A single-stage resonant AC-DC converter device with integrated Buck-boost unit

Abstract

This invention relates to the field of switching power supply technology and discloses a single-stage resonant AC-DC converter device with an integrated Buck-boost unit. The device includes a single-stage resonant AC-DC converter with an integrated Buck-boost unit and a control circuit. It solves the technical problems of existing AC-DC converters, such as complex two-stage structures, large single-stage resonant cavity current, low power factor, and high total harmonic distortion. The single-stage resonant AC-DC converter with an integrated Buck-boost unit includes a filter, an input rectifier, and a filter capacitor C. in First switch arm, second switch arm, capacitor C b Inductor L b Resonant inductor L r and resonant capacitor C r The components include a resonant cavity, a transformer T, an output rectifier, and an output capacitor C. o This invention eliminates energy backflow, achieving low resonant cavity current, high power factor, and low THD. Furthermore, it features a small frequency variation range for the switching transistor, facilitates soft switching, and simplifies the structure. It can be applied to data center server power supplies, vehicle chargers, power adapters, and other fields, demonstrating significant engineering application value.

Description

Technical Field

[0001] This invention relates to a single-stage resonant AC-DC converter device with an integrated Buck-boost unit, which can be applied to AC-DC power conversion fields such as data center server power supplies, on-board chargers, charging piles, and adapters, and belongs to the field of switching power supply technology. Background Technology

[0002] In recent years, with the rapid development of the power electronics industry, switching converters have been increasingly widely used, and high power density and high efficiency have become industry trends. Among them, AC-DC converters are widely used in adapters, on-board chargers and charging piles, data center server power supplies, and other fields.

[0003] Currently, mainstream AC-DC converters are mainly divided into two categories: two-stage architecture and single-stage architecture. A two-stage AC-DC converter consists of a front-stage power factor correction circuit and a rear-stage isolated DC-DC converter. The front-stage circuit corrects the power factor, reduces grid harmonic pollution, and outputs a stable DC bus voltage, while the rear-stage circuit provides electrical isolation and output voltage regulation. This architecture allows for independent optimization of the two stages, achieving high efficiency and power factor. However, it suffers from a large number of power devices and energy storage components, resulting in high circuit cost and large size, making it difficult to meet the demands of high-power-density applications.

[0004] like Figure 1 The two-stage architecture shown includes a front-end power factor correction circuit and a rear-end isolated DC-DC converter. The power factor correction circuit primarily corrects the power factor of the input current, reducing harmonic pollution to the power grid and generating a more stable DC bus voltage. The isolated DC-DC converter provides electrical isolation and output voltage regulation. This two-stage architecture allows for separate optimization of the two circuits, achieving higher efficiency and power factor. However, the two-stage circuitry involves more power devices and energy storage components, resulting in higher circuit cost and size.

[0005] Single-stage AC-DC converters integrate power factor correction and DC-DC conversion functions, reducing the number of power devices and lowering circuit cost and size, making them the development direction for high power density converters. Existing single-stage AC-DC converters mostly employ an LLC resonant converter topology, with a small-value capacitor connected in parallel at the output of the input rectifier to directly input the rectified sinusoidal half-wave voltage into the LLC resonant converter, simultaneously achieving power factor correction and voltage regulation. However, this topology has an inherent contradiction between gain and resonant cavity current: near the zero-crossing point of the sinusoidal half-wave voltage, a near-infinite voltage gain is required. To achieve this gain, the transformer's magnetizing inductance must be reduced, directly causing a significant increase in the resonant cavity current; simultaneously, the frequency range of the switching transistors needs to be significantly widened, making it difficult to improve converter efficiency.

[0006] like Figure 2 The single-stage AC-DC converter structure shown can reduce the number of power devices, thereby reducing circuit cost and size. A small-value capacitor is connected in parallel at the output of the input rectifier. The AC input voltage is rectified by the input rectifier to generate a sinusoidal half-wave voltage. The subsequent DC-DC converter often uses an LLC resonant converter with soft-switching characteristics to convert the sinusoidal half-wave voltage into a DC output voltage, while simultaneously achieving power factor correction of the AC input. However, there is a certain trade-off between the gain range of the LLC resonant converter and the resonant cavity current. Especially near the zero-crossing point of the sinusoidal half-wave voltage, a near-infinite voltage gain is required. To achieve this voltage gain, the magnetizing inductance of the transformer must be reduced sufficiently, resulting in an increase in the resonant cavity current. Furthermore, a very wide frequency range is required, making it difficult to improve the converter efficiency.

[0007] To address the aforementioned issues with LLC single-stage converters, the inventor's prior patent ZL202511334461.7 discloses a single-stage AC-DC converter with an integrated Boost unit. This Boost circuit increases the equivalent voltage across the resonant cavity, reducing the resonant cavity current and narrowing the frequency variation range of the switching transistors. However, in this topology, the capacitor voltage of the Boost circuit is higher than the rectifier bridge output voltage. During the freewheeling phase of the switching transistors, the energy of the Boost capacitor flows back to the filter capacitor after the rectifier bridge, preventing the filter capacitor voltage from dropping to zero near the zero-crossing of the input voltage. This results in a significant decrease in the converter's power factor (PF) and a substantial increase in total harmonic distortion (THD). This problem is even more pronounced under light load conditions, severely impacting the converter's grid adaptability.

[0008] In summary, existing AC-DC converters all suffer from technical defects: two-stage structures are complex, costly, and bulky; traditional single-stage LLC converters have large resonant cavity currents, wide switching frequency ranges, and low efficiency; and improved single-stage converters with integrated Boost cells suffer from energy backflow problems, resulting in low power factor and high THD. Currently, no single-stage AC-DC converter can simultaneously achieve low resonant cavity current, high power factor, low THD, and a narrow switching frequency range, making this a pressing technical problem to be solved in this field. Summary of the Invention

[0009] To overcome the shortcomings of existing AC-DC converters, such as the complexity, high cost, and large size of two-stage structures, and the large resonant cavity current, wide switching frequency range, energy backflow, low power factor, and large total harmonic distortion of single-stage resonant converters, this invention provides a single-stage resonant AC-DC converter device integrating a Buck-boost unit. This achieves the technical goals of low resonant cavity current, high power factor, low THD, and narrow switching frequency range under a single-stage architecture, while simplifying the control strategy and improving the converter's efficiency and adaptability to different operating conditions.

[0010] A single-stage resonant AC-DC converter device with integrated Buck-boost unit, comprising: a single-stage resonant AC-DC converter with integrated Buck-boost unit and a control circuit, wherein the single-stage resonant AC-DC converter with integrated Buck-boost unit includes: A filter, whose input is connected to the AC power grid, is used to filter out interference from the subsequent conversion circuit and reduce harmonic pollution to the power grid. The input rectifier is connected to the output of the filter to rectify the AC input voltage. Filter capacitor C in It is connected in parallel to the output of the input rectifier to filter out the high-frequency current of its subsequent circuits; The first switching bridge arm is composed of switching transistors Q1 and Q2. The drain of switching transistor Q1 is connected to the positive output terminal of the input rectifier 102, and the source of switching transistor Q1 is connected to the drain of switching transistor Q2 to form the midpoint of the first switching bridge arm. The source of switching transistor Q2 is connected to the negative output terminal of the input rectifier 102 and the primary power ground. The second switching bridge arm is composed of switching transistors Q3 and Q4. The drain of switching transistor Q3 is connected to the positive output terminal of the input rectifier 102, and the source of switching transistor Q3 is connected to the drain of switching transistor Q4, forming the midpoint of the second switching bridge arm. Inductor L b One end is connected to the source of switching transistor Q3 and the drain of switching transistor Q4, and the other end is connected to the primary power ground. Capacitor C b , with inductor L b The second switching bridge arm constitutes a Buck-boost circuit; capacitor C b The negative terminal is connected to the source of the switching transistor Q4, and the positive terminal is connected to the primary power ground; Resonant inductor L r and resonant capacitor C r The resonant cavity 103 is composed of a resonant inductor L. r One end is connected to the midpoint of the first switch bridge arm, and the resonant inductance L r The other end is connected to the resonant capacitor C. r One end, resonant capacitor C rThe other end is connected to one end of the primary winding of transformer T, and the other end of the primary winding of transformer T is connected to the midpoint of the second switch bridge arm. A transformer T includes at least one primary winding and one secondary winding, serving the functions of electrical isolation and power transmission. The output rectifier is coupled to the secondary winding of transformer T at its input terminal and is used to rectify the AC voltage output from the secondary winding of transformer T into DC voltage. Output capacitor C o It is connected in parallel with the output terminal of the output rectifier to filter out the high-frequency current component in the output rectifier.

[0011] The first and second switch arms form a primary-side switching network. Control signals from the control circuit are received to control the first and second switch arms, generating alternating high-frequency pulse voltage signals between the midpoints of the first and second switch arms. The level of these high-frequency pulse voltage signals varies depending on the duty cycle of the second switch arm. v in+ v cb - v in 0 v cb There are four or three of them.

[0012] The output rectifier is a full-bridge rectifier circuit, a voltage doubler rectifier circuit, a full-wave rectifier circuit, or other rectifier circuit structures.

[0013] The rectifier elements in the input rectifier and output rectifier are diodes or MOSFETs.

[0014] The resonant inductor L r The leakage inductance of transformer T can be used as a substitute.

[0015] In another case, a single-stage resonant AC-DC converter device with integrated Buck-boost unit includes a single-stage resonant AC-DC converter with integrated Buck-boost unit and a control circuit. Includes a single-stage resonant AC-DC converter and control circuit with integrated Buck-boost unit; The single-stage resonant AC-DC converter with integrated Buck-boost unit includes: A filter, whose input is connected to the AC power grid, is used to filter out interference from the subsequent conversion circuit and reduce harmonic pollution to the power grid. The input rectifier is connected to the output of the filter to rectify the AC input voltage. Filter capacitor C inIt is connected in parallel to the output of the input rectifier to filter out the high-frequency current of its subsequent circuits; The first switching bridge arm is composed of switching transistors Q1 and Q2. The drain of switching transistor Q1 is connected to the positive output terminal of the input rectifier, and the source of switching transistor Q1 is connected to the drain of switching transistor Q2, forming the midpoint of the first switching bridge arm. The source of switching transistor Q2 is connected to the negative output terminal of the input rectifier and the primary power ground. The second switching bridge arm is composed of switching transistors Q3 and Q4. The drain of switching transistor Q3 is connected to the positive output terminal of the input rectifier, and the source of switching transistor Q3 is connected to the drain of switching transistor Q4, forming the midpoint of the second switching bridge arm. Inductor L b One end is connected to the source of switching transistor Q3 and the drain of switching transistor Q4, and the other end is connected to the primary power ground. Capacitor C b , with inductor L b The second switching bridge arm constitutes a Buck-boost circuit; capacitor C b The negative terminal is connected to the source of the switching transistor Q4, and the positive terminal is connected to the primary power ground; Transformer T includes at least one primary winding and one secondary winding. The same-name terminal of the primary winding of transformer T is connected to the midpoint of a first switching bridge arm, and a DC blocking capacitor C is connected between the opposite-name terminal of the primary winding of transformer T and the midpoint of a second switching bridge arm. s It serves to provide electrical isolation and power transmission; Resonant inductor L r and resonant capacitor C r The resonant cavity is formed and located on the secondary side of transformer T, with resonant inductance L. r One end is connected to the corresponding terminal of the secondary winding of transformer T, and the resonant inductor L r The other end is connected to the resonant capacitor C. r One end, resonant capacitor C r The other end serves as an input terminal of the output rectifier; The output rectifier has another input terminal that is the opposite terminal of the secondary winding of transformer T, which is used to rectify the AC voltage output from the secondary winding of transformer into DC voltage. Output capacitor C o It is connected in parallel with the output terminal of the output rectifier to filter out the high-frequency current component in the output rectifier.

[0016] The control circuit includes an outer voltage loop and an inner current loop. By detecting the DC output voltage amplitude, AC input voltage, and AC input current, it dynamically adjusts the duty cycle of the second switching arm switch transistor within the AC input voltage cycle, thereby regulating the midpoint voltage of the switching arm. v abAnd the resonant cavity current, to realize the regulation of output voltage or output current and control of AC input current waveform, that is, to realize output voltage regulation or constant current and power factor correction functions.

[0017] Preferably, the two switches of the first bridge arm switch adopt a complementary turn-on method with a certain dead time, and the duty cycle of the switch is close to 50%.

[0018] Preferably, the control circuit further includes an input voltage sampling circuit, a current sampling circuit, and an output voltage sampling circuit. The input voltage sampling circuit acquires an AC input voltage signal, the current sampling circuit acquires an AC input current signal, and the output voltage sampling circuit acquires a DC output voltage signal.

[0019] Compared with the prior art, the technical solution of the present invention has the following outstanding technical effects, and the effects work synergistically, making it comprehensively superior to existing AC-DC converters: 1. Completely eliminates energy backflow, achieving high power factor and low THD: The Buck-boost unit topology design of this invention fundamentally eliminates the energy storage inductor L. b To the filter capacitor C in The energy return path is such that there is no energy return phenomenon in all operating modes, which makes the filter capacitor C... in The voltage can drop to zero near the zero-crossing of the input voltage, the AC input current waveform is highly synchronized with the input voltage waveform, the power factor is greatly improved, the total harmonic distortion of the current is significantly reduced, and it can still maintain excellent grid adaptability under light load conditions, thus solving the core technical defects of existing improved single-stage converters.

[0020] 2. Reduce resonant cavity current and narrow the frequency variation range of the switching transistor: By providing an appropriate input voltage to the resonant cavity through the Buck-boost unit, the input voltage amplitude of the resonant cavity is effectively increased. The required voltage gain can be achieved without reducing the excitation inductance of the transformer. The resonant cavity current is greatly reduced, and the frequency variation range of the switching transistor is greatly reduced. It can even achieve fixed frequency control, which solves the inherent contradiction between gain and current in traditional single-stage LLC converters.

[0021] 3. Simple control strategy, easy to implement soft switching, and high converter efficiency: The first switching arm adopts a complementary turn-on control method with a duty cycle of nearly 50%, while the second switching arm only needs to dynamically adjust the duty cycle. The overall control strategy is simple and easy to implement in engineering. The presence of the resonant cavity, combined with the narrow frequency variation range, makes it easy for the switching transistor to achieve soft switching with zero voltage turn-on / zero current turn-off under all operating conditions, which greatly reduces switching losses and improves the overall efficiency of the converter.

[0022] 4. Simplified circuit structure, achieving high power density and low cost: This invention is a single-stage architecture that integrates power factor correction and DC-DC conversion functions, reducing the number of components in the power conversion circuit by one stage compared to a two-stage converter; at the same time, the resonant inductor can be replaced by the leakage inductance of a transformer, further reducing the number of independent components, simplifying the circuit structure, reducing the size and cost, and meeting the application requirements of high power density.

[0023] 5. Strong adaptability to operating conditions and wide range of application scenarios: This invention can maintain excellent performance of low resonant cavity current, high power factor and low THD in the full voltage input range and the full load range from light load to full load. It can be widely used in AC-DC power conversion fields such as data center server power supply, vehicle charger, charging pile, and adapter, and has significant engineering application value and market prospects. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art 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.

[0025] Figure 1 This is a structural diagram of a traditional two-stage AC-DC converter; Figure 2 This is a schematic diagram of the structure of a prior art single-stage AC-DC converter; Figure 3 The diagram shows the structure of a single-stage AC-DC converter disclosed in existing patent ZL202511334461.7. Figure 4 for Figure 3 A schematic diagram of power recirculation in a single-stage AC-DC converter is shown. Figure 5 This is a schematic diagram of the structure of a single-stage resonant AC-DC converter device with integrated Buck-boost unit according to Embodiment 1 of the present invention; Figure 6 This is a waveform diagram of a switching transistor driving a single-stage resonant AC-DC converter with an integrated Buck-boost unit according to the present invention. Figure 7 This is an equivalent circuit diagram of a single-stage resonant AC-DC converter with integrated Buck-boost unit in operating mode 1 according to the present invention. Figure 8 This is an equivalent circuit diagram of a single-stage resonant AC-DC converter with integrated Buck-boost unit in operating mode 2 according to the present invention. Figure 9 This is an equivalent circuit diagram of a single-stage resonant AC-DC converter with integrated Buck-boost unit in operating mode 3 according to the present invention. Figure 10 This is an equivalent circuit diagram of a single-stage resonant AC-DC converter with integrated Buck-boost unit in operating mode 4 according to the present invention. Figure 11 This is another switching transistor drive waveform diagram of a single-stage resonant AC-DC converter with integrated Buck-boost unit according to the present invention; Figure 12 This is a third switching transistor drive waveform diagram of a single-stage resonant AC-DC converter with integrated Buck-boost unit according to the present invention. Figure 13 This is a schematic diagram of embodiment 2 of the single-stage resonant AC-DC converter with integrated Buck-boost unit according to the present invention.

[0026] In the diagram: 101 - Filter; 102 - Input rectifier; 103 - Resonant cavity; 104 - Output rectifier; 100 - Control circuit Detailed Implementation

[0027] 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.

[0028] Example 1: Reference Figure 5 The present invention provides a single-stage resonant AC-DC converter device with integrated Buck-boost unit, comprising a single-stage resonant AC-DC converter with integrated Buck-boost unit and a control circuit 100, wherein: The single-stage resonant AC-DC converter with integrated Buck-boost unit includes: Filter 101, whose input is connected to the AC power grid, is used to filter out interference from the subsequent conversion circuit and reduce harmonic pollution to the power grid. The input rectifier 102 is connected to the output of the filter to rectify the AC input voltage; Filter capacitor C in It is connected in parallel to the output of the input rectifier to filter out the high-frequency current of its subsequent circuits; The first switching bridge arm is composed of switching transistors Q1 and Q2. The drain of switching transistor Q1 is connected to the positive output terminal of the input rectifier 102, and the source of switching transistor Q1 is connected to the drain of switching transistor Q2 to form the midpoint of the first switching bridge arm. The source of switching transistor Q2 is connected to the negative output terminal of the input rectifier 102 and the primary power ground. The second switching bridge arm is composed of switching transistors Q3 and Q4. The drain of switching transistor Q3 is connected to the positive output terminal of the input rectifier 102, and the source of switching transistor Q3 is connected to the drain of switching transistor Q4, forming the midpoint of the second switching bridge arm. Inductor L b One end is connected to the source of switching transistor Q3 and the drain of switching transistor Q4, and the other end is connected to the primary power ground. Capacitor C b , with inductor L b The second switching bridge arm constitutes a Buck-boost circuit; capacitor C b The negative terminal is connected to the source of the switching transistor Q4, and the positive terminal is connected to the primary power ground; Resonant inductor L r and resonant capacitor C r The resonant cavity 103 is composed of a resonant inductor L. r One end is connected to the midpoint of the first switch bridge arm, and the resonant inductance L r The other end is connected to the resonant capacitor C. r One end, resonant capacitor C r The other end is connected to one end of the primary winding of transformer T, and the other end of the primary winding of transformer T is connected to the midpoint of the second switch bridge arm. A transformer T includes at least one primary winding and one secondary winding, serving the functions of electrical isolation and power transmission. The output rectifier 104 has its input terminal coupled to the secondary winding of the transformer T, and is used to rectify the AC voltage output from the secondary winding of the transformer into DC voltage. Output capacitor C o It is connected in parallel with the output terminal of the output rectifier to filter out the high-frequency current component in the output rectifier.

[0029] The first and second switch arms form a primary-side switching network. Control signals from the control circuit 100 are received to control the first and second switch arms, generating alternating high-frequency pulse voltage signals between the midpoints of the first and second switch arms. The level of these high-frequency pulse voltage signals varies depending on the duty cycle of the second switch arm. v in+ v cb - v in 0 v cb There are four or three of them.

[0030] In one embodiment, the output rectifier 104 is a full-bridge rectifier circuit.

[0031] In one embodiment, the output rectifier 104 is a voltage doubler rectifier circuit.

[0032] In one embodiment, the output rectifier 104 is a full-wave rectifier circuit.

[0033] The rectifier elements in the input rectifier 102 and the output rectifier 104 are diodes.

[0034] The rectifier elements in the input rectifier 102 and the output rectifier 104 are MOSFETs.

[0035] The resonant inductor L r The leakage inductance of transformer T can be used as a substitute.

[0036] The control circuit 100 includes an outer voltage loop and an inner current loop. By detecting the DC output voltage amplitude, AC input voltage, and AC input current, it dynamically adjusts the duty cycle of the second switch arm switching transistor within the AC input voltage cycle, thereby regulating the midpoint voltage of the switch arm. v ab And the resonant cavity current, to realize the regulation of output voltage or output current and control of AC input current waveform, that is, to realize output voltage regulation or constant current and power factor correction functions.

[0037] In one embodiment, the two switches of the first bridge arm switch are turned on in a complementary manner with a certain dead time, and the duty cycle of the switch is close to 50%.

[0038] The control circuit 100 further includes an input voltage sampling circuit, a current sampling circuit, and an output voltage sampling circuit.

[0039] As those skilled in this technical field know: The circuit structure of the output rectifier 104 can be one of the existing full-bridge rectifier circuit, voltage doubler rectifier circuit, full-wave rectifier circuit, or other rectifier circuit structures.

[0040] The rectifier elements in the input rectifier 102 and the output rectifier 104 are diodes or MOSFETs.

[0041] The resonant inductor L r The leakage inductance of transformer T can be used as a substitute.

[0042] See Figure 6The diagram shows a switching transistor drive waveform of the single-stage resonant AC-DC converter with integrated Buck-boost unit of the present invention. Ignoring the transition state in the dead interval, the converter has four operating modes depending on the operating state of the switching transistor: (1) Mode 1: In this operating mode, both switching transistors Q1 and Q3 are turned on. The equivalent circuit of the converter is as follows: Figure 7 As shown. In this mode, the inductor L b exist v in Excitation is performed on the storage under excitation; the voltage difference at the midpoint of the two switching bridge arms. v ab equal 0 ; Transformer primary resonant inductance L r and C r The resonance occurs through the primary circuit formed by the transformer windings and the short circuit of Q1 and Q3, and the secondary diode D of the transformer resonates. o2 and D o3 When the circuit is turned on, the energy transferred from the primary side of the transformer is transferred to the output capacitor C. o and load.

[0043] (2) Mode 2: In this operating mode, both switching transistors Q2 and Q3 are turned on. The equivalent circuit of the converter is as follows: Figure 8 As shown. In this mode, the inductor L b Continue in v in Excitation is performed on the storage under excitation; the voltage difference at the midpoint of the two switching bridge arms. v ab equal- v in ; Transformer primary resonant inductance L r and C r Resonance, transformer secondary diode D o2 and D o3 Keeping the circuit open, the energy transferred from the primary side of the transformer is transferred to the output capacitor C. o and load.

[0044] (3) Mode 3: In this operating mode, both switching transistors Q2 and Q4 are turned on. The equivalent circuit of the converter is as follows: Figure 9 As shown. In this mode, the inductor L b The energy stored in the capacitor C b Release; voltage difference at the midpoint of the two switching bridge arms v ab equal v cb ; Transformer primary resonant inductance L r and C r Resonance, transformer secondary diode D o1 and Do4 When the circuit is turned on, the energy transferred from the primary side of the transformer is transferred to the output capacitor C. o and load.

[0045] (4) Mode 4: In this operating mode, both switching transistors Q1 and Q4 are turned on. The equivalent circuit of the converter is as follows: Figure 10 As shown. In this mode, the inductor L b The energy stored in it continues to flow to capacitor C. b Release; voltage difference at the midpoint of the two switching bridge arms v ab equal v in +v cb ; Transformer primary resonant inductance L r and C r Resonance, transformer secondary diode D o1 and D o4 The circuit remains open, transferring the energy from the primary side of the transformer to the output capacitor C. o and load.

[0046] See Figure 11 The diagram shows a switching transistor drive waveform of the single-stage resonant AC-DC converter with integrated Buck-boost unit of the present invention. In this waveform, switching transistor Q3 has a very large duty cycle, typically occurring near the zero-crossing point of the AC input voltage. Under these conditions, the single-stage resonant AC-DC converter with integrated Buck-boost unit only has three operating modes: Mode 1, Mode 2, and Mode 4. Accordingly, v ab The voltage level includes 0, - v in and v in +v cb Three types.

[0047] See Figure 12 The diagram shows a switching transistor drive waveform for a single-stage resonant AC-DC converter with an integrated Buck-boost unit according to the present invention. In this waveform, switching transistor Q3 has a small duty cycle, typically occurring in applications with low voltage gain. Under these conditions, the single-stage resonant AC-DC converter with the integrated Buck-boost unit only has three operating modes: Mode 1, Mode 3, and Mode 4. Accordingly, v ab The level includes 0, v cb and v in +v cb Three types.

[0048] See Figures 7-10 There are four operating modes, and it is evident that inductance L will not appear in any of them. b The energy flows back to the filter capacitor C in Therefore, the single-stage resonant AC-DC converter with integrated Buck-boost unit of the present invention can achieve a high power factor and low THD.

[0049] Example 2: refer to Figure 13 Another embodiment of the present invention is shown, wherein the resonant cavity 103 can be placed on the secondary side of the transformer, and a DC blocking capacitor C is added on the primary side of the transformer. s Specifically, a DC blocking capacitor C is connected between the same-name terminal of the primary winding of transformer T and the midpoint of the first switch bridge arm, and between the opposite-name terminal of the primary winding of transformer T and the midpoint of the second switch bridge arm. s The circuit working principle of this embodiment is the same as... Figure 5 The embodiment shown is basically the same as that in Example 1, and will not be described again here.

[0050] Compared to existing single-stage AC-DC converters, the integrated Buck-boost unit single-stage resonant AC-DC converter of this invention solves the problem of excessive resonant cavity current, improves power factor, and reduces THD. Simultaneously, it features a simple control strategy, a small frequency range variation in the switching transistors, and easy soft-switching, thus easily achieving high efficiency and possessing significant engineering application value and market prospects.

[0051] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A single-stage resonant AC-DC converter device integrating a Buck-boost unit, characterized in that: Includes a single-stage resonant AC-DC converter and control circuit with integrated Buck-boost unit; The single-stage resonant AC-DC converter with integrated Buck-boost unit includes: A filter, whose input is connected to the AC power grid, is used to filter out interference from the subsequent conversion circuit and reduce harmonic pollution to the power grid. The input rectifier is connected to the output of the filter to rectify the AC input voltage. Filter capacitor C in It is connected in parallel to the output of the input rectifier to filter out the high-frequency current of its subsequent circuits; The first switching bridge arm is composed of switching transistors Q1 and Q2. The drain of switching transistor Q1 is connected to the positive output terminal of the input rectifier, and the source of switching transistor Q1 is connected to the drain of switching transistor Q2, forming the midpoint of the first switching bridge arm. The source of switching transistor Q2 is connected to the negative output terminal of the input rectifier and the primary power ground. The second switching bridge arm is composed of switching transistors Q3 and Q4. The drain of switching transistor Q3 is connected to the positive output terminal of the input rectifier, and the source of switching transistor Q3 is connected to the drain of switching transistor Q4, forming the midpoint of the second switching bridge arm. Inductor L b One end is connected to the source of switching transistor Q3 and the drain of switching transistor Q4, and the other end is connected to the primary power ground. Capacitor C b , with inductor L b The second switching bridge arm constitutes a Buck-boost circuit; capacitor C b The negative terminal is connected to the source of the switching transistor Q4, and the positive terminal is connected to the primary power ground. Resonant inductor L r and resonant capacitor C r The resonant cavity is composed of resonant inductance L. r One end is connected to the midpoint of the first switch bridge arm, and the resonant inductance L r The other end is connected to the resonant capacitor C. r One end, resonant capacitor C r The other end is connected to one end of the primary winding of transformer T, and the other end of the primary winding of transformer T is connected to the midpoint of the second switch bridge arm. A transformer T includes at least one primary winding and one secondary winding, serving the functions of electrical isolation and power transmission. The output rectifier has its input terminal coupled to the secondary winding of transformer T, and is used to rectify the AC voltage output from the secondary winding of transformer into DC voltage. Output capacitor C o It is connected in parallel with the output terminal of the output rectifier to filter out the high-frequency current component in the output rectifier.

2. The single-stage resonant AC-DC converter device with integrated Buck-boost unit according to claim 1, characterized in that: The first and second switch arms form a primary-side switching network. By receiving control signals output from the control circuit, the first and second switch arms are controlled, generating alternating high-frequency pulse voltage signals between the midpoints of the first and second switch arms. v ab Depending on the duty cycle of the different second switch arms, the level of the high-frequency pulse voltage signal is: v in+ v cb - v in 0 v cb There are four or three of them.

3. The single-stage resonant AC-DC converter device with integrated Buck-boost unit according to claim 1, characterized in that: The control circuit includes an outer voltage loop and an inner current loop. By detecting the DC output voltage amplitude, AC input voltage, and AC input current, it dynamically adjusts the duty cycle of the second switching arm switch transistor within the AC input voltage cycle, thereby regulating the midpoint voltage of the switching arm. v ab And the resonant cavity current, to realize the regulation of output voltage or output current and control of AC input current waveform, that is, to realize output voltage regulation or constant current and power factor correction functions.

4. A single-stage resonant AC-DC converter device integrating a Buck-boost unit according to claim 3, characterized in that: The control circuit further includes an input voltage sampling circuit, a current sampling circuit, and an output voltage sampling circuit. The input voltage sampling circuit acquires AC input voltage signals, the current sampling circuit acquires AC input current signals, and the output voltage sampling circuit acquires DC output voltage signals.

5. A single-stage resonant AC-DC converter device with integrated Buck-boost unit according to claim 1, characterized in that: The resonant inductor L r Replace it with the leakage inductance of transformer T.

6. The single-stage resonant AC-DC converter device with integrated Buck-boost unit according to claim 1, wherein the output rectifier is any one of a full-bridge rectifier circuit, a voltage doubler rectifier circuit, and a full-wave rectifier circuit.

7. A single-stage resonant AC-DC converter device with integrated Buck-boost unit according to claim 1, characterized in that: The rectifier elements in the input rectifier and output rectifier are diodes or MOSFETs.

8. A single-stage resonant AC-DC converter device integrating a Buck-boost unit, characterized in that: Includes a single-stage resonant AC-DC converter with integrated Buck-boost unit and control circuitry; Includes a single-stage resonant AC-DC converter with integrated Buck-boost unit and control circuitry; The single-stage resonant AC-DC converter with integrated Buck-boost unit includes: A filter, whose input is connected to the AC power grid, is used to filter out interference from the subsequent conversion circuit and reduce harmonic pollution to the power grid. The input rectifier is connected to the output of the filter to rectify the AC input voltage. Filter capacitor C in It is connected in parallel to the output of the input rectifier to filter out the high-frequency current of its subsequent circuits; The first switching bridge arm is composed of switching transistors Q1 and Q2. The drain of switching transistor Q1 is connected to the positive output terminal of the input rectifier, and the source of switching transistor Q1 is connected to the drain of switching transistor Q2, forming the midpoint of the first switching bridge arm. The source of switching transistor Q2 is connected to the negative output terminal of the input rectifier and the primary power ground. The second switching bridge arm is composed of switching transistors Q3 and Q4. The drain of switching transistor Q3 is connected to the positive output terminal of the input rectifier, and the source of switching transistor Q3 is connected to the drain of switching transistor Q4, forming the midpoint of the second switching bridge arm. Inductor L b One end is connected to the source of switching transistor Q3 and the drain of switching transistor Q4, and the other end is connected to the primary power ground. Capacitor C b , with inductor L b The second switching bridge arm constitutes a Buck-boost circuit; capacitor C b The negative terminal is connected to the source of the switching transistor Q4, and the positive terminal is connected to the primary power ground. Transformer T includes at least one primary winding and one secondary winding. The same-name terminal of the primary winding of transformer T is connected to the midpoint of a first switching bridge arm, and a DC blocking capacitor C is connected between the opposite-name terminal of the primary winding of transformer T and the midpoint of a second switching bridge arm. s It serves to provide electrical isolation and power transmission; Resonant inductor L r and resonant capacitor C r The resonant cavity is formed and located on the secondary side of transformer T, with resonant inductance L. r One end is connected to the corresponding terminal of the secondary winding of transformer T, and the resonant inductor L r The other end is connected to the resonant capacitor C. r One end, resonant capacitor C r The other end serves as an input terminal of the output rectifier; The output rectifier has another input terminal that is the opposite terminal of the secondary winding of transformer T, which is used to rectify the AC voltage output from the secondary winding of transformer into DC voltage. Output capacitor C o It is connected in parallel with the output terminal of the output rectifier to filter out the high-frequency current component in the output rectifier.

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