A single-stage isolated boost type PFC converter

Abstract

The application discloses a single-stage isolated Boost type PFC converter, which comprises input filter modules, rectifier modules, full-bridge energy storage inverter modules, isolation transformers, secondary-side rectifier modules and output filter modules which are electrically connected in sequence, and active clamp modules which are connected in parallel on a DC bus between the rectifier modules and the full-bridge energy storage inverter modules. The input filter modules comprise filter inductors which are connected in series with each phase of an AC power supply. The full-bridge energy storage inverter modules comprise a full-bridge circuit formed by four switching tubes, and the bridge arm midpoints are connected to the two ends of a primary winding of the isolation transformer. The filter inductors release energy which is superimposed with input power and is transmitted to a secondary winding of the isolation transformer. Two states are alternately performed in a switching cycle. The converter simultaneously realizes Boost voltage rising, energy storage and isolated inverter energy transmission in single-stage power conversion, does not need a large-capacity bus capacitor, simplifies a topological structure and improves conversion efficiency and power density.

Description

Technical Field

[0001] This application relates to the field of power conversion, specifically to a single-stage isolated Boost-type PFC converter. Background Technology

[0002] With the continuous development of power electronics technology, brick-type modular power supplies, with their advantages of high power density, high reliability, and standardized packaging, have been widely used in high-power-density power supply scenarios such as communication equipment, data centers, and servers, becoming the core power supply unit in these scenarios. Their emergence has improved the stability and efficiency of power supply systems, meeting the high power requirements of modern electronic equipment.

[0003] Traditional AC-DC power supply modules typically employ a two-stage circuit topology: a cascaded structure of a front-stage boost-type PFC converter and a rear-stage isolated DC-DC converter. The front-stage boost-type PFC converter rectifies and boosts the AC input to a stable DC bus voltage while correcting the input power factor. The rear-stage isolated DC-DC converter uses a high-frequency transformer to achieve electrical isolation and voltage transformation, converting the DC bus voltage to the required output voltage. This structure can meet power supply requirements to a certain extent and has advantages such as a high input power factor.

[0004] However, this two-stage circuit structure has several drawbacks. First, a large-capacity bus capacitor, typically an electrolytic capacitor, is required between the two stages to buffer the power difference between the front and rear stages and store energy. However, large-capacity electrolytic capacitors are bulky, heavy, and have a limited lifespan, severely restricting the power density and reliability of the brick-type power supply. Second, during power-on startup, the charging process of the large-capacity bus capacitor generates a huge inrush current, requiring additional inrush current suppression circuitry, such as NTC thermistors and relay bypass circuits. This increases the complexity and cost of the brick-type power supply's external circuitry. Furthermore, the front-stage Boost-type PFC converter typically requires sampling multiple AC voltage and current signals to achieve dual closed-loop control of the voltage outer loop and current inner loop. This complex control circuitry further reduces the power density of the brick-type power supply. Finally, the energy undergoes two power conversions, and the cumulative losses in each stage lead to a decrease in overall conversion efficiency, further limiting the improvement of power density.

[0005] While some attempts have been made to integrate PFC functionality with isolated DC-DC conversion functionality in existing technologies, there is still room for improvement in terms of circuit topology, control strategy, and conversion efficiency. Summary of the Invention

[0006] To address the technical problems in the prior art, this application provides a single-stage isolated Boost-type PFC converter.

[0007] This application provides a single-stage isolated Boost-type PFC converter using the following technical solution:

[0008] A single-stage isolated Boost-type PFC converter includes an input filter module, a rectifier module, a full-bridge energy storage inverter module, an isolation transformer, a secondary rectifier module, and an output filter module connected in sequence, as well as an active clamping module connected in parallel on the DC bus between the output terminal of the rectifier module and the input terminal of the full-bridge energy storage inverter module.

[0009] The input filtering module includes filter inductors connected in series with each phase of the AC power supply;

[0010] The full-bridge energy storage inverter module includes a full-bridge circuit composed of a first switch, a second switch, a third switch, and a fourth switch. The midpoints of the two bridge arms of the full-bridge circuit are respectively connected to the two ends of the primary winding of the isolation transformer.

[0011] The full-bridge energy storage inverter module is configured such that, in the first operating state, the first, second, third, and fourth switches are simultaneously turned on, making the two ends of the primary winding of the isolation transformer equipotential, and the filter inductor forms a charging circuit through the rectifier module and the full-bridge energy storage inverter module to store energy; in the second operating state, one set of diagonal switches of the full-bridge circuit is turned on and the other set of diagonal switches is turned off, so that the energy released by the filter inductor is superimposed with the electrical energy continuously input by the AC power supply through the rectifier module and then transferred to the secondary side through the isolation transformer; the first and second operating states alternate within one switching cycle, thereby simultaneously realizing boost voltage energy storage and isolation inverter energy transfer in single-stage power conversion.

[0012] In summary, this application includes at least one of the following beneficial technical effects:

[0013] 1. By multiplexing the Boost energy storage switch and the inverter switch of the isolated DC-DC converter in the traditional two-stage circuit into a full-bridge energy storage inverter module composed of a first, second, third, and fourth switching transistor, in the first operating state, all four switching transistors are turned on simultaneously to make the two ends of the primary winding of the isolation transformer equal in potential, thereby realizing energy storage in the filter inductor. In the second operating state, one set of diagonal switching transistors is turned on and the other set is turned off, so that the energy released by the filter inductor is superimposed with the power energy continuously input by the AC power supply through the rectifier module and then transferred to the secondary side through the isolation transformer. Thus, Boost boost energy storage and isolated inverter energy transfer are realized simultaneously in a single-stage power conversion. Since Boost boost energy storage and isolated inverter energy transfer are realized simultaneously in a single-stage power conversion, there is no need to set a large-capacity bus electrolytic capacitor between the rectifier output and the inverter stage, reducing the number of power conversion stages, reducing the superposition of power device losses, and thus improving conversion efficiency. At the same time, by eliminating the large-capacity electrolytic capacitor, the converter size is reduced, the power density is increased, and the surge current problem caused by the charging of the large-capacity capacitor during power-on is eliminated.

[0014] 2. By setting the inductance value, switching frequency, and load conditions of the filter inductor to operate in discontinuous current mode, the inductor current linearly rises from zero to a peak value and then linearly decreases before returning to zero before the end of the cycle in each switching cycle. Utilizing the characteristic of the current periodically returning to zero, the average envelope of the inductor current naturally follows the input voltage waveform in a sinusoidal shape. A constant duty cycle single-voltage closed-loop control method is adopted, which only samples the output DC voltage and compares it with the reference voltage. The constant duty cycle signal is output by the PI regulator to generate the PWM drive signal for the switching transistor. Therefore, output voltage stability and power factor correction can be achieved simultaneously without current sampling circuits and current inner loop control. This simplifies the hardware implementation of the control circuit, reduces the number of sampling channels, and lowers system cost and complexity. At the same time, the switching transistor turns on when the inductor current is zero, achieving zero-current turn-on to reduce switching losses.

[0015] 3. By setting an active clamping module, including a clamping capacitor and a clamping switch, in parallel on the DC bus between the output of the rectifier module and the input of the full-bridge energy storage inverter module, during the first operating state, the body diode of the clamping switch is forward-biased to charge the clamping capacitor by absorbing the voltage spike energy generated by the leakage inductance of the isolation transformer. During the second operating state, the clamping switch is controlled to conduct, feeding the energy stored in the clamping capacitor back to the isolation transformer. This effectively clamps the voltage spikes at a safe level to protect the power switches in the full-bridge energy storage inverter module from overvoltage breakdown. At the same time, the leakage inductance energy is recovered and reused to avoid energy waste, thereby improving the overall conversion efficiency and system reliability. Attached Figure Description

[0016] Figure 1This is a structural block diagram of a single-stage isolated Boost-type PFC converter provided in one embodiment of this application;

[0017] Figure 2 This is an example diagram of the three-phase circuit topology of a full-bridge single-stage isolated Boost PFC converter;

[0018] Figure 3 This is an example diagram of a single-phase circuit topology for a full-bridge single-stage isolated Boost PFC converter;

[0019] Figure 4 This is a three-phase circuit topology example of a full-wave single-stage isolated Boost PFC converter;

[0020] Figure 5 This is a single-phase circuit topology example of a full-wave, single-stage isolated Boost-type PFC converter;

[0021] Figure 6 These are the input and output voltage and current waveforms of a full-wave three-phase single-stage isolated Boost PFC converter.

[0022] Figure 7 This is a waveform diagram of the transformer primary current in a full-wave three-phase single-stage isolated Boost PFC converter;

[0023] Figure 8 This is the equivalent circuit diagram (a) of the three-phase rectifier circuit of a full-wave three-phase single-stage isolated Boost PFC converter in operation state;

[0024] Figure 9 This is the equivalent circuit diagram (b) of the three-phase rectifier circuit of the full-wave three-phase single-stage isolated Boost PFC converter in operation state;

[0025] Figure 10 This is the equivalent circuit diagram of the three-phase rectifier circuit of a full-wave three-phase single-stage isolated Boost PFC converter in its operating state (c).

[0026] Figure 11 This is the equivalent circuit diagram of the three-phase rectifier circuit of a full-wave three-phase single-stage isolated Boost PFC converter in its operating state (d).

[0027] Figure 12 This is the equivalent circuit diagram of the three-phase rectifier circuit of a full-wave three-phase single-stage isolated Boost PFC converter in its operating state (e).

[0028] Figure 13 This is the equivalent circuit diagram of the three-phase rectifier circuit of a full-wave three-phase single-stage isolated Boost PFC converter in its operating state (f).

[0029] Figure 14This is the equivalent circuit diagram of mode (a) of the full-bridge three-phase single-stage isolated Boost PFC converter in rectifier operation mode;

[0030] Figure 15 This is the equivalent circuit diagram of mode (a) of the full-bridge three-phase single-stage isolated Boost PFC converter in rectifier operation mode;

[0031] Figure 16 This is the three-mode equivalent circuit diagram of the full-bridge three-phase single-stage isolated Boost PFC converter in rectification mode (a);

[0032] Figure 17 This is the equivalent circuit diagram of mode (a) of the full-bridge three-phase single-stage isolated Boost PFC converter in rectification mode;

[0033] Figure 18 This is a block diagram of a constant duty cycle control strategy.

[0034] Explanation of reference numerals in the attached diagram: 100, AC power supply; 200, input filter module; 300, rectifier module; 400, active clamping module; 500, full-bridge energy storage inverter module; 600, isolation transformer; 700, secondary-side rectifier module; 800, output filter module; 900, DC load; L, filter inductor; D1~D6, rectifier diodes; S1, first switch; S2, second switch; S3, third switch; S4, fourth switch; S5~S8, rectifier devices; S9, clamping switch; C dc 1010 Clamping capacitor; N1, primary winding; N2, secondary winding; C2, output filter capacitor; 1010, first adder; 1020, PI regulator; 1030, limiter; 1040, first comparator; 1060, second adder; 1070, inverter; 1080, second comparator. Detailed Implementation

[0035] The technical solutions in the embodiments of this application will be further described in detail below with reference to the accompanying drawings. The described embodiments are only possible technical implementations of this application, but are not limited thereto. Other embodiments obtained by those skilled in the art in conjunction with the embodiments of this application without creative effort are also within the protection scope of this application.

[0036] This application mainly uses a single-stage power conversion to achieve multiple functions, thereby improving conversion efficiency, simplifying circuit structure and control. The following is a further detailed description of this application.

[0037] Please refer to Figure 1The single-stage isolated Boost-type PFC converter provided in this application includes, in sequence, an input filter module 200, a rectifier module 300, a full-bridge energy storage inverter module 500, an isolation transformer 600, a secondary-side rectifier module 700, and an output filter module 800, and an active clamping module 400 connected in parallel on the DC bus between the output terminal of the rectifier module 300 and the input terminal of the full-bridge energy storage inverter module 500. The input terminal of the input filter module 200 is connected to an AC power supply 100, and the output terminal of the output filter module 800 is connected to a DC load 900 (equivalent resistance R). L These modules work together to achieve functions such as power factor correction, boost conversion, and electrical isolation, solving the problems of complex, inefficient, and large-sized traditional two-stage ACDC power supply topologies. This converter reuses power devices to combine the boost energy storage switch and the inverter switch of the isolated DCDC circuit in a traditional two-stage circuit, constructing a high-frequency full-bridge energy storage inverter circuit. This achieves single-stage isolated ACDC conversion, eliminating the need for large-capacity bus capacitors and removing the bottleneck of large size and short lifespan of electrolytic capacitors. It also features low starting current surge and is suitable for high-power-density ACDC brick power supply modules.

[0038] Please refer to Figures 2 to 5 The circuit topology of this converter has four different configurations: a full-bridge three-phase single-stage isolated Boost PFC converter, a full-bridge single-phase single-stage isolated Boost PFC converter, a full-wave three-phase single-stage isolated Boost PFC converter, and a full-wave single-phase single-stage isolated Boost PFC converter. Among these, "full-bridge" refers to the secondary-side rectifier module 700 using a full-bridge rectifier circuit, and "full-wave" refers to the secondary-side rectifier module 700 using a full-wave rectifier circuit.

[0039] Specifically, the input filtering module 200 includes filter inductors L connected in series with each phase of the AC power supply 100. The filter inductors L can be made of magnetic materials with high permeability, such as ferrite core inductors (toroidal or E-shaped cores), or they can be air-core inductors. Connected in series with each phase of the AC power supply 100, the filter inductors L act as filters, suppressing high-frequency noise and interference in the AC power supply 100, while providing a stable input for subsequent rectification and energy storage processes. The filter inductors L also function as energy storage inductors in the Boost circuit, completing the storage and release of electrical energy. Each phase of a three-phase AC power supply has one filter inductor L, while a single-phase AC power supply has one filter inductor L.

[0040] The full-bridge energy storage inverter module 500 comprises a full-bridge circuit consisting of a first switching transistor S1, a second switching transistor S2, a third switching transistor S3, and a fourth switching transistor S4. These switching transistors can be either MOSFETs or IGBTs. MOSFETs offer advantages such as fast switching speed and low on-resistance, making them suitable for high-frequency operation; IGBTs, on the other hand, have higher voltage withstand and current carrying capacity, making them suitable for high-power applications. The midpoints of the two bridge arms of the full-bridge circuit are connected to the two ends of the primary winding N1 of the isolation transformer 600. The switching frequency of the full-bridge energy storage inverter module 500 is much higher than the power frequency of the front-end rectifier module 300. The boost circuit's voltage increase principle is achieved through the high-frequency switching of the transistors, simultaneously converting AC to DC power and outputting AC power to the isolation transformer 600. In the first operating state, the first switch S1, the second switch S2, the third switch S3, and the fourth switch S4 are simultaneously turned on, making the two ends of the primary winding N1 of the isolation transformer 600 at the same potential. The filter inductor L forms a charging circuit through the rectifier module 300 and the full-bridge energy storage inverter module 500 to store energy. At this time, the current in the filter inductor L rises linearly, converting electrical energy into magnetic energy for storage. In the second operating state, one set of diagonal switches in the full-bridge circuit is turned on, and the other set of diagonal switches is turned off. The energy released by the filter inductor L is superimposed with the electrical energy continuously input from the AC power supply 100 through the rectifier module 300 and then transferred to the secondary side through the isolation transformer 600. The first and second operating states alternate within one switching cycle, thereby simultaneously realizing boost voltage energy storage and isolation inverter energy transfer in a single-stage power conversion. This multiplexing method of power devices reduces the number of power conversion stages and power devices, simplifying the circuit topology.

[0041] The function of rectifier module 300 is to convert AC power supply 100 into DC power supply. When AC power supply 100 is a three-phase AC power supply, rectifier module 300 is a three-phase full-bridge rectifier circuit composed of six rectifier devices; when AC power supply 100 is a single-phase AC power supply, rectifier module 300 is a single-phase full-bridge rectifier circuit composed of four rectifier devices. The rectifier devices can be rectifier diodes or MOSFETs. Using rectifier diodes has the advantages of simple structure and low cost; using MOSFETs can achieve synchronous rectification, reduce conduction losses, and improve conversion efficiency. The output of rectifier module 300 is connected to the input terminals of active clamp module 400 and full-bridge energy storage inverter module 500. The rectifier circuit can adopt two forms: full-bridge rectification (a bridge circuit composed of four rectifier devices) and full-wave rectification (two rectifier devices in conjunction with a center-tapped transformer winding) to adapt to different voltage levels. Both can achieve efficient conversion of AC to unidirectional pulsating DC and have common advantages such as high ripple frequency, low filtering difficulty, and stable conversion efficiency.

[0042] The active clamping module 400 includes clamping capacitors. And clamping switch S9. Clamping capacitor. One end is connected to the positive output terminal of the rectifier module 300 and the positive input terminal of the full-bridge energy storage inverter module 500, at the positive DC bus node, with a clamping capacitor. The other end is connected to the negative DC bus node of the output negative terminal of the rectifier module 300 via the clamping switch S9. The active clamping module 400 is configured such that, during the first operating state, when the voltage spike of the bus of the full-bridge energy storage inverter module 500 caused by the leakage inductance of the isolation transformer 600 exceeds the clamping capacitor... When the voltage is [value], the body diode of the clamping switch S9 is forward-biased, and the clamping capacitor [value] is [value]. Absorbs peak energy for charging; during the second operating state, clamping switch S9 is controlled to conduct, and clamping capacitor... The energy stored in the capacitor is fed back to the isolation transformer 600 via the clamping switch S9. The active clamping module 400 can clamp the voltage spikes caused by the transformer leakage inductance to the clamping capacitor. The voltage level protects the power switches in the full-bridge energy storage inverter module 500 from overvoltage breakdown, while storing leakage inductance energy in the clamping capacitor. After the converter is powered off, the energy is fed back to the system through controlled discharge, avoiding energy waste and improving the overall conversion efficiency. In addition, when the converter is powered off, the active clamping module 400 can also act as a buffer circuit for the current of the input filter inductor L, preventing overvoltage breakdown of the device and protecting the device.

[0043] The isolation transformer 600 is used to achieve electrical isolation and voltage transformation. Its primary winding N1 is connected to the full-bridge energy storage inverter module 500, and its secondary winding N2 is connected to the secondary rectifier module 700. The magnetic core of the isolation transformer 600 is typically made of a high-permeability material, such as silicon steel sheet or ferrite, to reduce hysteresis loss and eddy current loss. The isolation transformer 600 transmits the high-frequency AC power generated by the full-bridge energy storage inverter module 500 to the secondary rectifier circuit, achieving electrical isolation and voltage transformation between the primary and secondary sides.

[0044] The secondary-side rectifier module 700 is one of the following: a full-bridge rectifier circuit consisting of four rectifier devices S5~S8, with a single secondary winding N2 on the secondary side of the isolation transformer 600; or a full-wave rectifier circuit consisting of two rectifier devices, with a center-tapped winding on the secondary side of the isolation transformer 600. The rectifier devices are either rectifier diodes or MOSFETs. When a MOSFET is used, the secondary-side rectifier module 700 operates in synchronous rectification mode. The full-bridge rectifier circuit is suitable for applications with higher output voltages, featuring a simpler transformer winding structure but a larger number of rectifier devices. The full-wave rectifier circuit is suitable for applications with lower output voltages, featuring fewer rectifier devices but a slightly more complex transformer winding structure. In low-voltage, high-current output applications, using MOSFETs instead of rectifier diodes in synchronous rectification mode can significantly reduce the on-state voltage drop and conduction losses of the rectifier devices, thereby improving conversion efficiency.

[0045] The output filter module 800 is one of the following: a C-type filter circuit consisting of a single output filter capacitor C2 connected in parallel to the output terminal of the secondary rectifier module 700; or a CLC-type π filter circuit consisting of a pre-stage filter capacitor, an output filter inductor, and a post-stage filter capacitor connected in sequence. The output terminal of the output filter module 800 is connected to a DC load resistor RL. By controlling the constant duty cycle, it ensures that the output is within the range of different DC load resistors RL... L Under operating conditions, the output DC voltage Maintaining stability is crucial. The C-type filter circuit only requires a single output filter capacitor C2 connected in parallel at the output of the secondary rectifier module 700 to achieve smoothing and ripple suppression of the output DC power. This solution is simple in design, low in cost, and small in size, making it suitable for applications where output ripple requirements are not high. The CLC-type π filter circuit employs a three-stage filtering architecture of a pre-stage capacitor-inductor-post-stage capacitor, which can significantly reduce the peak output voltage ripple and provide better output power quality. It is suitable for applications with stringent output ripple requirements, but it is more expensive, larger in size, and more difficult to design. Therefore, the appropriate selection and configuration should be based on the specific needs and constraints of the target application.

[0046] To ensure the stable and reliable operation of the converter under DCM conditions, the entire system also integrates comprehensive sampling, monitoring, driving, clamping, protection, and auxiliary function modules, including: a voltage characteristic sampling module for real-time high-frequency sampling of voltage and current parameters at the DC output terminal, accurately extracting voltage amplitude, phase, and frequency information to provide feedback control signals for the system; an input inductor current monitoring module for real-time acquisition and monitoring of the current of the front-end filter inductor L, used to assess the input power status in DCM mode and serving as the triggering basis for input-side overcurrent protection; an isolation drive module to provide stable drive for the main switching transistor; an active clamping module 400, which uses specific PWM control timing to solve the problem of voltage spikes in the power switching of the high-frequency full-bridge energy storage inverter circuit caused by transformer leakage inductance; and a soft-start and protection module to achieve smooth system startup and provide real-time protection against faults such as overcurrent, overvoltage, and overheating.

[0047] The implementation principle of this embodiment is as follows: This single-stage isolated Boost-type PFC converter achieves power factor correction, boost voltage increase, and electrical isolation simultaneously through a circuit design and module combination that reuses power devices. The reuse of power devices reduces the number of power conversion stages and power devices, simplifying the circuit topology. The filter inductor L operates in discontinuous inductor current mode, allowing the envelope of the input current to naturally follow the input voltage waveform, achieving power factor correction. Simultaneously, the switching transistor can achieve zero-current turn-on, reducing switching losses. The active clamping module 400 effectively suppresses voltage spikes generated by the leakage inductance of the isolation transformer 600 and feeds the leakage inductance energy back to the system, improving conversion efficiency. The secondary-side rectifier module 700 and the output filter module 800 are selected according to different application requirements, meeting various output demands. Compared with traditional two-stage solutions, this converter eliminates the need for large-capacity bus capacitors, removing the bottlenecks of large size and short lifespan of electrolytic capacitors. It features low starting current surge, simple control, low cost, and improved system reliability and power density, making it suitable for high-power-density ACDC brick power module applications.

[0048] In a specific embodiment, the inductance value of the filter inductor L and switching frequency It is configured such that, within the rated load range of the converter, the filter inductor L operates in discontinuous current mode. In discontinuous current mode, during each switching cycle, the current of the filter inductor L starts from zero and, during the first operating state, flows at a slope... Linear rise to peak It decreases linearly during the second operating state and returns to zero before the end of the switching cycle. The instantaneous input voltage after rectification. This is the duty cycle of the 500 full-bridge energy storage inverter module.

[0049] This discontinuous current switching mode (DMS) offers unique advantages. Because the current periodically returns to zero, the inductor current in each switching cycle is unaffected by the previous cycle. Under a constant duty cycle, the peak value of the inductor current in each switching cycle is proportional to the instantaneous input voltage at that moment. Therefore, the average envelope of the inductor current naturally exhibits a sinusoidal shape and is in phase with the input voltage, achieving a high power factor without the need for additional current sampling and current loop control. Simultaneously, the switch turns on when the inductor current is zero, achieving zero-current turn-on (ZCS), reducing switching losses and improving conversion efficiency. The DMS is suitable for low-to-medium power applications and offers high conversion efficiency.

[0050] The implementation principle of this embodiment is as follows: by reasonably setting the inductance value, switching frequency, and load conditions of the filter inductor L, the filter inductor L is made to operate in discontinuous current mode, which fully utilizes the characteristics of this mode to achieve high power factor and low switching loss. In this mode, the control of the converter is simpler, eliminating the need for complex current sampling and control circuits, reducing system cost and complexity, while improving conversion efficiency and power density, and further optimizing the performance of the single-stage isolated Boost-type PFC converter.

[0051] Please refer to Figure 18 In a specific embodiment, the converter further includes a constant duty cycle single voltage closed-loop control module, which includes a voltage sampling unit, a first adder 1010, a PI regulator 1020, and a carrier phase shifting drive unit.

[0052] The voltage sampling unit is used to sample the DC voltage at the output terminal of the output filter module 800. The first adder 1010 is used to convert DC voltage... With reference voltage The error signal is obtained through comparison; the PI controller 1020 processes the error signal and outputs a constant duty cycle signal. The carrier phase-shifting drive unit is used for signals based on a constant duty cycle. The PWM drive signals for the first switch S1 to the fourth switch S4 are generated by phase shifting the carrier wave.

[0053] This constant duty cycle single-voltage closed-loop control method relies on the inherent characteristics of the discontinuous current mode of the inductor, achieving both output voltage stability and power factor correction simultaneously through a single voltage closed loop. Compared to the traditional two-stage scheme requiring a voltage outer loop and a current inner loop for dual closed-loop control, it simplifies the hardware implementation of the control circuit, reduces the number of sampling channels, lowers system cost and complexity, and is beneficial for improving power density. This control method eliminates the need for current sampling circuits and complex control circuits; it only requires sampling the secondary-side output DC bus voltage, making control simple and easy to integrate.

[0054] The implementation principle of this embodiment is as follows: By sampling the output voltage and comparing it with a reference voltage, a constant duty cycle signal is generated by the PI regulator 1020, thereby controlling the on and off of the switching transistor. Since the envelope of the input current naturally follows the input voltage waveform in discontinuous current mode, no additional current sampling and control is required. Output voltage stability and power factor correction can be achieved through a single voltage closed loop. This control method simplifies the control circuit, improves the system's reliability and power density, and reduces costs.

[0055] Regarding the specific implementation of carrier phase shifting, the system generates two sawtooth wave carrier signals. The second carrier signal is offset relative to the first carrier signal by half a switching cycle (i.e., a phase shift of 180°). The carrier magnitude M is equal to the peak amplitude of the sawtooth wave carrier signal. The first sawtooth wave carrier signal is compared with the limited duty cycle signal Dt in the first comparator 1040. When the duty cycle signal Dt is greater than the first carrier signal, the first comparator 1040 outputs a high level to generate PWM drive signals for driving the first switch S1 and the fourth switch S4. The second sawtooth wave carrier signal is subtracted from the carrier magnitude M by the second adder 1060 and then inverted by the inverter 1070 to obtain an equivalent carrier signal offset by half a cycle from the first carrier signal. This equivalent carrier signal is compared with the limited duty cycle signal Dt in the second comparator 1080. When the duty cycle signal Dt is greater than the equivalent carrier signal, the second comparator 1080 outputs a high level to generate PWM drive signals for driving the second switch S2 and the third switch S3. Because the two carrier signals are 180° out of phase, there is also a half-cycle phase difference between the PWM drive signals of the first switch S1 and the fourth switch S4 and the PWM drive signals of the second switch S2 and the third switch S3. This enables the full-bridge energy storage inverter module 500 to sequentially experience the following operating timing sequences within one switching cycle: mode one (all four transistors are on simultaneously), mode two (S1 and S3 are on, S2 and S4 are off), mode three (all four transistors are on simultaneously), and mode four (S2 and S4 are on, S1 and S3 are off).

[0056] Please refer to Figure 6 and Figure 7 In a specific embodiment, the AC power supply 100 is a three-phase AC power supply, and the three-phase input voltages are respectively... , , In discontinuous inductor current mode, one input voltage cycle Within, the periodic average value of the inductor current in phase a is ,in , , , , This represents the peak value of the three-phase input phase voltage. Let L be the inductance value of the filter inductor. For switching frequency, For phase a in the corresponding The segmented current coefficient within the interval is determined by the converter voltage ratio and the instantaneous input voltage of the corresponding phase.

[0057] Current coefficient of each segment The specific expression is as follows:

[0058]

[0059]

[0060]

[0061]

[0062]

[0063] Calculations show that the average input power of phase a within a quarter cycle is:

[0064]

[0065] The power factor is:

[0066]

[0067] Furthermore, the power factor is only related to the voltage ratio M, and power factor correction can be achieved without current sampling under constant duty cycle control. The above formula shows that when the output voltage... At a given time, the power factor (PF) is only related to the input voltage; the higher the input voltage, the lower the PF value. Therefore, a constant duty cycle control method is adopted. The secondary-side output DC bus voltage is sampled and compared with the reference voltage. The error signal is directly output as a constant duty cycle signal after passing through the PI regulator 1020. By controlling the phase shift of the carrier wave, a PWM drive signal for the switching transistor is generated, thus simultaneously achieving output voltage regulation and power factor correction.

[0068] When the AC power supply 100 is a three-phase AC power supply, the power factor of the converter can be made to reach a preset target by configuring the voltage ratio range of the converter. According to the relationship between the power factor and the voltage ratio M, when the voltage ratio M is in the range of 1.0 ≤ M ≤ 2.5, the corresponding power factor PF ≥ 0.95; when the voltage ratio M is in the range of 1.0 ≤ M ≤ 1.8, the corresponding power factor PF ≥ 0.98. Therefore, in practical applications, the power factor can be determined based on the output voltage. Transformer turns ratio n, peak input voltage By setting the voltage ratio M within the above range and the design value of the duty cycle D, high power factor correction can be achieved without current sampling under constant duty cycle control.

[0069] The implementation principle of this embodiment is as follows: Under three-phase AC power input, utilizing the characteristics of discontinuous current mode in inductors, the expressions for the periodic average value of the inductor current, average input power, and power factor are derived mathematically. Since the power factor is only related to the voltage ratio M, under constant duty cycle control, current sampling is unnecessary; power factor correction can be achieved based on the relationship between the input and output voltages. This method simplifies the control process and improves the performance and efficiency of the converter under three-phase AC power input.

[0070] Please refer to Figures 14 to 17 In a specific embodiment, the full-bridge energy storage inverter module 500 sequentially experiences the following four modes within one switching cycle, where modes one and three correspond to the first operating state, and modes two and four correspond to the second operating state:

[0071] Please refer to Figure 14 Mode 1: Switches S1, S2, S3, and S4 are simultaneously turned on. At this time, the primary winding N1 of the isolation transformer 600 is short-circuited, providing a charging circuit for the filter inductor L. The current in the filter inductor L increases linearly with time to store energy. The rectifier devices in the secondary rectifier module 700 are in the off state due to reverse voltage. During this process, when the voltage spike caused by the switching on and off of the transistors exceeds the clamping capacitor... When the voltage is applied, the body diode of the clamping switch S9 in the active clamping module 400 is forward-biased, supplying power to the clamping capacitor. Charge, absorb peak energy.

[0072] Please refer to Figure 15 Mode 2: The second switch S2 and the fourth switch S4 are turned off, while the first switch S1 and the third switch S3 remain on. At this time, the primary winding N1 of the isolation transformer 600 is subjected to a positive voltage, and the corresponding rectifier devices in the secondary rectifier module 700 are turned on by the positive voltage. The input energy of the system is superimposed with the energy stored in the filter inductor L in the previous period, realizing the boost function. Energy is transferred from the primary winding N1 of the isolation transformer 600 to the secondary winding N2; simultaneously, the current of the filter inductor L shows a linear decreasing trend. During this stage, the clamping switch S9 of the active clamping module 400 is turned on under control, and the clamping capacitor... The stored energy is discharged through the clamping switch S9 and fed back to the isolation transformer 600, improving the overall conversion efficiency of the system.

[0073] Please refer to Figure 16Mode 3: Switches S1, S2, S3, and S4 are simultaneously turned on again, and the filter inductor L re-enters the charging stage. The operating state in this stage is exactly the same as in Mode 1, and the current in the filter inductor L rises linearly again. The body diode of the clamping switch S9 in the active clamping module 400 will still be forward-biased, and the clamping capacitor... It continues to charge in order to absorb any possible voltage spikes.

[0074] Please refer to Figure 17 Mode 4: The first switch S1 and the third switch S3 are turned off, while the second switch S2 and the fourth switch S4 remain on. At this time, the primary winding N1 of the isolation transformer 600 experiences a reverse voltage, and the corresponding rectifier in the secondary rectifier module 700 is turned on by a forward voltage. The system energy and the energy stored in the filter inductor L continue to be transferred to the secondary side of the isolation transformer 600, and the current in the filter inductor L decreases linearly. During this stage, the clamping switch S9 of the active clamping module 400 is turned on under control, and the clamping capacitor... The stored energy is discharged through the clamping switch S9 and fed back to the system.

[0075] In Mode 2 and Mode 4, the voltage polarity of the primary winding N1 of the isolation transformer 600 is opposite, causing the magnetic core of the isolation transformer 600 to be alternately magnetized in both positive and negative directions, thus preventing unidirectional saturation of the magnetic core. After Mode 4 ends, the circuit returns to the initial charging state of Mode 1, thus completing a full high-frequency switching cycle. Subsequently, the system enters the next operating cycle, thereby achieving continuous energy conversion and power factor correction.

[0076] During the operation of the above four modes, modes one and three realize the boost energy storage function of the filter inductor L, while modes two and four realize the energy storage release and isolation energy transfer functions. The four modes alternate in sequence within a high-frequency switching cycle, enabling the converter to simultaneously complete boost energy storage and isolation inverter energy transfer in single-stage power conversion, which greatly simplifies the circuit topology and control complexity.

[0077] Please refer to Figures 8 to 13 In a specific embodiment, when the AC power supply 100 is a three-phase AC power supply, the front-end rectifier module 300 is a three-phase full-bridge rectifier circuit, composed of six rectifier diodes D1 to D6. Since the power frequency of the three-phase AC power supply is much lower than the switching frequency of the full-bridge energy storage inverter module 500, the three-phase full-bridge rectifier circuit has six operating states within one power frequency cycle, each state occupying 60°, as follows:

[0078] Please refer to Figure 8In the (a) working state stage: In the common cathode rectifier diode group, the potential at the end of the three-phase input U phase (a phase) is at the highest level, and the corresponding rectifier diode D1 is subjected to a positive voltage and is in the conducting state; In the common anode rectifier diode group, the potential at the end of the three-phase input V phase (b phase) is at the lowest level, and the corresponding rectifier diode D4 is subjected to a positive voltage and is in the conducting state.

[0079] Please refer to Figure 9 In the (b) working state stage: in the common cathode rectifier diode group, the potential of the U phase endpoint remains the highest, and the rectifier diode D1 remains in the conducting state unchanged; in the common anode rectifier diode group, the endpoint with the lowest potential switches from the V phase to the W phase (c phase), so the corresponding rectifier diode D6 is turned on and D4 is turned off.

[0080] Please refer to Figure 10 In the (c) working state stage: in the common cathode rectifier diode group, the terminal with the highest potential switches from phase U to phase V, corresponding to rectifier diode D3 being turned on and D1 being turned off; in the common anode rectifier diode group, the terminal of phase W still maintains the lowest potential, and rectifier diode D6 continues to be turned on.

[0081] Please refer to Figure 11 In the (d) working state stage: In the common cathode rectifier diode group, the V phase endpoint still maintains the highest potential, and the rectifier diode D3 remains in the conducting state; In the common anode rectifier diode group, the endpoint with the lowest potential switches from the W phase to the U phase, corresponding to the rectifier diode D2 being turned on and D6 being turned off.

[0082] Please refer to Figure 12 In the (e) working state stage: in the common cathode rectifier diode group, the terminal with the highest potential switches from the V phase to the W phase, corresponding to rectifier diode D5 being turned on and D3 being turned off; in the common anode rectifier diode group, the U phase terminal still maintains the lowest potential, and rectifier diode D2 remains in the on state.

[0083] Please refer to Figure 13 In the (f) working state stage: In the common cathode rectifier diode group, the W phase endpoint still maintains the highest potential, and the rectifier diode D5 continues to conduct; In the common anode rectifier diode group, the endpoint with the lowest potential switches from the U phase to the V phase, corresponding to the rectifier diode D4 conducting and D2 being cut off.

[0084] When the moment of operation (g) arrives, the circuit returns to the initial state during operation (a), thus completing a full power frequency cycle. The three-phase rectifier circuit, through the alternating operation of the above six stages, continuously rectifies the three-phase AC power, providing pulsating DC voltage to the subsequent full-bridge energy storage inverter module 500. During each of the above six operating states, the full-bridge energy storage inverter module 500 simultaneously performs high-frequency switching operation, and the high-frequency operating principle is the same in each state, cycling according to the sequence of modes one to four.

[0085] In a specific embodiment, when the AC power supply 100 is a single-phase AC power supply, the filter inductor L is located on either the AC input side or the DC output side of the rectifier module 300. When the filter inductor L is located on the AC input side of the rectifier module 300, the inductor operates in AC mode, with current flowing bidirectionally through the inductor, resulting in higher core utilization. When the filter inductor L is located on the DC output side of the rectifier module 300, the inductor operates in DC pulsating mode, with current flowing unidirectionally through the inductor, making the inductor design relatively simple. Both placement methods are functionally equivalent, both enabling Boost energy storage and power factor correction in DCM mode, and can be flexibly selected based on the spatial layout and electromagnetic compatibility requirements of the specific application scenario.

[0086] The implementation principle of this embodiment is as follows: Setting the filter inductor L at different locations within the rectifier module 300 will result in different operating states, but all will achieve the functions of boost energy storage and power factor correction. Setting the filter inductor L on the AC input side improves core utilization, while setting it on the DC output side simplifies the design. Users can select the appropriate placement of the filter inductor L based on the requirements of the actual application scenario, such as space constraints and electromagnetic interference, to achieve optimal performance and application effects.

[0087] The following is a detailed description of the overall operation of this single-stage isolated Boost-type PFC converter.

[0088] When AC power 100 is connected, the AC power first passes through the filter inductor L in the input filter module 200 to filter out high-frequency noise, and then enters the rectifier module 300. The rectifier module 300 converts the AC power into pulsating DC power and outputs it to the DC bus. The active clamping module 400 is connected in parallel to the DC bus and is in standby mode.

[0089] Driven by control signals, the full-bridge energy storage inverter module 500 performs high-frequency switching operations at a frequency much higher than the power frequency. Within each high-frequency switching cycle, the converter sequentially undergoes operation in modes one through four:

[0090] During mode one (first operating state), all four switches S1 to S4 of the full-bridge energy storage inverter module 500 are simultaneously turned on, and the two ends of the primary winding N1 of the isolation transformer 600 are short-circuited to be at the same potential. At this time, the pulsating DC voltage output by the rectifier module 300 is entirely applied across the filter inductor L, and the current in the filter inductor L flows at a slope. Starting from zero, the voltage rises linearly, converting electrical energy into magnetic energy for storage. During this process, if the voltage spike caused by the leakage inductance of the isolation transformer 600 exceeds the clamping capacitor... Voltage, the body diode of clamping switch S9 in active clamping module 400 is forward-biased, clamping capacitor It absorbs peak energy for charging. The rectifier devices in the secondary rectifier module 700 are cut off due to reverse voltage, and no energy is transferred to the secondary side.

[0091] During mode two (second operating state), the first switch S1 and the third switch S3 remain on, while the second switch S2 and the fourth switch S4 are off. The primary winding N1 of the isolation transformer 600 is subjected to a positive voltage, and the corresponding rectifier device on the secondary side is turned on. At this time, the magnetic energy stored in the filter inductor L begins to be released. The released energy is superimposed on the electrical energy continuously input from the AC power supply 100 through the rectifier module 300, realizing the boost voltage function. The superimposed energy is transferred from the primary side to the secondary side through the isolation transformer 600. The current in the filter inductor L decreases linearly. Simultaneously, the clamping switch S9 of the active clamping module 400 is turned on under control, and the clamping capacitor... The leakage inductance energy stored in the system is fed back to the isolation transformer 600 through the clamping switch S9, thereby improving system efficiency.

[0092] During mode three (first operating state), the four switches S1 to S4 are turned on simultaneously again, and the operating state is the same as that of mode one. The filter inductor L is charged again, and the current rises linearly again.

[0093] During mode four (second operating state), the second switch S2 and the fourth switch S4 remain on, while the first switch S1 and the third switch S3 are off. The primary winding N1 of the isolation transformer 600 experiences a reverse voltage (opposite to the mode polarity), and the corresponding rectifier devices on the secondary side are turned on. The energy released by the filter inductor L, combined with the energy continuously input from the AC power supply 100 via the rectifier module 300, is transferred to the secondary side via the isolation transformer 600, causing the inductor current to decrease linearly. The clamping switch S9 of the active clamping module 400 is also controlled to conduct, feeding back the clamping capacitor. The energy in the transformer. In Mode 2 and Mode 4, the polarity of the primary voltage of the transformer alternates, causing the magnetic core to be magnetized alternately in both positive and negative directions, thus avoiding core saturation.

[0094] The high-frequency AC power transmitted to the secondary side via the isolation transformer 600 is rectified by the secondary-side rectifier module 700, converting the high-frequency AC power into pulsating DC power. The secondary-side rectifier module 700 can employ a full-bridge rectifier circuit or a full-wave rectifier circuit. When using MOSFETs, it can operate in synchronous rectification mode to reduce conduction losses. The rectified pulsating DC power is then smoothed and filtered by the output filter module 800 (a C-type filter circuit or a CLC-type π filter circuit), ultimately outputting a stable DC voltage to supply the DC load 900.

[0095] Please refer to Figure 18 At the control level, the converter adopts a constant duty cycle single-voltage closed-loop control method. The voltage characteristic sampling module samples the DC voltage at the output of the 800 output filter module in real time. Compare it with the reference voltage The comparison yields an error signal, which is then processed by a PI controller 1020 to output a constant duty cycle signal. Based on this constant duty cycle signal The PWM drive signals for four switching transistors S1 to S4 are generated by carrier phase shifting. Since the filter inductor L operates in discontinuous current mode (DCM), the current periodically returns to zero. The peak value of the inductor current in each switching cycle is proportional to the instantaneous input voltage at that moment. The average value envelope of the inductor current is naturally sinusoidal and in phase with the input voltage. Therefore, high power factor correction can be achieved without additional current sampling and current loop control. At the same time, the switching transistors turn on when the inductor current is zero, achieving zero current turn-on (ZCS) and reducing switching losses.

[0096] like Figure 18 As shown, this converter adopts a constant duty cycle single-voltage closed-loop control strategy. Its control loop includes a first adder 1010, a PI regulator 1020, a limiter 1030, a first comparator 1040, a second adder 1060, an inverter 1070, and a second comparator 1080.

[0097] The specific working process is as follows: The first adder 1010 receives the reference voltage. and output DC voltage The sampled values ​​are compared by subtracting the two to obtain an error signal; the error signal is sent to the PI regulator 1020 for processing and outputs a duty cycle signal Dt; the duty cycle signal Dt is limited by the limiter 1030 and then used as a comparison reference to be sent to the positive input terminal of the first comparator 1040 and the positive input terminal of the second comparator 1080 respectively.

[0098] Simultaneously, the system generates a sawtooth wave carrier signal. This sawtooth wave carrier is divided into two paths: the first path is directly fed into the negative phase input of the first comparator 1040, compared with the limited duty cycle signal, and outputs a PWM drive signal to drive the first switch S1 and the fourth switch S4; the second path is fed into the positive terminal of the second adder 1060, subtracted from the carrier magnitude M input to its negative terminal, and the result is inverted by the inverter 1070 and fed into the negative phase input of the second comparator 1080, compared with the limited duty cycle signal, and outputs a PWM drive signal to drive the second switch S2 and the third switch S3. Through the aforementioned carrier wave operation and control, two sets of drive signals that satisfy the operating timing of the full-bridge energy storage inverter circuit are generated. Through the carrier wave phase-shifting operation, the second equivalent carrier signal is offset by half a switching cycle (i.e., a phase shift of 180°) relative to the first carrier signal, thus creating a half-cycle phase difference between the drive signals of the first switch S1 and the fourth switch S4 and the drive signals of the second switch S2 and the third switch S3. By controlling the carrier wave operation, two sets of drive signals that satisfy the operating timing of the full-bridge energy storage inverter circuit are generated, simultaneously achieving output voltage regulation and power factor correction without the need for current sampling.

[0099] In summary, this single-stage isolated Boost-type PFC converter, through the power device multiplexing of the full-bridge energy storage inverter module 500, simultaneously achieves three major functions in single-stage power conversion: Boost boost energy storage, isolated inverter energy transfer, and power factor correction. Combined with the voltage spike suppression and energy feedback of the active clamp module 400, and the constant duty cycle single-voltage closed-loop control in DCM mode, it achieves high-efficiency, high-power-density, low-cost, and simple-to-control AC-CDC power conversion, making it an effective solution for high-power-density AC-CDC brick power modules.

[0100] The specific embodiments described above do not constitute a limitation on the scope of protection of this application. Any other corresponding changes and modifications made based on the technical concept of this application should be included within the scope of protection of this application.

Claims

1. A single-stage isolated Boost-type PFC converter, characterized in that, It includes an input filter module (200), a rectifier module (300), a full-bridge energy storage inverter module (500), an isolation transformer (600), a secondary rectifier module (700), and an output filter module (800) connected in sequence, as well as an active clamping module (400) connected in parallel on the DC bus between the output terminal of the rectifier module (300) and the input terminal of the full-bridge energy storage inverter module (500); The input filtering module (200) includes filter inductors (L) connected in series with each phase of the AC power supply (100); The full-bridge energy storage inverter module (500) includes a full-bridge circuit composed of a first switch (S1), a second switch (S2), a third switch (S3), and a fourth switch (S4). The midpoints of the two bridge arms of the full-bridge circuit are respectively connected to the two ends of the primary winding (N1) of the isolation transformer (600). The full-bridge energy storage inverter module (500) is configured such that, in the first operating state, the first switch (S1), the second switch (S2), the third switch (S3), and the fourth switch (S4) are simultaneously turned on, making the two ends of the primary winding (N1) of the isolation transformer (600) at the same potential, and the filter inductor (L) forms a charging circuit through the rectifier module (300) and the full-bridge energy storage inverter module (500) to store energy; in the second operating state, one set of diagonal switches of the full-bridge circuit is turned on and the other set of diagonal switches is turned off, so that the energy released by the filter inductor (L) is superimposed with the electrical energy continuously input by the AC power supply (100) through the rectifier module (300) and then transferred to the secondary side through the isolation transformer (600); The first and second operating states alternate within one switching cycle, thereby simultaneously achieving boost energy storage and isolated inverter energy transfer in a single-stage power conversion.

2. The single-stage isolated Boost-type PFC converter according to claim 1, characterized in that, The inductance value of the filter inductor (L) and switching frequency The filter inductor (L) is configured to operate in discontinuous current mode within the rated load range of the converter; in discontinuous current mode, the current of the filter inductor (L) starts from zero in each switching cycle and flows at a slope during the first operating state. Linear rise to peak It decreases linearly during the second operating state and returns to zero before the end of the switching cycle; in The instantaneous input voltage after rectification. The duty cycle of the full-bridge energy storage inverter module (500) is given.

3. The single-stage isolated Boost-type PFC converter according to claim 2, characterized in that, The converter further includes a constant duty cycle single-voltage closed-loop control module, which includes: The voltage sampling unit is used to sample the DC voltage at the output terminal of the output filter module (800). ; The first adder (1010) is used to convert the DC voltage... With reference voltage The error signal is obtained through comparison; A PI controller (1020) is used to process the error signal and output a constant duty cycle signal. ; A carrier phase-shifting drive unit is used to drive the signal based on the constant duty cycle. By offsetting the two sawtooth wave carrier signals by half a switching cycle to perform carrier phase shifting, PWM drive signals for the first switch (S1) to the fourth switch (S4) are generated.

4. The single-stage isolated Boost-type PFC converter according to claim 3, characterized in that, The AC power supply (100) is a three-phase AC power supply, and the voltage ratio of the converter is... It is configured to satisfy 1.0 ≤ M ≤ 2.5 so that the power factor PF of the converter is ≥ 0.95; wherein The turns ratio of the isolation transformer (600) is given. To output DC voltage, D is the peak value of the three-phase input phase voltage, and D is the duty cycle of the full-bridge energy storage inverter module (500).

5. The single-stage isolated Boost-type PFC converter according to claim 1, characterized in that, The active clamping module (400) includes a clamping capacitor (Cdc) and a clamping switch (S9). One end of the clamping capacitor (Cdc) is connected to the positive terminal of the DC bus between the positive output terminal of the rectifier module (300) and the positive input terminal of the full-bridge energy storage inverter module (500). The other end of the clamping capacitor (Cdc) is connected to the negative terminal of the DC bus of the negative output terminal of the rectifier module (300) via the clamping switch (S9). The active clamping module (400) is configured such that: during the first operating state, when the bus voltage of the full-bridge energy storage inverter module (500) spikes due to the leakage inductance of the isolation transformer (600) and exceeds the voltage of the clamping capacitor (Cdc), the body diode of the clamping switch (S9) is forward-biased, and the clamping capacitor (Cdc) absorbs the spike energy for charging; during the second operating state, the clamping switch (S9) is controlled to conduct, and the energy stored in the clamping capacitor (Cdc) is fed back to the isolation transformer (600) via the clamping switch (S9).

6. The single-stage isolated Boost-type PFC converter according to claim 1, characterized in that, The full-bridge energy storage inverter module (500) sequentially experiences the following modes within one switching cycle, wherein mode one and mode three correspond to the first operating state, and mode two and mode four correspond to the second operating state: Mode 1: The first switch (S1), the second switch (S2), the third switch (S3) and the fourth switch (S4) are turned on simultaneously, the primary winding (N1) of the isolation transformer (600) is short-circuited, and the current of the filter inductor (L) rises linearly to store energy. Mode 2: The first switch (S1) and the third switch (S3) are turned on, the second switch (S2) and the fourth switch (S4) are turned off, the primary winding (N1) of the isolation transformer (600) is subjected to a positive voltage, the filter inductor (L) releases energy, the energy is transferred to the secondary side through the isolation transformer (600), and the current of the filter inductor (L) decreases linearly. Mode 3: The first switch (S1), the second switch (S2), the third switch (S3), and the fourth switch (S4) are turned on simultaneously again, and the filter inductor (L) stores energy again, with the working state being the same as in Mode 1; Mode 4: The second switch (S2) and the fourth switch (S4) are turned on, the first switch (S1) and the third switch (S3) are turned off, the primary winding (N1) of the isolation transformer (600) is subjected to reverse voltage, the filter inductor (L) releases energy, the energy is transferred to the secondary side through the isolation transformer (600), and the current of the filter inductor (L) decreases linearly. In particular, the voltage polarity of the primary winding (N1) of the isolation transformer (600) in Mode 2 and Mode 4 is opposite, so that the magnetic core of the isolation transformer (600) is alternately magnetized in the positive and negative directions.

7. The single-stage isolated Boost-type PFC converter according to claim 1, characterized in that, The AC power supply (100) is a three-phase AC power supply, and the rectifier module (300) is a three-phase full-bridge rectifier circuit composed of six rectifier devices; or, the AC power supply (100) is a single-phase AC power supply, and the rectifier module (300) is a single-phase full-bridge rectifier circuit composed of four rectifier devices; the rectifier devices are rectifier diodes or MOSFETs.

8. The single-stage isolated Boost-type PFC converter according to claim 7, characterized in that, When the AC power supply (100) is a single-phase AC power supply, the filter inductor (L) is located on the AC input side or DC output side of the rectifier module (300).

9. The single-stage isolated Boost-type PFC converter according to claim 1, characterized in that, The secondary-side rectifier module (700) is one of the following: A full-bridge rectifier circuit consisting of four rectifier devices (S5~S8), wherein the isolation transformer (600) has a single winding (N2) on its secondary side; or A full-wave rectifier circuit consisting of two rectifier devices, wherein the isolation transformer (600) has a winding with a center tap on its secondary side; The rectifier is a rectifier diode or a MOSFET; when the rectifier is a MOSFET, the secondary rectifier module (700) operates in synchronous rectification mode.

10. The single-stage isolated Boost-type PFC converter according to claim 1, characterized in that, The output filtering module (800) is one of the following: A C-type filter circuit consisting of a single output filter capacitor (C2), wherein the output filter capacitor (C2) is connected in parallel to the output terminal of the secondary rectifier module (700); or A CLC-type π filter circuit is formed by connecting a pre-stage filter capacitor, an output filter inductor, and a post-stage filter capacitor in sequence.

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