KR20070006308A - Resonant ac/dc converter of a boost input type - Google Patents

Abstract

A resonant AC/DC converter of a boost input type is provided to conduct zero voltage switching by using resonance between leakage inductance and a resonance capacitor. A power factor improving circuit(10) has an input inductor and a first switch(S1) which are connected in serial-parallel with a rear end of a rectifying circuit. A clamping circuit(20) has a second switch and a clamping capacitor which are connected in serial-parallel with a rear end of the power factor improving circuit. A resonance circuit(30) has a leakage inductor and a resonance which are connected in serial-parallel with a rear end of the clamping circuit. A transformer(T) is installed to a rear end of the resonance circuit. A comparator compares an electric current output from a multiplier(60) with an electric current output from a first power line. A first drive circuit(80) controls opening/closing of the first switch, and a second drive circuit(90) controls opening/closing of the second switch.

Description

Resonant AC / DC Converter with Boost Input Method {RESONANT AC / DC CONVERTER OF A BOOST INPUT TYPE}

1 is a diagram illustrating IEC regulation values of general input current harmonic components,

2 is a graph showing the voltage, current and power of an ideal rectifier,

3 is a circuit diagram showing an active power factor improvement circuit according to the prior art,

4 is a control block diagram of an AC / DC converter according to the present invention;

5 is a theoretical waveform of each part of FIG. 4,

6A to 6F are circuit diagrams for explaining the current paths in each mode of FIG. 4;

7 is a graph illustrating an input / output voltage transfer ratio according to the present invention;

Figure 8 shows an equivalent circuit for the steady state analysis of the resonant circuit according to the present invention,

9 is a graph showing a change in output voltage according to the ratio of the present invention,

10 is a graph showing the power factor and efficiency of the AC / DC converter according to the present invention,

11 is a measurement waveform diagram of each part according to the present invention,

12 is an enlarged measurement waveform diagram of the switching instant of FIG. 11;

13 is a waveform diagram illustrating the voltage V _T and the resonant current ir of the transformer according to the present invention;

14 is a waveform diagram showing an input voltage and an input current according to the present invention.

* Explanation of symbols for the main parts of the drawings

10: power factor improvement circuit portion 20: clamping circuit portion

30: resonance circuit 50: error amplifier

60: multiplier 70: hysteresis comparator

80: first driving circuit portion 90: second driving circuit portion

BD: rectifier circuit S1: first switch means

S2: second switch means Lr: leakage inductor

Cr: resonant capacitor T: transformer

Ro: Load

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC / DC converter, and more particularly, to a resonant AC / DC converter of a boost input type that implements zero voltage switching by using resonance between a leakage inductor and a resonance capacitor of a transformer.

In general, a capacitor input rectifier circuit generates a narrow pulsed current because the rectifier circuit is conducted only for a short period near the maximum value of the AC input voltage.

Since such pulsed currents are simultaneously generated in each electronic device and added to the same phase, the pulsed current generates a voltage drop on the commercial power supply side and contains a large amount of harmonic components.

In response to this problem, IEC 1000-3-2 class D regulates the input power factor reduction caused by harmonic components for small electronic devices of 600 [W] or less.

In recent years, active power factor correction circuits for improving input power factor and suppressing harmonics have been simultaneously controlled such as power factor correction and secondary output of transformers, such as active clamp type flyback converters or asymmetric half bridge converters. A one-step active power factor correction circuit has been developed, and interest in this is increasing.

The limit of the input current according to IEC standard 1000-3-2 class D is shown in FIG.

The dashed line represents the IEC limit for the harmonic content of the input current, and the vertical line represents the harmonic content of the pulsed input current in the capacitor input rectifier circuit, indicating that the IEC limit is exceeded over the entire range. have.

As a countermeasure to prevent the power factor drop due to harmonic components of the input current, it is divided into a passive power factor improvement circuit and an active power factor improvement circuit.

Passive power factor correction circuit that reduces the size of low frequency high frequency components by adopting passive filter which combines inductor and capacitor is remarkable in terms of simple and economical structure, but the volume and weight are large and the effect of power factor improvement is not great.

On the other hand, an active power factor improvement circuit using a switch mode power supply has a disadvantage in that the circuit is complicated and the manufacturing cost increases as one or more control circuits are required. It is widely used as an input device such as an electronic ballast.

The active power factor improvement circuit is a circuit that improves the power factor by controlling the input current to follow the same shape as the input voltage. In other words, the power factor can be improved by removing the total harmonic components, which are components other than the fundamental wave components, in the input current.

The distortion of the waveform due to total harmonics is called total harmonic distortion (THD: Total Harmonics Distortion), and the relationship between the total harmonic distortion and the power factor of the circuit is shown in Equation 1 below.

Here, Irms is the effective value of the total current, and Irms (1) is the effective value of the fundamental wave current.

In particular, the relationship between the total harmonic distortion and the power factor in the case of a capacitor input rectifier can be simply expressed as Equation 2 below.

FIG. 2 shows a relationship between input voltage, current, and power when the harmonic component of the input current is completely removed, that is, when the power factor is 1 in the conventional active power factor improving circuit.

Referring to FIG. 2, the input power Pin has a frequency corresponding to twice the frequency of the AC input side power supply by multiplying the input voltage vin and the input current iin.

The active power factor improvement circuit is classified into a two-stage power factor improvement circuit in which two power converters are connected in series and a one-stage power factor improvement circuit composed of only one power converter.

3A and 3B are diagrams illustrating types of active power factor improving circuits.

3A is a two-stage active power factor improvement circuit that can maintain high efficiency over a wide input voltage range, but since the two converter circuits are directly connected, the circuit is complicated and the manufacturing cost increases, making it difficult to apply to low-cost power supply circuits. .

On the other hand, Figure 3b is a one-step active power factor improvement circuit to control the output voltage and the input power factor at the same time through a single power converter, not only can reduce the power conversion loss, but also because the manufacturing cost is economical.

Accordingly, an object of the present invention is to provide a boost input type resonant AC / DC converter which proposes a boost input type one-step active power factor improvement circuit using a current continuous mode pulse width modulation method.

Another object of the present invention is to reduce the switching loss through zero voltage switching using the resonance between the leakage inductor and the resonant capacitor of the transformer, a simple control circuit using a boost input type resonant AC / DC converter with a simple configuration To provide.

Technical means of the present invention for achieving the above object, in the resonant AC / DC converter for rectifying the input AC power through the rectifier circuit to improve the power factor to supply the DC power to the load: at the rear end of the rectifier circuit A power factor improving circuit unit in which the input inductor and the first switch means are installed in parallel to improve the power factor; A clamping circuit unit configured to limit a voltage change by installing a second switch means and a clamping capacitor in series at a rear end of the power factor improving circuit unit; A resonant circuit unit in which a leakage inductor and a resonant capacitor are installed in series and in parallel to implement a zero voltage at a rear end of the clamping circuit unit; A transformer installed at the rear end of the resonant circuit part and inductively converting the primary power to the secondary to supply the load; An error amplifier receiving and amplifying a voltage detected from an output side of the load and a predetermined reference voltage, respectively; A multiplier configured to receive and multiply the voltage output from the error amplifier by the voltage output from the first power line of the rectifier circuit; A comparator having hysteresis characteristics for comparing the current output from the multiplier with the current output from the second power line of the rectifier circuit, respectively, as non-inverting and inverting terminals; A first driving circuit unit receiving an output signal of the comparator and controlling opening and closing of the first switch means of the power factor improving circuit unit; And a second driving circuit unit which receives a signal in which the output signal of the comparator is inverted in phase and controls the opening and closing of the second switch means of the clamping circuit unit.

Specifically, the first switch means, the first internal diode embedded in parallel in its current path; And a first parasitic capacitor formed in parallel in the current path of the first switch means, wherein the second switch means comprises: a second internal diode built in parallel in its current path; And a second parasitic capacitor formed in parallel in the current path of the second switch means, the clamping capacitor being formed between the second switch means and the second power line to form an active clamp circuit together with the second switch means. It characterized in that it further comprises.

The resonant circuit unit may include a first leakage inductor, a second leakage inductor, and a resonance capacitor connected in series between a first power supply line and a second power supply line, respectively, and the transformer may have a primary side connected in parallel to the leakage inductor. coil; And a plurality of secondary side coils corresponding to the primary side coils and having a first output line, an intermediate tab, and a second output line.

In addition, a load is connected to a current path between the first output line and the intermediate tap of the secondary side coil, a first rectifying diode and an output inductor are connected in series between the first output line and the load, and the second output. A second rectifying diode is connected between the line and the output node of the first rectifying diode, characterized in that the output capacitor is connected in parallel with the load between the output node and the middle tap of the output inductor.

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

4 is a view illustrating a control configuration of an AC / DC converter according to the present invention, and includes a rectifier circuit BD, a power factor improvement circuit unit 10, a clamping circuit unit 20, a resonance circuit unit 30, a transformer T, and an error. The amplifier 50 includes a multiplier 60, a comparator 70, a first driving circuit unit 80, and a second driving circuit unit 90.

The rectifier circuit BD is composed of a bridge diode that receives an input AC power source Vin and converts it into a DC power source. The power factor improving circuit unit 10 has an input inductor Li and a rear end of the rectifier circuit BD. The first switch means (S1) is installed in series and parallel to improve the power factor of the DC power supply, the clamping circuit unit 20 is the second switch means (S2) and the clamping capacitor (C1) at the rear end of the power factor improvement circuit unit 10 ) Is installed in series to limit the voltage change, and the resonant circuit unit 30 has a leakage inductor (Lr) and a resonant capacitor (Cr) installed in series and parallel to implement zero voltage at the rear end of the clamping circuit unit (20). The transformer T is installed at the rear end of the resonant circuit unit 30, and is configured to inductively convert the primary power to the secondary to supply the load Ro.

In addition, the error amplifier 50 is configured to receive and amplify the voltage detected from the output side of the load Ro and the predetermined reference voltage V_ref, respectively, and the multiplier 60 outputs the voltage output from the error amplifier 50. And the voltage i_model output from the first power line of the rectifier circuit BD is multiplied, and the comparator 70 is formed of the current i_ref output from the multiplier 60 and the rectifier circuit BD. The Schmitt trigger has hysteresis characteristics for receiving and comparing currents i_real output from the second power line with non-inverting and inverting terminals, respectively, and the first driving circuit unit 80 provides an output signal of the comparator 70. And control the opening and closing of the first switch means (S1) of the power factor improving circuit unit 10, the second drive circuit unit 90 is the output signal of the comparator 70 is phase-inverted through the inverter 85 The second of the clamping circuit unit 20 receives a signal And it is configured to control the opening and closing of the location means (S2).

In addition, the first switch means (S1), the first internal diode (DS1) built in parallel in its current path, and the first parasitic capacitor (P1) formed in parallel in the current path of the first switch means (S1) ( CS1).

The second switch means S2 includes a second internal diode DS2 embedded in parallel in its current path, and a second parasitic capacitor CS2 formed in parallel in the current path of the second switch means S2. And a clamping capacitor (C1) formed between the second switch means (S2) and the second power line to form an active clamp circuit together with the second switch means (S2).

The resonant circuit unit 30 includes a first leakage inductor Lr, a second leakage inductor Lp, and a resonance capacitor Cr connected in series between the first power supply line and the second power supply line, respectively.

The transformer T corresponds to a primary coil N1 connected in parallel to the second leakage inductor Lp, and the primary coil N1, and includes a first output line, an intermediate tap, and a second output line. The branch is composed of a plurality of secondary coils N2 and N3, a load Ro is connected to a current path between the first output line and the intermediate tap of the secondary side first coil N2, and the first output. A first rectifying diode Do1 and an output inductor Lo are connected in series between a line and a load Ro, and a second rectifying diode (between the second output line and the output node of the first rectifying diode Do1). Do2) is connected, and the output capacitor Co is configured to be connected in parallel with the load Ro between the output node of the output inductor Lo and the intermediate tap.

That is, the power factor improving circuit portion 10 of the boost converter type is composed of an input inductor Li and a first switch means S1 on the input side, and the clamping circuit portion 20 includes a second switch means S2 and a clamping capacitor C1. It is composed of

The first and second internal diodes DS1 and DS2 connected in parallel to the first and second switch means S1 and S2, respectively, are diodes embedded in the respective switch means S1 and S2. The switch means S1, S2 have a component of each parasitic capacitor CS1, CS2.

The resonant circuit for realizing zero voltage of the first and second switch means (S1, S2) is composed of a second leakage inductance (Lr) and a resonant capacitor (Cr), if necessary, a second leakage inductor (Lp) Can be configured in addition.

During one period, the first and second switch means S1 and S2 are conducted at the ratio D and (1-D), respectively, and zero voltage switching is performed when both switch means S1 and S2 are turned on.

The voltage detected from the output side for output voltage control is amplified by the error amplifier 50 and multiplied by the input voltage through the multiplier 60 to become the reference current i_ref.

The gate driving signal of the first switching means S1 is obtained by comparing the reference current signal i_ref and the actual current i_real using the hysteresis comparator 70, and the gate driving signal of the second switching means S2 is obtained by comparing the first driving means with the first driving means S1. 1 is operated by receiving a waveform inverting the drive signal of the switch means S1. In this case, an appropriate dead time should be given to prevent dark short and zero voltage switching between the two signals.

In addition, the intrinsic resonance frequency between the first leakage inductor Lr and the resonance capacitor Cr provided at the front end of the transformer T may be expressed by Equation 3 below.

For the analysis of the converter proposed by the present invention is divided into six modes, the theoretical waveform of the main part for the current path and analysis for each mode is shown in Figs.

FIG. 5 is a waveform diagram illustrating theoretical waveforms of main parts of the circuit of FIG. 4, and FIGS. 6A to 6F are circuit diagrams illustrating a current path for each mode according to the present invention.

Mode 1 (t ₀ ≤t <t ₁ )

At t = t ₀ , both the first and second switch means S1 and S2 are turned off.

As shown in FIG. 6A, when the charging voltage of the first parasitic capacitor CS1 is discharged and lowers below the forward voltage drop of the first internal diode DS1, the first internal diode DS1 is turned on and the first leakage inductor is turned on. The resonant current ir between Lr and the resonant capacitor Cr is circulated through the first internal diode DS1, and both ends of the first switch means S1 are in a zero voltage state.

Since both ends of the first switch means S1 are in a zero voltage state during the period in which the first internal diode DS1 is conducted, the first switch means S1 is turned on at t ₀ ≤ t <t ₁ , thereby naturally Zero voltage switching takes place.

The current of the secondary side of the transformer T is transmitted to the load Ro through the first and second windings N2 and N3 and the first and second rectifying diodes DO1 and DO2 during the mode 1 mode.

Mode 2 (t ₁ ≤t <t ₂ )

Referring to FIG. 6B, the resonant current ir is reversed at t = t ₁ , and the current is1 of the first switch means S1 flows through the channel of the first switch means S1. The current on the secondary side of the transformer T is transferred to the load R ₀ side through the second winding N2 and the first rectifying diode DO1.

Mode 3 (t ₂ ≤t <t ₃ )

의 전압으로 충전되고 동시에

로 충전되어 있던 제 2 스위치수단(S2)의 제 2 기생커패시터(CS2)는 급속히 방전하게 된다.Referring to FIG. 6C, when the switch means S1 is turned off at t = t ₂ , the first parasitic capacitor CS1 of the first switch means S1

Charged at a voltage of

The second parasitic capacitor CS2 of the second switch means S2, which has been charged with, is rapidly discharged.

Mode 4 (t ₃ ≤t <t ₄ )

의 값까지 충전하게 된다.Referring to FIG. 6D, when t = t ₃ , when the charging voltage of the second parasitic capacitor CS2 is discharged and lowers below the forward voltage drop of the second internal diode DS2, the second internal diode DS2 is turned on. On and the resonant current (ir) flows through the second internal diode (DS2), the clamping capacitor (C1) by this current

To the value of.

Both ends of the second switch means S2 are in a zero voltage state during the period in which the second internal diode DS2 is turned on, so that the second switch means S2 is naturally turned on at t ₃ ≤ t <t ₄ . Voltage switching takes place.

The current of the secondary side of the transformer T is transferred to the load Ro through the plurality of windings N2 and N3 and two rectifying diodes DO1 and DO2 during the mode 4 mode.

Mode 5 (t ₄ ≤t <t ₅ )

Referring to FIG. 6E, at t = t ₄ , the resonant current ir is reversed and the current is2 of the second switch means S2 flows through the channel of the second switch means S2. The resonant current ir is reversed in direction, and current on the secondary side of the transformer T is transferred to the load Ro through the second winding N3 and the second rectifying diode DO2.

Mode 6 (t ₅ ≤t <t ₆ )

의 전압으로 충전됨과 동시에

으로 충전되어 있던 제 1 스위치수단(S1)의 제 1 기생커패시터(CS1)는 급속히 방전하게 됨으로써 한 주기가 끝난다.Referring to FIG. 6F, when the second switch means S2 is turned off at t = t ₅ , the second parasitic capacitor CS2 of the second switch means S2 is

While charging at a voltage of

The first parasitic capacitor CS1 of the first switch means S1, which has been charged by the battery, is rapidly discharged, thereby ending one cycle.

As shown in FIG. 4, the proposed converter includes a boost converter including an input inductor Li on the input side, a first switch means S1 and a clamping capacitor C1 as main switches, an auxiliary second switch means S2, and The power transmission unit consisting of a transformer (T) and a resonant capacitor (Cr) can be divided and analyzed.

When the ratio of the first switch means S1 is D, the voltage of the clamping capacitor C1, which is the DC link voltage of the boost converter, is expressed by Equation 4 below.

를 고려한 2차측 전압은 아래 수학식 5와 같다.And the turn ratio of the transformer T,

Considering the secondary voltage is as shown in Equation 5 below.

In an actual circuit, parasitic resistance components including winding resistances of the input inductor Li and the transformer T exist. If k is the influence of the primary parasitic resistance component, k is expressed by Equation 6 below.

Here, R is a load Ro side resistance component, and r is a synthetic parasitic resistance component on the primary side.

Therefore, the secondary voltage when considering this is as shown in Equation 7 below.

Based on this, the change in the output voltage with respect to the ratio D is shown as shown in FIG.

In FIG. 7, a dotted line is a voltage transfer ratio in an ideal case (N = 1) without considering the influence of resistance components including winding resistances of the input inductor Li and the transformer T, which is represented by a solid line. .

The proposed converter of boost type has a characteristic that the voltage of the DC link stage is increased due to the switching operation following the input voltage waveform during no load operation.

의 일정한 값이 된다고 가정할 경우 VDS1을 푸리에 급수로 전개하면 아래 수학식 8과 같다.For the steady state analysis of the proposed converter resonant circuit, the effect of the dead time between the two switch means (S1, S2) is ignored, and the voltage VDS1 between the drain and the source when the first switch means (S1) is off is relatively large. By clamping capacitor C1 having a value

Assuming a constant value of, VDS1 is expanded to Fourier series as shown in Equation 8 below.

이고,

이며,

이다.Where Davg is the mean value of the fertilization rate D,

ego,

Is,

to be.

가 직렬 공진주파수

에 근접하게 된다고 가정할 경우,

는 기본파 성분으로 근사화되어 다음 수학식 9와 같이 나타낼 수 있다.Switching frequency

Series Resonance Frequency

Assuming you are close to,

Is approximated to the fundamental wave component and can be expressed as Equation 9 below.

이다.here,

to be.

8 shows an equivalent circuit in which the equivalent resistance R of the circuit is added to obtain the resonance current ir in the steady state.

The impedance Z is obtained from the equivalent circuit, as shown in Equation 10 below.

이고,

이며,

이다. only,

ego,

Is,

to be.

은 다음 수학식 11과 같다.In addition, the resonance current at this time

Equation 11 is as follows.

Experimental Example

In order to verify the validity of the proposed converter, a prototype converter with input voltage AC 120V, output voltage DC 48V, and output current 5A was fabricated and tested.

9 shows the change of the output voltage according to the ratio of the proposed converter.

For steady-state DC analysis, the converter input voltage is DC 100V and the turn ratio N = 1/4 of the transformer T.

Where A is the ideal value without considering the parasitic resistance component, and B is the actual measured value.

As a result of the measurement, when compared to the section having a fertilization rate of 50% or less, the slope of the section having a fertilization rate of 50% or more is gently changed by the parasitic resistance component of the primary side, so it can be seen that it is not advantageous in terms of voltage transfer.

The power factor and efficiency in varying the load Ro of the converter proposed in the present invention are shown in FIG. 10.

In light load operation, the power factor and efficiency of the proposed converter are low.

However, high power factor and efficiency at maximum load range can be obtained at medium load. As a result, the maximum efficiency of 83% and the power factor of 99% were obtained.

FIG. 11 is a measurement waveform of each part in a normal operation state, and FIG. 12 is a waveform measured by enlarging a switching instant in the waveform of FIG. 11.

VGS1, VDS1, ir and iL on FIG. 11 represent the drive signal of the first switch means S1, the voltage between the drain source, the current and the current flowing through the input inductor Li, respectively.

At the turn-on moment in the left waveform diagram of FIG. 12, the current iS of the first switch means S1 flows through the first internal diode DS1, so that a zero voltage state is secured. It can be seen that zero voltage switching is achieved by turning on.

On the other hand, in the right waveform diagram of FIG. 12, the switching loss occurs because the current iS of the first switch means S1 and the voltage Vds1 of both ends of the first switch means S1 overlap each other. .

FIG. 13 shows the voltage VT and the resonance current ir applied to the primary coil N1 of the transformer T.

Here, since the resonant current (ir) has an asymmetrical shape due to the pulse width modulation but is bidirectional, it shows that the reverse current section may occur before the two switch means (S1, S2) are both turned on.

Figure 14 shows the AC input voltage and current applied to the converter, by showing that the input current perfectly follows the shape of the input voltage, it is possible to confirm the power factor improvement effect, a high power factor of 99% through the actual experiment Could get

While specific embodiments of the present invention have been described and illustrated above, it will be apparent that the present invention may be embodied in various modifications by those skilled in the art. Such modified embodiments should not be understood individually from the technical spirit or the prospect of the present invention, but should fall within the claims appended to the present invention.

Therefore, the present invention proposes a resonant AC / DC converter of a single stage boost input method, and the proposed converter implements zero voltage switching by using resonance between a leakage inductance and a resonance capacitor. The proposed converter can reduce switching loss through zero voltage switching using LC resonance, and it is a one-step type that simultaneously controls input power factor and output voltage. There is an advantage that high power factor can be obtained through modulation.

Claims (7)

In the resonant AC / DC converter which rectifies the input AC power through the rectifier circuit and improves the power factor to supply DC power to the load: A power factor improvement circuit unit in which an input inductor and a first switch means are installed in parallel in a rear end of the rectifier circuit to improve the power factor; A clamping circuit unit configured to limit a voltage change by installing a second switch means and a clamping capacitor in series at a rear end of the power factor improving circuit unit; A resonant circuit unit in which a leakage inductor and a resonant capacitor are installed in series and in parallel to implement a zero voltage at a rear end of the clamping circuit unit; A transformer installed at the rear end of the resonant circuit part and inductively converting the primary power to the secondary to supply the load; An error amplifier receiving and amplifying a voltage detected from an output side of the load and a predetermined reference voltage, respectively; A multiplier configured to receive and multiply the voltage output from the error amplifier by the voltage output from the first power line of the rectifier circuit; A comparator having hysteresis characteristics for comparing the current output from the multiplier with the current output from the second power line of the rectifier circuit, respectively, as non-inverting and inverting terminals; A first driving circuit unit receiving the output signal of the comparator and controlling opening and closing of the first switch means of the power factor improving circuit unit; And And a second driving circuit unit configured to receive an output signal of which the output signal of the comparator is inverted in phase to control the opening and closing of the second switch means of the clamping circuit unit. 2. The method according to claim 1, The first switch means includes a first internal diode built in parallel to its current path; And a first parasitic capacitor formed in parallel in the current path of the first switch means. The method according to claim 1 or 2, The second switch means may include a second internal diode built in parallel in its current path; And a second parasitic capacitor formed in parallel in the current path of the second switch means. The method according to claim 3, And a clamping capacitor formed between the second switch means and the second power supply line and constituting an active clamp circuit together with the second switch means. The method according to claim 1, The resonant circuit unit includes a boost input type resonant AC / DC converter, comprising a first leakage inductor, a second leakage inductor, and a resonance capacitor connected in series between the first power supply line and the second power supply line, respectively. The method according to claim 1, The transformer includes: a primary coil connected in parallel to the leakage inductor; And a plurality of secondary side coils corresponding to the primary side coils and having a first output line, an intermediate tap, and a second output line. The method according to claim 6, A load is connected to a current path between the first output line and the intermediate tap of the secondary coil, a first rectifying diode and an output inductor are connected in series between the first output line and the load, and the second output line The second rectifier diode is connected between the output node of the first rectifier diode, the output capacitor is connected between the output node and the intermediate tap of the output inductor in parallel with the load, resonant AC / DC type of the boost input method Converter.

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