Single-stage ac-dc converter and control method and control circuit thereof

Abstract

The application discloses a single-stage AC-DC converter and a control method and a control circuit thereof, and belongs to the technical field of electric energy conversion. The single-stage AC-DC converter comprises the following steps: calculating the minimum theoretical current required for completely charging and discharging the junction capacitor of a switching tube within a dead time; selecting a corresponding control mode according to a current working condition, obtaining a soft switching current error amount based on the minimum theoretical current and a compensation resonant current under the current control mode; and adjusting and approximately modulating a reverse operation according to the soft switching current error amount to obtain a given switching frequency and a phase shift angle of the corresponding control mode, and generating a switching driving signal. The application has a complete full-bridge structure, can expand the soft switching range through single phase shift, extended phase shift, double phase shift and triple phase shift control and frequency conversion control, is easy to realize soft switching, and increases the gain accuracy. Meanwhile, due to the full-bridge structure, the voltage stress borne by the switching tube is reduced, and the circuit stability and service life are improved.

Description

Technical Field

[0001] This application relates to the field of power conversion technology, and in particular to a single-stage AC-DC converter and its control method and control circuit. Background Technology

[0002] Microgrids, as a key application scenario for distributed generation, can provide users with a safe, stable, and clean power supply. Furthermore, their flexible installation and dispersed locations reduce energy losses during transportation, improve the efficiency of renewable energy utilization, expand the pathways for renewable energy use, and diversify the power supply methods of the power system. Today's AC / DC microgrids integrate renewable energy and distributed energy storage, primarily consisting of various renewable energy generation units, energy storage devices, and converters connecting these devices. In microgrids, the AC / DC converter is the core component connecting the renewable energy generation units, the bus, the power grid, and the energy storage units; therefore, possessing a highly efficient and stable AC / DC converter is of great significance to microgrids.

[0003] Two-stage AC / DC converters are widely used due to their high reliability and mature control methods. However, this type of topology typically consists of a front-stage AC / DC converter and a rear-stage isolated DC / DC converter, leading to an increase in the number of components, size, and structural complexity, which increases both cost and power density. In contrast, single-stage AC / DC full-bridge LC resonant converters can reduce the power conversion stage, offering potential advantages such as high efficiency, high power density, and low cost. Furthermore, by implementing phase-shift control on the topology based on a quasi-unipolar structure, a wide range of soft switching can be achieved, while also expanding the control degrees of freedom, improving efficiency and dynamic response, and better meeting the core requirements of microgrids and green energy for high efficiency, miniaturization, and high degree of freedom in AC / DC converters.

[0004] However, in traditional power supply systems, AC input must first be converted to DC by an independent rectifier circuit (stage 1) before being fed into the original DC-DC converter (stage 2) for boosting and power transmission. This multi-stage circuitry results in two energy conversion losses, and the additional rectifier modules increase the number of components, expand the overall size, and raise costs. Furthermore, the original resonant single-stage AC / DC converter, due to its half-bridge DC-side structure, has limited phase-shifting capabilities, leading to difficulties in soft-switching and limitations in gain accuracy. Summary of the Invention

[0005] This application aims to provide a single-stage AC-DC converter and its control method and circuit, which has a complete full-bridge structure. The soft-switching range can be expanded through single-phase shift, extended phase shift, double-phase shift, and triple-phase shift control, facilitating soft-switching implementation while increasing gain accuracy. Furthermore, due to the full-bridge structure, the voltage stress on the switching transistors is reduced, improving circuit stability and lifespan.

[0006] To achieve the above objectives, the technical solution of this application is as follows: A control method for a single-stage AC-DC converter, wherein the primary side of the power circuit of the single-stage AC-DC converter adopts a full-bridge rectifier circuit structure and a full-bridge resonant circuit structure; The control method for the single-stage AC-DC converter includes: Calculate the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time. The control mode corresponding to the current operating condition is selected, and the soft-switching current error is obtained based on the minimum theoretical current and the compensation resonant current under the current control mode. Among them, the control modes selected are as follows, depending on the higher the performance requirements of the single-stage AC-DC converter: single phase-shift frequency conversion control mode, extended phase-shift frequency conversion control mode, dual phase-shift frequency conversion control mode and triple phase-shift frequency conversion control mode. Based on the soft-switching current error, an inverse operation is performed using the fundamental frequency approximation modulation to obtain the given switching frequency and phase shift angle for the corresponding control mode, generating a switching drive signal. By dynamically adjusting the switching frequency and phase shift angle, the voltage gain coverage is wide, enabling it to adapt to high-amplitude fluctuations in the input AC voltage, resulting in stronger voltage adaptability and superior anti-fluctuation performance.

[0007] Optionally, calculate the compensation resonant current under the current control mode, including: In single-phase-shift frequency converter control mode, the compensation resonant current is calculated based on the given external phase shift angle and switching frequency under the current control mode, as shown below: Among them, the compensation resonant current represents , F To normalize the switching frequency, ; Z The normalized impedance of the resonant cavity, ; m The ratio of AC to DC voltage. ; For the outward phase angle, n For transformer turns ratio, The resonant frequency, f s For switching frequency, Vdc To output DC voltage, v ac For input AC voltage, The switching angular frequency is used; the single-phase-shift-frequency conversion control mode algorithm has the lowest computational load, and only adjusts and compensates for the resonant current by adjusting the external phase shift angle and switching frequency, which is suitable for normal operating conditions with small load fluctuations and stable input voltage.

[0008] In the extended phase-shift-frequency conversion control mode, the compensation resonant current is calculated based on the given outer phase shift angle, inner phase shift angle, and switching frequency under the current control mode, as shown below: in, This indicates the inner phase shift angle; cross-interference exists between parameters in this control mode. Compared to the single-phase-shift frequency converter control mode, the DC voltage gain coverage is wider, which can adapt to higher amplitude fluctuations in the input AC voltage, resulting in stronger voltage adaptability and better anti-fluctuation performance.

[0009] In the dual phase-shift-frequency conversion control mode, the compensation resonant current is calculated based on the given outer phase shift angle, inner phase shift angle, and switching frequency under the current control mode, as shown below: ; The dual phase-shift-frequency conversion control mode separates the outer and inner phase-shift angles into independent terms, eliminating parameter cross-coupling interference. The AC / DC voltage ratio is multiplied by a set of difference values, and the voltage influence component of the inner phase-shift angle is isolated. Compared with the extended phase-shift-frequency conversion control mode, the DC voltage gain coverage is further broadened, which can adapt to higher amplitude fluctuations in the input AC voltage, further enhancing the voltage adaptability and improving the anti-fluctuation performance.

[0010] In the triple phase-shift-frequency conversion control mode, the compensation resonant current is calculated based on the given switching frequency, outer phase shift angle, primary side inner phase shift angle, and secondary side inner phase shift angle under the current control mode, as shown below: in, This indicates the phase angle shifted inward from the original side; This represents the internal phase shift angle of the secondary side. Independent corrections are made to the internal phase shift angles of the primary and secondary sides. A set of difference values ​​is multiplied into the term multiplied by the AC / DC voltage ratio m, thus separately removing the voltage influence component of the internal phase shift angle of the primary side. This can cope with the dual disturbances of primary-side grid fluctuations and severe secondary-side load fluctuations. Compared to single-phase-shift-frequency converter control mode, extended-phase-shift-frequency converter control mode, and dual-phase-shift-frequency converter control mode, it has the widest DC voltage gain coverage, can adapt to the highest amplitude fluctuations in input AC voltage, has the strongest voltage adaptability, and the best anti-fluctuation performance.

[0011] Optionally, calculate the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time, expressed as follows: in, This represents the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time. This is the junction capacitance value of the switching transistor. Dead time, Input AC voltage v ac The instantaneous absolute value.

[0012] Optionally, based on the soft-switching current error, an inverse operation is performed with the fundamental frequency approximation modulation to obtain the given switching frequency and phase shift angle for the corresponding control mode, generating a switching drive signal, specifically including: The resonant current correction compensation component is obtained by proportional-integral adjustment of the soft-switching current error. The given resonant current q-axis component is obtained by superimposing the resonant current correction compensation component and the minimum theoretical current; The given resonant current q-axis component, input AC voltage, current reference value, and output DC voltage are collected, and the given switching frequency and phase shift angle of the corresponding control mode are obtained through fundamental frequency approximation modulation. The switching drive signal is obtained by pulse width modulation based on the given switching frequency and phase shift angle of the corresponding control mode.

[0013] Optionally, after generating the switch drive signal, the method further includes: adjusting the switching frequency to extend the DC voltage gain, as shown below: in, M Indicates DC voltage gain. Indicates the normalized switching frequency. This represents the quality factor at the resonant frequency.

[0014] A control circuit for a single-stage AC-DC converter, wherein the primary side of the power circuit of the single-stage AC-DC converter adopts a full-bridge rectifier circuit structure and a full-bridge resonant circuit structure; The control circuit of the single-stage AC-DC converter includes: The subtraction module takes the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time and the compensation resonant current under the current control mode as inputs to obtain the soft-switching current error. The proportional-integral (PI) control module uses the input soft-switching current error to perform proportional-integral adjustment to obtain the resonant current correction and compensation component. The addition module takes the resonant current correction compensation component and the minimum theoretical current as input to obtain the given resonant current q-axis component; The fundamental frequency approximation modulation module takes the given resonant current q-axis component, input AC voltage, current reference value, and output DC voltage as input, and obtains the given switching frequency and phase shift angle of the corresponding control mode through fundamental frequency approximation modulation. The compensation resonant current calculation module takes the given switching frequency and phase shift angle of the current control mode as input feedback to obtain the compensation resonant current under the current control mode.

[0015] Optionally, the control circuit of the single-stage AC-DC converter further includes: The pulse width modulation module takes the given switching frequency and phase shift angle corresponding to the control mode as input and modulates them with pulse width to obtain the switching drive signal.

[0016] A single-stage AC-DC converter includes a power circuit and a control circuit, the power circuit and the control circuit are connected, and the control circuit provides a switching drive signal to the power circuit to generate an output DC voltage; The power circuit includes: a full-bridge rectifier module, which receives the input AC voltage and rectifies it to obtain a first DC voltage; the full-bridge rectifier module adopts a full-bridge rectifier circuit structure; A full-bridge resonant module, wherein the full-bridge resonant module performs resonant transformation on a first direct current to obtain a first alternating current; the full-bridge resonant module adopts a full-bridge resonant circuit structure. The secondary-side rectifier module rectifies the first AC current to obtain an output DC voltage. Because the primary-side circuit's full-bridge rectifier module and full-bridge resonant module form a full-bridge circuit structure, the voltage stress on the switching transistors is reduced, circuit stability is improved, and service life is increased.

[0017] Optionally, the control circuit integrates the control method for a single-stage AC-DC converter as described above.

[0018] Optionally, the control circuit may employ the control circuit of a single-stage AC-DC converter as described above.

[0019] This application provides a single-stage AC-DC converter and its control method and control circuit, which has a complete full-bridge structure. The soft-switching range can be expanded through single phase shift, extended phase shift, double phase shift and triple phase shift control, which is easy to implement soft switching while increasing gain accuracy.

[0020] To make the above-mentioned features and advantages of the application more apparent and understandable, specific embodiments are provided below, and detailed descriptions are given in conjunction with the accompanying drawings. Attached Figure Description

[0021] Figure 1This is a structural diagram of a single-stage AC-DC converter.

[0022] Figure 2 This is a structural diagram of control circuit 2 in one embodiment.

[0023] Figure 3 This is a flowchart of the control method for a single-stage AC-DC converter. Detailed Implementation

[0024] To make the objectives and technical solutions of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the described embodiments of this application without creative effort are within the scope of protection of this application.

[0025] This application provides a single-stage AC-DC converter; please refer to [link / reference]. Figure 1 , Figure 1 This is a structural diagram of a single-stage AC-DC converter. The single-stage AC-DC converter includes: a power circuit 1 and a control circuit 2. The power circuit 1 and the control circuit 2 are connected. The control circuit 2 provides a switching drive signal to the power circuit 1 to generate an output DC voltage. V dc .

[0026] As an example, power circuit 1 includes: Full-bridge rectifier module 11, which receives input AC voltage v ac The current is rectified to obtain the first direct current. V dc1 ; Full-bridge resonant module 12, the full-bridge resonant module 12 is connected to the first DC power supply V 1. Perform resonance transformation to obtain the first alternating current. v ac1 ; Secondary rectifier module 13, the secondary rectifier module 13 for the first AC power v 1. Rectify to obtain the output DC voltage. V dc .

[0027] As an example, the full-bridge rectifier module 11 adopts a full-bridge rectifier circuit structure, specifically including: a switch S 1. Switch S 2. Switch S 3. Switch S 4 and capacitors C ac ,switchS The first terminal of 1 is connected to the input AC voltage. v ac One end is connected to the switch. S The second terminal of 1 is connected to the switch. S The second end of 3 is connected to the switch. S The second end of 2 is connected to the switch. S The first end of 1 is connected to the switch. S 2's first end and the switch S 4. Connect the first end to the switch. S The second terminal of 4 is connected to the input AC voltage. v ac The other end and the switch S The first end of 3 is connected to the capacitor. C ac The first end and the switch S The second end of 3 is connected to the capacitor. C ac The second end and the switch S Connect the first terminal of 4. Capacitor. C ac The voltage across the terminals is the first direct current. V dc1 .

[0028] As an example, the full-bridge resonant module 12 adopts a full-bridge resonant circuit structure, specifically including: a switch S 5. Switch S 6. Switch S 7. Switch S 8. Inductance L r ,capacitance C r and transformer T ,switch S 5's first end and switch S The second end of 6 is connected to the switch. S The second terminal of 5 is connected to the capacitor. C ac First end and switch S The second end of 7 is connected to the switch. S The first end of 6 and the switch S The first terminal of 8 and the capacitor C ac The second end is connected to the switch. S The second end of 8 and the switch S The first terminal of 7 is connected to the inductor. L r The first end and the switch S The first terminal of 7 is connected to the inductor. L r The second end and the transformer TThe first end of the primary winding is connected to the transformer. T The second end of the primary winding is connected to the capacitor. C r The first end is connected to the capacitor. C r The second end and the switch S Connect the first terminal of 5. Transformer. T The voltage across the secondary winding is the first alternating current. v ac1 .

[0029] Specifically, inductor L r It is a resonant inductor. Current flows through the inductor. L r The current is the resonant current. I r .

[0030] Specifically, capacitor C r It is a resonant capacitor.

[0031] As an example, the secondary-side rectifier module 13 adopts a full-bridge rectifier circuit structure, specifically including: a switch S 9. Switch S 10 ,switch S 11 and switches S 12 ,switch S The first terminal of 9 is connected to the transformer. T The first end of the secondary winding is connected to the switch. S The second terminal of 9 and the switch S 11 The second end is connected to the switch. S 10 The second end and the switch S The first end of 9 is connected to the switch. S 10 The first end and the switch S 12 The first end is connected to the switch. S 12 The second end and the switch S 11 The first end is connected to the switch. S 11 and switches S 12 The voltage across the terminals is the output DC voltage. V dc .

[0032] Specifically, switch S 1. Switch S 2. SwitchS 3. Switch S 4. Switch S 5. Switch S 6. Switch S 7. Switch S 8. Switch S 9. Switch S 10 ,switch S 11 and switches S 12 It is an N-type metal-oxide-semiconductor field-effect transistor (MOSFET), a switch. S 1. Switch S 2. Switch S 3. Switch S 4. Switch S 5. Switch S 6. Switch S 7. Switch S 8. Switch S 9. Switch S 10 ,switch S 11 and switches S 12 The first terminal is the source terminal of an N-type metal-oxide-semiconductor field-effect transistor, which is used for switching. S 1. Switch S 2. Switch S 3. Switch S 4. Switch S 5. Switch S 6. Switch S 7. Switch S 8. Switch S 9. Switch S 10 ,switch S 11 and switches S 12 The second terminal is the drain of an N-type metal-oxide-semiconductor field-effect transistor.

[0033] Specifically, since the full-bridge rectifier module 11 and the full-bridge resonant module 12 of the primary circuit are full-bridge circuit structures, the voltage stress on the switching transistors is reduced, the circuit stability is improved, and the service life is increased.

[0034] As an example, the switching transistors of the full-bridge rectifier module 11, the full-bridge resonant module 12, and the secondary-side rectifier module 13 are all 50% duty cycle square waves and have an outward phase shift. and the inward phase angle θ .

[0035] As an example, power circuit 1 also includes: an inductorL ac ,inductance L ac The first terminal is connected to the input AC voltage v ac One end is connected to the inductor. L ac The second end and the switch S The first end of 1 is connected.

[0036] Specifically, inductor L ac This is a filter inductor.

[0037] As an example, power circuit 1 also includes: capacitors C dc ,capacitance C dc The first end and the switch S 11 The second end is connected to the capacitor. C dc The second end and the switch S 12 The first end is connected.

[0038] Specifically, capacitor C dc This is a filter capacitor.

[0039] For example, please refer to Figure 2 , Figure 2 This is a structural diagram of control circuit 2 in one embodiment. Control circuit 2 may include: Subtraction module 21, wherein the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time is input. and the compensation resonant current under the current control mode The soft-switching current error is obtained by performing the subtraction. ; Proportional-integral control module 22, input soft-switching current error The resonant current correction and compensation component is obtained by performing proportional-integral adjustment. Addition module 23, inputs the resonant current correction compensation component and the minimum theoretical current. The q-axis components of the given resonant current are obtained by superposition. I rq ; The fundamental frequency approximation modulation module 24 inputs the q-axis component of the given resonant current. I rq Input AC voltage v ac Current reference value I ac_refOutput DC voltage V dc The given switching frequency for the corresponding control mode is obtained by fundamental frequency approximation (FHA) modulation. f s With phase shift angle; The compensation resonant current calculation module 25 receives the given switching frequency of the current control mode as input feedback. f s The compensated resonant current under the current control mode is obtained by using the phase shift angle. ; Pulse width modulation module 26, input with the given switching frequency corresponding to the control mode. f s The switching drive signal is obtained by pulse width modulation of the phase shift angle.

[0040] As an example, the control circuit 2 can integrate a control method for a single-stage AC-DC converter.

[0041] This application provides a control method for a single-stage AC-DC converter. Please refer to [link / reference]. Figure 3 , Figure 3 This is a flowchart of a control method for a single-stage AC-DC converter. The control method for the single-stage AC-DC converter includes: Step 1: Calculate the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time. ; Step 2: Select the control mode corresponding to the current operating conditions, based on the minimum theoretical current. Compensation resonant current under the current control mode Obtain the soft-switching current error Among them, the control modes selected are as follows, depending on the higher the performance requirements of the single-stage AC-DC converter: single phase-shift frequency conversion control mode, extended phase-shift frequency conversion control mode, dual phase-shift frequency conversion control mode and triple phase-shift frequency conversion control mode. Step 3: Based on the soft-switching current error... By performing inverse operations of adjustment and fundamental frequency approximation modulation, the given switching frequency for the corresponding control mode is obtained. f s The phase shift angle is used to generate a switch drive signal.

[0042] In step S1, please refer to Figure 3 In step S1, the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time is calculated. , means as follows: in, This is the junction capacitance value of the switching transistor. Dead time, Input AC voltage v ac The instantaneous absolute value. This is calculated by determining the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time. This enables precise compensation for soft switching.

[0043] In step S2, please refer to Figure 3 In step S2, the control mode corresponding to the current operating condition is selected based on the minimum theoretical current. Compensation resonant current under the current control mode Obtain the soft-switching current error .

[0044] Specifically, in the single-phase-frequency conversion control mode, a hybrid control strategy of single-phase-shift and frequency conversion is adopted to control the switching frequency. f s With the outward shift phase angle Fine-tuning is performed; in the extended phase-shift-frequency conversion control mode, an extended phase-shift and frequency conversion hybrid control strategy is adopted to adjust the switching frequency. f s Outward phase angle and inward phase angle Coupling is fine-tuned; in the dual phase-shift-frequency conversion control mode, a hybrid control strategy of dual phase-shift and frequency conversion is adopted to adjust the switching frequency. f s Outward phase angle and inward phase angle Decoupling allows for fine-tuning; in the triple phase-shift-frequency conversion control mode, a hybrid control strategy of triple phase-shift and frequency conversion is adopted to adjust the switching frequency. f s Outward phase angle Phase angle shifted inward from the original side and secondary side inward shift phase angle Fine-tuning is performed by dynamically adjusting the switching frequency. f s With its wide coverage of phase shift angle and voltage gain, it can adapt to high-amplitude fluctuations in input AC voltage, resulting in stronger voltage adaptability and superior anti-fluctuation performance.

[0045] In single-phase-shift frequency converter control mode, the given external phase shift angle under the current control mode is collected and fed back. and switching frequency f s Calculate the compensation resonant current It is expressed as follows: in, FTo normalize the switching frequency, ; Z The normalized impedance of the resonant cavity, ; m The ratio of AC to DC voltage. ; For the outward phase angle, n For transformer turns ratio, The resonant frequency, f s For switching frequency, V dc To output DC voltage, v ac For input AC voltage, The switching angular frequency is the variable frequency. The single-phase-shift frequency converter control mode algorithm has the lowest computational load, relying solely on external phase shift angles. and switching frequency f s Adjusting the compensation resonant current It is suitable for normal operating conditions with small load fluctuations and stable input voltage.

[0046] In the extended phase-shift-frequency converter control mode, the given external phase shift angle under the current control mode is collected and fed back. Inward phase angle and switching frequency f s Calculate the compensation resonant current It is expressed as follows: .

[0047] in, This represents the inner phase shift angle. The extended phase-shift-frequency conversion control mode algorithm uses... As the main variable for the outer phase shift, the inner phase shift angle Superimposed within the outer phase-shifting term, the inner and outer phase-shifting parameters are coupled and bound together. Changes in the two angles will simultaneously affect the same set of waveform components, through the outer phase-shifting angle. Inward phase angle Switching frequency f s These three factors collectively influence the DC voltage gain M and the resonant current, improving the accuracy of the output switch drive signal; however, there is cross-interference among these parameters. Compared to the single-phase-shift-frequency converter control mode, the DC voltage gain M has a wider coverage range and can adapt to the input AC voltage. v ac It has a higher amplitude of fluctuation, stronger voltage adaptability, and better anti-fluctuation performance.

[0048] In the dual phase-shift-frequency converter control mode, the given external phase shift angle of the current control mode is collected and fed back. Inward phase angle and switching frequency f s Calculate the compensation resonant current It is expressed as follows: The dual phase-shift-frequency conversion control mode will shift the external phase angle... Inward phase angle Decompose the terms into independent sub-items, eliminate parameter cross-coupling interference, multiply the AC / DC voltage ratio m by a set of difference values, and separately remove the inner phase shift angle. The voltage-affected component; compared to the extended phase-shift frequency converter control mode, the DC voltage gain M has a wider coverage range, which can adapt to the input AC voltage. v ac With higher amplitude fluctuations, voltage adaptability is further enhanced, and anti-fluctuation performance is even better.

[0049] In the triple phase-shift-frequency conversion control mode, the given switching frequency of the current control mode is collected and fed back. f s Outward phase angle Phase angle shifted inward from the original side and the secondary side inward shift phase angle Calculate the compensation resonant current It is expressed as follows: The phase shift angle within the triple phase-shift-frequency conversion control mode Decomposed into the phase angle of the primary side shifted inward. and the secondary side inward shift phase angle The phase shift angles of the primary and secondary sides are independently corrected. The AC / DC voltage ratio m is multiplied by a set of difference values ​​to isolate the phase shift angle of the primary side. The voltage influence component can cope with the dual disturbances of primary grid fluctuations and secondary load severity fluctuations; compared with single phase-shift-frequency conversion control mode, extended phase-shift-frequency conversion control mode and dual phase-shift-frequency conversion control mode, the DC voltage gain M has the widest coverage and can adapt to input AC voltage. v ac It exhibits the strongest voltage adaptability and the best anti-fluctuation performance under the highest fluctuation amplitude.

[0050] In step S3, please refer to Figure 3 In step S3, based on the soft-switching current error... By performing inverse operations of adjustment and fundamental frequency approximation modulation, the given switching frequency for the corresponding control mode is obtained. f s The phase shift angle is used to generate a switch drive signal.

[0051] As an example, step S3 specifically includes: For soft-switching current error The resonant current correction and compensation component is obtained by performing proportional-integral adjustment. The resonant current correction and compensation component and the minimum theoretical current The q-axis components of the given resonant current are obtained by superposition. I rq ; Acquire the q-axis component of the given resonant current I rq Input AC voltage v ac Current reference value I ac_ref Output DC voltage V dc The given switching frequency for the corresponding control mode is obtained through fundamental frequency approximation modulation. f s With phase shift angle; Based on the given switching frequency of the corresponding control mode f s The phase shift angle is pulse-width modulated to obtain the switch drive signal.

[0052] Furthermore, the switch drive signal drives and controls the switching transistors of the power circuit, transmitting the given switching frequency in digital form. f s The phase shift angle is converted into a hardware-recognizable switching drive timing, thereby enabling the adjustment of the switching frequency and phase shift angle of power circuit 1 under the corresponding control mode.

[0053] Furthermore, after generating the switch drive signal, the DC voltage gain M is calculated using the fundamental frequency approximation method by adjusting the switching frequency, as follows: The primary side square wave voltage of the transformer in the full-bridge resonant module of the single-stage AC-DC converter The amplitude is Transformer primary side square wave voltage The effective value of the fundamental component is expressed as follows: .

[0054] The resonant cavity is composed of an inductor ,capacitance Composition, resonant angular frequency It is expressed as follows: .

[0055] Transformer turns ratio Resonant current I r Approximately sine.

[0056] The secondary rectifier module of the single-stage AC-DC converter operates in the same manner as the rectifier bridge, with the filter capacitor... Large enough, the effective value of the fundamental component of the transformer secondary voltage The effective value of the fundamental component of the transformer secondary current With output DC voltage Output DC current The relationship is represented as follows: .

[0057] Furthermore, the equivalent AC resistance of the transformer secondary side It is expressed as follows: .

[0058] in, This indicates the load resistance.

[0059] Furthermore, the equivalent AC resistance of the transformer secondary side The equivalent resistance of the transformer primary side reflected to the transformer primary side It is expressed as follows: .

[0060] Furthermore, the resonant cavity of the full-bridge resonant module is obtained from the primary-side square wave voltage of the transformer. Power supply, inductor ,capacitance Equivalent resistance of transformer primary side The fundamental effective value of the primary voltage of a series transformer Right now The voltage across the terminals satisfies: .

[0061] RMS value of the fundamental component of the primary voltage of the transformer The effective value of the fundamental component of the square wave voltage on the primary side of the transformer The pressure distribution relationship is expressed as follows: .

[0062] Substituting into the above formula, we get: .

[0063] After eliminating the coefficients, the DC voltage gain M is expressed as follows: .

[0064] Furthermore, a normalized switching frequency is introduced. and resonant frequency Quality factor at the location , means as follows: So: Substituting into the formula for DC voltage gain M and simplifying, we get: .

[0065] In summary, it can be concluded that when the switching frequency... At the resonant frequency Right now , DC voltage gain A single-stage AC-DC converter achieves maximum gain, and with a good quality factor That is, the load is irrelevant. The resonant cavity impedance is zero, and there is no voltage drop loss.

[0066] When switching frequency Greater than the resonant frequency Right now , DC voltage gain With switching frequency The increase is monotonically decreasing. This is because of the inductance. The inductive reactance increases, drawing away more voltage.

[0067] When switching frequency Less than the resonant frequency Right now , Similarly, this refers to DC voltage gain. With switching frequency The capacitance decreases and drops monotonically. As capacitive reactance increases, partial voltage also increases.

[0068] The following will continue to combine Figure 1 This paper introduces the working principles and processes of four phase-shifting frequency conversion control modes.

[0069] In the single-phase-frequency conversion control mode, only the external phase shift angle and switching frequency of power circuit 1 are adjusted.

[0070] exist At that moment, the single-stage AC-DC converter is in the first switching mode, with switches S5 and S8 conducting at zero voltage, and switches S9 and S2 conducting at zero voltage. 12 Conduction. First DC current. V dc1 The positive current is applied to the LC resonant cavity and transformer via switching transistors S5 and S8. T Primary side, transformer T The secondary side is connected to switch S9 and switch S. 12 Output energy to the load. Resonant current. For the positive portion of a sine wave, the capacitance... It charges and discharges during the resonance process.

[0071] exist At any given time, the single-stage AC-DC converter is in the second switching mode, with switches S5 and S8 remaining on, and the secondary-side switching switch S... 10 Switch S 11 Simultaneously, the circuit is turned on. The secondary side of the transformer is short-circuited, the voltage of the primary winding is clamped to zero, and the entire input voltage is applied to the inductor. ,capacitance On the series branch. Resonant current. Continued forward flow, affecting the capacitor Fast charging stores energy for subsequent dead-zone commutation. There is no power output during this phase; the load is supplied by capacitors. powered by.

[0072] exist At that moment, the single-stage AC-DC converter is in the third switching mode, with switches S5 and S8 turned off, all primary-side switches entering the dead zone, and the transformer... T The secondary side still maintains the switching transistor S 10 Switch S 11 Simultaneous conduction. Resonant current. No sudden changes are allowed. The circuit is extracted from switching transistors S5 and S8, and a capacitor is used... The stored energy discharges the junction capacitance of switches S6 and S7, reducing their drain-source voltage to zero. The body diodes of switches S6 and S7 then conduct, clamping their voltage to zero, thus creating conditions for zero-voltage turn-on after the dead time ends.

[0073] exist At that moment, the single-stage AC-DC converter is in the fourth switching mode, with switches S6 and S7 turned on at zero voltage, and switch S... 10 Switch S 11 Synchronous rectification is performed upon activation. First DC current. V dc1 Reverse application to the resonant cavity and transformer T Above, the power is transmitted through the secondary-side switch S. 10 Switch S 11 Output to the load. Resonant current. Reverse flow, capacitor Reverse charging and discharging.

[0074] exist At that moment, the single-stage AC-DC converter is in the fifth switching mode, with switches S6 and S7 remaining on, and the transformer... TThe secondary side switches switching transistors S9 and S2 again. 11 .transformer T The primary side is clamped to zero again, and the entire reverse input voltage is applied to the inductor. ,capacitance Above, capacitor Reverse charging stores energy for the next dead zone.

[0075] exist At that moment, the single-stage AC-DC converter is in the sixth switching mode, with switches S6 and S7 turned off, entering the dead zone, and the transformer... T Secondary side holding switch S9, switch S 11 On. Reverse resonant current. With the help of capacitor Energy discharges the junction capacitance of switches S5 and S8, causing their body diodes to conduct and clamp to zero. After the dead time ends, switches S5 and S8 can be turned on with zero voltage, achieving soft switching.

[0076] In the extended phase-shift-frequency conversion control mode, the outer phase shift angle, inner phase shift angle, and switching frequency of power circuit 1 are adjusted.

[0077] exist At that moment, the single-stage AC-DC converter is in the first switching mode, with primary-side switches S5 and S8 conducting at zero voltage, and secondary-side switches S9 and S1... 12 Conduction. First DC current. V dc1 The positive current is applied to the LC resonant cavity and transformer via switching transistors S5 and S8. T Primary side, transformer T The secondary side is connected to switch S9 and switch S. 12 Output energy to the load. Resonant current. It is a positive sine wave, and the capacitor... Charge and discharge with resonance.

[0078] exist At any given time, the single-stage AC-DC converter is in the second switching mode, with primary-side switches S5 and S8 remaining on, and secondary-side switches S9 and S1 remaining off. 12 Turn on the switch S 10 Switch S 11 The voltage polarity of the transformer secondary side reverses, the resonant cavity is short-circuited, and the resonant current... It is rapidly declining and changing negative. Accelerate charging.

[0079] exist At that moment, the single-stage AC-DC converter is in the third switching mode, with the primary side switch S8 turned off and entering the dead zone; the secondary side holds the switch S8. 10 Switch S 11 On. Resonant current. Charge is extracted from the junction capacitance of switch S8 and injected into the junction capacitance of switch S7, causing the body diode of switch S7 to conduct and clamp to zero. At the end of the dead time, switch S7 has the zero-voltage turn-on condition.

[0080] exist At any given time, the single-stage AC-DC converter is in the fourth switching mode. Primary-side switch S5 remains on, and switch S7 is turned on at zero voltage, resulting in simultaneous conduction of switches S5 and S7, short-circuiting both. Switches S6 and S8 are off. The secondary side remains in the same state, with switch S7... 10 Switch S 11 On. Resonant current. The primary circulating current of the transformer flows through the resonant cavity and continues freewheeling without passing through the power supply or the capacitor. Slow discharge or charge.

[0081] exist At that moment, the single-stage AC-DC converter is in the fifth switching mode, with primary-side switches S5 and S7 continuing to conduct, and secondary-side switch S7 turned off. 10 Switch S 11 Turn on switch S9 and switch S 12 The transformer secondary voltage reverses again, forcing the resonant current to reverse. The capacitance decreases rapidly or even crosses zero. The charging and discharging directions change accordingly.

[0082] exist At that moment, the single-stage AC-DC converter is in the sixth switching mode, with the primary side switch S5 turned off and entering the dead zone; the secondary side maintains the operation of switches S9 and S1. 12 On. Resonant current. This charges the junction capacitance of switch S5 and discharges the junction capacitance of switch S6, causing the body diode of switch S6 to conduct and clamp to zero. After the dead time ends, switch S6 can be turned on with zero voltage.

[0083] exist At any given time, the single-stage AC-DC converter is in the seventh switching mode, with primary-side switch S6 turned on at zero voltage and switch S7 remaining on, resulting in switches S6 and S7 being on; secondary-side switches S9 and S1 are also on. 12 Conduction. First DC current. V dc1 The circuit is reverse-biased and applied to the LC resonant cavity and the primary winding of the transformer via switches S7 and S6, while the secondary winding is connected to switches S9 and S6. 12Output energy to the load. Resonant current. It is a negative sine wave, and the capacitor Reverse charging and discharging.

[0084] exist At any given time, the single-stage AC-DC converter is in the eighth switching mode, with primary-side switches S6 and S7 remaining on, and secondary-side switches S9 and S1 remaining off. 12 Turn on the switch S 10 Switch S 11 The secondary voltage flips, the resonant cavity is short-circuited, and the resonant current... Rapidly changing in the positive direction, capacitance Accelerated charging and discharging.

[0085] exist At that moment, the single-stage AC-DC converter is in the ninth switching mode, with the primary side switch S7 turned off and entering the dead zone; the secondary side holds the switch S7. 10 Switch S 11 On. Resonant current. The junction capacitance of switch S7 is charged, and the junction capacitance of switch S8 is discharged, causing the body diode of switch S8 to conduct and clamp to zero. After the dead time, switch S8 has the condition for zero-voltage turn-on.

[0086] exist At any given time, the single-stage AC-DC converter is in the tenth switching mode. Primary-side switch S6 remains on, and switch S8 is turned on at zero voltage, resulting in simultaneous conduction of switches S6 and S8, short-circuiting both. Switches S5 and S7 are off. The secondary side remains in the same state, with switch S6... 10 Switch S 11 On. Resonant current. Through the primary winding of the transformer, the resonant cavity circulates and continues to flow. Slow reverse charging.

[0087] exist At that moment, the single-stage AC-DC converter is in the eleventh switching mode, with primary-side switches S6 and S8 continuing to conduct, and secondary-side switch S1 turned off. 10 Switch S 11 Turn on switch S9 and switch S 12 The secondary voltage flips again, forcing the resonant current to... From negative to positive or rising rapidly, capacitance The charging and discharging directions change.

[0088] exist At that moment, the single-stage AC-DC converter is in the twelfth switching mode, with the primary side switch S6 turned off and entering the dead zone; the secondary side maintains the operation of switches S9 and S1. 12On. Resonant current. The junction capacitance of switch S8 is charged, and the junction capacitance of switch S5 is discharged, causing the body diode of switch S5 to conduct and clamp to zero. After the dead time, switch S5 turns on with zero voltage, returning to the first switching mode, and the cycle repeats.

[0089] In the dual phase-shift-frequency conversion control mode, the outer phase-shift angle, inner phase-shift angle, and switching frequency of the power circuit 1 are adjusted.

[0090] exist At that moment, the single-stage AC-DC converter is in the first switching mode, with primary-side switches S5 and S8 conducting at zero voltage, and secondary-side switches S9 and S1... 12 The circuit is on. The input voltage is applied forward through switches S5 and S8 to the LC resonant cavity and the primary winding of the transformer, while the secondary winding is applied through switches S9 and S1. 12 Output energy to the load. Resonant current. It is a positive sine wave, and the capacitor... Charge and discharge with resonance.

[0091] exist At any given time, the single-stage AC-DC converter is in the second switching mode, with primary-side switches S5 and S8 remaining on. Secondary-side switch S8 is off. 12 Turn on the switch S 11 Advanced forearm commutation forms switching transistor S9 and switching transistor S... 11 Simultaneously conducting, both upper transistors are short-circuited to zero level, and the switching transistor S... 10 Switch S 12 Turn off. The secondary side of the transformer is short-circuited and clamped to zero. The resonant cavity is subjected to a positive voltage, and the resonant current... Continue to rise positively, capacitance Charging and energy storage prepare for subsequent dead-zone switching.

[0092] exist At that moment, the single-stage AC-DC converter is in the third switching mode, with primary-side switch S8 turned off, entering the dead zone. Secondary-side switches S9 and S1 remain open. 11 On. Resonant current. The current freewheels, drawing charge from the junction capacitance of switch S8 and injecting it into the junction capacitance of switch S7, clamping the body diode of switch S7 to zero. At the end of the dead time, switch S7 meets the zero-voltage turn-on condition.

[0093] exist At any given time, the single-stage AC-DC converter is in the fourth switching mode. Primary-side switch S5 remains on, and switch S7 is turned on at zero voltage, forming a zero-level loop between switches S5 and S7. Switches S6 and S8 are off. The secondary side remains on with switches S9 and S8.11 Conduction. Both sides of the transformer are short-circuited at the top, the voltage across the resonant cavity is close to zero, and the resonant current is... Through the resonant cavity, the circulating current on the primary side of the transformer continues to flow, slowly attenuating, with almost no power transmission.

[0094] exist At any given time, the single-stage AC-DC converter is in the fifth switching mode, with primary-side switches S5 and S7 remaining on. Secondary-side switch S9 is off, and switch S1 is on. 10 Advanced arm commutation, switching to switching transistor S 10 Switch S 11 The transformer is turned on. The secondary voltage flips to negative, and the resonant cavity experiences a reverse voltage, forcing the resonant current to conduct. The capacitance drops rapidly to zero and begins to reverse. Discharge acceleration establishes the initial current for zero-voltage turn-on of the advanced arm and power transfer during the negative half-cycle.

[0095] exist At that moment, the single-stage AC-DC converter is in the sixth switching mode, with the primary-side switch S5 turned off and entering the dead zone. The secondary-side switch S5 remains open. 10 Switch S 11 On. Resonant current. This charges the junction capacitance of switch S5 and discharges the junction capacitance of switch S6, causing the body diode of switch S6 to conduct and clamp to zero. After the dead time ends, switch S6 can be turned on with zero voltage.

[0096] exist At any given time, the single-stage AC-DC converter is in the seventh switching mode, with primary-side switch S6 turned on at zero voltage and switch S7 remaining on, resulting in switches S6 and S7 being on. Secondary-side switch S... 10 Switch S 11 Conduction. First DC current. V dc1 The circuit is reverse-biased and applied to the LC resonant cavity and the primary winding of the transformer via switches S7 and S6, while the secondary winding is connected to the secondary winding via switch S7. 10 Switch S 11 Output energy to the load. Resonant current. It is a negative sine wave, and the capacitor Reverse charging and discharging.

[0097] exist At any given time, the single-stage AC-DC converter is in the eighth switching mode, with primary-side switches S6 and S7 remaining on. Secondary-side switch S7 is off. 11 Turn on the switch S 12 Advanced forearm commutation forms the switching transistor S 10 Switch S 12Simultaneously conducting, both lower transistors are short-circuited to zero level, switching transistors S9 and S2 are at their respective voltage levels. 11 Turn off. The secondary side of the transformer is short-circuited and clamped to zero again, the resonant cavity is subjected to reverse voltage, and the resonant current... The negative value continues to rise, and the capacitance... Reverse charging energy storage.

[0098] exist At that moment, the single-stage AC-DC converter is in the ninth switching mode, with the primary-side switch S7 turned off and entering the dead zone. The secondary-side switch S7 remains open. 10 Switch S 12 On. Resonant current. The charge is extracted from the junction capacitance of switch S7 and injected into the junction capacitance of switch S8, causing the body diode of switch S8 to conduct and clamp to zero. Switch S8 obtains the zero-voltage turn-on condition.

[0099] exist At any given time, the single-stage AC-DC converter is in the tenth switching mode. Primary-side switch S6 remains on, and switch S8 is turned on at zero voltage, forming a zero-level loop between switches S6 and S8. Switches S5 and S7 are off. The secondary side remains on with switch S6... 10 Switch S 12 Conduction. Both sides of the transformer are short-circuited at the bottom tube, the resonant cavity voltage is close to zero, and the resonant current is... The resonant cavity continues to flow through the primary side of the transformer, and the current decays slowly.

[0100] exist At any given time, the single-stage AC-DC converter is in the eleventh switching mode, with primary-side switches S6 and S8 remaining on. Secondary-side switch S8 is off. 10 Turn on switch S9, initiate advanced arm commutation, and switch to switch S9 and switch S... 12 The circuit is turned on. The secondary voltage of the transformer flips to positive, and the resonant cavity is subjected to a positive voltage, forcing the resonant current to conduct. From negative to positive crossing of zero, capacitor Accelerated charging establishes the initial current for zero-voltage turn-on of the leading arm and power transfer during the positive half-cycle.

[0101] exist At this time, the single-stage AC-DC converter is in the twelfth switching mode, with primary-side switch S8 turned off, entering the dead zone, and all primary-side switches turned off. Secondary-side switches S9 and S1 remain open. 12 On. Resonant current. The junction capacitance of switch S8 is charged, and the junction capacitance of switch S5 is discharged, causing the body diode of switch S5 to conduct and clamp to zero. After the dead time, switch S5 turns on with zero voltage, returning to the first switching mode, and the cycle repeats.

[0102] In the triple phase-shift-frequency conversion control mode, the external phase-shift angle, the internal phase-shift angle of the primary side, the internal phase-shift angle of the secondary side, and the switching frequency of the power circuit 1 are adjusted.

[0103] exist At that moment, the single-stage AC-DC converter is in the first switching mode, with primary-side switch S5 turned on at zero voltage, and switches S6, S7, and S8 all undriven. This is due to the resonant current at the end of the previous cycle. For the positive side, the current path passes through the resonant cavity, the transformer, and then to the body diode of the primary-side switching transistor. The secondary-side switching transistors S9 and S2 are also connected. 12 Turn-on. During this stage, the drain-source voltage of switch S8 is clamped to zero by its body diode, preparing for the upcoming turn-on.

[0104] exist At that moment, the single-stage AC-DC converter is in the second switching mode, with primary-side switch S8 turned on at zero voltage, forming a forward path with switch S5. Secondary-side switches S9 and S2... 12 The circuit is on. The input voltage is applied forward through switches S5 and S8 to the LC resonant cavity and the primary winding of the transformer, while energy is output from the secondary winding. Resonant current... Sinusoidal change, capacitance Charging and discharging.

[0105] exist At any given time, the single-stage AC-DC converter is in the third switching mode, with primary-side switches S5 and S8 remaining on. Secondary-side switch S8 is off. 12 Turn on the switch S 11 Advanced forearm commutation forms switching transistor S9 and switching transistor S... 11 Simultaneous conduction, short circuit between the two upper transistors, switching transistor S... 10 Switch S 11 Turn off. The secondary side of the transformer is short-circuited, the resonant cavity is subjected to a positive voltage, and the resonant current... Continue to rise, capacitance Energy storage.

[0106] exist At that moment, the single-stage AC-DC converter is in the fourth switching mode, with primary-side switch S8 turned off, entering the dead zone. Secondary-side switches S9 and S1 remain open. 11 On. Resonant current. The junction capacitance of switching transistors S8 and S7 is charged and discharged, and the switching transistor S... 7的 The body diode is clamped to zero.

[0107] exist At any given time, the single-stage AC-DC converter is in the fifth switching mode. Primary-side switch S5 remains on, and switch S7 is turned on at zero voltage, resulting in simultaneous conduction of switches S5 and S7. Secondary-side switches S9 and S7 remain on. 11 Conduction. Both sides are short-circuited in the upper tube, the resonant cavity voltage is close to zero, and the resonant current is... Circulating flow attenuation.

[0108] exist At any given time, the single-stage AC-DC converter is in the sixth switching mode, with primary-side switches S5 and S7 remaining on. Secondary-side switch S9 is off, and switch S1 is on. 10 Switching to the switching transistor S 10 Switch S 11 Conduction begins. Secondary voltage reverses direction, resonant current... Rapid descent across zero reversal, capacitor Discharge.

[0109] exist At that moment, the single-stage AC-DC converter is in the seventh switching mode, with the primary-side switch S5 turned off and entering the dead zone. The secondary-side switch S5 remains open. 10 Switch S 11 On. Resonant current. The junction capacitance of switching transistors S5 and S6 is charged and discharged, and the body diode of switching transistor S6 is clamped to zero.

[0110] exist At any given time, the single-stage AC-DC converter is in the eighth switching mode, with primary-side switch S6 turned on at zero voltage and switch S7 remaining on, resulting in switches S6 and S7 being on. Secondary-side switch S... 10 Switch S 11 Conduction. Energy is transferred in the reverse direction, resonant current. Negative sine wave, capacitance Reverse charging and discharging.

[0111] exist At any given time, the single-stage AC-DC converter is in the ninth switching mode, with primary-side switches S6 and S7 remaining on. Secondary-side switch S7 is off. 11 Turn on the switch S 12 To form the switching transistor S 10 Switch S 12 Simultaneous conduction leads to a short circuit between the two lower transistors. With the secondary side shorted, the resonant cavity experiences a reverse voltage, and the resonant current... Negative increase, capacitance Reverse energy storage.

[0112] exist At that moment, the single-stage AC-DC converter is in the tenth switching mode, with the primary-side switch S7 turned off and entering the dead zone. The secondary-side switch S7 remains open. 10 Switch S 12 On. Resonant current. The junction capacitance of switching transistors S7 and S8 is charged and discharged, and the body diode of switching transistor S8 is clamped to zero.

[0113] exist At any given time, the single-stage AC-DC converter is in the eleventh switching mode. Primary-side switch S6 remains on, while switch S8 is turned on at zero voltage, resulting in both switches S6 and S8 being on simultaneously. Secondary-side switch S6 remains on. 10 Switch S 12 Conduction. Both sides are short-circuited in the lower tube, resonant current. Circulation attenuation.

[0114] exist At any given time, the single-stage AC-DC converter is in the twelfth switching mode, with primary-side switches S6 and S8 remaining on. Secondary-side switch S8 is off. 10 Turn on switch S9, switch to switch S9, switch S 12 Conduction begins. Secondary voltage reverses direction, resonant current... From negative to positive crossing of zero, capacitor Charge.

[0115] exist At that moment, the single-stage AC-DC converter is in the thirteenth switching mode, with primary-side switch S8 turned off, entering the dead zone, and all primary-side switches turned off. Secondary-side switches S9 and S1 remain open. 12 On. Resonant current. The junction capacitances of switching transistors S8 and S5 are charged and discharged, and the body diode of switching transistor S5 is clamped to zero.

[0116] exist At that moment, the single-stage AC-DC converter is in the fourteenth switching mode, with primary-side switch S5 turned on at zero voltage, and switches S6, S7, and S8 undriven. Forward resonant current. Through the resonant cavity and the freewheeling current of the diode on the primary side of the transformer, the drain-source voltage of switch S8 is clamped to zero. The secondary side maintains the voltages of switches S9 and S... 12 Conduction.

[0117] exist At that moment, the single-stage AC-DC converter is in the fifteenth switching mode. The primary-side switch S8 is turned on with zero voltage under the conduction of the body diode, forming a forward path with the switch S5. At this time, it can be considered that the forward energy transfer has started.

[0118] exist At that moment, the single-stage AC-DC converter is in the sixteenth switching mode, with primary-side switches S5 and S8 turned on, and secondary-side switches S9 and S1... 12 Conduction continues until the next secondary-side commutation, completing a full cycle.

[0119] The single-stage AC-DC converter and its control method and circuit provided in this application have a complete full-bridge structure. The soft-switching range can be expanded through single-phase shift, extended phase shift, double-phase shift, and triple-phase shift combined with frequency conversion control, facilitating soft-switching implementation while increasing gain accuracy. Furthermore, due to the full-bridge structure, the voltage stress on the switching transistors is reduced, improving circuit stability and lifespan.

[0120] Although this application has been disclosed above with reference to embodiments, it is not intended to limit this application. Anyone skilled in the art may make some modifications and refinements without departing from the spirit and scope of this application. Therefore, the scope of protection of this application shall be determined by the appended claims.

Claims

1. A control method for a single-stage AC-DC converter, characterized in that, The primary side of the power circuit of the single-stage AC-DC converter adopts a full-bridge rectifier circuit structure and a full-bridge resonant circuit structure. The control method for the single-stage AC-DC converter includes: Calculate the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time. The control mode corresponding to the current operating condition is selected, and the soft-switching current error is obtained based on the minimum theoretical current and the compensation resonant current under the current control mode. Among them, the control modes selected are as follows, depending on the higher the performance requirements of the single-stage AC-DC converter: single phase-shift frequency conversion control mode, extended phase-shift frequency conversion control mode, dual phase-shift frequency conversion control mode and triple phase-shift frequency conversion control mode. Based on the soft-switching current error, the inverse operation of the fundamental frequency approximation modulation is performed to obtain the given switching frequency and phase shift angle of the corresponding control mode, and a switching drive signal is generated.

2. The control method for a single-stage AC-DC converter as described in claim 1, characterized in that, Calculate the compensation resonant current under the current control mode, including: In single-phase-shift frequency converter control mode, the compensation resonant current is calculated based on the given external phase shift angle and switching frequency under the current control mode, as shown below: Among them, the compensation resonant current represents , F To normalize the switching frequency, ; Z The normalized impedance of the resonant cavity, ; m The ratio of AC to DC voltage. ; For the outward phase angle, n For transformer turns ratio, The resonant frequency, f s For switching frequency, V dc To output DC voltage, v ac For input AC voltage, The switching angular frequency; In the extended phase-shift-frequency conversion control mode, the compensation resonant current is calculated based on the given outer phase shift angle, inner phase shift angle, and switching frequency under the current control mode, as shown below: in, Indicates the inward phase shift angle; In the dual phase-shift-frequency conversion control mode, the compensation resonant current is calculated based on the given outer phase shift angle, inner phase shift angle, and switching frequency under the current control mode, as shown below: ； In the triple phase-shift-frequency conversion control mode, the compensation resonant current is calculated based on the given switching frequency, outer phase shift angle, primary side inner phase shift angle, and secondary side inner phase shift angle under the current control mode, as shown below: in, This indicates the phase angle shifted inward from the original side; This indicates the phase angle of the secondary side shift.

3. The control method for a single-stage AC-DC converter as described in claim 2, characterized in that, The minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time is calculated as follows: in, This represents the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time. This is the junction capacitance value of the switching transistor. Dead time, Input AC voltage v ac The instantaneous absolute value.

4. The control method for a single-stage AC-DC converter as described in claim 3, characterized in that, Based on the soft-switching current error, an inverse operation is performed with the fundamental frequency approximation modulation to obtain the given switching frequency and phase shift angle for the corresponding control mode, generating a switching drive signal, specifically including: The resonant current correction compensation component is obtained by proportional-integral adjustment of the soft-switching current error. The given resonant current q-axis component is obtained by superimposing the resonant current correction compensation component and the minimum theoretical current; The given resonant current q-axis component, input AC voltage, current reference value, and output DC voltage are collected, and the given switching frequency and phase shift angle of the corresponding control mode are obtained through fundamental frequency approximation modulation. The switching drive signal is obtained by pulse width modulation based on the given switching frequency and phase shift angle of the corresponding control mode.

5. The control method for a single-stage AC-DC converter as described in claim 3, characterized in that, After generating the switch drive signal, the process also includes: adjusting the switching frequency to extend the DC voltage gain, as shown below: in, M Indicates DC voltage gain. Indicates the normalized switching frequency. This represents the quality factor at the resonant frequency.

6. A control circuit for a single-stage AC-DC converter, characterized in that, The primary side of the power circuit of the single-stage AC-DC converter adopts a full-bridge rectifier circuit structure and a full-bridge resonant circuit structure. The control circuit of the single-stage AC-DC converter includes: The subtraction module takes the minimum theoretical current required to fully charge and discharge the junction capacitance of the switching transistor within a dead time and the compensation resonant current under the current control mode as inputs to obtain the soft-switching current error. The proportional-integral (PI) control module uses the input soft-switching current error to perform proportional-integral adjustment to obtain the resonant current correction and compensation component. The addition module takes the resonant current correction compensation component and the minimum theoretical current as input to obtain the given resonant current q-axis component; The fundamental frequency approximation modulation module takes the given resonant current q-axis component, input AC voltage, current reference value, and output DC voltage as input, and obtains the given switching frequency and phase shift angle of the corresponding control mode through fundamental frequency approximation modulation. The compensation resonant current calculation module takes the given switching frequency and phase shift angle of the current control mode as input feedback to obtain the compensation resonant current under the current control mode.

7. The control circuit of the single-stage AC-DC converter as described in claim 6, characterized in that, Also includes: The pulse width modulation module takes the given switching frequency and phase shift angle corresponding to the control mode as input and modulates them with pulse width to obtain the switching drive signal.

8. A single-stage AC-DC converter, characterized in that, It includes a power circuit and a control circuit. The power circuit and the control circuit are connected. The control circuit provides a switching drive signal to the power circuit to generate an output DC voltage. The power circuit includes: a full-bridge rectifier module, which receives the input AC voltage and rectifies it to obtain a first DC voltage; the full-bridge rectifier module adopts a full-bridge rectifier circuit structure; A full-bridge resonant module, wherein the full-bridge resonant module performs resonant transformation on a first direct current to obtain a first alternating current; the full-bridge resonant module adopts a full-bridge resonant circuit structure. The secondary-side rectifier module rectifies the first AC power to obtain an output DC voltage.

9. The single-stage AC-DC converter as described in claim 8, characterized in that, The control circuit integrates the control method for a single-stage AC-DC converter as described in any one of claims 1-5.

10. The single-stage AC-DC converter as described in claim 8, characterized in that, The control circuit adopts the control circuit of the single-stage AC-DC converter as described in any one of claims 6-7.

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