A single-stage PFC power supply circuit

Abstract

This invention belongs to the field of switching power supply conversion technology, and provides a single-stage PFC power supply circuit, including an EMI filter module, a composite rectifier module, an energy feedback module, an energy storage capacitor C1, a first switching element Q1, a second switching element Q2, an energy storage inductor Lr, a resonant capacitor Cr, a transformer T1, and a secondary rectifier module. One end of the energy feedback module is connected between the composite rectifier module and the energy storage inductor Lr, and the other end is connected to the energy storage capacitor C1. During the conduction of the first switching element Q1 and its transmission to the secondary output, the operating state is cleverly adjusted by utilizing a resonant circuit. By incorporating the diode junction capacitance in the composite rectifier module and the energy feedback module into the resonant path, a bidirectional resonant current cycle is formed: the positive current charges the junction capacitance, and the negative current transfers energy to the feedback module, realizing dynamic compensation for the resonant capacitor and the load, effectively reducing the resonant frequency and voltage peak value, and improving the stability and reliability of the power supply output.

Description

Technical Field

[0001] This invention belongs to the field of switching power supply conversion technology, specifically relating to a single-stage PFC power supply circuit. Background Technology

[0002] In power supplies with a power rating greater than 75W, it is generally necessary to meet the standard requirements for harmonic current. Therefore, a power factor correction (PF) section is commonly added to the power supply. In practical applications, electrical equipment needs to be isolated from the power grid to ensure the safety and stability of the equipment and personal safety. To meet these requirements, the power supply typically adopts a two-stage voltage conversion structure. The first stage is usually a BOOST-type active PFC AC-to-high voltage DC conversion circuit, and the second stage is an isolated high voltage DC-to-low voltage DC conversion circuit. This two-stage voltage conversion power supply uses switching devices in both the first and second stages, resulting in a large number of switching devices, high switching losses, and, due to the numerous electronic components, complex circuitry, larger power supply size, and higher cost.

[0003] To address this, existing technologies generally employ single-stage isolated PFC technology. For example, a single-stage isolated PFC circuit using a single switching topology produces a power output with significant power frequency voltage ripple, failing to meet the voltage accuracy requirements of many electrical devices. Therefore, it is necessary to combine two or more switching topologies to achieve both high power factor and low voltage ripple. While this combination uses only a single control circuit, achieving the functions of both topologies through multiplexing switching devices, this approach leads to mutual interference between the two topologies during operation due to the single control, resulting in increased harmonics, decreased power factor, and reduced power output stability and reliability. Summary of the Invention

[0004] The purpose of this invention is to disclose a single-stage PFC power supply circuit that solves the comprehensive technical defects of existing single-stage or two-stage isolated PFC circuits, such as low efficiency, high size and cost, high voltage stress, strong electromagnetic interference and poor output stability, making it difficult to simultaneously meet the design requirements of high power factor, high efficiency and compact reliability.

[0005] To achieve the above objectives, the present invention discloses a single-stage PFC power supply circuit, including an EMI filter module, a composite rectifier module, an energy feedback module, an energy storage capacitor C1, a first switching element Q1, a second switching element Q2, an energy storage inductor Lr, a resonant capacitor Cr, a transformer T1, and a secondary rectifier module. The EMI filter module, composite rectifier module, and energy feedback module are connected in sequence. One end of the energy storage capacitor C1 is connected to the first switching element Q1 and the transformer T1, and the other end is connected to the composite rectifier module. The second switching element Q2 is connected to the energy storage inductor Lr, the resonant capacitor Cr, and the first switching element Q1. The transformer T1 is also connected to the secondary rectifier module. One end of the energy storage inductor Lr is connected to the composite rectifier module; One end of the transformer T1 is connected to the other end of the energy storage inductor Lr through the resonant capacitor Cr; or, one end of the transformer T1 is connected to the resonant capacitor Cr, and the other end is connected to the other end of the energy storage inductor Lr. One end of the energy feedback module is connected between the composite rectifier module and the energy storage inductor Lr, and the other end is connected to the energy storage capacitor C1; Near the zero-crossing point of the AC mains power, the first switching element Q1 is in the conducting state, and the inductive energy stored in the primary winding of transformer T1 is transferred to the secondary output. At this time, the inductive energy stored in the energy storage inductor Lr is released to the energy storage capacitor C1. When the current of the energy storage inductor Lr drops to zero, the energy storage inductor Lr, the first switching element Q1, the diode junction capacitance in the composite rectifier module, and the energy feedback module form a resonant circuit and generate resonance. The positive resonant current flows to the junction capacitance of the diode in the composite rectifier module, and the negative resonant current flows to the energy feedback module to adjust the resonant capacitor and the load. By adjusting the feedback strength of the energy feedback module, the equivalent resonant capacitor and the load on the resonant circuit are adjusted, thereby reducing the resonant frequency and voltage amplitude.

[0006] As an optional implementation, the energy storage capacitor C1, energy storage inductor Lr, composite rectifier module, first switching element Q1, and second switching element Q2 form a BOOST-type power factor correction circuit for performing power factor correction; the energy storage capacitor C1, resonant capacitor Cr, first switching element Q1, second switching element Q2, transformer T1, and secondary rectifier module form an asymmetrical half-bridge flyback isolation converter circuit for electrically isolating the input and output and performing power step-down conversion. When the BOOST power factor correction circuit is working, the primary winding of transformer T1 stores energy. When the asymmetrical half-bridge flyback isolation converter circuit is working, the secondary rectifier module is turned on, and the inductive energy stored in the primary winding of transformer T1 is transferred to the secondary winding. When the energy storage inductor Lr is completely released, the energy storage inductor Lr, the first switching element Q1, the energy storage capacitor C1, the composite rectifier module, and the energy feedback module form a resonant circuit. The positive resonant current flows through the energy storage capacitor C1 to the junction capacitance of the diode in the composite rectifier module, and the negative resonant current flows through the energy storage inductor Lr to the energy feedback module to reduce the resonant capacitance and load.

[0007] As an optional implementation, one end of the energy feedback module is connected to the composite rectifier module and the energy storage inductor Lr, and the other end is connected to the positive terminal of the energy storage capacitor C1 and the first switching element Q1. The energy feedback module includes a diode D1, a resistor R1, a resistor R2, and a capacitor C2; the anode of the diode D1 is connected to the energy storage inductor Lr and the output terminal of the composite rectifier module, and the cathode is connected to one end of the resistor R2; one end of the capacitor C2 is connected to the other end of the resistor R2, and the other end is connected to the anode of the energy storage capacitor C1 and the first switching element Q1; the resistor R2 is connected in parallel with the capacitor C2. When the asymmetric half-bridge flyback isolation converter circuit is working, the secondary rectifier module is turned on. At this time, the negative resonant current flows through resistor R1 to capacitor C2, and the energy feedback module increases the equivalent capacitance and load of the resonant circuit, thereby reducing the resonant frequency and voltage amplitude.

[0008] As an optional implementation, one end of the energy storage inductor Lr is connected to the output terminal of the composite rectifier module, and the other end is connected to the same-name terminal of the primary winding of the transformer T1 through the resonant capacitor Cr. The opposite-name terminal of the primary winding of the transformer T1 is connected to the positive terminal of the energy storage capacitor C1, the first switching element Q1, and the energy feedback module.

[0009] As an optional implementation, one end of the energy feedback module is connected to the composite rectifier module and the energy storage inductor Lr, and the other end is grounded; The energy feedback module 3 includes a diode D2, a resistor R3, a resistor R4, and a capacitor C3; the anode of the diode D2 is grounded, and the cathode of the diode D2 is connected to one end of the resistor R4; one end of the capacitor C3 is connected to the other end of the resistor R4, and the other end of the capacitor C3 is connected to the composite rectifier module 2 and the energy storage inductor Lr; the resistor R3 and the capacitor C3 are connected in parallel. When the asymmetric half-bridge flyback isolation converter circuit is working, the secondary rectifier module is turned on. At this time, the negative resonant current flows through resistor R4 to capacitor C3, and the energy feedback module increases the equivalent capacitance and load of the resonant circuit, thereby reducing the resonant frequency and voltage amplitude.

[0010] As an optional implementation, one end of the energy storage inductor Lr is connected to the output terminal of the composite rectifier module, and the other end is connected to the opposite-named terminals of the first switching element Q1, the second switching element Q2, and the primary winding of the transformer T1; the same-named terminal of the primary winding of the transformer T1 is grounded through the resonant capacitor Cr; the positive terminal of the energy storage capacitor C1 is connected to the first switching element Q1 and the composite rectifier module.

[0011] As an optional implementation, the secondary rectifier module includes a diode D3 and a capacitor C4. The anode of the diode D3 is connected to the power output terminal VO+, and the cathode of the diode D3 is connected to the opposite terminal of the secondary winding of the transformer T1. The same terminal of the secondary winding of the transformer T1 is connected to the positive terminal of the capacitor C4 and the power output terminal VO-. The negative terminal of the capacitor C4 is connected to the power output terminal VO-.

[0012] As an optional implementation, the first switching element Q1 includes an N-channel MOSFET and the second switching element Q2 includes an N-channel MOSFET.

[0013] As an optional implementation, the EMI filtering module includes a capacitor CX1, a common-mode inductor LF1, a differential-mode inductor L1, and a capacitor CX2 connected in sequence.

[0014] As an optional implementation, the composite rectifier module includes diodes D4, D5, D6, and D7; diodes D4, D5, D6, and D7 are connected in series in pairs to form a single-phase bridge rectifier.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: During the period when the first switching element Q1 is turned on and transmits to the secondary output, the working state is cleverly adjusted by using a resonant circuit. By incorporating the diode junction capacitance in the composite rectifier module and the energy feedback module into the resonant path, a bidirectional resonant current cycle is formed: the positive current charges the junction capacitance, and the negative current transfers energy to the feedback module, thereby realizing dynamic compensation for the resonant capacitor and the load, effectively reducing the resonant frequency and voltage peak, and improving the stability and reliability of the power supply output. A BOOST-type power factor correction circuit is formed by using energy storage capacitor C1, energy storage inductor Lr, composite rectifier module, first switching element Q1, and second switching element Q2; an asymmetric half-bridge flyback isolation converter circuit is formed by using energy storage capacitor C1, resonant capacitor Cr, first switching element Q1, second switching element Q2, transformer T1, and secondary rectifier module. Thus, a single-stage PFC power supply circuit is formed, which efficiently integrates power factor correction and isolation conversion through an innovative single-stage resonant topology. By utilizing resonant soft-switching technology, switching efficiency and reliability are improved by reducing switching losses and voltage stress, while electromagnetic interference is suppressed, enabling the system to maintain stable and efficient soft-switching characteristics over a wide load range. It significantly reduces the number of switching devices and switching losses, while improving conversion efficiency and simplifying the circuit architecture, effectively reducing the size and cost of the power supply. The unique resonant modulation mechanism solves the problems of large voltage ripple and low accuracy in traditional single-stage PFC, while avoiding the problem of mutual interference in multi-topology combinations. Ultimately, a balance between low voltage stress, low electromagnetic interference, and high power factor was achieved, maintaining stable and reliable output over a wide voltage input range and comprehensively optimizing power supply performance. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a system framework diagram of a single-stage PFC power supply circuit provided in Embodiment 1 of the present invention; Figure 2 This is provided in Embodiment 1 of the present invention. Figure 1 Hardware circuit diagram; Figure 3 This is a waveform diagram of the key working waveforms provided in Embodiment 1 of the present invention without the addition of an energy feedback circuit; Figure 4 This is a waveform diagram of the key working waveforms when adding energy feedback circuit according to Embodiment 1 of the present invention; Figure 5 This is a system framework diagram of a single-stage PFC power supply circuit provided in Embodiment 2 of the present invention; Figure 6 This is provided in Embodiment 2 of the present invention. Figure 5 Hardware circuit diagram; Icons: EMI filter module 1, composite rectifier module 2, energy feedback module 3, secondary rectifier module 4. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] In this invention, the terms "upper," "lower," "left," "right," "front," "rear," "top," "bottom," "inner," "outer," "middle," "vertical," "horizontal," "lateral," and "longitudinal" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are primarily for the purpose of better describing the invention and its embodiments, and are not intended to limit the indicated devices, elements, or components to having a specific orientation, or to be constructed and operated in a specific orientation.

[0020] Furthermore, in addition to indicating direction or positional relationship, some of the aforementioned terms may also have other meanings. For example, the term "above" may also be used in certain situations to indicate a dependency or connection. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0021] Furthermore, the terms "installation," "setup," "equipped with," "connection," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral structure; 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, or an internal connection between two devices, components, or parts. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0022] Furthermore, the terms "first," "second," etc., are primarily used to distinguish different devices, components, or parts (which may be the same or different in specific type and construction), and are not intended to indicate or imply the relative importance or quantity of the indicated devices, components, or parts. Unless otherwise stated, "a plurality of" means two or more.

[0023] The technical solution of the present invention will be further described below with reference to the embodiments and accompanying drawings.

[0024] Example 1 Please see Figure 1 and Figure 2 As shown, this application embodiment provides a single-stage PFC power supply circuit, including an EMI filter module 1, a composite rectifier module 2, an energy feedback module 3, an energy storage capacitor C1, a first switching element Q1, a second switching element Q2, an energy storage inductor Lr, a resonant capacitor Cr, a transformer T1, and a secondary rectifier module 4. The EMI filter module 1, the composite rectifier module 2, and the energy feedback module 3 are connected in sequence. One end of the energy storage capacitor C1 is connected to the first switching element Q1 and the transformer T1, and the other end is connected to the composite rectifier module 2. The second switching element Q2 is connected to the energy storage inductor Lr, the resonant capacitor Cr, and the first switching element Q1. The transformer T1 is also connected to the secondary rectifier module 4. One end of the energy storage inductor Lr is connected to the composite rectifier module 2; One end of the transformer T1 is connected to the other end of the energy storage inductor Lr through the resonant capacitor Cr; or, one end of the transformer T1 is connected to the resonant capacitor Cr, and the other end is connected to the other end of the energy storage inductor Lr. One end of the energy feedback module 3 is connected between the composite rectifier module 2 and the energy storage inductor Lr, and the other end is connected to the energy storage capacitor C1; Near the zero-crossing point of the AC mains power, the first switching element Q1 is in the conducting state, and the inductive energy stored in the primary winding of transformer T1 is transferred to the secondary output. At this time, the inductive energy stored in the energy storage inductor Lr is released to the energy storage capacitor C1. When the current of the energy storage inductor Lr drops to zero, the energy storage inductor Lr, the first switching element Q1, the diode junction capacitance in the composite rectifier module 2, and the energy feedback module 3 form a resonant circuit and generate resonance. The positive resonant current flows to the junction capacitance of the diode in the composite rectifier module 2, and the negative resonant current flows to the energy feedback module 3 to adjust the resonant capacitor and the load. By adjusting the feedback strength of the energy feedback module 3, the equivalent resonant capacitor and the load on the resonant circuit are adjusted, thereby reducing the resonant frequency and voltage amplitude.

[0025] In this embodiment, the resonant module includes an energy storage inductor Lr and a resonant capacitor Cr; The energy storage capacitor C1, energy storage inductor Lr, composite rectifier module 2, first switching element Q1, and second switching element Q2 form a BOOST-type power factor correction circuit for performing power factor correction; the energy storage capacitor C1, resonant capacitor Cr, first switching element Q1, second switching element Q2, transformer T1, and secondary rectifier module 4 form an asymmetrical half-bridge flyback isolation converter circuit for electrically isolating the input and output and performing power step-down conversion. When the BOOST power factor correction circuit is working, the primary winding of transformer T1 stores energy. When the asymmetrical half-bridge flyback isolation converter circuit is working, the secondary rectifier module 4 is turned on, and the inductive energy stored in the primary winding of transformer T1 is transferred to the secondary winding. When the energy storage inductor Lr is completely released, the energy storage inductor Lr, the first switching element Q1, the energy storage capacitor C1, the composite rectifier module 2, and the energy feedback module 3 form a resonant circuit. The positive resonant current flows through the energy storage capacitor C1 to the junction capacitance of the diode in the composite rectifier module 2, and the negative resonant current flows through the energy storage inductor Lr to the energy feedback module 3 to reduce the resonant capacitance and load.

[0026] The energy storage inductor Lr is preferably a differential-mode inductor. The inductance of the energy storage inductor Lr is set to enable the circuit to operate in a critical continuous state and a discontinuous state. Therefore, within half a cycle of the AC mains power, the peak current of the energy storage inductor Lr in each operating cycle will automatically track the AC voltage. The peak inductor current is always twice the average current, which means that the average input current will also automatically follow the input voltage, thus achieving the power factor correction function.

[0027] In this embodiment, one end of the energy feedback module 3 is connected to the composite rectifier module 2 and the energy storage inductor Lr, and the other end is connected to the positive terminal of the energy storage capacitor C1 and the first switching element Q1. The energy feedback module 3 includes a diode D1, a resistor R1, a resistor R2, and a capacitor C2; the anode of the diode D1 is connected to the energy storage inductor Lr and the output terminal of the composite rectifier module 2, and the cathode is connected to one end of the resistor R2; one end of the capacitor C2 is connected to the other end of the resistor R2, and the other end is connected to the anode of the energy storage capacitor C1 and the first switching element Q1; the resistor R2 is connected in parallel with the capacitor C2. When the asymmetric half-bridge flyback isolation converter circuit is working, the secondary rectifier module 4 is turned on. At this time, the negative resonant current flows through the resistor R1 to the capacitor C2, and increases the equivalent capacitance and load of the resonant circuit through the energy feedback module 3 (by adjusting the values ​​of the resistor R2 and the capacitor C2 in the energy feedback module 3 to increase the equivalent capacitance and load of the resonant circuit), thereby reducing the resonant frequency and voltage amplitude.

[0028] Specifically, the asymmetrical half-bridge flyback isolation converter circuit still transfers energy to the output. During the period after the energy stored in the energy storage inductor Lr in the BOOST power factor correction circuit is released, a portion of the resonant energy is fed back to the energy storage capacitor C1 due to the high-frequency resonance generated by the junction capacitance of the energy storage inductor Lr and the diode in the composite rectifier circuit, as well as the energy feedback module. This energy feedback circuit effectively changes the resonant capacitance and load, reducing the resonant frequency and voltage amplitude. This solves the problem of high voltage stress and large electromagnetic interference caused by mutual interference in the single-stage PFC circuit implemented by combining the functions of the two conversion topologies. The composite rectifier circuit performs the functions of rectifying AC to DC and the high-frequency rectification function of the freewheeling diode in the BOOST power factor correction circuit. When the first switching element Q1 of the asymmetrical half-bridge flyback isolation converter circuit is turned on, the high-frequency current in the energy storage inductor Lr must flow unidirectionally; otherwise, the current cannot track the input voltage, current harmonics increase, and the power factor is low.

[0029] In this embodiment, one end of the energy storage inductor Lr is connected to the output terminal of the composite rectifier module 2, and the other end is connected to the same-name terminal of the primary winding of the transformer T1 through the resonant capacitor Cr. The opposite-name terminal of the primary winding of the transformer T1 is connected to the positive terminal of the energy storage capacitor C1, the first switching element Q1, and the energy feedback module 3.

[0030] In this embodiment, the secondary rectifier module 4 includes a diode D3 and a capacitor C4. The anode of the diode D3 is connected to the power output terminal VO+, and the cathode of the diode D3 is connected to the opposite terminal of the secondary winding of the transformer T1. The same terminal of the secondary winding of the transformer T1 is connected to the positive terminal of the capacitor C4 and the power output terminal VO-. The negative terminal of the capacitor C4 is connected to the power output terminal VO-.

[0031] In this embodiment, the first switching element Q1 includes an N-channel MOSFET and the second switching element Q2 includes an N-channel MOSFET.

[0032] This embodiment of the invention also includes a main controller, which is connected to the first switching element Q1 and the second switching element Q2. Specifically: The main controller includes a first drive terminal VGH and a second drive terminal VGL; The gate of the first switching element Q1 is connected to the first driving terminal VGH, the drain is connected to the opposite terminal of the primary winding of transformer T1, the positive terminal of energy storage capacitor C1, and the energy feedback module 3, and the source is connected between the energy storage inductor Lr and the resonant capacitor Cr. The gate of the second switching element Q2 is connected to the second driving terminal VGL, the drain is connected between the energy storage inductor Lr and the resonant capacitor Cr, and the source is grounded.

[0033] In this embodiment, the EMI filtering module 1 includes a capacitor CX1, a common-mode inductor LF1, a differential-mode inductor L1, and a capacitor CX2 connected in sequence.

[0034] In this embodiment, the composite rectifier module 2 includes diodes D4, D5, D6, and D7; diodes D4, D5, D6, and D7 are connected in series to form a single-phase bridge rectifier bridge.

[0035] The working principle of this embodiment is as follows: I. For example Figure 2 , Figure 3 As shown, when the AC mains power is positive half-cycle, it is rectified into low-frequency pulsating DC power by diodes D4 and D7 of the composite rectifier circuit after passing through the EMI filter circuit. When the input high-level pulse of the second drive terminal VGL is received, the second switching element Q2 is turned on, and the energy storage inductor Lr begins to store energy. The current of the energy storage inductor Lr rises linearly from zero.

[0036] Simultaneously, the inductance of the primary winding NP of transformer T1 stores energy, and the excitation current rises linearly. When the current rises to the set value of the asymmetrical half-bridge flyback converter control circuit, the output of the second drive terminal VGL turns low, the second switching element Q2 turns off, the current of the energy storage inductor Lr continues to flow, and it decreases linearly from the maximum value. This current flows through the diodes D4 and D7 of the composite rectifier circuit and the parasitic diode inside the first switching element Q1, charging the energy storage capacitor C1. The energy stored in the energy storage inductor Lr begins to release, and the voltage across the energy storage capacitor C1 increases.

[0037] After the dead time, the first drive terminal VGH changes from low to high level, and the first switching element Q1 is turned on. At this time, the first switching element Q1 is turned on at zero voltage, the rectifier diode D1 is turned on, and the inductance stored in the primary winding NP of the transformer T1 is transferred to the secondary output. The inductance voltage of the transformer T1 is reversed and clamped by the voltage of the output winding NS. The excitation current decreases linearly, and the leakage inductance of the transformer T1 and the DC isolation coupling capacitor C4 resonate. When the current resonates to zero, the drive of the first drive terminal VGH changes from high level to low level, and the first switching element Q1 is turned off. After the dead time, the drive of the second drive terminal VGL changes from low level to high level. At this time, the second switching element Q2 is turned on at zero voltage, and the energy storage inductor Lr begins to store energy again.

[0038] This process repeats continuously, achieving a highly efficient isolated step-down conversion function from input to output DC voltage.

[0039] II. Figure 3 , Figure 4 This will be explained in conjunction with energy feedback module 3: (1) The key operating waveforms without the added energy feedback circuit are as follows: Figure 4 As shown: VGL is the driving waveform of the second switching element Q2; VGH is the driving waveform of the first switching element Q1; IL is the current waveform of the energy storage inductor Lr; VAC is Figure 3 The voltage waveform between points A and C at the output of the composite rectifier circuit; VBC is Figure 3 The voltage waveform between points B and C on both ends of the energy storage capacitor C1.

[0040] Near the zero-crossing point of the AC mains voltage, the instantaneous voltage is relatively low, the peak current of the energy storage inductor Lr is small, and the inductor stores relatively little energy. The charging of the energy storage capacitor C1 by the inductor will end quickly, within a short time. When the inductor current drops to zero, the first switching element Q1 is still in the conducting state, and the inductor energy stored in the primary winding NP of transformer T1 is still being transferred to the secondary output. The energy storage inductor Lr and the energy storage capacitor C1, together with the first switching element Q1 and the diode junction capacitance in the composite rectifier circuit, form a resonant circuit. At this time, the impedance of the resonant circuit is low, and there is no load, which will form a high-frequency free resonance. High voltage will be generated at the output points A and C of the composite rectifier circuit. This high-frequency, high-voltage voltage will damage the diodes of the composite rectifier circuit and cause strong electromagnetic interference, requiring the addition of an energy feedback circuit to solve the problem.

[0041] (2) The key operating waveforms when the energy feedback circuit is added are as follows: Figure 4 As shown: Near the zero-crossing point of the AC mains voltage, the instantaneous voltage is relatively low, the peak current of the energy storage inductor Lr is relatively small, and the inductor stores relatively little energy. The charging of the energy storage capacitor C1 by the inductor will end quickly, and the time is relatively short. When the inductor current drops to zero, the first switching element Q1 is still in the conducting state, and the inductor energy stored in the primary winding NP of the transformer T1 is still being transferred to the secondary output. The energy storage inductor Lr, the energy storage capacitor C1, the first switching element Q1, the junction capacitance of the diode in the composite rectifier circuit, and the energy feedback circuit form a resonant circuit and load. The positive resonant current mainly flows through the junction capacitance of the diode in the composite rectifier circuit, while the negative resonant current mainly flows to the energy feedback circuit, and a small portion flows to the junction capacitance of the diode in the composite rectifier circuit. This changes the equivalent resonant capacitance and load, thereby reducing the resonant frequency and the resonant voltage amplitude. This solves the problem of high voltage stress and large electromagnetic interference caused by mutual interference in the function of the single-stage PFC circuit implemented by the combination of the two conversion topologies.

[0042] Key working waveforms are as follows Figure 4 As shown, VGL is the driving waveform of the second switching element Q2, VGH is the driving waveform of the first switching element Q1, IL is the current waveform of the energy storage inductor Lr, and VAC is... Figure 2 The voltage waveform between points A and C at the output of the composite rectifier circuit, VBC is... Figure 2 The voltage waveform between points B and C on both ends of the energy storage capacitor C1, compared to the voltage waveform of VAC. Figure 3 Both the resonant frequency and the resonant voltage amplitude decreased.

[0043] Example 2 Please see Figure 5 , Figure 6 As shown, this embodiment of the invention provides a single-stage PFC power supply circuit. The difference between this embodiment and Embodiment 1 is that: In this embodiment, one end of the energy feedback module 3 is connected to the composite rectifier module 2 and the energy storage inductor Lr, and the other end is grounded; The energy feedback module 3 includes a diode D2, a resistor R3, a resistor R4, and a capacitor C3; the anode of the diode D2 is grounded, and the cathode of the diode D2 is connected to one end of the resistor R4; one end of the capacitor C3 is connected to the other end of the resistor R4, and the other end of the capacitor C3 is connected to the composite rectifier module 2 and the energy storage inductor Lr; the resistor R3 and the capacitor C3 are connected in parallel.

[0044] When the asymmetric half-bridge flyback isolation converter circuit is working, the secondary rectifier module 4 is turned on. At this time, the negative resonant current flows through the resistor R4 to the capacitor C3, and increases the equivalent capacitance and load of the resonant circuit through the energy feedback module 3 (by adjusting the values ​​of the resistor R4 and the capacitor C3 in the energy feedback module 3 to increase the equivalent capacitance and load of the resonant circuit), thereby reducing the resonant frequency and voltage amplitude.

[0045] In this embodiment, one end of the energy storage inductor Lr is connected to the output terminal of the composite rectifier module 2, and the other end is connected to the opposite-named terminals of the first switching element Q1, the second switching element Q2, and the primary winding of the transformer T1; the same-named terminal of the primary winding of the transformer T1 is grounded through the resonant capacitor Cr; the positive terminal of the energy storage capacitor C1 is connected to the first switching element Q1 and the composite rectifier module 2.

[0046] This embodiment of the invention also includes a main controller, which is connected to the first switching element Q1 and the second switching element Q2. Specifically: The main controller includes a first drive terminal VGH and a second drive terminal VGL; The gate of the first switching element Q1 is connected to the first driving terminal VGH, the drain is connected to the positive terminal of the energy storage capacitor C1 and the composite rectifier module 2, and the source is connected to the opposite terminal of the primary winding of the transformer T1, the energy storage inductor Lr and the drain of the second switching element Q2. The gate of the second switching element Q2 is connected to the second driving terminal VGL, the drain is connected between the energy storage inductor Lr and the opposite terminal of the primary winding of the transformer T1, and the source is grounded.

[0047] One end of the resonant capacitor Cr is connected to the same terminal of the primary winding of transformer T1, and the other end is grounded.

[0048] The working principle of this embodiment is the same as that of Embodiment 1, and will not be repeated here.

[0049] Compared with the prior art, the beneficial effects of the embodiments of the present invention are as follows: (1) During the period when the first switching element Q1 is turned on and the output is transferred to the secondary, the working state is adjusted by cleverly using the resonant circuit. By incorporating the diode junction capacitance in the composite rectifier module 2 and the energy feedback module 3 into the resonant path, a bidirectional resonant current cycle is formed: the positive current charges the junction capacitance, and the negative current transfers energy to the feedback module, thereby realizing dynamic compensation for the resonant capacitor and the load, effectively reducing the resonant frequency and voltage peak, and improving the stability and reliability of the power supply output. (2) A BOOST-type power factor correction circuit is formed by energy storage capacitor C1, energy storage inductor Lr, composite rectifier module 2, first switching element Q1, and second switching element Q2; an asymmetric half-bridge flyback isolation conversion circuit is formed by energy storage capacitor C1, resonant capacitor Cr, first switching element Q1, second switching element Q2, transformer T1, and secondary rectifier module 4. Thus, a single-stage PFC power supply circuit is formed, which efficiently integrates power factor correction and isolation conversion through an innovative single-stage resonant topology. (3) By utilizing resonant soft-switching technology, the switching efficiency and reliability are improved by reducing switching losses and voltage stress, while suppressing electromagnetic interference, so that the system can maintain stable and efficient soft-switching characteristics over a wide load range. (4) It significantly reduces the number of switching devices and switching losses, while improving conversion efficiency and simplifying the circuit architecture, effectively reducing the size and cost of the power supply. (5) The unique resonant modulation mechanism solves the problems of large voltage ripple and low accuracy in traditional single-stage PFC, while avoiding the problem of mutual interference in multi-topology combinations. Ultimately, a balance between low voltage stress, low electromagnetic interference, and high power factor was achieved, maintaining stable and reliable output over a wide voltage input range and comprehensively optimizing power supply performance.

[0050] The technical means disclosed in this invention are not limited to those disclosed in the above embodiments, but also include technical solutions composed of any combination of the above technical features. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

Claims

1. A single-stage PFC power supply circuit, characterized by: It includes an EMI filter module, a composite rectifier module, an energy feedback module, an energy storage capacitor C1, a first switching element Q1, a second switching element Q2, an energy storage inductor Lr, a resonant capacitor Cr, a transformer T1, and a secondary rectifier module; The EMI filter module, composite rectifier module, and energy feedback module are connected in sequence. One end of the energy storage capacitor C1 is connected to the first switching element Q1 and the transformer T1, and the other end is connected to the composite rectifier module. The second switching element Q2 is connected to the energy storage inductor Lr, the resonant capacitor Cr, and the first switching element Q1. The transformer T1 is also connected to the secondary rectifier module. One end of the energy storage inductor Lr is connected to the composite rectifier module; One end of the transformer T1 is connected to the other end of the energy storage inductor Lr through the resonant capacitor Cr; or, one end of the transformer T1 is connected to the resonant capacitor Cr, and the other end is connected to the other end of the energy storage inductor Lr. One end of the energy feedback module is connected between the composite rectifier module and the energy storage inductor Lr, and the other end is connected to the energy storage capacitor C1; Near the zero-crossing point of the AC mains power, the first switching element Q1 is in the conducting state, and the inductive energy stored in the primary winding of transformer T1 is transferred to the secondary output. At this time, the inductive energy stored in the energy storage inductor Lr is released to the energy storage capacitor C1. When the current of the energy storage inductor Lr drops to zero, the energy storage inductor Lr, the first switching element Q1, the diode junction capacitance in the composite rectifier module, and the energy feedback module form a resonant circuit and generate resonance. The positive resonant current flows to the junction capacitance of the diode in the composite rectifier module, and the negative resonant current flows to the energy feedback module to adjust the resonant capacitor and the load. By adjusting the feedback strength of the energy feedback module, the equivalent resonant capacitor and the load on the resonant circuit are adjusted, thereby reducing the resonant frequency and voltage amplitude.

2. The single-stage PFC power supply circuit as described in claim 1, characterized in that: The energy storage capacitor C1, energy storage inductor Lr, composite rectifier module, first switching element Q1, and second switching element Q2 form a BOOST-type power factor correction circuit for performing power factor correction; the energy storage capacitor C1, resonant capacitor Cr, first switching element Q1, second switching element Q2, transformer T1, and secondary rectifier module form an asymmetrical half-bridge flyback isolation converter circuit for electrically isolating the input and output and performing power step-down conversion. When the BOOST power factor correction circuit is working, the primary winding of transformer T1 stores energy. When the asymmetrical half-bridge flyback isolation converter circuit is working, the secondary rectifier module is turned on, and the inductive energy stored in the primary winding of transformer T1 is transferred to the secondary winding. When the energy storage inductor Lr is completely released, the energy storage inductor Lr, the first switching element Q1, the energy storage capacitor C1, the composite rectifier module, and the energy feedback module form a resonant circuit. The positive resonant current flows through the energy storage capacitor C1 to the junction capacitance of the diode in the composite rectifier module, and the negative resonant current flows through the energy storage inductor Lr to the energy feedback module to reduce the resonant capacitance and load.

3. A single-stage PFC power circuit as recited in claim 1, wherein: One end of the energy feedback module is connected to the composite rectifier module and the energy storage inductor Lr, and the other end is connected to the positive terminal of the energy storage capacitor C1 and the first switching element Q1. The energy feedback module includes a diode D1, a resistor R1, a resistor R2, and a capacitor C2; the anode of the diode D1 is connected to the energy storage inductor Lr and the output terminal of the composite rectifier module, and the cathode is connected to one end of the resistor R2; one end of the capacitor C2 is connected to the other end of the resistor R2, and the other end is connected to the anode of the energy storage capacitor C1 and the first switching element Q1; the resistor R2 is connected in parallel with the capacitor C2. When the asymmetric half-bridge flyback isolation converter circuit is working, the secondary rectifier module is turned on. At this time, the negative resonant current flows through resistor R1 to capacitor C2, and the energy feedback module increases the equivalent capacitance and load of the resonant circuit, thereby reducing the resonant frequency and voltage amplitude.

4. A single-stage PFC power circuit as recited in claim 1, characterized by: One end of the energy feedback module is connected to the composite rectifier module and the energy storage inductor Lr, and the other end is grounded. The energy feedback module includes a diode D2, a resistor R3, a resistor R4, and a capacitor C3; the anode of the diode D2 is grounded, and the cathode of the diode D2 is connected to one end of the resistor R4; one end of the capacitor C3 is connected to the other end of the resistor R4, and the other end of the capacitor C3 is connected to the composite rectifier module and the energy storage inductor Lr; the resistor R3 and the capacitor C3 are connected in parallel. When the asymmetric half-bridge flyback isolation converter circuit is working, the secondary rectifier module is turned on. At this time, the negative resonant current flows through resistor R4 to capacitor C3, and the energy feedback module increases the equivalent capacitance and load of the resonant circuit, thereby reducing the resonant frequency and voltage amplitude.

5. A single-stage PFC power supply circuit as claimed in claim 3, characterized in that: One end of the energy storage inductor Lr is connected to the output terminal of the composite rectifier module, and the other end is connected to the same-name terminal of the primary winding of the transformer T1 through the resonant capacitor Cr. The opposite-name terminal of the primary winding of the transformer T1 is connected to the positive terminal of the energy storage capacitor C1, the first switching element Q1, and the energy feedback module.

6. A single-stage PFC power circuit as claimed in claim 4, characterized in that: One end of the energy storage inductor Lr is connected to the output terminal of the composite rectifier module, and the other end is connected to the opposite-named terminals of the first switching element Q1, the second switching element Q2, and the primary winding of the transformer T1; the same-named terminal of the primary winding of the transformer T1 is grounded through the resonant capacitor Cr; the positive terminal of the energy storage capacitor C1 is connected to the first switching element Q1 and the composite rectifier module.

7. A single-stage PFC power circuit as claimed in claim 5, characterized in that: The secondary rectifier module includes a diode D3 and a capacitor C4. The anode of the diode D3 is connected to the power output terminal VO+, and the cathode of the diode D3 is connected to the opposite terminal of the secondary winding of the transformer T1. The same terminal of the secondary winding of the transformer T1 is connected to the positive terminal of the capacitor C4 and the power output terminal VO-. The negative terminal of the capacitor C4 is connected to the power output terminal VO-.

8. A single-stage PFC power circuit as recited in claim 1, wherein: The first switching element Q1 includes an N-channel MOSFET, and the second switching element Q2 includes an N-channel MOSFET.

9. A single-stage PFC power circuit as recited in claim 1, wherein: The EMI filtering module includes a capacitor CX1, a common-mode inductor LF1, a differential-mode inductor L1, and a capacitor CX2 connected in sequence.

10. A single-stage PFC power supply circuit as claimed in claim 1, characterized in that: The composite rectifier module includes diodes D4, D5, D6, and D7; diodes D4, D5, D6, and D7 are connected in series in pairs to form a single-phase bridge rectifier.

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