between the node N1 and the ground line L1 and is a smoothing capacitor that smooths the output voltage (power supply voltage VBAT) of the battery 3 supplied to the voltage conversion unit 13.

[0024] The voltage conversion unit 13 is, for example, a power supply device that generates a high voltage and a low voltage from the output voltage (power supply voltage VBAT) of the battery 3. The voltage conversion unit 13 boosts the power supply voltage VBAT output by the battery 3 and generates a voltage VH higher than the power supply voltage VBAT as a control voltage and outputs it to the signal line L4. Also, the voltage conversion unit 13 generates a voltage lower than the voltage VH from the power supply voltage VBAT output by the battery 3, which is a voltage for the control unit 17, and supplies it to the control unit 17. Note that the power supply voltage VBAT is supplied to the voltage conversion unit 13 via the main switch 4.

[0025] The control signal generation unit 14 is, for example, a gate driver that drives the switching elements 21 to 23 and the switching elements 31 to 33. The control signal generation unit 14 generates a control signal for the switching element 20 based on a control voltage (voltage VH) obtained by boosting the power supply voltage VBAT output from the battery 3. Although not shown for the sake of explanation, control signals are output to the gate terminals of the switching element 22, the switching element 23, and the switching elements 31 to 33, respectively. The control signal generation unit 14 generates a control signal for the switching element 20 based on the control by the control unit 17. Also, when the control signal generation unit 14 outputs a control signal for the switching element 21, the resistors 15 and 16 are connected to the control signal.

[0026] The first end of resistor 15 is connected to the signal line of the control signal of the control signal generation unit 14, and the second end is connected to node N3 (the gate terminal of the switching element 21). The first end of resistor 16 is connected to node N3, and the second end is connected to the signal line of the drive signal U. Resistors 15 and 16 are connected in series between the signal line of the control signal generation unit 14 (the control signal line for the control voltage VH) and the signal line of the drive signal U.

[0027] Although not shown in the diagram, the control signal generation unit 14 also has resistors similar to resistors 15 and 16 connected to the control signals of switching elements 22, 23, and 31 to 33.

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

[0029] Furthermore, since the switching element 20 is an N-type MOSFET, in order to reduce its on-resistance, the voltage of the control signal supplied to the gate terminal must be higher than the source-drain voltage, which is the voltage between the source terminal and the drain terminal. When the gate voltage of the switching element 20 falls below the source-drain voltage, it conducts in the saturation region (unsaturated operation), increasing the on-resistance of the switching element 20 and causing heat generation.

[0030] The switching element 21 has its drain terminal connected to the power line L3 (high-potential power line), its source terminal connected to node N4, and its control terminal (gate terminal) connected to node N3. Node N4 is the signal line for the drive signal U used when driving the generator 2 as a starter motor. Node N3 is the signal line for the control signal output by the control signal generation unit 14, which is driven by the control voltage VH.

[0031] The switching element 22 has its drain terminal connected to the power line L3, its source terminal connected to node N5, and its control terminal (gate terminal) connected to the output line of the control signal of the control signal generation unit 14, which is the same as node N3. Node N5 is the signal line for the drive signal V when the generator 2 is driven as a starter motor. The gate terminal of the switching element 22 is driven by the control voltage VH generated by the control signal output by the control signal generation unit 14.

[0032] The switching element 23 has its drain terminal connected to the power line L3, its source terminal connected to node N6, and its control terminal (gate terminal) connected to the output line of the control signal of the control signal generation unit 14, which is the same as node N3. Node N6 is the signal line for the drive signal W used when driving the generator 2 as a starter motor. The gate terminal of the switching element 23 is driven by the control voltage VH generated by the control signal output by the control signal generation unit 14.

[0033] 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, switching elements 31 to 33 will be described as switching element 30 when referring to any low-side switching elements provided in the battery charging device 1, or when no particular distinction is made.

[0034] The switching element 31 has its drain terminal connected to node N4, its source terminal connected to the ground line L1 (low-potential power line) via resistor 18, and its control terminal (gate terminal) connected to the control signal output line of the control signal generation unit 14. Node N4 is the signal line for the drive signal U used when driving the generator 2 as a starter motor.

[0035] The switching element 32 has its drain terminal connected to node N5, its source terminal connected to the ground line L1 via resistor 18, and its control terminal (gate terminal) connected to the output line of the control signal of the control signal generation unit 14. Node N5 is the signal line for the drive signal V when the generator 2 is driven as a starter motor.

[0036] The switching element 33 has its drain terminal connected to node N6, its source terminal connected to the ground line L1 via resistor 18, and its control terminal (gate terminal) connected to the output line of the control signal of the control signal generation unit 14. Node N6 is the signal line for the drive signal W used when driving the generator 2 as a starter motor.

[0037] Switching elements 20 (21-23) and 30 (31-33) function as an inverter circuit when the generator 2 is driven as a starter motor. Furthermore, switching elements 20 (21-23) and 30 (31-33) function as a rectifier circuit when the generator 2 is used to charge the battery 3, rectifying the AC voltage generated by the generator 2.

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

[0039] The control unit 17 is, for example, a processor including a CPU (Central Processing Unit), and comprehensively controls the battery charging device 1. When the control unit 17 drives the generator 2 as a starter motor, it controls the switching elements 20 (21-23) and switching elements 30 (31-33) as an inverter circuit. In this embodiment, the control unit 17 is included in the control device 10.

[0040] Furthermore, when charging the battery 3 from the generator 2, the control unit 17 controls the switching elements 20 (21-23) and 30 (31-33) as a rectifier circuit. The control unit 17 controls a control signal to turn off the switching element 20 (non-conducting state) when the differential voltage ΔV (= voltage VH - voltage VP), which represents the control voltage VH based on the voltage VP of the power line L3 connected to the battery 3, falls below a predetermined threshold voltage (for example, below the threshold voltage Vth). Now, referring to Figure 2, the configuration of the main parts of the battery charging device 1, including the control unit 17, will be described.

[0041] Figure 2 is a diagram illustrating an example of the configuration of the main parts of the battery charging device 1 according to this embodiment. As shown in Figure 2, the main components of the battery charging device 1 include a control device 10, a control signal generation unit 14, resistors (15, 16), and switching elements (21, 31).

[0042] The control device 10 includes resistors 101 and 102, a capacitor 103, resistors 104 and 105, a capacitor 106, and a control unit 17. Resistors 101 and 102 are connected in series between the power line L3 and the ground line L1 of the voltage VP, and the resistance ratio of resistors 101 and 102 converts the voltage VP into a voltage range detectable by the ADC171, which will be described later.

[0043] Resistor 101 has its first end connected to the power line L3 and its second end connected to node N8. Resistor 102 has its first end connected to node N8 and its second end connected to the ground line L1. Node N8 is connected to the first detection terminal of the ADC171, which will be described later. Capacitor 103 is connected between node N8 and the ground line L1, and flattens the voltage at node N8, which is obtained by resistively dividing the voltage VP.

[0044] Furthermore, resistors 104 and 105 are connected in series between the signal line L4 of the control voltage VH and the ground line, and the resistance ratio of resistors 104 and 105 converts the control voltage VH into a voltage range detectable by the ADC171, which will be described later.

[0045] The first end of resistor 104 is connected to node N9, and the second end is connected to signal line L4. The first end of resistor 105 is connected to node N9, and the second end is connected to ground line L1. Node N9 is connected to the second detection terminal of ADC171, which will be described later. Capacitor 106 is connected between node N9 and ground line L1, and flattens the voltage at node N9 obtained by resistively dividing the voltage VH.

[0046] The control unit 17 includes an ADC 171, a memory 172, and a CPU 173. The ADC171 (an example of an analog-to-digital converter) detects the voltage VP of the power line L3 and the control voltage VH. That is, the ADC171 detects the voltage value of the control voltage VH and the voltage value of the voltage VP. The control unit 17 calculates the difference voltage ΔV based on the voltage VP of the power line L3 and the control voltage VH detected by the ADC171.

[0047] Memory 172 is, for example, RAM (Random Access Memory) or flash memory, and stores programs (for example, control programs). CPU173 executes the program stored in memory172.

[0048] The control unit 17 is implemented by causing the CPU 173 to execute a program stored in the memory 172. When the differential voltage ΔV falls below the threshold voltage Vth, the control unit 17 outputs a signal SG so that the control signal generation unit 14 outputs the voltage of the ground line L1 as a control signal HSG to the switching element 21(20). In this case, the control signal generation unit 14 enters state ST2, where the signal line of the control signal HSG and the ground line L1 are connected.

[0049] Furthermore, when the differential voltage ΔV is greater than the threshold voltage Vth, the control unit 17 outputs a signal SG to the control signal generation unit 14 so that the switching element 21(20) functions as a synchronous rectifier. When the switching element 21(20) is controlled to the ON state, the control signal generation unit 14 enters state ST1, where the signal line of the control signal HSG and the signal line L4 of the control voltage VH are connected.

[0050] Next, the operation of the battery charging device 1 according to this embodiment will be described with reference to the drawings. Figure 3 is a flowchart showing an example of the operation of the battery charging device 1 according to this embodiment. Here, the protection process of the battery charging device 1 by the control unit 17) (control device 10) will be described.

[0051] As shown in Figure 3, the control unit 17 of the battery charging device 1 first detects the voltage VP of the power line L3 and the control voltage VH using the ADC 171 (step S101). The control unit 17 detects the voltage VP by detecting the voltage at node N8, which is divided by resistors 101 and 102, using the ADC 171, and also detects the control voltage VH by detecting the voltage at node N9, which is divided by resistors 104 and 105, using the ADC 171.

[0052] Next, the control unit 17 calculates the differential voltage ΔV (= control voltage VH - voltage VP) (step S102). The control unit 17 calculates the differential voltage ΔV by subtracting the voltage VP detected by the ADC 171 from the control voltage VH detected by the ADC 171.

[0053] Next, the control unit 17 determines whether the differential voltage ΔV is less than or equal to the threshold voltage Vth (differential voltage ΔV ≤ threshold voltage Vth) (step S103). If the differential voltage ΔV is less than or equal to the threshold voltage Vth (step S103: YES), the control unit 17 proceeds to step S104. If the differential voltage ΔV is greater than the threshold voltage Vth (step S103: NO), the control unit 17 proceeds to step S105.

[0054] In step S104, the control unit 17 controls the switching element 20 to the OFF state. The control unit 17 connects the signal line of the control signal HSG to the ground line L1 in the control signal generation unit 14, and controls the gate terminal of the switching element 20 to the potential of the ground line L1, thereby turning off the switching element 20. After the processing in step S104, the control unit 17 returns the process to step S101.

[0055] Furthermore, in step S105, the control unit 17 controls the ON state of the switching element 20 to rectify the AC voltage. The control unit 17 controls the switching element 20 to rectify the AC voltage generated by the generator 2 and generate a charging voltage. After the processing in step S105, the control unit 17 returns the process to step S101.

[0056] As described above, the battery charging device 1 according to this embodiment comprises a switching element 20, a control signal generation unit 14, and a control unit 17. The switching element 20, by being controlled to be in an ON state (conductive state), rectifies the AC voltage generated by the generator 2 and supplies the charging voltage to the battery 3. The control signal generation unit 14 outputs a control signal HSG for the switching element 20, which is a control voltage VH obtained by boosting the power supply voltage VBAT output from the battery 3. The control unit 17 controls the control signal HSG to turn the switching element 20 into a non-conductive state when the differential voltage ΔV, which represents the control voltage VH based on the voltage VP of the power supply line L3 connected to the battery side (battery 3 side) terminal of the switching element 20, falls below a predetermined threshold voltage (below threshold voltage Vth).

[0057] As a result, the battery charging device 1 according to this embodiment can suppress the switching element 20 from turning on in the unsaturated region, which is a region outside the saturation region, and can reduce the heat generated by the switching element 20. Therefore, the battery charging device 1 according to this embodiment can protect the switching element 20 when, for example, the supply of the power supply voltage VBAT is stopped while the generator 2 is generating power. That is, for example, when the battery charging device 1 is mounted on a motorcycle or the like, the battery charging device 1 according to this embodiment can protect the switching element 20 when the main switch 4 is turned off and the power supply voltage of the battery 3 is interrupted while the generator is generating power (while the wheels are rotating).

[0058] In the unsaturated region, the on-resistance of the switching element 20 increases due to the low gate voltage, causing the switching element 20 to overheat abnormally and potentially leading to failure. The battery charging device 1 according to this embodiment can prevent such failures caused by abnormal overheating of the switching element 20.

[0059] Furthermore, the battery charging device 1 according to this embodiment includes a memory 172 for storing programs and a CPU 173 for executing the programs stored in the memory 172. The control unit 17 is realized by causing the CPU 173 to execute the programs stored in the memory 172.

[0060] As a result, the battery charging device 1 according to this embodiment can appropriately protect the switching element 20 through software processing without adding any special hardware, for example, if the supply of the power supply voltage VBAT is interrupted while the generator 2 is generating power.

[0061] Furthermore, the battery charging device 1 according to this embodiment includes an ADC171 (analog-to-digital converter) that detects the voltage VP of the power line L3 and the control voltage VH. The control unit 17 calculates the differential voltage ΔV based on the voltage VP of the power line L3 and the control voltage VH detected by the ADC171 (analog-to-digital converter).

[0062] As a result, the battery charging device 1 according to this embodiment can more accurately detect the voltage VP, the control voltage VH, and the differential voltage ΔV by using the ADC171, and can more effectively protect the switching element 20.

[0063] Furthermore, the control device 10 according to this embodiment is a control device for a battery charging device 1 that includes a switching element 20 that rectifies the AC voltage generated by the generator 2 and supplies a charging voltage to the battery 3 when its ON state is controlled, and a control signal generation unit 14 that outputs a control signal HSG for the switching element 20 using a control voltage VH obtained by boosting the power supply voltage VBAT output from the battery 3, and includes a control unit 17. The control unit 17 controls the control signal HSG to turn off the switching element 20 when the differential voltage ΔV, which represents the control voltage VH based on the voltage VP of the power supply line L3 connected to the battery 3 terminal of the switching element 20, falls below a predetermined threshold voltage (below threshold voltage Vth).

[0064] As a result, the battery charging device 1 according to this embodiment provides the same effects as the battery charging device 1 described above, and can protect the switching element 20 if, for example, the supply of power voltage VBAT is stopped while the generator 2 is generating power.

[0065] Furthermore, the protection method according to this embodiment is a protection method for a battery charging device 1 comprising a switching element 20 that rectifies the AC voltage generated by the generator 2 and supplies a charging voltage to the battery 3 by controlling its ON state, and a control signal generation unit 14 that outputs a control signal HSG for the switching element 20 using a control voltage VH obtained by boosting the power supply voltage VBAT output from the battery 3, and includes a control step. In the control step, the control unit 17 controls the control signal HSG to de-conduct the switching element 20 when the differential voltage ΔV, which represents the control voltage VH based on the voltage VP of the power supply line L3 connected to the battery 3 terminal of the switching element 20, falls below a predetermined threshold voltage (below threshold voltage Vth).

[0066] As a result, the protection method according to this embodiment has the same effect as the battery charging device 1 described above, and can protect the switching element 20 if, for example, the supply of power voltage VBAT is stopped while the generator 2 is generating power.

[0067] [Second Embodiment] Next, with reference to the drawings, a battery charging device 1 according to the second embodiment will be described. In the second embodiment, the basic configuration of the battery charging device 1 is the same as that of the first embodiment shown in Figures 1 and 2 above, so its description will be omitted here. In this embodiment, the processing of the control unit 17 is different, and the changes in the processing of the control unit 17 will be explained here.

[0068] In this embodiment, the predetermined threshold voltage includes a threshold voltage Vth1 (first threshold voltage) and a threshold voltage Vth2 (second threshold voltage) that is higher than the threshold voltage Vth1. In this embodiment, the control unit 17 controls the control signal HSG to turn off the switching element 20 when the differential voltage ΔV becomes less than or equal to the threshold voltage Vth1 (less than or equal to the first threshold voltage). The control unit 17 also controls the ON state of the switching element 20 to rectify the AC voltage when the differential voltage ΔV becomes higher than the threshold voltage Vth2 (second threshold voltage).

[0069] Next, with reference to the drawings, the operation of the battery charging device 1 according to the second embodiment will be described in detail. Figure 4 is a flowchart showing an example of the operation of the battery charging device 1 according to the second embodiment.

[0070] In Figure 4, the processes in steps S201 and S202 are the same as those in steps S101 and S102 shown in Figure 3 above, so their explanation is omitted here.

[0071] In step S203, the control unit 17 determines whether the differential voltage ΔV is less than or equal to the threshold voltage Vth1 (differential voltage ΔV ≤ threshold voltage Vth1). If the differential voltage ΔV is less than or equal to the threshold voltage Vth1 (step S203: YES), the control unit 17 proceeds to step S204. If the differential voltage ΔV is greater than the threshold voltage Vth1 (step S203: NO), the control unit 17 proceeds to step S205.

[0072] In step S204, the control unit 17 controls the switching element 20 to the OFF state. The control unit 17 connects the signal line of the control signal HSG and the ground line L1 to the control signal generation unit 14, and controls the gate terminal of the switching element 20 to the potential of the ground line L1, thereby turning off the switching element 20. After the processing in step S204, the control unit 17 returns the process to step S201.

[0073] Furthermore, in step S205, the control unit 17 determines whether the differential voltage ΔV is greater than the threshold voltage Vth2 (differential voltage ΔV > threshold voltage Vth2). If the differential voltage ΔV is greater than the threshold voltage Vth2 (step S205: YES), the control unit 17 proceeds to step S206. If the differential voltage ΔV is less than or equal to the threshold voltage Vth2 (step S205: NO), the control unit 17 returns to step S201.

[0074] In step S206, the control unit 17 changes the process to control the ON state of the switching element 20 so as to rectify the AC voltage. As a result, the control unit 17 controls the switching element 20 to rectify the AC voltage generated by the generator 2 and generate a charging voltage. After the process in step S206, the control unit 17 returns the process to step S201.

[0075] As described above, in this embodiment, the predetermined threshold voltage includes a threshold voltage Vth1 (first threshold voltage) and a threshold voltage Vth2 (second threshold voltage) that is higher than the threshold voltage Vth1. The control unit 17 controls the control signal HSG to turn off the switching element 20 when the differential voltage ΔV becomes less than or equal to the threshold voltage Vth1 (less than or equal to the first threshold voltage). The control unit 17 also controls the state of the switching element 20 to rectify the AC voltage when the differential voltage ΔV becomes higher than the threshold voltage Vth2 (second threshold voltage).

[0076] As a result, the battery charging device 1 according to this embodiment can have hysteresis between the control of the switching element 20 to the off state and the control of it to the on state to rectify the AC voltage, thereby reducing malfunctions caused by noise near a predetermined threshold voltage, for example.

[0077] It should be noted that the present invention is not limited to the embodiments described above, and can be modified without departing from the spirit of the invention. For example, in each of the embodiments described above, the generator 2 is described as an ACG starter that integrates a starter motor and an ACG (alternating current generator) and is directly connected to a crank, but it is not limited to this. The generator 2 may be a single generator, such as a single-phase magnet type AC generator, or a generator of other types.

[0078] Furthermore, although the above embodiments describe examples of the battery charging device 1 and control device 10 being used in vehicle applications such as motorcycles, they are not limited to this and may be applied to other applications.

[0079] Furthermore, in each of the above embodiments, the control unit 17 was shown to use the ADC 171 to detect the voltage VP and the control voltage VH, and to calculate the differential voltage ΔV by calculation by the CPU 173, but the control unit 17 is not limited to this. The control unit 17 may, for example, use a comparator instead of the ADC 171 to detect the voltage VP and the control voltage VH, and to determine that the differential voltage ΔV is below a predetermined threshold voltage.

[0080] Furthermore, in each of the above embodiments, an example was described in which the high-potential power 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. However, the invention is not limited to this, and the power line L3 may be directly connected to the battery 3 without the main relay 5.

[0081] Furthermore, although examples in the above embodiments have been described in which the voltage conversion unit 13 and the control signal generation unit 14 have different configurations, the invention is not limited to these configurations. For example, the control signal generation unit 14 may include part or all of the voltage conversion unit 13.

[0082] Furthermore, although the above embodiment describes an example in which the control device 10 is applied to a battery charging device 1 (for charging the battery 3), it is not limited to this, and may be applied to applications that do not include a battery, for example.

[0083] The battery charging device 1 described above has a computer system inside. The processing steps of the control unit 17 described above are stored in program form on a computer-readable recording medium, and the above processing is performed when the computer reads and executes this program. Here, a computer-readable recording medium refers to a magnetic disk, magneto-optical disk, CD-ROM, DVD-ROM, semiconductor memory, etc. Alternatively, this computer program may be distributed to a computer via a communication line, and the computer that receives the distribution may execute the program. [Industrial applicability]

[0084] This invention can be applied to battery charging and other applications. [Explanation of symbols]

[0085] 1. Battery charging device 2 generators 3 Batteries 4 Main Switch 5 Main Relay 6. Main switch section 10 Control device 11 diodes 12, 19, 103, 106 Capacitors 13 Voltage conversion section 14 Control signal generation unit 15, 16, 18, 101, 102, 104, 105 resistors 17 Control Unit 20, 21, 22, 23, 30, 31, 32, 33 Switching elements 171 ADC 172 memory 173 CPU

Claims

1. A switching element controls the conduction state to rectify the AC voltage generated by the generator and supply the charging voltage to the battery. A control signal generation unit that outputs a control signal for the switching element using a control voltage obtained by boosting the power supply voltage output from the battery, A control unit controls the control signal to de-conduct the switching element when the differential voltage, which represents the control voltage based on the voltage of the power line connected to the battery-side terminal of the switching element, falls below a predetermined threshold voltage. Memory for storing programs, A CPU (Central Processing Unit) that executes the program stored in the memory, An analog-to-digital converter that detects the voltage of the power line and the control voltage. Equipped with, The control unit, This is achieved by having the CPU execute the program stored in the memory, The analog-to-digital converter performs a process to detect the voltage of the power line and the control voltage, A process for calculating the difference voltage based on the voltage of the power line and the control voltage, When the differential voltage falls below a predetermined threshold voltage, a signal is output to the control signal generation unit to connect the signal line of the switching element's control signal to the ground line, thereby controlling the control signal to put the switching element into a non-conducting state. A battery charging device characterized by causing the CPU to execute the above.

2. The predetermined threshold voltage includes a first threshold voltage and a second threshold voltage that is higher than the first threshold voltage. The control unit, When the differential voltage falls below the first threshold voltage, the control signal is controlled to de-conduct the switching element. When the differential voltage becomes higher than the second threshold voltage, the conduction state of the switching element is controlled to rectify the AC voltage. The battery charging device according to feature 1.

3. A control device for a battery charging device comprising: a switching element that rectifies the AC voltage generated by a generator and supplies a charging voltage to a battery by controlling its conduction state; and a control signal generation unit that outputs a control signal for the switching element using a control voltage obtained by boosting the power supply voltage output from the battery, A control unit controls the control signal to de-conduct the switching element when the differential voltage, which represents the control voltage based on the voltage of the power line connected to the battery-side terminal of the switching element, falls below a predetermined threshold voltage. Memory for storing programs, A CPU (Central Processing Unit) that executes the program stored in the memory, An analog-to-digital converter that detects the voltage of the power line and the control voltage. Equipped with, The control unit, This is achieved by having the CPU execute the program stored in the memory, The analog-to-digital converter performs a process to detect the voltage of the power line and the control voltage, A process for calculating the difference voltage based on the voltage of the power line and the control voltage, When the differential voltage falls below a predetermined threshold voltage, a signal is output to the control signal generation unit to connect the signal line of the switching element's control signal to the ground line, thereby controlling the control signal to put the switching element into a non-conducting state. A control device characterized by causing the CPU to execute the above.

4. A battery charging device protection method comprising: a switching element that rectifies the AC voltage generated by a generator and supplies a charging voltage to a battery by controlling its conduction state; and a control signal generation unit that outputs a control signal for the switching element using a control voltage obtained by boosting the power supply voltage output from the battery, The control unit includes a control step in which it controls the control signal to put the switching element into a non-conducting state when the differential voltage, which represents the control voltage based on the voltage of the power line connected to the battery and connected to the battery-side terminal of the switching element, falls below a predetermined threshold voltage. The aforementioned battery charging device Memory for storing programs, A CPU (Central Processing Unit) that executes the program stored in the memory, An analog-to-digital converter that detects the voltage of the power line and the control voltage. It is equipped with, The control unit is realized by causing the CPU to execute the program stored in the memory. In the control step, the control unit, The analog-to-digital converter performs a process to detect the voltage of the power line and the control voltage, A process for calculating the difference voltage based on the voltage of the power line and the control voltage, When the differential voltage falls below a predetermined threshold voltage, a signal is output to the control signal generation unit to connect the signal line of the switching element's control signal to the ground line, thereby controlling the control signal to put the switching element into a non-conducting state. A protection method characterized by causing the CPU to execute the above.

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