Bridgeless single-stage AC-DC resonant converter

Abstract

The invention discloses a bridgeless single-stage AC-DC resonant converter. The bridgeless single-stage AC-DC resonant converter comprises a linear-resonant circuit and an output rectifying circuit, the positive input end of the linear-resonant circuit is connected with one end of the output side of the low-pass filter, and the negative input end of the linear-resonant circuit is connected with the other end of the output side of the low-pass filter; one end of the output side of the linear-resonant circuit is connected with one input end of the output rectifying circuit, and the other output end of the linear-resonant circuit is connected with the other end of the output rectifying circuit; one output end of the output rectifying circuit is connected with the positive end of the output load battery; the other end of the output rectification circuit is connected with the negative end of the output load battery. According to the single-stage AC-DC resonant converter, the equivalent AC input voltage amplitude of the AC-DC converter is effectively changed, the topological voltage gain range is further remarkably widened, and the conversion efficiency of the single-stage AC-DC resonant converter is improved.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, specifically a bridgeless single-stage AC-DC resonant converter. Background Technology

[0002] The increasing number of traditional gasoline-powered vehicles has exacerbated the fossil fuel crisis and environmental pollution. Electric vehicles, with their "zero emissions" advantage, have gradually become a focus of social attention. On-board chargers, as a crucial component of electric vehicles, directly determine the efficiency and safety of vehicles at AC charging stations, thus attracting widespread attention. The core requirements of on-board chargers are: providing the necessary high-voltage DC power to the battery, achieving power factor correction, and controlling and protecting the charging process. Based on meeting these core requirements, current research on on-board chargers mainly focuses on improving efficiency, reducing costs, and minimizing size.

[0003] Traditional on-board chargers typically employ a two-stage architecture, consisting of a front-stage AC-DC converter and a rear-stage DC-DC converter. The front-stage AC-DC converter features power factor correction (PFC), while the rear-stage DC-DC converter converts the DC output from the front stage into voltage and current suitable for charging the battery. Its AC input and DC output can be decoupled, resulting in good power factor correction. However, because it contains two independent power stages, the electrical energy needs to be processed twice. Both the front and rear stages require independent active and passive power devices, and a high-voltage, high-capacity electrolytic capacitor needs to be connected in parallel between the front and rear stages. This makes the two-stage topology costly, bulky, and has low power density, making it difficult to meet future commercialization needs.

[0004] AC-DC PFC converters based on a single-stage architecture can achieve power control through a single isolation conversion. They offer advantages such as low cost, high efficiency, and high power density, making them a viable solution. LLC resonant converters, with their high efficiency and simple control, are used in medium-to-high power AC-DC conversion applications. However, traditional LLC structures have a limited output voltage gain range, making it difficult to achieve high conversion efficiency while simultaneously meeting the wide voltage gain range and high power factor requirements of automotive batteries. If voltage gain is the primary design parameter, the overall efficiency performance of the converter under wide voltage variations will be reduced. Therefore, continuous improvement of current topologies and control methods is still needed to enable single-stage topologies to meet the requirements of high efficiency, high power density, and a wide voltage gain range. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and propose a bridgeless single-stage AC-DC resonant converter that can change the equivalent AC input voltage amplitude of the AC-DC resonant converter, thereby significantly widening the voltage gain range of the topology.

[0006] To achieve the above objectives, the technical solution specifically adopted by the present invention is as follows: A bridgeless single-stage AC-DC resonant converter includes a linear-resonant circuit and an output rectifier circuit. The linear-resonant circuit converts the AC input voltage into a high-frequency alternating signal, and the rectifier circuit rectifies the high-frequency signal into a stable, high-quality DC output. This is achieved through the resonant capacitor C. r The voltage across the terminals determines whether the circuit is operating in linear or resonant mode. The positive input of the linear-resonant circuit is connected to one end of the low-pass filter's output, and the negative input is connected to the other end. One output of the linear-resonant circuit is connected to one input of the output rectifier circuit, and its other output is connected to the other end of the output rectifier circuit. One output of the output rectifier circuit is connected to the output capacitor C. o1 The positive terminal of the output rectifier circuit is connected to the positive terminal of the output load battery; the other end of the output rectifier circuit is connected to the output capacitor C. o2 Connect the negative terminal to the output load battery.

[0007] The linear-resonant circuit includes switching transistors Q1 and Q2, diodes D1 and D2, and a bus capacitor C. b Resonant capacitor C r and resonant inductance L r The primary winding N of transformer T1 p and secondary winding N s The gate of the switching transistor Q1 is connected to the drive signal output unit. v Gs1 The gate of the switching transistor Q2 is connected to the drive signal output unit. v Gs2 The source of switching transistor Q1 is connected to the primary winding N of the transformer. p One end of the transistor is connected to the drain of the switching transistor Q2, and the drain of the switching transistor Q1 is connected to the bus capacitor C. b One end of the transistor is connected to the cathode of diode D1, and the source of switch Q2 is connected to resonant capacitor C. r One end of the diode, the anode of diode D2, and the bus capacitor C b The other end; resonant capacitor C r The other end is connected to one end of the low-pass filter output side, the anode of diode D1, and the cathode of diode D2; resonant inductor L r One end is connected to the output side of the low-pass filter, and the other end is connected to the primary winding N of the transformer. p The other end. One end of the low-pass filter input is connected to the AC input voltage. v ac One end of the low-pass filter is connected to the AC input voltage, and the other end is connected to the input voltage. v ac The other end. Resonant capacitor C rThe capacitance value is much smaller than the bus capacitance C. b The capacitance value, the resonant capacitor C r With bus capacitor C b The capacitance value in series and the resonant capacitance C r Since the capacitance values ​​are approximately equal, the resonant capacitor connected in parallel with diode D1 is omitted, simplifying the circuit structure. Transformer secondary winding N s One end serves as the positive output terminal of the linear-resonant circuit, and the secondary winding N of the transformer... s The other end serves as the negative output terminal of the linear-resonant circuit, where the resonant inductance L... r and transformer T1 primary winding N p The sequence order can be changed.

[0008] Preferably, the output rectifier circuit uses a DC blocking capacitor C. d The voltage doubler rectifier circuit includes a DC blocking capacitor C. d The voltage doubler rectifier circuit includes diodes D3 and D4, and DC blocking capacitor C. d Output capacitors Co1 and Co2. The anode of diode D3 is connected to the N winding of the transformer complex winding. s One end of diode D3 is connected to the cathode of diode D4; the cathode of diode D3 is connected to one end of output capacitor Co1 and the positive terminal of the load battery; the anode of diode D4 is connected to one end of output capacitor Co2 and the negative terminal of the load battery; the DC blocking capacitor C... d One end is connected to the secondary winding N of the transformer. s At the other end, the DC blocking capacitor C d The other end is connected to the other end of the output capacitor Co1 and the other end of the output capacitor Co2. The output rectifier circuit can also use full-bridge rectification, full-wave rectification, or other output rectifier circuits.

[0009] The present invention also includes a controller for a bridgeless single-stage AC-DC resonant converter, the controller comprising an output current signal conditioning circuit K. i1 Input current signal conditioning circuit K i2 Output voltage signal conditioning circuit K v1 Input voltage signal conditioning circuit K v2 Subtractor U c1 Subtractor U c2 Subtractor U c4 PI controller 1, PI controller 2, PI controller 3, multiplier U c3 Phase-locked loop (PLL), feedforward meter, adder U c5 Divider U c6 Root mean square (RMS) value calculation unit, duty cycle calculation unit, and drive signal controller.

[0010] The output voltage signal conditioning circuit K v1Sampling load battery output voltage V o One of the output signal terminals is connected to the subtractor U. c1 One signal input terminal is connected to the output voltage signal conditioning circuit K. v1 The other output signal terminal is connected to one input terminal of the feedforward meter, subtractor U c1 Another signal input terminal is connected to the output voltage reference signal. V o_ref The input terminals are connected, and the subtractor U... c1 The output signal terminal of PI controller 1 is connected to the input terminal of PI controller 1, and the output signal terminal of PI controller 1 is connected to one input terminal of constant voltage / constant current selector.

[0011] The output current signal conditioning circuit K i1 Sampling load battery output current I o One of its output signal terminals is connected to the subtractor U. c2 Connected to one of the signal input terminals, subtractor U c2 Another signal input terminal is connected to the output current reference signal I o_ref The input terminals are connected, and the subtractor U... c2 The output signal terminal of PI controller 1 is connected to the input terminal of PI controller 2. The output signal terminal of PI controller 2 is connected to the other input terminal of the constant voltage / constant current selector. The constant voltage / constant current selector selects the output signal of PI controller 1 or the output signal of PI controller 2 according to different output requirements.

[0012] The input voltage signal conditioning circuit K v2 Sampled input voltage v ac One end of its output signal terminal is connected to the input terminal of the phase-locked loop (PLL), and the other end is connected to the input terminal of the root mean square (RMS) value calculation unit. The input voltage signal conditioning circuit K... v2 The output signal is sent to the root mean square (RMS) value calculation unit, and the output signal of the RMS value calculation unit is sent to the divider U. c6 One end simultaneously outputs the reference value V of the voltage signal. o_ref Feed into divider U c6 At the other end, the divider U c6 The output result is sent to the duty cycle calculation unit, and the output signal of the duty cycle calculation unit is sent to the drive signal controller; input voltage v ac The input voltage phase θ is obtained after passing through the phase-locked loop (PLL) and sent to the |sin(θ)| calculation unit; the input voltage phase θ is sent to another input terminal of the feedforward meter; the obtained |sin(θ)| signal and the output signal of PI controller 1 or PI controller 2 are multiplied by the multiplier U c3 Multiply to obtain the input current reference signal.i ac_ref And fed into subtractor U c4 One of the input terminals.

[0013] The input current signal conditioning circuit K i2 Sample input current i ac Its output signal terminal is connected to the subtractor U c4 The other input is connected to the multiplier U. c3 Output signal to subtractor U c4 Subtractor U c4 The output signal is sent to PI controller 3; the output signals of the feedforward meter and PI controller 3 are sent to adder U. c5 via adder U c5 The processed output signal is sent to the drive signal controller. The drive signal controller then outputs the drive signal. v Gs1 The drive signal is output to the gate of the switching transistor Q1. v Gs2 The output voltage is controlled and the power factor is corrected by changing the switching frequency and duty cycle of the switching transistors Q1 and Q2, which are connected to the gate of the switching transistor Q2.

[0014] This invention has the following characteristics and beneficial effects: Depending on the voltage across the resonant capacitor, the circuit operates in either linear or resonant mode. Taking the positive half-cycle of the input voltage as an example, when the voltage across the resonant capacitor drops to zero, the loop current flows through the diode D2 connected in parallel across the resonant capacitor. The multiplexing of the resonant inductor and the magnetizing inductor enables resonance and boost functions within a single switching cycle. Furthermore, through duty cycle-frequency coordinated control, the equivalent AC input voltage amplitude of the AC-DC converter is effectively altered, thereby significantly widening the topology voltage gain range and improving the conversion efficiency of the single-stage AC-DC resonant converter. Attached Figure Description

[0015] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a traditional single-stage LLC PFC resonant converter topology; Figure 2 This is a circuit diagram of a single-stage AC-DC resonant converter suitable for electric vehicle charging according to an embodiment of the present invention; Figure 3 This is a controller circuit diagram of a single-stage AC-DC resonant converter suitable for electric vehicle charging, according to an embodiment of the present invention. Figure 4(a) shows the equivalent circuit of mode I of a single-stage AC-DC resonant converter suitable for electric vehicle charging according to an embodiment of the present invention; Figure 4(b) shows the equivalent circuit of a single-stage AC-DC resonant converter mode II suitable for electric vehicle charging according to an embodiment of the present invention; Figure 4(c) shows the equivalent circuit of a single-stage AC-DC resonant converter mode III suitable for electric vehicle charging according to an embodiment of the present invention; Figure 4(d) shows the equivalent circuit of mode IV of a single-stage AC-DC resonant converter suitable for electric vehicle charging according to an embodiment of the present invention; Figure 4(e) shows the equivalent circuit of mode V of a single-stage AC-DC resonant converter suitable for electric vehicle charging according to an embodiment of the present invention; Figure 4(f) shows the equivalent circuit of mode VI of a single-stage AC-DC resonant converter suitable for electric vehicle charging according to an embodiment of the present invention; Figure 5(a) shows the key waveform of the discontinuous current mode switching cycle of a single-stage AC-DC resonant converter suitable for electric vehicle charging according to an embodiment of the present invention. Figure 5(b) shows the key waveforms of the continuous current mode switching cycle of a single-stage AC-DC resonant converter suitable for electric vehicle charging according to an embodiment of the present invention. Detailed Implementation

[0016] The present invention will now be described in detail with reference to embodiments 1. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that, unless otherwise specified, the embodiments and features described in the embodiments of the present invention can be combined with each other.

[0017] A typical LLC resonant converter topology is as follows: Figure 1 As shown, this invention provides a bridgeless single-stage AC-DC resonant converter suitable for wide voltage applications, employing... Figure 2 The circuit 100 shown and Figure 3 The controller 101 and circuit 100 shown include a resonant-linear circuit 1001 and an output rectifier circuit 1002. The positive input terminal of the linear-resonant circuit 1001 is connected to one end of the output side of the low-pass filter, and its negative input terminal is connected to the other end of the output side of the low-pass filter. One end of the output side of the linear-resonant circuit is connected to one input terminal of the output rectifier circuit 1002, and its other output terminal is connected to the other end of the output rectifier circuit. One output terminal of the output rectifier circuit is connected to the output capacitor C. o1 The positive terminal of the output rectifier circuit is connected to the positive terminal of the output load battery; the other end of the output rectifier circuit is connected to the output capacitor C. o2 Connect the negative terminal to the output load battery.

[0018] The linear-resonant circuit 1001 includes switching transistors Q1 and Q2, diodes D1 and D2, and a bus capacitor C. b Resonant capacitor C r and resonant inductance L r The primary winding N of transformer T1 p and secondary winding N s The gate of the switching transistor Q1 is connected to the output of the drive signal controller. v GS1 The gate of the switching transistor Q2 is connected to the output of the drive signal controller. v GS2 The source of switching transistor Q1 is connected to the primary winding N of the transformer. p One end of the transistor is connected to the drain of the switching transistor Q2, and the drain of the switching transistor Q1 is connected to the bus capacitor C. b One end of the transistor is connected to the cathode of diode D1, and the source of switch Q2 is connected to resonant capacitor C. r One end of the diode, the anode of diode D2, and the bus capacitor C b The other end; resonant capacitor C r The other end is connected to one end of the low-pass filter output side, the anode of switch D1, and the cathode of switch D2; resonant inductor L r One end is connected to the output side of the low-pass filter, and the other end is connected to the primary winding N of the transformer. p The other end. One end of the low-pass filter input is connected to the AC input voltage. v ac One end of the low-pass filter is connected to the AC input voltage, and the other end is connected to the input voltage. v ac The other end. The transformer secondary winding N s One end serves as the positive output terminal of the linear-resonant circuit, and the secondary winding N of the transformer... s The other end serves as the negative output terminal of the linear-resonant circuit. The resonant inductance L... r and transformer T1 primary winding N p The sequence order can be changed.

[0019] The output rectifier circuit 1002 can be equipped with a DC blocking capacitor C. d The voltage doubler rectifier circuit includes a DC blocking capacitor C. d The voltage doubler rectifier circuit includes diodes D3 and D4, and DC blocking capacitor C. d Output capacitors Co1 and Co2. The anode of diode D3 is connected to the N winding of the transformer complex winding. s One end of diode D3 is connected to the cathode of diode D4; the cathode of diode D3 is connected to one end of output capacitor Co1 and the positive terminal of the load battery; the anode of diode D4 is connected to one end of output capacitor Co2 and the negative terminal of the load battery; the DC blocking capacitor C... dOne end is connected to the secondary winding N of the transformer. s At the other end, the DC blocking capacitor C d The other end is connected to the other end of the output capacitor Co1 and the other end of the output capacitor Co2. The output rectifier circuit can also use full-bridge rectification, full-wave rectification, or other output rectifier circuits.

[0020] To further illustrate this invention, the positive half-cycle of the AC input voltage in discontinuous current mode is used as an example to explain the circuit's operating principle during the switching cycle. Similar to a conventional LLC converter, this topology operates in either discontinuous current mode or continuous current mode when the input and output voltages change, and the proportion of the switching cycle occupied by the linear mode duration increases with increasing input power. In Figures 5(a) and 5(b), v G1 v G2 These are the drive signals for switching transistors Q1 and Q2, respectively. m For the magnetizing inductor current, i r For the resonant inductor current, i D2 V is the current across diode D2. m Let t0 be the voltage across the primary transformer T1. The starting point is defined as when the resonant current drops to zero, at which point the resonant capacitor voltage is zero. When the resonant capacitor voltage is not zero, the circuit is in resonant mode; when the resonant capacitor voltage is zero, the circuit is in linear mode.

[0021] Figure 4(a) is an equivalent circuit diagram of the first operating mode of the bridgeless single-stage AC-DC resonant converter according to an embodiment of the present invention, corresponding to the t0-t1 time period in the key waveform diagram of the discontinuous current mode switching cycle in Figure 5(a). At this time, switch Q1 is on, Q2 is off, the resonant capacitor voltage is not zero, diodes D1 and D2 are off, diode D3 in the rectifier circuit is off, and D4 is on, and the converter enters the resonant mode. The resonant current i r The bus capacitor C flows through b At this point, the converter's characteristics are the same as those of a traditional LLC resonant converter in P mode, with the transformer's primary winding clamped by the secondary rectifier circuit. This continues until the resonant current i... r With excitation current i m If they are equal, proceed to the next stage.

[0022] Figure 4(b) is an equivalent circuit diagram of the second operating mode of the bridgeless single-stage AC-DC resonant converter according to an embodiment of the present invention, corresponding to the t1-t2 time period in the key waveform diagram of the discontinuous current mode switching cycle in Figure 5(a). Switch Q1 remains on, Q2 remains off, diodes D1 and D2 are off, and diodes D3 and D4 in the rectifier circuit are off. During this stage, the magnetizing inductor L... m No longer clamped by the secondary rectifier circuit, L m With resonant inductor L r and resonant capacitor Cr Resonance occurs when the output capacitor C is in resonance. 01 and output capacitor C O2 Together, they maintain the power supply to the output. Simultaneously, the resonant current i r The output capacitor of the switching transistor Q2 is discharged to achieve soft switching.

[0023] Figure 4(c) is an equivalent circuit diagram of the third operating mode of the bridgeless single-stage AC-DC resonant converter according to an embodiment of the present invention, corresponding to the t2-t3 time period in the key waveform diagram of the discontinuous current mode switching cycle in Figure 5(a). Switch Q1 is off, Q2 is on, diodes D1 and D2 are off, diode D3 in the rectifier circuit is on, and D4 is off. The primary winding of the transformer is clamped by the secondary rectifier circuit, which is the same as the P stage of a traditional LLC resonant converter. At this time, the resonant current I... r The resonant capacitor is used to control the circuit. When the voltage across the resonant capacitor drops to zero, this phase ends, marking the end of the resonant mode and the circuit will enter the linear mode.

[0024] Figure 4(d) is an equivalent circuit diagram of the fourth operating mode of the bridgeless single-stage AC-DC resonant converter according to an embodiment of the present invention, corresponding to the t3-t4 time period in the key waveform diagram of the discontinuous current mode switching cycle in Figure 5(a). Switch Q1 remains off, Q2 remains on, the resonant capacitor voltage drops to zero, diode D1 is off, diode D2 is on, diode D3 in the rectifier circuit is on, and diode D4 is off. The resonant current i r Through diode D2, the converter enters linear mode. At this time, the primary winding is still clamped by the secondary rectifier circuit, and the resonant current i r The linear decrease continues until it matches the excitation current i. m If the same applies, this phase ends.

[0025] Figure 4(e) is an equivalent circuit diagram of the fifth operating mode of the bridgeless single-stage AC-DC resonant converter according to an embodiment of the present invention, corresponding to the t4-t5 time period in the key waveform diagram of the discontinuous current mode switching cycle in Figure 5(a). Switch Q1 remains off, Q2 remains on, diode D1 is off, diode D2 is on, and diodes D3 and D4 in the rectifier circuit are off. During this stage, the magnetizing inductor is no longer clamped by the secondary rectifier circuit, and the resonant current i... r With excitation current i m Rising in sync.

[0026] Figure 4(f) is an equivalent circuit diagram of the sixth operating mode of the bridgeless single-stage AC-DC resonant converter according to an embodiment of the present invention, corresponding to the t5-t6 time period in the key waveform diagram of the discontinuous current mode switching cycle in Figure 5(a). Switch Q1 is turned on, Q2 is turned off, diode D2 is turned on, diode D1 is turned off, diode D3 in the rectifier circuit is turned off, and diode D4 is turned on. At this time, the primary winding of the transformer is clamped by the secondary rectifier circuit, and the magnetizing current i m The linear decrease occurs, while the resonant current i r The current decreases, preparing for the soft switching of switch Q2 in the next stage. This continues until the resonant current i... r This phase ends when the current drops to zero, which means the linear mode ends and diode D2 achieves zero-current turn-off.

[0027] The controller 101 includes an output current signal conditioning circuit K. i1 Input current signal conditioning circuit K i2 Output voltage signal conditioning circuit K v1 Input voltage signal conditioning circuit K v2 Subtractor U c1 Subtractor U c2 Subtractor U c4 PI controller 1, PI controller 2, PI controller 3, multiplier U c3 Phase-locked loop (PLL), feedforward meter, adder U c5 Divider U c6 Root mean square value calculation unit, duty cycle calculation unit, drive signal controller; The output voltage signal conditioning circuit K v1 Sampling load battery output voltage V o The output voltage signal conditioning circuit K v1 One of the output signal terminals is connected to the subtractor U c1 Connected to one input terminal, subtractor U c1 Another signal input terminal is connected to the output voltage reference signal. V o_ref The input terminals are connected, and the subtractor U... c1 The output signal is sent to PI controller 1, and the output signal of PI controller 1 is sent to one input terminal of the constant voltage / constant current selector. The output voltage signal conditioning circuit K v1 The other output signal terminal is connected to one input terminal of the feedforward meter; the output current signal conditioning circuit K i1 Sampling load battery output current I o The output current signal conditioning circuit K i1 The output signal terminal of the subtractor U c2 Connected to one input terminal, subtractor U c2The output signal is sent to PI controller 2, and the output signal of PI controller 2 is sent to the other input terminal of the constant voltage / constant current selector; the constant voltage / constant current selector selects the output signal of PI controller 1 or the output signal of PI controller 2 according to the output requirements; the input voltage signal conditioning circuit K v2 Sampled input voltage v ac One end of its output signal terminal is connected to the input terminal of the phase-locked loop (PLL), and the other end is connected to the input terminal of the root mean square (RMS) value calculation unit, thus conditioning the input voltage signal K. v2 The output signal is sent to the root mean square (RMS) value calculation unit, and the output signal of the RMS value calculation unit is sent to the divider U. c6 One end simultaneously outputs the reference value V of the voltage signal. o_ref Feed into divider U c6 At the other end, the divider U c6 The output result is sent to the duty cycle calculation unit, and the output signal of the duty cycle calculation unit is sent to the drive signal controller. The input voltage passes through the phase-locked loop (PLL) to obtain the input voltage phase θ, which is then sent to the |sin(θ)| calculation unit; the input voltage phase θ is sent to one input terminal of the feedforward meter; the obtained |sin(θ)| signal is multiplied by the output signal of PI controller 1 or PI controller 2 via multiplier U. c3 Multiply to obtain the input current reference signal. i ac_ref And fed into subtractor U c4 One input terminal; the input current signal conditioning circuit K i2 Sample input current i ac The signal is sent to the subtractor U via the output signal terminal. c4 Multiplier U c3 Output signal to subtractor U c4 Subtractor U c4 The output signal is sent to PI controller 3; the output signals of the feedforward meter and PI controller 3 are sent to adder U. c5 via adder U c5 The processed output signal is sent to the drive signal controller.

[0028] The controller 101 is used to implement constant voltage / current output and power factor correction control of a specific embodiment of a novel bridgeless single-stage AC-DC resonant converter circuit 100 suitable for electric vehicle charging applications. Its control principle is as follows: When the current output is constant current, i.e., the output signal terminal of the PI controller 1 is connected to the multiplier U... c3 Connect one signal input terminal to sample the output voltage V. o Input signal conditioning circuit K v1 The conditioned signal is compared with the preset reference voltage V. o_refSubtractor U c1 Obtain the error signal e v1 The signal is then sent to PI controller 1, and the output signal of PI controller 1 ultimately affects the output v of the drive signal controller. Gs1 and v Gs2 v Gs1 and v Gs2 These are connected to the gates of switching transistors Q1 and Q2 respectively. A constant output voltage is achieved by changing the switching frequency and duty cycle of switching transistors Q1 and Q2. Currently, when the output is constant current, the output signal terminal of PI controller 2 is connected to the multiplier U. c3 Connect one of the signal input terminals to sample the output current I. o Input signal conditioning circuit K i1 The conditioned signal and the reference voltage I o_ref Subtractor U c2 Obtain the error signal e i1 The signal is then sent to PI controller 2, and the output signal of PI controller 2 will also affect the output of the drive signal controller. Gs1 and v Gs2 The output current is kept constant by changing the switching frequency and duty cycle of switching transistors Q1 and Q2. The input voltage is sampled. v ac Input signal conditioning circuit K v2 The input voltage signal conditioning circuit K v2 Sampled input voltage v ac One end of its output signal terminal is connected to the input terminal of the phase-locked loop (PLL), and the other end is connected to the input terminal of the root mean square (RMS) value calculation unit, thus conditioning the input voltage signal K. v2 The output signal is sent to the root mean square (RMS) value calculation unit, and the output signal of the RMS value calculation unit is sent to the divider U. c6 One end simultaneously outputs the reference value V of the voltage signal. o_ref Feed into divider U c6 At the other end, the divider U c6 The output of the divider is sent to the duty cycle calculation unit. c6The result represents the gain required by the converter under the current input voltage. Since the gain curve has inherent boundaries when relying solely on frequency conversion control, duty cycle control is introduced to change the effective voltage amplitude applied to the resonant network, thereby expanding the upper and lower limits of the gain. When the required gain cannot be met by frequency conversion control alone, duty cycle-frequency coordinated control is used. The output signal of the duty cycle calculation unit is sent to the drive signal controller. The conditioned input voltage signal passes through a phase-locked loop (PLL) to obtain the input voltage phase θ. The |sin(θ)| signal is obtained by the calculation unit and multiplied by the output signal of PI controller 1 or PI controller 2 via multiplier U. c3 Multiplying them yields an input current reference signal that is in phase with the input voltage. i ac_ref Sample input current i ac Input signal conditioning circuit K i2 The conditioned signal and the input current reference signal i ac_ref Subtractor U c4 Obtain the error signal e i2 The signal is fed into PI controller 3 to achieve input current waveform tracking control. To improve the tracking effect of the input current waveform and reduce input current harmonics, feedforward control is typically introduced. The feedforward meter reduces the amplitude of the change in the output of the inner-loop PI regulator, thus enhancing the tracking effect of the input current without affecting the current loop response speed. The pre-designed feedforward meter and the output signal of PI controller 3 are fed into adder U. c5 The control signal is obtained by adding them together. e c1 The signal is fed into the drive signal controller. The feedforward table can be obtained by fitting the switching frequency results from theoretical calculations or circuit simulation. The controller 101 can be implemented using a digital controller or an analog circuit.

[0029] This invention focuses on the challenge of synergistic optimization between wide voltage gain and high efficiency conversion in single-stage topologies. It proposes a composite circuit structure integrating linear and resonant circuits, and comprehensively considers converter efficiency, cost, harmonics, and power density in parameter design and device selection, resulting in a novel bridgeless isolated single-stage AC-DC resonant converter scheme. This scheme features low overall cost, compact structure, and simple control. Its small size and weight meet the lightweight and miniaturization requirements of electric vehicles; its wide gain range meets the input voltage and current requirements of power batteries; and its high efficiency and low total harmonic distortion enable fast and high-quality charging of electric vehicles. This invention provides a high-efficiency, high-power-density single-stage isolated converter scheme for the electric vehicle field, offering a new path to overcome the challenge of simultaneously achieving wide voltage gain and high efficiency in traditional LLC resonant converters, effectively promoting the innovation of mainstream topologies in the electric vehicle charging field.

[0030] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A bridgeless single-stage AC-DC resonant converter, characterized in that, This includes linear-resonant circuits and output rectifier circuits; The positive input terminal of the linear-resonant circuit is connected to one end of the output side of the low-pass filter, and the negative input terminal of the linear-resonant circuit is connected to the other end of the output side of the low-pass filter; one end of the output side of the linear-resonant circuit is connected to one input terminal of the output rectifier circuit, and the other output terminal is connected to the other end of the output rectifier circuit; one output terminal of the output rectifier circuit is connected to the positive terminal of the output load battery; the other end of the output rectifier circuit is connected to the negative terminal of the output load battery.

2. The bridgeless single-stage AC-DC resonant converter according to claim 1, characterized in that, The linear-resonant circuit includes switching transistors Q1 and Q2, diodes D1 and D2, and a bus capacitor C. b Resonant capacitor C r and resonant inductance L r The primary winding N of transformer T1 p and secondary winding N s ; The gate of the switching transistor Q1 is connected to the drive signal output unit. v Gs1 The gate of the switching transistor Q2 is connected to the drive signal output unit. v Gs2 The source of the switching transistor Q1 is connected to the primary winding N of the transformer. p One end of the transistor is connected to the drain of the switching transistor Q2, and the drain of the switching transistor Q1 is connected to the bus capacitor C. b One end of the transistor is connected to the cathode of diode D1, and the source of switch Q2 is connected to resonant capacitor C. r One end of the diode, the anode of diode D2, and the bus capacitor C b The other end; resonant capacitor C r The other end is connected to one end of the low-pass filter output side, the anode of diode D1, and the cathode of diode D2; resonant inductor L r One end is connected to the output side of the low-pass filter, and the other end is connected to the primary winding N of the transformer. p The other end; one end of the low-pass filter input is connected to the AC input voltage. v ac One end of the low-pass filter is connected to the AC input voltage, and the other end is connected to the input voltage. v ac The other end; transformer secondary winding N s One end serves as the positive output terminal of the linear-resonant circuit, and the secondary winding N of the transformer... s The other end serves as the negative output terminal of the linear-resonant circuit.

3. A bridgeless single-stage AC-DC resonant converter according to claim 2, characterized in that, The resonant inductor L r and transformer T1 primary winding N p The sequence order can be changed.

4. A bridgeless single-stage AC-DC resonant converter according to claim 2, characterized in that, The resonant capacitor C r The capacitance value is much smaller than the bus capacitance C. b The capacitance value.

5. A bridgeless single-stage AC-DC resonant converter according to claim 1, characterized in that, The output rectifier circuit uses a DC blocking capacitor C. d A voltage doubler rectifier circuit; The capacitor containing DC blocking capacitor C d The voltage doubler rectifier circuit includes diode D3, diode D4, and DC blocking capacitor C. d Output capacitor Co1, output capacitor Co2; diode D3 anode connected to transformer complex winding N. s One end of diode D3 is connected to the cathode of diode D4; the cathode of diode D3 is connected to one end of output capacitor Co1 and the positive terminal of the load battery; the anode of diode D4 is connected to one end of output capacitor Co2 and the negative terminal of the load battery; the DC blocking capacitor C... d One end is connected to the secondary winding N of the transformer. s At the other end, the DC blocking capacitor C d The other end is connected to the other end of the output capacitor Co1 and the other end of the output capacitor Co2.

6. A bridgeless single-stage AC-DC resonant converter according to claim 1, characterized in that, The output rectifier circuit can also employ full-bridge rectification or full-wave rectification output rectifier circuits.

7. A bridgeless single-stage AC-DC resonant converter according to any one of claims 1 to 6, characterized in that, The bridgeless single-stage AC-DC resonant converter also includes a controller, which is implemented as follows: The output voltage signal conditioning circuit K v1 Sampling load battery output voltage V o One of the output signal terminals is connected to the subtractor U. c1 One signal input terminal is connected to the output voltage signal conditioning circuit K. v1 The other output signal terminal is connected to one input terminal of the feedforward meter, subtractor U c1 Another signal input terminal is connected to the output voltage reference signal. V o_ref The input terminals are connected, and the subtractor U... c1 The output signal terminal of is connected to the input terminal of PI controller 1, and the output signal terminal of PI controller 1 is connected to one input terminal of the constant voltage / constant current selector. The output current signal conditioning circuit K i1 Sampling load battery output current I o One of its output signal terminals is connected to the subtractor U. c2 Connected to one of the signal input terminals, subtractor U c2 Another signal input terminal is connected to the output current reference signal I o_ref The input terminals are connected, and the subtractor U... c2 The output signal terminal of PI controller 1 is connected to the input terminal of PI controller 2, and the output signal terminal of PI controller 2 is connected to the other input terminal of constant voltage / constant current selector. The constant voltage / constant current selector selects the output signal of PI controller 1 or the output signal of PI controller 2 according to different output requirements. The input voltage signal conditioning circuit K v2 Sampled input voltage v ac One end of its output signal terminal is connected to the input terminal of the phase-locked loop (PLL), and the other end is connected to the input terminal of the root mean square (RMS) value calculation unit; the input voltage signal conditioning circuit K... v2 The output signal is sent to the root mean square (RMS) value calculation unit, and the output signal of the RMS value calculation unit is sent to the divider U. c6 One end simultaneously outputs the reference value V of the voltage signal. o_ref Feed into divider U c6 At the other end, the divider U c6 The output result is sent to the duty cycle calculation unit, and the output signal of the duty cycle calculation unit is sent to the drive signal controller; input voltage v ac The input voltage phase θ is obtained after passing through the phase-locked loop (PLL) and sent to the |sin(θ)| calculation unit; the input voltage phase θ is sent to another input terminal of the feedforward meter; the obtained |sin(θ)| signal and the output signal of PI controller 1 or PI controller 2 are multiplied by the multiplier U c3 Multiply to obtain the input current reference signal. i ac_ref And fed into subtractor U c4 One of the input terminals; The input current signal conditioning circuit K i2 Sample input current i ac Its output signal terminal is connected to the subtractor U c4 The other input is connected to the multiplier U. c3 Output signal to subtractor U c4 Subtractor U c4 The output signal is sent to PI controller 3; the output signals of the feedforward meter and PI controller 3 are sent to adder U. c5 via adder U c5 The processed output signal is sent to the drive signal controller; the drive signal controller outputs the drive signal. v Gs1 The drive signal is output to the gate of the switching transistor Q1. v Gs2 The output voltage is controlled and the power factor is corrected by changing the switching frequency and duty cycle of the switching transistors Q1 and Q2, which are connected to the gate of the switching transistor Q2.

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