A multi-mode ac-dc llc resonant converter topology and control strategy thereof

Abstract

This invention discloses a multi-mode AC-DC LLC resonant converter topology and its control strategy. The 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 its negative output terminal is connected to the negative input terminal of the LLC resonant converter circuit and grounded. One end of the output side of the LLC resonant converter circuit is connected to one input terminal of the output rectifier circuit, 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. o Connect the positive terminal to the output load battery R. o The positive terminal of the output rectifier circuit is connected to the negative terminal of the output capacitor, and then connected to the output load battery R. o The negative terminal. This invention 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.

Description

Technical Field

[0001] This invention relates to the field of switching power supply technology, specifically a multi-mode AC-DC LLC resonant converter topology and its control strategy. Background Technology

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

[0003] Traditional on-board chargers typically employ a two-stage architecture. The front stage acts as a PFC (Power Factor Correction) unit to achieve AC-DC conversion, while the rear stage uses 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 rear stage. Because both the front and rear stages require independent active and passive power devices, and high-voltage, high-capacity electrolytic capacitors need to be connected in parallel between them, this two-stage system design results in high cost, large size, and low reliability, making it increasingly difficult to meet the demands of commercial applications.

[0004] Single-stage AC-DC PFC converters, with their advantages of low cost, high efficiency, and high power density, are considered a viable solution and have attracted attention. Single-stage LLC resonant converters, with their high efficiency, low cost, and simple control, are used in medium-to-high power AC-DC conversion applications. A typical topology is shown below. Figure 1 As shown. However, due to the PFM (Pulse Frequency Modulation) control used in traditional single-stage AC-DC LLC topologies, their output voltage gain range is limited. Sacrificing parameter optimization design to meet wide voltage gain requirements will reduce the overall efficiency of the converter under wide voltage variations. On the other hand, when considering the pre-charging requirements of electric vehicles, on-board chargers based on single-stage AC-DC LLC resonant converters are difficult to meet the application requirements of a wide voltage range of 100–420V. Therefore, how to expand the voltage gain of traditional single-stage AC-DC LLC topologies while maintaining high-efficiency power conversion is a highly challenging task. Summary of the Invention

[0005] The application aims to overcome the deficiencies of the prior art, and provides a multi-mode AC-DC LLC resonant converter topology and a control strategy thereof, which can effectively change the equivalent AC input voltage amplitude of the AC-DC LLC resonant converter, and further significantly widen the voltage gain range of the topology.

[0006] In order to achieve the above-mentioned purpose, the application specifically adopts the following technical solutions:

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

[0008] The input rectifier circuit comprises an input inductor L b , a switch tube S1, a switch tube S2, a switch tube Q1 and a switch tube Q2, one end of the input inductor L b is connected to one end of an AC source v ac , the other end of the input inductor L b is connected to the source electrode of the switch tube S1 and the drain electrode of the switch tube S2, the other end of the AC source v ac is connected to the source electrode of the switch tube Q1 and the drain electrode of the switch tube Q2. The drain electrode of the switch S1 is connected to the drain electrode of the switch Q1, and serves as the positive output end of the input rectifier circuit; the source electrode of the switch S2 is connected to the source electrode of the switch Q2, and serves as the negative output end of the input rectifier circuit.

[0009] The LLC resonant converter circuit adopts a full-bridge LLC topology, and comprises an input capacitor C in , multiplexed switch tubes Q1 and Q2, switch tubes Q3 and Q4, a resonant capacitor C r , a resonant inductor L r , a primary winding N p and a secondary winding N s of a transformer T1. The positive end of the input capacitor C in is connected to the positive output end of the input rectifier circuit and the drain electrodes of the switch tubes Q1 and Q3, and serves as the positive input end of the LLC resonant converter circuit; the negative end of the input capacitor C inThe negative end of the LLC resonant converter circuit 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. r The source of the switch tube Q3 is connected to the drain of the switch tube Q4 and the primary winding N p of the transformer, and the like end of the primary winding N r of the transformer is connected to the other end of the resonant capacitor C r The other end of the resonant inductor L r is connected to the like end of the primary winding N p of the transformer, and the like end of the secondary winding N s of the transformer is connected to the other end of the resonant inductor L r , the other end of the resonant capacitor C r , and the like end of the primary winding N p of the transformer.

[0010] As a preferred embodiment, the output rectifier circuit is a full-bridge rectifier circuit, and can also be a voltage doubler rectifier, a full-wave rectifier, or the like.

[0011] The multi-mode AC-DC LLC resonant converter topology of the present application further comprises a controller, which comprises an output current signal conditioning circuit K i1 , an input current signal conditioning circuit K i2 , an output voltage signal conditioning circuit K v1 , an input voltage signal conditioning circuit K v2 , a subtracter U c1 , a subtracter U c2 , a subtracter U c4 , a PI controller 1, a PI controller 2, a PI controller 3, a multiplier U c3 , a phase-locked loop PLL, a feedforward table, and an adder U c5 .

[0012] The output current signal conditioning circuit K v1 samples the output voltage V o , and one output signal end is connected to the input end of the subtracter U c1 , and the output signal end of the subtracter U c1 is connected to the input end of the PI controller 1, the output signal end of the PI controller 1 is connected to one input end of the constant voltage / constant current selector, and the other output signal end of the output voltage signal conditioning circuit K v1 is connected to one input end of the feedforward table.

[0013] The output current signal conditioning circuit K i1The sampling output current I o The output signal end of the sampling output current I c2 is connected with the input end of the subtracter U c2 , the output signal end of the subtracter U v2 is connected with the input end of the PI controller 2, the output signal end of the PI controller 2 is connected with the other input end of the constant voltage / constant current selector, and the constant voltage / constant current selector selects the output signal of the PI controller 1 or the output signal of the PI controller 2 according to the requirement.

[0014] The input voltage signal conditioning circuit K ac The sampling input voltage v v2 is connected with the input end of the phase-locked loop PLL, the output signal of the input voltage signal conditioning circuit K c3 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 is sent to the |sin(θ)| calculation unit, the input voltage phase θ is sent to one input end of the feedforward table, the obtained |sin(θ)| signal is multiplied with the output signal of the PI controller 1 or the PI controller 2 through the multiplier U ac_ref .

[0015] The input current signal conditioning circuit K i2 The sampling input current i ac is connected with the input end of the subtracter U c4 , the output signal of the multiplier U c3 is sent to the subtracter U c4 , the output signal of the subtracter U c4 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 , and the output signal after the processing of the adder U c5 is sent to the driver.

[0016] The application also provides a control strategy of the multi-mode AC-DC LLC resonant converter topology, which selects the appropriate working mode according to the size of the output voltage amplitude, and adopts the hysteresis comparison to avoid the oscillation problem in the switching process; in order to reduce the influence of the switching process on the input current waveform, the zero-crossing point (θ=0 or π) of the alternating input voltage detected by the phase-locked loop PLL is taken as the switching starting point, at this time, the input power is almost zero, and the switching frequency of the converter is predictable: in the mode IV and V, the switching frequency near the zero-crossing point is almost equal to the minimum frequency; for the mode II, since the frequency doubling technology is used, the switching frequency can be predicted as half of the minimum frequency in advance, so as to reduce the influence of the frequency mutation on the input current waveform and realize the smooth conversion between the adjacent modes.

[0017] Specifically, the control strategy switches five working modes by changing 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 according to the size of the output voltage amplitude, and then selects a suitable working mode.

[0018] The five working modes are as follows.

[0019] Mode I: The switch tube S1, the switch tube S2, the switch tube Q1 and the switch tube Q2 are high-frequency synchronous rectification switches in a working frequency cycle, and the switch tube Q3 and the switch tube Q4 are high-frequency switches in the working frequency cycle; at this time, the input rectifier circuit 101 is a bridge rectifier circuit composed of the switch tube S1, the switch tube S2, the switch tube Q1 and the switch tube Q2, the LLC converter 102 is a half-bridge LLC circuit composed of the switch tube Q3, the switch tube Q4 and the resonant cavity circuit, and the high-frequency tube fixed duty ratio D=0.5.

[0020] Mode II: The switch tube S1 and the switch tube S2 are synchronous rectification switches in a working frequency cycle, and the switch tube Q1, the switch tube Q2, the switch tube Q3 and the switch tube Q4 are high-frequency switches in the working frequency cycle; 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 and the switch tube Q4 and the resonant cavity circuit; wherein the control strategy adopts a frequency doubling mode, and the high-frequency tube fixed duty ratio D=0.25.

[0021] Mode III: The switch tube S1 and the switch tube S2 are high-frequency synchronous rectification switches in a working frequency cycle, the switch tube Q1 and the switch tube Q2 are high-frequency switches in the working frequency cycle, and the switch tube Q3 and the switch tube Q4 are high-frequency synchronous rectification switches in the working frequency cycle; 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 half-bridge LLC circuit composed of the switch tube Q1, the switch tube Q2 and the resonant cavity circuit; wherein the high-frequency tube fixed duty ratio D=0.5.

[0022] Mode IV: The switch tube S1 and the switch tube S2 are high-frequency switches in a working frequency cycle, the switch tube Q1 and the switch tube Q2 are high-frequency synchronous rectification switches in the working frequency cycle, and the switch tube Q3 and the switch tube Q4 are high-frequency switches in the working frequency cycle; 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 half-bridge LLC circuit composed of the switch tube Q3, the switch tube Q4 and the resonant cavity circuit; wherein the high-frequency tube Q3 and the high-frequency tube Q4 duty ratio D can change with the input voltage, and are used to adjust the bus voltage vbus the amplitude of the equivalent input voltage v ab the waveform of the equivalent input voltage v

[0023] 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 change of the input voltage, for adjusting the bus voltage v bus the amplitude of the equivalent input voltage v ab the waveform of the equivalent input voltage v

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

[0025] By changing the control logic of the switch bridge arms S1-S2 and 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 different output voltages, so as to effectively change the equivalent AC input voltage amplitude of the AC-DC LLC resonant converter, and further significantly widen the voltage gain range of the topology, while improving the conversion efficiency of the single-stage AC-DC LLC resonant converter. BRIEF DESCRIPTION OF DRAWINGS

[0026] Other characteristics, objects and advantages of the application will become more apparent by reading the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

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

[0028] Figure 2 It is a circuit diagram of a new multi-mode AC-DC LLC resonant converter suitable for wide voltage applications according to an embodiment of the application;

[0029] Figure 3 It is a controller circuit diagram of a new multi-mode AC-DC LLC resonant converter suitable for wide voltage applications according to an embodiment of the application;

[0030] Figure 4 It is a mode switching flowchart of a new multi-mode AC-DC LLC resonant converter suitable for wide voltage applications according to an embodiment of the application;

[0031] Figure 5An equivalent circuit 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 application;

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

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

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

[0035] The present application will be described in detail below with specific embodiments. The following embodiments will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

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

[0037] The input rectifier circuit 1001 includes an input inductor L b , a switch tube S1, a switch tube S2, a switch tube Q1 and a switch tube Q2. One end of the input inductor L b is connected to one end of the alternating current source v ac , and the other end of the input inductor L b is connected to the source of the switch tube S1 and the drain of the switch tube S2. The alternating current source vac The other end of switch S1 is connected to the source of switch Q1 and the drain of switch Q2. The drain of switch S1 is connected to the drain of switch Q1 and serves as the positive output terminal of the input rectifier circuit. The source of switch S2 is connected to the source of Q2 and 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 input capacitor C. in Multiplexed switching transistors Q1, Q2, Q3, and Q4, and resonant capacitor C. r and resonant inductance L r The primary winding N of transformer T1 p and secondary winding N s Input capacitor C in The positive terminal is connected to the positive output terminal of the input rectifier circuit and the drain of switching transistors Q1 and Q3, serving as the positive input terminal of the LLC resonant converter circuit 1002; the input capacitor C in The negative terminal of the input rectifier circuit 1001 is connected to the negative output terminal of the input rectifier circuit 1001, as well as the source of the switching transistors Q2 and Q4, and grounded, serving as the negative input terminal of the LLC resonant converter circuit 1002; the source of the switching transistor Q1 is connected to the drain of the switching transistor Q2 and the resonant capacitor C. r At one end, the source of switching transistor Q3 is connected to the drain of switching transistor Q4 and the primary winding N of the transformer. p The opposite terminal. Resonant capacitor C r The other end is connected to the resonant inductor L r One end, resonant inductor L r The other end is connected to the primary winding N of the transformer. p The same terminal. Transformer secondary winding N s The terminal with the same name as the transformer secondary winding Ns is used as the positive output terminal of the LLC converter, and the terminal with the opposite name as the negative output terminal of the LLC converter.

[0039] It is worth noting that the resonant capacitor C r Resonant inductor L r Transformer T1 primary winding N p The sequence order can be changed.

[0040] The output rectifier circuit 1003 can be a traditional full-bridge rectifier circuit, or it can be a voltage doubler rectifier, full-wave rectifier, or other output rectifier circuits.

[0041] The equivalent circuits for the five operating modes of this invention are as follows: Figure 5 As shown, the key waveforms of the switching cycle 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 The turns ratio of transformer T1 is n = N pN s . In combination Figure 5 and Figure 6 , the following will be described in detail the five working modes:

[0042] 1) Mode I as shown in Figure 5 (a): the switch S1, switch S2, switch Q1 and switch Q2 in the power frequency cycle as power frequency synchronous rectification switch, the switch Q3, switch Q4 in the power frequency cycle as high frequency switch. Among them, the input rectifier circuit 101 is composed of switch S1, switch S2, switch Q1 and switch Q2 bridge rectifier circuit, LLC converter 102 is composed of switch Q3, switch Q4 and resonant cavity circuit half bridge LLC circuit. Among them, the high frequency tube fixed duty ratio D = 0.5, as shown in Figure 6 (a). Its equivalent voltage gain is M LLC / 2n.

[0043] 2) mode II as shown in Figure 5 (b): the switch S1, switch S2 in the power frequency cycle as synchronous rectification switch, the switch Q1, switch Q2, switch Q3, switch Q4 in the power frequency cycle as high frequency switch. Among them, the input rectifier circuit 101 is composed of switch S1, switch S2, switch Q1 and switch Q2 totem pole rectifier circuit, LLC converter 102 is composed of switch Q1, switch Q2, switch Q3, switch Q4 and resonant cavity circuit full bridge LLC circuit. Among them, the control strategy adopts frequency doubling way, high frequency tube fixed duty ratio D = 0.25, as shown in Figure 6 (b). Its equivalent voltage gain is 2M LLC / 3n.

[0044] 3) mode III as shown in Figure 5 (c): the switch S1, switch S2 in the power frequency cycle as power frequency synchronous rectification switch, the switch Q1, switch Q2 in the power frequency cycle as high frequency switch, the switch Q3, switch Q4 in the power frequency cycle as power frequency synchronous rectification switch. Among them, the input rectifier circuit 101 is composed of switch S1, switch S2, switch Q1 and switch Q2 totem pole rectifier circuit, LLC converter 102 is composed of switch Q1, switch Q2 and resonant cavity circuit half bridge LLC circuit. Among them, the high frequency tube fixed duty ratio D = 0.5, as shown in Figure 6 (c). Its equivalent voltage gain is M LLC / n.

[0045] 4) mode IV as shown in Figure 5(d) as shown: the switch S1, switch S2 in the power frequency cycle for high frequency switch, the switch Q1, switch Q2 in the power frequency cycle for power frequency synchronous rectifier switch, the switch Q3, switch Q4 in the power frequency cycle for high frequency switch. Wherein the input rectifier circuit 101 is by switch S1, switch S2, switch Q1 and switch Q2 composed of totem pole rectifier circuit, LLC converter 102 is by switch Q3, switch Q4 and resonant cavity circuit composed of half bridge LLC circuit. Wherein, the high frequency tube Q3, Q4 duty ratio D with input voltage change can change, for adjusting bus voltage v bus The amplitude and the waveform of the equivalent input voltage v ab Of the resonant cavity, as shown in Figure 6 (d). Its equivalent voltage gain is M LLC Sin(Dπ) / [2n(1-D)].

[0046] 5) mode V as shown in Figure 4 (b) : the switch S1, switch S2, switch Q1, switch Q2, switch Q3, switch Q4 work state is same with mode II. Wherein the input rectifier circuit 101 is by switch S1, switch S2, switch Q1 and switch Q2 composed of totem pole rectifier circuit, LLC converter 102 is by switch Q1, switch Q2, switch Q3, switch Q4 and resonant cavity circuit composed of full bridge LLC circuit. Wherein, the high frequency tube duty ratio D with input voltage change can change, for adjusting bus voltage v bus The amplitude and the waveform of the equivalent input voltage v ab Of the resonant cavity, as shown in ​

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

[0048] Based on the above construction idea, the voltage gain characteristics of the topology in different modes of the application are shown in table 1.

[0049] Table 1 voltage gain characteristics in five modes

[0050]

[0051]

[0052] The controller 101, including 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 , subtracter 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 table and adder U c5 ;

[0053] the output current signal conditioning circuit K v1 samples the output voltage V o , the output signal end of the output current signal conditioning circuit K v1 is connected with the input end of subtractor U c1 , subtractor U c1 outputs a signal to PI controller 1, and PI controller 1 outputs a signal to one input end of the constant-voltage / constant-current selector; another output signal end of the output voltage signal conditioning circuit K v1 is connected with one input end of the feedforward table; the output current signal conditioning circuit K i1 samples the output current I o , the output signal end of the output current signal conditioning circuit K i1 is connected with the input end of subtractor U c2 , subtractor U c2 outputs a signal to PI controller 2, and PI controller 2 outputs a signal 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 according to the requirement; the input voltage signal conditioning circuit K v2 samples the input voltage V ac , and the output signal end of the input voltage signal conditioning circuit K v2 is connected with the input end of the phase-locked loop PLL; the output signal of the input voltage signal conditioning circuit K v2 is sent to the duty cycle adjustment module through the effective value calculation unit, and the high-frequency tube duty cycle D is obtained; the output of the phase-locked loop PLL obtains the input voltage phase θ and is sent to the |sin(θ)| calculation unit; the input voltage phase θ is sent to one input end of the feedforward table; the obtained |sin(θ)| signal is multiplied with the output signal of PI controller 1 or PI controller 2 through multiplier U c3 , and the input current reference signal i ac_ref is obtained; the input current signal conditioning circuit K i2 samples the input current i ac , and the output signal end sends the signal to subtractor U c4 ; multiplier U c3 outputs a signal to subtractor U c4 ; subtractor U c4 outputs a signal to PI controller 3; the output signal of the feedforward table and PI controller 3 is sent to adder U c5, the processed signal and the reference voltage V c5 The processed signal is output to the driver.

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

[0055] Reference ​ A new multi-mode AC-DC LLC resonant converter specific embodiment mode switching flow chart suitable for wide output voltage is shown in the figure. Taking the 100-420V output voltage of the electric vehicle charging as an example, the region I, II and III are divided. 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 switching points needs to consider two aspects: 1) the output voltage amplitude. According to the output voltage, the appropriate working mode is preferred, and the hysteresis comparison is used to avoid the oscillation problem in the switching process. The specific switching point comparison values are V th1d = 150V, V th1u = 170V, V th2d = 250V, and V th2u = 270V. 2) The selection of the input voltage starting point. In order to reduce the impact of the switching process on the input current waveform, the application takes 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 mutation on the input current waveform and achieving smooth transition between adjacent modes.

[0056] The application combines totem pole circuit / bridge rectifier circuit and LLC topology, and changes the switching bridge arm control logic, so that the topology switches between single-stage / quasi-single-stage / two-stage modes. Different mode combinations can be selected for different voltage gain ranges, 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. At the same time, a unified power factor correction control strategy is used in different working modes, and finally a single-stage AC-DC LLC resonant converter with high efficiency and high power factor power conversion under wide output voltage is realized.

[0057] The basic principles, main features and advantages of the application are shown and described above. Those skilled in the art should understand that the application is not limited by the above examples, and the above examples and descriptions in the specification are only preferred examples of the application and are not intended to limit the application. Without departing from the spirit and scope of the application, various changes and improvements can be made to the application, and these changes and improvements all fall within the scope of the claimed application. The scope of protection of the application is defined by the appended claims and their equivalents.

Claims

1. A multi-mode AC-DC LLC resonant converter topology, characterized by: The input rectifier circuit, LLC resonant converter circuit and output rectifier circuit are included, the positive output end of the input rectifier circuit is connected with the positive input end of the LLC resonant converter circuit, and the negative output end of the input rectifier circuit is connected with the negative input end of the LLC resonant converter circuit and the input ground; One end of the output side of the LLC resonant converter circuit is connected to one 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 the positive terminal of the output capacitor C o , and to the positive terminal of the output load battery R o ; the other terminal of the output rectifier circuit is connected to the negative terminal of the output capacitor, and to the negative terminal of the output load battery R o , The input rectifier circuit includes the switch S1, the switch S2, the switch Q1 and the switch Q2, the drain of the switch S1 is connected with the drain of the switch Q1 and serves as the positive output end of the input rectifier circuit, and the source of the switch S2 is connected with the source of the switch Q2 and serves as the negative output end of the input rectifier circuit; The LLC resonant converter circuit adopts a full-bridge LLC topology, comprising an input capacitor C in , a multiplexed switch tube Q1 and a switch tube Q2, a switch tube Q3, and a switch tube Q4 in The positive end of the input capacitor C is connected to the positive output end of the input rectifier circuit 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 in The negative end of the input capacitor C 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 grounded, serving as the negative input end of the LLC resonant converter circuit Also included is a controller comprising an output current signal conditioning circuit K i1 , an input current signal conditioning circuit K i2 , an output voltage signal conditioning circuit K v1 , an input voltage signal conditioning circuit K v2 , a subtractor U c1 , a subtractor U c2 , a subtractor U c4 , a PI controller 1, a PI controller 2, a PI controller 3, a multiplier U c3 , a phase locked loop PLL, a feed forward table and an adder U c5 , The output voltage signal conditioning circuit K v1 The sampling output voltage V o One output signal terminal of which is connected to the input terminal of subtractor U c1 The output signal terminal of subtractor U c1 is connected to the input terminal of PI controller 1, the output signal terminal of PI controller 1 is connected to one input terminal of constant voltage / constant current selector, and the other output signal terminal of output voltage signal conditioning circuit K v1 is connected to one input terminal of feedforward table; The output current signal conditioning circuit K i1 The sampling output current I o The output signal end of the output current signal conditioning circuit K is connected with the input end of the subtractor U c2 The output signal end of the subtractor U c2 is connected with the input end of the PI controller 2, and the output signal end of the PI controller 2 is connected with the other input end of the constant voltage / constant current selector, and the constant voltage / constant current selector selects the output signal of the PI controller 1 or the output signal of the PI controller 2 according to the requirement. The input voltage signal conditioning circuit K v2 The sampling input voltage v ac The output signal end is connected with the input end of the phase-locked loop PLL; the input voltage signal conditioning circuit K v2 The output signal is sent to the regulation duty cycle module through the effective value calculation unit, and the high frequency tube duty cycle D is obtained; the output of the phase-locked loop PLL obtains the input voltage phase θ, and is sent 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 is multiplied with the output signal of the PI controller 1 or the PI controller 2 through the multiplier U c3 , and the input current reference signal i ac_ref is obtained; 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 input terminals are 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 signal is then sent to the driver.

2. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 1, characterized in that: The input rectifier circuit further comprises an input inductor L b One end of the input inductor L b is connected to one end of an AC source v ac The other end of the input inductor L b is connected to the source of switch S1 and the drain of S2, and the other end of the AC source v ac is connected to the source of switch Q1 and the drain of Q2.

3. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 2, characterized in that: The LLC resonant converter circuit adopts a full-bridge LLC topology, and further comprises a resonant capacitor C r and a resonant inductor L r The primary winding N p and the secondary winding N s of the transformer T1 The source electrode of the switching transistor Q1 is connected to the drain electrode of the switching transistor Q2 and one end of the resonant capacitor C r The source electrode of the switching transistor Q3 is connected to the drain electrode of the switching transistor Q4 and the opposite end of the primary winding N p of the transformer; the other end of the resonant capacitor C r is connected to one end of the resonant inductor L r The other end of the resonant inductor L r is connected to the same end of the primary winding N p of the transformer; the same end of the secondary winding N s of the transformer is used as the positive output terminal of the LLC converter, and the opposite end of the secondary winding Ns of the transformer is used as the negative output terminal of the LLC converter.

4. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 3, characterized by: The resonance capacitor C r , resonance inductance L r , primary winding N p of the transformer T1 can be exchanged.

5. A multi-mode AC-DC LLC resonant converter topology as claimed in claim 3, characterized by: The output rectifier circuit adopts a full-bridge rectifier circuit, a voltage-doubler rectifier circuit or a full-wave rectifier circuit.

6. A control strategy for a multi-mode AC-DC LLC resonant converter topology as claimed in any of claims 3 to 5, characterized in that: According to the size of the output voltage amplitude, the zero-crossing point of the alternating input voltage detected by the phase-locked loop (PLL) is taken as the switching starting point, and the switching of the five working modes is realized by changing the working states of the switches S1, S2, Q1, Q2, Q3 and Q4, wherein the five working modes are as follows: Mode I: the switches S1, S2, Q1 and Q2 are working frequency synchronous rectifier switches in a working frequency cycle, and the switches Q3 and Q4 are high-frequency switches in the working frequency cycle; at this time, the input rectifier circuit 101 is a bridge rectifier circuit composed of the switches S1, S2, Q1 and Q2, the LLC converter 102 is a half-bridge LLC circuit composed of the switches Q3, Q4 and a resonant cavity circuit, and the high-frequency tube has a fixed duty ratio D=0.5; Mode II: the switches S1 and S2 are synchronous rectifier switches in a working frequency cycle, and the switches Q1, Q2, Q3 and Q4 are high-frequency switches in the working frequency cycle; at this time, the input rectifier circuit 101 is a totem-pole rectifier circuit composed of the switches S1, S2, Q1 and Q2, and the LLC converter 102 is a full-bridge LLC circuit composed of the switches Q1, Q2, Q3 and Q4 and a resonant cavity circuit; wherein the control strategy adopts a frequency-doubling mode, and the high-frequency tube has a fixed duty ratio D=0.25; Mode III: the switches S1 and S2 are working frequency synchronous rectifier switches in a working frequency cycle, the switches Q1 and Q2 are high-frequency switches in the working frequency cycle, and the switches Q3 and Q4 are working frequency synchronous rectifier switches in the working frequency cycle; at this time, the input rectifier circuit 101 is a totem-pole rectifier circuit composed of the switches S1, S2, Q1 and Q2, and the LLC converter 102 is a half-bridge LLC circuit composed of the switches Q1, Q2 and a resonant cavity circuit; wherein the high-frequency tube has a fixed duty ratio D=0.5; Mode IV: the switch S1, switch S2 in the power frequency cycle for high frequency switching, the switch Q1, switch Q2 in the power frequency cycle for power frequency synchronous rectification switch, the switch Q3, switch Q4 in the power frequency cycle for high frequency switching; at this time, the input rectifier circuit 101 is by switch S1, switch S2, switch Q1 and switch Q2 composed of totem pole rectifier circuit, LLC converter 102 is by switch Q3, switch Q4 and resonant cavity circuit composed of half bridge LLC circuit; wherein, high frequency tube Q3, Q4 duty ratio D can be changed with the input voltage changes, for adjusting the bus voltage v bus The amplitude and the waveform of the equivalent input voltage v ab Of the resonant cavity; Mode V: the working states of the switch S1, the switch S2, the switch Q1, the switch Q2, the switch Q3 and the switch 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 S1, the switch S2, the switch Q1 and the switch Q2, and the LLC converter 102 is a full-bridge LLC circuit composed of the switch Q1, the switch Q2, the switch Q3, the switch Q4 and the resonant cavity circuit; wherein the high-frequency tube duty cycle D can be changed with the input voltage, for adjusting the amplitude of the bus voltage v bus and the waveform of the resonant cavity equivalent input voltage v ab .

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