KR20210063980A - Soft switching converter - Google Patents

Abstract

According to the present technology, a soft switching converter is disclosed. According to a specific embodiment of the present technology, by applying a soft switching method of a soft switching converter equipped with a serial input stage and a parallel output stage, the voltage rating of a transformer primary switching element can be determined to be half that of input power, current rating can be reduced by interleaving DC blocking capacitors, and the number of capacitors can be reduced and by designing a ZVS current of a switch by using the resonance of a leakage inductor and a DC blocking capacitor, a ZVS turn-on operation of the switch is possible regardless of input voltage and load changes so as to reduce the switching loss of the switch.

Description

Soft Switching Converter {SOFT SWITCHING CONVERTER}

The present invention relates to a soft switching converter, and more particularly, in a soft switching converter having a series input terminal and a parallel output terminal, the voltage rating of the switch of the soft switching converter can be reduced to half that of the input power, and connected to the secondary side of the transformer The present invention relates to a technology capable of reducing a current rating of a capacitor by interleaving the capacitor and reducing switching loss by using resonance.

Low-voltage DC-DC Converters (LDCs) used in eco-friendly vehicles such as Electric Vehicles (EVs) and Hybrid Electric Vehicles (HEVs) provide power from high-voltage batteries to in-vehicle electronic systems. It is an important part that charges the low-voltage auxiliary battery that supplies

In order to shorten the charging time of an electric vehicle and extend the mileage according to a single charge, the need for increasing the capacity of the battery is increasing.

Recently, electric vehicles with 800V battery packs have been released, and accordingly, the need for 800V/14V LDC topology research is emerging.

In response to this need, the most commonly used topology for 400V/14V LDCs for electric vehicles equipped with 400V battery packs is a Phase Shift Full-bridge converter that can achieve ZVS (Zero Voltage Switch) turn-on without additional circuitry. Bridge, PSFB).

However, when PSFB is applied to the LDC for electric vehicles equipped with an 800V battery pack, the voltage rating of the switch becomes 800V, which is the input voltage, so a switch with a voltage rating of 1000V or higher must be used, and it is difficult to select an appropriate MOSFET.

In general PSFB, soft switching may fail at light load or soft switching may fail even at high load as the input voltage increases. In addition, a large-capacity DC blocking capacitor to ensure the offset of the magnetizing current of the transformer is 0 has reached the limit of being installed at each end of the transformer.

Accordingly, the present applicant proposes a soft switching converter having a low switch voltage rating and a wide input voltage range.

According to the present invention, in a soft switching converter having a series input terminal and a parallel output terminal, the voltage rating of a plurality of switches of the soft switching converter can be reduced to half of the input power by connecting the primary side switch legs in series, and connected to the secondary side of the transformer An object of the present invention is to provide a soft switching converter capable of reducing the current rating of the capacitor by interleaving the capacitor and reducing the switching loss of a plurality of switches by using resonance.

According to an aspect according to an embodiment, the soft switching converter,

a converter connected in series to both the input and output terminals of the output power to convert the DC input power into the AC type using a soft switching method; a transformer provided with at least one transformer respectively connected to an output terminal of the converter; It is characterized in that it comprises a rectifier for rectifying the output current of the transformer in the form of direct current to the load side.

Preferably, the converter is provided with a plurality of switches S1 to S4 of the half-bridge, and may be configured to perform a 180 degree phase shift with respect to the switches S1 and S2 and the switches S3 and S4 and perform asymmetric and complementary switching operation.

Preferably, the transformer

_{a transformer T1 in which a primary coil is wound between the output terminal of the leakage inductor L k1} and the leakage inductor L _k1 connected to the output terminal of the switch S1 of the converter connected to the input terminal of the input power and the output terminal of the switch S2 connected in series with the switch S1; _{and a leakage inductor L k2} connected to the output terminal of the switch S3 connected in series to the output terminal of the switch S2 and A transformer T2 in which a primary coil is wound between the output terminal of the switch S4 connected in series between the output terminal of the switch S3 and the output terminal of the input power may be provided as a transformer T2.

Preferably, the rectifier includes a capacitor Cr interleaved at the output terminals of the transformer T1 and the transformer T2; and diodes D1 and D2 connected between the output terminal of each capacitor Cr and the input terminal of the transformer T1 and respectively connected to the input terminal of the transformer T2.

Preferably, the soft switching converter may further include a filter unit for removing a noise component with respect to the output voltage of the rectifier.

According to an embodiment, by interleaving the dc blocking capacitor and applying the soft switching method of the soft switching converter having a series input terminal and a parallel output terminal, the voltage rating of the switching element can be determined as half of the input power, and the secondary winding of the transformer It is possible to reduce the current rating of the capacitor, and by interleaving the capacitor Cr, the current rating of the capacitor can be reduced, and the number of capacitors can be reduced.

In addition, according to an embodiment, ZCS turn-off design of the diode element of the switch is possible using the resonance of the leakage inductor and the DC blocking capacitor, and the ZVS turn-on operation of the switch is possible according to the input voltage and load variation, so the switching loss of the switch can reduce

The following drawings attached to this specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the detailed description of the present invention to be described later, so the present invention is a matter described in such drawings should not be construed as being limited only to
1 is a conceptual diagram of a soft switching converter according to an embodiment.
2 to 7 are diagrams illustrating an operation process of a soft switching converter according to an exemplary embodiment.
8 is a waveform diagram illustrating a current of each switch according to a load change according to an exemplary embodiment.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art may easily implement the present invention. However, the present invention may be implemented in various different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part "includes" a certain component, it means that other components may be further included, rather than excluding other components, unless otherwise stated. In addition, terms such as “…unit”, “…group”, “…module”, etc. described in the specification mean a unit that processes at least one function or operation, which is implemented by hardware or software or a combination of hardware and software. can be

In one embodiment, the current rating of the switch of the converter can be reduced by interleaving the dc blocking capacitor and applying the soft switching method of the converter, and the switch of the converter is ZVS (Zero Voltage Switch) regardless of a wide input voltage and load range By being turned on, it is possible to increase the efficiency by reducing the switching loss, and it is possible to remove the offset of the magnetizing current by performing DC blocking.

Hereinafter, the present invention will be described in detail by describing preferred embodiments of the present invention with reference to the accompanying drawings.

1 is a diagram showing the configuration of a soft switching converter to which an embodiment is applied, and FIGS. 2 to 7 are diagrams showing an operation process for each mode of the soft switching converter shown in FIG. 1 .

1 to 7 , the soft switching converter to which an embodiment is applied may include at least one of the half-bridge converter 100 , the transformer 200 , the rectifier 300 , and the filter unit 400 . .

Here, the half-bridge converter 100 is connected in series to both ends of the capacitors C1 and C2 respectively connected between the input terminal and the output terminal of the input power Vin, the switches S1 and S2 connected in series to both ends of the capacitor C1, and the capacitor C2. and switches S3 and S4. Here, each of the switches S1 to S4 may be provided as a switching element and a diode element, and only related components are shown.

Here, the switches S1 and S2 and the switches S3 and S4 of the half-bridge converter 100 each have a phase difference of 180 degrees and perform asymmetric and complementary switching operation.

Therefore, regardless of input voltage and load change, switches S1 to S4 operate in ZVS (Zero Voltage Switching) turned-on state, and the potential difference across switches S1 to S4 is determined to be half of the input voltage Vin, so each of capacitors C1 and C2 The potential difference between both ends satisfies the input power supply Vin/2.

Therefore, since the turn-off switching loss of the switch is reduced, even at a high input voltage of 800V or more, the switches S1 to S4 can use a 600V Si MOSFET.

The transforming unit 200 may be provided to the primary coil is wound between the leakage inductor L _k1 and _k1 leakage inductor L connected to the output terminal an output terminal of the switch S1 and switch S2 output transformer T1. In addition, the transformer 200 is a leakage inductor L _k2 connected to the output terminal of the switch S3 and It may further include a transformer T2 in which the primary side coil is wound between the output terminal of the switch S4.

And the rectifying unit 300 is connected to the secondary side of the transformer 200, the rectifying unit 300 is a capacitor Cr connected between one end of each transformer T1 and the other end of the transformer T2 and the output end of the load load and each of the transformer T1, Diodes D1 and D2 connected to each of the output terminals of T2 may be provided. Accordingly, the DC component included in the current of the transformers T1 and T2 is blocked by the capacitor Cr. That is, as the capacitor Cr is interleaved on the secondary sides of the transformers T1 and T2, the number of capacitors can be reduced, the current rating of the switch can be reduced, and the offset of the magnetizing current of the transformer 200 can be removed.

Then, the filter unit 400 is connected to the output terminal of the rectifier 200 to one end of each transformer T1 and the other end of the transformer T2, and the filter unit 400 is provided with coils L1, L2 and a capacitor Cout.

That is, coil L1. Each of L2 is connected to one end of the transformer T1 and the other end of the transformer T2, and the capacitor Cout is connected to both ends of the load. Accordingly, the noise component included in the voltage of the rectifying unit 300 is removed based on the filter unit 400 .

은 부하 전압

과 동일하고, 캐패시터 Cr의 전류

은 정류부(200)의 다이오드 D1, D2의 전류

,

의 차로 나타낼 수 있다. Accordingly, the voltage of the capacitor Cr of the rectifier for DC blocking

silver load voltage

equal to and the current of the capacitor Cr

Currents of diodes D1 and D2 of the silver rectifier 200

,

can be expressed as the difference of

Accordingly, in one embodiment, the voltage rating of the primary side switch of the transformer can be determined as half of the input power by interleaving the dc blocking capacitor and applying the soft switching method of the soft switching converter provided with the serial input terminal and the parallel output terminal, and the secondary side of the transformer The current rating of the winding may be reduced, and the current rating of the capacitor may be reduced by interleaving the capacitor Cr, and the number of capacitors may be reduced.

In addition, in one embodiment _{, ZCS turn-off design of the diode element of the switch is possible using the resonance of the leakage inductors L k1} , L _k2 and the DC blocking capacitor Cr, and the ZVS turn-on operation of the switches S1 to S4 according to the input voltage and load change Therefore, it is possible to reduce the switching loss of the switch.

Hereinafter, an operation process for the soft switching converter will be described with reference to FIGS. 2 to 7 .

First, as shown in (a) of FIG. 2, the switches S1 to S3 supplied from the outside at the time before the initial to (deadtime period) are maintained in the off state, and the diode element of the switch S1 is in the on state. is maintained, and the diodes D1 and D2 of the rectifying unit 300 are maintained in an on state. Accordingly, the voltage of the diode D1 is linearly decreased while the voltage of the diode D2 of the rectifier is linearly increased.

은

으로 증가된 다음 유지되고, 변압기 T1의 2차측 전압

은 음의

값을 가진다. 여기서,

는 스위치 S1의 게이트 신호의 PWM 듀티이다. That is, as shown in (b), the voltage of the _{leakage inductor L K1}

silver

is increased and then held, the voltage on the secondary side of transformer T1

is negative

have a value here,

is the PWM duty of the gate signal of switch S1.

의 크기는 감소하나 기울기는

이다. Also, the current in the leakage inductor L _K1

decreases in size, but the slope of

to be.

은 선형적으로 증가되고 스위치 S1의 전압

은 0으로 유지되며, 스위치 S2에 흐르는 전류

는 0으로 유지되고 스위치 S4의 양단 간의 전위차

는

으로 유지된다. 이에 캐패시터 C2의 전압은

이다. Also, the current flowing through the switch S1

increases linearly and the voltage on switch S1

is held at zero, and the current flowing through switch S2

is held at zero and the potential difference between the ends of switch S4

Is

is maintained as Therefore, the voltage across capacitor C2 is

to be.

은 서서히 감소되는 반면 정류부(200)의 다이오드 D2의 전류

는 선형적으로 증가된다.And the current of the diode D1 of the rectifying unit 300

is gradually decreased while the current of the diode D2 of the rectifier 200

is increased linearly.

3 is a diagram showing a circuit diagram and a waveform diagram of mode 2 in the period of time t0 to t1. As shown in (a) (b) of FIG. 3, at time t0, the switch S1 operates in the ZVS turn-on state, and the switch S4 is kept on.

의 크기는 감소 상태가 유지되나, 기울기

는 양의 값을 가지며, 누설 인덕터 L_K1의 전류

의 감소량이 0일 때 누설 인덕터 L_K1의 전류

의 방향이 반대로 흐르고, 이에 모드 3로 진행된다. Therefore, the current in the leakage inductor L _K1

The magnitude of is maintained in a decreasing state, but the slope

is a positive value, and the current in the _{leakage inductor L K1}

The current in the _{leakage inductor L K1} when the decrease of

flows in the opposite direction, and thus mode 3 proceeds.

은 필터부(400)의 코일 L1 전류와 동일할 때까지 증가된다. 이때 정류부(300)의 다이오드 D1은 ZCS(Zero Current Switching) 턴오프 상태로 전환된다. 이때 누설 인덕터 L_K1의 전류

는 하기 식 1로 나타낼 수 있다.4 is a diagram showing a circuit diagram and a waveform diagram of mode 3 in the period t1 to t2, and as shown in (a) (b) of FIG. 4, the current of the _{leakage inductor L K1}

is increased until it is equal to the coil L1 current of the filter unit 400 . At this time, the diode D1 of the rectifier 300 is switched to a ZCS (Zero Current Switching) turned off state. At this time, the current of the _{leakage inductor L K1}

can be represented by the following formula (1).

[Equation 1]

은 급격하게 감소되고, 변압기 T1의 2차측 전압

은 급격하게 증가된다.That is, as shown in (b), since _{the leakage current of the leakage inductor L K1} is excited by the transformer T1 and transferred to the secondary side, the leakage current of the leakage inductor L _K1 Voltage

is sharply reduced, and the secondary voltage of transformer T1

is increased rapidly.

은 선형적으로 증가되고 스위치 S1의 전압

은 0으로 유지되며, 스위치 S2에 흐르는 전류

는 0으로 유지되고 스위치 S4의 양단 간의 전위차

는

으로 유지된다. 이에 캐패시터 C2의 전압은

이다. Also, the current flowing through the switch S1

increases linearly and the voltage on switch S1

is held at zero, and the current flowing through switch S2

is held at zero and the potential difference between the ends of switch S4

Is

is maintained as Therefore, the voltage across capacitor C2 is

to be.

은 서서히 감소되어 시점 t3에서 ZCS 턴오프되고, 정류부(200)의 다이오드 D2의 전류

는 선형적으로 증가된다.And the current of the diode D1 of the rectifying unit 300

is gradually decreased and ZCS is turned off at time t3, and the current of the diode D2 of the rectifying unit 200 is

is increased linearly.

That is, when the diode D1 is switched to the ZCS turn-off state, it proceeds to mode 4.

은 하기 식 2에 도달될 때 까지 선형적으로 증가된다.5 is a diagram showing a circuit diagram and a waveform diagram of mode 4 in the period t2 to t3. As shown in FIG. 5(a)(b), the current of _{the leakage inductor L K1 increases}

is linearly increased until Equation 2 is reached.

[Equation 2]

은

로 유지된다.Also, the secondary voltage of transformer T1

silver

is maintained as

은 선형적으로 증가하다가 급격하게 0으로 감소하고, 스위치 S1의 전압

은 0으로 유지되며, 스위치 S2에 흐르는 전류

는 0으로 유지되다가 급격하게 감소되며, 스위치 S4의 양단 간의 전위차

는

으로 유지되고 시점 t3에서 급격하게 0으로 감소된다. 이에 캐패시터 C2의 전압은 0이다. Also, the current flowing through the switch S1

increases linearly and then abruptly decreases to 0, and the voltage of switch S1

is held at zero, and the current flowing through switch S2

is maintained at 0 and then rapidly decreased, and the potential difference between both ends of the switch S4

Is

, and abruptly decreases to 0 at time t3. Accordingly, the voltage of the capacitor C2 is zero.

가 식 2를 만족하는 시점 t3에서 하프브리지 컨버터(100)의 스위치 S1은 턴오프 상태로 스위칭되며, 이에 모드 5로 진행된다. Therefore, the current of the leakage inductor L _K1

At a time t3 that satisfies Equation 2, the switch S1 of the half-bridge converter 100 is switched to a turned-off state, thereby proceeding to mode 5.

는 스위치 S2의 다이오드 소자로 흐르고, 이에 누설 인덕터 L_K1와 캐패시터 Cr 간의 공진된다. 6 is a diagram showing a circuit diagram and a waveform diagram of mode 5 in the period t3 to t4. As shown in (a)(b), the current of the _{leakage inductor L K1}

flows into the diode element of the switch S2, thereby _{resonating between the leakage inductor L K1} and the capacitor Cr.

Accordingly, the equivalent circuit of the soft switching converter is as shown.

는 다음 식 3으로 나타낼 수 있다.According to this equivalent circuit, the current of the switch S2

can be expressed by Equation 3 below.

[Equation 3]

이고, D는 게이트 신호의 PWM 듀티이다.Here, the resonant frequency

and D is the PWM duty of the gate signal.

은

으로 유지되고, 변압기 T1의 2차측 전압

은 캐패시터 Cr의 전압

과 동일하고 감소되며, 또한, 누설 인덕터 L_K1의 전류

의 기울기는 감소된다. As shown in (b), the voltage of the _{leakage inductor L K1}

silver

is maintained, and the voltage on the secondary side of the transformer T1 is

the voltage on the silver capacitor Cr

is equal to and reduced, and also the current in the _{leakage inductor L K1}

slope is reduced.

은 0으로 유지되나 스위치 S1의 전압

은 0으로 유지되며, 스위치 S2에 흐르는 전류

는 선형적으로 증가되나 스위치 S4의 양단 간의 전위차

는

으로 유지된다. 이에 캐패시터 C2의 전압은

이다. Also, the current flowing through the switch S1

remains at zero, but the voltage on switch S1

is held at zero, and the current flowing through switch S2

is linearly increased, but the potential difference between both ends of switch S4

Is

is maintained as Therefore, the voltage across capacitor C2 is

to be.

및 다이오드 D2의 전류

는 선형적으로 증가됨을 알 수 있다.And the current of the diode D1 of the rectifying unit 300

and current in diode D2

It can be seen that increases linearly.

Then, when the switch S2 is switched to the ZVS turn-on state, it proceeds to the next mode 6 .

7 is a circuit diagram and waveform diagram of mode 6 in the period t4 to t5. Referring to FIGS. 7 (a) and (b), at time t4, the switch S2 is ZVS turned on, and the leakage inductor L _K 1 and the capacitor Resonance between Cr is maintained, and an equivalent circuit therefor is as shown.

의 크기는 증가하나 기울기

는 선형적으로 감소하고, 정류부(300)의 다이오드 D1의 전류

은 서서히 감소되는 반면 정류부(200)의 다이오드 D2의 전류

는 선형적으로 증가하다가 스위치 S3가 ZVS 턴온 상태로 동작되는 시점에서 선형적으로 감소하다가 0으로 유지된다. 그리고, 모드 6는 스위치 S2가 턴오프로 스위칭될 때까지 유지되며 이후 모드 1로 진행된다. Referring to (b), the current of the _{leakage inductor L K1}

increases in size but slopes

is linearly decreased, and the current of the diode D1 of the rectifying unit 300 is

is gradually decreased while the current of the diode D2 of the rectifier 200

increases linearly, decreases linearly when switch S3 is operated in the ZVS turn-on state, and remains at 0. Then, the mode 6 is maintained until the switch S2 is switched to turn off, and then proceeds to the mode 1.

Accordingly, in one embodiment, the voltage rating of the primary side switch of the transformer can be determined as half of the input power by interleaving the dc blocking capacitor and applying the soft switching method of the soft switching converter provided with the serial input terminal and the parallel output terminal, and the secondary side of the transformer The current rating of the winding may be reduced, and the current rating of the capacitor may be reduced by interleaving the capacitor Cr, and the number of capacitors may be reduced.

In addition, according to an embodiment, the ZVS current of the switch is designed using the resonance of the leakage inductor and the DC blocking capacitor, so that the ZVS turn-on operation of the switch is possible regardless of the input voltage and load variation, thereby reducing the switching loss of the switch.

8 is a waveform diagram showing the current flowing in the switches S1 to S4 according to each load change according to an embodiment. Referring to FIG. 8, an embodiment shows the ZVS turn-on regardless of the input voltage Vin and the load Vbat change. You can see what you achieve.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and it is easily changed by a person skilled in the art from the embodiment of the present invention to equivalent Including all changes to the extent recognized as

Claims (5)

a converter connected in series to both the input and output terminals of the input power to convert the DC input power into the AC type using a soft switching method;
a transformer provided with at least one transformer respectively connected to an output terminal of the converter; and
and a rectifier for rectifying the output current of the transformer in a DC form and transmitting the rectifier to the load. The method of claim 1, wherein the converter
A soft switching converter that is provided with a plurality of switches S1 to S4 of the half-bridge, and is provided to perform a 180 degree phase shift with respect to the switches S1 and S2 and the switches S3 and S4 and to perform asymmetrically complementary switching operation. According to claim 1, wherein the transformer,
_{a transformer T1 in which a primary coil is wound between the output terminal of the leakage inductor L k1} and the leakage inductor L _k1 connected to the output terminal of the switch S1 of the converter connected to the input terminal of the input power and the output terminal of the switch S2 connected in series with the switch S1; and
_{Leakage inductor L k2} connected to the output of switch S3 in series with the output of switch S2 and A soft switching converter comprising a transformer T2 in which a primary coil is wound between the output terminal of the switch S4 connected in series between the output terminal of the switch S3 and the output terminal of the input power. The method of claim 2, wherein the rectifying unit
a capacitor Cr interleaved at the output terminals of each of the transformers T1 and T2; and
A soft switching converter comprising diodes D1 and D2 connected between the output terminal of each capacitor Cr and the input terminal of the transformer T1 and each of the input terminals of the transformer T2. 4. The method of claim 3, wherein the soft switching converter
Soft switching converter, characterized in that it further comprises a filter for removing a noise component with respect to the output voltage of the rectifier.

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