KR20050000689A - Power converter with improved power factor compensation - Google Patents

Abstract

PURPOSE: A power converter is provided to compensate a power factor regardless of the size of the input AC voltage and reduce harmonics, by converting the waveform of input current into a sine wave similar to the waveform of input voltage. CONSTITUTION: A power converter comprises a full wave rectifying unit(31), a half wave rectifying unit(32), a smoothing capacitor(C1), a power factor compensation unit(33), and a harmonics reduction unit(34). The full wave rectifying unit full wave rectifies an AC power. The half wave rectifying unit is connected in parallel to the full wave rectifying unit, and half wave rectifies the AC power. The smoothing capacitor is connected to an output terminal of the full wave rectifying unit, and smooths the waveform output from the full wave rectifying unit. The power factor compensation unit controls the waveform of an input current in accordance with the difference voltage between the output voltage of the full wave rectifying unit and a voltage(V1) of the smoothing capacitor. The power factor compensation unit controls the waveform of an input current in accordance with the difference voltage between the output voltage of the full wave rectifying unit and a neutral point voltage(V2) of a primary coil(WC1). The harmonics reduction unit reduces harmonics of input current by controlling the waveform of an input current in accordance with the difference voltage between a voltage(V3) obtained by reducing the voltage(V1) of the smoothing capacitor and the voltage output from the full wave rectifying unit.

Description

POWER CONVERTER WITH IMPROVED POWER FACTOR COMPENSATION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter applied to a power adapter for converting an AC power source into a DC power source, and more particularly, by converting a waveform of an input current into a sinusoidal wave similar to a waveform of an input voltage, thereby reducing the power factor of the power source regardless of the magnitude of the AC input voltage. The present invention relates to a power converter that improves inverse rule compensation and harmonic reduction that can compensate for power factor and reduce harmonics.

In general, in the case of an electronic communication device or a computer system and a large-capacity electronic device, a switching mode power supply device that receives an AC power to be used and converts it into DC power, and then converts it into DC power of the same power using a switching means It is used a lot. In this case, the switching mode power supply (SMPS) inevitably generates the switching noise, the electromagnetic wave generated in the low power consumption electronic devices, that is, switching noise is not a big problem, but in the case of high output, the electromagnetic environmental pollution is serious. have.

Therefore, in recent years, in Europe and Japan, the IEC 1000-3-2 standard has been enacted to remove the harmonic noise generated from power supplies, and switching mode power supplies with input power consumption of 75W or higher are required for power factor correction (PFC). To be applied. The reason for the strengthening of regulations is to dispose of the electromagnetic pollution, which is being watched recently. Such regulations related to electromagnetic pollution are expected to be gradually expanded.

In the prior art, which is currently applied, a power converter having a two-stage configuration generally comprising a PFC stage and a DC / DC stage is shown in FIG.

1 is a circuit diagram of a conventional two stage power converter.

The rectifier 11 illustrated in FIG. 1 performs a function of converting an input AC power into DC power. The power factor correction (PFC) unit 12 serves to improve the power factor and output a controlled DC voltage by making the input current shape into a sine wave which is almost similar to the input AC power. The DC / DC converter 13 receives DC power from the power factor correction (PFC) unit 12 and supplies DC power required to the load side.

The conventional power converter has an advantage that the shape of the input current is almost sine wave, but the power factor correction (PFC) unit must be used separately, so that the power factor correction unit 12 has a power factor correction stage and a power factor correction (PFC) control stage, And it consists of a complex circuit including a switching element, such that the number of parts required increases the product price, there is a problem that the possibility of failure increases.

A single-stage or one-stage power converter for solving the problem of the conventional power converter shown in FIG. 1 is shown in FIG. 2.

2 is a circuit diagram of a conventional single stage power converter.

In the power converter illustrated in FIG. 2, a bridge diode (BD), a smoothing capacitor (C1), a transformer (T1), and a switching element (Q1) for converting an AC input power into a DC power source are generally used as a DC / DC converter. It consists of a flyback circuit. Here, there is a diode D1 which prevents a reverse flow from the first filter capacitor C2 and the smoothing capacitor C1 to the first filter capacitor C2, and the power factor correction coil L1 and the power factor correction coil ( The diode D2, which prevents the reverse flow of l2), is connected to the neutral point of the transformer, thereby reducing the high frequency component of the input current to compensate for the power factor. Details of this are described in US Pat. No. 5,673,184.

In the power converter of FIG. 2, unlike the configuration of the power converter of FIG. 1, a complex power factor correction (PFC) unit is not used, and the power factor correction unit 22 of FIG. 2 is coiled at the stage of the DC / DC converter 23. And a relatively simple circuit for improving power factor and delivering energy by using a passive element such as a diode. Therefore, the advantage of such a power converter is that the power factor correction (PFC) control unit and the power factor correction (PFC) switching element used in the conventional two-stage configuration method are not necessary, so the circuit configuration is simple and the number of elements used is reduced and the price is reduced. It is inexpensive and has a low probability of failure.

However, since the power factor correction function is deteriorated by not using a complicated separate power factor correction circuit, the shape of the input current has a different shape from that of the sine wave, and thus, a large amount of harmonic components are included in the input current.

3A, 3B, and 3C are waveform diagrams of the individual input currents and the combined input currents.

During a part of the cycle of the input power source Vac shown in FIG. 3A, there is little input current as shown in FIG. ) Flows. During a short period of one cycle, a relatively large current i1 flows, and the sum of the two currents i1 and i2 becomes the input current iac shown in FIG. As the current i1 having a relatively large magnitude starts to flow, the input current has a shape that changes rapidly, and thus has a relatively large harmonic component.

The present invention has been proposed to solve the above problems, and its object is to convert the waveform of the input current into a sine wave similar to the waveform of the input voltage, thereby compensating the power factor of the power source regardless of the magnitude of the AC input voltage. In addition, the present invention provides a power converter that improves inverse rule compensation and harmonic reduction that can reduce harmonics.

1 is a circuit diagram of a conventional two stage power converter.

2 is a circuit diagram of a conventional single stage power converter.

3A, 3B, and 3C are waveform diagrams of the individual input currents and the combined input currents.

4 is a circuit diagram of a power converter according to the present invention.

5A, 5B, and 5C are waveform diagrams of individual input currents and composite input currents.

Explanation of symbols on the main parts of the drawings

31: full wave rectifier

32: half-wave rectifier

33: power factor correction unit

34: harmonic reduction part

35: transformer

35: pressure-resistant processing unit

In order to achieve the above object of the present invention, the power converter of the present invention

In the power converter having a transformer for reducing the input power to the primary winding coil and secondary winding coil ratio,

A full-wave rectifier for full-wave rectifying the AC power;

A half-wave rectifier connected in parallel to the full-wave rectifier to half-wave rectify the AC power;

A smoothing capacitor connected to an output terminal of the full wave rectifying unit to smooth the output waveform of the full wave rectifying unit;

The waveform of the input current is controlled by the difference voltage between the output voltage of the full wave rectifier and the voltage of the smoothing capacitor, and the waveform of the input current is controlled by the difference voltage between the output voltage of the full wave rectifier and the mid-point voltage of the primary winding coil. A power factor correction unit for adjusting the power factor; And

Harmonic reduction unit for reducing the harmonics of the input current by adjusting the waveform of the input current by the voltage difference between the voltage of the smoothing capacitor to a predetermined size reduced voltage and the output voltage of the full wave rectifier.

Characterized in having a.

In addition, the power converter of the present invention

In the power converter having a transformer for reducing the input power to the primary winding coil and secondary winding coil ratio,

A full-wave rectifier for full-wave rectifying the AC power;

A half-wave rectifier connected in parallel to the full-wave rectifier to half-wave rectify the AC power;

A smoothing capacitor connected to an output terminal of the full wave rectifying unit to smooth the output waveform of the full wave rectifying unit;

A first diode having an anode terminal connected to the first half wave output point of the full wave rectifying unit and a cathode terminal connected to the smoothing capacitor;

A first filter capacitor connected between an anode end of the first diode and a second half wave output point of the full wave rectifier;

A second filter capacitor connected between an output point of the half wave rectifier and a second half wave output point of the full wave rectifier;

A power factor correction coil having one end connected to an output point of the half wave rectifier;

A second diode having an anode terminal connected to the other end of the power factor correction coil and a cathode terminal connected to the neutral point of the primary winding coil;

A high frequency reduction coil having one end connected to a first output point of the full wave rectifier;

A third diode having an anode end connected to the other end of the high frequency reduction coil; And

An auxiliary winding coil connected between the cathode end of the third diode and one side of the primary winding coil and wound in a direction opposite to the winding direction of the primary winding coil;

Characterized in that it comprises a.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings referred to in the present invention, components having substantially the same configuration and function will use the same reference numerals.

4 is a circuit diagram of a power converter according to the present invention.

Referring to FIG. 4, the power converter according to the present invention is a power converter having a transformer 35 for depressurizing an input power by a ratio of a primary winding coil WC1 and a secondary winding coil WC2, which is a full-wave rectifier for AC power. A full wave rectifying unit 31 connected to the full wave rectifying unit 31 in parallel, a half wave rectifying unit 32 for half-wave rectifying the AC power, and an output terminal of the full wave rectifying unit 31, and the full wave rectifying unit ( The waveform of the input current is adjusted by the difference between the smoothing capacitor C1 smoothing the output waveform of 31) and the output voltage of the full wave rectifying unit 31 and the voltage V1 of the smoothing capacitor C1. The power factor correction unit 33 adjusts the waveform of the input current by the difference between the output voltage of the full-wave rectifying unit 31 and the middle voltage V2 of the primary winding coil WC1, and the smoothing capacitor C1. Voltage V3 obtained by depressing the voltage V1 by a predetermined magnitude and the output of the full-wave rectifier 31 It includes a harmonic reduction unit 34 for reducing the harmonics of the input current by adjusting the waveform of the input current by the difference voltage with the output voltage.

The power factor correction unit 33 includes a first diode D1 having an anode terminal connected to the first half-wave output point P1 of the full wave rectifying unit 31 and a cathode terminal connected to the smoothing capacitor C1; The first filter capacitor C2 connected between the anode end of the first diode D1 and the second half wave output point P2 of the full wave rectifier 31, and the output point P3 of the half wave rectifier 32. And a second filter capacitor C3 connected between the second half-wave output point P2 of the full-wave rectifier 31, and a power factor correction coil having one end connected to the output point P3 of the half-wave rectifier 32. L1), an anode connected to the other end of the power factor correction coil L1, and a second diode D2 having a cathode connected to the neutral point MP of the primary winding coil WC1.

The harmonic reducing unit 34 has a high frequency reduction coil L2 having one end connected to the first output point P1 of the full wave rectifying unit 31 and an anode end connected to the other end of the high frequency reduction coil L2. The third diode D3 is connected between the cathode end of the third diode D3 and one side of the primary winding coil WC1, and is wound in a direction opposite to the winding direction of the primary winding coil WC1. An auxiliary winding coil (Waux) is included.

In addition, the power converter further includes a breakdown voltage processing unit 37 that provides energy of the power factor correction coil L1 to the secondary winding coil WC2, and the breakdown voltage processing unit 37 of the transformer 35 One end is connected to one end of the output terminal, and has a fifth coil L5 for releasing power from the power factor correction coil L1 of the power factor correction unit 33, and an anode terminal connected to the other end of the fifth coil L5. And a fifth diode D5 having a cathode terminal connected to the other end of the output terminal of the transformer 35.

Here, Q1, which is not described in the drawings, is a switching transistor, D4 is a diode, and C4 is a capacitor.

Hereinafter, the operation and effects of the present invention will be described in detail with reference to FIGS. 4 to 5.

Referring to FIG. 4, the full-wave rectifying unit 31 of the present invention receives AC power of approximately 90V to 264V, rectifies and outputs AC power as a DC power source, and the half-wave rectifying unit 32 directs the input AC power to DC. The half-wave rectification is performed by the power supply, and the power factor correction unit 33 of the present invention compensates the power factor for the input power input to the full-wave rectifying unit 31 and the half-wave rectifying unit 32 and inputs the full-wave rectifying unit 31. The harmonic reduction unit 34 of the present invention reduces the harmonics included in the waveform of the input power source.

First, the power factor correction unit 33 will be described in detail. First, the output voltage of the full-wave rectifying unit 31 is smoothed by the smoothing capacitor C1. In this case, the power factor correction unit 33 of the present invention The first filter capacitor C2 reduces the noise component included in the output of the full wave rectifier 31.

The first diode D1 of the power factor correction unit 33 prevents a reverse flow of current from the smoothing capacitor C1 to the first filter capacitor C2, and further, when the inrush current is started, the transformer 35 This prevents the primary winding coil (WC1) from being transferred to the side.

In addition, the second filter capacitor C3 of the power factor correction unit 33 reduces the noise included in the output of the half-wave rectifier 32, and the second diode D2 of the power factor correction unit 33 is the flat A backflow from the utilization capacitor C1 to the second filter capacitor C3 is prevented, and the power factor correction coil L1 connected in series with the second diode D2 prevents a sudden change in current.

Referring to FIG. 5A, when the output voltage Vac of the full wave rectifying unit 31 is higher than the voltage V1 of the smoothing capacitor C1, the first diode D1 is turned on and thus, FIG. As shown in FIG. 2), when the first current i1 flows and the output voltage of the half-wave rectifier 32 is higher than the midpoint voltage V2 of the primary winding coil WC1, the second diode is turned on. As shown in FIG. 5B, the second current i2 flows so that the waveform of the synthesized current of the first current i1 and the second current i2 follows the voltage waveform of the input power source. Improve power factor.

That is, by the power factor correction unit 33 of the present invention, the neutral point MP voltage V2 of the transformer 35 is approximately 1/2 of the voltage V1 of the smoothing capacitor C1. The second current i2 flows in the section (section 1) in which the output voltage Vac of the full-wave rectifier 31 is higher than the second voltage V2, and the second current i2 flowing in the second diode D2. Due to the wide interval (section 1), the waveform of the input current can approach the waveform of the input voltage to compensate for the power factor.

On the other hand, the harmonic compensator 34 of the present invention, the AC input voltage is higher than the voltage (V1) of the smoothing capacitor (C1) to prevent the phenomenon that the input current is rapidly increased to increase the harmonic components, AC input voltage In the section (section 2) which is slightly lower than the voltage V1 of the smoothing capacitor C1, the input current flows more, thereby reducing the harmonic content.

In detail, when the output voltage of the full-wave rectifying unit 31 is higher than the voltage V3 of the voltage V1 of the smoothing capacitor C1 reduced by a predetermined size, the third diode D3 is turned on, and thus, FIG. As shown in (b), a third current i3 flows, and the third current i3 is combined with the first and second currents i1 and i2 to form a current iac of the input power source. do.

Here, the third voltage V3 is set higher than the second voltage V2 and lower than the first voltage V1. Accordingly, the output voltage of the full wave rectifying unit 31 and the third voltage are set. The third current i3 generated by the difference voltage with the V3 has a longer flow time than the first current i1 and a short flow time than the second current i2. Therefore, harmonics due to the sudden current difference between the first current i1 and the second current i2 may be reduced due to the third current i3.

On the other hand, the breakdown voltage processing unit 37 of the present invention provides the energy of the power factor correction coil L1 to the secondary winding coil WC2. If the load is small, the current introduced into the power factor correction coil L1 is small. Is used to solve the problem of flowing into the smoothing capacitor C1 to increase the breakdown voltage of the smoothing capacitor, and smoothing the current flowing into the power factor correction coil L1 through the load-side first filter capacitor C4. It serves to reduce the breakdown voltage of the capacitor C1.

According to the present invention as described above, it is possible to satisfy the regulation of IEC 1000-3-2 even at a low input voltage by reducing the harmonic components regardless of the magnitude of the AC input voltage.

According to the present invention as described above, by converting the waveform of the input current into a sine wave similar to the waveform of the input voltage, it is possible to compensate the power factor of the power source (harmonic) at the same time, regardless of the magnitude of the AC input voltage There is an effect that can be reduced.

The above description is only a description of specific embodiments of the present invention, and the present invention is not limited to these specific embodiments, and various changes and modifications of the configuration are possible from the above-described specific embodiments of the present invention. It will be apparent to those skilled in the art to which the present invention pertains.

Claims (6)

In the power converter having a transformer 35 for reducing the input power to the ratio of the primary winding coil (WC1) and the secondary winding coil (WC2), A full-wave rectifier 31 for full-wave rectifying AC power; A half-wave rectifier 32 connected to the full-wave rectifier 31 in parallel for half-wave rectifying the AC power; A smoothing capacitor C1 connected to the output terminal of the full wave rectifying unit 31 to smooth the output waveform of the full wave rectifying unit 31; The waveform of the input current is adjusted by the difference voltage between the output voltage of the full wave rectifier 31 and the voltage V1 of the smoothing capacitor C1, and the output voltage of the full wave rectifier 31 and the primary winding coil ( A power factor correction unit 33 for adjusting the waveform of the input current by the difference voltage of the midpoint voltage V2 of the WC1; And Harmonics that reduce the harmonics of the input current by adjusting the waveform of the input current by controlling the waveform of the input current by the difference voltage between the voltage V3 of the smoothing capacitor C1 and the voltage V3 obtained by depressing a predetermined magnitude and the output voltage of the full-wave rectifier 31 Reduction part (34) Power converter comprising a. The power factor correction unit 33 of claim 1, wherein A first diode (D1) having an anode terminal connected to the first half-wave output point (P1) of the full wave rectifying unit (31) and a cathode terminal connected to the smoothing capacitor (C1); A first filter capacitor (C2) connected between an anode end of the first diode (D1) and a second half-wave output point (P2) of the full wave rectifier (31); A second filter capacitor (C3) connected between an output point (P3) of the half-wave rectifier (32) and a second half-wave output point (P2) of the full-wave rectifier (31); A power factor correction coil L1 having one end connected to an output point P3 of the half-wave rectifier 32; And Second diode D2 having an anode terminal connected to the other end of the power factor correction coil L1 and a cathode terminal connected to the neutral point MP of the primary winding coil WC1. Power converter comprising a. The method of claim 1, wherein the harmonic reduction unit 34 A high frequency reduction coil L2 having one end connected to a first output point P1 of the full wave rectifying unit 31; A third diode (D3) having an anode end connected to the other end of the high frequency reduction coil (L2); And Auxiliary winding coil (Waux) is connected between the cathode end of the third diode (D3) and one side of the primary winding coil (WC1), and wound in a direction opposite to the winding direction of the primary winding coil (WC1) Power converter comprising a. The method of claim 3, wherein the power converter It further includes a breakdown voltage processing unit 37 for providing energy of the power factor correction coil L1 to the secondary winding coil WC2 side. The pressure resistant processing unit 37 A fifth coil L5 connected to one end of an output terminal of the transformer 35 and releasing power from the power factor correction coil L1 of the power factor correction unit 33; A fifth diode D5 having an anode connected to the other end of the fifth coil L5 and a cathode connected to the other end of the output terminal of the transformer 35; Power converter comprising a. In the power converter having a transformer 35 for reducing the input power to the ratio of the primary winding coil (WC1) and the secondary winding coil (WC2), A full-wave rectifier 31 for full-wave rectifying AC power; A half-wave rectifier 32 connected to the full-wave rectifier 31 in parallel for half-wave rectifying the AC power; A smoothing capacitor C1 connected to the output terminal of the full wave rectifying unit 31 to smooth the output waveform of the full wave rectifying unit 31; A first diode (D1) having an anode terminal connected to the first half-wave output point (P1) of the full wave rectifying unit (31) and a cathode terminal connected to the smoothing capacitor (C1); A first filter capacitor (C2) connected between an anode end of the first diode (D1) and a second half-wave output point (P2) of the full wave rectifier (31); A second filter capacitor (C3) connected between an output point (P3) of the half-wave rectifier (32) and a second half-wave output point (P2) of the full-wave rectifier (31); A power factor correction coil L1 having one end connected to an output point P3 of the half-wave rectifier 32; A second diode (D2) having an anode terminal connected to the other end of the power factor correction coil (L1) and a cathode terminal connected to the neutral point (MP) of the primary winding coil (WC1); A high frequency reduction coil L2 having one end connected to a first output point P1 of the full wave rectifying unit 31; A third diode (D3) having an anode end connected to the other end of the high frequency reduction coil (L2); And Auxiliary winding coil (Waux) is connected between the cathode end of the third diode (D3) and one side of the primary winding coil (WC1), and wound in a direction opposite to the winding direction of the primary winding coil (WC1) Power converter comprising a. The method of claim 5, wherein the power converter It further includes a breakdown voltage processing unit 37 for providing energy of the power factor correction coil L1 to the secondary winding coil WC2 side. The pressure resistant processing unit 37 A fifth coil L5 connected to one end of an output terminal of the transformer 35 and releasing power from the power factor correction coil L1 of the power factor correction unit 33; A fifth diode D5 having an anode connected to the other end of the fifth coil L5 and a cathode connected to the other end of the output terminal of the transformer 35; Power converter comprising a.