Multi-level Buck-Boost converter and soft switching modulation control circuit and control method thereof

Abstract

The invention discloses a multi-level Buck-Boost converter and a soft switching modulation control circuit and a soft switching modulation control method thereof, a topological structure of the multi-level Buck-Boost converter has universality, and any level form of the multi-level Buck-Boost converter can be obtained by utilizing the topological structure according to input and output voltage levels. Meanwhile, a soft switching modulation strategy suitable for the multi-level Buck-Boost converter is provided, on the basis that soft switching of all switching tubes can be achieved in a global range, the pulsation and effective value of inductive current can be further reduced, and the power density of the converter can be improved. The invention correspondingly provides a control circuit and a control method for specifically realizing the soft switching modulation strategy, the control circuit is simple and reliable in structure, and smooth switching in different working modes can be ensured.

Description

Technical Field

[0001] The invention belongs to the technical field of power converters, and in particular relates to a multi-level Buck-Boost converter and a soft switching modulation control circuit and a control method thereof. Background Art

[0002] DC-DC converters are widely used in photovoltaic power generation, electric vehicles, and household energy storage. With the increase in power level requirements, the voltage levels of the above application scenarios are also increasing in order to improve conversion efficiency. For example, in photovoltaic power generation systems, the output voltage of photovoltaic modules has reached 1000V and is developing towards 1500V; the voltage level of electric vehicle battery systems has also transitioned from 400V to 800V.

[0003] Four Switch Buck-Boost (FSBB) converter has broad application prospects due to its homopolar output voltage, buck-boost function and bidirectional energy transmission. However, the FSBB converter is a two-level topology structure, with the left bridge arm being a Buck unit, and the voltage stress borne by the switch tube being the maximum input voltage; and the right bridge arm being a Boost unit, and the voltage stress borne by the switch tube being the maximum output voltage. Limited by the voltage rating of existing switch devices, the FSBB converter is not suitable for high voltage input applications.

[0004] In order to reduce the voltage stress of the switch tube, existing research has proposed the topology of the three-level six-tube Buck-Boost converter and the symmetrical three-level FSBB converter, and adopted the two-mode interleaved control method for control. However, as the voltage level of these three-level topologies increases further, the application scenarios will be limited; and they adopt the hard switching control strategy, and the switching loss will increase significantly as the switching frequency increases. Summary of the invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the above-mentioned prior art, provide a multi-level Buck-Boost converter and its soft switching modulation control circuit and control method, give a universal multi-level Buck-Boost converter topology suitable for any voltage level, and implement a soft switching modulation strategy for all switch tubes in the entire domain (the entire input voltage and load conversion range).

[0006] In order to achieve the above technical objectives, the technical solution adopted by the present invention is:

[0007] A multi-level Buck-Boost converter, the converter comprising a Buck unit, a Boost unit, an intermediate filter inductor and an output filter capacitor;

[0008] The Buck unit includes 2m switching tubes Q L1 , Q L2 ...Q L2m 、(m-1) flying capacitors C fL1 , C fL2 ……C fL(m-1) , forming (m+1) levels; flying capacitor C fL(q-1) The two ends of L2q The drain and Q L(2q-1) The source of is connected, q is any positive integer less than or equal to m; Q L1 With Q L2 Complementary conduction, Q L3 With Q L4 Complementary conduction, and so on, Q L(2m-1) With Q L2m Complementary conduction;

[0009] The Boost unit includes 2n switch tubes Q R1 , Q R2 ...Q R2n 、(n-1) flying capacitors C fR1 , C fR2 ……C fR(n-1) , forming (n+1) levels; flying capacitor C fR(p-1) The two ends of R2p The drain and Q R(2p-1) The source of is connected, p is any positive integer less than or equal to m; Q R1 With Q R2 Complementary conduction, Q R3 With Q R4 Complementary conduction, and so on, Q R(2n-1) With Q R2n Complementary conduction;

[0010] The intermediate filter inductor is connected to the midpoint of the Buck unit bridge arm and the midpoint of the Boost unit bridge arm respectively; the output filter capacitor is connected to both ends of the load;

[0011] m, n are any positive integers.

[0012] To optimize the above technical solutions, the specific measures taken also include:

[0013] The soft switching modulation strategy of the above converter includes:

[0014] (1) According to the on-off status of the Buck unit switch tube, the bridge arm midpoint voltage v is obtained A Can be V in ,

[0015]

[0016] According to the on-off status of the Boost unit switch tube, the bridge arm midpoint voltage v is obtained. B Can be V o , 0, where V in is the input voltage, V o is the output voltage;

[0017] (2) By v A and v B Get the voltage v across the intermediate filter inductor AB There are m×n combinations, and v AB There are four situations:

[0018] 1)v B =0,v A ≠0, then v AB Can be equal to V in , At this time, under any load condition, the intermediate filter inductor current i Lc Linear rise;

[0019] 2)v A =0,v B ≠0, then v AB Can be equal to -V o , At this time, under any load condition, i Lc Linear decline;

[0020] 3)v A =0,v B =0, then v AB =0,i Lc remain unchanged;

[0021] 4)v A ≠0, v B ≠0, then Where 0<m i ≤m,0<n i ≤n, and parameter m i and n i are all positive integers, i Lc Linear increase or linear decrease;

[0022] (3) At the beginning of each cycle, i Lc V in The slope of the linear rise; then the middle segment i Lc by The slope rises or falls linearly; finally, i Lc With -V o The slope decreases linearly until it drops to -I ZVS , with vAB =0 modulates the inductor current waveform to maintain -I ZVS Soft switching condition.

[0023] The above pair Lc The modulation method is:

[0024] like Then For the middle segment i Lc Modulation is performed, at this time the middle segment i Lc remain unchanged;

[0025] If any Then The smallest level combination for i Lc The waveform is modulated, and the middle segment i Lc Linear rise;

[0026] If any Likewise The smallest level combination for i Lc The waveform is modulated, and the middle segment i Lc Linear decline;

[0027] In other cases, there is no and exist simultaneously and When using and The level combination with the smallest absolute value in the Lc The waveform is modulated, and the middle segment i Lc The waveform rises linearly first and then falls linearly.

[0028] A control circuit for a multi-level Buck-Boost converter, for a multi-level Buck-Boost converter with m=2 and n=1, a Buck unit includes four switch tubes Q1, Q2, Q3, Q4 and a flying capacitor, forming three levels, wherein two ends of the flying capacitor are respectively connected to the midpoints of Q1 and Q3 and the midpoints of Q2 and Q4, Q1 and Q2 are complementary turned on, and Q3 and Q4 are complementary turned on; a Boost unit includes switch tubes Q5 and Q6, Q5 and Q6 are complementary turned on, forming two levels; two ends of an intermediate filter inductor are respectively connected to the midpoints of a Buck unit bridge arm and the midpoints of a Boost unit bridge arm, an output filter capacitor is connected to two ends of a load, and a control circuit includes an output voltage stabilization module with a flying capacitor voltage control, a level calculation module, a valley current control module, and a phase shift control signal generation module;

[0029] The output voltage stabilization module with flying capacitor voltage control is used to realize output voltage control and flying capacitor voltage control, and obtain drive signals of flying capacitor charging cycle switch tubes Q3 and Q4 and drive signals of flying capacitor discharging cycle switch tubes Q1 and Q2;

[0030] The level calculation module is used to calculate v A =V in The on-time signal V time_1 , and obtain the driving signals of the flying capacitor discharge cycle switch tubes Q1 and Q2 and the driving signals of the flying capacitor charge cycle switch tubes Q3 and Q4;

[0031] The valley current control module is used to ensure that the switch tube can achieve the negative current required for soft switching. zvs , and obtain the driving signals of the switch tubes Q5 and Q6;

[0032] The phase shift control signal generating module is used to calculate the phase shift signal V of the phase difference between the switching tubes Q1 and Q5 at the time of opening. θ , and obtain the phase difference between the turn-on times of the switch tubes Q1 and Q5.

[0033] In the above-mentioned output voltage regulation module with flying capacitor voltage control, the output voltage sampling value v is regulated by the output voltage regulator. os With a given voltage reference V o_ref By comparison, the closed-loop output signal v of the output voltage regulator is obtained. r , the flying capacitor voltage controller samples the flying voltage v flys With v ins / 2, and the closed-loop output Δv of the flying capacitor voltage controller is obtained. r ;

[0034] v r With Δv r After proportional addition, it is added to the sawtooth wave v saw The output of comparator 1 and clock CLKa are sent to RS trigger 1. The positive output signal of RS trigger 1 is the driving signal of switch tube Q3, and its negative signal is the driving signal of switch tube Q4.

[0035] v r With Δv r After subtracting the same proportion, the sawtooth wave v saw The output of comparator 2 and clock CLKb are sent to RS trigger 2. The positive output signal of RS trigger 2 is the driving signal of switch tube Q1, and its negative signal is the driving signal of switch tube Q2.

[0036] The pulse frequency of CLKa and CLKb is a sawtooth wave vsaw The frequency is half that of CLKa, and the phase difference between CLKb and CLKb is 180°.

[0037] In the above level calculation module, v os and input voltage v ins After proportional subtraction in subtractor 1, the output of subtractor 1, v ins With v r Send to multiplier 1 for multiplication and division operations; os and v ins After proportional subtraction in subtractor 2, the output of subtractor 1, v ins With V θ The outputs of multiplier 1 and multiplier 2 are sent to adder 1 and added to get v A =V in The on-time signal V time_1 , V time_1 With sawtooth wave v saw The output of comparator 3 and CLKa are sent to RS trigger 3 for comparison; the output of comparator 3 and CLKb are sent to RS trigger 4, the positive output signal of RS trigger 3 is the driving signal of switch tube Q1, and its inverted signal is the driving signal of switch tube Q2; the output of comparator 3 and CLKb are sent to RS trigger 4, the positive output signal of RS trigger 4 is the driving signal of switch tube Q3, and its inverted signal is the driving signal of switch tube Q4; V time_1 The formula is as follows;

[0038]

[0039] In the above valley current control module, the inductor current sampling value i Lc , change i Lc The negative current reference -I required to ensure soft switching of the switch tubes Q1, Q3, and Q6 ZVS Sent to comparator 4 for comparison, when i Lc Down to -I ZVS When the comparator 4 outputs the shutdown signal v comp Jump high level; v comp The output of CLKa and CLKb is sent to RS trigger 5 through the output of the OR gate and CLK2. The positive output signal of RS trigger 5 is the driving signal of switch tube Q5, and its negative signal is the driving signal of switch tube Q6.

[0040] The above-mentioned phase shift control signal generating module includes a PDCM mode phase shift angle calculating unit, a PCRM mode phase shift angle calculating unit and a phase shift pulse generating unit;

[0041] The PDCM mode phase shift angle calculation unit includes a subtractor 3, a multiplier 3 and an adder 2, v osand v ins After proportional subtraction in subtractor 3, the output of subtractor 3, v os With v r The result of the multiplication and division operation is sent to the multiplier 3, and the minimum phase shift angle limit D c_max V M After adding by adder 2, the phase shift angle V in PDCM mode is obtained. θ_PDCM ;

[0042] The PCRM mode phase shift angle calculation unit includes adders 3, 4, 5 and a single-pole three-throw switch; adders 3, 4 and 5 are respectively used to perform approximate calculations of the phase shift angle under the PCRM mode under different input-output voltage relationships; the single-pole three-throw switch is used to determine the input-output voltage relationship, and the selection signal of the single-pole three-throw switch is determined by v ins and v os After comparison by comparator 6 and v ins / 2 and v os After comparison by comparator 5, the outputs of comparator 5 and comparator 6 are logically judged by logic gates to obtain selection signal numbers 1 to 3; the phase shift angle V in PCRM mode is finally output through a single-pole triple-throw switch. θPCRM , V θPDCM and V θPCRM After the diode is selected, the final phase shift signal V is obtained. θ Input phase shift pulse generating unit;

[0043] The phase-shift pulse generating unit includes a comparator 7 and its peripheral circuits, which are used to θ The resulting phase shift angle D θ The falling edge is extracted as the clock signal CLK2.

[0044] The above V θ_PDCM The calculation formula is as follows:

[0045]

[0046] Where D c_max Indicates the minimum phase shift angle limit for achieving soft switching.

[0047] V θPCRM The calculation formula is as follows:

[0048]

[0049] In the formula, a1, b1, c1, a2, b2, c2, a3, b3, c3 are all constants, V M Represents sawtooth wave v saw The amplitude, L c Indicates the inductance value, T s Indicates the cycle size, IZVS represents the negative current reference, and k represents the sampling factor of the input and output voltages.

[0050] A control method for a multi-level Buck-Boost converter comprises the following steps:

[0051] Step 1: Sample the output voltage to get v os And with a given voltage reference V o_ref For comparison, the output voltage is stabilized by closed-loop regulation of the output voltage regulator;

[0052] Sampling the flying voltage to get v flys And with a given voltage reference v ins / 2 for comparison, and the flying capacitor voltage is stabilized by the flying capacitor voltage controller;

[0053] The output of the output voltage regulator is proportionally added to the output of the flying capacitor voltage controller to obtain the driving signal of the flying capacitor charging cycle switch tubes Q3 and Q4;

[0054] The output of the output voltage regulator is proportionally subtracted from the output of the flying capacitor voltage controller to obtain the driving signals of the flying capacitor discharge period switch tubes Q1 and Q2;

[0055] Step 2: Sample the output voltage and input voltage to get v os and v ins , respectively, with the closed-loop output v of the output voltage regulator r and the phase shift signal V θ , after proportional operation, we get v A =V in The on-time signal V time_1 , used to control the driving signals of the flying capacitor discharge cycle switch tubes Q1 and Q2 and the driving signals of the flying capacitor charge cycle switch tubes Q3 and Q4;

[0056] Step 3: Sample the intermediate filter inductor current to obtain the intermediate filter inductor current sampling value i Lc and the negative current reference -I required to ensure soft switching of the switch tubes Q1, Q3, and Q6 zvs For comparison, when i Lc Linear decrease to -I zvs When the switch tube Q5 is turned off, the drive signals of the switch tubes Q5 and Q6 are obtained;

[0057] Step 4: Sample the input voltage and output current to get v ins and i os , calculate the phase shift signal V representing the phase difference between the switch tubes Q1 and Q5 when they are turned on θ , controls the phase difference between the turn-on times of the switch tubes Q1 and Q5.

[0058] The control circuit and control method are not limited to the multi-level Buck-Boost converter with m=2 and n=1, and the control method can be adopted and promoted for any m or n multi-level Buck-Boost converter; the control circuit for any m or n multi-level Buck-Boost converter is characterized by: an output voltage stabilization module with flying capacitor voltage control, a valley current control module, a level calculation module and a phase shift control signal generation module;

[0059] The output voltage regulator module with flying capacitor voltage control is used to realize the control of output voltage and flying capacitor voltage. The output voltage regulator compares the output voltage sampling with the given voltage reference to obtain the closed-loop output signal v of the output voltage regulator. r , the flying capacitor voltage controller compares the flying capacitor voltage sampling value with the flying capacitor voltage reference, and obtains the closed-loop output Δv of (m+n-2) flying capacitor voltage controllers rL1 , Δv rL2 ...Δv rL(m-1) and Δv rR1 , Δv rR2 ...Δv rR(n-1) ; v r With Δv rL1 , Δv rL2 ...Δv rL(m-1) Proportional addition and subtraction are used to correct the duty cycle of the Buck unit switch tube. r With Δv rR1 , Δv rR2 ...Δv rR(n-1) Proportional addition and subtraction are used to correct the duty cycle of the Boost unit switch tube to achieve output voltage control and flying capacitor voltage regulation;

[0060] The valley current control module is used to ensure that the switch tube can achieve the required negative current -I zvs , through the valley current control module, the inductor current sampling value i Lc , change i Lc To ensure the switch Q L1 , Q L3 ...Q L(2m-1) and Q R2 , Q R4 ...Q R2n Negative current reference required to achieve soft switching -I ZVS Sent to the comparator for comparison, when i Lc Down to -I ZVS When the switch tube Q is turned off R1 , Q R3 ...Q R(2n-1) ;

[0061] The level calculation module is used to calculate the minimum level combination to achieve inductor current waveform modulation Judgment of and calculation of conduction time;

[0062] The phase shift control signal generation module is used to calculate the phase difference between the Buck unit and the Boost unit when the switch tube is turned on. θ , and obtain the phase difference when the switch tube is turned on.

[0063] The level calculation module and the phase shift control signal generation module jointly play the role of reducing the ripple and effective value of the inductor current.

[0064] The present invention has the following beneficial effects:

[0065] The present invention proposes a multi-level Buck-Boost converter topology structure, which is universal and includes a three-level structure in the prior art, and can obtain any level form of the multi-level Buck-Boost converter according to the input and output voltage levels.

[0066] The present invention adopts a multi-level structure, which is beneficial to reducing the voltage stress of the switch tube, so that the converter can be better applied to high-voltage and high-power occasions;

[0067] At the same time, by utilizing the new control freedom brought by the multi-level structure, the present invention proposes a soft switching modulation strategy suitable for a multi-level Buck-Boost converter. This modulation strategy utilizes the level combination brought by the multi-level structure to modulate the inductor current waveform. On the basis of realizing soft switching of all switch tubes within the entire domain, it can further reduce the pulsation and effective value of the inductor current, which is beneficial to improving the power density of the converter.

[0068] The present invention designs a control circuit and a control method for realizing the above soft switch modulation strategy. The control method is as follows: by sampling the inductor current i Lc The negative current reference required to achieve soft switching -I ZVS Comparison, control the valley current to achieve soft switching of all switches; phase shift control signal D θ The level calculation unit is used to reduce the inductor current ripple and effective value; the output voltage regulator and the flying capacitor controller realize the control of the output voltage and the flying capacitor voltage through proportional calculation, and realize the decoupling of the two voltage loops. The control circuit structure is simple and reliable, and can ensure smooth switching in different working modes. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1a It is a topology structure form 1 of a multi-level Buck-Boost converter;

[0070] Figure 1b It is a topology structure form 2 of a multi-level Buck-Boost converter;

[0071] Figure 2a For existence The inductor current waveform diagram;

[0072] Figure 2b For any The inductor current waveform diagram;

[0073] Figure 2c For any The inductor current waveform diagram;

[0074] Figure 2d In other cases, it does not exist and exist simultaneously and The inductor current waveform diagram;

[0075] Figure 3 It is a multi-level Buck-Boost converter topology with m=2 and n=1;

[0076] Figure 4a The converter in the present invention is V o >V in Schematic diagram of the inductor current waveform changing with load when ;

[0077] Figure 4b The converter in the present invention is V in / 2≤V o ≤V in Schematic diagram of the inductor current waveform changing with load when ;

[0078] Figure 4c The converter in the present invention is V o <V in Schematic diagram of the inductor current waveform changing with load when / 2;

[0079] Figure 5 is an overall block diagram of a multi-level Buck-Boost converter control circuit in an embodiment of the present invention;

[0080] Figure 6a This is a simulation waveform diagram of the present invention when the input voltage is 300V under full load;

[0081] Figure 6b This is a simulation waveform diagram when the input voltage is 600V under full load in the present invention;

[0082] Figure 6c This is a simulation waveform diagram of the present invention when the input voltage is 900V under full load;

[0083] Figure 7a It is a simulation waveform diagram of the present invention when the input voltage is 600V and jumps from 10% load-full load-10% load;

[0084] Figure 7b It is a simulation waveform diagram of the input voltage jumping from 300V-900V-300V when fully loaded in the present invention. DETAILED DESCRIPTION

[0085] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0086] A multi-level Buck-Boost converter disclosed in an embodiment of the present invention, Figure 1a and Figure 1b There are two types of multi-level Buck-Boost converter topologies;

[0087] The multi-level Buck-Boost converter consists of a Buck unit, a Boost unit, an intermediate filter inductor and an output filter capacitor; the Buck unit consists of 2m switch tubes Q L1 , Q L2 ...Q L2m , and (m-1) flying capacitors C fL1 , C fL2 ……C fL(m-1) , forming (m+1) levels; flying capacitor C fL(m-1) The two ends of Q L2m The drain and Q L(2m-1) The source of the switch tube Q L1 With Q L2 Complementary conduction, Q L3 With Q L4 Complementary conduction...Q L(2m-1) With Q L2m Complementary conduction; the Boost unit consists of 2n switch tubes Q R1 , Q R2 ...Q R2n , and (n-1) flying capacitors C fR1 , C fR2 ……C fR(n-1) , forming (n+1) levels. Flying capacitor C fR(n-1) The two ends of R2n The drain and Q R(2n-1) The source of the switch tube Q R1 With Q R2 Complementary conduction, Q R3 With Q R4 Complementary conduction...Q R(2n-1) With Q R2ncomplementary conduction; the intermediate filter inductor is respectively connected to the midpoint A of the Buck unit bridge arm and the midpoint B of the Boost unit bridge arm to store and transfer energy; the output filter capacitor is connected to both ends of the load to filter out the switching frequency ripple; according to an embodiment of the present invention, m and n of the Buck unit and the Boost unit are any positive integers, so the universal multi-level Buck-Boost converter can obtain a topology structure with any level combination.

[0088] The embodiment of the present invention discloses a soft switching modulation strategy for a multi-level Buck-Boost converter to achieve the Q L1 , Q L3 ...Q L(2m-1) and Q R2 , Q R4 ...Q R2n The soft switch needs to ensure that the inductor current is too negative before the switch is turned on, so that the junction capacitance of the switch is discharged to zero and the reverse parallel diode is naturally turned on. The magnitude of the negative current required to be achieved is defined as -I ZVS ; To realize the switch tube Q L2 , Q L4 ...Q L2m and Q R1 , Q R3 ...Q R(2n-1) For soft switching, it is necessary to ensure that the inductor current is positive before the switch tube is turned on, discharge the junction capacitance of the switch tube to zero so that its reverse parallel diode is naturally turned on, and define the size of the positive current required to be achieved as I ZVS ; Figure 2 is a waveform diagram of the inductor current under the soft switching modulation strategy, and the modulation strategy includes the following steps;

[0089] Step 1: According to the on / off status of the Buck unit switch tube, the bridge arm midpoint voltage v is obtained. A Can be V in , 0; According to the on-off status of the Boost unit switch tube, the bridge arm midpoint voltage v is obtained B Can be V o , 0, where V in is the input voltage, V o is the output voltage;

[0090] Step 2: Based on the bridge arm midpoint voltage v A and v B The voltage across the inductor can be obtained AB There are m×n combinations, where v AB Can be divided into four situations: 1. v B =0,v A ≠0, then v AB Can be equal to V in, At this time, under any load condition, the inductor current i Lc Linear increase; 2. v A =0,v B ≠0, then v AB Can be equal to -V o , At this time, under any load condition, the inductor current i Lc Linear decrease; 3. v A =0,v B =0, then v AB =0, the inductor current remains unchanged; 4. v A ≠0, v B ≠0, then Where 0<m i ≤m,0<n i ≤n, and m i and n i All are positive integers, and the inductor current increases or decreases linearly;

[0091] Step 3: To increase the ability to transfer energy to the load, at the beginning of each cycle, the inductor current is set at V in The slope rises linearly; then the inductor current in the middle section increases with The slope rises or falls linearly; finally, the inductor current is -V o The slope decreases linearly until it drops to -I ZVS In order to reduce the inductor current ripple, v AB =0 modulates the inductor current waveform to maintain -I ZVS Soft switching conditions;

[0092] If the above exists Then The inductor current in the middle section is modulated. At this time, the inductor current in the middle section remains unchanged. The inductor current waveform is as follows: Figure 2a As shown;

[0093] If any Then The minimum level combination modulates the inductor current waveform. At this time, the inductor current in the middle section rises linearly. The inductor current waveform is shown in the figure below. Figure 2b As shown;

[0094] If any Likewise The smallest level combination modulates the inductor current waveform. At this time, the inductor current in the middle section decreases linearly. The inductor current waveform is shown in the figure below. Figure 2c As shown;

[0095] In other cases, there is no and exist simultaneously and When using and The level combination with the smallest absolute value modulates the inductor current waveform at the same time. At this time, the inductor current waveform in the middle section first rises linearly and then drops linearly. The inductor current waveform is shown in the figure below: Figure 2d shown.

[0096] The embodiment of the present invention discloses a control method for a multi-level Buck-Boost converter. According to the embodiment of the present invention, the multi-level Buck-Boost converter is set to have m=2, n=1, Figure 3 It is a multi-level Buck-Boost converter topology with m=2 and n=1;

[0097] The converter includes a three-level Buck unit, a two-level Boost unit, an intermediate filter inductor and an output filter capacitor; the three-level Buck unit includes four switch tubes Q1, Q2, Q3, Q4 and a flying capacitor, wherein the two ends of the flying capacitor are respectively connected to the midpoints of Q1 and Q3 and the midpoints of Q2 and Q4, Q1 and Q2 are complementary turned on, and Q3 and Q4 are complementary turned on; the two-level Boost unit includes switch tubes Q5 and Q6, Q5 and Q6 are complementary turned on; the two ends of the intermediate filter inductor are respectively connected to the midpoints of the bridge arms of the three-level Buck unit and the midpoints of the bridge arms of the two-level Boost unit, and the output filter capacitor is connected to the two ends of the load;

[0098] The control method includes four control variables: the duty cycle D of the switch tube Q1 y1 , the duty cycle D of the switch tube Q3 y2 , the duty cycle D of the switch tube Q5 y3 The phase difference between the opening time of Q1 and Q5 is defined as the phase shift angle D θ . Control degree of freedom D y1 It is used to control the switching action of the switch tube of Q1, and its inverted signal is used to control the switching action of the switch tube of Q2. The control degree of freedom D y2 It is used to control the switching action of the switch tube of Q3, and its inverted signal is used to control the switching action of the switch tube of Q4. Control freedom D y3 It is used to control the switching action of the switch tube of Q5, and its inverted signal is used to control the switching action of the switch tube of Q6. Control freedom D θ Used to control the phase difference between the opening time of the switch tubes Q1 and Q5;

[0099] To achieve soft switching of the switch tubes Q1, Q3 and Q6, it is necessary to ensure that the inductor current is over-negative before the switch tube is turned on, discharge the junction capacitance of the switch tube to zero, and make its reverse parallel diode naturally turn on. The magnitude of the negative current required to achieve is defined as -I ZVSTo achieve soft switching of the switch tubes Q2, Q4 and Q5, it is necessary to ensure that the inductor current is positive before the switch tube is turned on, discharge the junction capacitance of the switch tube to zero, and make its reverse parallel diode naturally turn on. The magnitude of the positive current required to achieve this is defined as I ZVS The control method for realizing soft switching of a multi-level Buck-Boost converter includes:

[0100] Step 1: Sample the output voltage v os And with a given voltage reference V o_ref For comparison, the output voltage regulator is closed-loop regulated to stabilize the output voltage; the flying voltage v is sampled flys And with a given voltage reference v ins / 2 is compared, and the flying capacitor voltage is stabilized by the flying capacitor voltage controller; the output of the output voltage regulator is proportionally added to the output of the flying capacitor voltage controller, and the driving signals of the flying capacitor charging cycle switch tubes Q3 and Q4 can be obtained to obtain the duty cycle D of the flying capacitor charging cycle switch tube Q3 y2 ; Subtract the output of the output voltage regulator from the output of the flying capacitor voltage controller in proportion to obtain the driving signals of the flying capacitor discharge cycle switch tubes Q1 and Q2, and obtain the duty cycle D of the flying capacitor discharge cycle switch tube Q1 y1 ;

[0101] Step 2: Sample the output voltage v os and input voltage v ins , and the closed-loop output of the output voltage regulator v r and the phase shift signal V θ , after proportional operation, we get 1 level (v A =V in ) of the conduction time signal V time_1 This signal controls the driving signals of the flying capacitor discharge cycle switch tubes Q1 and Q2 and the driving signals of the flying capacitor charging cycle switch tubes Q3 and Q4, that is, this signal controls the duty cycle D of the flying capacitor discharge cycle switch tube Q1. y1 And the duty cycle D of the flying capacitor charging cycle switch Q3 y2 ;

[0102] Step 3: Sample the inductor current i Lc and the negative current reference -I required to ensure soft switching of the switch tubes Q1, Q3, and Q6 zvs For comparison, when i Lc Linear decrease to -I zvs When the switch tube Q5 is turned off, the drive signals of the switch tubes Q5 and Q6 are obtained, and the duty cycle D of the switch tube Q5 is obtained. y3 , ensuring soft switching of Q1, Q3 and Q6;

[0103] Step 4: Sample the input voltage v ins With the output current i os , perform approximate calculations to obtain the phase shift signal V representing the phase difference between the switch tubes Q1 and Q5 at the time of their turn-on. θ , and obtain the phase difference D at the turn-on time of the control switch tubes Q1 and Q5 θ , control the phase difference between the turn-on times of the switch tubes Q1 and Q5 to ensure soft switching of Q2, Q4 and Q5.

[0104] The output of the output voltage regulator is added or subtracted in the same proportion as the output of the flying capacitor voltage controller.

[0105] Rated input voltage V in and rated output voltage V o With duty cycle D y1 , D y2 and D y3 The relationship between them is:

[0106]

[0107] From this relationship, we can see that the relationship between input and output is only related to D y1 , D y2 and D y3 Under the same input, output and load, adjust different D θ and D y1 and D y2 The proportional relationship can satisfy the premise that the inductor current pulsation is minimized under the premise of realizing soft switching of the six switch tubes; in the embodiment, the specific D θ and D y1 and D y2 The proportional relationship is as follows:

[0108] Approximate phase shift angle D in PCRM mode θ The expression is:

[0109]

[0110] Phase shift angle D in PCRM mode θ The expression is:

[0111]

[0112] In the formula, a1, b1, c1, a2, b2, c2, a3, b3, c3 are all constants, V o Represents the output voltage, V in Indicates input voltage, v os Indicates the output voltage sampling value, v ins Indicates the input voltage sampling value, I ZVS Represents the negative current reference, Lc Indicates the inductance value, T s represents the cycle size, k represents the sampling coefficient of the input and output voltages, V M Represents sawtooth wave v saw The amplitude, v r represents the voltage regulator output;

[0113] FIG4 is a diagram showing the transition process of the converter from PCRM mode to PDCM mode at different input and output voltages;

[0114] D y1 and D y2 The proportional relationship is as follows:

[0115]

[0116] This relationship represents the flying capacitor discharge cycle D y1 and D y2 The proportional relationship between the flying capacitor charging cycle D y1 and D y2 The proportional relationship duality;

[0117] Since the above expression is simple and linear, the calculation of the expression can be implemented by a proportional addition circuit constructed by a digital controller DSP, a microprocessor MCU, a field programmable logic device FPGA or an operational amplifier of an analog circuit.

[0118] The embodiment of the present invention discloses a control circuit of a multi-level Buck-Boost converter; the present invention adopts an analog control circuit as an example, and its principle schematic diagram is shown as follows: Figure 5 As shown, the circuit structure of the multi-level Buck-Boost converter is as follows Figure 3 As shown, the control circuit mainly includes four components: an output voltage stabilization module with flying capacitor voltage control, a level calculation module, a valley current control module and a phase shift control signal generation module;

[0119] (I) Output voltage regulator module with flying capacitor voltage control

[0120] The output voltage stabilization module with flying capacitor voltage control is used to realize the control of output voltage and flying capacitor voltage, and obtain the driving signals of flying capacitor charging cycle switch tubes Q3 and Q4 and the driving signals of flying capacitor discharging cycle switch tubes Q1 and Q2;

[0121] By sampling the output voltage v os With a given voltage reference V o_ref By comparison, the closed-loop output signal v of the output voltage regulator (composed of operational amplifier EA1 and its peripheral circuit) is obtained. r , sampling flying voltage v flysAnd with a given voltage reference v ins / 2, and the closed-loop output Δv of the flying capacitor voltage controller (composed of operational amplifier EA2 and its peripheral circuits) is obtained. r ; Output voltage regulator output v r The output Δv of the flying capacitor voltage controller r After proportional addition, it is added to the sawtooth wave v saw The output of the comparator 1 is compared with the output of the comparator 1, and the output of the comparator 1 and the CLKa are sent to the RS trigger 1. The positive output signal of the RS trigger 1 is the driving signal of the switch tube Q3, and the negative signal is the driving signal of the switch tube Q4. The output voltage regulator v r The output of the flying capacitor voltage controller after inversion -Δv r After adding in the same proportion to the sawtooth wave v saw The signal is sent to comparator 2 for comparison, and its output and CLKb are sent to RS trigger 2. The positive output signal of RS trigger 2 is the driving signal of switch tube Q1, and its negative signal is the driving signal of switch tube Q2.

[0122] The pulse frequency of CLKa and CLKb is a sawtooth wave v saw The frequency is half that of CLKa, and the phase difference between CLKb and CLKb is 180°.

[0123] (II) Level calculation module

[0124] The level calculation module is used to calculate the 1 level (v A =V in ) of the conduction time signal V time_1 , and obtain the driving signals of the flying capacitor discharge cycle switch tubes Q1 and Q2 and the driving signals of the flying capacitor charge cycle switch tubes Q3 and Q4; by sampling the output voltage v os and the output voltage v ins After proportional subtraction in subtractor 1, its output and input voltage v ins The output signal of the output voltage regulator v r Sent to multiplier 1 for multiplication and division operations; sample output voltage v os and the output voltage v ins After proportional subtraction in subtractor 2, its output and input voltage v ins With the phase shift signal V θ The outputs of multiplier 1 and multiplier 2 are sent to adder 1 and added to get V time_1 , with sawtooth wave v sawThe output is sent to comparator 3 for comparison; its output and CLKa are sent to RS trigger 3, the positive output signal of RS trigger 3 is the driving signal of switch tube Q1, and its negative signal is the driving signal of switch tube Q2; its output and CLKb are sent to RS trigger 4, the positive output signal of RS trigger 4 is the driving signal of switch tube Q3, and its negative signal is the driving signal of switch tube Q4; after subtractors 1 and 2, multipliers 1 and 2 and adder, the final 1 level (v A =V in ) of the conduction time signal V time_1 , V time_1 The formula is as follows;

[0125]

[0126] (III) Valley current control module

[0127] The valley current control module ensures that the switch tube can achieve the required negative current -I zvs , and obtain the driving signals of the switch tubes Q5 and Q6; by sampling the inductor current i Lc , change i Lc The negative current reference -I required to ensure soft switching of the switch tubes Q1, Q3, and Q6 ZVS Sent to comparator 4 for comparison, when i Lc Down to -I ZVS When the comparator 4 outputs the shutdown signal v comp Jump high level; In order to prevent the output of comparator 4 from jumping, the comparator is usually set to a hysteresis comparator. Since the loop width of the hysteresis comparator is narrow, it is approximately considered that when i Lc Down to -I ZVS When the output signal v of comparator 4 comp Will jump high level; v comp The output of CLKa and CLKb is sent to RS trigger 5 through the output of the OR gate and CLK2. The positive output signal of RS trigger 5 is the driving signal of switch tube Q5, and its negative signal is the driving signal of switch tube Q6.

[0128] (IV) Phase shift control signal generation module

[0129] The phase shift control signal generation module is used to calculate the phase shift signal V between the phase difference between the switch tubes Q1 and Q5 when they are turned on. θ , and obtain the phase difference of the switch tubes Q1 and Q5 at the time of opening; the phase shift control signal generating module includes a PDCM mode phase shift angle calculation part, a PCRM mode phase shift angle calculation part and a phase shift pulse generating part;

[0130] The PDCM mode phase shift angle calculation part consists of a subtractor 3, a multiplier 3 and an adder 2. By sampling the output voltage vos and the output voltage v ins After proportional subtraction in subtractor 3, its output and output voltage v os The output signal of the output voltage regulator v r It is sent to multiplier 3 for multiplication and division, and then compared with the minimum phase shift angle limit D c_max V M After adding by adder 2, the phase shift angle V in PDCM mode is obtained. θ_PDCM , V θ_PDCM The calculation formula is as follows:

[0131]

[0132] Where D c_max Indicates the minimum phase shift angle limit for achieving soft switching,

[0133] The PCRM mode phase shift angle calculation part is composed of adder 3, adder 4, adder 5 and single-pole three-throw switch; adders 3, 4, 5 respectively perform approximate calculation of the phase shift angle under the PCRM mode under different input-output voltage relationships; the single-pole three-throw switch determines the input-output voltage relationship, and the selection signal of the single-pole three-throw switch is determined by the sampled input voltage v ins and the output voltage v os After comparison and sampling by comparator 6, half of the input voltage v ins / 2 and the output voltage v os After comparison by comparator 5, the outputs of comparator 5 and comparator 6 are logically judged by logic gates (including AND gates and NOT gates) to obtain selection signal numbers 1 to 3; the phase shift angle V in PCRM mode is finally output through a single-pole triple-throw switch. θ_PCRM , V θ_PCRM The calculation formula is as follows:

[0134]

[0135] Phase shift angle V in PDCM mode θ_PDCM and the phase shift angle V in PCRM mode θ_PCRM After the diode is selected, the final phase shift signal V is obtained. θ (Phase shift signal V θ Take V θ_PCRM and V θ_PDCM The phase shift pulse generating part includes a comparator 7 and its peripheral circuits, which shifts the phase signal V θ The resulting phase shift angle D θ The falling edge is extracted as the clock signal CLK2.

[0136] The control circuit and control method are not limited to multi-level Buck-Boost converters with m=2 and n=1, and the control method can be adopted and promoted for any m or n multi-level Buck-Boost converters; for any m or n multi-level Buck-Boost converter, the control circuit includes an output voltage stabilization module with flying capacitor voltage control, a valley current control module, a level calculation module and a phase shift control signal generation module;

[0137] The output voltage regulator module with flying capacitor voltage control is used to realize the control of output voltage and flying capacitor voltage. The output voltage regulator compares the output voltage sampling with the given voltage reference to obtain the closed-loop output signal v of the output voltage regulator. r , the flying capacitor voltage controller compares the flying capacitor voltage sampling value with the flying capacitor voltage reference, and obtains the closed-loop output Δv of (m+n-2) flying capacitor voltage controllers rL1 , Δv rL2 ...Δv rL(m-1) and Δv rR1 , Δv rR2 ...Δv rR(n-1) ; v r With Δv rL1 , Δv rL2 ...Δv rL(m-1) Proportional addition and subtraction are used to correct the duty cycle of the Buck unit switch tube. r With Δv rR1 , Δv rR2 ...Δv rR(n-1) Proportional addition and subtraction are used to correct the duty cycle of the Boost unit switch tube to achieve output voltage control and flying capacitor voltage regulation;

[0138] The valley current control module is used to ensure that the switch tube can achieve the required negative current -I zvs , through the valley current control module, the inductor current sampling value i Lc , change i Lc To ensure the switch Q L1 , Q L3 ...Q L(2m-1) and Q R2 , Q R4 ...Q R2n Negative current reference required to achieve soft switching -I ZVS Sent to the comparator for comparison, when i Lc Down to -I ZVS When the switch tube Q is turned off R1 , Q R3 ...Q R(2n-1) ;

[0139] The level calculation module is used to calculate the minimum level combination to achieve inductor current waveform modulation Judgment of and calculation of conduction time;

[0140] The phase shift control signal generation module is used to calculate the phase difference between the Buck unit and the Boost unit when the switch tube is turned on. θ , and obtain the phase difference when the switch tube is turned on.

[0141] The level calculation module and the phase shift control signal generation module jointly play the role of reducing the ripple and effective value of the inductor current.

[0142] In order to further illustrate the superiority of the present control method, a simulation example of the present invention is given below.

[0143] According to the 3300W multi-level Buck-Boost converter parameters given in Table 1, m=2, n=1 of the multi-level Buck-Boost converter are selected, and the simulation circuit is built using the saber simulation software. Figures 6a to 6c The simulation waveforms of different input voltages under full load are given; among them, Figure 6a This is the simulation waveform diagram under full load with input voltage of 300V; Figure 6b This is the simulation waveform diagram under full load with input voltage of 600V; Figure 6c This is a simulation waveform diagram under full load with an input voltage of 900V. It can be seen that all switch tubes can achieve ZVS and the inductor current pulsation is small. Figure 7a , Figure 7b The simulation waveforms of load jump and input voltage jump are given, where: Figure 7a The middle one is the simulation waveform diagram of load jump when the input voltage is 600V; Figure 7b This is the simulation waveform of the input voltage jump at full load. It can be seen that the output voltage can be stabilized at 400V and has a faster dynamic response speed.

[0144] Table 1 3300W four-tube Buck-Boost converter simulation parameters

[0145] parameter symbol Numeric parameter symbol Numeric Input voltage <![CDATA[V in ]]> 300～900V Switching frequency <![CDATA[f s ]]> 300kHz Output voltage <![CDATA[V o ]]> 400V Intermediate filter inductor <![CDATA[L c ]]> 15μH Flying Capacitor <![CDATA[C fly ]]> 40μF Output Capacitor <![CDATA[C o ]]> 20μF

[0146] The above are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should be regarded as the protection scope of the present invention.

Claims

1. A multi-level Buck-Boost converter, characterized in that: The converter includes a Buck unit, a Boost unit, an intermediate filter inductor and an output filter capacitor; The Buck unit includes 2m switching tubes Q L1 , Q L2 ...Q L2m 、(m-1) flying capacitors C fL1 , C fL2 ……C fL(m-1) , forming (m+1) levels; flying capacitor C fL(q-1) The two ends of Q L2q The drain and Q L(2q-1) The source of is connected, q is any positive integer less than or equal to m; Q L1 With Q L2 Complementary conduction, Q L3 With Q L4 Complementary conduction, and so on, Q L(2m-1) With Q L2m Complementary conduction; The Boost unit includes 2n switch tubes Q R1 , Q R2 ...Q R2n 、(n-1) flying capacitors C fR1 , C fR2 ……C fR(n-1) , forming (n+1) levels; flying capacitor C fR(p-1) The two ends of Q R2p The drain and Q R(2p-1) The source connection of p is any positive integer less than or equal to n, Q R1 With Q R2 Complementary conduction, Q R3 With Q R4 Complementary conduction, and so on, Q R(2n-1) With Q R2n Complementary conduction; The intermediate filter inductor is connected to the midpoint of the Buck unit bridge arm and the midpoint of the Boost unit bridge arm respectively; the output filter capacitor is connected to both ends of the load; m, n are any positive integers.

2. A multi-level Buck-Boost converter according to claim 1, characterized in that: The soft switching modulation strategy of the converter includes: (1) According to the on-off status of the Buck unit switch tube, the bridge arm midpoint voltage v is obtained A Can be V in , 0, where V in is the input voltage; According to the on-off status of the Boost unit switch tube, the bridge arm midpoint voltage v is obtained. B Can be V o , 0, where V o is the output voltage; (2) By v A and v B Get the voltage v across the intermediate filter inductor AB There are m×n combinations, and v AB There are four situations: 1)v B =0,v A ≠0, then v AB Can be equal to V in , At this time, under any load condition, the intermediate filter inductor current i Lc Linear rise; 2)v A =0,v B ≠0, then v AB Can be equal to -V o , At this time, under any load condition, i Lc Linear decline; 3)v A =0,v B =0, then v AB =0,i Lc remain unchanged; 4)v A ≠0, v B ≠0, then Where 0<m i ≤m,0<n i ≤n, and parameter m i and n i are all positive integers, i Lc Linear increase or linear decrease; (3) At the beginning of each cycle, i Lc V in The slope of the linear rise; then the middle segment i Lc by The slope rises or falls linearly; finally i Lc With -V o The slope decreases linearly until it drops to -I ZVS , with v AB =0 modulates the inductor current waveform to maintain -I ZVS Soft switching condition.

3. A multi-level Buck-Boost converter according to claim 2, characterized in that: to i Lc The modulation method is: like Then For the middle segment i Lc Modulation is performed, at this time the middle segment i Lc remain unchanged; If any Then The smallest level combination for i Lc The waveform is modulated, and the middle segment i Lc Linear rise; If any Likewise The smallest level combination for i Lc The waveform is modulated, and the middle segment i Lc Linear decline; In other cases, there is no and exist simultaneously and When using and The level combination with the smallest absolute value in the Lc The waveform is modulated, and the middle segment i Lc The waveform rises linearly first and then falls linearly.

4. A soft switching modulation control circuit for a multi-level Buck-Boost converter according to any one of claims 2 or 3, characterized in that: For any m, n multi-level Buck-Boost converter, the control circuit includes an output voltage stabilization module with flying capacitor voltage control, a valley current control module, a level calculation module and a phase shift control signal generation module; The output voltage regulator module with flying capacitor voltage control is used to realize the control of output voltage and flying capacitor voltage. The output voltage regulator compares the output voltage sampling with the given voltage reference to obtain the closed-loop output signal v of the output voltage regulator. r , the flying capacitor voltage controller compares the flying capacitor voltage sampling value with the flying capacitor voltage reference, and obtains the closed-loop output Δv of (m+n-2) flying capacitor voltage controllers rL1 , Δv rL2 ...Δv rL(m-1) and Δv rR1 , Δv rR2 ...Δv rR(n-1) ; v r With Δv rL1 , Δv rL2 ...Δv rL(m-1) Proportional addition and subtraction are used to correct the duty cycle of the Buck unit switch tube. r With Δv rR1 , Δv rR2 ...Δv rR(n-1) Proportional addition and subtraction are used to correct the duty cycle of the Boost unit switch tube to achieve output voltage control and flying capacitor voltage regulation; The valley current control module is used to ensure that the switch tube can achieve the required negative current -I zvs , through the valley current control module, the inductor current sampling value i Lc , change i Lc To ensure the switch Q L1 , Q L3 ...Q L(2m-1) and Q R2 , Q R4 ...Q R2n Negative current reference required to achieve soft switching -I ZVS Sent to the comparator for comparison, when i Lc Down to -I ZVS When the switch tube Q is turned off R1 , Q R3 ...Q R(2n-1) ; The level calculation module is used to calculate the minimum level combination to achieve inductor current waveform modulation Judgment of and calculation of conduction time; The phase shift control signal generation module is used to calculate the phase difference between the Buck unit and the Boost unit when the switch tube is turned on. θ , and obtain the phase difference when the switch is turned on; The level calculation module and the phase shift control signal generation module jointly play the role of reducing the ripple and effective value of the inductor current.

5. The soft switching modulation control circuit according to claim 4, characterized in that: For the multi-level Buck-Boost converter with m=2 and n=1, the Buck unit includes four switch tubes Q1, Q2, Q3, Q4 and a flying capacitor, forming three levels, wherein the two ends of the flying capacitor are connected to the midpoints of Q1 and Q3 and the midpoints of Q2 and Q4 respectively, Q1 and Q2 are complementary turned on, and Q3 and Q4 are complementary turned on; the Boost unit includes switch tubes Q5 and Q6, Q5 and Q6 are complementary turned on, forming two levels; The two ends of the intermediate filter inductor are connected to the midpoint of the Buck unit bridge arm and the midpoint of the Boost unit bridge arm respectively, and the output filter capacitor is connected to both ends of the load, which is characterized by: The output voltage stabilization module with flying capacitor voltage control is used to realize output voltage control and flying capacitor voltage control, and obtain driving signals of flying capacitor charging cycle switch tubes Q3 and Q4 and driving signals of flying capacitor discharging cycle switch tubes Q1 and Q2; The level calculation module is used to calculate v A =V in The on-time signal V time_1 , and obtain the driving signals of the flying capacitor discharge cycle switch tubes Q1 and Q2 and the driving signals of the flying capacitor charge cycle switch tubes Q3 and Q4; The valley current control module is used to ensure that the switch tube can achieve the negative current required for soft switching. zvs , and obtain the driving signals of the switch tubes Q5 and Q6; The phase shift control signal generating module is used to calculate the phase difference of the switching tubes Q1 and Q5 at the time of opening the phase shift signal V θ , and obtain the phase difference between the turn-on times of the switch tubes Q1 and Q5.

6. The soft switching modulation control circuit according to claim 5, characterized in that: In the output voltage regulator module with flying capacitor voltage control, the output voltage sampling value v is os With a given voltage reference V o_ref By comparison, the closed-loop output signal v of the output voltage regulator is obtained. r , the flying capacitor voltage controller samples the flying voltage v flys With v ins / 2, and the closed-loop output Δv of the flying capacitor voltage controller is obtained. r ; v r With Δv r After proportional addition, it is added to the sawtooth wave v saw The output of comparator 1 and clock CLKa are sent to RS trigger 1 for comparison. The positive output signal of RS trigger 1 is the driving signal of switch tube Q3, and its negative signal is the driving signal of switch tube Q4. v r With Δv r After subtracting the same proportion, the sawtooth wave v saw The output of comparator 2 and clock CLKb are sent to RS trigger 2. The positive output signal of RS trigger 2 is the driving signal of switch tube Q1, and its negative signal is the driving signal of switch tube Q2. The pulse frequency of CLKa and CLKb is a sawtooth wave v saw The frequency is half that of CLKa, and the phase difference between CLKb and CLKb is 180°.

7. The soft switching modulation control circuit according to claim 5, characterized in that: In the valley current control module, the inductor current sampling value i Lc , change i Lc The negative current reference -I required to ensure soft switching of the switch tubes Q1, Q3, and Q6 ZVS Sent to comparator 4 for comparison, when i Lc Down to -I ZVS When the comparator 4 outputs the shutdown signal v comp Jump high level; v comp The output of CLKa and CLKb is sent to RS trigger 5 through the output of the OR gate and CLK2. The positive output signal of RS trigger 5 is the driving signal of switch tube Q5, and its negative output signal is the driving signal of switch tube Q6.

8. The soft switching modulation control circuit according to claim 5, characterized in that: In the level calculation module, v os And the input voltage sampling value v ins After proportional subtraction in subtractor 1, the output of subtractor 1, v ins With v r Send to multiplier 1 for multiplication and division operations; os and v ins After proportional subtraction in subtractor 2, the output of subtractor 2, v ins With V θ The outputs of multiplier 1 and multiplier 2 are sent to adder 1 and added to get v A =V in The on-time signal V time_1 , V time_1 With sawtooth wave v saw The output of comparator 3 and CLKa are sent to RS trigger 3 for comparison; the output of comparator 3 and CLKb are sent to RS trigger 4, the positive output signal of RS trigger 3 is the driving signal of switch tube Q1, and its inverted signal is the driving signal of switch tube Q2; the output of comparator 3 and CLKb are sent to RS trigger 4, the positive output signal of RS trigger 4 is the driving signal of switch tube Q3, and its inverted signal is the driving signal of switch tube Q4; V time_1 The formula is as follows; 9. The soft switching modulation control circuit according to claim 5, characterized in that: The phase shift control signal generating module includes a PDCM mode phase shift angle calculating unit, a PCRM mode phase shift angle calculating unit and a phase shift pulse generating unit; The PDCM mode phase shift angle calculation unit includes a subtractor 3, a multiplier 3 and an adder 2, v os and v ins After proportional subtraction in subtractor 3, the output of subtractor 3, v os With v r The result of the multiplication and division operation is sent to the multiplier 3, and the minimum phase shift angle limit D c_max V M After adding by adder 2, the phase shift angle V in PDCM mode is obtained. θ_PDCM ; The PCRM mode phase shift angle calculation unit includes adders 3, 4, 5 and a single-pole three-throw switch; adders 3, 4 and 5 are respectively used to perform approximate calculations of the phase shift angle under the PCRM mode under different input-output voltage relationships; the single-pole three-throw switch is used to determine the input-output voltage relationship, and the selection signal of the single-pole three-throw switch is determined by v ins and v os After comparison by comparator 6 and v ins / 2 and v os After comparison by comparator 5, the outputs of comparator 5 and comparator 6 are logically judged by logic gates to obtain selection signal numbers 1 to 3; After the single-pole triple-throw switch, the phase shift angle V in PCRM mode is finally output. θ_PCRM , V θ_PDCM and V θ_PCRM After the diode is selected, the final phase shift signal V is obtained. θ Input phase shift pulse generating unit; Where V θ_PDCM The calculation formula is as follows: Where D c_max Indicates the minimum phase shift angle limit for achieving soft switching; V θ_PCRM The calculation formula is as follows: In the formula, a1, b1, c1, a2, b2, c2, a3, b3, c3 are all constants, V M Represents sawtooth wave v saw The amplitude of i os is the output current sampling value; L c Indicates the inductance value, T s Indicates the cycle size, I ZVS represents the negative current reference, k represents the sampling factor of the input and output voltage, D y1 is the duty cycle of the switch tube Q1. The phase-shift pulse generating unit includes a comparator 7 and its peripheral circuits, which are used to θ The resulting phase shift angle D θ The falling edge is extracted as the clock signal CLK2.

10. A soft switching modulation control method for a multi-level Buck-Boost converter, implemented based on the control circuit according to any one of claims 4 to 9, characterized in that: The control method comprises the following steps: Step 1: Sample the output voltage to get v os And with a given voltage reference V o_ref For comparison, the output voltage is stabilized by closed-loop regulation of the output voltage regulator; Sampling the flying voltage to get v flys And with a given voltage reference v ins / 2 for comparison, and the flying capacitor voltage is stabilized by the flying capacitor voltage controller; The output of the output voltage regulator is proportionally added to the output of the flying capacitor voltage controller to obtain the driving signal of the flying capacitor charging cycle switch tubes Q3 and Q4; The output of the output voltage regulator is proportionally subtracted from the output of the flying capacitor voltage controller to obtain the driving signals of the flying capacitor discharge period switch tubes Q1 and Q2; Step 2: Sample the output voltage and input voltage to get v os and v ins , respectively, with the closed-loop output v of the output voltage regulator r and the phase shift signal V θ , after proportional operation, we get v A =V in The on-time signal V time_1 , used to control the driving signals of the flying capacitor discharge cycle switch tubes Q1 and Q2 and the driving signals of the flying capacitor charge cycle switch tubes Q3 and Q4; Step 3: Sample the intermediate filter inductor current to obtain the intermediate filter inductor current sampling value i Lc and the negative current reference -I required to ensure soft switching of the switch tubes Q1, Q3, and Q6 zvs For comparison, when i Lc Linear decrease to -I zvs When the switch tube Q5 is turned off, the drive signals of the switch tubes Q5 and Q6 are obtained; Step 4: Sample the input voltage and output current to get v ins and i os , calculate the phase shift signal V representing the phase difference between the switching tubes Q1 and Q5 when they are turned on θ , control the phase difference between the switch tubes Q1 and Q5 when they are turned on; For any m, n multi-level Buck-Boost converter, the control method is extended to perform control.

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