KR20020074245A - High efficiency soft-switching AC-DC boost converter using coupled inductor and energy recovery circuit having power factor correction function - Google Patents

Abstract

PURPOSE: A high efficiency soft switching AC-DC booster converter is provided to significantly reduce electromagnetic interference by reducing stresses of blocking diode, while reducing harmonic distortion. CONSTITUTION: A high efficiency soft switching AC-DC booster converter comprises a booster inductor(Lb) for receiving a DC voltage through a primary coil, and which has a secondary coil operating as a voltage source; a leakage inductor(LL) connected to the secondary coil of the booster inductor, and which limits the current being applied from the secondary coil; an auxiliary switching element(Q2) connected to the secondary coil of the booster inductor through the leakage inductor, and zero-current switched by the current limitation of the leakage inductor; a main switching element(Q1) which is zero-voltage switched when the current flowing by the switching operation of the auxiliary switching element reaches the current flowing at the primary coil of the booster inductor; and a blocking switching element which is switched during turn-off of the main switching element, such that the current flowing through the main switching element charges a resonance capacitor and provides a current path.

Description

High efficiency soft-switching AC-DC boost converter using coupled inductor and energy recovery circuit having power factor correction function}

The present invention relates to a soft switching AC-DC boost converter, and more particularly to a novel high efficiency soft switching AC-DC using a coupled inductor and an energy regeneration circuit with a power factor correction (PFC) circuit. Booster converter allows simpler circuit configuration to minimize EMI and harmonic distortion and switching losses due to switching noise and to reduce system size at a low cost The present invention relates to an AC-DC boost converter for high efficiency soft switching using a coupled inductor and an energy regenerative circuit having a power factor correction function that enables a compact, lightweight and high reliability.

Background Art Conventionally, a computer, an electronic calculator, a communication device, an audio / video device, and a medical device using a semiconductor device such as an integrated circuit (IC) or an integrated circuit (LSI) has a DC power source having various kinds of low voltage and high quality as an operating power source. It is required.

In order to supply such high-quality DC power to each device, the commercial AC voltage must be rectified to a desired DC voltage. As shown in FIG. 1, when using a line filter (LFT), a bridge diode (BD), and an LC filter, the cost is reduced. There is a point to be reduced.

However, as shown in FIG. 2 and FIG. 3, since the current flows only near the peak value of the commercial AC input voltage, the input current waveform is in the form of a pulse, which generates a large amount of harmonic distortion (HD). There is a ham.

Therefore, if the power factor is low, the efficiency of the power line decreases, and if there are many harmonics, it may adversely affect other electronic systems nearby, causing a malfunction.

On the other hand, the regulation of low power factor and harmonics is strengthened, and a regulation to regulate it was made in 1982 by the international standard IEC (International Electrotechnical Commission), and the representative is IEC 555-2, which is smaller than 600W. IEC 519 for higher capacities. These regulations were amended to IEC 100-3-2 in 1995 and represent the harmonic limits for Class D switching power supplies of 600 W and higher in IEC 1000-3-2. The United States and the European Union have already adopted the IEC standard to regulate harmonics, while Korea has not yet regulated the harmonics, but research to reduce noise and harmonics is active because it is expected to adopt the IEC standard in the near future. Is expected to come true

In order to improve and overcome this problem, a variety of high power factor AC-DC converter circuits have been proposed and applied. However, most of these AC-DC converter circuits employ a hard switching converter circuit, so that the unity power factor can be controlled and the input current can be made into a sinusoidal waveform. There are problems such as waveform distortion due to harmonics, electromagnetic interference (EMI) and switching loss due to switching noise.

In particular, power systems applied to information and communication devices, computer devices, and medical devices require small, light weight, high efficiency power factor correction (PFC) or switch-mode power supply (SMPS) systems. As the demand for power is rapidly increasing, the power factor correction circuit converter of the pulse width modulation (PWM) method, which is currently used hard switching, increases the size and weight of the inductor, transformer, and capacitor by increasing the switching frequency. Although it can be reduced, the switching loss for the switching element is proportional to the switching frequency, so the problem is that the loss increases.

Therefore, even with a simpler circuit configuration, the demand for the development of a high power factor converter having high power density with high efficiency even when the converter is operated at a high frequency while minimizing switching loss of the switch is increasing day by day.

Accordingly, the present invention has been made in view of the above-described conventional situation, and an object thereof is to apply only a small number of circuit elements to a hard switching PWM AC-DC boost converter so that the switching elements are zero-voltage switching and zero voltage switching. High efficiency with coupled inductor and energy regenerative circuit with power factor correction to enable zero-current switching and to achieve soft switching with minimal switching losses and harmonics It is to provide a soft switching AC-DC boost converter.

1 is a view showing the configuration of a conventional basic AC-DC rectifier circuit,

FIG. 2 is a view showing input voltage / current and harmonic waveforms of the conventional circuit shown in FIG. 1;

3 is a graph analyzing harmonics with respect to an input current in the circuit of FIG. 1;

4 is a diagram illustrating a circuit configuration of a high efficiency soft switching AC-DC boost converter using a coupled inductor having a power factor correction (PFC) function and an energy regenerative circuit according to the present invention;

5A and 5B are diagrams illustrating a transformer model and an equivalent model thereof of the boost inductor according to the present invention shown in FIG. 4;

6 is a view showing an equivalent circuit of a soft switching boost converter according to the present invention;

7 is a view showing an ideal operating waveform of the soft switching boost converter according to the present invention;

8 is a view showing the operating state of the first mode for the interval t0-t1 in the ideal basic operating waveform of Figure 7 for the boost converter of the present invention,

9 is a view showing the operating state of the second mode for the period t1-t2 in the ideal basic operating waveform of Figure 7 for the boost converter of the present invention,

10 is a view showing the operating state of the third mode for the period t2-t3 in the ideal basic operating waveform of Figure 7 for the boost converter of the present invention,

11 is a view showing the operating state of the fourth mode for the period t3-t4 in the ideal basic operating waveform of Figure 7 for the boost converter of the present invention,

12 is a view showing an operating state of a fifth mode for a period t4-t5 in the ideal basic operating waveform of FIG. 7 for the boost converter of the present invention;

FIG. 13 is a view showing an operating state of a sixth mode for a period t5-t0 + ts in the ideal basic operating waveform of FIG. 7 for the boost converter of the present invention; FIG.

14 is a view showing the configuration of the control circuit of the boost converter according to the present invention;

15 is a view showing the configuration of the EMI filter circuit applied to the present invention,

16 is a view showing a circuit configuration to which the boost converter of the present invention is applied;

17 is a waveform diagram illustrating a simulation result according to an operating characteristic of a soft switching AC-DC boost converter according to the present invention;

18A to 18C illustrate harmonic analysis results of input voltage, input current and harmonic experimental waveforms, hard switching, and soft switching of the present invention of a soft switching AC-DC boost converter according to a preferred embodiment of the present invention. Waveform diagram,

19A is a waveform diagram exemplarily illustrating characteristics of voltage, current, and current experiment waveforms of an auxiliary switching device of a main switching device in a soft switching AC-DC boost converter according to a preferred embodiment of the present invention;

19B is a view exemplarily illustrating characteristics of voltage and current test waveforms of an auxiliary switching device in a soft switching AC-DC boost converter according to a preferred embodiment of the present invention;

19C is a diagram illustrating characteristics of a voltage of a blocking diode and a current experimental waveform of a capacitor in a soft switching AC-DC boost converter according to a preferred embodiment of the present invention;

FIG. 20 is a view illustrating efficiency characteristic curves for an AC-DC boost converter for high efficiency soft switching using a coupled inductor having an power factor correction function and an energy regeneration circuit according to the present invention.

<Description of the symbols for the main parts of the drawings>

LFT: line filter, BD: bridge diode,

Q1, Q2: switching element, C1 to C3: capacitor,

L _b : stepped inductor, L _L : leakage inductor,

D _B : blocking diode, C _S : capacitor,

C _R : resonance capacitor, C _Q2 : clamp capacitor.

In order to achieve the above object, according to the present invention, in the AC-DC rectifier circuit for converting an AC input voltage into a DC voltage and supplying the load, the DC voltage is applied through the primary winding to operate as a dependent current source, A boost inductor whose secondary winding operates as a dependent voltage source, a leakage inductor connected to the secondary winding of the boost inductor to limit a current applied from the secondary winding, and a boost inductor of the boost inductor via the leak inductor. An auxiliary switching element connected to the secondary winding and switched to zero current by the current limiting of the leakage inductor; zero voltage switching when a current flowing by the switching of the auxiliary switching element reaches a current flowing in the primary winding of the boost inductor. The main switching device is advanced, and the main switching device is switched when the main switching device is turned off. High efficiency soft switching AC current flowing in the resonance capacitor is charged, and with the coupling inductor and the energy recovery circuit having a power factor correction function consisting of blocking the switching device to provide a different current paths - a DC up-converter is provided.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

That is, FIG. 4 is a diagram illustrating a circuit configuration of a high efficiency soft switching AC-DC boost converter using a coupled inductor having an power factor correction circuit and an energy regeneration circuit according to the present invention.

The configuration of the present invention is a two stage method that produces a constant DC voltage with a boost converter using a PFC circuit, and then obtains a desired output voltage through a DC-DC converter having an isolated transformer. This is a popular method. This two stage method has a low frequency ripple in the final output voltage and has an advantage of fast response.

In addition, the present invention described above is a boost converter using a PFC circuit, and as shown in FIGS. 5 and 6, the transformer model of the input inductor acts as a transformer for passing a large magnetizing current Im. This magnetizing current flows through the magnetizing inductance Lm. An ideal transformer with a turn-ratio of 1: N _X is assumed to be modeled as a tight coupling between the primary side and the auxiliary winding.

As shown in FIG. 4, the soft switching AC-DC converter according to the present invention has a simpler circuit configuration, while the blocking diode D _B is simultaneously controlled while the main switching element controls zero voltage switching (ZVS). Soft switching can be realized.

The soft switching AC-DC converter according to the drawing includes a boost inductor L _b , a main switching element consisting of a magnetic circuit, an IGBT or a MOS-FET, an auxiliary switching element Q1, Q2, and a leakage inductor L. _L ), a blocking diode (D), a resonant capacitor (C _R ), a clamp capacitor (C _Q2 ), and a capacitor (C _S ).

The boost inductor L _b has a primary winding connected to an AC input voltage source V _in , a secondary winding additionally connected to the auxiliary switching element Q2, and a leakage inductor L _L. Used as a resonant inductor. Thus, the secondary winding provides a path with little loss.

In addition, by connecting a capacitor (C _Q2 ) in parallel to the auxiliary switching element ( _Q2 ), the voltage spike and oscillation generated at the moment when the auxiliary switching element (S _Q2 ) is turned off is greatly reduced. Make it work.

The leakage inductor L _L generated by adding the secondary winding to the boost inductor L _b is a current flowing through the auxiliary circuit so that the auxiliary switching element Q ₂ performs zero-current switching (ZCS). limit (di / dt)

In addition, while the auxiliary circuit is operating, it operates as a current transformer. The secondary winding is then used to create an auxiliary path for the current flowing through the primary side. The inductor acts as a boost inductor in all remaining sections in which the auxiliary circuit is not operated.

That is, the boost inductor L _b and the magnetic circuit start to flow in the secondary winding under the influence of the current flowing in the primary winding when the auxiliary switching element Q2 is turned on. The magnetizing current of the secondary winding is influenced in the direction of attenuation, while the current flowing through the auxiliary circuit reaches the current value according to the turn ratio (n) of the primary winding of the boost inductor L _b and N _X. When the charge stored in the resonant circuit can be removed.

After that, when the voltage of the main switching circuit drops to 0V, the main switching element Q ₁ is turned on, so that the current flowing through the boost inductor L _b flows through the main switching element Q ₁ . Auxiliary switching element Q ₂ has a zero-volt-switching (ZVS) operating characteristic that is operated to turn off at zero current.

In this case, since the auxiliary switching element Q2 should be unidirectional, a fast recovery diode D _FR is connected in series to the corresponding auxiliary switching element Q2 in order to block current flowing in the opposite direction. Once the current decreases to zero, the auxiliary switching element Q2 is turned off to zero current switching (ZCS).

On the other hand, when the magnetic circuit in which the secondary winding of the boost inductor L _b is added to the AC-DC converter of the present invention is applied, the maximum current flowing in the auxiliary circuit is half of the current flowing in the boost inductor L _b . This can be limited to a small capacity of the auxiliary circuit element, and the switching conduction loss can be reduced.

In addition, by connecting the capacitor (C _Q2 ) in parallel to the auxiliary switching element (Q2), so that the voltage spike and oscillation generated in the process of turning off the auxiliary switching element (Q2) can be reduced. do.

In the same figure, a capacitor C _S is connected to the blocking diode D _B in parallel to reduce and reduce a loss of the corresponding blocking diode D _B generated at the time of turn-on and turn-off of the switching element. By allowing the blocking diode D _B to operate at a reduced stress, the electromagnetic interference (EMI), which is a major obstacle of the system, can be reduced while improving the efficiency of the conventional converter.

Next, FIGS. 5A and 5B are diagrams illustrating a transformer model and an equivalent model thereof of the boost inductor according to the present invention shown in FIG. 4.

In the transformer model of the boost inductor shown in FIG. 5A and the equivalent model shown in FIG. 5B, assuming that the transformer is in an ideal state, the primary winding may be a slave current source, and the secondary winding side may be replaced by a slave voltage source. And the leakage inductance of the secondary winding is L _L and is used as a resonant inductor.

6 is a diagram illustrating an equivalent circuit of a soft switching boost converter according to the present invention, wherein the equivalent circuit of the soft switching AC-DC boost converter according to the drawings includes a main switching element Q ₁ and an auxiliary switching element Q ₂ . , Boosted inductor and magnetic circuit (Coupled Inductor), resonant capacitor (C _R ), blocking diode (D _B ), parallel capacitor (C _Q2 ) of auxiliary switching element (Q ₂ ), all voltages of the equivalent circuit The overcurrent will appear based on the three terminals (ⓒ, ⓟ, ⓐ).

Here, the primary winding of the boost inductor may be replaced as a slave current source, and the secondary winding may be replaced as a slave voltage source.

Next, the operation of the soft switching AC-DC converter according to the present invention made as described above will be described in detail with reference to FIGS. 7 to 13.

That is, FIG. 7 is a diagram illustrating an ideal basic operation waveform of the boost converter according to the present invention, and the switching operation according to the section of t0 to t5 is divided into six modes (first mode to sixth mode).

First, in the first mode, the resonant capacitor C _R is discharged to zero, and the capacitor Cs is charged to the output voltage Vo, while the clamp capacitor C _Q2 is discharged. It is assumed that the switching element Q2 is in an off state and the main switching element Q1 is switched from an on state to an off state.

The first mode corresponds to a section of t ₀ to t ₁ in FIG. 7, and the circuit of the first mode is as shown in FIG. 8. That is, the first mode is a main switching element (Q ₁₎ a ZVS (Zero-Voltage-Switching: ZVS ) in the range of t ₀ to the turn-is started while off, flows into the main switching element (Q ₁₎ Since the current flows through the resonant capacitor C _R , the voltage applied to the corresponding main switching element Q ₁ gradually increases to charge the output voltage V ₀ .

Accordingly, the resonant capacitor C _R is a combination of a capacitance C _DS connected to an external node of the main switching element Q ₁ , which is a field effect transistor, and a capacitance C _{oss of} the main switching element, and a drain. Since the dv / dt of the short voltage is controlled by the corresponding capacitor C _R , the resonant capacitor C _R initially sets the drain voltage of the main switching element Q1 to 0 (Zero) V to turn off. The loss of the main switching element Q ₁ can thus be significantly reduced.

In addition, in the section of t ₀ , the input current charges the clamp capacitor C _Q2 connected in parallel to the auxiliary switching element Q ₂ .

The clamp capacitor C _Q2 prevents voltage spike and oscillation generated when the auxiliary switching element Q ₂ is turned off.

When the charging of the resonant capacitor C _R and the clamp capacitor C _{Q2 of} the main switching element Q ₁ is completed, the second mode is shifted from the first mode to the next second mode. Corresponds to the section from t1 to t2 at 7.

The second mode corresponds to the period t1 to t2 in FIG. 7, and as shown in FIG. 9, the voltage of the capacitor Cs is charged in the reverse direction by the output voltage V ₀ in the reverse direction. As a result, only the charge of the capacitor Cs is discharged to the load side at the same time, and the blocking diode D _B is turned on at zero voltage so that the current Im of the boost inductor flows to the output load side.

Since the blocking diode D _B is turned on at zero voltage, voltage stress can be reduced. The blocking diode D _B is turned on at zero voltage and the input current Im flows to the output in a state in which the main switching element Q ₁ and the auxiliary switching element Q ₂ are turned off. The voltage across the main switching element Q ₁ is equal to the output voltage Von = Vpan.

Next, the third mode corresponds to the period t2 to t3 in FIG. 7, and another switching period starts at t2 as shown in FIG. 10, and the drain voltage of the main switching element Q ₁ is set to 0V. In order to drop, the auxiliary switching element Q ₂ is first turned on with zero current switching ZCS.

The auxiliary switching element Q ₂ is turned on by zero current switching (ZCS) because the current of the auxiliary inductor increases at a ratio of [Vpan + Nx (Vpan-Vcan)] / L _L , and the current is As it increases, the auxiliary current is reflected on the primary winding side until it reaches the value of Im / Nx. In this case, the current Im of the boost inductor is a direct current magnetizing current flowing through the boost inductor, and the maximum current flowing to the auxiliary switching element is limited to about half of the current Im flowing in the boost inductor L _b . Can be.

This is because not only the current flowing in the auxiliary circuit affects the primary side of the input inductor, but also the current flows according to the turn ratio n. During this time, when the current of the blocking diode D _B decreases to zero, the blocking diode D _B is turned off by soft switching.

On the other hand, the state equation for the current flowing through the leakage inductor (L _L ) is as shown in Equation 1 below.

Here, if the current does not flow through the blocking diode D _B at t3 in the end section of the third mode, a loss may occur due to the reverse recovery characteristic of the blocking diode D _B , but the current may occur. Since the charge flows to the output voltage of the capacitor Cs, the loss can be reduced regardless of the reverse recovery characteristic of the blocking diode D _B. As a result, the converter circuit of the present invention can not only operate at lower temperatures, but also minimize the electromagnetic interference (EMI).

Subsequently, the third mode proceeds to a subsequent fourth mode, and the fourth mode corresponds to a section of t3 to t4 in FIG. 7.

In the fourth mode, as shown in FIG. 11, when the current flowing to the auxiliary switching element Q ₂ becomes I _m / Nx at _{t 3} , the corresponding leakage inductor L _L and the resonant capacitor C _R undergo resonance. The resonant period is continued until the resonant capacitor C _R is discharged and the voltage at both ends thereof becomes zero.

The current flowing through the auxiliary switching element Q2 continues to increase while the resonant capacitor C _R is discharged, and the time required for the drain voltage of the main switching element Q ₁ to reach zero is zero. 1/4 of the resonant period. At the end of the period t3 to t4 including the fourth mode, the body diode of the main switching element Q ₁ is turned on.

Accordingly, the current of the leakage inductor L _L and the capacitor voltage of the main switching element Q ₁ are as shown in Equations 2 and 3 below.

Next, the fourth mode proceeds to the fifth mode, which corresponds to the period t4 to t5 in FIG. 7.

In the fifth mode, as shown in FIG. 12, in the period t4, the drain voltage V _ca = v _s of the main switching element Q ₁ becomes 0 V, and the resonance current is leaked from the resonant capacitor C _R. By free-wheeling to the body diode of the main switching element Q ₁ through L _L , the corresponding body diode is turned on. At this time, the main switching element Q ₁ is turned on when the body diode of the corresponding main switching element Q1 is turned on to turn on the zero voltage switching ZVS, that is, the time t4 and the time ton. The turn-on gate signal of the main switching element Q1 is applied to conduct the circuit between them. As the main switching element Q1 is turned on by zero voltage switching ZVS, switching loss can be reduced, and the voltage applied to the boost inductor Lm is reduced to 0 V because the voltage applied to the main switching element Q ₁ becomes 0V. _{Becomes the} same as V _ca.

Therefore, the voltage appearing on the secondary winding of the boost inductor Lm becomes NxVca, and the voltage across the leakage inductor L _L becomes -NxVca + vca = -NxVca, so that the boost inductor Lm is a coupling transformer. The energy is returned to the voltage source Vin through the step-up inductor Lm, and the current of the auxiliary switching element Q ₂ decreases at a ratio of NxVca / L _L.

Current of the auxiliary switching element (Q ₂₎ falls to 0 (Zero), the auxiliary switching element (Q ₂₎ is to keep the current to zero due to the nature of flowing a current to the one-way, in a period (t ₅₎ It is turned off by zero current switching (ZCS).

The state equation for this is described as the leakage inductor current, which is represented by Equation 4 below.

Next, the fifth mode proceeds to the following sixth mode, and the sixth mode corresponds to a section of t5 to t0 + t5 in FIG. 7.

In the sixth mode, as shown in FIG. 13, such a circuit operates as a typical hard switching PWM boost converter, and the boost inductor Lm has energy from the voltage source Vin magnetizing the boost inductor Lm. It is used as a conventional filter inductor because it is stored in current, and positive di / dt becomes equal to Vca / Lm, while output capacitor C _R discharges the output voltage to the load.

Next, FIG. 14 is a diagram showing the configuration of the control circuit of the boost converter according to the present invention.

As shown in FIG. 14, the control circuit of the high efficiency soft switching AC-DC boost converter according to the present invention includes a voltage compensator, a multiplier, a current compensator, and a triangular wave generator. SK) and divider (DK).

In the control circuit, the comparator com of the voltage compensator detects the output voltage V _O and compares it with the reference voltage V _ref , and the compared error signal e = V _ref −V _O is a voltage compensator. It is used to maintain the output DC voltage at the level specified by and to obtain stable transient response characteristics.

Here, in the control circuit for controlling the AC-DC converter of the present invention, the main purpose of the system is to control the output voltage and maintain the AC input voltage and the AC input current as in-phase and sinusoidal input current waveforms. Detects the voltage to obtain the control reference waveform (| V _AC |), and the detected voltage | V _AC | is the voltage compensator through the divider (DK) in the multiplier (MK) to obtain the input current command signal (I _com ) in phase. It is obtained by multiplying the output signal V _vea from (I _com = | V _ac | × V _vea ).

In practice, the current I _Lb flowing in the boost inductor L _b is controlled to accurately track the current command signal I _com by appropriately designing a current compensator in the current loop, so that the control circuit Through the unit input power factor can be obtained.

In developing the above driving circuit, the power factor is 0.999, and the total current harmonic distortion (THD) is limited to 3% or less. It is desirable to apply the pre-regulator of UC3854BN.

Next, FIG. 15 is a diagram showing a configuration of an EMI filter circuit applied to the present invention, and FIG. 16 is a diagram showing a circuit configuration to which the boost converter of the present invention is applied.

As shown in Figs. 15 and 16, the circuit to which the high efficiency soft switching boost converter of the present invention is applied has a high efficiency soft switching AC-DC boost converter using a coupled inductor and an energy regeneration circuit having a frequency of 100 kHz at 2000 W of power. The step-up inductor (L _b ) is designed such that the peak-peak ripple current is 15% of the current (I_Lbpk) of the peak step-up inductor (L _b ) in order to reduce the loss due to the harmonic switching ripple. The value of (L _b ) is 521 μH, the leakage inductance value is 39 μH, and a PQ50 / 50 core manufactured by TDK Corp. was used as a device having low loss characteristics even at high frequency. Nx was set to 0.5 in consideration of the current stress and the voltage stress of the auxiliary circuit.

The resonant capacitor is the sum of the output capacitor of the main switching element Q ₁ and the external node capacitor C _R , and low ESR and ESL are required at high frequencies.

In addition, in order to reduce the turn-off loss generated when the switching current of the main switching element Q ₁ is switched to the capacitor side, a large charging current may be charged, and the resonant capacitor C may be considered in consideration of the parasitic inductor and the parasitic capacitor. The value of _R ) must be determined. Therefore, the resonant capacitor C _R used a ceramic capacitor having a low loss factor (tan δ) of 0.2% and a low loss.

In addition, the main switching device (Q ₁ ) is applied to the field effect transistor device of 500V, 30A having R_DS (on) = 0.18Ω (25 ° C) and C_OSS ?? 600pF, the auxiliary switching device (Q ₂ ) A 500V, 22A field effect transistor device with R_DS (on) = 0.24Ω (25 ° C) and C_OSS ?? 470pF is used, and the blocking diode is a diode device with a reverse recovery time (t _rr ) of 50ns. .

In addition, the electromagnetic interference (Electro-Magnetic Interference; EMI) can be classified into a conducted component (Conducted Emission (CE) and the radiated component (Radiated; RE) appearing in the space (air) to go through the power line, the radiation component In this case, measures are taken by shielding or grounding, and the conductive powder is an EMI filter as shown in FIG. 14. The line filter LFT1 (LFT2) and the resistor R _{11 are shown in} FIG. And capacitors C ₁₁ , C ₁₂ , C _13, and C ₁₄ to reduce noise as a whole. As a signal path countermeasure, the pattern is configured to reduce the parasitic capacitors for the PCB and the arrangement of each component, and in particular, the capacitor C _S is connected to the blocking diode D _B in turn to turn on. And to reduce electromagnetic interference (EMI), an important consideration of the system at turn-off.

Next, a simulation result and an experimental result of the present invention will be described with reference to FIG. 17.

That is, FIG. 17 is a waveform diagram illustrating a simulation result according to an operating characteristic of the AC-DC boost converter according to the present invention.

As shown in FIG. 17, the AC-DC step-up converter of the present invention has a simulation result using Pspice, which is almost identical to the ideal waveform shown in FIG. 7.

Next, Figure 18a is a waveform showing the experimental results of the input voltage, current and harmonics at the input voltage 220VAC, output 400VDC, switching frequency 100kHz, 1kW, power factor 0.998, Figure 18b is the input current when the conventional hard switching Fig. 18C is a graph showing harmonic analysis of input current of a boost converter according to the present invention.

In harmonic analysis, the FFT analysis was performed on the experimental waveform measured by C program by determining the step so that the sampling number is 1024 by selecting one cycle from the stored data after downloading the input current from the oscilloscope.

In the figure, the soft switching boost converter according to the present invention has a total harmonic distortion factor (THD) of 0.03102 (about 3%). The total harmonic distortion (THD) of the hard switching converter is 0.07829 (about 8%), and the harmonic distortion relative to the input current of the simple AC-DC rectifier circuit as shown in Figs. 1 and 3 is 1.22505.

Thus, it can be seen that the soft switching AC-DC boost converter of the present invention has about 3% less total harmonic distortion than hard switching, which is the harmonic limit for switching power supplies (Class D) in the IEC 1000-3-2 standard. It turns out that it is less than.

19A, 19B, and 19C exemplarily show characteristics of the main switch voltage, the current and the auxiliary switch current, the voltage of the blocking diode and the current waveform of the capacitor in the AC-DC boost converter of the present invention. to be.

19A shows that the main switching element Q1 soft switches to zero voltage switching ZVS in the main switch voltage, current and auxiliary switch current waveforms in the soft switching AC-DC boost converter of the present invention. It can be seen that the resonance current flowing at (Q2) becomes about 8A.

As shown in FIG. 19B, voltage spikes and oscillations generated when the auxiliary switching element Q2 is turned off by the auxiliary switch voltage and current experimental waveforms of the soft switching AC-DC boost converter according to the present invention. Oscillation) is reduced.

As shown in FIG. 19C, the voltage waveform of the blocking diode D _B and the current waveform of the capacitor C _S connected in parallel with the blocking diode are illustrated. In the figure, it can be seen that the blocking diode reduces the stress generated during turn-on or turn-off by soft switching.

In addition, as shown in FIG. 20, the active switch elements Q1, Q2, and D _B allow soft switching to proceed, and a secondary winding is added to the boost inductor L _b to provide a lossless current path. By connecting the capacitors in parallel to the blocking diode, the blocking diode's stress is reduced during turn-on and turn-off, resulting in an overall maximum efficiency of 97.63% at full load and high input.

It is a matter of course that the present invention having the above-described embodiments can be variously modified without departing from the gist of the present invention without departing from the gist thereof.

As described above, according to the present invention, a coupling inductor and an energy regenerative circuit having a power factor correction circuit are used, the active switch element allows soft switching to proceed, the leakage inductance is used as a resonant inductor, and a capacitor in parallel to the blocking diode. By reducing the stress on the blocking diodes during turn-on and turn-off and enabling the blocking diodes to operate with reduced stress, the system considerably reduces electromagnetic interference, an important consideration of the system. In addition, soft switching by the switching element and the blocking diode of the boost converter has the effect of reducing the harmonic distortion as a whole rather than the conventional hard switching.

As a result, by adding only a small number of circuit elements to the hard-switching PWM AC-DC boost converter, the efficiency can be improved compared to the conventional hard-switching converter and the system can be controlled at a high frequency to make the boost inductor small. In addition, the capacitor can be used with a smaller capacity, and the active switching element performs soft switching to operate the system at a lower temperature, thereby significantly reducing the heat sink area. Light weight and high reliability can be produced to have a special effect.

Claims (6)

In the high efficiency soft switching AC-DC boost converter circuit, A boost inductor receiving the DC voltage through the primary winding and operating as a slave current source, the secondary winding operating as a slave voltage source; A leakage inductor connected to the secondary winding of the boost inductor to limit a current applied from the secondary winding; An auxiliary switching element connected to the secondary winding of the boost inductor through the leakage inductor and switched at zero current by a current limit of the leakage inductor; A main switching device in which zero voltage switching proceeds when a current flowing by switching of the auxiliary switching device reaches a current flowing in a primary winding of the boost inductor; Combined inductor and energy regeneration with a power factor correction function, characterized in that it consists of a blocking switching element that is switched at the time of turning off the main switching element and the current flowing to the main switching element charges the resonant capacitor and provides a different current path. AC-DC boost converter for high efficiency soft switching using circuitry. 2. The method of claim 1, wherein the main switching element and the auxiliary switching element comprise one of an IGBT and a MOS-FET, and the high efficiency soft switching using a combined inductor and an energy regenerative circuit having a power factor correction function. AC-DC boost converter. 3. The high efficiency software using a combined inductor and energy regeneration circuit having a power factor correction function according to claim 2, wherein the main switching element further comprises a resonant capacitor connected in parallel to reduce turn-off losses. AC-DC boost converter for switching. 3. The coupled inductor and energy regeneration circuit of claim 2, wherein the auxiliary switching device further comprises a capacitor connected in parallel to reduce spikes and oscillations at turn-off. AC-DC boost converter for high efficiency soft switching. 2. The AC-DC boost converter for high efficiency soft switching using a coupled inductor having an power factor correction function and an energy regeneration circuit according to claim 1, wherein the blocking switching element comprises a blocking diode. 6. The coupled inductor and energy regenerative circuit of claim 5, wherein the blocking switching element further comprises capacitors connected in parallel to reduce losses during turn-on and turn-off. AC to DC boost converter for high efficiency soft switching.