WO2014057577A1 - Power supply device and battery charging device - Google Patents

Abstract

The present invention is equipped with a transformer (13), which has a primary coil wherein a coil between coil terminals a-b and a coil between coil terminals b-c are connected in series; and switching circuit units (18), which select any of the coils of the primary coil and apply a power supply voltage. In addition, a control unit (15) switches the coil of the primary coil supplying the electricity two or more times during one cycle of voltage deviation of an alternating current power supply (1), thereby causing the alternating current power supply to operate as a power supply which uses the transformer (13) with an appropriate turn ratio corresponding to the changing power supply voltage. By lowering the turn ratio and performing an appropriate switching operation when the power supply voltage is high the efficiency can be increased, and by increasing the turn ratio when the power supply voltage is low, it is possible to output prescribed power even with a low power supply voltage.

Description

Power supply device and battery charging device

The present invention relates to a power supply device such as a DC / DC converter or an AC / DC converter that outputs a predetermined voltage from a varying power supply voltage, and a battery charging device using the power supply device.

In the tide of reducing carbon dioxide emissions that promote global warming, the small amount of carbon dioxide emissions has been accepted, the demand for electric vehicles has increased, and the spread has been accelerated.
A power battery mounted on the electric vehicle is charged by an external AC power source using a charging device, and the battery charging device has a coil (reactor) and a switching element for efficiently taking in power from the AC power source. For example, a power factor correction (PFC) circuit configured by a DC / DC converter including a transformer, a switching element, and the like is used. The electric vehicle is also equipped with a DC / DC converter that generates a 12V power supply for auxiliary equipment from a power battery. Note that a series of configurations for outputting a DC voltage from the AC power supply can also be referred to as an AC / DC converter.

As described above, a PFC circuit that supplies a substantially constant DC voltage while improving the power factor is used in the front stage of the DC / DC converter of the charging device that charges the power battery from the AC power supply. In other words, in order to operate the DC / DC converter suitably, a PFC circuit that supplies a constant DC voltage is necessary, and the supply voltage to the DC / DC converter fluctuates using a simple PFC circuit. If this is the case, the DC / DC converter cannot perform a suitable operation.
Further, the power battery serving as the power source of the DC / DC converter that generates the 12V power source for the auxiliary device is not necessarily a stable DC power source because the voltage varies depending on the charging state. In other words, it is difficult to say that the DC / DC converter always operates under a suitable power supply voltage.

In the power supply environment where the optimum voltage may not be supplied as described above, the DC / DC converter used for the battery charger and the auxiliary device is expected to fluctuate the power supply voltage. In response to fluctuations, priority was given to the operation in the extreme state, and in some states, the design was admitted to allow the deterioration of the characteristics.
For example, in a charging device composed of a PFC circuit and a DC / DC converter, there are typically two types of AC power supply voltage to be connected: a 100 Vrms system and a 200 Vrms system. If designing with emphasis on 200 Vrms, a 100 Vrms power supply is used. There is no denying the decrease in efficiency when used.
In addition, in a DC / DC converter that generates a 12V power supply for auxiliary equipment, a transformer having a turn ratio that outputs 12V from the lowest voltage of the power battery voltage, and the output is limited to 12V even at the highest voltage of the power battery voltage. Although a switching element that operates with a narrow duty that can be used is required, the efficiency cannot be denied in the operation with the narrow duty.

Hereinafter, a conventional example will be described in which a technique corresponding to fluctuations in the power supply voltage input to the DC / DC converter and a device to which the DC / DC converter is applied are described.

The power supply device according to Patent Document 1 is an AC / DC converter that switches a tap of a primary winding of a transformer in correspondence with the level of an AC power supply voltage (that is, a rectifier and a smoothing unit that convert AC power supply voltage to DC). And a DC / DC converter to which a direct current is supplied), and appropriately selects and switches the winding ratio of the transformer to control the on-duty of the switching transistor to about 50%.
In this patent document 1, for example, a transformer tap is selected and switched corresponding to an AC power source having an effective value of 100 Vrms to 240 Vrms, and corresponds to a voltage at each timing in one cycle of the AC power source changing in a sine wave shape. There is no description indicating that the taps are sequentially switched.

The booster circuit according to Patent Document 2 is a circuit for boosting and taking out stored power stored in an electric double layer capacitor, and includes a DC / DC converter that boosts the voltage of the capacitor. When the voltage of the capacitor decreases, the winding number reduction means (switching circuit) reduces the number of turns on the primary side of the transformer to increase the step-up ratio of the transformer, thereby avoiding a decrease in output voltage.
As described in paragraph [0025] of Patent Document 2, “the switching circuit 19 has a contact point 19a of an electromagnetic relay”, a slow-operating relay is used for switching the number of turns. Therefore, the switching operation is not frequently performed in a short cycle such as one cycle of the AC power supply.

The DC / DC converter according to Patent Document 3 can be used even if the polarity of the DC power supply voltage is reversed using a bidirectional switching element.
In this patent document 3, there is no description indicating that the turns ratio of the transformer is switched according to the power supply voltage, and there is no description that suggests using an AC power supply as the power supply.

The uninterruptible power supply method according to Patent Document 4 uses a bi-directional semiconductor switch to charge an AC / AC converter that directly modulates an AC power supply voltage without converting it to DC and demodulates it on the secondary side, and a storage battery. And an AC / DC converter that outputs an alternating current from the storage battery.
Paragraph [0025] of this patent document 4 describes that the circuit configuration on the primary side of the transformer is switched between the full-bridge type and the half-bridge type in accordance with the power supply voltages of 100 Vrms and 200 Vrms. There is no description indicating that the turn ratio of the transformer is sequentially switched in accordance with the voltage at each timing in one cycle of the AC power supply that changes in a wave shape.

JP 2000-209855 A JP 2012-115112 A JP 2012-65444 A Japanese Patent Laid-Open No. 10-174437

A conventional DC / DC converter, for example, as described in Patent Document 1 above, absorbs fluctuations in one cycle of an AC power supply to generate a constant DC voltage, and operates the DC / DC converter suitably. Therefore, a rectifier circuit and a smoothing circuit for smoothing a change corresponding to a half cycle of the AC power supply and a PFC circuit for outputting a smoothed voltage are required. The smoothing capacitor of this configuration needs to have a sufficient capacity in order to ensure the characteristics of the DC / DC converter over the half cycle of the AC power supply. Therefore, in order to secure the characteristics of the DC / DC converter, it is desired to reduce this capacity, but the reduction or elimination of the smoothing capacitor is an issue for reducing the size and cost of the power supply device. It was. That is, it is possible to configure a DC / DC converter (an AC / DC converter that includes a series of circuits from an AC power supply) that operates properly even when the power supply voltage supplied to the DC / DC converter fluctuates. It is a problem of making it cheaper and cheaper.
Note that the above-mentioned Patent Document 1 uses a smoothing capacitor to generate a direct-current voltage that favorably operates the DC / DC converter, and further increases the efficiency of the DC / DC converter. In accordance with the effective values (for example, 100 Vrms and 200 Vrms), the transformer turns ratio is temporarily switched. Therefore, there is no description of the configuration of a DC / DC converter that operates favorably when a voltage that varies from moment to moment in a sinusoidal form is supplied, and the reduction of the smoothing capacitor is not considered as an issue.

The present invention has been made in order to solve the above-described problems, and a power supply device (DC / DC converter) that outputs a predetermined voltage from a power supply whose voltage fluctuates from time to time. The voltage fluctuates in a sine wave shape. It is an object of the present invention to provide a power supply device (AC / DC converter) that outputs a predetermined voltage from an AC power supply and a battery charging device using the power supply device.

The power supply device (DC / DC converter and AC / DC converter) of the present invention includes a transformer having a primary winding constituted by a plurality of windings connected in series and a plurality of windings of the primary winding. A switching circuit having a plurality of switching elements connected to the control circuit, and a controller that controls operation of the switching elements and selectively applies a power supply voltage to the plurality of windings constituting a primary winding, The control unit controls the switching element to switch the winding to which the power supply voltage is applied among the primary windings twice or more corresponding to the voltage at that time in one cycle of the varying power supply voltage. Is.

The battery charging device of the present invention is for charging a battery mounted on a vehicle using the power supply device described above.

According to the present invention, the primary coil winding to which the power supply voltage is applied fluctuates and is switched twice or more corresponding to the current voltage during one cycle of the fluctuation of the power supply voltage. As a transformer having an appropriate turns ratio with respect to the power supply voltage of the power supply, in a situation where the power supply voltage is low, by switching to the primary winding having a high turn ratio, a predetermined voltage can be obtained from the low power supply voltage. Can be output. In a situation where the power supply voltage is high, the efficiency can be increased by switching to the primary winding having a low turns ratio and performing an appropriate switching operation. Therefore, it is possible to provide a power supply device (DC / DC converter) that can output a predetermined voltage from a direct current power supply whose voltage varies every moment.

According to the present invention, when an AC power source is used as a power source, a predetermined voltage can be output even at a timing when the power source voltage in the repetition cycle of the AC power source is low due to the above-described characteristics. A power supply device (AC / DC converter) that is high, has low harmonics, and high power factor can be provided.

According to the present invention, when charging the battery from the AC power source, the above-described characteristics can output a predetermined voltage even when the power source voltage is low in the repetition cycle of the AC power source. It is possible to provide a battery charger having a high power factor, a low high frequency, and a high power factor.

It is a circuit diagram which shows the structure of the battery charging device which concerns on Embodiment 1 of this invention. 6 is a graph illustrating operation waveforms when only switches SW1 to SW4 are used in the battery charging apparatus according to Embodiment 1. 6 is a graph for explaining operation waveforms when all of switches SW1 to SW6 are used in the battery charging apparatus according to the first embodiment. 6 is a circuit diagram showing a modification of the battery charging device according to Embodiment 1. FIG. 6 is a graph for explaining operation waveforms when an overvoltage protection unit and a snubber unit are added to the battery charging apparatus according to Embodiment 1; 6 is a circuit diagram showing a modification of the battery charging device according to Embodiment 1. FIG. It is a circuit diagram which shows the structure of the battery charging device which concerns on Embodiment 2 of this invention. FIG. 6 is a circuit diagram showing a modification of the battery charging device according to Embodiment 2. It is a circuit diagram which shows the structure of the battery charging device which concerns on Embodiment 3 of this invention. FIG. 6 is a diagram illustrating a transformer according to a third embodiment. 10 is a graph illustrating operation waveforms when all of switches SW1 to SW8 are used in the battery charging apparatus according to Embodiment 3. It is a circuit diagram which shows an example of the signal transmission circuit of the battery charging device which concerns on Embodiment 4 of this invention. FIG. 12 is a circuit diagram showing another example of a signal transmission circuit of a battery charging device according to Embodiment 4. FIG. 12 is a circuit diagram showing another example of a signal transmission circuit of a battery charging device according to Embodiment 4. FIG. 12 is a circuit diagram showing another example of a signal transmission circuit of a battery charging device according to Embodiment 4. It is a circuit diagram which shows the structure of the battery charging device which concerns on Embodiment 5 of this invention. It is a figure explaining the installation example of the battery charging device which concerns on Embodiment 5. FIG. It is a circuit diagram which shows the structure of the battery charging device which concerns on Embodiment 6 of this invention. It is a figure explaining the example of installation of the battery charging device which concerns on Embodiment 6. FIG. FIG. 10 is an external perspective view illustrating a transformer according to a sixth embodiment.

Hereinafter, in order to explain the present invention in more detail, modes for carrying out the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
The battery charger 10 shown in FIG. 1 converts an alternating-current power supply voltage that changes every moment into a predetermined voltage (battery voltage) using, for example, an alternating-current power supply 1 having a period of 20 ms (50 Hz) or 17 ms (60 Hz) as a power supply. Thus, the battery 2 is charged. The present invention relates to a power supply device including a DC / DC converter, but the filter capacitor C1 of the power supply rectifier 11 for full-wave rectification of the AC voltage is a small-capacitance capacitor for noise filters and has almost no smoothing action. The voltage rectified by the power supply rectification unit 11 is a voltage in which a sinusoidal half-wave voltage is repeated while being DC. Accordingly, the behavior of the PFC / DC / DC converter 12 with respect to the voltage supplied to the PFC / DC / DC converter 12 and the voltage is equivalent to the half cycle of the alternating current. The operation will be described according to the behavior when.

In FIG. 1, a battery charger 10 includes a power rectifier 11 that rectifies an AC voltage of an AC power supply 1 and outputs a DC voltage, a PFC / DC / DC converter 12 that converts a DC voltage into a battery voltage, and a PFC. An output rectification unit 14 that rectifies and smoothes the output voltage of the DC / DC converter unit 12 and supplies it to the battery 2 and a control unit 15 that operates the switches SW1 to SW6 of the switching circuit unit 18. The battery charging device 10 in FIG. 1 can be rephrased as an AC / DC converter that inputs an AC voltage and outputs a DC voltage.

In the power supply rectification unit 11 provided on the primary side of the PFC / DC / DC converter unit 12, the AC voltage of the AC power supply 1 is full-wave rectified by the four rectification diodes D1 to D4, and a sinusoidal half-wave voltage is repeated. It is converted into a DC voltage. On the other hand, in the output rectification unit 14 provided on the secondary side of the PFC / DC / DC converter unit 12, the output voltage of the PFC / DC / DC converter unit 12 is full-wave rectified by the four rectifier diodes D5 to D8, It is smoothed by the smoothing coil L1 and the smoothing capacitor C2 and converted into a DC voltage.
The circuit configurations of the power rectifier 11 and the output rectifier 14 are not limited to the illustrated example.

The PFC / DC / DC converter unit 12 includes a transformer 13 having a primary winding in which a plurality of windings are connected in series, a secondary winding, and a plurality of windings constituting the primary winding. And a switching circuit unit 18 for selectively applying a voltage to the terminals a to c. In the switching circuit unit 18, the switches SW 1 to SW 6 are turned on and off by the drive signal output from the control unit 15 to switch the connection between the winding terminals a to c and change the turns ratio of the primary winding and the secondary winding. . In the illustrated example, the number of winding turns between the winding terminals ac and the number of winding turns between the winding terminals ab are made equal.

The control unit 15 controls the on / off operation of the switches SW1 to SW6 based on the power supply voltage rectified by the power supply rectification unit 11, and when the power supply voltage is low in one cycle of the power supply voltage, the winding terminal a− The power supply voltage is applied between b and when the power supply voltage is high, the power supply voltage is applied between the winding terminals ac. For convenience, the connection of the winding terminals a to c of the primary winding of the transformer 13 is switched twice or more in one cycle of the power supply voltage.
Further, the control unit 15 performs phase control, PWM (Pulse Width Modulation) operation or PFM (Pulse) on the switches SW1 to SW6 based on the output voltage (or output current, power supply current) after rectification and smoothing by the output rectification unit 14. (Frequency Modulation) is operated to adjust the output voltage (or output current, power supply current).

The control unit 15 is configured to perform digital control using a microcomputer having a high-speed arithmetic function, analog control using an error amplifier circuit composed of an operational amplifier or the like, or digital-analog control combining a general-purpose microcomputer and an error amplifier circuit. Etc.

First, the case where only the switches SW1 to SW4 are used without operating the switches SW5 and SW6 (fixed in the off state) will be described with reference to FIG. 2A shows the power supply voltage of the AC power supply 1, FIG. 2B shows the energization direction of the transformer 13, FIG. 2C shows the output voltage of the rectifier diodes D5 to D8, and FIG. Is an output current (that is, an input current of the battery 2).
As described above, the voltage supplied to the PFC / DC / DC converter unit 12 and the behavior of the PFC / DC / DC converter unit 12 with respect to the voltage are equivalent to the half cycle of the alternating current. It substitutes by description of the operation | movement corresponding to a power supply voltage.

The switches SW1 and SW4 are repeatedly turned on and off at the same timing (for example, 50% duty), and a current flows between the winding terminals ac of the primary winding when turned on. On the other hand, the switches SW2 and SW3 are repeatedly turned on and off by reversing the operation of the switches SW1 and SW4 at the same timing, and a current flows between the winding terminals ca of the primary winding when turned on. (When switch SW1 is on, switch SW4 is also on and switches SW2 and SW3 are off. Conversely, when switch SW1 is off, switch SW4 is also off and switches SW2 and SW3 are on.)

As shown in FIGS. 2 (c) and 2 (d), the output rectifier 14 outputs a voltage that is twice the turn ratio of the voltage applied to the primary winding, but the battery has constant voltage characteristics. Therefore, when the output voltage is less than or equal to the battery voltage, no current flows, and the current starts flowing after exceeding the battery voltage. Therefore, at the timing T _L when the power supply voltage is low, the power at the timing T _L is not used at all. That is, when the AC power source 1 that changes in a sine wave shape is used, the voltage range used in one cycle is narrow, that is, the period during which current flows is narrow. The power usage efficiency is low. In addition, since the period during which current flows in one cycle of the AC power supply is narrow and the power supply current to be received is close to a rectangular wave, there are many harmonic components, and there is concern about the effect on other devices connected to the same AC power supply. The

In the description of FIG. 2 above, the on / off of the switches SW1 to SW4 is set to 50% Duty for convenience. However, as a power supply device for charging a battery having a constant voltage characteristic, the timing T _H when the power supply voltage is a high voltage is used. In order to prevent an excessive output current from flowing, the duty of the voltage applied between the winding terminals a-c and the winding terminals c-a is narrowed by phase control or PWM / PFM operation. the efficiency is deteriorated in the most communicated likely those timing T _H power.

In the case of phase control, the control unit 15 alternately turns on and off one of the switches SW1 and SW2 with a duty of about 50%, and turns on and off the other switches SW3 and SW4 alternately with a duty of about 50%. The output voltage is adjusted by shifting the operation phase of SW1 and SW2 and the operation phase of switches SW3 and SW4 and changing the energization time for energizing the transformer 13. In the case of PWM operation, the control unit 15 makes the ON / OFF repetition cycle of the switches SW1 to SW4 constant, and the ON time of the switch SW1 (that is, the OFF time of the switch SW2) and the ON time of the switch SW3 ( That is, the output voltage is adjusted by changing the ratio of the off time of the switch SW4. In the case of PFM operation, the control unit 15 repeats turning on the switches SW1 and SW3 while keeping the on time of the switch SW1 (at this time the switch SW2 is off) and the on time of the switch SW3 (at this time the switch SW4 is off). The output voltage is adjusted by changing the period.

Next, a case where all the switches SW1 to SW6 are used will be described with reference to FIG. 3A is the power supply voltage of the AC power supply 1, FIG. 3B is the energization direction of the transformer 13, FIG. 3C is the output voltage of the rectifier diodes D5 to D8, and FIG. Is an output current (that is, an input current of the battery 2).

At the timing _TL when the power supply voltage is low, the switches SW1 and SW6 are repeatedly turned on and off at the same timing (for example, 50% duty), and a current flows between the winding terminals a and b of the primary winding when turned on. On the other hand, the switches SW2 and SW5 are repeatedly turned on and off by reversing the operation of the switches SW1 and SW6 at the same timing, and a current flows between the winding terminals ba of the primary winding when turned on. The switches SW1 and SW6 and the switches SW2 and SW5 are alternately turned on and off. During this time, the switches SW3 and SW4 are fixed off.
As described above, as shown in FIG. 3C, at the timing _TL when the power supply voltage is low, by increasing the turns ratio of the transformer 13, an appropriate voltage is generated from the low voltage and the charging current is supplied to the battery 2. It can flow.

On the other hand, in the power supply voltage higher timing _{T H,} as in the case of FIG. 2, a switch SW1, SW4 and the switch SW2, SW3 are repeatedly turned on and off alternately between the winding terminals a-c and the winding terminal c- An electric current is passed alternately between a. During this time, the switches SW5 and SW6 are fixed off.
By lowering the turns ratio of the transformer 13 in the power supply voltage is high timing T _H, can generate an appropriate voltage from this high voltage supplying the charging current to the battery 2.

As described above, by using all switches SW1 ~ SW6, also in the power supply voltage is low timing T _L, in order to power those timing T _L is used, the voltage range to be used in one cycle Expansion, that is, the period during which current flows can be expanded.
When the power source of the battery charging device 10 is alternating current, the energization current in the region indicated by hatching in FIG.
That is, since the power factor can be improved by the PFC / DC / DC converter unit 12 of this configuration, there is no need to provide a PFC circuit such as the chopper circuit 10 shown in FIG. In addition to reducing the number of smoothing capacitors, the PFC circuit can be simplified, and the power supply device can be made smaller and less expensive.
In addition, since the power supply current to be received can be approximated to a sine wave by expanding the period during which the current flows in one cycle of the AC power supply, harmonic components that affect the power supply side can also be suppressed.

Further, by appropriately switching the turns ratio of the transformer 13 in accordance with the power supply voltage of the AC power supply 1 at that time, the switches SW1 to SW6 can be operated with a wide duty at the respective timings T _H and T _L. As a result, the efficiency can be increased at the respective timings T _H and T _L and further in the entire period.

Next, a specific example of the switches SW1 to SW6 will be described.

FIG. 4 shows a circuit configuration of the battery charging device 10a when a field effect transistor (FET) is used for the switches SW1 to SW6. In the PFC / DC / DC converter section 12a, the switching circuit 18a uses the switching elements FET1 to FET6 as the switches SW1 to SW6, and includes backflow prevention diodes D9 and D10 for preventing current backflow to the switching elements FET3 and FET4. . The operations of the switching elements FET1 to FET6 are the same as the operations of the switches SW1 to SW6 described with reference to FIG.

In the above configuration, when the control unit 15 operates the switching elements FET1, FET2, FET5, and FET6 to energize between the winding terminals ab and between the winding terminals ba, the winding terminal c of the transformer configuration. Since a voltage is also generated, a voltage not lower than the power supply voltage or not higher than the GND voltage is applied to the terminals of the switching elements FET3 and FET4, so that parasitic diodes (not shown) in the switching elements FET3 and FET4 are applied. A current flows, and a current flows backward through the switching elements FET3 and FET4 (arrows in FIG. 4). Therefore, in order to prevent backflow of the current, backflow prevention diodes D9 and D10 are connected in series. By installing the backflow prevention diodes D9 and D10, backflow of the current can be prevented, the DC / DC converter can be operated normally without destroying the switching elements FET3 and FET4, and sufficient output can be obtained. .

In FIG. 4, an overvoltage protection unit 16 and a snubber unit 17 are provided between the winding terminal a and the winding terminal c of the transformer 13. The overvoltage protection unit 16 is a circuit in which, for example, the anodes or the cathodes of two Zener diodes are connected, and the surge voltage generated when the energization direction between the winding terminals of the primary winding is switched is increased. Suppresses the voltage section to a limited voltage. The snubber portion 17 is an RC circuit including, for example, a resistor R1 and a capacitor C3, and absorbs this surge energy.

5A shows the power supply voltage of the AC power supply 1, FIG. 5B shows the energization direction of the transformer 13, and FIG. 5C shows the winding terminal of the transformer 13 when the overvoltage protection section 16 and the snubber section 17 are provided. FIG. 5D shows the voltage between winding terminals ac when no overvoltage protection unit 16 and snubber unit 17 are provided. Note that positive and negative voltages are generated between the winding terminals a and c in accordance with the voltage applied between the winding terminals a and b. FIGS. 5 (c) and 5 (d) For convenience, the absolute value is converted from the minus side to the plus side.
When a current is applied between the winding terminals a and b of the primary winding, a voltage is also generated between the winding terminals a and c, and a surge is generated as shown in FIG. However, this surge can be suppressed as shown in FIG. 5C by providing the overvoltage protection unit 16 and the snubber unit 17.

FIG. 6 shows a circuit configuration of the battery charging device 10b when bidirectional switches are used for the switches SW1 to SW6. In the PFC / DC / DC converter section 12b, bidirectional switching elements FET11 to FET16 are used as the switches SW1 to SW6. Moreover, the overvoltage protection part 16 and the snubber part 17 are provided similarly to FIG.
In the above configuration, only the switching elements FET3 and FET4 need to be bidirectional switches, and the other switching elements FET1, FET2, FET5 and FET6 do not necessarily need to be bidirectional switches. In FIG. 6, in order to unify the elements to be used, all are bidirectionally compatible.

The bidirectional switching element FET11 is composed of two switching elements FET11a and 11b connected in series. Similarly, the bidirectional switching element FET12 is switching elements FET12a and 12b, the bidirectional switching element FET13 is switching elements FET13a and 13b, the bidirectional switching element FET14 is switching elements FET14a and 14b, and the bidirectional switching element FET15 is switching elements FET15a and 15b. The bidirectional switching element FET16 is composed of switching elements FET16a and 16b. The operations of these bidirectional switching elements FET11 to FET16 are the same as the operations of the switches SW1 to SW6 described with reference to FIG.

As described above, when the unidirectional switching elements FET3 and FET4 are used, it is necessary to connect the backflow prevention diodes D9 and D10 in series so that the current does not flow backward, but the bidirectional switching elements FET13 and FET14 Can be used to pass and stop the current in both forward and reverse directions, and since the series backflow prevention diodes D9 and D10 are not used, the loss due to the series backflow prevention diodes D9 and D10 can be reduced and the efficiency is improved. improves.

As described above, according to the first embodiment, the battery charger 10 is configured by a plurality of windings connected in series (a winding between the winding terminals ab and a winding between the winding terminals bc). A transformer 13 having a primary winding, a switching circuit unit 18 having a plurality of switches SW1 to SW6 individually connected to a plurality of winding terminals a to c constituting the primary winding, and switches SW1 to A control unit 15 that controls the operation of the SW 6 to selectively apply a power supply voltage to a plurality of windings constituting the primary winding, and an output rectifying unit 14 that rectifies the output voltage of the transformer 13 is provided. The unit 15 is configured to switch the winding for applying the power supply voltage among the primary windings two or more times corresponding to the voltage at that time in one cycle of the fluctuation of the varying power supply voltage.
For this reason, for example, when using a DC power source whose voltage varies from moment to moment, such as the output of a DC power source that rectifies the output of an AC generator on which AC component ripple is superimposed, the momentarily changes. By operating as a transformer with an appropriate turns ratio with respect to the changing power supply voltage at that time, in a situation where the power supply voltage is low, switching to the primary winding with a high turn ratio allows the low power supply voltage to be predetermined. Can be output. In a situation where the power supply voltage is high, the efficiency can be increased by switching to the primary winding having a low turns ratio and performing an appropriate switching operation. Therefore, a highly efficient power supply device (DC / DC converter) with a wide usable power supply voltage range can be realized.
Also, with this configuration, it is possible to reduce the number of smoothing capacitors and realize a power supply device using a simple PFC circuit.
In addition, since the power supply current to be received can be made to flow almost continuously by expanding the period in which the current flows in one cycle of the changing power supply, harmonic components that affect the power supply side can be suppressed.

When the battery charging device 10 using the AC power source 1 as a power source is configured using the PFC / DC / DC converter unit 12 for the DC power source, a power source rectifying unit 11 that rectifies the AC voltage of the AC power source 1 is added. The voltage after rectification is applied to the primary winding of the transformer 13. This configuration also has a characteristic of outputting a predetermined voltage even when the power supply voltage is low in the repetition cycle of the AC power supply, as described above, and this characteristic provides high power use efficiency and low harmonics. In addition, a power unit having a high power factor (an AC / DC converter including a power rectifier 11 and a PFC / DC / DC converter 12) can be configured.

Furthermore, the battery chargers 10, 10a, 10b according to the first embodiment may be used as a battery charger for charging a battery 2 for driving an electric vehicle, and directly plugged into a home or commercial AC power source 1. Can be connected to charge the battery 2 for power.

In addition, according to the first embodiment, the switching circuit unit 18a has the backflow prevention diodes D9 and D10 that block the backflow of current through the switching elements FET3 and FET4. As a result, reverse current flow can be prevented, so that the DC / DC converter can be operated normally without destroying the switching element, and sufficient output can be obtained.

Further, according to the first embodiment, the bidirectional switching elements FET11 to FET16 are used as the switching elements of the switching circuit unit 18b. As a result, the backflow prevention diodes D9 and D10 can be reduced, so that the loss caused by the backflow prevention diodes D9 and D10 can be reduced and the efficiency can be improved.

In the above description, two FETs are used as the switching elements. However, the present invention is not limited to this, and may be one switching element having equivalent characteristics, such as a transistor, IGBT (insulated gate type). A bipolar transistor) may be used. In addition to conventional Si (silicon) semiconductors, GaN (gallium), which can increase current density, has low on-resistance, has a short switching time, and can operate at high frequencies, is included as a semiconductor constituting these switching elements. A nitride (gallium nitride) based semiconductor or SiC (silicon carbide, silicon carbide) based semiconductor can also be used. The GaN-based or SiC-based semiconductor has a high withstand voltage and can operate at a high temperature. Therefore, as a switching element for a large-capacity power supply device (DC / DC converter, AC / DC converter). Is preferable.

Although not shown, a conversion circuit unit (for example, switches SW1, SW2, SW5, SW6 in FIG. 1) converts the secondary output to AC on the secondary side of the PFC / DC / DC converter unit 12. If the circuit) is added, the battery charger 10 can be configured as a DC / AC inverter, and a DC / AC inverter with a wide usable power supply voltage range and high efficiency can be realized.

In the above description, a configuration is shown in which a plurality of primary windings are used and the windings are switched in response to a varying power supply voltage. However, the same operation is performed with a plurality of secondary windings. Is also possible. In this case, the winding is switched and adjusted to a predetermined output voltage in accordance with voltages generated in a plurality of windings constituting the secondary winding.

Embodiment 2. FIG.
FIG. 7 is a circuit diagram showing a configuration of battery charging apparatus 10c according to the second embodiment. In FIG. 7, parts that are the same as or equivalent to those in FIGS. 1 to 6 are given the same reference numerals, and descriptions thereof are omitted.
In the first embodiment, the power supply rectifying unit 11 that rectifies the AC voltage of the AC power supply 1 is provided. However, in the second embodiment, the switches SW1 to SW6 are all made bidirectionally compatible, as shown in FIG. In addition, the AC voltage of the AC power supply 1 can be directly applied to the transformer 13 without providing the power supply rectifying unit 11. Incidentally, in the first embodiment, it is necessary to add a backflow prevention diode or use a bidirectional switch for the switching elements FET3 and FET4 to which a voltage not lower than the power supply voltage or lower than the GND voltage is applied. However, the other switching elements FET1, FET2, FET5 and FET6 do not necessarily have to be bidirectional switches. On the other hand, in order to delete the power supply rectification unit 11, all of the switches SW1 to SW6 need to be compatible with each other.
As described above, in the second embodiment, the power supply rectifying unit 11 is omitted, and an AC voltage is directly applied to the transformer 13 to obtain a DC output. Therefore, the PFC of the first embodiment is used. The DC / DC converter unit can be rephrased as the PFC / AC / DC converter unit 12c. Since the internal configuration of the PFC / AC / DC converter unit 12c is the same as that of the PFC / DC / DC converter unit 12 of FIG. 1 except that the switches SW1 to SW6 are bidirectionally compatible, description thereof will be omitted. In the configuration of FIG. 7, each winding terminal constituting the primary winding of the transformer 13 is switched four times in one cycle of the sinusoidal fluctuation of the AC voltage.

Next, specific examples of the switches SW1 to SW6 used in the PFC / AC / DC converter unit 12c will be described.
FIG. 8 shows a circuit configuration of a battery charging device 10d using the bidirectional switching elements FET11 to FET16. In the PFC / AC / DC converter unit 12d of FIG. 8, bidirectional switching elements FET11 to FET16 are used as the switches SW1 to SW6 as in FIG. 6, and an overvoltage protection unit 16 and a snubber unit 17 are further provided. By using the bidirectional switching elements FET11 to FET16, the current in any direction can be turned on and off. Therefore, the current is arbitrarily supplied to the transformer 13 regardless of the polarity of the power supply voltage, that is, even with an AC voltage. Can be energized. Further, the backflow of current to the switching elements FET11a to FET16b can be prevented.

As described above, according to the second embodiment, the battery charging device 10d includes a plurality of windings connected in series (a winding between the winding terminals ab and a winding between the winding terminals bc). A switching circuit section 18 having switches SW1 to SW6 individually connected to terminals a to c of a plurality of windings constituting the primary winding, and switches SW1 to SW6 A control unit 15 that selectively applies the power supply voltage of the AC power supply 1 to a plurality of windings constituting the primary winding, and an output rectification unit 14 that rectifies the output voltage of the transformer 13. The control unit 15 is configured to switch the winding for applying the power supply voltage among the primary windings two or more times corresponding to each voltage in one cycle of the fluctuation of the power supply voltage. For this reason, when using the AC power supply 1 whose voltage fluctuates in a sine wave shape, the power supply voltage is low by operating as a transformer having an appropriate turns ratio with respect to the power supply voltage that fluctuates every moment. By switching to the primary winding having a high turn ratio, a predetermined voltage can be output from the low power supply voltage. In a situation where the power supply voltage is high, the efficiency can be increased by switching to the primary winding having a low turns ratio and performing an appropriate switching operation. Therefore, it is possible to configure a power supply device (AC / DC converter) with high power utilization efficiency, low harmonics, and high power factor.
Further, with this configuration, a simpler power supply device can be realized by reducing the number of smoothing capacitors, using a simple PFC circuit, and not using the power supply rectifier diodes (D1 to D4 in FIG. 1).

Furthermore, the battery charging devices 10c and 10d according to the second embodiment may be used as a battery charging device for charging the battery 2 for driving an electric vehicle, and the plug is directly connected to the home or commercial AC power source 1. Thus, the power battery 2 can be charged.

Embodiment 3 FIG.
FIG. 9 is a circuit diagram showing a configuration of battery charging device 10e according to the third embodiment. FIG. 10 is a diagram illustrating the transformer 13e of the battery charging device 10e. 9 and 10, the same or corresponding parts as those in FIGS. 1 to 8 are designated by the same reference numerals and the description thereof is omitted.

In the first and second embodiments, two windings are connected in series to form the primary winding of the transformer 13. However, in the third embodiment, three windings having different numbers of turns are used. The primary winding of the transformer 13e is configured by connecting in series. For example, as shown in FIG. 10, the primary winding of the transformer 13e has 10 turns (T) of windings between the winding terminals ab and 10 turns (T) of windings between the winding terminals bc. 30T, and the number of windings between the winding terminals cd is 20T. The number of turns of the secondary winding of the transformer 13e is 60T.
Further, with the addition of the windings, switches SW7 and SW8 are added to the switching circuit unit 18e.

11 (a) shows the power supply voltage of the AC power supply 1, FIG. 11 (b) shows the winding terminal to which the power supply voltage is applied, and FIG. 11 (c) shows the output voltage of the rectifier diodes D5 to D8. FIG. 11C shows an envelope waveform of the output voltage for each winding switching, not the output voltage waveform for each switching of the energization direction of the transformer 13e.

When the control unit 15 selects between the winding terminals ab as the primary winding of the transformer 13e to which the power supply voltage is applied (that is, the switches SW1, SW6 and the switches SW2, SW5 are alternately turned on / off), the turns ratio A 1: 6 transformer 13e can be configured, and a sufficient output voltage can be output even when the power supply voltage is low.

In response to the rise of the power supply voltage, the control unit 15 next selects between the winding terminals cd of the primary winding to make the turns ratio 2: 6 (that is, the switches SW3 and SW8 and the switches SW4 and SW7). Are alternately turned on / off), and then the winding terminals bc are selected to have a turns ratio of 3: 6 (that is, the switches SW3 and SW6 and the switches SW4 and SW5 are turned on and off alternately) and the winding is continued. The line terminals a-c are selected to have a turns ratio of 4: 6 (that is, the switches SW1, SW4 and the switches SW2, SW3 are turned on and off alternately), and then the winding terminals b-d are selected to turn the number of turns. The ratio is set to 5: 6 (that is, the switches SW5 and SW8 and the switches SW6 and SW7 are turned on and off alternately).

When the power supply voltage approaches the maximum voltage, the control unit 15 selects between the winding terminals ad of the primary winding (that is, the switches SW1 and SW8 and the switches SW2 and SW7 are turned on and off alternately). , A turns ratio 6: 6, that is, a 1: 1 transformer 13e is formed.
Note that the above order is reversed in response to a decrease in the power supply voltage.

FIG. 11 (c) shows the output voltage when the duty of the switch that is turned on / off in each turn ratio period is fixed at 50%, but in actuality, in each period, phase control or PWM · PFM By controlling the duty of the voltage applied to each winding terminal by performing the operation, the output voltage is finely controlled to output a more suitable battery charging current, and the power supply current to be received is further reduced in harmonics Can approximate a sine wave.

The number of windings constituting the primary winding of the transformer 13e, the number of turns of the primary winding and the secondary winding, and connection and selection of each winding constituting the primary winding are other than the above examples. The winding may be separated from other windings.

As described above, according to the third embodiment, the primary winding of the transformer 13e is composed of a plurality of windings having different numbers of turns, and the number of turns is arbitrary according to the combination of these windings. For this reason, by configuring a transformer with a high turns ratio, it is possible to output power even when the power supply voltage is low. In addition, a transformer having a turn ratio suitable for the voltage at each timing of the varying power supply voltage can be configured, and further, by performing an appropriate duty switching operation at the power supply voltage at each timing, power utilization efficiency is high, A high-efficiency power supply (AC / DC converter) can be realized with a high rate, low harmonics.
In addition, this configuration reduces the number of smoothing capacitors, uses a simple PFC circuit, and does not use power supply rectifier diodes (D1 to D4 in FIG. 1) while realizing a simple power supply device. Furthermore, it is possible to realize a power supply device having a high power factor and few harmonics.

Even when the DC power source described in the first embodiment is used as a power source, the power source device having the same effect as described above can be obtained by configuring the primary winding of the transformer as in the third embodiment. (DC / DC converter) can be realized.

Embodiment 4 FIG.
In the fourth embodiment, a configuration in which the control unit 15 drives the switches SW1 to SW6 via an insulated signal transmission circuit will be described. Each of the switching elements constituting the switches SW1 to SW6 operates at a potential floating from the reference voltage. Therefore, as a drive signal transmission circuit for operating each switching element, for example, a pulse transformer 20 as shown in FIGS. An insulated power source 22 and a photocoupler 24 as shown in FIGS. 13 and 15 are used.

12 to 15 are circuit diagrams showing the configuration of the signal transmission circuit of the battery charging apparatus 10 according to the fourth embodiment. The same or corresponding parts as those in FIGS. 1 to 11 are denoted by the same reference numerals. Description is omitted. It should be noted that the control units 15a to 15d show only portions related to transmission of drive signals.
Further, bidirectional switching elements FET11 to FET16 are used as the switches SW1 to SW6, and the bidirectional switching element FET11 (switching element FET11a and switching element FET11b) is shown as a representative.

12, a switching element FET 21 that controls the pulse transformer 20 is connected to the primary side of the pulse transformer 20 in the control unit 15a. The gate terminals of the switching elements FET11a and 11b are connected to the high potential side of the secondary winding of the pulse transformer 20, and the source terminals of the switching elements FET11a and 11b are commonly connected to the low potential side.

In this control unit 15a, a drive signal (on / off signal) for driving the bidirectional switching element FET11 is input to the switching element FET21, and transmitted to the switching elements FET11a and 11b via the pulse transformer 20 in an insulated state. The element FETs 11a and 11b perform an on / off operation at the same timing.

In the control unit 15b shown in FIG. 13, a switching element FET 25 for controlling the photocoupler 24 is connected to the light emitting side of the photocoupler 24. The gate terminals of the switching elements FETs 11a and 11b are connected to the light receiving side of the photocoupler 24 through a gate driving unit 24a. Each source terminal of the switching elements FET 11 a and 11 b is connected to the low potential side of the insulated power supply 22. The insulated power supply 22 is composed of a transformer 22a, a rectifier diode D22, and a smoothing capacitor C22. In response to the control of the switching element FET23, the insulating power supply 22 generates drive power for the switching elements FET11a and 11b and supplies it to the gate drive unit 24a.

In this control unit 15b, the switching element FET 23 driven by the power source rectangular wave signal controls the insulated power source 22, and supplies the driving power for the bidirectional switching element FET 11 to the gate driving unit 24a. In addition, a drive signal (ON / OFF signal) for controlling the operation of the bidirectional switching element FET11 is input to the switching element FET25, and is transmitted in an insulated state to the switching elements FET11a and 11b via the photocoupler 24 and the gate driving unit 24a. Then, the switching elements FET11a and 11b perform the on / off operation at the same timing.

12 and 13, the mutual source terminals of the switching elements FET11a and 11b are connected. However, the present invention is not limited to this, and as shown in FIGS. 14 and 15, the mutual drains of the switching elements FET11a and 11b. Terminals may be connected. When the drain terminals are connected as shown in FIGS. 14 and 15, it is necessary to input drive signals having different potentials to the gate terminals of the switching elements FET11a and 11b. Are provided, and two insulated power supplies 22 are provided so that the photocoupler 24 operates with each power supply.

Further, in addition to the pulse transformer 20 and the photocoupler 24, an insulated signal transmission circuit may be configured using, for example, magnetic coupling means (magnetic isolator) or the like.

As described above, according to the fourth embodiment, the battery charging device 10 receives the drive signals for controlling the operations of the bidirectional switching elements FET11 to FET16 from the control units 15a to 15d in the insulated state. The signal transmission circuit for transmitting to the FET 16 is provided. Therefore, the signal transmission path from the control unit 15 to the bidirectional switching elements FET11 to FET16 can be insulated, the switching circuit unit can be operated favorably, and a power supply device (DC / DC converter or AC / DC converter) can be realized.

Embodiment 5 FIG.
FIG. 16 is a circuit diagram showing a configuration of battery charging device 10f according to the fifth embodiment. FIG. 17 is a diagram illustrating an installation example of the battery charging device 10f. 16 and 17, the same or corresponding parts as in FIGS. 1 to 15 are denoted by the same reference numerals and description thereof is omitted.

In the fifth embodiment, the primary side component 31 incorporating the primary winding of the transformer 13f and the secondary side component 32 incorporating the secondary winding are individually formed and separated from each other. To do. And one primary side structure part 31 is used as an external (ground installation) power supply device connected to the external alternating current power supply 1. FIG. The other secondary side structural part 32 is mounted in an electric vehicle, and an output is connected to the battery 2 for power of the electric vehicle.

When charging the vehicle-mounted battery 2, the vehicle is such that the core wound with the secondary winding of the secondary side component 32 faces the core wound with the primary winding of the primary side component 31. Is stopped (the vehicle is stopped at a position where the transformer 13f is formed by both cores, the primary winding and the secondary winding), and the primary winding and the secondary side configuration portion 32 of the primary side configuration portion 31. The power is transmitted in a non-contact manner by a transformer 13f constituted by the secondary winding of the non-contact.

In the case of non-contact charging, a resonance circuit in which the resonance winding 33 and the resonance capacitor C4 are connected in series is used, and a resonance current is applied to the resonance winding 33 and the resonance capacitor C4. It is desirable to cause the secondary side to resonate.

In FIG. 16, the bidirectional switching elements FET11 to FET16 are used as the switching elements of the switching circuit unit 18, but the present invention is not limited to this. 16 illustrates the PFC / AC / DC converter in which the primary side configuration unit 31 can be directly connected to the AC power source 1. However, the configuration includes the power rectification unit 11 and the PFC / DC / DC converter illustrated in FIG. It doesn't matter.
In FIG. 17, the primary side component 31 is disposed on the ground and the secondary component 32 is disposed below the electric vehicle. However, other arrangements may be used.

As described above, according to the fifth embodiment, the battery charging device 10f includes the power supply device including the primary winding 31 of the transformer 13f, the switching circuit unit 18, and the control unit 15 and the transformer. The secondary side component 32 is separated from the secondary side component 32 having the 13f secondary winding and the output rectifying unit 14, and the primary side component 31 can be disposed outside the vehicle. Made the configuration. For this reason, the battery charger for electric vehicles which can charge a power battery from an external power supply device in a non-contact manner can be realized with a simple configuration using the power supply device.

Embodiment 6 FIG.
FIG. 18 is a circuit diagram showing a configuration of battery charging device 10g according to the sixth embodiment. FIG. 19 is a diagram illustrating an installation example of the battery charging device 10g. 18 and 19, the same or corresponding parts as those in FIGS. 1 to 17 are denoted by the same reference numerals and description thereof is omitted.

In the sixth embodiment, the power supply device described in the fifth embodiment is configured so that the battery 2 mounted on the electric vehicle can be charged by connecting a plug (not shown) directly to the household or commercial AC power supply 40. The second primary side component 41 is provided on the vehicle-mounted side. The second primary side configuration unit 41 includes a second primary winding 42, a switching circuit unit 18 that switches connection of the respective winding terminals a to c of the second primary winding 42, and an overvoltage protection unit. 16 and a snubber part 17.

FIG. 20 shows an external perspective view of the transformer 13g separated into the external power supply device side and the vehicle-mounted side. A primary winding 35 is wound around the core 34 of the primary side component 31 which is one external power supply device. The primary winding 35 is composed of two windings connected in series, and the winding terminals a to c are connected to the primary side component 31 (shown in FIG. 18).

The primary winding 42, the secondary winding 13g-1, and the resonance winding 33 are wound around the core 45 of the other in-vehicle secondary side component 32. The second primary winding 42 is composed of two windings connected in series, and the winding terminals a to c are connected to the second primary side component 41 (shown in FIG. 18). ing. The resonance winding 33 is connected in series with the resonance capacitor C4 as shown in FIG.

When the battery 2 is charged in a non-contact manner using the external power supply device (primary side component 31), the core 45 of the in-vehicle secondary component 32 is replaced with the core 34 of the primary component 31. The vehicle is stopped so as to face each other (the vehicle is stopped at a position where the transformer 13g is constituted by the cores 34, 45, the primary winding 35, and the secondary winding 13g-1). Electric power is transmitted by a transformer 13g composed of the primary winding 35 and the on-vehicle side secondary winding 13g-1.

In the case of charging in a non-contact manner, the control unit 15 turns on a switch of the resonance circuit (for example, the bidirectional switching element FET 36) to resonate the secondary side, and resonates with the resonance winding 33. It is desirable to apply a resonance current to the capacitor C4.

On the other hand, when charging the in-vehicle battery 2 by directly connecting a plug to the AC power source 40, the second primary winding 42 and the secondary winding 13g-1 of the second primary side component 41 are Electric power is transmitted by a transformer 13g constituted by
Note that when charging is performed by directly connecting a plug, the control unit 15 turns off the bidirectional switching element FET 36 of the resonance circuit.

As described above, according to the sixth embodiment, the secondary side component 32 mounted on the vehicle is mounted on the vehicle-mounted side separately from the primary winding 35 of the primary side component 31 disposed outside the vehicle. The second primary winding 42 is provided. For this reason, a part of the transformer is shared by the external power supply device and the in-vehicle battery charging device, so that the power battery can be charged by directly connecting the plug, and the power battery can be connected from the external power supply device in a non-contact manner. A battery charging device that can be charged can be realized by a simple configuration using the power supply device.

In the fifth and sixth embodiments, the battery charging device is configured using the PFC / AC / DC converter unit. However, the battery charging device is configured by the power rectifier unit 11 and the PFC / DC / DC converter shown in FIG. It doesn't matter.

In addition to the above, within the scope of the invention, the invention of the present application can be freely combined with each embodiment, modified any component of each embodiment, or omitted any component in each embodiment. Is possible.

As described above, the power supply device (DC / DC converter or AC / DC converter) according to the present invention has the primary winding of the transformer twice or more corresponding to the voltage at that time in one cycle of the fluctuation of the power supply voltage. Since the wire turns ratio is switched, it is suitable for use in a battery charger for charging a power battery for an electric vehicle.

1,40 AC power supply, 2 battery, 10, 10a-10g battery charger, 11 power rectifier, 12, 12a, 12b PFC / DC / DC converter, 12c-12e PFC / AC / DC converter, 13, 13e ~ 13g transformer, 13g-1 secondary winding, 14 output rectifier, 15, 15a ~ 15d controller, 16 overvoltage protector, 17 snubber, 18, 18a, 18b, 18e switching circuit, 20 pulse transformer, 22 Insulated power supply, 22a transformer, 24 photocoupler, 24a gate drive unit, 31 primary side configuration unit, 32 secondary side configuration unit, 33 resonance winding, 34, 45 core, 35 primary winding, 41 second Primary side component, 42 2nd primary winding, C1 filter capacitor, C2, C22 smooth Capacitor, C3 capacitor, C4 resonance capacitor, D1 ~ D8, D22 rectifier diodes, FET1 ~ FET6, FET21, FET23 switching elements, FET11 ~ FET16, FET36 bidirectional switching element, L1 coil, R1 resistors, SW1 ~ SW8 switch.

Claims (10)

1. A power supply device that outputs a predetermined voltage from a DC power supply voltage that fluctuates in voltage or an AC power supply voltage that fluctuates in a sine wave,
   A transformer having a primary winding constituted by a plurality of windings connected in series;
   A switching circuit having a plurality of switching elements individually connected to the plurality of windings of the primary winding;
   A control unit for controlling the operation of the switching element and selectively applying the power supply voltage to the plurality of windings constituting the primary winding;
   The control unit controls the switching element so that the winding to which the power supply voltage is applied among the primary windings corresponds to the voltage at that time in one cycle of the fluctuating power supply voltage. A power supply device that is switched twice or more.
2. The power supply apparatus according to claim 1, wherein the switching circuit includes a diode that blocks a reverse current flowing in the switching element.
3. The power supply device according to claim 1, wherein the switching element used in the switching circuit is a bidirectional switching element or a bidirectional switching element.
4. The power supply device according to claim 1, wherein the primary winding is constituted by a plurality of windings having different numbers of turns, and the turn ratio of the transformer is arbitrarily switched by a combination of the plurality of windings.
5. The power supply apparatus according to claim 1, further comprising an insulating signal transmission circuit that transmits a signal for controlling an operation of the switching element from the control unit to the switching element.
6. The power supply apparatus according to claim 1, wherein the switching element is a Si-based, GaN-based, or SiC-based element.
7. The control unit adjusts an output voltage, an output current, or a power supply current by performing phase control, PWM (Pulse Width Modulation) operation, or PFM (Pulse Frequency Modulation) operation on the switching element. The power supply described.
8. A battery charger for charging a battery mounted on a vehicle using the power supply device according to claim 1.
9. The primary winding and core of the transformer of the power supply device, the switching circuit, and the primary side component having the control unit are separated from the secondary side component having the secondary winding and core of the transformer. The battery charging device according to claim 8, wherein the secondary side component is mounted on the vehicle, and the primary component is disposed outside the vehicle.
10. 10. The battery according to claim 9, wherein the core of the secondary side component includes a second primary winding separately from the separated primary winding of the primary component. Charging device.

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