Battery charging device, control device, and control method

Abstract

This battery charging device comprises: a bridge rectifier circuit that outputs, as battery charging power, DC power obtained by rectifying AC power, such output performed by controlling the on / off of a switching element connected between the battery and an output signal line of a generator that outputs the AC power; a temperature detection unit that detects the temperature of the switching element; and a control unit that controls the charging current of the battery by controlling the phase of the switching element, on the basis of the temperature detected by the temperature detection unit.

Description

Battery charging device, control device, and control method

[0001] The present disclosure relates to a battery charging device, a control device, and a control method.

[0002] Some vehicles are equipped with battery charging devices that rectify AC power output from a generator using a bridge rectifier circuit that uses switching elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) to charge the battery. The switching elements used for rectification within the battery charging device unit are the components that generate the most heat. However, they have a set upper limit for their operating temperature, and they must be designed to ensure that this limit is not exceeded. This requires temperature testing of the unit for each vehicle, which places a heavy burden on the vehicle manufacturer's manufacturing process. Furthermore, if the results of the temperature testing indicate that the temperature exceeds the upper limit, design changes may be required, which could require not only reselection of MOSFETs but also changes to the unit's external dimensions, potentially resulting in significant design setbacks.

[0003] Meanwhile, a technology has been disclosed for a voltage regulator equipped with a thermal protection circuit that turns off the output when an overheating state is detected to prevent breakdown due to an excessive temperature rise (see, for example, Patent Document 1). If such a thermal protection circuit is provided, it may become unnecessary to perform a temperature measurement test on the unit for each vehicle to prevent the temperature from exceeding an upper limit value.

[0004] JP 2017-107296 A

[0005] However, the technology described in Patent Document 1 has the problem that, since the output is turned off when an overheating state is detected, even if destruction can be prevented, the output is temporarily stopped.

[0006] The present invention has been made in consideration of the above-mentioned circumstances, and one of its objects is to provide a battery charging device, a control device, and a control method that prevent damage due to temperature rise without stopping the output of charging current.

[0007] In order to solve the above problem, one aspect of the present invention is a battery charging device comprising: a bridge rectifier circuit that controls the on / off of a switching element connected between an output signal line of a generator that outputs AC power and a battery, thereby rectifying the AC power and outputting DC power as charging power for the battery; a temperature detection unit that detects the temperature of the switching element; and a control unit that controls the phase of the switching element based on the temperature detected by the temperature detection unit, thereby controlling the charging current for the battery.

[0008] In addition, one aspect of the present invention is that in the above-mentioned battery charging device, when the temperature detected by the temperature detection unit reaches a first threshold value, the control unit performs advance angle control to advance the phase of the switching element relative to the phase of the AC current output from the generator.

[0009] In addition, one aspect of the present invention is that in the above-mentioned battery charging device, when the temperature detected by the temperature detection unit reaches a second threshold value higher than the first threshold value, the control unit performs advance control to advance the phase of the switching element further relative to the phase of the AC current output from the generator than when the temperature detected by the temperature detection unit reaches the first threshold value.

[0010] In another aspect of the present invention, in the battery charging device, the bridge rectifier circuit includes a plurality of the switching elements, and a plurality of the temperature detection units are provided corresponding to the plurality of switching elements to detect the temperatures of each of the switching elements, and the control unit performs advance angle control to advance the phase of the switching element corresponding to one of the plurality of temperature detection units whose detected temperature has reached the first threshold value relative to the phase of the AC current output from the generator, and performs delay angle control to delay the phase of the switching element corresponding to at least one of the plurality of temperature detection units whose detected temperature has not reached the first threshold value relative to the phase of the AC current output from the generator.

[0011] In one aspect of the present invention, in the battery charging device, the switching element is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

[0012] Another aspect of the present invention is a control device that controls a battery charging device having a bridge rectifier circuit that rectifies AC power and outputs DC power as charging power for the battery by controlling the on / off of a switching element connected between an output signal line of a generator that outputs AC power and a battery, and a temperature detection unit for detecting the temperature of the switching element, wherein the control device monitors the temperature detected by the temperature detection unit and controls the phase of the switching element based on the temperature detected by the temperature detection unit to control the charging current of the battery.

[0013] Another aspect of the present invention is a control method for a battery charging device including a bridge rectifier circuit that controls the on / off of a switching element connected between an output signal line of a generator that outputs AC power and a battery, thereby rectifying the AC power and outputting DC power as charging power for the battery, and a temperature detection unit for detecting the temperature of the switching element, the control method including the steps of: a control unit monitoring the temperature detected by the temperature detection unit; and a control unit controlling the phase of the switching element based on the temperature detected by the temperature detection unit, thereby controlling the charging current of the battery.

[0014] According to the present invention, the temperature of the switching element that generates the most heat in the battery charger is detected, and the charging current of the battery is controlled by controlling the phase of the switching element based on the detected temperature. This allows the battery charger to prevent damage due to temperature rise without stopping the output of the charging current. In addition, because the battery charger is equipped with a protection circuit that controls the charging current based on the temperature of the switching element, it may be possible to eliminate the need to perform unit temperature measurement tests for each vehicle.

[0015] A block diagram showing an example of a battery charging device according to a first embodiment. An explanatory diagram of phase control of a switching element according to the first embodiment. A timing chart showing an example of phase control according to the first embodiment. An image diagram of variation in element temperature according to a second embodiment. A timing chart showing an example of phase control according to the second embodiment.

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0017] [First Embodiment] Fig. 1 is a block diagram showing an example of a battery charging device 1 according to this embodiment. The battery charging device 1 is a charging device for charging a battery mounted on a vehicle or the like. The battery charging device 1 shown in Fig. 1 is connected to a generator 2 and rectifies AC power generated by the generator 2 to charge a battery 3. The generator 2 is, for example, a three-phase AC generator that outputs AC power. The battery 3 is, for example, a lead-acid battery, and a negative electrode (negative electrode) is connected to a ground line L1 and a positive electrode (positive electrode) is connected to a power supply line L2.

[0018] The battery charging device 1 includes a capacitor 11, a bridge rectifier circuit 12, a control unit 13, and a power supply unit 14. The capacitor 11 is connected between the ground line L1 and the power supply line L2, and is a smoothing capacitor that smoothes the output voltage and charging voltage of the battery 3.

[0019] The bridge rectifier circuit 12 includes switching elements Q (Q1 to Q6), thermistors T (T1 to T6), and resistors R (R1 to R6). The switching elements Q (Q1 to Q6) are, for example, N-channel metal oxide semiconductor field effect transistors (MOSFETs). The switching elements Q (Q1 to Q6) are connected between the output signal line of the generator 2 and the battery 3, and are configured as a three-phase bridge rectifier circuit.

[0020] The bridge rectifier circuit 12 outputs DC power, which is obtained by rectifying AC power output from the generator 2, as charging power for the battery 3, via the ground line L1 and the power line L2, by controlling the on / off of the switching elements Q (Q1 to Q6) by the control unit 13.

[0021] The control unit 13 includes a CPU (Central Processing Unit), a memory, etc., and the bridge rectifier circuit 12 controls the on / off of the switching elements Q (Q1 to Q6). For example, the control unit 13 generates and outputs a control signal to the gate terminal of each of the switching elements Q1 to Q6 to control the on / off timing (energization timing).

[0022] The power supply unit 14 generates a voltage (control power supply voltage) for the control unit 13 from the voltage between the ground line L1 and the power line L2 (the output voltage and charging voltage of the battery 3), and supplies it to the control unit 13 via the ground line L1 and the power line L3.

[0023] When the switching elements Q (Q1 to Q6) are controlled to turn on and off, the on-resistance of the switching elements Q (Q1 to Q6) and the current flowing through them consume power and generate heat. The greater the output current of the bridge rectifier circuit 12 (the charging current to the battery 3), the greater the amount of heat generated. The switching elements Q (Q1 to Q6) are the components that generate the most heat within the battery charging device 1, and because an upper limit for their operating temperature has been set, it is necessary to ensure that they do not exceed this upper limit.

[0024] Therefore, the control unit 13 monitors the temperatures of the switching elements Q (Q1 to Q6) and controls the output current (charging current to the battery 3) so that the temperature does not exceed an upper limit. For example, the thermistors T (T1 to T6) shown in Fig. 1 are provided near each of the switching elements Q (Q1 to Q6) as temperature sensors for detecting the temperature of each of the switching elements Q (Q1 to Q6).

[0025] The thermistor T1 is provided near the switching element Q1 to detect the temperature of the switching element Q1. The thermistor T1 and resistor R1 are connected in series between the ground line L1 and the power supply line L3. The control unit 13 monitors the temperature of the switching element Q1 by detecting the voltage divided by the thermistor T1 and resistor R1.

[0026] Similarly, thermistors T2 to T6 are provided near the switching elements Q2 to Q6, respectively, to detect the temperatures of the switching elements Q2 to Q6. Thermistors T2 to T6 and resistors R2 to R6 are connected in series between the ground line L1 and the power supply line L3. The control unit 13 detects and monitors the temperatures of the switching elements Q2 to Q6 by detecting the voltages divided by thermistors T2 to T6 and resistors R2 to R6, respectively.

[0027] The control unit 13 controls the output current (charging current for the battery 3) by controlling the phase of the on / off timing (current application timing) of the switching elements Q (Q1 to Q6) based on the temperature detected using the thermistors T (T1 to T6).

[0028] 2 is an explanatory diagram of the phase control of the switching elements according to this embodiment. This diagram illustrates the cases where the phase of the energization timing of the switching elements Q (Q1 to Q6) is advanced and delayed relative to the phase of the AC current (phase current) output from the generator 2.

[0029] The output current can be increased or decreased by controlling the phase angle of the energization timing of the switching elements Q (Q1 to Q6). For example, shifting the phase to the advance side reduces the output current, while shifting the phase to the delay side increases the output current. The smaller the output current, the smaller the current flowing in the battery charging device 1, and therefore the amount of heat generated.

[0030] Here, the control unit 13 grasps the phase of the phase current using a position sensor (not shown) or the like provided in the generator 2 in order to control the phase of the energization timing for the phase current.

[0031] For example, when the temperature of the switching elements Q (Q1 to Q6) rises, the control unit 13 performs advance angle control to advance the phase of the switching elements Q (Q1 to Q6) relative to the phase of the phase current before the temperature exceeds an upper limit. By shifting the phase of the switching elements Q (Q1 to Q6) to the advance angle side, the control unit 13 can reduce the current flowing through the switching elements Q (Q1 to Q6) and suppress the amount of heat generated.

[0032] Next, with reference to FIG. 3, an example of phase control in which the control unit 13 controls the phase of the energization timing so that the temperature of the switching elements Q (Q1 to Q6) does not exceed an upper limit value will be described.

[0033] 3 is a timing chart showing an example of phase control according to this embodiment, in which the horizontal axis represents time (t), and the diagram shows the temperature of the switching element Q (element temperature), the output current of the battery charger 1, the output voltage (charging voltage of the battery 3), and the phase angle of the energization timing.

[0034] Here, the temperature (element temperature) of the switching element Q monitored by the control unit 13 is, for example, the highest temperature among the temperatures of the switching elements Q1 to Q6. Note that the temperature (element temperature) of the switching element Q monitored by the control unit 13 may be the temperature of any one of the switching elements Q1 to Q6.

[0035] Furthermore, here, Limit1 (an example of a first threshold) and Limit2 (an example of a second threshold) are set as thresholds (upper limits) for the temperature (element temperature) of the switching element Q. For example, Limit2 is set to the rated temperature of the switching element Q, and Limit1 is set to a temperature slightly lower than the rated temperature.

[0036] When the control unit 13 starts charging the battery 3 at time t0, it controls the phase of the switching element Q to the retard side (positive side) and charges the battery 3 with an appropriate output current. For example, as the charging voltage increases, the control unit 13 gradually reduces the amount of retardation by which the phase is retarded, thereby gradually reducing the output current. Furthermore, as charging begins, the element temperature gradually increases.

[0037] At time t1, the charging voltage reaches the target voltage, and the control unit 13 adjusts the output current in accordance with the target voltage. For example, the control unit 13 controls the phase to be slightly delayed so that the charging voltage maintains the target voltage. The element temperature continues to rise gradually.

[0038] At time t2, the element temperature reaches Limit1, so the control unit 13 controls the phase of the switching element Q to the advance side (negative side) and limits the output current (reduces the output current) so that the element temperature does not exceed Limit1. Although the charge voltage gradually decreases due to the decrease in output current, the control unit 13 continues to control the phase of the switching element Q to the advance side (negative side) while the element temperature reaches Limit1.

[0039] In this way, when the element temperature reaches Limit1, the control unit 13 performs advance angle control to advance the phase of the switching element Q relative to the phase of the phase current.

[0040] At time t3, the element temperature falls below Limit1, so the control unit 13 releases the limit on the output current and adjusts the output current in accordance with the target voltage, as in the period from time t1 to time t2, causing the charging voltage to gradually recover toward the target voltage.

[0041] At time t4, the element temperature rises sharply and reaches Limit2, so the control unit 13 limits the output current further (reduces the output current further) than when Limit1 was reached. That is, the control unit 13 controls the phase of the switching element Q further to the advance side (negative side) than when Limit1 was reached.

[0042] In this way, when the element temperature reaches Limit2, the control unit 13 performs advance angle control to advance the phase of the switching element Q with respect to the phase of the phase current further than when Limit1 was reached.

[0043] At time t5, the element temperature drops to Limit1, and the control unit 13 then shifts to the same control as in the period from time t2 to time t3.

[0044] In addition, in FIG. 3, an example is shown in which two threshold levels, Limit1 and Limit2, are set as the upper limit value of the element temperature, but the threshold level determined as the upper limit value may be only Limit1, or three or more threshold levels may be set.

[0045] As described above, the battery charging device 1 according to this embodiment includes a bridge rectifier circuit 12, thermistors T (T1 to T6), and a control unit 13. The bridge rectifier circuit 12 controls the on / off states of switching elements Q (Q1 to Q6) connected between the output signal line of the generator 2, which outputs AC power, and the battery 3, thereby rectifying AC power and outputting DC power as charging power for the battery 3. The thermistors T (T1 to T6) are an example of a temperature detection unit for detecting the temperatures of the switching elements Q (Q1 to Q6). The control unit 13 controls the phase of the switching elements Q (Q1 to Q6) based on the temperature detected by the thermistors T (T1 to T6), thereby controlling the charging current for the battery 3.

[0046] As a result, the battery charging device 1 detects the temperature of the switching element Q, which generates the most heat within the battery charging device 1, and controls the charging current of the battery 3 by controlling the phase of the switching element Q based on the detected temperature, thereby preventing damage due to temperature rise without stopping the output of the charging current.

[0047] In addition, since the battery charging device 1 is equipped with a protection circuit that controls the charging current based on the temperature of the switching element Q, it may become unnecessary to perform a temperature measurement test on the battery charging device 1 (unit) for each vehicle.

[0048] Furthermore, eliminating the need to conduct temperature testing of the battery charging device 1 (unit) for each vehicle reduces the labor burden on the vehicle manufacturer, eliminates the need for design changes based on the results of temperature testing, and eliminates concerns about major design setbacks.

[0049] For example, when the temperature detected by the thermistor T (T1 to T6) reaches Limit1 (an example of a first threshold value), the control unit 13 performs advance angle control to advance the phase of the switching element Q (Q1 to Q6) relative to the phase of the AC current (phase current) output from the generator 2.

[0050] As a result, when the temperature of the switching element Q rises, the battery charger 1 can reduce the charging current so that the temperature does not exceed the upper limit.

[0051] Furthermore, when the temperature detected by the thermistor T (T1 to T6) reaches Limit2 (an example of a second threshold value) that is higher than Limit1 (an example of a first threshold value), the control unit 13 performs advance angle control to advance the phase of the switching element Q (Q1 to Q6) further than when Limit1 is reached relative to the phase of the AC current (phase current) output from the generator 2.

[0052] As a result, when the temperature of the switching element Q rises further rapidly, the battery charger 1 can further reduce the charging current so that the temperature does not exceed the upper limit.

[0053] For example, the switching elements Q (Q1 to Q6) are MOSFETs (Metal Oxide Semiconductor Field Effect Transistors).

[0054] This allows the battery charger 1 to charge the battery 3 relatively efficiently.

[0055] In addition, the control unit 13 (an example of a control device) that controls the battery charging device 1 in this embodiment monitors the temperature of the switching elements Q (Q1 to Q6) detected by the thermistors T (T1 to T6), and controls the charging current of the battery 3 by controlling the phase of the switching elements Q (Q1 to Q6) based on the temperature detected by the thermistors T (T1 to T6).

[0056] As a result, the control unit 13 that controls the battery charging device 1 detects the temperature of the switching element Q that generates the most heat within the battery charging device 1, and controls the charging current of the battery 3 by controlling the phase of the switching element Q based on the detected temperature, thereby preventing damage due to temperature rise without stopping the output of the charging current.

[0057] In addition, the control method for the battery charging device 1 according to this embodiment includes the steps of monitoring the temperature of the switching elements Q (Q1 to Q6) detected by the thermistors T (T1 to T6), and controlling the charging current of the battery 3 by controlling the phase of the switching elements Q (Q1 to Q6) based on the temperature detected by the thermistors T (T1 to T6).

[0058] As a result, the control method of the battery charging device 1 detects the temperature of the switching element Q that generates the most heat within the battery charging device 1, and controls the charging current of the battery 3 by controlling the phase of the switching element Q based on the detected temperature, thereby preventing damage due to temperature rise without stopping the output of the charging current.

[0059] Second Embodiment Next, a second embodiment of the present invention will be described. In the first embodiment, the phases of the switching elements Q1 to Q6 are uniformly controlled, but there may be cases where differences in temperature occur among the switching elements Q1 to Q6. For example, if the generator 2 is a three-phase AC generator and switching elements Q are arranged above and below each arm of the U-phase, V-phase, and W-phase, there may be cases where differences in temperature occur among the switching elements Q1 to Q6 depending on the arrangement locations.

[0060] 4 is an image diagram of the variation in element temperature according to this embodiment. For example, on the circuit board, the location where switching elements Q1 and Q4 are located is on the side of the vehicle that is closer to a heat source such as the engine, and the location where switching elements Q3 and Q6 are located is on the side closer to the outside, such as the cowl.

[0061] In this case, the temperature gradually changes from low to high from the side closer to the outside (the right side in the figure) to the side closer to the heat source (the left side in the figure). Even if the switching elements Q1 to Q6 are controlled to have the same current flowing through them, the temperature of the switching elements Q2 and Q5 will be higher than the temperature of the switching elements Q3 and Q6, and the temperature of the switching elements Q1 and Q4 will be even higher than the temperature of the switching elements Q2 and Q5.

[0062] Therefore, the battery charging device 1 according to this embodiment monitors the temperature of each of the switching elements Q1 to Q6 and individually controls the phase of each element. For example, in the example shown in FIG. 4, the phase of the switching elements Q1 and Q4, which have a relatively higher temperature among the switching elements Q1 to Q6, is advanced to reduce the current flow, and the phase of the switching elements Q3 and Q6, which have a lower temperature, is retarded to increase the current flow. This compensates for the decrease in output current (charging current for the battery 3) caused by advancing the phase of the switching elements Q1 and Q4. The state in which the temperatures of the switching elements Q1 and Q4 and the switching elements Q3 and Q6 are the same as the temperatures of the switching elements Q2 and Q5 (i.e., the state in which all of the switching elements Q1 to Q6 are the same temperature) represents a state in which the maximum performance is achieved.

[0063] FIG. 5 is a timing chart showing an example of phase control according to this embodiment. In this diagram, the horizontal axis represents time (t), and the diagram shows changes in element temperature, line current, output current of the battery charger 1, output voltage (charging voltage of the battery 3), and phase angle of energization timing. Here, the upper limit (threshold) of element temperature is referred to as Limit. This Limit corresponds to, for example, Limit 1 in FIG. 3, but multiple thresholds may be set, as in the example shown in FIG. 3.

[0064] In this embodiment, the temperature of each switching element Q is monitored and phase control is performed individually. Here, of the switching elements Q1 to Q6 shown in FIG. 4, the element temperatures, phase angles, and line currents of the corresponding phases are shown as examples for two elements, switching element Q1 (high temperature side) and switching element Q6 (low temperature side).

[0065] 3, when charging of battery 3 starts at time t0, the element temperature gradually increases. Although control unit 13 controls switching element Q1 and switching element Q6 at the same phase angle, the temperature of switching element Q1 increases faster than that of switching element Q6 due to the difference in their locations.

[0066] At time t1, the element temperature of switching element Q1 reaches Limit. Therefore, the control unit 13 controls the phase of switching element Q1 to the advance side (negative side) to prevent the element temperature of switching element Q1 from exceeding Limit, thereby limiting (reducing) the line current of the corresponding phase of switching element Q1. Furthermore, the control unit 13 controls the phase of switching element Q6 to the retard side (positive side), thereby increasing the line current of the corresponding phase of switching element Q6 by the amount of the reduction in the line current of the corresponding phase of switching element Q1. This maintains the output current without reducing it. Note that while the temperature rise of switching element Q1 is suppressed, the temperature of switching element Q6 continues to rise.

[0067] At time t2, the temperature of switching element Q6 reaches Limit, so like the phase of switching element Q1, the phase of switching element Q6 is also controlled to the advance side (- side), and the line current of the corresponding phase of switching element Q6 is limited (reduced). Because the temperatures of both switching element Q1 and switching element Q6 have reached Limit, the line current of the corresponding phase of switching element Q1 and the line current of the corresponding phase of switching element Q6 are both limited (reduced), and the output current decreases.

[0068] At time t3, the temperatures of both switching element Q1 and switching element Q6 fall below Limit, so the control unit 13 releases the limit on the output current. Here, because the output voltage has not reached the target value, the control unit 13 controls the phases of both switching element Q1 and switching element Q6 to the retard side (positive side), thereby increasing the line current and the output current.

[0069] As described above, in the battery charging device 1 according to this embodiment, the bridge rectifier circuit 12 includes a plurality of switching elements Q1 to Q6. A plurality of thermistors T are provided corresponding to the plurality of switching elements Q1 to Q6 to detect the respective temperatures of the switching elements Q1 to Q6. The control unit 13 performs advance angle control to advance the phase of the switching element Q corresponding to a thermistor T among the plurality of thermistors T1 to T6 whose detected temperature has reached Limit (an example of a first threshold value) relative to the phase of the AC current (phase current) output from the generator 2. The control unit 13 also performs delay angle control to delay the phase of the switching element Q corresponding to at least one thermistor T among the plurality of thermistors T1 to T6 whose detected temperature has not reached Limit (an example of a first threshold value) relative to the phase of the AC current (phase current) output from the generator 2.

[0070] This allows the battery charging device 1 to suppress temperature variations in each element while allowing current to flow to the maximum extent possible within the range in which the temperature of each element does not exceed the upper limit, thereby making it possible to bring out the maximum performance of the battery charging device 1.

[0071] Although the embodiments of the present invention have been described above in detail with reference to the drawings, the specific configurations are not limited to the above-described embodiments, and the present invention also includes designs that do not deviate from the gist of the present invention. For example, the configurations described in the above-described embodiments can be combined in any manner.

[0072] In the above embodiment, an example was shown in which the generator 2 is a three-phase AC generator, but the type of the generator 2 is not limited to a three-phase AC generator.

[0073] The battery charging device 1 described above has an internal computer system. The processing by the control unit 13 described above is stored in the form of a program on a computer-readable recording medium, and the computer reads and executes this program to perform the processing. Here, the computer-readable recording medium refers to a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, etc. Alternatively, the computer program may be distributed to a computer via a communication line, and the computer that receives the program may execute the program.

[0074] Furthermore, some or all of the functions of the battery charging device 1 in the above-described embodiment may be realized as an integrated circuit such as an LSI (Large Scale Integration). Each function may be individually implemented as a processor, or some or all of the functions may be integrated into a processor. The integrated circuit method is not limited to LSI, and may be implemented using a dedicated circuit or a general-purpose processor. Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology, an integrated circuit based on that technology may be used.

[0075] REFERENCE SIGNS LIST 1 Battery charging device, 2 Generator, 3 Battery, 11 Capacitor, 12 Bridge rectifier circuit, 13 Control unit, 14 Power supply unit, Q (Q1 to Q6) Switching element, T (T1 to T6) Thermistor, R (R1 to R6) Resistor

Claims

1. A battery charging device comprising: a bridge rectifier circuit that outputs, as charging power for the battery, DC power obtained by rectifying AC power by controlling on / off of a switching element connected between an output signal line of a generator that outputs AC power and the battery; a temperature detection unit that detects the temperature of the switching element; and a control unit that controls the charging current of the battery by controlling the phase of the switching element based on the temperature detected by the temperature detection unit.

2. The battery charging device according to claim 1, wherein when the temperature detected by the temperature detection unit reaches a first threshold value, the control unit performs an advanced angle control to advance the phase of the switching element with respect to the phase of the AC current output from the generator.

3. The battery charging device according to claim 2, wherein when the temperature detected by the temperature detection unit reaches a second threshold value higher than the first threshold value, the control unit performs an advanced angle control to further advance the phase of the switching element with respect to the phase of the AC current output from the generator compared to when the first threshold value is reached.

4. The bridge rectifier circuit includes a plurality of the switching elements, the temperature detection unit includes a plurality provided corresponding to each of the plurality of switching elements to detect the temperature of each of the plurality of switching elements, and the control unit performs an advanced angle control to advance the phase of the switching element corresponding to the temperature detection unit among the plurality of temperature detection units whose detected temperature has reached the first threshold value with respect to the phase of the AC current output from the generator, and performs a retarded angle control to retard the phase of the switching element corresponding to at least one of the plurality of temperature detection units whose detected temperature has not reached the first threshold value with respect to the phase of the AC current output from the generator. The battery charging device according to claim 2.

5. The battery charging device according to claim 1, wherein the switching element is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor).

6. A control device for controlling a battery charging device including a bridge rectifier circuit that outputs, as charging power for the battery, DC power obtained by rectifying AC power by controlling the on / off of a switching element connected between an output signal line of a generator that outputs AC power and the battery, and a temperature detection unit for detecting the temperature of the switching element, the control device monitoring the temperature detected by the temperature detection unit and controlling the charging current of the battery by controlling the phase of the switching element based on the temperature detected by the temperature detection unit.

7. A control method for a battery charging device including a bridge rectifier circuit that outputs, as charging power for the battery, DC power obtained by rectifying AC power by controlling the on / off of a switching element connected between an output signal line of a generator that outputs AC power and the battery, and a temperature detection unit for detecting the temperature of the switching element, the control method including steps of: a control unit monitoring the temperature detected by the temperature detection unit; and controlling the charging current of the battery by controlling the phase of the switching element based on the temperature detected by the temperature detection unit.

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