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

Abstract

The present invention discloses a multi-level Buck-Boost converter and its soft-switching modulation control circuit and control method. The multi-level Buck-Boost converter has a universal topology that can be used to obtain any level form of the multi-level Buck-Boost converter based on the input and output voltage levels. A soft-switching modulation strategy suitable for the multi-level Buck-Boost converter is also proposed. This strategy can further reduce the pulsation and effective value of the inductor current while achieving soft switching of all switches across the entire domain, thereby improving the power density of the converter. Accordingly, a control circuit and control method are proposed for specifically implementing the above-mentioned soft-switching modulation strategy. The control circuit structure is simple and reliable, and can ensure smooth switching between different operating modes.

Description

Technical Field

[0001] The present 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 applications such as photovoltaic power generation, electric vehicles, and household energy storage. As power requirements increase, voltage levels in these applications are also increasing to improve conversion efficiency. For example, the output voltage of photovoltaic modules in photovoltaic power generation systems has reached 1000V and is trending towards 1500V; the voltage level of electric vehicle battery systems is also transitioning from 400V to 800V.

[0003] The Four Switch Buck-Boost (FSBB) converter has broad application prospects due to its homopolar output voltage, buck-boost functionality, and bidirectional energy transfer. However, the FSBB converter is a two-level topology. Its left-hand bridge arm consists of buck units, subjecting the switches to voltage stress equal to the maximum input voltage; its right-hand bridge arm consists of boost units, subjecting the switches to voltage stress equal to the maximum output voltage. Limited by the voltage ratings of existing switching devices, the FSBB converter is not suitable for applications with high-voltage inputs.

[0004] To reduce the voltage stress on the switching transistors, existing research has proposed three-level six-transistor Buck-Boost converter and symmetrical three-level FSBB converter topologies, employing two-mode interleaved control. However, as voltage levels increase, the application scenarios of these three-level topologies will be limited. Furthermore, their hard-switching control strategy significantly increases switching losses as 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 and provide a multi-level Buck-Boost converter and its soft switching modulation control circuit and control method, and provide a universal multi-level Buck-Boost converter topology suitable for any voltage level and 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, 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 Q L2q The drain and Q L(2q-1) The source connection of 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 switching 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 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 and n are any positive integers.

[0012] To optimize the above technical solutions, 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 increases linearly; 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 to modulate the inductor current waveform and 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 minimum level combination for i Lc The waveform is modulated, and the middle segment i Lc linear rise;

[0026] If any Likewise The minimum 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 first rises linearly 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, wherein the Buck unit includes four switching tubes Q1, Q2, Q3, and Q4 and a flying capacitor, forming three levels, 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, with Q1 and Q2 complementary to each other and Q3 and Q4 complementary to each other; the Boost unit includes switching tubes Q5 and Q6, which are complementary to each other, forming two levels; the two ends of the intermediate filter inductor are respectively connected to the midpoints of the Buck unit bridge arm and the midpoint of the Boost unit bridge arm, and the output filter capacitor is connected to the two ends of the load; the control circuit includes 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;

[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 for flying capacitor charging cycle switch tubes Q3 and Q4 and drive signals for 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 -I 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 difference between 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 moments of the switches Q1 and Q5.

[0033] In the above-mentioned output voltage stabilization 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 value v flys With v ins / 2 to obtain the closed-loop output Δv of the flying capacitor voltage controller. r ;

[0034] v r and Δv r After proportional addition and 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 Q3, and its negative output signal is the driving signal of switch Q4.

[0035] v r and Δv r After subtracting the same proportion from 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 Q1, and its negative output signal is the driving signal of switch 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 the proportional subtraction is performed in subtractor 1, the output of subtractor 1, v ins With v r Send to multiplier 1 for multiplication and division operation; os and v ins After proportional subtraction in subtractor 2, the output of subtractor 1, v ins With V θ Send it to multiplier 2 for multiplication and division operations; send the outputs of multiplier 1 and multiplier 2 to adder 1 and add them 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 Q1, and its negative signal is the driving signal of switch 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 Q3, and its negative signal is the driving signal of switch 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 Descend 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.

[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 is performed in subtractor 3, the output of subtractor 3, v os With v r The result is sent to multiplier 3 for multiplication and division operation, and the result is equal to 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 and output voltage relationships; the single-pole three-throw switch is used to determine the input and 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 the logic gate to obtain the selection signal numbers 1 to 3; the phase shift angle V in PCRM mode is finally output through the single-pole triple-throw switch. θPCRM , V θPDCM and V θPCRM After the diode is selected, the final phase-shift signal V 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 convert V 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] Where 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 cycle switches 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-shifted 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 Linearly decrease to -I zvs When the switch tube Q5 is turned off, the driving 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 that represents the phase difference between the switching tubes Q1 and Q5 when they are turned on θ , controls the phase difference between the turn-on moments of the switch tubes Q1 and Q5.

[0058] The control circuit and control method are not limited to multi-level Buck-Boost converters with m=2 and n=1, and can be applied to any multi-level Buck-Boost converters with m or n. The control circuit for any multi-level Buck-Boost converter with m or n 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 samples the output voltage and compares it 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 to obtain 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 and 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, and v r and 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 negative current required for soft switching -I zvs , through the valley current control module, the inductor current sampling value i Lc , change i Lc and ensure the switch tube 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 Descend to -I ZVS When the switch tube Q is turned off at the same time 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 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 switch tube when they are 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. The topology structure is universal. The topology structure includes the three-level structure form 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 in high-voltage and high-power applications;

[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 uses 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 in the entire range, 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-mentioned soft switching 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 sum level calculation unit is used to reduce inductor current ripple and RMS value. The output voltage regulator and flying capacitor controller control the output voltage and flying capacitor voltage through proportional calculation, decoupling the two voltage loops. This control circuit has a simple and reliable structure and ensures smooth switching between different operating 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 the topology structure form 2 of the 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 1 is an overall block diagram of a multi-level Buck-Boost converter control circuit according to 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 and full load;

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

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

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

[0084] Figure 7b This 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 described in further detail below with reference to the accompanying drawings.

[0086] The embodiment of the present invention discloses a multi-level Buck-Boost converter. Figure 1a and Figure 1b There are two topological structures of multi-level Buck-Boost converters;

[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 switching 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 Q 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 connected to the midpoint A of the Buck unit bridge arm and the midpoint B of the Boost unit bridge arm, respectively, for storing and transferring energy; the output filter capacitor is connected across the load to filter out switching frequency ripple; according to an embodiment of the present invention, wherein m and n of the Buck unit and the Boost unit are any positive integers, 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 Soft switching requires 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 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 the reverse parallel diode is naturally turned on, and define the size of the positive current required to achieve this as I ZVS ; Figure 2 is a diagram of the inductor current waveform under the soft switching modulation strategy, 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 as v 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 rise; 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 Are all positive integers, 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 at 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 to modulate the inductor current waveform and maintain -I ZVS Soft switching conditions;

[0092] If the above 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 minimum 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 falls 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 consists of 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 switching tubes Q1, Q2, Q3, and Q4, and a flying capacitor. 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 conductive, and Q3 and Q4 are complementary conductive. The two-level Boost unit includes switching tubes Q5 and Q6. Q5 and Q6 are complementary conductive. The two ends of the intermediate filter inductor are connected to the midpoints of the three-level Buck unit bridge arm and the midpoints of the two-level Boost unit bridge arm, respectively. 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 moments 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 inverse signal is used to control the switching action of the switch tube of Q2, and the control degree of freedom D y2 It is used to control the switching action of the switch tube of Q3, and its inverse signal is used to control the switching action of the switch tube of Q4. y3 It is used to control the switching action of the switch tube of Q5, and its inverse signal is used to control the switching action of the switch tube of Q6. θ Used to control the phase difference between the turn-on moments of the switches Q1 and Q5;

[0099] To achieve soft switching of the switches Q1, Q3, and Q6, it is necessary to ensure that the inductor current is over-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 is defined as -I ZVSTo achieve soft switching of the switches Q2, Q4, and Q5, it is necessary to ensure that the inductor current is positive before the switch is turned on, discharge the junction capacitance of the switch to zero, and make its reverse-parallel diode naturally conduct. The magnitude of the positive current required is defined as I ZVS A control method for implementing 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 Compare and adjust the output voltage through the closed loop of the output voltage regulator; sample the flying voltage v flys And with a given voltage reference v ins / 2, 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 switches Q3 and Q4 can be obtained to obtain the duty cycle D of the flying capacitor charging cycle switch Q3. y2 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 cycle switches Q1 and Q2, and the duty cycle D of the flying capacitor discharge cycle switch Q1 is obtained. 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-shifted 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 Linearly 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 switching tubes Q1 and Q5 at the time of opening. θ , get the phase difference D when the control switches Q1 and Q5 are turned on θ , controlling the phase difference between the turn-on moments of the switch tubes Q1 and Q5, ensuring soft switching of Q2, Q4 and Q5.

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

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

[0106]

[0107] From this relation, 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 ripple is minimized under the premise of achieving 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] Where a1, b1, c1, a2, b2, c2, a3, b3, c3 are all constants, V o Indicates the output voltage, V in Indicates the input voltage, v os Indicates the output voltage sampling value, v ins Indicates the input voltage sampling value, I ZVS Indicates the negative current reference, Lc Indicates the inductance value, T s Indicates the cycle size, k indicates the sampling coefficient of input and output voltage, V M Represents sawtooth wave v saw The amplitude, v r Indicates the voltage regulator output;

[0113] Figure 4 shows 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 discharge period of the flying capacitor 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 built 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 for a multi-level Buck-Boost converter; the present invention adopts an analog control circuit as an example, and its principle 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 regulator module with flying capacitor voltage control, a level calculation module, a valley current control module and a phase shift control signal generation module;

[0119] (1) Output voltage regulator module with flying capacitor voltage control

[0120] The output voltage regulator module with flying capacitor voltage control is used to realize output voltage control and flying capacitor voltage control, and obtain the driving signals of the flying capacitor charging cycle switch tubes Q3 and Q4 and the driving signals of the 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 circuits) is obtained. r , sampling flying voltage v flysAnd with a given voltage reference v ins / 2 to obtain the closed-loop output Δv of the flying capacitor voltage controller (composed of the operational amplifier EA2 and its peripheral circuits). r ; Output voltage regulator output v r The output Δv of the flying capacitor voltage controller r After proportional addition and 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 output 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 them in the same proportion, they are added 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 output signal is the driving signal of switch tube Q2.

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

[0123] (2) Level calculation module

[0124] The level calculation module is used to calculate the 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 charging 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 Send to multiplier 1 for multiplication and division operation; 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 , and 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 passing through 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] (3) Valley current control module

[0127] The valley current control module ensures that the switch tube can achieve the negative current required for soft switching -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 Descend 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 hysteresis comparator has a narrow loop width, it is approximately considered that when i Lc Descend to -I ZVS When the output signal of comparator 4 is 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 output signal is the driving signal of switch tube Q6.

[0128] (4) Phase shift control signal generation module

[0129] The phase shift control signal generation module is used to calculate the phase difference between the switching tubes Q1 and Q5 at the time of opening the phase shift signal V θ , and obtain the phase difference between the switch tubes Q1 and Q5 at the time of opening; the phase shift control signal generation module includes a PDCM mode phase shift angle calculation part, a PCRM mode phase shift angle calculation part and a phase shift pulse generation 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 The data 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 adders 3, 4, and 5 and a single-pole three-throw switch. Adders 3, 4, and 5 respectively perform approximate calculations of the phase shift angle under different input-output voltage relationships in the PCRM mode. 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 signals 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 θ (Phase-shifted 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 will shift 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 can be applied to any multi-level Buck-Boost converter with m or n. 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 for any multi-level Buck-Boost converter with m or n.

[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 samples the output voltage and compares it 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 to obtain 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 and 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, and v r and 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 negative current required for soft switching -I zvs , through the valley current control module, the inductor current sampling value i Lc , change i Lc and ensure the switch tube 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 Descend to -I ZVS When the switch tube Q is turned off at the same time 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 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 switch tube when they are 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 this 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 The simulation waveform diagram is at an input voltage of 900V and full load. It can be seen that all switching 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 of load jump when the input voltage is 600V; Figure 7b The simulation waveform of the input voltage jump at full load is shown. It can be seen that the output voltage can be stabilized at 400V and has a fast dynamic response speed.

[0144] Table 1 Simulation parameters of a 3300W four-tube Buck-Boost converter

[0145] parameter symbol Numerical parameter symbol Numerical 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 merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions based on the principles of the present invention are within the scope of protection of the present invention. It should be noted that for those skilled in the art, various improvements and modifications that do not depart from the principles of the present invention should be considered within the scope of protection 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 the connection, 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 switching 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, 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; 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 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 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 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 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 increases linearly; 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 to modulate the inductor current waveform and maintain -I ZVS Soft switching condition.

2. The multi-level Buck-Boost converter according to claim 1, wherein: 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 minimum level combination for i Lc The waveform is modulated, and the middle segment i Lc linear rise; If any Likewise The minimum 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 first rises linearly and then falls linearly.

3. A soft switching modulation control circuit for a multi-level Buck-Boost converter according to any one of claims 1 or 2, 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 samples the output voltage and compares it 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 to obtain 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 and 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, and v r and 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 negative current required for soft switching -I zvs , through the valley current control module, the inductor current sampling value i Lc , change i Lc To ensure the switch tube 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 Descend to -I ZVS When the switch tube Q is turned off at the same time 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 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 switch tube when they are turned on. θ , and obtain the phase difference when the switch tube 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.

4. The soft switching modulation control circuit according to claim 3, wherein: For a multi-level Buck-Boost converter with m=2 and n=1, the Buck unit includes four switching tubes Q1, Q2, Q3, and Q4 and a flying capacitor, forming three levels. 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 and Q3 and Q4 are complementary. The Boost unit includes switching tubes Q5 and Q6. Q5 and Q6 are complementary and formed into 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. The characteristics are: 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 for flying capacitor charging cycle switch tubes Q3 and Q4 and drive signals for 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 -I 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 between 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 moments of the switches Q1 and Q5.

5. The soft switching modulation control circuit according to claim 4, 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 value v flys With v ins / 2 to obtain the closed-loop output Δv of the flying capacitor voltage controller. r ; where v ins is the input voltage sampling value; v r and Δv r After proportional addition and 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 Q3, and its negative output signal is the driving signal of switch Q4. v r and Δv r After subtracting the same proportion from 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 Q1, and its negative output signal is the driving signal of switch 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°.

6. The soft switching modulation control circuit according to claim 4, 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 Descend 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.

7. The soft switching modulation control circuit according to claim 4, wherein: In the level calculation module, the output voltage sampling value v os And the input voltage sampling value v ins After the proportional subtraction is performed in subtractor 1, the output of subtractor 1, v ins With v r Send to multiplier 1 for multiplication and division operation; os and v ins After the proportional subtraction is performed in subtractor 2, the output of subtractor 2, v ins With V θ Send it to multiplier 2 for multiplication and division operations; send the outputs of multiplier 1 and multiplier 2 to adder 1 and add them 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 Q1, and its negative signal is the driving signal of switch 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 Q3, and its negative signal is the driving signal of switch Q4; V time_1 The formula is as follows:

8. The soft switching modulation control circuit according to claim 4, wherein: 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, and outputs a voltage sampling value v os And the input voltage sampling value v ins After proportional subtraction is performed in subtractor 3, the output of subtractor 3, v os With v r The result is sent to multiplier 3 for multiplication and division operation, and the result is equal to 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 and output voltage relationships; the single-pole three-throw switch is used to determine the input and 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 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: Where 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; The phase-shift pulse generating unit includes a comparator 7 and its peripheral circuits, which are used to convert V θ The resulting phase shift angle D θ The falling edge is extracted as the clock signal CLK2.

9. 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 3 to 8, characterized in that: The control method includes 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 cycle switches 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-shifted 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 Linearly decrease to -I zvs When the switch tube Q5 is turned off, the driving 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 that represents the phase difference between the switching tubes Q1 and Q5 when they are turned on θ , controls the phase difference between the turn-on moments of the switches Q1 and Q5; For any m, n multi-level Buck-Boost converter, the control method is extended to perform control.

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