CN117424458B

CN117424458B - Control method, system and controller of power supply conversion circuit

Info

Publication number: CN117424458B
Application number: CN202311744892.1A
Authority: CN
Inventors: 谭诗干; 唐建明; 钟康; 黄旭辉; 高飞
Original assignee: Shenzhen Tongye Technology Co ltd
Current assignee: Shenzhen Tongye Technology Co ltd
Priority date: 2023-12-19
Filing date: 2023-12-19
Publication date: 2024-02-23
Anticipated expiration: 2043-12-19
Also published as: CN117424458A

Abstract

The present disclosure relates to the field of power control technologies, and in particular, to a method, a system, and a controller for controlling a power conversion circuit, where the method is applicable to the power conversion circuit; the power conversion circuit comprises a front-stage LLC circuit and a rear-stage BUCK circuit; the method comprises the following steps: according to the working scene of the power supply conversion circuit, determining the gain of the power supply conversion circuit, and recording the gain as the total gain of the power supply conversion circuit; selecting a gear in which the power conversion circuit works from a plurality of set gears according to the total gain of the power conversion circuit and the load condition of the power conversion circuit; the plurality of gears are set according to the different values of the open-closed loop working state of the front-stage LLC circuit, the gain of the front-stage LLC circuit, the open-closed loop working state of the rear-stage BUCK circuit and the duty ratio of the BUCK unit. Therefore, the power conversion circuit can effectively solve the problems of low power conversion efficiency, high output ripple current and the like of the existing wide-range power conversion circuit.

Description

Control method, system and controller of power supply conversion circuit

Technical Field

The present disclosure relates to the field of power control technologies, and in particular, to a method and a system for controlling a power conversion circuit, and a controller.

Background

The full-bridge/half-bridge LLC resonant soft switching power supply technology has the advantage of extremely high conversion efficiency, and is widely applied to the fields of battery charging power supplies and other charging power supplies. However, compared with the traditional circuits such as full-bridge phase-shifting conversion and full-bridge forward conversion with duty ratio, the LLC conversion circuit based on frequency modulation has the defect of narrow output voltage regulation range, for example, the regulation range can be 1-1.6 times, and the regulation of larger multiplying power is very difficult. When the gain is 1 at the resonance point, the LLC resonance transformation can improve the gain by reducing the frequency, but the range is limited, if the gain exceeds more than 1.6, the resonance parameter design becomes more and more difficult, the power transformation efficiency is also reduced, and the adoption is less and less; the gain is smaller than 1 when the frequency is increased, but the switching device works in a hard switching mode, so that the switching efficiency is low, the impact of the switching device is large, and the switching device is rarely adopted. Therefore, when the individual LLC conversion gain variation exceeds [1,1.6], it is difficult to achieve the maximum voltage of 16V (corresponding to gain 1.6) for an LLC conversion output, and, according to this gain range, only 10V (corresponding to gain 1) can be achieved at the minimum, but below 10V, it is difficult to operate effectively due to large current ripple, poor efficiency, inability to achieve soft switching, and the like.

Therefore, in order to cope with the needs of the wide voltage output scene, for the situations that the wide voltage output needs to be adapted, such as a battery charging cabinet, a power supply device and the like, a power supply conversion circuit is usually set to be two-stage conversion, one-stage LLC resonance soft switching realizes high-efficiency isolation conversion, and then one-stage conversion control such as BUCK hard switching is added to realize wide voltage regulation, so that the output of the full voltage range from 0V to rated voltage is realized.

In the two-stage conversion design mode, two-stage independent control (or inner and outer ring control) is generally adopted, and the control method is the simplest, but has the defects that the conversion efficiency of the whole power supply of the two-stage conversion is not the highest, the output ripple current is relatively high, and the like.

Disclosure of Invention

In view of this, the embodiments of the present application provide a control method, a system and a controller for a power conversion circuit, which can effectively solve the problems of low power conversion efficiency and high output ripple current existing in the existing wide-range power conversion circuit.

In a first aspect, embodiments of the present application provide a method for controlling a power conversion circuit, where the method is applicable to the power conversion circuit; the power supply conversion circuit comprises a front-stage LLC circuit and a rear-stage BUCK circuit;

the pre-stage LLC circuit comprises N groups of LLC resonant units; the post-stage BUCK circuit comprises M paths of BUCK units; the size of N is determined according to the input of the power supply conversion circuit and the voltage withstand value of the MOS switching device in the LLC resonance unit; the size of M is determined according to the output of the power supply conversion circuit and the current capacity of the selected MOS switching device; the method comprises the following steps:

Determining the overall gain of the power supply conversion circuit according to the working scene and circuit design composition of the power supply conversion circuit, and marking the overall gain as the overall gain of the power supply conversion circuit;

selecting a gear in which the power conversion circuit works from a plurality of set gears according to the total gain of the power conversion circuit and the load condition of the power conversion circuit; the gear positions are set according to the open-closed loop working state of the front-stage LLC circuit, the gain of the front-stage LLC circuit, the open-closed loop working state of the rear-stage BUCK circuit and the value of the duty ratio of the BUCK unit;

and controlling the power conversion circuit to perform conversion work according to the selected gear of the power conversion circuit.

In some embodiments, in the controlling the power conversion circuit to perform conversion operation, the method further includes: controlling the frequency of the corresponding input signals among N groups of LLC resonant units to be the same, wherein the phase difference among the input signals is 360 degrees/N; the phase difference of the input signals corresponding to M paths of BUCK units is controlled to be 360 degrees/M, and the duty ratio is the same; and controlling the BUCK unit to work in a CCM continuous current mode.

In some embodiments, the plurality of gear positions are set according to an open-close loop operation state of the preceding stage LLC circuit, a gain of the preceding stage LLC circuit, and a combination of different values and different states of the open-close loop operation state of the succeeding stage BUCK circuit and a duty ratio of the BUCK unit, including:

According to the group number M of the BUCK units, M+1 gears are determined;

the working conditions of the front stage LLC circuit and the rear stage BUCK circuit corresponding to the M+1 gears are as follows:

gear 1: controlling the pre-stage LLC circuit to work in a frequency modulation closed loop control state, and controlling the gain of the pre-stage LLC circuit to be 1, g and 1.35-1.45; controlling the back-stage BUCK circuit to work in a fixed through state;

any one of the 2 nd to M th gear j: controlling the pre-stage LLC circuit to work in a frequency modulation closed-loop control state, wherein the gain of the pre-stage LLC circuit is [1, g ]]G is more than or equal to 1.35 and less than or equal to 1.45; the open loop operation of the back-stage BUCK circuit is controlled to be in a fixed duty ratioA state; j is more than or equal to 2 and less than or equal to M;

m+1st gear: and controlling the front-stage LLC circuit to work at a fixed resonance point in an open loop manner, wherein the gain of the front-stage LLC circuit is 1, and controlling the rear-stage BUCK circuit to work in a closed loop control state of duty ratio adjustment.

In some embodiments, the selecting a gear in which the power conversion circuit operates from a plurality of set gears according to the total gain of the power conversion circuit and the load condition of the power conversion circuit includes:

dividing the value range [0, g ] of the total gain of the power supply conversion circuit into M+1 sub-gain intervals in a mode of decreasing the total gain of the power supply conversion circuit, wherein the i sub-gain intervals are correspondingly marked as i sub-gain intervals, and i is more than or equal to 1 and less than or equal to M+1;

Judging a sub-gain section in which the total gain of the power supply conversion circuit is positioned, and obtaining a determined sub-gain section; judging the load condition of the power supply conversion circuit; the load conditions of the power supply conversion circuit comprise normal load and light load; the normal load finger load current is larger than the rated current set proportion value;

if the determined sub-gain section is positioned in the q-th sub-gain section, q is more than or equal to 1 and less than or equal to M, and the load condition of the power conversion circuit is normal load, selecting the q-th gear;

and if the determined sub-gain section is positioned in the M+1th sub-gain section or the load condition of the power conversion circuit is light load, selecting the M+1th gear.

In some embodiments, the selecting a gear in which the power conversion circuit operates from a plurality of set gears according to the total gain of the power conversion circuit and the load condition of the power conversion circuit further includes:

when the load current is larger than the set current value and works in the [2, M ] gear, the BUCK unit is kept to work in a CCM continuous current mode, and the switching frequency of the BUCK unit is determined to be reduced according to the inductance size, the load current and the input and output voltage of the BUCK unit.

In some embodiments, the determining the overall gain of the power conversion circuit according to the working scenario and the circuit design configuration of the power conversion circuit, which is marked as the overall gain of the power conversion circuit, includes:

if N groups of LLC resonant units in the pre-stage LLC circuit are connected in series, the total gain of the power conversion circuit is obtained by adopting the following formula:

if N groups of LLC resonant units in the pre-stage LLC circuit are connected in parallel, the total gain of the power conversion circuit is obtained by adopting the following formula:

wherein,representing the total gain of the power conversion circuit, +.>Represents output voltage, K represents power conversion powerThe way transformation ratio, M represents BUCK unit group number, < ->Representing the input voltage.

In some embodiments, 1.ltoreq.N.ltoreq.6, 1.ltoreq.M.ltoreq.6.

In a second aspect, embodiments of the present application provide a power conversion circuit control system, the system including a controller and a power conversion circuit; the power conversion circuit includes: the power conversion circuit comprises a front-stage LLC circuit and a rear-stage BUCK circuit which are connected in series; the pre-stage LLC circuit comprises N groups of LLC resonant units; the post-stage BUCK circuit comprises M paths of BUCK units; the size of N is determined according to the input of the power supply conversion circuit and MOS voltage withstand capacity in the LLC resonance unit; the size of M is determined according to the output of the power supply conversion circuit;

The controller controls the power conversion circuit according to a control method of the power conversion circuit provided in the first aspect of the present application.

In some embodiments, when the input voltage is less than the input high voltage limit value, then the N sets of LLC resonant cells are connected in parallel;

when the input voltage is greater than or equal to the input high-voltage limit value, N groups of LLC resonant units are connected in series;

when the output voltage is greater than or equal to the output high voltage limit value, M paths of BUCK units are connected in series;

and when the output voltage is smaller than the output high-voltage limit value, the M paths of BUCK units are connected in parallel. In a third aspect, embodiments of the present application provide a power conversion controller, where the power conversion controller includes a processor and a memory, where the memory stores a computer program, and the processor is configured to execute the computer program to implement a control method of a power conversion circuit provided in the first aspect of the present application.

The embodiment of the application has the following beneficial effects:

according to the gear shifting control design with two-stage fusion, a plurality of gears are set according to the open-closed loop working state of the front-stage LLC circuit, the gain of the front-stage LLC circuit, the open-closed loop working state of the rear-stage BUCK circuit and the value of the duty ratio of the BUCK unit. Then, according to the working scene and circuit design composition of the power supply conversion circuit, determining the overall gain of the power supply conversion circuit, and marking the overall gain as the overall gain of the power supply conversion circuit; and finally, selecting a gear in which the power conversion circuit works from a plurality of set gears according to the total gain of the power conversion circuit and the load condition of the power conversion circuit. According to the working scene of the power supply conversion circuit, the open-closed loop working states of the front stage LLC circuit and the rear stage BUCK circuit are controlled, the gain of the front stage LLC circuit is controlled by controlling the input frequency, and the duty ratio of the BUCK unit is determined according to the output, so that the characteristics of optimal overall efficiency and minimum ripple current are achieved. Therefore, the power conversion circuit can effectively solve the problems of low power conversion efficiency, high output ripple current and the like of the existing wide-range power conversion circuit.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered limiting the scope, and that other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

FIG. 1 is a flow chart of a control method of a power conversion circuit according to an embodiment of the present application;

FIG. 2 is a schematic circuit diagram of a power conversion circuit according to an embodiment of the present application;

FIG. 3 shows a schematic diagram of superimposed current ripple output when the three-phase BUCK in the embodiment of the application works alternately at a 2/3 duty cycle;

FIG. 4 shows a schematic diagram of superimposed output current ripple when the three-phase BUCK in the embodiment of the application works in a staggered manner at a 1/3 duty cycle;

FIG. 5 is another flow chart of a control method of the power conversion circuit according to the embodiment of the present application;

fig. 6 shows a schematic structural diagram of a control device of the power conversion circuit according to the embodiment of the present application.

Description of main reference numerals:

110-input capacitance; 120-full bridge LLC resonant circuit; 130-an output rectifying circuit; a 200-BUCK circuit; 610-a circuit total gain calculation module; 620-gear selection module; 630-a transition drive module.

Detailed Description

The following description of the embodiments of the present application will be made clearly and completely with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, not all embodiments.

The components of the embodiments of the present application, which are generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, as provided in the accompanying drawings, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present application without making any inventive effort, are intended to be within the scope of the present application.

In the following, the terms "comprises", "comprising", "having" and their cognate terms may be used in various embodiments of the present application are intended only to refer to a particular feature, number, step, operation, element, component, or combination of the foregoing, and should not be interpreted as first excluding the existence of or increasing the likelihood of one or more other features, numbers, steps, operations, elements, components, or combinations of the foregoing. Furthermore, the terms "first," "second," "third," and the like are used merely to distinguish between descriptions and should not be construed as indicating or implying relative importance.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which various embodiments of this application belong. The terms (such as those defined in commonly used dictionaries) will be interpreted as having a meaning that is identical to the meaning of the context in the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein in connection with the various embodiments.

Some embodiments of the present application are described in detail below with reference to the accompanying drawings. The embodiments described below and features of the embodiments may be combined with each other without conflict.

The power conversion circuit generally adopts two-stage independent control (or called internal and external loop control), wherein the front stage is a small closed loop, and the rear stage is a large closed loop. If the LLC conversion link is usually arranged near the resonance point and works in an open loop with fixed frequency to realize the isolation conversion with the highest efficiency, the isolation transformation ratio of the input voltage and the output voltage of the stage is also fixed; then, the duty ratio of the BUCK conversion is controlled and regulated to realize the required output voltage change regulation, and the required current change regulation is also included. Namely, the front stage LLC always works in an open loop to realize isolation and basic transformation ratio control, and the BUCK always works in a closed loop to realize closed loop regulation of current and voltage. The control method is the simplest, but has the defects that the conversion efficiency of the two-stage conversion overall power supply is not the highest, the output ripple current is relatively high, and the like. Therefore, the control method, the system and the controller of the power supply conversion circuit can effectively solve the problems of low power supply conversion efficiency, high output ripple current and the like of the existing wide-range power supply conversion circuit.

The method is suitable for a power supply conversion circuit; the power supply conversion circuit comprises a front-stage LLC circuit and a rear-stage BUCK circuit; the pre-stage LLC circuit and the post-stage BUCK circuit are serially connected. The pre-stage LLC circuit comprises N groups of LLC resonant units; the post-stage BUCK circuit comprises M paths of BUCK units; the size of N is determined according to the input of the power supply conversion circuit and the voltage withstand value of the MOS switching device in the LLC resonance unit; and the size of M is determined according to the output of the power conversion circuit and the current capacity of the selected MOS switching device.

Further, considering the voltage-withstanding capability and the current-carrying capability of devices such as a common MOS tube or a silicon carbide MOS tube in the power supply conversion circuit, N groups of LLC resonant units can be connected in series or in parallel. M-path BUCK units can be connected in parallel or in series. In short, when the current is larger than the load current of the MOS tube, the voltage is larger than the load voltage of the MOS tube, and the voltage is connected in series, and the specific value of N, M is determined according to the input and output of the power conversion circuit.

The highest withstand voltage of the common MOS tube is 1200V, and the highest withstand voltage of the silicon carbide MOS tube commonly used at present is also 1200V.

After PFC rectification is carried out on three-phase 380VAC of commercial power, the voltage is generally about 700V; after PFC rectification is carried out on the commercial power of 220Vac, the voltage is generally about 400V; the input voltage in this embodiment refers to the dc voltage after ac rectification and the voltage when dc is directly input from the outside. Thus, the present embodiment defines the input high voltage threshold as 800V, the input voltage is lower than 800V and the input voltage is higher than or equal to 800V. The output high voltage limit value is defined as 500V, the output voltage is defined as high voltage when the output voltage is equal to or greater than 500V, and the output voltage is defined as low voltage when the output voltage is less than 500V.

The specific connection conditions of the front-stage LLC circuit and the rear-stage BUCK circuit comprise the following steps:

1) When the input voltage is less than 800V, the N groups of LLC resonant units are connected in parallel; i.e. in a low voltage high current input scenario, then the N groups of LLC resonant units are connected in parallel. The input voltage is lower than 220V, and the input voltage is lower than the low voltage, and the input voltage is called heavy current when the current in the power conversion circuit is larger than the maximum bearing current of the MOS tube in the LLC resonance unit.

2) When the input voltage is greater than or equal to 800V, N groups of LLC resonant units are connected in series; that is, at the time of high voltage input, N sets of LLC resonant units are connected in series. When the final product adopts 220Vac or three-phase 380Vac as the commercial power to supply power, the current is boosted and rectified by PFC, the current is generally less than 800V and belongs to low voltage, the value range is [200V,800V ], otherwise, the current is high voltage when the current is input to other scenes with the value of more than 800V. For example, the highest withstand voltage of the MOS tube in the LLC resonant unit is 1200V, if the input voltage is more than 2000V, and further, the limit working condition is considered, 3000V voltage is required to be born, so that 3 LLC resonant units are required to be connected in series to meet the requirement (3600 > 3000V).

3) When the output voltage is more than or equal to 500V, M paths of BUCK units are connected in series; i.e. in a high voltage output scenario, M groups of BUCK units are connected in series.

4) When the output voltage is less than 500V, M paths of BUCK units are connected in parallel. I.e. when large current is output, M groups of BUCK units are connected in parallel.

In a word, LLC resonant units in the front stage LLC circuit are not limited to be connected in series, and can be connected in parallel in a low-voltage high-power input scene; the BUCK units in the later stage BUCK circuit are not limited to be connected in parallel, and can also be connected in series (multi-level BUCK conversion) in a high-voltage output scene. The number of the serial-parallel connection stages is not limited to 3 groups. For example, a common MOS tube maximally bears 30A current, and a silicon carbide MOS tube maximally bears 100A current, if 200A is needed, 7 common MOS tubes need to be connected in parallel, and at least 2 silicon carbide MOS tubes need to be connected in parallel. Preferably, 1.ltoreq.N.ltoreq.6, 1.ltoreq.M.ltoreq.6. Namely, N can be 1, namely a single LLC resonant unit, no series-parallel connection exists, and the situation is common; m can also take 1, preferably, when M takes 3, the working condition scene covered by the lowest ripple effect is wider, and when taking 1, only about 50% of the working condition scene is covered. When N or M is more than 6, the complexity is high and generally not used.

In order to meet the high-power requirement, a front stage LLC circuit and a rear stage BUCK circuit are usually connected in parallel by adopting a plurality of groups of conversion units respectively; in order to meet the needs of input or output voltage and current, a plurality of groups of conversion units are connected in series respectively, so that the needs of different scenes are met. Wherein both the LLC resonant unit and the BUCK unit are referred to as conversion units. The LLC resonant unit can be a full-bridge LLC resonant unit or a half-bridge resonant unit. Illustratively, a power conversion circuit in the present application, the front stage LLC circuit includes 3 sets of full-bridge LLC resonant units connected in series, and the back stage BUCK circuit includes 3 sets of parallel BUCK units. 3 groups of full-bridge LLC resonant units are connected in series to meet the requirement of high input voltage; the 3-way BUCK units are connected in parallel to meet the requirement of large current. The power supply conversion circuit can realize high-voltage input and low-voltage output, for example, the input voltage is 1500V, and the output voltage is 0-110V.

Fig. 2 shows a circuit schematic of a power conversion circuit according to an embodiment of the present application, where a front stage LLC circuit includes 3 sets of full-bridge LLC resonant units connected in series, and a rear stage BUCK circuit includes 3 sets of parallel BUCK units. In the figure, C1, Q2, Q3, Q4, lr1, cr1, T1 and D1-D4 form 1 group of full-bridge LLC resonance units; q13, D13 and L1 form a 1-path BUCK unit; c2, Q5, Q6, Q7, Q8, lr2, cr2, T2, D5-D8 form a group 2 full-bridge LLC resonant unit (full-bridge LLC conversion unit); q14, D14, L2 constitute the 2 nd BUCK conversion. C3, Q9, Q10, Q11, Q12, lr3, cr3, T3 and D9-D12 form a 3 rd group full-bridge LLC resonance unit; q15, D15 and L3 form a 3 rd BUCK unit; c1, C2, and C3 in fig. 2 are also referred to as input capacitors 110; Q1-Q12, lr 1-Lr 3, cr 1-Cr 3, and T1-T3 are also referred to as full-bridge LLC resonant circuits 120; d1 to D12 are also called output rectifying circuits 130; the 1 st, 2 nd and 3 rd BUCK units are also collectively referred to as BUCK circuit 200.

The control method of the power conversion circuit will be described with reference to specific embodiments.

Fig. 1 shows a flowchart of a control method of a power conversion circuit according to an embodiment of the present application. The control method of the power conversion circuit comprises the following steps:

S10, determining the overall gain of the power conversion circuit according to the working scene and circuit design composition of the power conversion circuit, and marking the overall gain as the overall gain of the power conversion circuit.

In one embodiment, in step S10, according to the operating scenario of the power conversion circuit, the overall gain of the power conversion circuit, labeled as the overall gain of the power conversion circuit, is determined, where the overall gain of the power conversion circuit is equal to the gain of the preceding stage LLC circuit multiplied by the gain of the succeeding stage BUCK circuit, and includes:

wherein,representing the total gain of the power conversion circuit, +.>Represents output voltage, K represents combined transformation ratio of transformer unit and rectification of power conversion circuit (power conversion circuit is also called transformer), M represents BUCK unit group number, < >>Representing the input voltage.

S20, selecting a gear in which the power conversion circuit works from a plurality of set gears according to the total gain of the power conversion circuit and the loading condition of the power conversion circuit.

The gear positions are set according to the different values of the open-closed loop working state of the front-stage LLC circuit, the gain of the front-stage LLC circuit, the open-closed loop working state of the rear-stage BUCK circuit and the duty ratio of the BUCK unit.

The normal load refers to that the output current is larger (for example, when the rated current is more than 10 percent), and the inductance current of each BUCK unit is continuous, namely, the CCM mode or the critical continuous. The light load means that the output current is very low, so that the inductance current of a single BUCK unit is discontinuous. Normal load: under loaded conditions, such as in a charged state; the charging is started with a relatively high power, and near the full time, there is a time when the current is low, and the time is no-load, also called light-load.

Light load, including no load: for example, after the battery is fully charged, only constant-voltage floating charge is performed at the moment, the charging current is very low, or the direct turn-off current of a battery BMS loop is 0, and the inductance current of the BUCK unit is discontinuous at the moment; for another example, when the battery is discharged for a long time or is not used for a long time, a short time of working condition close to 0V can occur when no electricity is used.

In one power conversion circuit shown in fig. 2, the input nominal voltage is assumed to be 1500V, and the final output voltage is 0-115V. When the input voltage is 1800V, the pre-stage LLC circuit operates at a resonance point gain of 1, and outputs an intermediate rectified bus voltage of 100V, which is equal to the lower limit of the output voltage range under normal conditions described later, and at this time, the transformer transformation ratio=1800V/3/100=6:1.

In order to exert the highest LLC conversion efficiency, the gain of the pre-stage LLC circuit is controlled to be within the range of [1, g ], and g is more than or equal to 1.35 and less than or equal to 1.45. The gain value range [1, g ] is the maximum value of the preceding LLC circuit, and the value of g is determined by the specifically designed resonant circuit parameters. The optimal conversion efficiency can be obtained only when the value of g is usually designed to be 1.35-1.45, and the gain adjustment range is considered; if g=1.2, the efficiency is inherently higher, but the gain adjustment range is too narrow; on the contrary, g=1.6 or more is rare and g=2.0 or more is almost rare due to efficiency influence. Thus, the expression "1.35.ltoreq.g.ltoreq.1.45" is a range of usual designs, and once the circuit parameters are determined, the g value is determined to be 1.4 or 1.35.

The following describes the principle of setting the gain range of the pre-stage LLC circuit:

when the LLC resonant unit is controlled, the gain of the pre-stage LLC circuit is controlled to be kept within 1-1.4 times by controlling the input voltage frequency to work in a section below a resonance point, so that the highest LLC conversion efficiency is exerted. If the gain is [1,1.4], the gain range is narrower, which is beneficial to designing better LLC resonance hardware parameters to keep higher resonance transformation efficiency. If the gain range of the preceding stage LLC circuit is smaller in the control design of the preceding stage LLC circuit, the K value can be larger, and the K value corresponding to the gain of 1.4 times can be more than 8. Therefore, when the resonance inductance is unchanged, the inductance of the transformer is larger, so that the exciting current is small under the same working frequency, and the transformer and loop impedance loss are lower, thereby improving the working efficiency. Conversely, if the gain adjustment range is large, for example, 1 to 1.6 times or more, the K value coefficient can only be selected to be a lower value, for example, about 4 times, and when the resonant inductance is unchanged, the inductance of the transformer is small, so that the exciting current is large, the line loss is increased, and the conversion efficiency is reduced.

The total gain range determines the regulation capability of the output voltage range, and the gain range [1, g ] of the front stage LLC circuit is limited and is equivalent to 1 at the lowest, so that the lower voltage can be obtained only through the rear stage BUCK circuit, the gain range of the rear stage BUCK circuit is [0,1], and the regulation of the full voltage range can be realized.

Further, in order to reduce the loop ripple current, when the power conversion circuit is controlled to perform conversion operation, the frequencies of the input signals corresponding to the N groups of LLC resonant units are controlled to be the same, and the phase difference between the input signals is 360 degrees/N; the phase difference of the input signals corresponding to M paths of BUCK units is controlled to be 360 degrees/M, and the duty ratio is the same; the control BUCK unit works in CCM continuous current mode with the best effect, and the BUCK unit works in non-CCM continuous current mode with the inferior effect. The current mode is most relevant to the inductance design of the BUCK circuit, and when the inductance design guarantees more than 10% of output current, the inductance current enters a continuous state, and the inductance current is designed to be more than 20% to guarantee the continuous current state. That is, the BUCK unit operates in CCM continuous current mode when the power conversion circuit is normally loaded, and operates in non-CCM continuous current mode when the power conversion circuit is lightly loaded.

The BUCK unit design works in CCM continuous current mode, and the BUCK circuit works in CCM continuous current mode under the condition that the filter inductor L is large enough, and the current of each BUCK unit is continuous under normal load.

In order to reduce loop ripple current, the PWM working control time sequence of 3 groups of full-bridge LLC resonant units keeps phase-staggering control, namely the frequency is kept the same in real time, and the phases are respectively phase-staggering by 120 degrees; the BUCK cell also maintains a phase dislocation phase of 120 ° at its PWM chopping period. In the interleaving control, if the BUCK cells are 4 groups, the phases are interleaved by 90 degrees.

Based on the staggered parallel connection of the 3 phases in the back-stage BUCK circuit, the equivalent working frequency is 3 times of that of single-path conversion, so that output ripple is greatly reduced, or inductance design can be reduced, inductance impedance loss is reduced, the efficiency of a BUCK unit conversion link is improved, and the volume weight of an inductor is smaller. Exemplary, based on three-phase interleaving, when the BUCK units work at 1/3 and 2/3 duty cycles, the current ripple of the three-phase BUCK units is completely cancelled, the output ripple current is 0 in theory, only the direct current constant value is adopted, the output ripple current is 0 when the BUCK units are directly connected, fig. 3 shows a schematic diagram of current ripple superposition output when the three-phase BUCK units work at 2/3 duty cycles in an interleaved manner, and fig. 4 shows a schematic diagram of current ripple superposition output when the three-phase BUCK units work at 1/3 duty cycles in an interleaved manner.

In one embodiment, the plurality of gear positions are set according to the open-closed loop operation state of the preceding stage LLC circuit, the gain of the preceding stage LLC circuit, and the combination of different values and different states of the open-closed loop operation state of the following stage BUCK circuit and the duty ratio of the BUCK unit, including:

determining M+1 gears according to the group number M of BUCK units;

gear 1: controlling the pre-stage LLC circuit to work in a frequency modulation closed loop control state, and controlling the gain of the pre-stage LLC circuit to be 1, g and 1.35-1.45; controlling the post-stage BUCK circuit to work in a fixed straight-through state;

any one of the 2 nd to M th gear j: the pre-stage LLC circuit is controlled to work in a frequency modulation closed-loop control state, and the gain of the pre-stage LLC circuit is [1, g ]]G is more than or equal to 1.35 and less than or equal to 1.45; control the post-stage BUCK circuit to work at a fixed duty ratio in an open loop mannerA state; j is more than or equal to 2 and less than or equal to M;

m+1st gear: the open loop of the front stage LLC circuit is controlled to work at a fixed resonance point, the gain of the front stage LLC circuit is 1, and the back stage BUCK circuit is controlled to work in a closed loop control state of duty ratio adjustment.

Illustratively, the present application adopts a two-stage fused shift control design in combination with the characteristics of LLC resonant transformation and BUCK staggered parallel connection. The pre-stage LLC circuit conversion link does not always work in a fixed frequency in an open loop mode, and more time-to-time frequency conversion works in a closed loop control mode. The conversion link of the back-stage BUCK circuit does not always work in a closed-loop control state with a variable duty ratio, and more time periods work in an open-loop control state with a fixed duty ratio. For example, n=3, m=3, and the corresponding m+1 gears specifically include the following:

First gear: the conversion link of the front stage LLC circuit works in a frequency modulation closed loop control state, the gain of the front stage LLC circuit can be adjusted between 1 and 1.4, the rear stage BUCK circuit works in a fixed through state, and the fixed gain of the BUCK link is 1. At the moment, the rear-stage BUCK circuit works in a direct-connection state, no switching loss exists, the LLC resonance unit also works in a resonance state, and the comprehensive efficiency is highest.

Second gear: the conversion link of the front stage LLC circuit works in a frequency modulation closed-loop control state, the gain of the front stage LLC circuit can be adjusted between 1 and 1.4, the open loop of the rear stage BUCK circuit works in a fixed duty ratio 2/3 state, and the fixed gain of the rear stage BUCK circuit is 2/3. At this time, the BUCK unit works in a three-phase staggered state with a duty ratio of 2/3, as shown in fig. 3, and the output theoretical ripple of the later stage BUCK circuit is 0.

Third gear: the conversion link of the front stage LLC circuit works in a frequency modulation closed-loop control state, the gain of the front stage LLC circuit can be adjusted between 1 and 1.4, the BUCK unit works in a fixed duty ratio 1/3 state in an open loop mode, and the fixed gain of the rear stage BUCK circuit is 1/3. At this time, the BUCK unit works in a three-phase staggered state with a duty ratio of 1/3, as shown in FIG. 4, and the output theoretical ripple of the rear-stage BUCK circuit is 0.

Fourth gear: the conversion link of the front stage LLC circuit works in a fixed resonance point in an open loop mode, and the rear stage BUCK circuit works in a closed loop control state of duty ratio adjustment.

In one embodiment, selecting a gear in which the power conversion circuit operates from among a plurality of gear settings according to a total gain of the power conversion circuit and a load condition of the power conversion circuit includes:

dividing the value range [0, g ] of the total gain of the power supply conversion circuit into M+1 sub-gain intervals according to the mode of decreasing the total gain of the power supply conversion circuit, wherein the i sub-gain intervals are correspondingly marked as i sub-gain intervals, and i is more than or equal to 1 and less than or equal to M+1;

judging a sub-gain section in which the total gain of the power supply conversion circuit is positioned, and obtaining a determined sub-gain section; judging the load condition of the power supply conversion circuit; the load conditions of the power supply conversion circuit comprise normal load and light load; the normal load indicates that the load current is larger than the rated current set proportion value;

if the determined sub-gain section is positioned in the q-th sub-gain section, q is more than or equal to 1 and less than or equal to M, and the load condition of the power supply conversion circuit is normal load, selecting the q-th gear;

if the determined sub-gain section is positioned in the M+1th sub-gain section or the load condition of the power conversion circuit is light load, selecting the M+1th gear.

Further, in order to reduce switching loss and improve efficiency, the total ripple current of the BUCK is kept to be 0, when the load current is larger than the set current value and the BUCK is operated in [2, M ] gear, the BUCK unit is kept to operate in a CCM continuous current mode, and the switching frequency of the BUCK unit is determined to be reduced according to the size of the inductor, the load current and the input and output voltage of the BUCK unit. For example, the load current is more than or equal to 50% of rated current, so that the frequency of conversion of the BUCK unit can be greatly reduced, the switching loss is reduced, the efficiency is further improved, and meanwhile, the total ripple current of the later-stage BUCK circuit is kept to be 0. The specific switching frequency value can be accurately calculated or approximately calculated according to the inductance, the load current, the input and output voltage of the BUCK unit and the like, so that current continuity is ensured.

The total gain g=output voltage x transformer transformation ratio x N/input voltage of the power conversion circuit. For example, 1600V is input and 110V is output, the transformer transformation ratio is designed in the preamble, and g=1.24), and then the above gear is selected according to the total gain G of the power conversion circuit and the load condition, so as to realize the matching fusion control of two stages of different gears, specifically:

if g= [1.0,1.4], and when the vehicle is loaded normally, the first gear control is selected to cope with all normal conditions.

If g= [0.67,1], and under normal load, the second gear control is selected to cope with the lower voltage condition. If the full voltage is 100%, the lower voltage ranges from 60% to 80% of the full voltage.

If g= [0.33, 67], and under normal load, the third gear control is selected, corresponding to outputting a lower voltage condition. If the full voltage is 100%, the lower voltage ranges from 30% to 60% of the full voltage.

If G= [0,0.33], or if the belt is very light, selecting the fourth gear control, corresponding to the light load and the voltage condition close to 0V output. If the full load current is 100%, the corresponding current of the light load is 10% or less of the full current, the light load definition is basically based on whether the inductance current of the BUCK unit is continuous or not, the inductance current of the BUCK unit is no-load, namely the light load, and the inductance current of the BUCK unit is normal load when the inductance current of the BUCK unit is continuous. The normal working condition is described according to the input voltage, the output voltage and the load state, and represents the maximum probability and the most common typical range of the power supply in time and space when the power supply is actually used in daily work.

Input voltages corresponding to normal working conditions, such as 220VAc single-phase mains supply, are quite common in the range of 220-235 VAC; the rail is powered by 1500V DC power, and the voltage fluctuation is most common in the range of 1500-1800V. Although the power supply standard may be outside the above range, it is extremely rare. Based on the above scenario, the normal condition is defined according to the ratio of the maximum value to the minimum value of the input voltage fluctuation, for example, the ratio is 1.2.

The output voltage corresponding to the normal operating condition, for example, when charging the battery, is typically near the nominal voltage. If the nominal voltage is 48V, the electric quantity below 42V is low, so that the voltage of the 48V lithium battery is defined in a 42V-48V range under the normal working condition; and if the nominal voltage is 110V, the voltage of the storage battery for a certain metro vehicle is usually 100-115V, and even if the voltage is completely less than 100V until the minimum value is 77V or the voltage is completely less than 0V, the voltage of the battery can be quickly increased to more than 100V within a few minutes after charging and enters a normal state. Based on the above scenario, the maximum/minimum value of the output voltage fluctuation corresponding to the normal condition may be defined within 1.15 times.

Based on the definition of the input normal voltage and the output normal voltage, the maximum change=1.2×1.15=1.38 < 1.4 of the total gain of the input and the output under the normal working condition is calculated, and the first gear controlled by the fusion gear can meet the regulation requirements of the voltage and the current. And under other working conditions, when the second gear and the third gear are controlled, the output current ripple is 0.

S30, controlling the power conversion circuit to perform conversion operation according to the selected gear of the power conversion circuit.

A control method of the power conversion circuit of the present application will be described with reference to an example of the power conversion circuit in fig. 2, that is, n=3, m=3, and as shown in fig. 5, the method includes the following steps:

s100, input voltage and output voltage which are correspondingly designed by the power conversion circuit are collected and updated.

S110, the total gain g=output voltage×3×transformer transformation ratio ≡input voltage of the power conversion circuit is calculated.

S120, judging a sub-gain section falling in according to the total gain G of the power conversion circuit, determining the load condition, and selecting a gear according to the total gain G of the power conversion circuit and the load condition. The load conditions include normal load and light load. The value of the current is 10% -100% of the full current in the normal load range, and the other conditions are light load, namely the BUCK inductance current is discontinuous.

The following procedure for selecting a gear is represented using a pseudo code:

if (G > 1 and normally loaded)

Fusion shift control flag = first gear control;

else if (0.67 < G < 1, and normally loaded)

Fusion shift control flag = second gear control;

else if (0.33 < G < 0.67, and normally loaded)

Fusion shift control flag = third gear control;

else if (0<G < 0.33, and light load)

Fusion shift control flag = fourth gear control;

Else

fusion shift control flag = fusion shift control flag;

case (fusion shift control mark)

First gear control: performing frequency modulation closed loop control on a pre-stage LLC circuit, controlling the gain of the pre-stage LLC circuit to be limited to 1-1.4, and generating PWM waves for the 3-path LLC resonant unit based on the phase dislocation of which the chopping period is 120 degrees; the 3-way BUCK unit switch is fixed and fully opened and directly connected.

Second gear control: performing frequency modulation closed-loop control on a pre-stage LLC circuit, controlling the gain of the pre-stage LLC circuit to be limited to 1-1.4, and enabling 3 LLC resonant units to generate waves based on 120-degree phase-dislocation PWM (pulse width modulation) of a chopping period; the fixed duty ratio of each BUCK unit switch is 2/3, and PWM wave generation is performed on 3-path BUCK units based on 120-DEG alternate on chopper period.

Third gear control: performing frequency modulation closed-loop control on a pre-stage LLC circuit, wherein the gain of the pre-stage LLC circuit is limited to 1-1.4, and 3 LLC resonant units emit waves based on PWM with a chopping period of 120 DEG phase stagger; the fixed duty ratio of each BUCK unit switch is 1/3, and PWM wave generation is alternately started for 3 paths of BUCK units based on the chopping period of 120 degrees.

Fourth gear control: controlling a pre-stage LLC circuit to work at a fixed and resonant point, wherein 3 LLC resonant units emit waves based on a phase-staggered PWM with a chopping period of 120 DEG; each BUCK unit works in a variable duty ratio state, keeps a phase-dislocation cooling closed-loop control state, calculates 1 closed loop of the BUCK unit to obtain a dynamic duty ratio, and alternately turns on PWM wave generation for 3 paths of BUCK units based on the chopping period of 120 degrees.

S130, controlling the power conversion circuit to perform conversion operation according to the selected gear of the power conversion circuit.

Furthermore, when the second gear control and the third gear control are selected, and the output current is larger, for example, more than or equal to 50% of rated current, the switching loss can be reduced by reducing the frequency of BUCK conversion, the efficiency is further improved, and meanwhile, the total ripple current of the rear-stage BUCK circuit is kept to be 0. The specific switching frequency value can be accurately calculated or approximately calculated according to the inductance, the load current, the input and output voltage of the BUCK unit and the like, so that current continuity is ensured.

The method adopts the fusion stepping control power supply conversion circuit for the first time, most of the time in the power supply conversion circuit works under normal working condition, the BUCK unit is directly connected without switching loss, the front-stage LLC circuit works near a resonance frequency point with lower gain, and the power supply conversion circuit has highest efficiency; the output end of the power supply conversion circuit has no switch conversion, so the electromagnetic interference is low.

Under most other working conditions, the closed-loop dynamic regulation is carried out by the front-stage LLC circuit, the rear-stage BUCK circuit is fixed at 1/3 or 2/3 gear, the sum ripple current of 3 phases is 0, and the output electromagnetic interference is low.

The application also provides a power conversion circuit control system, which comprises a controller and a power conversion circuit; the power conversion circuit includes: the power conversion circuit comprises a front-stage LLC circuit and a rear-stage BUCK circuit which are connected in series; the pre-stage LLC circuit comprises N groups of LLC resonant units; the post-stage BUCK circuit comprises M paths of BUCK units; the size of N is determined according to the input of the power supply conversion circuit and MOS load capacity in the LLC resonance unit; the size of M is determined according to the output of the power supply conversion circuit;

Controller a control method of a power conversion circuit of the present application controls the power conversion circuit.

In one embodiment, when the input voltage is less than 800V, then N sets of LLC resonant cells are connected in parallel;

when the input voltage is greater than 800V, N groups of LLC resonant units are connected in series;

when the output voltage is greater than 500V, M paths of BUCK units are connected in series;

when the output voltage is less than 500V, M paths of BUCK units are connected in parallel.

Wherein N is more than or equal to 1 and less than or equal to 6, and M is more than or equal to 1 and less than or equal to 6. It will be appreciated that the controller in the system of the present embodiment corresponds to the control method of the power conversion circuit of the above embodiment, and the options in the above embodiment are equally applicable to the present embodiment, so the description thereof will not be repeated here.

Fig. 6 shows a schematic structural diagram of a control device of the power conversion circuit according to the embodiment of the present application. Illustratively, the apparatus is for controlling a power conversion circuit; the power conversion circuit comprises a front-stage LLC circuit and a rear-stage BUCK circuit which are connected in series; the pre-stage LLC circuit comprises N groups of LLC resonant units; the post-stage BUCK circuit comprises M paths of BUCK units; the size of N is determined according to the input of the power supply conversion circuit and MOS load capacity in the LLC resonance unit; the size of M is determined according to the output of the power supply conversion circuit; the control device of the power conversion circuit comprises: a circuit total gain calculation module 610, a gear selection module 620, and a transition drive module 630.

The circuit total gain calculation module 610 is configured to determine an overall gain of the power conversion circuit according to a working scenario of the power conversion circuit, and mark the overall gain as the overall gain of the power conversion circuit;

a gear selection module 620, configured to select a gear in which the power conversion circuit operates from among a plurality of set gears according to a total gain of the power conversion circuit and a load condition of the power conversion circuit; the gear positions are set according to the different values of the open-closed loop working state of the front-stage LLC circuit, the gain of the front-stage LLC circuit, the open-closed loop working state of the rear-stage BUCK circuit and the duty ratio of the BUCK unit;

the conversion driving module 630 is configured to control the power conversion circuit to perform a conversion operation according to the selected gear of the power conversion circuit.

It will be appreciated that the apparatus of the present embodiment corresponds to the control method of the power conversion circuit of the above embodiment, and the options in the above embodiment are also applicable to the present embodiment, so the description thereof will not be repeated here.

The present application also provides a power conversion controller, which illustratively includes a processor and a memory, the memory storing a computer program, the processor being configured to execute the computer program to implement a control method of a power conversion circuit of the present application.

The power conversion controller includes a processor and a memory, wherein the memory stores a computer program, and the processor executes the computer program to cause the power conversion controller to execute the control method of the power conversion circuit or the functions of each module in the control device of the power conversion circuit.

The processor may be an integrated circuit chip with signal processing capabilities. The processor may be a general purpose processor including at least one of a central processing unit (Central Processing Unit, CPU), a graphics processor (Graphics Processing Unit, GPU) and a network processor (Network Processor, NP), a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic device, discrete hardware components. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like that may implement or perform the methods, steps, and logic blocks disclosed in embodiments of the present application.

The Memory may be, but is not limited to, random access Memory (Random Access Memory, RAM), read Only Memory (ROM), programmable Read Only Memory (Programmable Read-Only Memory, PROM), erasable Read Only Memory (Erasable Programmable Read-Only Memory, EPROM), electrically erasable Read Only Memory (Electric Erasable Programmable Read-Only Memory, EEPROM), etc. The memory is used for storing a computer program, and the processor can correspondingly execute the computer program after receiving the execution instruction.

The present application also provides a readable storage medium storing the computer program for use in the power conversion controller described above.

In the several embodiments provided in this application, it should be understood that the disclosed apparatus and method may be implemented in other manners as well. The apparatus embodiments described above are merely illustrative, for example, of the flow diagrams and block diagrams in the figures, which illustrate the architecture, functionality, and operation of possible implementations of apparatus, methods and computer program products according to various embodiments of the present application. In this regard, each block in the flowchart or block diagrams may represent a module, segment, or portion of code, which comprises one or more executable instructions for implementing the specified logical function(s). It should also be noted that, in alternative implementations, the functions noted in the block may occur out of the order noted in the figures. For example, two blocks shown in succession may, in fact, be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending upon the functionality involved. It will also be noted that each block of the block diagrams and/or flowchart illustration, and combinations of blocks in the block diagrams and/or flowchart illustration, can be implemented by special purpose hardware-based systems which perform the specified functions or acts, or combinations of special purpose hardware and computer instructions.

In addition, functional modules or units in the embodiments of the present application may be integrated together to form a single part, or each module may exist alone, or two or more modules may be integrated to form a single part.

The functions, if implemented in the form of software functional modules and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on such understanding, the technical solution of the present application may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a smart phone, a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the methods described in the embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.

The foregoing is merely specific embodiments of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think about changes or substitutions within the technical scope of the present application, and the changes and substitutions are intended to be covered by the scope of the present application.

Claims

1. A control method of a power conversion circuit, characterized in that the method is applied to the power conversion circuit; the power supply conversion circuit comprises a front-stage LLC circuit and a rear-stage BUCK circuit;

determining the total gain of the power supply conversion circuit according to the working scene and circuit design composition of the power supply conversion circuit, and marking the total gain as the total gain of the power supply conversion circuit;

Controlling the power conversion circuit to perform conversion according to the selected gear of the power conversion circuit;

the plurality of gear positions are set according to the open-closed loop working state of the preceding stage LLC circuit, the gain of the preceding stage LLC circuit, and the combination of different values and different states of the open-closed loop working state of the following stage BUCK circuit and the duty ratio of the BUCK unit, and the gear positions comprise:

according to the group number M of the BUCK units, M+1 gears are determined;

2. The method according to claim 1, wherein when the power conversion circuit is controlled to perform a conversion operation, the method further comprises: controlling the frequency of the corresponding input signals among N groups of LLC resonant units to be the same, wherein the phase difference among the input signals is 360 degrees/N; the phase difference of the input signals corresponding to M paths of BUCK units is controlled to be 360 degrees/M, and the duty ratio is the same; and controlling the post-stage BUCK circuit to work in a CCM continuous current mode.

3. The method according to claim 1, wherein selecting a gear in which the power conversion circuit operates from among a plurality of gear settings according to a total gain of the power conversion circuit and a load condition of the power conversion circuit, comprises:

4. The method according to claim 1, wherein the selecting a gear in which the power conversion circuit operates from among a plurality of gear settings according to the total gain of the power conversion circuit and the load condition of the power conversion circuit, further comprises:

5. The method for controlling a power conversion circuit according to claim 1, wherein determining the overall gain of the power conversion circuit, labeled as the overall gain of the power conversion circuit, according to the operating scenario and circuit design configuration of the power conversion circuit, comprises:

wherein,representing the total gain of the power conversion circuit, +.>Represents output voltage, K represents combined transformation ratio of transformer unit and rectification of power conversion circuit, M represents BUCK unit group number,/and/or the like>Representing the input voltage.

6. The method according to any one of claims 1 to 5, wherein 1.ltoreq.n.ltoreq.6, and 1.ltoreq.m.ltoreq.6.

7. A power conversion circuit control system, the system comprising a controller and a power conversion circuit; the power conversion circuit includes: the power conversion circuit comprises a front-stage LLC circuit and a rear-stage BUCK circuit which are connected in series; the pre-stage LLC circuit comprises N groups of LLC resonant units; the post-stage BUCK circuit comprises M paths of BUCK units; the size of N is determined according to the input of the power supply conversion circuit and MOS voltage withstand capacity in the LLC resonance unit; the size of M is determined according to the output of the power supply conversion circuit;

The controller controls the power conversion circuit according to the control method of the power conversion circuit according to any one of claims 1 to 6.

8. The power conversion circuit control system according to claim 7, wherein when the input voltage is less than the input high voltage limit value, then the N sets of LLC resonant cells are connected in parallel;

and when the output voltage is smaller than the output high-voltage limit value, the M paths of BUCK units are connected in parallel.

9. A power conversion controller, characterized in that it comprises a processor and a memory, the memory storing a computer program, the processor being adapted to execute the computer program to implement the control method of the power conversion circuit according to any one of claims 1-6.