Multi-mode AC-DC LLC resonant converter topology and control strategy thereof

Abstract

The invention discloses a multi-mode AC-DC LLC resonant converter topology and a control strategy thereof, the topology comprises an input rectification circuit, an LLC resonant converter circuit and an output rectification circuit, the positive output end of the input rectification circuit is connected with the positive input end of the LLC resonant converter circuit, and the negative output end of the input rectification circuit is connected with the negative input end of the LLC resonant converter circuit and is connected with the input ground; one end of the output side of the LLC resonant converter circuit is connected with one input end of the output rectifying circuit, and the other output end of the LLC resonant converter 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 capacitor Co and is connected with the positive end of the output load battery Ro; and the other end of the output rectifying circuit is connected with the negative end of the output capacitor and is connected with the negative end of the output load battery Ro. According to the invention, the equivalent AC input voltage amplitude of the AC-DC LLC resonant converter can be effectively changed, so that the voltage gain range of the topology is obviously widened.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to a multi-mode AC-DC LLC resonant converter topology and a control strategy thereof. Background Art

[0002] In recent years, with the rapid development of the electric vehicle industry, on-board chargers have attracted much attention as an important component of electric vehicles. Taking the typical 400V voltage platform of electric vehicles as an example, the charging voltage range of its power battery pack is about 250V to 420V. If pre-charging is taken into account, the charging voltage range will reach an ultra-wide 100 to 420V, which poses a challenge to the design of on-board chargers.

[0003] Traditional on-board chargers usually adopt a two-stage architecture, with the front stage as a PFC (Power Factor Correction) unit to achieve AC-DC conversion, and the back stage using a DC-DC converter to achieve wide output voltage regulation. A typical single-phase on-board charger solution uses a totem pole Boost converter as the front stage and an LLC converter as the back stage. Since both the front and back stage topologies require independent active and passive power devices, and high-voltage and large-capacity electrolytic capacitors need to be connected in parallel between the front and back stages, the two-stage system solution is costly, large in size, and has low reliability, and it is becoming increasingly difficult to meet commercial application requirements.

[0004] The AC-DC PFC converter based on the single-stage architecture is regarded as a feasible solution with its advantages of low cost, high efficiency and high power density. The single-stage LLC resonant converter is used in medium and high power AC-DC conversion due to its high efficiency, low cost and simple control. Its typical topology is as follows: Figure 1 As shown. However, since the traditional single-stage AC-DC LLC topology adopts PFM (Pulse Frequency Modulation) control, its output voltage gain variation range is limited. If the parameter optimization design is sacrificed to meet the wide voltage gain, the overall efficiency performance of the converter under wide voltage changes will be reduced. On the other hand, when considering the pre-charging requirements of electric vehicles, the on-board charger based on the single-stage AC-DC LLC resonant converter is difficult to meet the application requirements of a wide voltage of 100 to 420V. Therefore, how to broaden the voltage gain of the traditional single-stage AC-DC LLC topology while maintaining high-efficiency power conversion is a very challenging task. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a multi-mode AC-DC LLC resonant converter topology and its control strategy, which can effectively change the equivalent AC input voltage amplitude of the AC-DC LLC resonant converter, thereby significantly widening the voltage gain range of the topology.

[0006] In order to achieve the above object, the technical solution specifically adopted by the present invention is as follows:

[0007] A multi-mode AC-DC LLC resonant converter topology includes an input rectifier circuit, an LLC resonant converter circuit, and an output rectifier circuit. The positive output terminal of the input rectifier circuit is connected to the positive input terminal of the LLC resonant converter circuit, and the negative output terminal thereof is connected to the negative input terminal of the LLC resonant converter circuit and connected to the input ground; one terminal of the output side of the LLC resonant converter circuit is connected to an input terminal of the output rectifier circuit, and the other output terminal thereof is connected to the other terminal of the output rectifier circuit. One output terminal of the output rectifier circuit is connected to an output capacitor C o The positive terminal is connected to the output load battery R o The other end of the output rectifier circuit is connected to the negative end of the output capacitor and connected to the output load battery R o The negative terminal.

[0008] The input rectifier circuit includes an input inductor L b , switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 , input inductance L b One end is connected to the AC source v ac One end of the input inductor L b The other end is connected to the switch tube S 1 The source and S 2 The drain, AC source v ac The other end is connected to the switch tube Q 1 source and Q 2 The drain of switch S 1 The drain of Q 1 The drain of the switch S 2 The source is connected to Q 2 The source of the rectifier circuit serves as the negative output terminal of the input rectifier circuit.

[0009] The LLC resonant converter circuit adopts a full-bridge LLC topology, including an input capacitor C in , multiplexed switch tube Q 1 And the switch tube Q 2 , switch tube Q 3 , switch tube Q 4 , resonant capacitor C rand resonant inductor L r , transformer T 1 The primary winding N p and the secondary winding N s . Input capacitor C in The positive end of the input rectifier circuit is connected to the positive output end and the switch tube Q 1 And the switch tube Q 3 The drain of the LLC resonant converter circuit is used as the positive input terminal; the input capacitor C in The negative end of the input rectifier circuit is connected to the negative output end and the switch tube Q 2 And the switch tube Q 4 The source of the switch tube Q is connected to ground and serves as the negative input terminal of the LLC resonant converter circuit; 1 The source of the switch tube Q 2 The drain and resonant capacitor C r One end of the switch tube Q 3 The source of the switch tube Q 4 The drain and the transformer primary winding N p The opposite end of the resonant capacitor C r The other end is connected to the resonant inductor L r One end of the resonant inductor L r The other end is connected to the primary winding N of the transformer p The same-name terminal of the transformer secondary winding N s The same-name end of the transformer secondary winding Ns is used as the positive output end of the LLC converter, and the opposite-name end of the transformer secondary winding Ns is used as the negative output end of the LLC converter. r , resonant inductor L r , transformer T 1 Primary winding N p The order of series connection can be reversed.

[0010] Preferably, the output rectifier circuit adopts a full-bridge rectifier circuit, and may also adopt output rectifier circuits such as voltage doubler rectifier and full-wave rectifier.

[0011] A multi-mode AC-DC LLC resonant converter topology of the present invention also includes a controller, the controller 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, feed-forward table and adder U c5 .

[0012] The output current signal conditioning circuit K v1 Sample output voltage V o , one of its output signal terminals is connected to the subtractor U c1 The input end of the subtractor U c1 The output signal end of the PI controller 1 is connected to the input end of the PI controller 1, and the output signal end of the PI controller 1 is connected to an input end of the constant voltage / constant current selector, and the output voltage signal conditioning circuit K v1 The other output signal terminal is connected to an input terminal of the feedforward table;

[0013] The output current signal conditioning circuit K i1 Sample output current I o , its output signal end is connected to the subtractor U c2 The input end of the subtractor U c2 The output signal end of is connected to the input end of PI controller 2, and the output signal end of PI controller 2 is connected to another input end 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 as needed.

[0014] The input voltage signal conditioning circuit K v2 Sample input voltage v ac , whose output signal end is connected to the input end of the phase-locked loop PLL; the input voltage signal conditioning circuit K v2 The output signal of the PLL is sent to the duty cycle adjustment module through the effective value calculation unit to obtain the high-frequency tube duty cycle D; the output of the phase-locked loop PLL obtains the input voltage phase θ and sends it to the |sin(θ)| calculation unit; the input voltage phase θ is sent to an input end of the feedforward table; the obtained |sin(θ)| signal and the output signal of the PI controller 1 or PI controller 2 are multiplied by the multiplier U c3 Multiply by to get the input current reference signal i ac_ref .

[0015] The input current signal conditioning circuit K i2 Sampling input current i ac , its output signal end is connected to the subtractor U c4 The input of the multiplier U c3 Output signal to subtractor U c4 , subtractor U c4 The output signal is sent to the PI controller 3; the output signal of the feedforward table and the PI controller 3 is sent to the adder U c5 , through adder U c5 After processing, the output signal is sent to the driver.

[0016] The present invention also provides a control strategy for the above-mentioned multi-mode AC-DC LLC resonant converter topology, which selects a suitable operating mode according to the magnitude of the output voltage amplitude, and uses hysteresis comparison to avoid oscillation problems during the switching process; in order to reduce the impact of the switching process on the input current waveform, the zero-crossing point (θ=0 or π) of the AC input voltage detected by the phase-locked loop PLL is used as the switching starting point, at which time the input power is almost zero, and the switching frequency of the converter is predictable: in modes IV and V, the switching frequency near the zero-crossing point is almost equal to the minimum frequency; for mode II, due to the use of frequency doubling technology, the switching frequency can be predicted in advance to be half of the minimum frequency, thereby reducing the impact of frequency mutations on the input current waveform and achieving smooth conversion between adjacent modes.

[0017] Specifically, the control strategy switches among five working modes according to the magnitude of the output voltage amplitude by changing the working states of the switch tubes S1, S2, Q1, Q2, Q3 and Q4, and then selects the appropriate working mode.

[0018] Among them, the five working modes are:

[0019] Mode I: The switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The switch tube Q 3 , switch tube Q 4 The input rectifier circuit 101 is composed of the switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The LLC converter 102 is composed of a bridge rectifier circuit, and the LLC converter 102 is composed of a switch tube Q 3 , switch tube Q 4 The half-bridge LLC circuit composed of the resonant cavity circuit has a fixed duty cycle of D = 0.5 for the high-frequency tube;

[0020] Mode II: The switch S 1 , switch tube S 2 The switch tube Q 1 , switch tube Q 2 , switch tube Q 3 , switch tube Q 4 The input rectifier circuit 101 is composed of the switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2The LLC converter 102 is composed of a totem pole rectifier circuit, wherein the switch tube Q 1 , switch tube Q 2 , switch tube Q 3 , switch tube Q 4 A full-bridge LLC circuit composed of a resonant cavity circuit; wherein the control strategy adopts a frequency doubling method, and the high-frequency tube has a fixed duty cycle of D=0.25;

[0021] Mode III: The switch S 1 , switch tube S 2 The switch tube Q 1 , switch tube Q 2 The switch tube Q performs high frequency switching during the power frequency cycle. 3 , switch tube Q 4 During the power frequency cycle, the input rectifier circuit 101 is operated as a power frequency synchronous rectifier switch; at this time, the input rectifier circuit 101 is operated by the switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The totem pole rectifier circuit is composed of the LLC converter 102, which is composed of the switch tube Q 1 , switch tube Q 2 A half-bridge LLC circuit composed of a resonant cavity circuit; wherein the high-frequency tube has a fixed duty cycle of D=0.5;

[0022] Mode IV: The switch S 1 , switch tube S 2 The switch tube Q performs high frequency switching during the power frequency cycle. 1 , switch tube Q 2 The switch tube Q 3 , switch tube Q 4 The input rectifier circuit 101 is composed of the switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The LLC converter 102 is composed of a totem pole rectifier circuit, wherein the switch tube Q 3 , switch tube Q 4 A half-bridge LLC circuit composed of a resonant cavity circuit; in which the high-frequency tube Q 3 , Q 4 The duty cycle D can be changed with the input voltage to adjust the bus voltage v bus The amplitude and the equivalent input voltage v of the resonant cavity ab The waveform of

[0023] Mode V: The switch tube S 1 , switch tube S2 , switch tube Q 1 , switch tube Q 2 , switch tube Q 3 , switch tube Q 4 The working state is the same as that of mode II; at this time, the input rectifier circuit 101 is composed of the switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The LLC converter 102 is composed of a totem pole rectifier circuit, wherein the switch tube Q 1 , switch tube Q 2 , switch tube Q 3 , switch tube Q 4 A full-bridge LLC circuit composed of a resonant cavity circuit; wherein the high-frequency tube duty cycle D can be changed with the input voltage to adjust the bus voltage v bus The amplitude and the equivalent input voltage v of the resonant cavity ab Waveform

[0024] The present invention has the following characteristics and beneficial effects:

[0025] By changing the control logic of the switch bridge arms S1-S2, Q1-Q4, the topology can be switched between single-stage / quasi-single-stage / two-stage modes; different mode combinations can be selected for different voltage gain ranges; different working modes can also be switched for output voltages at different stages, thereby effectively changing the equivalent AC input voltage amplitude of the AC-DC LLC resonant converter, thereby significantly widening the voltage gain range of the topology and improving the conversion efficiency of the single-stage AC-DC LLC resonant converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0027] Figure 1 It is a traditional single-stage LLC PFC resonant converter topology;

[0028] Figure 2 A circuit diagram of a novel multi-mode AC-DC LLC resonant converter suitable for wide voltage applications according to an embodiment of the present invention;

[0029] Figure 3 A controller circuit diagram of a novel multi-mode AC-DC LLC resonant converter suitable for wide voltage applications according to an embodiment of the present invention;

[0030] Figure 4A mode switching flow chart of a novel multi-mode AC-DC LLC resonant converter suitable for wide voltage applications according to an embodiment of the present invention;

[0031] Figure 5 The equivalent circuits of different modes of a novel multi-mode AC-DC LLC resonant converter suitable for wide voltage applications according to an embodiment of the present invention are as follows;

[0032] In the figure: (a) Mode I; (b) Mode II / Mode V; (c) Mode III; (d) Mode IV.

[0033] Figure 6 This is a key waveform diagram of the switching cycles of five specific modes of a novel multi-mode AC-DC LLC resonant converter suitable for wide voltage applications according to an embodiment of the present invention;

[0034] In the figure: (a) Mode I; (b) Mode II; (c) Mode III; (d) Mode IV; (e) Mode V. DETAILED DESCRIPTION

[0035] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

[0036] The present invention is a novel multi-mode AC-DC LLC resonant converter suitable for wide voltage applications, using Figure 2 The circuit 100 shown and Figure 3 The controller 101 shown in the figure, the circuit 100 includes an input rectifier circuit 1001, an LLC resonant converter circuit 1002 and an output rectifier circuit 1003. Among them, the positive output terminal of the input rectifier circuit 1001 is connected to the positive input terminal of the LLC resonant converter circuit 1002, and its negative output terminal is connected to the negative input terminal of the LLC resonant converter circuit 1002 and connected to the input ground. One end of the output side of the LLC resonant converter circuit 1002 is connected to an input end of the output rectifier circuit 1003, and the other output end is connected to the other end of the output rectifier circuit 1003. One output end of the output rectifier circuit 1003 is connected to the output capacitor C o The positive terminal is connected to the output load battery R o The other end of the output rectifier circuit 1003 is connected to the negative end of the output capacitor and connected to the output load battery R o The negative terminal.

[0037] The input rectifier circuit 1001 includes an input inductor L b , switch tube S 1 , switch tube S 2, switch tube Q 1 And the switch tube Q 2 , input inductance L b One end is connected to the AC source v ac One end of the input inductor L b The other end is connected to the switch tube S 1 The source and switch tube S 2 The drain, AC source v ac The other end is connected to the switch tube Q 1 The source and switch tube Q 2 The drain of switch S 1 The drain of the switch tube Q 1 The drain of the switch S 2 The source is connected to Q 2 The source of the rectifier circuit serves as the negative output terminal of the input rectifier circuit.

[0038] The LLC resonant converter circuit 1002 adopts a full-bridge LLC topology, including an input capacitor C in , multiplexed switch tube Q 1 And the switch tube Q 2 , switch tube Q 3 , switch tube Q 4 , resonant capacitor C r and resonant inductor L r , transformer T 1 The primary winding N p and the secondary winding N s . Input capacitor C in The positive end of the input rectifier circuit is connected to the positive output end and the switch tube Q 1 And the switch tube Q 3 The drain of the LLC resonant converter circuit 1002 is used as the positive input terminal; the input capacitor C in The negative end of the input rectifier circuit 1001 is connected to the negative output end and the switch tube Q 2 And the switch tube Q 4 The source of the switch tube Q is connected to ground and serves as the negative input terminal of the LLC resonant converter circuit 1002; 1 The source of the switch tube Q 2 The drain and resonant capacitor C r One end of the switch tube Q 3 The source of the switch tube Q 4 The drain and the transformer primary winding N p The opposite end of the resonant capacitor C r The other end is connected to the resonant inductor L r One end of the resonant inductor L r The other end is connected to the primary winding N of the transformer p The same-name end of the transformer secondary winding Ns The same-name end of the transformer secondary winding Ns serves as the positive output end of the LLC converter, and the opposite-name end of the transformer secondary winding Ns serves as the negative output end of the LLC converter.

[0039] It is worth noting that the resonant capacitor C r , resonant inductor L r , transformer T 1 Primary winding N p The order of series connection can be reversed.

[0040] The output rectifier circuit 1003 may adopt a conventional full-bridge rectifier circuit, or may adopt an output rectifier circuit such as a voltage doubler rectifier or a full-wave rectifier.

[0041] The equivalent circuits of the five working modes of the present invention are as follows: Figure 5 As shown, the key waveforms of the switching cycles in different modes are as follows Figure 6 As shown. The normalized instantaneous voltage gain of the LLC resonant converter in full-bridge mode is defined as M LLC , transformer T 1 The turns ratio is n = N p :N s . Combined Figure 5 and Figure 6 , the following will introduce these five working modes in detail:

[0042] 1) Mode I Figure 5 (a) shows: the switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The switch tube Q 3 , switch tube Q 4 The input rectifier circuit 101 is composed of a switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The LLC converter 102 is composed of a bridge rectifier circuit, and the LLC converter 102 is composed of a switch tube Q 3 , switch tube Q 4 The half-bridge LLC circuit is composed of a resonant cavity circuit. Among them, the high-frequency tube has a fixed duty cycle of D = 0.5, such as Figure 6 (a). Its equivalent voltage gain is M LLC / 2n.

[0043] 2) Mode II Figure 5 (b) shows: the switch tube S 1 , switch tube S 2 The switch tube Q 1, switch tube Q 2 , switch tube Q 3 , switch tube Q 4 The input rectifier circuit 101 is composed of a switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The LLC converter 102 is composed of a totem pole rectifier circuit, wherein the switch tube Q 1 , switch tube Q 2 , switch tube Q 3 , switch tube Q 4 The full-bridge LLC circuit is composed of a resonant cavity circuit. Among them, the control strategy adopts a frequency doubling method, and the high-frequency tube has a fixed duty cycle of D = 0.25. Figure 6 (b) is shown. Its equivalent voltage gain is 2M LLC / 3n.

[0044] 3) Mode III Figure 5 (c) shows: the switch tube S 1 , switch tube S 2 The switch tube Q 1 , switch tube Q 2 The switch tube Q performs high frequency switching during the power frequency cycle. 3 , switch tube Q 4 The input rectifier circuit 101 is composed of a switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The LLC converter 102 is composed of a totem pole rectifier circuit, wherein the switch tube Q 1 , switch tube Q 2 The half-bridge LLC circuit is composed of a resonant cavity circuit. Among them, the high-frequency tube has a fixed duty cycle of D = 0.5, such as Figure 6 (c) is shown. Its equivalent voltage gain is M LLC / n.

[0045] 4) Mode IV Figure 5 (d) shows: the switch tube S 1 , switch tube S 2 The switch tube Q performs high frequency switching during the power frequency cycle. 1 , switch tube Q 2 The switch tube Q 3 , switch tube Q 4 The input rectifier circuit 101 is composed of a switch tube S 1, switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The LLC converter 102 is composed of a totem pole rectifier circuit, wherein the switch tube Q 3 , switch tube Q 4 The half-bridge LLC circuit is composed of a resonant cavity circuit. 3 , Q 4 The duty cycle D can be changed with the input voltage to adjust the bus voltage v bus The amplitude and the equivalent input voltage v of the resonant cavity ab The waveform, such as Figure 6 (d) is shown. Its equivalent voltage gain is M LLC / [2n(1-D)].

[0046] 5) Mode V Figure 5 (b) shows: the switch tube S 1 , switch tube S 2 , switch tube Q 1 , switch tube Q 2 , switch tube Q 3 , switch tube Q 4 The working state is the same as that of mode II. The input rectifier circuit 101 is composed of a switch tube S 1 , switch tube S 2 , switch tube Q 1 And the switch tube Q 2 The LLC converter 102 is composed of a totem pole rectifier circuit, wherein the switch tube Q 1 , switch tube Q 2 , switch tube Q 3 , switch tube Q 4 The full-bridge LLC circuit is composed of a resonant cavity circuit. Among them, the high-frequency tube duty cycle D can be changed with the input voltage, which is used to adjust the bus voltage v bus The amplitude and the equivalent input voltage v of the resonant cavity ab The waveform, such as Figure 6

[0047] (e) is shown. Its equivalent voltage gain is M LLC· sin(Dπ) / [2n(1-D)].

[0048] Based on the above construction ideas, the voltage gain characteristics of the topology in different modes of the present invention are shown in Table 1.

[0049] Table 1 Voltage gain characteristics in five modes

[0050]

[0051]

[0052] 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, feed-forward table and adder U c5 ;

[0053] The output current signal conditioning circuit K v1 Sample output voltage V o , the output current signal conditioning circuit K v1 The output signal terminal of the subtractor U c1 The input end of the subtractor U c1 The output signal is sent to the PI controller 1, and the PI controller 1 outputs the signal 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 an input terminal of the feedforward table; the output current signal conditioning circuit K i1 Sample output current I o , the output current signal conditioning circuit K i1 The output signal terminal of the subtractor U c2 The input end of the subtractor U c2 The output signal is sent to the PI controller 2, and the PI controller 2 outputs the signal to the other input end of the constant voltage / constant current selector; the constant voltage / constant current selector selects the output signal of the PI controller 1 or the output signal of the PI controller 2 as needed; the input voltage signal conditioning circuit K v2 Sample input voltage v ac , the input voltage signal conditioning circuit K v2 The output signal end is connected to the input end of the phase-locked loop PLL; the input voltage signal conditioning circuit K v2 The output signal of the PLL is sent to the duty cycle adjustment module through the effective value calculation unit to obtain the high-frequency tube duty cycle D; the output of the phase-locked loop PLL obtains the input voltage phase θ and sends it to the |sin(θ)| calculation unit; the input voltage phase θ is sent to an input end of the feedforward table; the obtained |sin(θ)| signal and the output signal of the PI controller 1 or PI controller 2 are multiplied by the multiplier U c3 Multiply by to get the input current reference signal i ac_ref ; The input current signal conditioning circuit K i2Sampling input current i ac , transmitted to the subtractor U through the output signal terminal c4 , multiplier U c3 Output signal to subtractor U c4 ; Subtractor U c4 The output signal is sent to the PI controller 3; the output signal of the feedforward table and the PI controller 3 is sent to the adder U c5 , through adder U c5 After processing, the output signal is sent to the driver.

[0054] The controller 101 is used to implement a novel multi-mode AC-DC LLC resonant converter circuit 100 for wide voltage applications with constant output and power factor correction control. The control principle is as follows: the sampled output voltage V o Send to signal conditioning circuit K v1 , the conditioned signal and the reference voltage V o_ref Subtractor U c1 Get the error signal e v1 , and sent to PI controller 1 to achieve constant output voltage. Sampled output current I o Send to signal conditioning circuit K i1 , the conditioned signal and the reference voltage I o_ref Subtractor U c2 Get the error signal e i1 , and sent to PI controller 2 to achieve constant output current. Sample input voltage v ac Send to signal conditioning circuit K v2 The conditioned signal passes through the phase-locked loop PLL to obtain the input voltage phase θ. The |sin(θ)| signal obtained by the calculation unit and the output signal of PI controller 1 or PI controller 2 are multiplied by the multiplier U c3 Multiply by to get the input current reference signal i ac_ref . Sample input current i ac Send to signal conditioning circuit K i2 , the conditioned signal and the input current reference signal i ac_ref Subtractor U c4 Get the error signal e i2 , and sent to the PI controller 3 for input current waveform tracking control. In order to improve the input current waveform tracking effect and reduce the input current harmonics, feedforward control is usually introduced. The pre-designed feedforward table and the output signal of the PI controller 3 are sent to the adder U c5 Add the control signal e c1 The feedforward table can be obtained by fitting according to the switching frequency conversion law. It can be understood that the controller 101 can be implemented by a digital controller or an analog circuit.

[0055] refer to Figure 4 The present invention is a novel multi-mode AC-DC LLC resonant converter suitable for wide output voltage. The specific implementation mode switching flow chart is shown in FIG. Taking the 100-420V output voltage of electric vehicle charging as an example, the regions are divided into I, II, and III. Among them, region I is V o =100V-170V, Region II is V o =150V-270V, Region I is V o =250V-420V. The setting of the switching point needs to consider two aspects: 1) the magnitude of the output voltage. According to the output voltage, the appropriate working mode is selected, and the hysteresis comparison is used to avoid the oscillation problem during the switching process. The specific switching point comparison values ​​are V th1d =150V, V th1u =170V, V th2d =250V and V th2u =270V. 2) Selection of the starting point of the input voltage. In order to reduce the impact of the switching process on the input current waveform, the present invention uses the zero-crossing point (θ=0 or π) of the AC input voltage detected by the phase-locked loop PLL as the switching starting point. At this time, the input power is almost zero, and the switching frequency of the converter is predictable. In modes IV and V, the switching frequency near the zero-crossing point is almost equal to the minimum frequency. For mode II, due to the use of frequency doubling technology, the switching frequency can be predicted in advance to be half of the minimum frequency, thereby reducing the impact of frequency mutations on the input current waveform and achieving smooth conversion between adjacent modes.

[0056] The present invention combines the totem pole circuit / bridge rectifier circuit with the LLC topology, and switches the topology between single-stage / quasi-single-stage / two-stage modes by changing the switch bridge arm control logic. Different mode combinations can be selected for different voltage gain ranges to effectively change the equivalent AC input voltage amplitude of the AC-DC LLC resonant converter, thereby significantly widening the voltage gain range of the topology. At the same time, a unified power factor correction control strategy is adopted under different working modes, and finally the single-stage AC-DC LLC resonant converter is realized under a wide output voltage with high efficiency and high power factor power conversion.

[0057] The above shows and describes 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 by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A multi-mode AC-DC LLC resonant converter topology, characterized in that: The invention comprises an input rectifier circuit, an LLC resonant converter circuit and an output rectifier circuit. The positive output terminal of the input rectifier circuit is connected to the positive input terminal of the LLC resonant converter circuit, and the negative output terminal thereof is connected to the negative input terminal of the LLC resonant converter circuit and connected to the input ground; one end of the output side of the LLC resonant converter circuit is connected to an input terminal of the output rectifier circuit, and the other output terminal thereof 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 o The positive terminal is connected to the output load battery R o The other end of the output rectifier circuit is connected to the negative end of the output capacitor and connected to the output load battery R o The negative terminal.

2. A multi-mode AC-DC LLC resonant converter topology according to claim 1, characterized in that: The input rectifier circuit includes an input inductor L b , switch tube S1, switch tube S2, switch tube Q1 and switch tube Q2, input inductor L b One end is connected to the AC source v ac One end of the input inductor L b The other end is connected to the source of switch tube S1 and the drain of S2, and the AC source v ac The other end is connected to the source of the switch tube Q1 and the drain of Q2; the drain of the switch S1 is connected to the drain of Q1 and serves as the positive output end of the input rectifier circuit, and the source of the switch S2 is connected to the source of Q2 and serves as the negative output end of the input rectifier circuit.

3. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 1, characterized in that: The LLC resonant converter circuit adopts a full-bridge LLC topology, including input capacitor C in , multiplexed switch tube Q1 and switch tube Q2, switch tube Q3, switch tube Q4, resonant capacitor C r and resonant inductor L r , the primary winding N of transformer T1 p and the secondary winding N s ; Input capacitance C in The positive end of the input rectifier circuit is connected to the positive output end and the drain of the switch tube Q1 and the switch tube Q3, serving as the positive input end of the LLC resonant converter circuit; the input capacitor C in The negative end of the switch Q1 is connected to the negative output end of the input rectifier circuit and the source of the switch tube Q2 and the switch tube Q4 and is grounded, serving as the negative input end of the LLC resonant converter circuit; the source of the switch tube Q1 is connected to the drain of the switch tube Q2 and the resonant capacitor C r The source of the switch tube Q3 is connected to the drain of the switch tube Q4 and the primary winding N of the transformer. p The opposite end of the resonant capacitor C r The other end is connected to the resonant inductor L r One end of the resonant inductor L r The other end is connected to the primary winding N of the transformer p The same-name terminal of the transformer secondary winding N s The same-name end of the transformer secondary winding Ns serves as the positive output end of the LLC converter, and the opposite-name end of the transformer secondary winding Ns serves as the negative output end of the LLC converter.

4. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 3, characterized in that: The resonant capacitor C r , resonant inductor L r , transformer T1 primary winding N p The order of series connection can be reversed.

5. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 1, characterized in that: The output rectification circuit adopts a full-bridge rectification circuit, a voltage doubler rectification circuit or a full-wave rectification circuit.

6. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 1, characterized in that: Also includes a controller, the controller 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, feed-forward table and adder U c5 .

7. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 6, characterized in that: The output current signal conditioning circuit K v1 Sample output voltage V o , one of its output signal terminals is connected to the subtractor U c1 The input end of the subtractor U c1 The output signal end of the PI controller 1 is connected to the input end of the PI controller 1, and the output signal end of the PI controller 1 is connected to an input end of the constant voltage / constant current selector, and the output voltage signal conditioning circuit K v1 The other output signal terminal is connected to an input terminal of the feedforward table; The output current signal conditioning circuit K i1 Sample output current I o , its output signal end is connected to the subtractor U c2 The input end of the subtractor U c2 The output signal end of is connected to the input end of PI controller 2, and the output signal end of PI controller 2 is connected to another input end 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 as needed.

8. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 6, characterized in that: The input voltage signal conditioning circuit K v2 Sample input voltage v ac , whose output signal end is connected to the input end of the phase-locked loop PLL; the input voltage signal conditioning circuit K v2 The output signal of the PLL is sent to the duty cycle adjustment module through the effective value calculation unit to obtain the high-frequency tube duty cycle D; the output of the phase-locked loop PLL obtains the input voltage phase θ and sends it to the |sin(θ)| calculation unit; the input voltage phase θ is sent to an input end of the feedforward table; the obtained |sin(θ)| signal and the output signal of the PI controller 1 or PI controller 2 are multiplied by the multiplier U c3 Multiply by to get the input current reference signal i ac_ref .

9. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 6, characterized in that: The input current signal conditioning circuit K i2 Sampling input current i ac , its output signal end is connected to the subtractor U c4 The input of the multiplier U c3 Output signal to subtractor U c4 , subtractor U c4 The output signal is sent to the PI controller 3; the output signal of the feedforward table and the PI controller 3 is sent to the adder U c5 , through adder U c5 After processing, the output signal is sent to the driver.

10. A control strategy for a multi-mode AC-DC LLC resonant converter topology according to any one of claims 1 to 9, characterized in that: According to the magnitude of the output voltage amplitude, the zero-crossing point of the AC input voltage detected by the phase-locked loop PLL is used as the switching starting point, and the switching tubes S1, S2, Q1, Q2, and Q 3、 The working state of the switch tube Q4 realizes the switching of five working modes, among which the five working modes are: Mode I: the switch tubes S1, S2, Q1 and Q2 act as power frequency synchronous rectification switches in the power frequency cycle, and the switch tubes Q3 and Q4 act as high frequency switches in the power frequency cycle; at this time, the input rectification circuit 101 is a bridge rectification circuit composed of the switch tubes S1, S2, Q1 and Q2, the LLC converter 102 is a half-bridge LLC circuit composed of the switch tubes Q3, Q4 and a resonant cavity circuit, and the high frequency tube has a fixed duty cycle D=0.5; Mode II: the switch tubes S1 and S2 act as synchronous rectifier switches in the power frequency cycle, and the switch tubes Q1, Q2, Q3, and Q4 act as high-frequency switches in the power frequency cycle; at this time, the input rectifier circuit 101 is a totem pole rectifier circuit composed of the switch tubes S1, S2, Q1, and Q2, and the LLC converter 102 is a full-bridge LLC circuit composed of the switch tubes Q1, Q2, Q3, Q4, and a resonant cavity circuit; wherein the control strategy adopts a frequency doubling method, and the high-frequency tube has a fixed duty cycle D=0.25; Mode III: the switch tubes S1 and S2 act as power frequency synchronous rectification switches in the power frequency cycle, the switch tubes Q1 and Q2 act as high frequency switches in the power frequency cycle, and the switch tubes Q3 and Q4 act as power frequency synchronous rectification switches in the power frequency cycle; at this time, the input rectification circuit 101 is a totem pole rectification circuit composed of the switch tubes S1, S2, Q1 and Q2, and the LLC converter 102 is a half-bridge LLC circuit composed of the switch tubes Q1, Q2 and a resonant cavity circuit; wherein the high frequency tube has a fixed duty cycle D=0.5; Mode IV: the switch tubes S1 and S2 act as high-frequency switches in the power frequency cycle, the switch tubes Q1 and Q2 act as power frequency synchronous rectification switches in the power frequency cycle, and the switch tubes Q3 and Q4 act as high-frequency switches in the power frequency cycle; at this time, the input rectifier circuit 101 is a totem pole rectifier circuit composed of the switch tubes S1, S2, Q1 and Q2, and the LLC converter 102 is a half-bridge LLC circuit composed of the switch tubes Q3, Q4 and a resonant cavity circuit; wherein the duty cycle D of the high-frequency tubes Q3 and Q4 can change with the input voltage, and is used to adjust the bus voltage v bus The amplitude and the equivalent input voltage v of the resonant cavity ab The waveform of Mode V: The working states of the switch tube S1, the switch tube S2, the switch tube Q1, the switch tube Q2, the switch tube Q3, and the switch tube Q4 are the same as those in mode II; at this time, the input rectifier circuit 101 is a totem pole rectifier circuit composed of the switch tube S1, the switch tube S2, the switch tube Q1, and the switch tube Q2, and the LLC converter 102 is a full-bridge LLC circuit composed of the switch tube Q1, the switch tube Q2, the switch tube Q3, the switch tube Q4 and the resonant cavity circuit; wherein the high-frequency tube duty cycle D can be changed with the input voltage, and is used to adjust the bus voltage v bus The amplitude and the equivalent input voltage v of the resonant cavity ab waveform.

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