A wide load power factor correction circuit and power module

Abstract

This invention belongs to the field of power factor correction technology for switching power supplies, specifically relating to a wide-load power factor correction circuit and power module. It includes a rectifier circuit, the input of which is connected to the power supply; and a π-type filter network comprising a first valley-fill circuit, an energy storage inductor, and a second valley-fill circuit connected in series. The input of the first valley-fill circuit is connected to the output of the rectifier circuit, and the output of the second valley-fill circuit is connected to the load. This invention addresses the problem of a narrow power factor correction range. By widening the conduction angle through a double valley-fill structure and combining it with a π-type filter network to suppress high-frequency harmonics and optimize the current waveform, the input current is made closer to a sine wave. Actual measurements show that the power factor remains between 0.91 and 0.95 within a range from full load to 10% light load, without requiring additional control chips, as all components are passive, significantly improving reliability. Compared to active PFC circuits, it offers a clear cost advantage.

Description

Technical Field

[0001] This invention belongs to the field of power factor correction technology for switching power supplies, specifically relating to a power factor correction circuit and power module with wide load range. Background Technology

[0002] Power factor correction (PFC) is an important means to improve the efficiency of electronic devices in utilizing electrical energy and reduce harmonic pollution in the power grid. Currently, PFC technology is mainly divided into two categories: active PFC and passive PFC.

[0003] Active PFC circuits mainly consist of switching transistors, inductors, and dedicated control ICs. They rectify the AC mains voltage and boost it to a DC high voltage of approximately 390-400V, adaptable to AC input voltages across the entire spectrum. However, active PFC has an inherent drawback: its power factor decreases significantly as the load decreases, severely impacting power quality under light load conditions. This limitation restricts the application of active PFC circuits in applications with frequently changing loads (such as dimming LED drivers and multi-mode operating equipment).

[0004] Passive PFC circuits utilize passive components such as inductors, capacitors, and diodes, offering advantages such as simple structure, low cost, and high reliability. Valley-fill passive PFC circuits are among the most common topologies. Several improved solutions for passive PFC circuits exist. However, these existing solutions primarily focus on improving the absolute value of the power factor, failing to address the issue of maintaining a high and stable power factor over a wide load range. The power factor of traditional valley-fill circuits is typically between 0.7 and 0.9, and it decreases significantly as the load decreases, making it unsuitable for applications requiring high load adaptability.

[0005] The output adjustment of lighting equipment (such as lamps, displays, etc.) is frequent and constant, and the power factor (PF value) directly affects the efficiency of electrical energy. How to achieve a passive PFC circuit that maintains a high and stable power factor over a wide load range without significantly increasing cost and complexity has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the shortcomings of existing technologies, a power factor correction circuit and power module with a wide load range are provided to solve the problem of a narrow power factor correction range.

[0007] On the one hand, the technical solution of the present invention to solve the above-mentioned technical problems is as follows: a power factor correction circuit with wide load range, comprising: A rectifier circuit, whose input terminal is connected to the power supply; The π-type filter network includes a first valley filler circuit, an energy storage inductor, and a second valley filler circuit connected in series. The input terminal of the first valley filler circuit is connected to the output terminal of the rectifier circuit, and the output terminal of the second valley filler circuit is connected to the load.

[0008] Compared with existing technologies, the above technical solutions have the following beneficial effects: This circuit widens the conduction angle through a double valley-fill structure, and combines a π-type filter network to suppress high-frequency harmonics and optimize the current waveform, making the input current closer to a sine wave. Actual measurements show that the power factor remains between 0.91 and 0.95 within a range from full load to 10% light load. Furthermore, it requires no additional control chip, as all components are passive, significantly improving reliability. Compared to active PFC circuits, it offers a clear cost advantage.

[0009] Based on the above technical solution, the embodiments of this application can be further improved as follows: In one embodiment, the first valley-filling circuit includes: a first capacitor C1, a second capacitor C2, a first diode D1, a second diode D2, and a third diode D3; The first capacitor C1 is connected in series with the first diode D1 and then connected in parallel between the positive and negative output terminals of the rectifier circuit. The third diode D3 is connected in series with the second capacitor C2 and then connected in parallel between the positive and negative output terminals of the rectifier circuit. The anode of the second diode D2 is connected to the first series node between the first capacitor C1 and the first diode D1, and the cathode is connected to the second series node between the third diode D3 and the second capacitor C2; The anode of the first diode D1 is connected to the negative output terminal of the rectifier circuit, and the cathode is connected to the first series node; The output terminal of the first valley filling circuit is the cathode of the third diode D3.

[0010] In one embodiment, the second valley-filling circuit includes: a third capacitor C3, a fourth capacitor C4, a fourth diode D4, a fifth diode D5, and a sixth diode D6; The third capacitor C3 and the fourth diode D4 are connected in series and then connected between the positive and negative terminals of the load. The sixth diode D6 and the fourth capacitor C4 are connected in series and then connected between the positive and negative terminals of the load. The anode of the fifth diode D5 is connected to the third series node between the third capacitor C3 and the fourth diode D4, and the cathode is connected to the fourth series node between the sixth diode D6 and the fourth capacitor C4. The anode of the fourth diode D4 is connected to the negative output terminal of the rectifier circuit, and the cathode is connected to the third series node; the output terminal of the second valley fill circuit is the cathode of the sixth diode D6.

[0011] In one embodiment, the inductance value of the energy storage inductor ranges from 0.5mH to 10mH.

[0012] In one embodiment, the rectifier circuit is a rectifier bridge.

[0013] In one embodiment, a protection circuit is also connected between the input terminal of the rectifier circuit and the power supply. The protection circuit includes overcurrent protection units connected in series with the positive and negative terminals of the power supply, respectively.

[0014] On the other hand, this embodiment also discloses a power module that includes a power factor correction circuit with a wide load as described above.

[0015] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages: 1. High and stable power factor over a wide load range: The passive PFC circuit achieves a power factor between 0.91 and 0.95 when the load is between 10% and full load. This allows the passive PFC circuit to replace the active PFC circuit and achieve a superior power factor. It is widely used in cost-sensitive applications and where high power factor is crucial, such as consumer electronics, small appliance power supplies, LED lighting drivers, TV standby power supplies, and chargers. Its high and stable power factor over a wide load range makes it particularly suitable for scenarios with frequently changing loads.

[0016] 2. Synergistic effect of π-type filter network: The two valley-filling circuits and the intermediate energy storage inductor work together to not only smooth the current waveform, but more importantly, maintain the relative stability of the circuit impedance characteristics when the load changes. When the load is reduced, the freewheeling effect of the energy storage inductor and the energy release of the two-stage valley-filling circuits compensate each other, achieving power factor stability over a wide load range.

[0017] 3. Simple structure and low cost: It is composed of only passive components and does not require any active control chips or complex circuits, which greatly reduces material costs and design complexity.

[0018] 4. Extremely high reliability: The entire circuit is composed of passive components such as diodes, capacitors, and inductors, eliminating switching losses and controller failure risks. It has a long lifespan and is suitable for applications with stringent reliability requirements, such as consumer electronics, small household appliance power supplies, and LED lighting.

[0019] 5. Reduce total harmonic distortion: The π-type filter network has a dual smoothing effect on the current waveform, making the input current waveform closer to a sine wave, significantly reducing harmonic content and minimizing power grid pollution. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 This is a circuit diagram of the present invention.

[0022] Figure 2 This is a comparison curve of the power factor changes of the circuit in this invention and the active PFC circuit.

[0023] Figure 3 This is a schematic diagram comparing the AC input current waveform under 10% load in this invention. Detailed Implementation

[0024] The embodiments of the technical solution of the present invention will now be described in detail with reference to the accompanying drawings. These embodiments are merely illustrative of the technical solution of the present invention and are therefore intended to limit the scope of protection of the present invention. It should be noted that, unless otherwise stated, the technical or scientific terms used in this application should have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0025] In the description of this application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the present invention.

[0026] Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly defined.

[0027] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0028] Example 1 like Figure 1 As shown, the present invention provides a wide-load power factor correction circuit, which includes: a rectifier circuit, a π-type filter network and a load. The π-type filter network is located between the output terminal of the rectifier bridge and the load, and the input terminal of the rectifier circuit is connected to the power supply.

[0029] The π-type filter network includes a first valley filler circuit, an energy storage inductor L2, and a second valley filler circuit connected in series. The input terminal of the first valley filler circuit is connected to the output terminal of the rectifier circuit, and the output terminal of the second valley filler circuit is connected to the load.

[0030] The first valley filling circuit and the second valley filling circuit are both passive valley filling circuits, each including a valley filling topology consisting of at least two capacitors and at least three diodes.

[0031] By widening the conduction angle through a double valley-filling structure and combining it with a π-type filter network to suppress high-frequency harmonics and optimize the current waveform, the input current is made closer to a sine wave. Actual measurements show that the power factor remains between 0.91 and 0.95 within a range from full load to 10% light load. Furthermore, no additional control chip is required, as all components are passive, significantly improving reliability. Compared to active PFC circuits, it offers a clear cost advantage.

[0032] Specifically, the first valley-filling circuit includes: a first capacitor C1, a second capacitor C2, a first diode D1, a second diode D2, and a third diode D3; The first capacitor C1 is connected in series with the first diode D1 and then connected in parallel between the positive and negative output terminals of the rectifier circuit. The third diode D3 is connected in series with the second capacitor C2 and then connected in parallel between the positive and negative output terminals of the rectifier circuit. The anode of the second diode D2 is connected to the first series node between the first capacitor C1 and the first diode D1, and the cathode is connected to the second series node between the third diode D3 and the second capacitor C2; The anode of the first diode D1 is connected to the negative output terminal of the rectifier circuit, and the cathode is connected to the first series node; The output terminal of the first valley filling circuit is the cathode of the third diode D3.

[0033] In one embodiment, the second valley-filling circuit includes: a third capacitor C3, a fourth capacitor C4, a fourth diode D4, a fifth diode D5, and a sixth diode D6; The third capacitor C3 and the fourth diode D4 are connected in series and then connected between the positive and negative terminals of the load. The sixth diode D6 and the fourth capacitor C4 are connected in series and then connected between the positive and negative terminals of the load. The anode of the fifth diode D5 is connected to the third series node between the third capacitor C3 and the fourth diode D4, and the cathode is connected to the fourth series node between the sixth diode D6 and the fourth capacitor C4. The anode of the fourth diode D4 is connected to the negative output terminal of the rectifier circuit, and the cathode is connected to the third series node; the output terminal of the second valley fill circuit is the cathode of the sixth diode D6, and is connected to the positive terminal of the load.

[0034] Actual measurements show that the passive PFC circuit of this invention has a power factor (PF) of approximately 0.95 under full load, approximately 0.945 under 75% load, approximately 0.938 under half load, approximately 0.925 under 25% load, and approximately 0.91 under 10% load. Under the same conditions, the active PFC circuit has a PF of approximately 0.956 under full load, which decreases to approximately 0.86 under 75% load, approximately 0.7 under half load, approximately 0.48 under 20% load, and approximately 0.39 under 10% load. This comparative measurement demonstrates… Figure 3 As shown in the figure, the current waveforms at the AC input terminals of both circuits are schematic diagrams under 10% load. According to circuit theory, the closer the current waveform is to a sine wave and the smaller the phase difference with the voltage, the higher the power factor. Therefore, the passive PFC circuit of this invention is significantly superior to the active PFC circuit.

[0035] The specific measurement data of the passive PFC circuit compared with the active PFC circuit in this embodiment are shown in the table below;

[0036] The data in the table above were obtained using Hangzhou Yuanfang's PF9811 intelligent electrical parameter tester under the same load and conditions with an input AC voltage of 220V. A curve comparison chart is plotted from the table above. Figure 2 As shown.

[0037] The inductance value of the energy storage inductor L2 ranges from 0.5mH to 10mH, and the specific value is determined according to the load power.

[0038] Specific working principle: The operation of the circuit of this invention can be divided into the following stages: 1. Charging stage: When the rectified voltage is higher than the voltage of each capacitor, the current charges the capacitors C3 and C4 of the second valley filling circuit through the energy storage inductor L2, and at the same time supplies power to the load. The capacitors C1 and C2 of the first valley filling circuit are also in the charging state.

[0039] There are two specific charging paths: The first path is: BR1→C1→D2→C2→BR1; The second path is: BR1→L2→C3→D5→C4→BR1; 2. Freewheeling Stage: When the rectified voltage drops, the energy storage inductor L2 reverses its potential polarity to maintain current continuity, releasing energy through the freewheeling path. Simultaneously, the capacitors in the first and second valley-filling circuits begin to discharge, jointly maintaining the load current.

[0040] There are four specific discharge paths: The first path is: C1→L2→Load→D1→C1; The second path is: C2→D3→L2→Load→C2; The third path is: C3→Load→D4→C3; The fourth path is: C4→D6→Load→C4; 3. Synergistic effect of the π-type filter network: The first valley-filling circuit performs initial smoothing of the rectified output, the energy storage inductor L2 performs secondary smoothing of the current, and the second valley-filling circuit performs tertiary smoothing of the output voltage. This three-stage smoothing structure forms a π-type filter network, making the current flowing to the load highly smooth, almost pure DC.

[0041] The principle of wide load stability is achieved in this embodiment: the π-type filter network composed of the double valley filling circuit and the intermediate energy storage inductor L2 not only realizes multiple smoothing of the current waveform, but more importantly, it generates a synergistic compensation effect when the load changes.

[0042] When the load decreases from full load to light load: the freewheeling time of the energy storage inductor L2 is extended, which compensates for the current discontinuity caused by the decrease in load current. The discharge time constant of the energy storage capacitor in the two-stage valley-filling circuit is increased, which maintains the stability of the output voltage. The three components work together to ensure that the input current waveform always maintains a full sine wave shape under different load conditions, thereby achieving power factor stability across the entire load range.

[0043] In this embodiment, a protection circuit is also connected between the input terminal of the rectifier circuit and the power supply. The protection circuit includes an overcurrent protection unit connected in series with the positive and negative terminals of the power supply. The overcurrent protection unit is a fuse F1 and a thermistor NTC, which are connected in series with the live wire and the neutral wire of the power supply, respectively. The fuse provides overcurrent protection. When the current is too large, it melts and cuts off the power supply to protect the downstream circuit from being burned out. The thermistor NTC is mainly used to suppress the surge current of the main circuit of the line at the moment of power-on.

[0044] A common-mode inductor L1 is also connected between the protection circuit and the rectifier circuit. The AC power enters the rectifier bridge through the common-mode inductor L1. The common-mode inductor can suppress common-mode interference and filter out interference signals of the same direction to ground on the live wire and neutral wire. A varistor VR1 is connected to the output terminal of the common-mode inductor L1. It is used to prevent overvoltage at the input terminal. When the voltage exceeds its rated value, the resistance drops sharply, forming a large current that causes the fuse to blow, thereby protecting the subsequent circuit.

[0045] The rectifier circuit is a rectifier bridge that converts AC to DC. It converts the "clean" AC power, which has been processed by the EMI circuit formed by the fuse, common-mode inductor and varistor, into pulsating DC power through the bridge connection of internal diodes.

[0046] Example 2 This embodiment also discloses a power supply module, which includes a wide-load power factor correction circuit as described in Embodiment 1 above.

[0047] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A power factor correction circuit with wide load range, characterized in that, include: A rectifier circuit, whose input terminal is connected to the power supply; The π-type filter network includes a first valley filler circuit, an energy storage inductor, and a second valley filler circuit connected in series. The input terminal of the first valley filler circuit is connected to the output terminal of the rectifier circuit, and the output terminal of the second valley filler circuit is connected to the load.

2. The power factor correction circuit for wide loads according to claim 1, characterized in that, The first valley-filling circuit includes: a first capacitor C1, a second capacitor C2, a first diode D1, a second diode D2, and a third diode D3; The first capacitor C1 is connected in series with the first diode D1 and then connected in parallel between the positive and negative output terminals of the rectifier circuit. The third diode D3 is connected in series with the second capacitor C2 and then connected in parallel between the positive and negative output terminals of the rectifier circuit. The anode of the second diode D2 is connected to the first series node between the first capacitor C1 and the first diode D1, and the cathode is connected to the second series node between the third diode D3 and the second capacitor C2; The anode of the first diode D1 is connected to the negative output terminal of the rectifier circuit, and the cathode is connected to the first series node; The output terminal of the first valley filling circuit is the cathode of the third diode D3.

3. The power factor correction circuit for wide loads according to claim 1, characterized in that, The second valley-filling circuit includes: a third capacitor C3, a fourth capacitor C4, a fourth diode D4, a fifth diode D5, and a sixth diode D6; The third capacitor C3 and the fourth diode D4 are connected in series and then connected between the positive and negative terminals of the load. The sixth diode D6 and the fourth capacitor C4 are connected in series and then connected between the positive and negative terminals of the load. The anode of the fifth diode D5 is connected to the third series node between the third capacitor C3 and the fourth diode D4, and the cathode is connected to the fourth series node between the sixth diode D6 and the fourth capacitor C4. The anode of the fourth diode D4 is connected to the negative output terminal of the rectifier circuit, and the cathode is connected to the third series node; the output terminal of the second valley fill circuit is the cathode of the sixth diode D6.

4. The power factor correction circuit for wide loads according to claim 1, characterized in that, The inductance value of the energy storage inductor ranges from 0.5mH to 10mH.

5. The power factor correction circuit for wide loads according to claim 1, characterized in that, The rectifier circuit is a rectifier bridge.

6. The power factor correction circuit for wide loads according to claim 1, characterized in that, A protection circuit is also connected between the input terminal of the rectifier circuit and the power supply. The protection circuit includes overcurrent protection units connected in series with the positive and negative terminals of the power supply, respectively.

7. A power supply module, characterized in that, Includes a power factor correction circuit with wide load as described in any one of claims 1-6.

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