KR101552284B1 - An isolated single-switch DC-DC converter - Google Patents

Abstract

The present invention relates to an insulated single-switch DC-DC converter which uses a single switch, a resonant tank, and a lossless snubber to realize soft switching of all elements to minimize loss occurring when switching to obtain high efficiency. The insulated single-switch DC-DC converter comprises: a power source; a filter inductor to remove noise in a voltage outputted from the power source; a transformer to relate a current flowing into a first coil to a second coil; a switch to supply or block the current to the first coil of the transformer; a snubber disposed between the switch and the transformer to remove a surge voltage and realize a soft switching operation of the switch to remove loss occurring when switching; a resonant tank connected to the second coil of the transformer to generate a resonant current; a rectifier unit to rectify and flatten a voltage outputted through the resonant tank to output the rectified and flattened voltage; and a control unit to control the switching operation of the switch.

Description

[0001] The present invention relates to an isolated single-switch DC-DC converter,

The present invention relates to an isolation type single-switch DC-DC converter, and more particularly, to a DC-DC converter of a single-switch type using a single switch and a resonant tank and a lossless snubber, DC converters that can achieve high efficiency by minimizing the losses that occur during the operation of a single-switch DC-DC converter.

Generally, a DC-DC converter (DC-DC converter) is a power device that converts a DC voltage of a certain voltage into a DC voltage of a different voltage. Power systems such as MIC photovoltaic systems, mobile fuel cells, and automotive inverters are used as a device to adjust the output voltage because of the low output voltage and the large fluctuation depending on the load.

Existing active clamp DC-DC converters have a full-bridge, push-pull, half-bridge, flyback, and forward structures.

The full-bridge, push-pull and half-bridge converters are isolated boost converters with low input current ripple, high boost ratio, low magnetizing current and are suitable for high capacity applications. All switches use ZVS (Zero Voltage Switching) It has the advantage of being able to turn on. On the other hand, there is a disadvantage in that a lot of switches are used and a loss occurs due to hard switching when the switch is turned off.

In addition, the flyback and forward converters have the advantage of low switch count and ZVS turn-on of all switches. On the other hand, the flyback converter has a disadvantage in that it has a large magnetizing current and is not suitable for high boost and high power applications due to the structure of an insulated buck-boost converter. In addition, the forward converter has an insulated buck converter structure which is not suitable for high voltage application.

In order to solve the drawbacks of the active clamp DC-DC converter, a conventionally proposed technique is disclosed in the following Non-Patent Document 1: K.-B. Park, C.-E. Kim, G.-W.Moon, and M.-J.Youn, "PWM resonant single-switch isoated converter," IEEE Trans. Power Electron, vol. 24, 8, pp. 1876-1886, Aug. 2009. [Non-Patent Document 2] J. Lee, J. Park, and H. Geon, "Series-connected forward-flyback converter for high step-up power conversion," IEEE Trans. Power Electron, vol. 26, no. 12, pp. 3629-3641, Dec. 2011. [Patent Document 3] A. Emrani, E. Adib, and H. Farzanehfard, "Single-switch soft-switched isolated DC-DC converter," IEEE Trans. Power Electron, vol. 27, no. 4, pp. 1952-1957, Apr. 2012.

K.-B. Park, C.-E. Kim, G.-W.Moon, and M.-J.Youn, "PWM resonant single-switc isoated converter," IEEE Trans. Power Electron, vol. 24, 8, pp. 1876-1886, Aug. 2009. J. Lee, J. Park, and H. Jeon, "Series-connected forward-flyback converter for high step-up power conversion," IEEE Trans. Power Electron, vol. 26, no. 12, pp. 3629-3641, Dec. 2011. A. Emrani, E. Adib, and H. Farzanehfard, "Single-switch soft-switched isolated DC-DC converter," IEEE Trans. Power Electron, vol. 27, no. 4, pp. 1952-1957, Apr. 2012.

However, the above-described conventional techniques have the following problems.

That is, the non-patent document 1, which is a flyback converter applying resonance, and the non-patent document 2, which is a single switch-insulated converter combining flyback and forward, have a disadvantage that high efficiency can not be achieved by hard switching when the switch is turned off have.

In addition, all of the devices are soft-switched and have a small number of elements, but they are disadvantageous in that they are not suitable for high voltage application because of low voltage step ratio.

It is an object of the present invention to solve all the problems of the prior art as described above, and it is an object of the present invention to provide a method and apparatus for solving the above- And to provide an insulated single-switch DC-DC converter capable of achieving high efficiency by minimizing loss.

Another object of the present invention is to provide an insulated single-switch DC-DC converter using a very small-rated lossless snubber and operating independently of the main circuit.

It is still another object of the present invention to provide an insulated single-switch DC-DC converter capable of minimizing the magnetization current of the transformer to reduce the volume of the core.

According to an aspect of the present invention, there is provided an isolated single-switch DC-DC converter including: a source power supply; A filter inductor for eliminating noise introduced into a voltage output from the source power supply; A transformer for inducing a current flowing into the primary coil into a secondary coil; A switch for supplying or blocking a current to the primary coil of the transformer; A snubber that is disposed between the switch and the transformer to remove a surge voltage and implement a soft switching operation of the switch to eliminate losses occurring during switching; A resonance tank connected to a secondary coil of the transformer to generate a resonance current; A rectifying unit for rectifying, smoothing and outputting a voltage output through the resonance tank; And a control unit for controlling the switching operation of the switch.

The switch is implemented as a MOSFET (MOS-FET) or an IGBT (Insulated Gate Bipolar mode Transistor).

The insulation type single-switch DC-DC converter may further include a clamp capacitor connected between the snubber and the primary side of the transformer and adapted to regulate a current flowing into the transformer.

Wherein the snubber has a capacitor connected to the drain terminal of the switch for charging and discharging a current supplied to the primary coil of the transformer; First and second diodes, one end of which is connected to the capacitor; And an inductor connected to the anode of the first diode.

A resonance capacitor connected to one end of the secondary coil of the transformer to generate a resonance current; And a resonance inductor connected to the other end of the secondary coil.

According to an aspect of the present invention, there is provided an isolated single-switch DC-DC converter including: a source power supply; A plurality of filter inductors for removing noise introduced into a voltage output from the source power supply; A plurality of transformers for causing the secondary coil to induce a current flowing into the primary coil; A plurality of switches for supplying or blocking current to the primary coil of the plurality of transformers; A plurality of snubbers disposed between the plurality of switches and the plurality of transformers to eliminate a surge voltage and implement a soft switching operation of the plurality of switches to eliminate losses occurring during switching; A plurality of resonance tanks connected to the secondary coils of the plurality of transformers to generate a resonance current; A plurality of rectifying units for rectifying, smoothing, and outputting a voltage output through the plurality of resonance tanks; And a control unit for controlling a switching operation of the plurality of switches,

Wherein a plurality of filter inductors and a plurality of switches which are the primary side of the plurality of transformers are formed in parallel and a plurality of rectifying sections that are the secondary side of the plurality of transformers are connected in series to increase the voltage to a high voltage.

According to an aspect of the present invention, there is provided an isolated single-switch DC-DC converter including: a source power supply; A plurality of filter inductors for removing noise introduced into a voltage output from the source power supply; A plurality of transformers for causing the secondary coil to induce a current flowing into the primary coil; A plurality of switches for supplying or blocking current to the primary coil of the plurality of transformers; A plurality of snubbers disposed between the plurality of switches and the plurality of transformers to eliminate a surge voltage and implement a soft switching operation of the plurality of switches to eliminate losses occurring during switching; A plurality of resonance tanks connected to the secondary coils of the plurality of transformers to generate a resonance current; A plurality of rectifying units for rectifying, smoothing, and outputting a voltage output through the plurality of resonance tanks; And a control unit for controlling a switching operation of the plurality of switches,

Wherein a plurality of filter inductors and a plurality of switches which are the primary side of the plurality of transformers are formed in parallel and a plurality of rectifying sections which are the secondary side of the plurality of transformers are arranged in parallel to increase the power by a large power.

According to the present invention, the use of a single switch not only simplifies the configuration of the converter but also reduces the implementation cost of the converter.

Further, according to the present invention, soft switching (ZCS) turn-off, Z-current switching and Z-voltage switching (ZVS) of all the devices are performed using a resonance tank and a lossless snubber. Turn-off), it is possible to minimize the loss occurring in switching, thereby achieving high efficiency and increasing power density.

Also, according to the present invention, there is an advantage that the magnetizing current of the transformer is small and the volume of the transformer core can be reduced.

1 is a circuit diagram of an insulation type single-switch DC-DC converter according to a preferred embodiment of the present invention,
FIG. 2 is an operational waveform diagram of the insulated single-switch DC-DC converter of FIG. 1,
3 is an operational principle diagram of the insulated single-switch DC-DC converter of Fig. 1, Fig.
4A to 4C are operation waveforms according to duty according to the present invention,
5 is a circuit diagram showing another embodiment of a DC-DC converter in which an insulation type single-switch DC-DC converter of the present invention is extended for high boosting,
FIG. 6 is an operational waveform diagram of the DC-DC converter of FIG. 5,
7 is a circuit diagram showing another embodiment of a DC-DC converter in which an insulated single-switch DC-DC converter of the present invention is extended for large power.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an isolated single-switch DC-DC converter according to a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of an isolated single-switch DC-DC converter according to a preferred embodiment of the present invention, which includes a source voltage Vi, a filter inductor Li, a switch S1, a snubber 10, a clamp capacitor Cc A transformer T, a resonance tank 20, a rectifying unit 30, and a control unit 40.

The filter inductor Li serves to remove noise introduced into the voltage output from the source power source Vi.

The transformer T serves to induce a current flowing into the primary coil as a secondary coil, and it is preferable that the primary coil and the secondary coil are implemented at a ratio of 1: n.

The switch S1 serves to supply or cut off a current to the primary coil of the transformer T and is preferably implemented as a MOSFET or an insulated gate bipolar mode transistor (IGBT).

The snubber 10 is disposed between the switch S1 and the transformer T to remove a surge voltage and implement a soft switching operation of the switch S1 to eliminate losses occurring during switching . The snubber 10 includes a capacitor Cs connected to the drain terminal D of the switch S1 for charging and discharging a current supplied to the primary coil of the transformer T; A first diode Ds1 and a second diode Ds2, one end of which is connected to the capacitor Cs; And an inductor Ls connected to the anode of the first diode Ds1.

The resonance tank 20 is connected to a secondary coil of the transformer T to generate a resonance current. The resonance tank 20 includes a resonance capacitor Cr connected to one end of a secondary coil of the transformer T to generate a resonance current; And a resonant inductor Lr connected to the other end of the secondary coil.

The rectifying unit 30 rectifies, smoothes and outputs the voltage output through the resonance tank 20. The rectifying unit 30 includes a first diode D1 having an anode connected to an output terminal of the resonant inductor Lr; A second diode D2 connected between the output end of the resonant inductor Lr and the anode of the first diode D1; And a smoothing capacitor (Co) connected to the cathode of the first diode (D1).

The clamp capacitor Cc is connected between the snubber 10 and the primary side of the transformer T and regulates a current flowing into the transformer T. [

The controller 40 controls the switching operation of the switch S1 using the PWM control signal according to the duty to control the output voltage.

The operation of the insulation type single-switch DC-DC converter according to the present invention will be described in detail with reference to FIGS. 1 to 4. FIG.

First, the insulation-type single-switch DC-DC converter according to the present invention includes nine modes (Mode 1 (V)) as shown in FIG. 3 during a cycle from the first turn- To Mode 9).

The switch S1 is turned on and the inductor Ls and the capacitor Cs of the snubber 10 start to resonate in the period between t0 and t1 of Fig. (-NVcc) + Vcr, min-Vo (-nVcc)) is induced in the inductor Lr of the resonance tank 20 connected to the secondary side of the transformer T, Voltage is applied and the current iLr of the resonance inductor Lr decreases at a constant slope. The current iD1 of the first diode D1 of the rectifying section 30 is also reduced at the same slope, and the zero current switching (ZCS) turn-off is performed. When the current iLr of the resonant inductor Lr becomes 0, the mode 2 is selected as the next mode.

Next, the current iLr of the resonance inductor Lr of the resonance tank 20 becomes 0 while the current direction changes and the resonance inductor Lr and the resonance capacitor Lr change in the period between t1 and t2 in Fig. (Cr), a resonance circuit is formed. Then, when the voltage Vcs of the capacitor Cs of the snubber 10 becomes -Vcc, the next mode is Mode3.

2, the second diode Ds2 of the snubber 10 is turned on and the inductor Ls and the capacitor Cs of the snubber 10 are resonantly connected to each other in the period between t2 and t3 of FIG. Lt; / RTI > At this time, a voltage of -Vcc is applied to the inductor Ls of the snubber 10 so that the current iLs of the inductor Ls decreases to a predetermined slope. When the current iLs of the inductor Ls of the snubber 10 becomes zero, Mode4 becomes the next mode.

2 and Fig. 3, the resonance of the resonance inductor Lr and the resonance capacitor cs of the resonance tank 20 is terminated and the second diode D2 is turned off The next mode is Mode5.

2, the sum of the input current and the magnetizing current of the transformer T flows in the switch S1, and when the switch S1 is turned off, the mode is Mode6, which is the next mode .

Next, the switch S1 is turned off in the period between t5 and t6 of FIG. 2 and the mode 6, and the sum of the input current and the magnetizing current flows to the capacitor Cs of the snubber 10, When the voltage Vcs of the capacitor Cs of the nubber 10 becomes equal to (Vo - Vcr, min) / n, Mode7 becomes the next mode.

The first diode D1 of the rectifying unit 30 is turned on and the resonance inductor Lr of the resonance tank 20 and the snubber 10 of the resonance tank 20 are turned on in a period between t6 and t7 of FIG. The capacitor Cs starts resonance. Then, when the current iLr of the resonant inductor Lr becomes equal to (Ii + Ilm) / n, the resonance is ended and Mode 8, which is the next mode, is obtained.

In addition, the first diode Ds1 of the snubber 10 is turned on in the period between the periods t7 and t8 of FIG. 2 and FIG. 3 of Mode 8, and the inductor Ls and the capacitor Cs start to resonate. The voltage Vcr of the resonant capacitor Cr of the resonance tank 20 is reduced to a predetermined slope and becomes Mode9 when the resonance of the inductor Ls and the capacitor Cs of the snubber 10 is completed.

Finally, a current of (Ii + Ilm) / n flows in the resonance capacitor Cr of the resonance tank 20 in the period between t8 and t9 in FIG. 2, which is mode 9 and the voltage Vcr of the resonance capacitor Cr becomes a constant slope And becomes the first mode which is the next mode when the switch S1 is turned on.

As described above, the isolated single-switch DC-DC converter of the present invention achieves the zero current switching turn-off of the diode and the zero current switching turn-on / zero voltage switching turn-off of the diode in all regions, Using a lossless snubber, the switching losses are very small. In addition, unlike the conventional single switch converter, since the upper limit and the upper limit of the transformer are both used, the volume of the core can be reduced.

As described above, the insulation type single-switch DC-DC converter of the present invention can perform three operations according to the operation duty. That is, the above resonance region as shown in FIG. 4A in which the duty D Ts is smaller than 0.5 占 1 r1 is a resonance region as shown in Fig. 4b in which the switch turn-off current and the di / dt of the diode are somewhat larger and the duty D 占 Ts s is 0.5 占 1 r1 Region and duty D · Ts> 0.5 · Tr1 In the below resonance region as shown in FIG. 4c, the switch turn-off current and diode di / dt are small. Therefore, it is preferable to operate in the resonance region or the below resonance region in the main operation region. Here, Ts is the switching period, and Tr1 is the resonance period of the resonant inductor Lr and the resonant capacitor Cr.

5 shows a structure in which the filter inductor and the switch on the input side are connected in parallel and the rectifying part on the output side is connected in series with respect to the transformer T based on the insulation type single-switch DC-DC converter as shown in FIG. . Here, a snubber, a 1: n transformer, and a resonance inductor Lr1, which are made up of the source power source Vi, the filter inductor L1, the switch S1, the capacitor Csn1 and two diodes DsnL1 and DsnU1 and the inductor Lsn, And a resonance capacitor consisting of a resonance capacitor Cr1 and two diodes D _U1 and D _L1 and a capacitor Co1 constitute an insulation type single switch DC-DC converter as shown in Fig. A snubber, a 1: n transformer, and a resonant inductor Lrn, which are made up of a source power source Vi, a filter inductor Lp, a switch Sp, a capacitor CsnP and two diodes DsnLp and DsnUp and an inductor Lsn, And the resonance capacitor made up of the resonant capacitor Crn and two diodes D _UN 3 and D _LN and the capacitor Co 2 constitute another insulation type single switch DC-DC converter as shown in Fig. Where N is the number of diode legs connected in series and P is the number of input-side switches and filter inductors connected in parallel. In order to increase the step-up ratio, the number of series-connected output-side voltage doublers (N) is increased. However, since the voltage rating of each device is small, Do. In order to increase the power capacity, it is advantageous to increase the number of filter inductors and switches connected to each input side. In this case, the number of elements increases, but the power rating of each element becomes small, which is advantageous when large power is required . Such a converter can select an element that is easy to price and supply by appropriately selecting the number of input parallel lines (P) and the number of output serial lines (N) in a given design specification.

Also, interleaving can be applied in parallel expansion to reduce the volume of the input / output passive elements.

FIG. 6 is a waveform diagram showing another embodiment of the isolated single-switch DC-DC converter shown in FIG. The plurality of switches S1 and S2 operate with the same duty, and each switch gives a 180 DEG phase difference for interleaving, and controls the output voltage by adjusting the duty ratio. These DC-DC converters have resonance due to lossless snubber and resonance tank, but they have different current loops and are not affected by each other. The switches S1 and S2 turn on the zero current switching by the current slope of the resonant inductor Lr of the resonant tank and turn off the zero voltage switching by the voltage slope of the capacitor Csni of the snubber. In addition, the diodes D2 and D4 of the rectifying part are formed resonance between the resonant inductor Lr and the resonant capacitor Cr to achieve the zero current switching turn-off.

7 shows a structure in which the filter inductor and the switch on the input side are connected in parallel and the rectifying part on the output side is connected in parallel based on the transformer T based on the insulation type single-switch DC-DC converter as shown in Fig. 1 . Here, a snubber, a 1: n transformer, and a resonance inductor Lr1, which are made up of the source power source Vi, the filter inductor L1, the switch S1, the capacitor Csn1 and two diodes DsnL1 and DsnU1 and the inductor Lsn, A resonance tank made up of a resonance capacitor Cr1 and a resonance capacitor Cr1 and two diodes D _U1 and D _L1 and a capacitor Co constitute an insulation type single switch DC-DC converter as shown in Fig. A snubber, a 1: n transformer, and a resonant inductor Lrp, which are composed of a source power source Vi, a filter inductor Lp, a switch Sp, a capacitor Csnp and two diodes DsnLp and DsnUp and an inductor Lsn, And a resonance capacitor consisting of a resonance capacitor Crp and two diodes D _up and D _Lp and a capacitor Co constitute another insulation type single switch DC-DC converter as shown in Fig. Where P is the number of input side switches and filter inductors connected in parallel, and the number of output side diodes connected in parallel. If you want to increase the power capacity, you can increase the number of filter inductors and switches connected to each input side. However, since the power rating of each device is small, it is advantageous when large power is required. Such a converter can select an easy-to-supply and easy-to-supply device by appropriately selecting the number of inputs parallel (P) and the number of output parallel (P) in a given design specification, thus enabling optimum design.

Although the present invention has been described in detail with reference to the above embodiments, it is needless to say that the present invention is not limited to the above-described embodiments, and various modifications may be made without departing from the spirit of the present invention.

The present invention is applied to a high-voltage insulated single-switch DC-DC converter. In particular, the present invention is effectively applied to a DC-DC converter that boosts an input DC voltage to a high boost ratio or boosts an input DC voltage to a high power.

Li: filter inductor
S1: Switch
T: Transformer
10: Snubber
20: resonance tank
30: rectification part
40:

Claims (11)

Source power;
A filter inductor for eliminating noise introduced into a voltage output from the source power supply;
A transformer for inducing a current flowing into the primary coil into a secondary coil;
A switch for supplying or blocking a current to the primary coil of the transformer;
A snubber that is disposed between the switch and the transformer to remove a surge voltage and implement a soft switching operation of the switch to eliminate losses occurring during switching;
A resonance tank connected to a secondary coil of the transformer to generate a resonance current;
A rectifying unit for rectifying, smoothing and outputting a voltage output through the resonance tank; And
And a control unit for controlling a switching operation of the switch,
A resonance capacitor connected to one end of a secondary coil of the transformer to generate a resonance current; And a resonance inductor connected to the other end of the secondary coil,
A capacitor connected to the drain terminal of the switch for charging and discharging a current supplied to the primary coil of the transformer; First and second diodes, one end of which is connected to the capacitor; And an inductor coupled to an anode of the first diode,
Wherein the resonant inductor of the resonant tank performs a zero current switching turn-on of the diode and the switch with a current slope, and the zero voltage switching turn-off of the switch is performed by a voltage slope of the capacitor included in the snubber. Single - switch DC - DC converter.
The isolation type single-switch DC-DC converter according to claim 1, wherein the switch is implemented by at least one of a MOSFET (MOS-FET) and an IGBT (Insulated Gate Bipolar mode transistor).
The isolation type single-switch DC-DC converter according to claim 1, further comprising a clamp capacitor connected between the snubber and a primary side of the transformer, for controlling a current flowing into the transformer.
delete delete Source power; A plurality of filter inductors for removing noise introduced into a voltage output from the source power supply; A plurality of transformers for causing the secondary coil to induce a current flowing into the primary coil; A plurality of switches for supplying or blocking current to the primary coil of the plurality of transformers; A plurality of snubbers disposed between the plurality of switches and the plurality of transformers to eliminate a surge voltage and implement a soft switching operation of the plurality of switches to eliminate losses occurring during switching; A plurality of resonance tanks connected to the secondary coils of the plurality of transformers to generate a resonance current; A plurality of rectifying units for rectifying, smoothing, and outputting a voltage output through the plurality of resonance tanks; And a control unit for controlling a switching operation of the plurality of switches,
Wherein a plurality of filter inductors and a plurality of switches which are the primary side of the plurality of transformers are formed in parallel and a plurality of rectifying sections that are the secondary side of the plurality of transformers are connected in series,
A resonance capacitor connected to one end of a secondary coil of the transformer to generate a resonance current; And a resonance inductor connected to the other end of the secondary coil,
A capacitor connected to the drain terminal of the switch for charging and discharging a current supplied to the primary coil of the transformer; First and second diodes, one end of which is connected to the capacitor; And an inductor coupled to an anode of the first diode,
Wherein the resonant inductor of the resonant tank performs a zero current switching turn-on of the diode and the switch with a current slope, and the zero voltage switching turn-off of the switch is performed by a voltage slope of the capacitor included in the snubber. Single - switch DC - DC converter.
The isolation type single-switch DC-DC converter according to claim 6, wherein the step-up ratio is varied by increasing or decreasing the number of the plurality of rectifying sections that are the secondary side of the plurality of transformers.
The isolation type single-switch DC-DC converter according to claim 6, wherein power is varied by increasing or decreasing the number of filter inductors and a plurality of switches, which are the primary side of the plurality of transformers.
Source power; A plurality of filter inductors for removing noise introduced into a voltage output from the source power supply; A plurality of transformers for causing the secondary coil to induce a current flowing into the primary coil; A plurality of switches for supplying or blocking current to the primary coil of the plurality of transformers; A plurality of snubbers disposed between the plurality of switches and the plurality of transformers to eliminate a surge voltage and implement a soft switching operation of the plurality of switches to eliminate losses occurring during switching; A plurality of resonance tanks connected to the secondary coils of the plurality of transformers to generate a resonance current; A plurality of rectifying units for rectifying, smoothing, and outputting a voltage output through the plurality of resonance tanks; And a control unit for controlling a switching operation of the plurality of switches,
Wherein a plurality of filter inductors and a plurality of switches which are the primary side of the plurality of transformers are formed in parallel and a plurality of rectifying portions that are the secondary side of the plurality of transformers are formed in parallel,
A resonance capacitor connected to one end of a secondary coil of the transformer to generate a resonance current; And a resonance inductor connected to the other end of the secondary coil,
A capacitor connected to the drain terminal of the switch for charging and discharging a current supplied to the primary coil of the transformer; First and second diodes, one end of which is connected to the capacitor; And an inductor coupled to an anode of the first diode,
Wherein the resonant inductor of the resonant tank performs a zero current switching turn-on of the diode and the switch with a current slope, and the zero voltage switching turn-off of the switch is performed by a voltage slope of the capacitor included in the snubber. Single - switch DC - DC converter.
The isolated single-switch DC-DC converter according to claim 9, wherein the power is varied by increasing or decreasing the number of the plurality of rectifying sections that are the secondary sides of the plurality of transformers.
10. The isolated single-switch DC-DC converter according to claim 9, wherein power is varied by increasing or decreasing the number of filter inductors and a plurality of switches, which are the primary sides of the plurality of transformers.

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