KR20190063340A - Dc-dc converter for multi-load - Google Patents

Abstract

Embodiments of the present invention provide a DC-DC converter capable of multi-load control in which a primary circuit unit is configured to include at least one slave bridge to one master bridge, thereby charging several electric cars and forklift trucks having different allowable charging voltage ranges of a battery by using a single charging system.

Description

[0001] DESCRIPTION [0002] DC-DC CONVERTER FOR MULTI-LOAD [

Embodiments of the present invention relate to a DC-DC converter capable of multi-load control.

The following description merely provides background information related to the embodiments of the present invention and does not constitute prior art.

Recently electric vehicles (EVs) are the next generation of technology that is drawing attention of various governments and corporations as well as various international organizations along with the key of green growth policy.

Such an electric vehicle receives electric energy from the outside, charges it into the battery, and uses a voltage charged in the battery to drive the motor to obtain power. BACKGROUND OF THE INVENTION [0002] Chargers for electric vehicles require a DC-DC converter capable of supplying a DC voltage of a wide voltage range to an output as a device for providing a voltage required for charging a battery built in an electric vehicle.

Recently, charging technologies for electric vehicles and forklift charging systems of 3.3 kW and 6.6 kW per 1: 1 unit have been developed at home and abroad.

However, it is difficult to cope with the demand for charging system due to the rapid growth of the e-mobility market including electric vehicles and forklifts by the 1: 1 unit charging system technology.

Therefore, in order to construct an efficient charging system environment and to cope with new market demand, it is necessary to charge a plurality of electric vehicles and forklifts using one charging system.

The embodiments of the present invention provide a multi-output multi-tap structure multi-load controllable DC-DC converter capable of selectively charging a plurality of electric vehicles with one charging system by selectively controlling an output voltage using a master bridge and a slave bridge. DC converter according to the present invention.

One embodiment of the invention includes at least two transformers comprising a primary winding, a core and a secondary winding; A master bridge having a plurality of switching elements alternately operated with a predetermined duty cycle to receive electrical energy from the outside and transfer electrical energy to the at least two transformers, And at least two switching elements connected in parallel with the master bridge and operating in a phase shift manner based on the operation of the master bridge for transmitting electrical energy to the at least two transformers, A primary circuit portion including a slave bridge; At least two secondary circuit units connected to the at least two transformers for receiving electric energy from the master bridge and the at least one slave bridge, rectifying the received electric energy, and delivering the electric energy to at least one battery located outside; And a controller for controlling a part or all of the plurality of switching elements included in the master bridge and the at least two slave bridges.

According to an embodiment of the present invention, it is possible to provide a multi-output multi-tap structure DC-DC converter capable of charging a plurality of electric vehicles with one charging system.

According to another aspect of the embodiment of the present invention, when the multi-load operation is performed, since the individual charging systems for the respective loads operate in a phase shift manner, there is an effect that the ripple of the output energy can be reduced .

1 is a circuit diagram of a DC-DC converter capable of multi-load control according to an embodiment of the present invention.
FIG. 2 is a circuit diagram and waveform diagram when one electric vehicle is connected to a DC-DC converter capable of multi-load control according to an embodiment of the present invention shown in FIG.
FIG. 3 is a circuit diagram and waveform diagram when a plurality of electric vehicles are connected to a DC-DC converter capable of multi-load control according to an embodiment of the present invention shown in FIG.
FIG. 4A is a circuit diagram for simulating a DC-DC converter capable of multi-load control according to an embodiment of the present invention, and FIG. 4B shows a simulation result using the circuit diagram of FIG. 4A.
FIG. 5 is a circuit diagram of a DC-DC converter capable of multi-load control according to an embodiment of the present invention.
Fig. 6 shows an example in which two slave bridges included in the circuit shown in Fig. 5 control the individual output voltages by performing a phase shift operation.
7 is an example of a secondary circuit part applicable to a DC-DC converter capable of multi-load control according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in different drawings. In the following description of the present invention, detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In describing the components of the embodiments according to the present invention, the first, second, i), ii), a), b) and the like can be used. Such a code is intended to distinguish the constituent element from other constituent elements, and the nature of the constituent element, the order or the order of the constituent element is not limited by the code. It is also to be understood that when a component is referred to as being "comprising" or "comprising," it should be understood that it is not intended to exclude other components, it means.

Hereinafter, a DC-DC converter capable of multi-load control according to embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a circuit diagram of a DC-DC converter capable of multi-load control according to an embodiment of the present invention.

The DC-DC converter 100 capable of multi-load control according to an embodiment of the present invention includes a primary circuit unit 110, a secondary circuit unit set 120, a control unit 130, and a transformer set 140. A DC-DC converter 100 capable of multi-load control according to an embodiment of the present invention receives electric energy from outside and performs conversion and rectification, and thereafter supplies electric power to a battery (not shown) included in an electric vehicle such as a forklift, golf cart, As shown in FIG.

The primary circuitry 110 may include one master bridge 114 and at least two slave bridges 112,116. The master bridge 114 may include two switching elements Q ₃ and Q ₄ . The master bridge 114 receives electric energy V _IN from the outside and switches in phase shift manner with at least one slave bridge selected from at least two slave bridges 112 and 116 to generate a direct current (DC) voltage Into a high-frequency voltage. Here, the two switching elements Q ₃ and Q ₄ , that is, the first master bridge switching element Q ₃ and the second master bridge switching element Q ₄ included in the master bridge 114 are connected to the controller 130 And performs a switching operation. In addition, the first master bridge switching device Q ₃ and the second master bridge switching device Q ₄ can alternately operate with a predetermined duty cycle. Here, the predetermined duty cycle means a ratio of the activation time for turning on the two switching elements Q ₃ and Q ₄ to operate. Here, the duty cycle between the first master bridge switching device Q ₃ and the second master bridge switching device Q ₄ included in the master bridge 114 may be set to have a duty cycle of 50%. That is, each of the two switching elements Q ₃ and Q ₄ may be set to have the same ratio of turn-on times.

The master bridge 114 includes a first master node, a second master node, and a third master node. The first master node is a node electrically connected to an external power source as one end of both ends of the first master bridge switching device Q _3. The second master node has a first master bridge switching device Q ₃ and a second master Bridge switching element Q ₄ and the third master node is the other end not connected to the first master bridge switching element Q ₃ at both ends between the second master bridge switching elements Q ₄ , And is a node electrically connected to a power source.

The first master node is electrically connected to one end of the external power source and the first slave node of at least one slave bridge and the second master node is electrically connected to each of the primary winding portions of the at least one transformer, The master node is electrically connected to the other end of the external power source and the third slave node of the at least one slave bridge.

At least two slave bridges included in the DC-DC converter 100 capable of multi-load control according to an embodiment of the present invention shown in FIG. 1 include a first slave bridge 112 and a second slave bridge 116 . The first slave bridge 112 includes two switching elements Q ₁ and Q ₂ , that is, a first slave bridge switching element Q ₁ and a _first slave bridge switching element Q ₂ , The bridge 116 includes two switching elements Q ₅ and Q ₆ , that is, a 2 a slave bridge switching element Q ₅ and a 2 b slave bridge switching element Q ₆ . Each of the first slave bridge 112 and the second slave bridge 116 receives the control signal from the controller 130 and switches the phase of the control signal with the master bridge 114 in a phase shift manner to convert the DC voltage into a high frequency voltage .

The secondary circuit part set 120 is electrically connected to each of the secondary winding parts of the transformer set 140 to rectify the voltage applied from the secondary winding part of the transformer set 140. The secondary circuit part set 120 may include at least two secondary circuit parts 122, 124. The secondary circuit units 122 and 124 included in the secondary circuit unit set 120 are connected to the transformers 142 and 144 corresponding to the respective secondary circuit units 122 and 124, And is electrically connected to each of the secondary windings of the transformer 144 to receive electrical energy from the first transformer 142 and the second transformer 144, respectively. Each of the secondary circuit units 122 and 124 rectifies the electric energy applied from each of the secondary windings of the transformers 142 and 144 to transfer the DC voltage to the battery included in the electric vehicle located outside.

The DC-DC converter 100 capable of multi-load control according to an embodiment of the present invention includes a primary circuit unit 110 and a first transformer 142, a primary circuit unit 110 and a second transformer A first capacitor C _B1 and a second capacitor C _B2 that are respectively located between the first and second capacitors C ₁ and C 4. The capacitors C _B1 and C _B2 serve to block the DC bias voltage transmitted to the first transformer 142 and the second transformer 144, respectively.

The controller 130 transmits control signals to the plurality of switching elements included in each of the master bridge 114 and the at least one slave bridge 112 and 116 included in the primary circuit unit 110, Can be individually turned on or turned off. The control unit 130 may alternately turn on and off the plurality of switching elements included in the master bridge 114 and the plurality of switching elements included in the at least one slave bridge 112 and 116 in a 50% And the master bridge 114 and the at least one slave bridge 112, 116 may be controlled based on a phase shift pulse width modulation (PWM) scheme. In addition, the controller 130 may turn on or off part or all of the switching elements included in the master bridge 116 and the at least one slave bridge 112 and 116 at the same time.

The transformer set 140 includes at least two transformers, i.e., a first transformer 142 and a second transformer 144. The number of transformers included in the transformer set 140 can be adjusted according to the number of secondary circuit units included in the secondary circuit group 120, that is, the number of electric vehicles to be charged. Each of the transformers included in the transformer set 140 includes a primary winding portion including at least one winding, a core and a secondary winding portion formed by including at least one winding, Is transformed to a winding ratio between the primary winding portion and the secondary winding portion and is transferred to the secondary winding portion.

The primary winding of each of the transformers included in the transformer set 140 is connected to a node located between the plurality of switching elements included in the master bridge 114 and at least one of the slave bridge 112, And a second stage connected to a node located between the plurality of switching elements included in one slave bridge.

The multi-load controllable DC-DC converter 100 according to an embodiment of the present invention further includes a capacitor between the node located between the plurality of switching elements included in the master bridge 114 and the first end of the transformer . These capacitors act to block the DC bias voltage delivered to each transformer.

FIG. 2 is a circuit diagram and waveform diagram when one electric vehicle is connected to a DC-DC converter capable of multi-load control according to an embodiment of the present invention shown in FIG.

Referring to FIGS. 1, 2A and 2B, the master bridge 114 of the multi-load controllable DC-DC converter 100 according to the embodiment of the present invention has a 50% Lt; RTI ID = 0.0 > duty cycle. ≪ / RTI > The control signals G ₃ and G ₄ for switching the two switching elements Q ₃ and Q ₄ included in the master bridge 114 are alternately applied with a fixed duty cycle of 50% The control signals G ₁ and G ₂ for switching the two switching elements Q ₁ and Q ₂ included in the switching element 112 are alternately applied with a fixed duty cycle of 50%. Here, a control signal for driving the two switching elements Q ₅ and Q ₆ included in the second slave bridge 116 is not applied.

In this case, the two switching elements Q ₃ and Q ₄ included in the master bridge 114 operate alternately with a fixed duty cycle of 50%, and two switching elements Q ₁ and Q ₂ included in the first slave bridge 112 Q ₁ and Q ₂ perform an operation of performing a phase shift operation on the master bridge 114 to control the output voltage B ₀₂ of one secondary circuit unit 124 included in the secondary circuit group 120 . This is because the node b and the first slave bridge 112, which are nodes located between the first master bridge switching device Q ₃ and the second master bridge switching device Q ₄ , which are two switching devices included in the master bridge 114, two switching elements in the 1a slave bridge switching elements (Q ₁₎ and the 1b slave bridge switching elements (Q ₂₎ which is confirmed by the waveforms of V _ba voltage value between the nodes of the node a is located between contained in .

Since the second slave bridge 116 is not operating, the other secondary circuit part 122 included in the secondary circuit part set 120 is not driven and is electrically connected to the secondary circuit part 122 The first transformer 142 included in the set of transformers 140 which are not connected is also not driven. This can be confirmed also in the waveform diagram of FIG. 2 (b) showing the current I _T1 flowing through the first transformer 142.

3 is a circuit diagram and waveform diagram when a plurality of electric vehicles are connected to a DC-DC converter capable of multi-load control according to an embodiment of the present invention.

In this case, the two switching elements Q ₃ and Q ₄ included in the master bridge 114 operate alternately with a fixed duty cycle of 50%, and two switching elements Q ₁ and Q ₂ included in the first slave bridge 112 Q ₁ and Q ₂ included in the second slave bridge 116 and the two switching elements Q ₅ and Q ₆ included in the second slave bridge 116 perform a phase shift operation with respect to the master bridge 114, (B ₀₁ , B _o2 ) of the two secondary circuit sections 122, 124 included in the control signal. The operation of the DC-DC converter capable of multi-load control shown in FIG. 3 is the same as the operation of the DC-DC converter 100 capable of multi-load control described with reference to FIG.

FIG. 4A is a circuit diagram for simulating a DC-DC converter capable of multi-load control according to an embodiment of the present invention, and FIG. 4B shows a simulation result using the circuit diagram of FIG. 4A.

The multi-load controllable DC-DC converter circuit of FIG. 4A includes five slave bridges, five transformers, and five secondary circuit sections to allow charging of five different electric vehicles.

4B shows the voltage between the node located between the node located between the two switching elements included in the master bridge and the slave bridge, and FIG. 4B shows the voltage from each of the transformers to each of the transformers (C) of FIG. 4B is an output voltage applied to both ends of the battery of the electric vehicle located outside.

As can be seen from the waveform diagram of FIG. 4B, the switching elements of the slave bridge individually perform a phase shift operation around the master bridge to stably control the output voltage.

FIG. 5 is a circuit diagram of a DC-DC converter capable of multi-load control according to an embodiment of the present invention.

The extended multi-load controllable DC-DC converter includes a master bridge 510, at least two slave bridges 520, a control unit 530, at least two transformers, and at least two secondary circuit units. The extended multi-load controllable DC-DC converter of FIG. 5 includes four transformers, one master bridge, four transformers for charging four different electric vehicles: a forklift, a golf cart, a ladder car and a four- Slave bridges and four secondary circuitry. That is, the circuit diagram of FIG. 5 is the same as adding two slave bridges, two transformers, and two secondary circuit sections to the DC-DC converter 100 capable of multi-load control of FIG. Two slave bridges are connected in parallel with the master bridge, one end of each of the two transformers is connected to a node between two switching elements included in the master bridge, and the other end of each of the two transformers is connected to the other two slave bridges Lt; RTI ID = 0.0 > switching elements. ≪ / RTI > In the embodiment of FIG. 5, a DC-DC converter capable of multi-load control for charging four different electric vehicles has been described, but the number of electric vehicles for charging is not limited thereto. That is, when charging N different electric vehicles, N slave bridges may be formed in one master bridge, and N transformers and N secondary circuits may be formed. In this way, the DC-DC converter capable of multi-load control according to an embodiment of the present invention can simultaneously charge a plurality of electric vehicles having built-in batteries having different charging voltage allowable ranges.

Fig. 6 shows an example in which two slave bridges included in the circuit shown in Fig. 5 control the individual output voltages by performing a phase shift operation.

A DC-DC converter capable of multi-load control according to an embodiment of the present invention includes a master bridge 610, a first slave bridge 622, a second slave bridge 624, a third slave bridge 626, A primary circuit portion including a slave bridge 628, a control portion 630, a plurality of transformers, and a number of secondary circuit portions corresponding to the number of transformers. The operation principle of the DC-DC converter capable of multi-load control according to the embodiment of the present invention shown in FIG. 6 is the same as the basic operation principle of the DC-DC converter capable of multi-load control shown in FIG.

In this case, the master bridge 610, the first slave bridge 622 and the second slave bridge 624 are operated in the primary circuit portion to perform the operation for charging two different or identical electric vehicles, The third slave bridge 626 and the fourth slave bridge 628 do not operate. In the circuit diagram shown in Fig. 6, only the upper two transformers and the two secondary circuit portions corresponding to the transformers operate.

6A shows the overall circuit operation while the first master bridge switching device Q ₁ , which is one of the two switching elements included in the master bridge 610, is turned on, and FIG. Shows the overall circuit operation while the second master bridge switching element Q ₂ , which is one of the two switching elements included in the master bridge 610, is turned on.

The first slave bridge 622 and the second slave bridge 624 are driven around the first master bridge switching device Q ₁ and the second master bridge switching device Q ₂ included in the master bridge 610 in both cases. ) Performs a phase shifting operation, and individually controls the output voltages (B _o1 , B _o2 ) of the secondary circuit through these operations.

The master bridge 610 includes a first master node, a second master node, and a third master node. The first master node is a node electrically connected to an external power source as one end of both ends of the first master bridge switching device Q _1. The second master node has a first master bridge switching device Q ₁ and a second master Bridge switch element Q ₂ and the third master node is the other end not connected to the first master bridge switching element Q ₁ at both ends between the second master bridge switching elements Q ₄ And a node electrically connected to an external power source.

The first master node includes one end of an external power source, a first slave node of the first slave bridge 622, a first slave node of the second slave bridge 624, a first slave node of the third slave bridge 626, And is electrically connected to the first slave node of the fourth slave bridge 628. The second master node is electrically connected to the upper end of the primary winding portion of the first transformer located at the uppermost one of the five transformers and the lower end of the primary winding portion of the fifth transformer located at the lowermost end of the first transformer. The third master node is connected to the other end of the external power source, the third slave node of the first slave bridge 622, the third slave node of the second slave bridge 624, the third node of the third slave bridge 626, Lt; RTI ID = 0.0 > slave < / RTI > bridge 628.

The second slave node b of the first slave bridge 622, the second slave node c of the second slave bridge 624, the second slave node d of the third slave bridge 626, Each of the second slave nodes e of the slave bridge 628 is connected to the lower end of the primary winding portion of the first transformer and the upper end of the primary winding portion of the second transformer, the lower end of the primary winding portion of the second transformer, The upper end of the winding section, the lower end of the primary winding section of the third transformer, the upper end of the primary winding section of the fourth transformer, and the upper end of the primary winding section of the fifth transformer. Also, the electrical connection between each node and the top of the primary winding of each transformer may be via a capacitor.

7 is an example of a secondary circuit part applicable to a DC-DC converter capable of multi-load control according to an embodiment of the present invention.

The secondary circuit units 122 and 124 rectify the electric energy of the high frequency voltage transmitted from the transformer and transfer the electric energy to both ends of the battery of the electric vehicle located outside, thereby charging the battery.

Each of the secondary circuit portions 122 and 124 may be formed to include a selected one of a full-bridge rectifier circuit, a center-tapped rectifier circuit, and a current doubler rectifier circuit .

The full-bridge rectification circuit is formed to include at least four diodes and at least one inductor, and the mid-tap rectification circuit is formed to include at least two diodes and at least one inductor. Here, in the case of a mid-tap rectifier circuit, a node located between two windings included in a transformer is connected to one end of both ends included in the battery of an electric vehicle, and one diode of at least two diodes is connected to at least one inductor And the other end of the battery is connected to the other end of the battery.

Referring to Figure 7 (a), the pull-freeze rectifying circuit includes a first diode, a second diode, a third diode, a fourth diode and a first inductor. The cathode of the first diode is electrically connected to the cathode of the third diode and one end of the first inductor and the anode of the first diode is connected to one end of both ends included in the output portion of the at least two transformers, 2 < / RTI > diode. The anode of the second diode is electrically connected to the anode of the fourth diode and one end of the battery and the anode of the third diode is electrically connected to the other end of both ends of the output of the at least two transformers and the cathode of the fourth diode, . The other end of the first inductor is electrically connected to the other end of the battery.

Referring to Figure 7 (b), the mid-tap rectifier circuit includes a first diode, a second diode, and a first inductor. The cathode of the first diode is electrically connected to the cathode of the second diode and one end of the first inductor. The anode of the first diode is electrically connected to one end of the output of the transformer and the anode of the second diode is electrically connected to the other end of the output of the transformer.

Referring to FIG. 7 (c), it includes a first diode, a second diode, a first capacitor, and a second capacitor. The cathode of the first diode is electrically connected to one end of the first capacitor and one end of the first inductor. The anode of the first diode is electrically connected to one end of both ends included in the secondary winding portion of the transformer and the cathode of the second diode. The anode of the second diode is electrically connected to one end of the second capacitor and one end of the battery. The other end of the first capacitor is electrically connected to the other end of both ends included in the secondary winding portion of the transformer and the other end of the second capacitor. The other end of the first inductor is electrically connected to the other end of at least one battery.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventive concept. Various modifications and variations will be possible. Therefore, the embodiments according to the present invention are intended to illustrate rather than limit the technical idea of the embodiments, and the scope of the technical idea of the embodiments is not limited by these embodiments. The scope of protection of embodiments according to the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be interpreted as being included in the scope of the embodiments of the present invention.

110: Primary circuit
112, 622: first slave bridge
114, 510, 610: master bridge
116, 624: second slave bridge
120: Secondary circuit part set
122, 124: secondary circuit portion
130, 530, 630:
140: Transformer set
142, 144: Transformer
520: Slave bridge aggregation
626: Third slave bridge
628: Fourth slave bridge

Claims (11)

At least two transformers including a primary winding portion, a core and a secondary winding portion;
A master bridge having a plurality of switching elements alternately operated with a predetermined duty cycle to receive electrical energy from the outside and transfer electrical energy to the at least two transformers, At least two slaves connected in parallel with the master bridge and having a plurality of switching elements to operate and operating in a phase shift manner based on the operation of the master bridge to transfer electrical energy to the at least two transformers, A primary circuit portion including a slave bridge;
At least two secondary circuit units connected to the at least two transformers for receiving electric energy from the master bridge and the at least one slave bridge, rectifying the received electric energy, and delivering the electric energy to at least one battery located outside; And
And a control section for controlling a part or all of the plurality of switching elements included in the master bridge and the at least two slave bridges,
DC converter capable of multi-load control. The method according to claim 1,
Wherein the primary winding section includes:
A first node connected between a node located between a plurality of switching elements included in the master bridge and a capacitor, and a second node connected between a node located between the plurality of switching elements included in the at least one slave bridge, Wherein the DC-DC converter includes two stages. 3. The method of claim 2,
Wherein,
DC converter according to claim 1 or 2, wherein the controller controls the two switching elements included in the master bridge so as not to operate simultaneously. The method of claim 3,
Wherein,
DC converter according to claim 1 or 2, wherein the controller controls the two switching elements included in each of the at least one slave bridge to not operate simultaneously. 5. The method of claim 4,
Wherein the at least one slave bridge comprises:
DC converter according to claim 1, wherein the DC-DC converter is configured to have the same number as the number of the at least one battery. 6. The method of claim 5,
Wherein each of the at least two secondary circuit portions comprises:
A DC-DC controllable multi-load control circuit comprising a selected one of a full-bridge rectifier circuit, a full-bridge rectifier circuit, a center-tapped rectifier circuit and a current doubler rectifier circuit. Converter. The method according to claim 6,
Wherein the master bridge comprises a first master node, a second master node and a third master node, wherein the first master node is electrically connected to one end of an external power source and a first slave node of the at least one slave bridge Wherein the second master node is electrically connected to each of the inputs of the at least one transformer and the third master node is electrically connected to the other end of the external power source and the third slave node of the at least one slave bridge DC converter according to claim 1, 6. The method of claim 5,
Wherein each of the at least two secondary circuit portions comprises:
And a cathode of the first diode is electrically connected to the cathode of the third diode and one end of the first inductor, wherein the cathode of the first diode is electrically connected to the cathode of the third diode and the one end of the first inductor, and the first diode, the second diode, the third diode, An anode of the first diode is electrically connected to one end of both ends included in the secondary winding portion and a cathode of the second diode, and an anode of the second diode is connected to the anode of the fourth diode and the anode of the second diode. The anode of the third diode is electrically connected to the other end of both ends included in the secondary winding portion and the cathode of the fourth diode, and the other end of the first inductor is electrically connected to one end of the at least one battery, Wherein the at least one battery is electrically connected to the other end of the at least one battery. 6. The method of claim 5,
Wherein each of the at least two secondary circuit portions comprises:
Wherein the cathode of the first diode is electrically connected to the cathode of the second diode and one end of the first inductor and the anode of the first diode is connected to the cathode of the second diode And the anode of the second diode is electrically connected to the other end of the two ends of the secondary winding portion, wherein the anode of the second diode is electrically connected to one end of both ends of the winding portion. 6. The method of claim 5,
Wherein each of the at least two secondary circuit portions comprises:
Wherein a cathode of the first diode is electrically connected to one end of the first capacitor and one end of the first inductor, and the cathode of the first diode is connected to one end of the second capacitor Wherein the anode of the second diode is electrically connected to one end of both ends included in the secondary winding portion and the cathode of the second diode and the anode of the second diode is electrically connected to one end of the second capacitor and one end of the at least one battery The other end of the first capacitor is electrically connected to the other end of both ends included in the secondary winding part and the other end of the second capacitor and the other end of the first inductor is electrically connected to the other end of the at least one battery To-DC converter. The method according to claim 1,
Wherein the duty cycle ratio between the two switching elements included in the master bridge and the duty cycle ratio between the two switching elements included in each of the at least one slave bridge are 1: DC-DC converter.

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