Working mode switching method of Buck Boost converter

Abstract

The invention relates to a working mode switching method of a Buck Boost converter. The method comprises the following steps: generating a reference duty ratio based on a sampling current, a sampling voltage and a reference voltage reference value of the Buck Boost converter; obtaining a current working mode, a Buck unit compensation duty ratio and a Boost unit compensation duty ratio of the Buck Boost converter based on the reference duty ratio; generating a Buck unit duty ratio and a Boost unit duty ratio based on the reference duty ratio, the current working mode, the Buck unit compensation duty ratio and the Boost unit compensation duty ratio; and controlling a switching tube of the Buck Boost converter based on the duty ratio of the Buck unit and the duty ratio of the Boost unit so as to realize consistent output voltage gain. According to the invention, voltage gains before and after working mode switching can be consistent, so that the problem of violent voltage fluctuation is solved.

Description

Technical Field

[0001] This invention relates to the field of BuckBoost converters, and more specifically, to a method for switching the operating mode of a BuckBoost converter. Background Technology

[0002] The four-switch buck-boost (FSBB) converter has three operating modes: buck mode, boost mode, and buck-boost mode. When the input voltage changes, the buck-boost converter needs to switch between these three modes to stabilize the output voltage. However, current buck-boost converters' mode switching methods suffer from discontinuous voltage gain before and after mode switching, easily leading to drastic voltage fluctuations. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for switching the operating mode of a BuckBoost converter, which can achieve consistent voltage gain before and after switching the operating mode, thereby solving the problem of drastic voltage fluctuations.

[0004] The technical solution adopted by this invention to solve its technical problem is as follows: A method for switching the operating mode of a BuckBoost converter is constructed, comprising: generating a reference duty cycle based on the sampled current, sampled voltage, and reference voltage value of the BuckBoost converter; obtaining the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle; generating the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle; and controlling the switching transistors of the BuckBoost converter based on the Buck unit duty cycle and the Boost unit duty cycle to achieve consistent voltage gain.

[0005] In the operating mode switching method of the BuckBoost converter described in this invention, the BuckBoost converter includes a first capacitor, a Buck unit, a Boost unit, a second capacitor, and an inductor bridge arm; the first capacitor is connected to a first voltage and the Buck unit, and the second capacitor is connected to a second voltage and the Boost unit; the two ends of the inductor bridge arm are respectively connected to the Buck unit and the Boost unit; the Buck unit includes a first switch and a second switch, and the Boost unit includes a third switch and a fourth switch.

[0006] In the BuckBoost converter operating mode switching method described in this invention, a reference duty cycle is generated based on the sampled current, sampled voltage, and reference voltage reference value of the BuckBoost converter. This includes: using the sampled voltage of the second capacitor as the input of the outer voltage loop of the voltage-current dual closed loop, using the reference voltage reference value as the given value of the outer voltage loop of the voltage-current dual closed loop, and generating the given value of the inner current loop of the voltage-current dual closed loop; using the sampled current of the inductor bridge arm as the input of the inner current loop of the voltage-current dual closed loop, and generating the reference duty cycle.

[0007] In the BuckBoost converter operating mode switching method of the present invention, obtaining the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle includes: when the reference duty cycle is less than or equal to the Buck mode duty cycle, determining that the current operating mode of the BuckBoost converter is Buck mode, and calculating the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Buck mode; when the reference duty cycle is greater than the Buck mode duty cycle and less than or equal to the BuckBoost mode duty cycle, determining that the current operating mode of the BuckBoost converter is BuckBoost mode, and calculating the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the BuckBoost mode; when the reference duty cycle is greater than the BuckBoost mode duty cycle, determining that the current operating mode of the BuckBoost converter is Boost mode, and calculating the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Boost mode. In the operating mode switching method of the BuckBoost converter described in this invention, the calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in Buck mode are: dBuckComp=0; dBoostComp=(2-dMax)*(1-dMax); the calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in BuckBoost mode are: dBuckComp=-(dMin)*(dLoopOut)∈[-dMin,0]; dBoostComp=(1-dMax)*(2-dLoopOut)∈[0,(2-dMax)*(1-dMax)]; the calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in Boost mode are: dBuckComp=-dMin; dBoostComp=0; where dBuckComp represents the Buck unit compensation duty cycle, dBoostComp represents the Boost unit compensation duty cycle, and dMax represents the maximum duty cycle of the switching transistor. dMin represents the minimum duty cycle of the switching transistor, and dLoopOut represents the reference duty cycle; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode; the calculation formula is obtained under the same output voltage gain.

[0008] In the BuckBoost converter operating mode switching method of the present invention, obtaining the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle further includes: obtaining the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle and the dead time duty cycle of the switching transistor; the calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Buck mode are: dBuckComp=0; dBoostComp=(2-dMax+Dd)*(1-dMax+Dd); the calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the BuckBoost mode are: dBu ckComp = -(dMin - Dd) * (dLoopOut - Dd) ∈ [Dd - dMin, 0]; dBoostComp = (1 - dMax + Dd) * (2 - dLoopOut + Dd) ∈ [0, (2 - dMax + Dd) * (1 - dMax + Dd)]; The calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Boost mode are: dBuckComp = Dd - dMin; dBoostComp = 0; where dBuckComp represents the Buck unit compensation duty cycle, dBoostComp represents the Boost unit compensation duty cycle, dMax represents the maximum duty cycle of the switching transistor, Dd represents the dead time duty cycle of the switching transistor, dMin represents the minimum duty cycle of the switching transistor, and dLoopOut represents the reference duty cycle; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode.

[0009] In the method for switching the operating mode of the BuckBoost converter according to the present invention, when the reference duty cycle is less than or equal to the Buck mode duty cycle, it is determined that the current operating mode of the BuckBoost converter is the Buck mode, including: when the reference duty cycle dLoopOut <= dMax, it is determined that the current operating mode of the BuckBoost converter is the Buck mode; when the reference duty cycle is greater than the Buck mode duty cycle and less than or equal to the BuckBoost mode duty cycle, it is determined that the current operating mode of the BuckBoost converter is the BuckBoost mode, including: when the reference duty cycle dMax < dLoopOut <= 1 + dMin, it is determined that the current operating mode of the BuckBoost converter is the BuckBoost mode; when the reference duty cycle is greater than the BuckBoost mode duty cycle, it is determined that the current operating mode of the BuckBoost converter is the Boost mode, including: when the reference duty cycle 1 + dMin < dLoopOut <= 2, it is determined that the current operating mode of the BuckBoost converter is the Boost mode.

[0010] In the method for switching the operating mode of the BuckBoost converter according to the present invention, when the reference duty cycle is less than or equal to the Buck mode duty cycle, it is determined that the current operating mode of the BuckBoost converter is the Buck mode, further including: when the BuckBoost converter switches back from the BuckBoost mode to the Buck mode, when the reference duty cycle dLoopOut <= then, it is determined that the current operating mode of the BuckBoost converter is the Buck mode; and / or when the reference duty cycle is greater than the BuckBoost mode duty cycle, it is determined that the current operating mode of the BuckBoost converter is the Boost mode, further including: when the BuckBoost converter switches from the BuckBoost mode to the Buck mode, when the reference duty cycle < dLoopOut <= 2, it is determined that the current operating mode of the BuckBoost converter is the Boost mode.

[0011] In the buckBoost converter operating mode switching method described in this invention, the buck unit duty cycle and boost unit duty cycle are generated based on the reference duty cycle, the current operating mode, the buck unit compensation duty cycle, and the boost unit compensation duty cycle. This includes: when the current operating mode is buckBoost mode, the calculation formulas for the buck unit duty cycle and the boost unit duty cycle are: dBuck = dLoopOut + dBuckComp ∈ [dMin, dMax]; dBoost = dLoopOut-1 + dBoostComp ∈ [dMin, dMax]; when the current operating mode is buck mode, the calculation formulas for the buck unit duty cycle and the boost unit duty cycle are: dBuck = dLoopOut + dBuckComp mp∈[dMin,dMax]; dBoost=0; When the current operating mode is Boost mode, the calculation formulas for the Buck unit duty cycle and the Boost unit duty cycle are: dBuck=1; dBoost=dLoopOut-1+dBoostComp∈[dMin,dMax]; where dBuck represents the Buck unit duty cycle, dBoost represents the Boost unit duty cycle; dLoopOut represents the base duty cycle, dBuckComp represents the Buck unit compensation duty cycle in the current operating mode, dBoostComp represents the Boost unit compensation duty cycle in the current operating mode; dMax represents the maximum duty cycle of the switching transistor, Dd represents the dead time duty cycle of the switching transistor, dMin represents the minimum duty cycle of the switching transistor; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode.

[0012] In the BuckBoost converter operating mode switching method of the present invention, controlling the switching transistors of the BuckBoost converter based on the duty cycle of the Buck unit and the duty cycle of the Boost unit to achieve voltage gain consistency includes: generating a first switching transistor modulation signal and a second switching transistor modulation signal based on the Buck unit duty cycle and a triangular carrier signal, wherein the first switching transistor modulation signal is out of phase with the second switching transistor modulation signal; generating a third switching transistor modulation signal and a fourth switching transistor modulation signal based on the Boost unit duty cycle and the triangular carrier signal, wherein the third switching transistor modulation signal is out of phase with the fourth switching transistor modulation signal; and controlling the first switching transistor, the second switching transistor, the third switching transistor, and the fourth switching transistor based on the first switching transistor modulation signal, the second switching transistor modulation signal, the third switching transistor modulation signal, and the fourth switching transistor modulation signal to achieve voltage gain consistency.

[0013] In the BuckBoost converter operating mode switching method described in this invention, the voltage gain Where M represents voltage gain, Vout represents output voltage, Vin represents input voltage, dBuck represents the duty cycle of the Buck unit, and dBoost represents the duty cycle of the Boost unit.

[0014] The BuckBoost converter operating mode switching method of the present invention generates a reference duty cycle based on the sampled current, sampled voltage, and reference voltage of the BuckBoost converter; obtains the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle; generates the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle; and controls the switching transistors of the BuckBoost converter based on the Buck unit duty cycle and the Boost unit duty cycle. Because it obtains the current operating mode of the BuckBoost converter based on the reference duty cycle, and generates the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle, the operating mode switching and voltage judgment are decoupled, ensuring a smooth switching process and consistent voltage gain before and after switching, and preventing drastic voltage fluctuations before and after switching.

[0015] Another technical solution adopted by the present invention to solve its technical problem is: constructing a BuckBoost converter control system, including a BuckBoost converter, a sampling device, a reference duty cycle device, a nonlinear controller, a duty cycle generation device, and a driving device; the sampling device is used to sample the sampling current and sampling voltage of the BuckBoost converter; the reference duty cycle device is used to generate a reference duty cycle based on the sampling current, sampling voltage, and reference voltage reference value of the BuckBoost converter; the nonlinear controller is used to obtain the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle; the duty cycle generation device is used to generate the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle; the driving device is used to control the switching transistors of the BuckBoost converter based on the Buck unit duty cycle and the Boost unit duty cycle to achieve consistent voltage gain.

[0016] The operating mode system of the BuckBoost converter implementing the present invention generates a reference duty cycle based on the sampled current, sampled voltage, and reference voltage of the BuckBoost converter; obtains the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle; generates the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle; and controls the BuckBoost converter based on the Buck unit duty cycle and the Boost unit duty cycle. The switching transistors of the OOTS converter obtain the current operating mode of the BuckBoost converter based on the reference duty cycle, and generate the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle. Because the switching transistors are controlled by superimposing the compensation duty cycle onto the reference duty cycle, the actual circuit switching transistor on / off control is more precise, that is, the output voltage is smoothly controlled. Therefore, the operating mode switching and voltage judgment are decoupled, which can ensure a smooth switching process and consistent voltage gain before and after the switching, and can prevent drastic voltage fluctuations before and after the switching. Attached Figure Description

[0017] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings: Figure 1This is a flowchart of the operating mode switching method of the BuckBoost converter of the present invention; Figure 2 This is a circuit diagram of a BuckBoost converter to which the BuckBoost converter operating mode switching method of the present invention is applicable; Figure 3 This is a circuit diagram of another BuckBoost converter to which the BuckBoost converter operating mode switching method of the present invention is applicable; Figure 4 This is a block diagram of the voltage and current dual closed loop to which the BuckBoost converter operating mode switching method of the present invention is applicable. Figure 5 This is a schematic diagram illustrating the BuckBoost converter operating mode determination, Buck unit compensation duty cycle and Boost unit compensation duty cycle calculation process of the BuckBoost converter operating mode switching method of the present invention. Figure 6 This is a schematic diagram of the Buck cell duty cycle, the Boost cell duty cycle generation steps, and the switching transistor control steps of the BuckBoost converter operating mode switching method of the present invention. Figure 7 This is a schematic diagram of another operating mode determination process of the BuckBoost converter in the BuckBoost converter operating mode switching method of the present invention; Figure 8 This is a schematic diagram illustrating the calculation process of the Buck unit compensation duty cycle and the Boost unit compensation duty cycle of the BuckBoost converter in the BuckBoost converter operating mode switching method of the present invention. Figure 9 This is a schematic diagram showing the approximate changes in the duty cycle of Buck and Boost cells under different operating modes, without considering the effect of dead time. Figure 10A and Figure 10B Output voltage test diagram of BuckBoost converter after adopting the BuckBoost converter operating mode switching method of the present invention; Figure 11 This is a block diagram of the BuckBoost converter control system of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] Figure 1 This is a flowchart of the working mode switching method of the BuckBoost converter of the present invention. Figure 2 This is a circuit diagram of a BuckBoost converter to which the working mode switching method of the BuckBoost converter of the present invention is applicable. Figure 3 This is a circuit diagram of another BuckBoost converter to which the BuckBoost converter operating mode switching method of the present invention is applicable. For example... Figure 2 As shown, the BuckBoost converter includes a first capacitor C1, a Buck unit 100, a Boost unit 200, a second capacitor C2, and an inductor bridge arm L1. The first capacitor C1 is connected to a first voltage Vin and the Buck unit 100, and the second capacitor C2 is connected to a second voltage Vout and the Boost unit 200. The two ends of the inductor bridge arm L1 are respectively connected to the Buck unit 100 and the Boost unit 200. Preferably, the Buck unit 100 includes switching transistors Q1 and Q2, and the Boost unit includes switching transistors Q3 and Q4. Figure 3 As shown, the BuckBoost converter further includes a third capacitor C3 and an LLC circuit connected between the first voltage Vin and the first capacitor. It should be noted that the operating mode switching method of the BuckBoost converter of the present invention is applicable to any four-switch BuckBoost converter. Figures 2-3 This is just an example.

[0020] like Figure 1 As shown, in step S1, a reference duty cycle is generated based on the sampled current, sampled voltage, and reference voltage of the BuckBoost converter. In a preferred embodiment of the invention, a voltage-current dual closed loop can be constructed first. Then, the sampled voltage of the second capacitor C2 is used as the input of the voltage outer loop of the voltage-current dual closed loop, and the reference voltage is used as the setpoint of the voltage outer loop of the voltage-current dual closed loop to generate the setpoint of the current inner loop of the voltage-current dual closed loop. The sampled current of the inductor arm L1 is used as the input of the current inner loop of the voltage-current dual closed loop to generate the reference duty cycle. Of course, in other preferred embodiments of the invention, an output voltage PI loop can be designed first. Then, the sampled voltage of the second capacitor C2 is used as the input of the output voltage PI loop, and the reference voltage is used as the setpoint of the output voltage PI loop. Then, an inductor current PI loop is designed, and the output of the output voltage PI loop is used as the setpoint of the inductor current PI loop. The sampled current of the inductor arm L1 is used as the input of the inductor current PI loop to generate the reference duty cycle. In other preferred embodiments of the invention, the reference duty cycle can also be generated using any other suitable method.

[0021] In step S2, the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter are obtained based on the reference duty cycle. In a preferred embodiment of the present invention, when the reference duty cycle is less than or equal to the Buck mode duty cycle, the current operating mode of the BuckBoost converter is determined to be Buck mode, and the Buck unit compensation duty cycle and Boost unit compensation duty cycle in Buck mode are calculated; when the reference duty cycle is greater than the Buck mode duty cycle and less than or equal to the BuckBoost mode duty cycle, the current operating mode of the BuckBoost converter is determined to be BuckBoost mode, and the Buck unit compensation duty cycle and Boost unit compensation duty cycle in BuckBoost mode are calculated; when the reference duty cycle is greater than the BuckBoost mode duty cycle, the current operating mode of the BuckBoost converter is determined to be Boost mode, and the Buck unit compensation duty cycle and Boost unit compensation duty cycle in Boost mode are calculated.

[0022] In a further preferred embodiment of the present invention, in order to avoid the switching boundary loop jitter problem and the switching boundary threshold has hysteresis, the cut-out duty cycle from Buck mode to Buck-Boost mode is defined to be greater than the cut-in duty cycle, and the cut-in duty cycle from Buck-Boost mode to Boost mode is defined to be greater than the cut-out duty cycle.

[0023] In step S3, the Buck unit duty cycle and the Boost unit duty cycle are generated based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle. In a preferred embodiment of the invention, the Buck unit duty cycle in the current operating mode can be obtained by superimposing the reference duty cycle and the Buck unit compensation duty cycle based on the current operating mode. Similarly, the Boost unit duty cycle in the current operating mode can be obtained by superimposing the reference duty cycle and the Boost unit compensation duty cycle based on the current operating mode.

[0024] In step S4, the switching transistors of the BuckBoost converter are controlled based on the duty cycle of the Buck cell and the duty cycle of the Boost cell to achieve consistent voltage gain.

[0025] In a further preferred embodiment of the present invention, modulation signals for switch Q1 and switch Q2 are generated based on the duty cycle of the Buck unit and the triangular carrier signal, wherein the modulation signal for switch Q1 is inverted compared to the modulation signal for switch Q2; modulation signals for switch Q3 and switch Q4 are generated based on the duty cycle of the Boost unit and the triangular carrier signal, wherein the modulation signal for switch Q3 is inverted compared to the modulation signal for switch Q4; and the switching transistors Q1, Q2, Q3, and Q4 are controlled based on the modulation signals for switch Q1, Q2, Q3, and Q4 to achieve consistent voltage gain.

[0026] According to the volt-second balance principle, the voltage gain Where M represents voltage gain, Vout represents output voltage, Vin represents input voltage, dBuck represents the duty cycle of the Buck unit, and dBoost represents the duty cycle of the Boost unit.

[0027] The BuckBoost converter operating mode switching method of the present invention generates a reference duty cycle based on the sampled current, sampled voltage, and reference voltage of the BuckBoost converter; obtains the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle; generates the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle; and controls the switching transistors of the BuckBoost converter based on the Buck unit duty cycle and the Boost unit duty cycle. Because it obtains the current operating mode of the BuckBoost converter based on the reference duty cycle, and generates the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle, the operating mode switching and voltage judgment are decoupled, ensuring a smooth switching process and consistent voltage gain before and after switching, and preventing drastic voltage fluctuations before and after switching.

[0028] The following will combine Figure 2 The circuit diagram of the BuckBoost converter shown below illustrates a preferred embodiment of the operating mode switching method of the BuckBoost converter of the present invention.

[0029] In this preferred embodiment, the design is first as follows: Figure 4The voltage and current dual closed loop shown includes an outer voltage loop and an inner current loop. Using voltage and current samplers, the sampled voltage OutputVoltReal of the second capacitor and the sampled current ILReal of the inductor arm L1 are acquired, respectively, and used as feedback inputs for the outer voltage loop and the inner current loop. Based on the customer-set reference voltage value OutputVoltRef, the cascaded output dLoopOut through voltage and current loop compensation is used as the reference duty cycle, i.e., the reference duty cycle dLoopOut. Specifically, the sampled voltage OutputVoltReal of the second capacitor is used as the feedback input of the outer voltage loop, the reference voltage value OutputVoltRef is used as the setpoint of the outer voltage loop, the output ILRef of the outer voltage loop is used as the setpoint of the inner current loop, the sampled current ILReal of the inductor arm L1 is used as the feedback value of the inner current loop, and the output dLoopOut of the inner current loop obtained by the cascaded voltage and current loop compensation is used as the reference duty cycle.

[0030] by Figure 2 Taking the BuckBoost converter shown as an example, it has three operating modes: Buck mode, Buck-Boost mode, and Boost mode. Switches Q1 and Q2 are defined as complementary wave generators, and their duty cycles satisfy... The switching transistor Q1 is the main control transistor of Buck unit 100, with a duty cycle of The third switch Q3 and the fourth switch Q4 generate complementary waveforms, and their duty cycles satisfy... The fourth switch, Q4, is the main control transistor of the Boost unit 200, with a duty cycle of... In Buck mode, the duty cycle of switch Q1 is... The duty cycle of the fourth switch Q4 In Buck-Boost mode, the duty cycle of switch Q1 The duty cycle of the fourth switch Q4 In Boost mode, the duty cycle of switch Q1 The duty cycle of the fourth switch Q4 From this, the voltage gain can be obtained. .

[0031] Define the reference duty cycle of the current loop output. ,in This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode. Due to the constraints of maximum duty cycle dMax and minimum duty cycle dMin on the switching transistors, Buck unit compensation duty cycles dBuckComp and dBoostComp are designed to ensure consistent gain before and after the operating mode switch. Therefore, the Buck unit duty cycle is... The duty cycle of the Boost unit is Therefore, we can conclude that: 1) Assuming the BuckBoost converter switches from Buck mode to Buck-Boost mode, the BuckBoost converter is in buck mode. The voltage gain M1 before switching can be expressed as:

[0032] After the operating mode switch, since the BuckBoost converter is still in buck mode, the main control transistor of the Boost unit operates at its minimum duty cycle. At this time, the voltage gain M2 can be expressed as:

[0033] The voltage gain must remain consistent before and after switching operating modes, i.e. = 2. Simultaneous equations: = ,

[0034] After simplification, we get:

[0035] 2) Assume the BuckBoost converter switches from Buck-Boost mode to Boost mode. Before switching operating modes, the BuckBoost converter is in the boost phase. The main control transistor of the Buck unit operates at its maximum duty cycle, and the voltage gain M3 is expressed as:

[0036] After the operating mode switch, the voltage gain M4 of the BuckBoost converter is expressed as follows:

[0037] The voltage gain must remain consistent before and after switching operating modes, i.e. = 4. Simultaneous equations:

[0038] After simplifying the above equation, we get:

[0039] It should be noted that "instead" can be understood as, , 2. , 4. Historical output voltage gain can be used, and this gain will be applied in the next round of control. , By controlling the switching on and off of the converter's transistors, the output voltage gain is kept constant. , 2. , 4 can also be the real-time output voltage gain, through... , Real-time control of the switching transistors of the converter ensures that the output voltage gain remains the same.

[0040] Furthermore, considering the impact of the dead time of the switching transistor on the operating mode switching process, assuming the switching cycle time is Ts and the dead time is Td, the duty cycle during the dead phase can be obtained as follows: Dd is generally taken to be less than dMin, so the actual duty cycle of the switch Q1 is determined. Similarly, the actual duty cycle of the fourth switch Q4 can be obtained. The duty cycles of D1 and D4 after compensating for the dead time Dd are recalculated. = 2. And from the equation M3=M4, we obtain the following formula:

[0041] Furthermore, the calculation expressions for the Buck cell compensation duty cycle dBuckComp and the Boost cell compensation duty cycle dBoostComp, which include the dead time effect, can be calculated:

[0042] Based on the above analysis, the Buck unit compensation duty cycle and the Boost unit compensation duty cycle that ensure consistent voltage gain before and after the operating mode switch can be determined.

[0043] Of course, the effect of dead time can be ignored, in which case the dead duty cycle Dd of the switching transistor can be set to 0. The calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in Buck mode are: dBuckComp=0; dBoostComp=(2-dMax)*(1-dMax); The calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in BuckBoost mode are: dBuckComp=-(dMin)*(dLoopOut)∈[-dMin,0]; dBoostComp=(1-dMax)*(2-dLoopOut)∈[0,(2-dMax)*(1-dMax)]; The formulas for calculating the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in Boost mode are: dBuckComp = -dMin; dBoostComp = 0; where dBuckComp represents the Buck unit compensation duty cycle, dBoostComp represents the Boost unit compensation duty cycle, dMax represents the maximum duty cycle of the switching transistor, dMin represents the minimum duty cycle of the switching transistor, and dLoopOut represents the reference duty cycle; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode.

[0044] Therefore, we can obtain the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the Buck Boost converter based on the reference duty cycle. After confirming the Buck unit compensation duty cycle and Boost unit compensation duty cycle, we generally use the reference duty cycle... Different working mode ranges are selected based on the following ranges, i.e., generally selected. For the Buck pattern interval, For the Buck-Boost mode range, This is the interval for Boost mode.

[0045] The specific process is as follows. When the reference duty cycle is less than or equal to the Buck mode duty cycle, it is determined that the current working mode of the BuckBoost converter is the Buck mode, and the compensation duty cycle of the Buck unit and the compensation duty cycle of the Boost unit in the Buck mode are calculated; when the reference duty cycle is greater than the Buck mode duty cycle and less than or equal to the BuckBoost mode duty cycle, it is determined that the current working mode of the BuckBoost converter is the BuckBoost mode, and the compensation duty cycle of the Buck unit and the compensation duty cycle of the Boost unit in the BuckBoost mode are calculated; when the reference duty cycle is greater than the BuckBoost mode duty cycle, it is determined that the current working mode of the BuckBoost converter is the Boost mode, and the compensation duty cycle of the Buck unit and the compensation duty cycle of the Boost unit in the Boost mode are calculated.

[0046] Figure 5 It is a schematic diagram of the working mode judgment of the BuckBoost converter and the calculation process of the compensation duty cycle of the Buck unit and the compensation duty cycle of the Boost unit in the working mode switching method of the BuckBoost converter of the present invention. As Figure 5 shown, first, after obtaining the reference duty cycle dLoopOut through the voltage-current double closed-loop, it is judged whether it is less than or equal to the Buck mode duty cycle (that is, whether dLoopOut <= dMax holds). If so, it is determined that the current working mode of the BuckBoost converter is the Buck mode; otherwise, it is judged that it is greater than the Buck mode duty cycle and less than or equal to the BuckBoost mode duty cycle (that is, whether dMax < dLoopOut <= 1 + dMin holds). If so, it is determined that the current working mode of the BuckBoost converter is the BuckBoost mode; otherwise, continue to judge whether the reference duty cycle is greater than the BuckBoost mode duty cycle (that is, whether 1 + dMin < dLoopOut or 1 + dMin < dLoopOut <= 2 holds). If so, it is determined that the current working mode of the BuckBoost converter is the Boost mode.

[0047] Furthermore, as Figure 5As shown, the calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Buck mode are: dBuckComp=0; dBoostComp=(2-dMax+Dd)*(1-dMax+Dd); The calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the BuckBoost mode are: dBuckComp=-(dMin-Dd)*(dLoopOut-Dd)∈[Dd-dMin,0]; dBoostComp=(1-dMax+Dd)*(2-dLoopOut+Dd)∈[0,(2-dMax+Dd)*(1-dMax+Dd)]; The formulas for calculating the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in Boost mode are: dBuckComp = Dd - dMin; dBoostComp = 0; where dBuckComp represents the Buck unit compensation duty cycle, dBoostComp represents the Boost unit compensation duty cycle, dMax represents the maximum duty cycle of the switching transistor, Dd represents the dead-time duty cycle of the switching transistor, dMin represents the minimum duty cycle of the switching transistor, and dLoopOut represents the reference duty cycle; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode.

[0048] Subsequently, the Buck unit duty cycle and the Boost unit duty cycle are generated based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle. Then, the switching transistors of the BuckBoost converter are controlled based on the Buck unit duty cycle and the Boost unit duty cycle to achieve consistent voltage gain. The specific process is as follows: Figure 6 As shown.

[0049] Figure 6 This is a schematic diagram illustrating the steps for generating the Buck cell duty cycle and the Boost cell duty cycle, as well as the switching transistor control steps, in the BuckBoost converter operating mode switching method of the present invention. Figure 6As shown, when the current operating mode is BuckBoost mode, the formulas for calculating the duty cycle of the Buck unit and the duty cycle of the Boost unit are: dBuck = dLoopOut + dBuckComp ∈ [dMin, dMax]; dBoost = dLoopOut - 1 + dBoostComp ∈ [dMin, dMax]; when the current operating mode is Buck mode, the formulas for calculating the duty cycle of the Buck unit and the Boost unit are: dBuck = dLoopOut + dBuckComp ∈ [dMin, dMax]; dBoost = 0; when the current operating mode is Boost mode, the duty cycle of the Buck unit is calculated as follows ... The formulas for calculating the duty cycle and the duty cycle of the Boost unit are: dBuck = 1; dBoost = dLoopOut - 1 + dBoostComp ∈ [dMin, dMax]; where dBuck represents the duty cycle of the Buck unit, dBoost represents the duty cycle of the Boost unit; dLoopOut represents the base duty cycle, dBuckComp represents the Buck unit compensation duty cycle in the current operating mode, dBoostComp represents the Boost unit compensation duty cycle in the current operating mode; dMax represents the maximum duty cycle of the switch, Dd represents the dead-time duty cycle of the switch, dMin represents the minimum duty cycle of the switch; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode.

[0050] Further as Figure 6 The method involves generating a first switching transistor modulation signal PWM_D1 and a second switching transistor modulation signal PWM_D2 based on the Buck unit duty cycle dBuck and the triangular carrier signal, wherein the first switching transistor modulation signal PWM_D1 is inverted compared to the second switching transistor modulation signal PWM_D2; generating a third switching transistor modulation signal PWM_D3 and a fourth switching transistor modulation signal PWM_D4 based on the Boost unit duty cycle dBoost and the triangular carrier signal, wherein the third switching transistor modulation signal PWM_D3 is inverted compared to the fourth switching transistor modulation signal PWM_D4; and controlling switching transistors Q1, Q2, Q3, and Q4 based on the first switching transistor modulation signal PWM_D1, the second switching transistor modulation signal PWM_D2, the third switching transistor modulation signal PWM_D3, and the fourth switching transistor modulation signal PWM_D4 to achieve consistent voltage gain.

[0051] In a preferred embodiment of the present invention, the duty cycle dBuck of the Buck unit can be input to any known drive signal generation unit. The drive signal generation unit generates a first switch modulation signal PWM_D1 and a second switch modulation signal PWM_D2 based on the current operating mode of the BuckBoost converter, according to the duty cycle dBuck of the Buck unit and the triangular carrier signal. The first switch modulation signal PWM_D1 is out of phase with the second switch modulation signal PWM_D2, and is sent to switches Q1 and Q2. The main control transistor of the Buck unit is switch Q1, and the corresponding duty cycle is dBuck. Similarly, the duty cycle dBoost of the Boost unit can be input to any known drive signal generation unit. The drive signal generation unit generates the third switch modulation signal PWM_D3 and the fourth switch modulation signal PWM_D4 based on the current operating mode of the Boost Boost converter, according to the duty cycle dBoost of the Boost unit and the triangular carrier signal. The third switch modulation signal PWM_D3 is inverted with the fourth switch modulation signal PWM_D4 and is sent to the switches Q4 and Q3. The main control transistor of the Boost unit is the fourth switch Q4, and the corresponding duty cycle is dBoost. This completes the output voltage regulation control. Based on the volt-second balance principle, the voltage gain... Where M represents voltage gain, Vout represents output voltage, Vin represents input voltage, dBuck represents the duty cycle of the Buck unit, and dBoost represents the duty cycle of the Boost unit.

[0052] The BuckBoost converter operating mode switching method of the present invention generates a reference duty cycle based on the sampled current, sampled voltage, and reference voltage of the BuckBoost converter; obtains the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle; generates the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle; and controls the switching transistors of the BuckBoost converter based on the Buck unit duty cycle and the Boost unit duty cycle. Because it obtains the current operating mode of the BuckBoost converter based on the reference duty cycle, and generates the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle, the operating mode switching and voltage judgment are decoupled, ensuring a smooth switching process and consistent voltage gain before and after switching, and preventing drastic voltage fluctuations before and after switching.

[0053] The following will combine Figure 3 The circuit diagram of the BuckBoost converter shown below illustrates a preferred embodiment of the operating mode switching method for the BuckBoost converter of the present invention. Figure 3 The BuckBoost converter shown is suitable for bidirectional DC charging and discharging of a Vehicle to Device (V2D) electric vehicle discharge device. The BuckBoost converter includes an LLC circuit, an input filter capacitor C3, a bus filter capacitor C1, an output filter capacitor C2, a filter inductor L1, and four controllable switching transistors Q1-Q4.

[0054] Assumptions: The sampling voltage of the second capacitor C2 and the sampling current of the inductor bridge arm L1 are sampled and controlled at a switching frequency fs of 40KHz. The switching cycle time is Ts (25µs). The maximum duty cycle constraint dMax of the switch is 0.95, the minimum duty cycle dMin is 0.05, and the dead time Td is 0.5µs. The duty cycle of the dead time can be obtained. .

[0055] As mentioned earlier, the first step is to design as follows: Figure 4The shown voltage-current double closed-loop includes a voltage outer loop and a current inner loop. A voltage sampler and a current sampler are used to respectively obtain the sampled voltage OutputVoltReal of the second capacitor and the sampled current ILReal of the inductor leg L1, and use them as the feedback inputs of the voltage outer loop and the current inner loop respectively. According to the reference voltage reference value OutputVoltRef set by the customer, through the compensation effect of the voltage loop and the current loop, the cascaded output dLoopOut is used as the reference duty cycle, that is, the reference duty cycle dLoopOut. Specifically, the sampled voltage OutputVoltReal of the second capacitor is used as the feedback input of the voltage outer loop, the reference voltage reference value OutputVoltRef is used as the given value of the voltage outer loop, then the output ILRef of the voltage outer loop is used as the given value of the current inner loop, the sampled current ILReal of the inductor leg L1 is used as the feedback value of the current inner loop, and then the current inner loop output dLoopOut obtained by cascading the compensation effect of the voltage loop and the current loop is used as the reference duty cycle.

[0056] Subsequently, similar to the foregoing embodiments, we can obtain the current working mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle. In this preferred embodiment, to avoid the switching boundary cycle jitter problem, the switching boundary threshold has a hysteresis. That is, when the reference duty cycle is less than or equal to the Buck mode duty cycle, it is determined that the current working mode of the BuckBoost converter is the Buck mode, including: when the reference duty cycle dLoopOut <= dMax, it is determined that the current working mode of the BuckBoost converter is the Buck mode; when the reference duty cycle is greater than the Buck mode duty cycle and less than or equal to the BuckBoost mode duty cycle, it is determined that the current working mode of the BuckBoost converter is the BuckBoost mode, including: when the reference duty cycle dMax < dLoopOut <= 1 + dMin, it is determined that the current working mode of the BuckBoost converter is the BuckBoost mode; when the reference duty cycle is greater than the BuckBoost mode duty cycle, it is determined that the current working mode of the BuckBoost converter is the Boost mode, including: when the reference duty cycle 1 + dMin < dLoopOut <= 2, it is determined that the current working mode of the BuckBoost converter is the Boost mode. When the reference duty cycle is less than or equal to the Buck mode duty cycle, it is determined that the current working mode of the BuckBoost converter is the Buck mode, which further includes: when the BuckBoost converter switches back to the Buck mode from the BuckBoost mode, when the reference duty cycle dLoopOut <= When it is, it is determined that the current working mode of the Buck - Boost converter is the Buck mode; when the reference duty cycle is greater than the Buck - Boost mode duty cycle, it is determined that the current working mode of the Buck - Boost converter is the Boost mode. Further included is: when the Buck - Boost converter switches from the Buck - Boost mode to the Buck mode, when the reference duty cycle <dLoopOut <= 2, it is determined that the current working mode of the Buck - Boost converter is the Boost mode.

[0057] Figure 7 is a schematic diagram of another working mode determination process of the Buck - Boost converter in the working mode switching method of the Buck - Boost converter of the present invention. As Figure 7 shown, define the switching - in duty cycle from the Buck mode to the Buck - Boost mode as , and the switching - out duty cycle as ; define the switching - in duty cycle from the Buck - Boost mode to the Boost mode as , and the switching - out duty cycle as , then according to the reference duty cycle dLoopOut, it is possible to determine the current working mode of the Buck - Boost converter, and calculate the Buck unit compensation duty cycle dBuckComp and the Boost unit compensation duty cycle dBoostComp.

[0058] Figure 8 is a schematic diagram of the calculation process of the Buck unit compensation duty cycle and the Boost unit compensation duty cycle of the Buck - Boost converter in the working mode switching method of the Buck - Boost converter of the present invention; the calculation process is similar to the foregoing embodiment. Further as Figure 8As shown, the calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Buck mode are: dBuckComp=0; dBoostComp=(2-dMax+Dd)*(1-dMax+Dd)=1.07*0.07; The calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the BuckBoost mode are: dBuckComp=-(dMin-Dd)*(dLoopOut-Dd)∈[Dd-dMin,0]; that is, dBuckComp=-0.03*(dLoopOut-0.02)∈[-0.03,0]; dBoostComp=(1-dMax+Dd)*(2-dLoopOut+Dd)∈[0,(2-dMax+Dd)*(1-dMax+Dd)]; That is, dBoostComp==0.07*(2.02-dLoopOut)∈[0,0.07*1.07]; the calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Boost mode are: dBuckComp=Dd-dMin=-0.03; dBoostComp=0; where dBuckComp represents the Buck unit compensation duty cycle, dBoostComp represents the Boost unit compensation duty cycle, dMax represents the maximum duty cycle of the switching transistor, Dd represents the dead time duty cycle of the switching transistor, dMin represents the minimum duty cycle of the switching transistor, and dLoopOut represents the reference duty cycle; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode.

[0059] Subsequently, similar to the aforementioned embodiments, such as Figure 6As shown, when the current working mode is BuckBoost mode, the calculation formulas for the Buck unit duty cycle and the Boost unit duty cycle are: dBuck = dLoopOut + dBuckComp ∈ [dMin, dMax]; dBoost = dLoopOut - 1 + dBoostComp ∈ [dMin, dMax]; when the current working mode is Buck mode, the calculation formulas for the Buck unit duty cycle and the Boost unit duty cycle are: dBuck = dLoopOut + dBuckComp ∈ [dMin, dMax]; dBoost = 0; when the current working mode is Boost mode, the calculation formulas for the Buck unit duty cycle and the Boost unit duty cycle are: dBuck = 1; dBoost = dLoopOut - 1 + dBoostComp ∈ [dMin, dMax]; where dBuck represents the duty cycle of the Buck cell, dBoost represents the duty cycle of the Boost cell; dLoopOut represents the base duty cycle, dBuckComp represents the Buck cell compensation duty cycle in the current operating mode, dBoostComp represents the Boost cell compensation duty cycle in the current operating mode; dMax represents the maximum duty cycle of the switch, Dd represents the dead-time duty cycle of the switch, dMin represents the minimum duty cycle of the switch; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode.

[0060] Further as Figure 6 The method involves generating a first switching transistor modulation signal PWM_D1 and a second switching transistor modulation signal PWM_D2 based on the Buck unit duty cycle dBuck and the triangular carrier signal, wherein the first switching transistor modulation signal PWM_D1 is inverted compared to the second switching transistor modulation signal PWM_D2; generating a third switching transistor modulation signal PWM_D3 and a fourth switching transistor modulation signal PWM_D4 based on the Boost unit duty cycle dBoost and the triangular carrier signal, wherein the third switching transistor modulation signal PWM_D3 is inverted compared to the fourth switching transistor modulation signal PWM_D4; and controlling switching transistors Q1, Q2, Q3, and Q4 based on the first switching transistor modulation signal PWM_D1, the second switching transistor modulation signal PWM_D2, the third switching transistor modulation signal PWM_D3, and the fourth switching transistor modulation signal PWM_D4 to achieve consistent voltage gain.

[0061] In a preferred embodiment of the present invention, the duty cycle dBuck of the Buck unit can be input to any known drive signal generation unit. The drive signal generation unit generates a first switch modulation signal PWM_D1 and a second switch modulation signal PWM_D2 based on the current operating mode of the BuckBoost converter, according to the duty cycle dBuck of the Buck unit and the triangular carrier signal. The first switch modulation signal PWM_D1 is out of phase with the second switch modulation signal PWM_D2, and is sent to switches Q1 and Q2. The main control transistor of the Buck unit is switch Q1, and the corresponding duty cycle is dBuck. Similarly, the duty cycle dBoost of the Boost unit can be input to any known drive signal generation unit. The drive signal generation unit generates the third switch modulation signal PWM_D3 and the fourth switch modulation signal PWM_D4 based on the current operating mode of the Boost Boost converter, according to the duty cycle dBoost of the Boost unit and the triangular carrier signal. The third switch modulation signal PWM_D3 is inverted with the fourth switch modulation signal PWM_D4 and is sent to the switches Q4 and Q3. The main control transistor of the Boost unit is the fourth switch Q4, and the corresponding duty cycle is dBoost. This completes the output voltage regulation control. Based on the volt-second balance principle, the voltage gain... Where M represents voltage gain, Vout represents output voltage, Vin represents input voltage, dBuck represents the duty cycle of the Buck unit, and dBoost represents the duty cycle of the Boost unit.

[0062] The BuckBoost converter operating mode switching method of the present invention generates a reference duty cycle based on the sampled current, sampled voltage, and reference voltage of the BuckBoost converter; obtains the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle; generates the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle; and controls the switching transistors of the BuckBoost converter based on the Buck unit duty cycle and the Boost unit duty cycle. Because it obtains the current operating mode of the BuckBoost converter based on the reference duty cycle, and generates the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle, the operating mode switching and voltage judgment are decoupled, ensuring a smooth switching process and consistent voltage gain before and after switching, and preventing drastic voltage fluctuations before and after switching. Furthermore, in this preferred embodiment, the switching process is relatively smooth, solving the problem of drastic voltage fluctuations at the switching boundary. The duty cycles of the Buck unit and the Boost unit are obtained by superimposing their respective compensated duty cycles on the output of the same current loop, eliminating the need for additional loops, simplifying implementation, improving controller robustness, and providing better dynamic performance.

[0063] Figure 9 This is a schematic diagram showing the approximate changes in the duty cycle of Buck and Boost cells under different operating modes, without considering the effect of dead time. Figure 10A and Figure 10B Output voltage test diagram of the BuckBoost converter after employing the operating mode switching method of the BuckBoost converter of the present invention. See also... Figure 9 From 10A to 10B, we know that the input voltage of the BuckBoost converter is 500V, the output load is a 300Ω resistor, and the output voltage rises from 0V to 1000V at a slow voltage change rate of 600V / s, and then falls back to 300V. We can see that the switching process between the three operating modes is relatively smooth. At the mode switching boundary points, the output voltage and inductor current are basically stable, showing good dynamic performance. The switching boundary point 1 is from Buck mode to Buck-Boost mode, the switching boundary point 2 is from Buck-Boost mode to Boost mode, the switching boundary point 3 is from Boost mode to Buck-Boost mode, and the switching boundary point 4 is from Buck-Boost mode to Buck mode.

[0064] A further preferred embodiment of the present invention also provides a BuckBoost converter control system. Figure 11 This is a block diagram illustrating the principle of the BuckBoost converter control system of the present invention. The BuckBoost converter control system includes a BuckBoost converter, a sampling device, a reference duty cycle device, a nonlinear controller, a duty cycle generation device, and a drive device.

[0065] like Figure 11 As shown, the BuckBoost converter includes a first capacitor C1, a Buck unit 100, a Boost unit 200, a second capacitor C2, and an inductor bridge arm L1. The first capacitor C1 is connected to a first voltage Vin and the Buck unit 100, and the second capacitor C2 is connected to a second voltage Vout and the Boost unit 200. The two ends of the inductor bridge arm L1 are respectively connected to the Buck unit 100 and the Boost unit 200. Preferably, the Buck unit 100 includes switching transistors Q1 and Q2, and the Boost unit includes switching transistors Q3 and Q4. As mentioned above, in other preferred embodiments of the present invention, the BuckBoost converter may also employ other structures.

[0066] The sampling device is used to sample the sampling current and sampling voltage of the BuckBoost converter. The reference duty cycle device is used to generate a reference duty cycle based on the sampling current, sampling voltage, and reference voltage reference value of the BuckBoost converter; the nonlinear controller is used to obtain the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle; the duty cycle generation device is used to generate the Buck unit duty cycle and Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle; the driving device is used to control the switching transistors of the BuckBoost converter based on the Buck unit duty cycle and the Boost unit duty cycle to achieve voltage gain consistency. Figure 11 As shown, the driving device includes a driving signal generation unit, a first driving unit, and a second driving unit, which are used to drive the switching transistors Q1 and Q2 of the Buck unit 100, and the switching transistors Q3 and Q4 of the Boost unit, respectively. As mentioned above, the reference duty cycle device, the nonlinear controller, the duty cycle generation device, and the driving device can be constructed based on the aforementioned embodiments.

[0067] Preferably, the reference duty cycle device can be used to take the sampled voltage of the second capacitor as the input of the voltage outer loop of the voltage-current dual closed loop, take the reference voltage reference value as the given value of the voltage outer loop of the voltage-current dual closed loop, and generate the given value of the current inner loop of the voltage-current dual closed loop; and take the sampled current of the inductor bridge arm as the input of the current inner loop of the voltage-current dual closed loop to generate the reference duty cycle. The nonlinear controller can be used to determine that the current operating mode of the BuckBoost converter is Buck mode when the reference duty cycle is less than or equal to the Buck mode duty cycle, and calculate the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Buck mode; when the reference duty cycle is greater than the Buck mode duty cycle and less than or equal to the BuckBoost mode duty cycle, determine that the current operating mode of the BuckBoost converter is BuckBoost mode, and calculate the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the BuckBoost mode; when the reference duty cycle is greater than the BuckBoost mode duty cycle, determine that the current operating mode of the BuckBoost converter is Boost mode, and calculate the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Boost mode.

[0068] Preferably, the calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Buck mode are: dBuckComp=0; dBoostComp=(2-dMax+Dd)*(1-dMax+Dd); the calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the BuckBoost mode are: dBuckComp=-(dMin-Dd)*(dLoopOut-Dd)∈[Dd-dMin,0]; dBoostComp=(1-dMax+Dd)*(2-dLoopOut+Dd)∈[0,(2-dMax+Dd)*(1-dMax+Dd) The formulas for calculating the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in Boost mode are: dBuckComp = Dd - dMin; dBoostComp = 0; where dBuckComp represents the Buck unit compensation duty cycle, dBoostComp represents the Boost unit compensation duty cycle, dMax represents the maximum duty cycle of the switching transistor, Dd represents the dead-time duty cycle of the switching transistor, dMin represents the minimum duty cycle of the switching transistor, and dLoopOut represents the reference duty cycle. dLoopOut , Indicates that the Buck - Boost converter is in the buck state, Indicates that the Buck - Boost converter is in the boost state.

[0069] Preferably, when the reference duty cycle is less than or equal to the buck - mode duty cycle, it is determined that the current operating mode of the Buck - Boost converter is the buck mode, including: when the reference duty cycle dLoopOut <= dMax, it is determined that the current operating mode of the Buck - Boost converter is the buck mode; when the reference duty cycle is greater than the buck - mode duty cycle and less than or equal to the Buck - Boost - mode duty cycle, it is determined that the current operating mode of the Buck - Boost converter is the Buck - Boost mode, including: when the reference duty cycle dMax < dLoopOut <= 1 + dMin, it is determined that the current operating mode of the Buck - Boost converter is the Buck - Boost mode; when the reference duty cycle is greater than the Buck - Boost - mode duty cycle, it is determined that the current operating mode of the Buck - Boost converter is the boost mode, including: when the reference duty cycle 1 + dMin < dLoopOut <= 2, it is determined that the current operating mode of the Buck - Boost converter is the boost mode.

[0070] Preferably, when the reference duty cycle is less than or equal to the buck - mode duty cycle, further determining that the current operating mode of the Buck - Boost converter is the buck mode includes: when the Buck - Boost converter switches back to the buck mode from the Buck - Boost mode, when the reference duty cycle dLoopOut <= then it is determined that the current operating mode of the Buck - Boost converter is the buck mode; and / or when the reference duty cycle is greater than the Buck - Boost - mode duty cycle, further determining that the current operating mode of the Buck - Boost converter is the boost mode includes: when the Buck - Boost converter switches from the Buck - Boost mode to the buck mode, when the reference duty cycle < dLoopOut <= 2, it is determined that the current operating mode of the Buck - Boost converter is the boost mode.

[0071] Preferably, when the current operating mode is BuckBoost mode, the formulas for calculating the duty cycle of the Buck unit and the duty cycle of the Boost unit are: dBuck = dLoopOut + dBuckComp ∈ [dMin, dMax]; dBoost = dLoopOut - 1 + dBoostComp ∈ [dMin, dMax]; when the current operating mode is Buck mode, the formulas for calculating the duty cycle of the Buck unit and the duty cycle of the Boost unit are: dBuck = dLoopOut + dBuckComp ∈ [dMin, dMax]; dBoost = 0; when the current operating mode is Boost mode, the duty cycle of the Buck unit is calculated as follows ... The formulas for calculating the duty cycle and the duty cycle of the Boost unit are: dBuck = 1; dBoost = dLoopOut - 1 + dBoostComp ∈ [dMin, dMax]; where dBuck represents the duty cycle of the Buck unit, dBoost represents the duty cycle of the Boost unit; dLoopOut represents the base duty cycle, dBuckComp represents the Buck unit compensation duty cycle in the current operating mode, dBoostComp represents the Boost unit compensation duty cycle in the current operating mode; dMax represents the maximum duty cycle of the switch, Dd represents the dead-time duty cycle of the switch, dMin represents the minimum duty cycle of the switch; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode.

[0072] Preferably, the drive signal generation unit is used to generate a first switch modulation signal and a second switch modulation signal based on the Buck unit duty cycle and the triangular carrier signal, wherein the first switch modulation signal is out of phase with the second switch modulation signal; and to generate a third switch modulation signal and a fourth switch modulation signal based on the Boost unit duty cycle and the triangular carrier signal, wherein the third switch modulation signal is out of phase with the fourth switch modulation signal; the first drive unit is used to control the first switch and the second switch based on the first switch modulation signal and the second switch modulation signal; the second drive unit is used to control the third switch and the fourth switch based on the third switch modulation signal and the fourth switch modulation signal.

[0073] Although this invention has been described through specific embodiments, those skilled in the art should understand that various modifications and equivalent substitutions can be made to this invention without departing from its scope. Furthermore, various modifications can be made to this invention for specific situations or materials without departing from its scope. Therefore, this invention is not limited to the specific embodiments disclosed, but should include all embodiments falling within the scope of the claims. The above descriptions are merely preferred embodiments of the invention and are not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A method for switching the operating mode of a BuckBoost converter, characterized in that, include: A reference duty cycle is generated based on the sampled current, sampled voltage, and reference voltage value of the BuckBoost converter. The current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter are obtained based on the reference duty cycle. The Buck unit duty cycle and the Boost unit duty cycle are generated based on the baseline duty cycle, the current operating mode, the Buck unit compensated duty cycle, and the Boost unit compensated duty cycle. The switching transistors of the BuckBoost converter are controlled based on the duty cycles of the Buck cells and the Boost cells to achieve consistent output voltage gain.

2. The operating mode switching method for the BuckBoost converter according to claim 1, characterized in that, The BuckBoost converter includes a first capacitor, a Buck unit, a Boost unit, a second capacitor, and an inductor bridge arm; the first capacitor is connected to a first voltage and the Buck unit, and the second capacitor is connected to a second voltage and the Boost unit; the two ends of the inductor bridge arm are respectively connected to the Buck unit and the Boost unit. The Buck unit includes a first switch and a second switch, and the Boost unit includes a third switch and a fourth switch.

3. The operating mode switching method for the BuckBoost converter according to claim 2, characterized in that, A reference duty cycle is generated based on the sampled current, sampled voltage, and reference voltage reference value of the BuckBoost converter, including: The sampled voltage of the second capacitor is used as the input of the outer voltage loop of the voltage-current dual closed loop, and the reference voltage value is used as the given value of the outer voltage loop of the voltage-current dual closed loop to generate the given value of the inner current loop of the voltage-current dual closed loop. The sampling current of the inductor bridge arm is used as the input of the inner current loop of the voltage-current dual closed loop to generate the reference duty cycle.

4. The operating mode switching method for the BuckBoost converter according to claim 2, characterized in that, Based on the reference duty cycle, the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the Buck Boost converter are obtained, including: When the reference duty cycle is less than or equal to the Buck mode duty cycle, the current operating mode of the BuckBoost converter is determined to be Buck mode, and the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Buck mode are calculated. When the reference duty cycle is greater than the Buck mode duty cycle and less than or equal to the BuckBoost mode duty cycle, the current operating mode of the BuckBoost converter is determined to be BuckBoost mode, and the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the BuckBoost mode are calculated. When the reference duty cycle is greater than the BuckBoost mode duty cycle, the current operating mode of the BuckBoost converter is determined to be Boost mode, and the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in Boost mode are calculated.

5. The operating mode switching method for the BuckBoost converter according to claim 4, characterized in that, The calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Buck mode are: dBuckComp=0; dBoostComp=(2-dMax)*(1-dMax); The calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the BuckBoost mode are: dBuckComp=-(dMin)*(dLoopOut)∈[-dMin,0]; dBoostComp=(1-dMax)*(2-dLoopOut)∈[0,(2-dMax)*(1-dMax)]; The Buck unit compensation duty cycle and the calculation formula for the Boost unit compensation duty cycle in the Boost mode are: dBuckComp = -dMin; dBoostComp = 0; Where dBuckComp represents the Buck unit compensation duty cycle, dBoostComp represents the Boost unit compensation duty cycle, dMax represents the maximum duty cycle of the switching transistor, dMin represents the minimum duty cycle of the switching transistor, and dLoopOut represents the reference duty cycle. dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode, and the calculation formula is obtained under the same output voltage gain.

6. The operating mode switching method for the BuckBoost converter according to claim 5, characterized in that, The step of obtaining the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle further includes: obtaining the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle and the dead time duty cycle of the switching transistors. The calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Buck mode are: dBuckComp=0; dBoostComp=(2-dMax+Dd)*(1-dMax+Dd); The calculation formulas for the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the BuckBoost mode are: dBuckComp=-(dMin-Dd)*(dLoopOut-Dd)∈[Dd-dMin,0]; dBoostComp=(1-dMax+Dd)*(2-dLoopOut+Dd)∈[0,(2-dMax+Dd)*(1-dMax+Dd)]; The formula for calculating the Buck unit compensation duty cycle and the Boost unit compensation duty cycle in the Boost mode is: dBuckComp=Dd-dMin; dBoostComp=0; Where dBuckComp represents the compensation duty cycle of the Buck cell, dBoostComp represents the compensation duty cycle of the Boost cell, dMax represents the maximum duty cycle of the switching transistor, Dd represents the dead-time duty cycle of the switching transistor, dMin represents the minimum duty cycle of the switching transistor, and dLoopOut represents the reference duty cycle; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode.

7. The operating mode switching method for the BuckBoost converter according to claim 5 or 6, characterized in that, When the reference duty cycle is less than or equal to the Buck-mode duty cycle, it is determined that the current operating mode of the BuckBoost converter is the Buck mode, including: when the reference duty cycle dLoopOut <= dMax, it is determined that the current operating mode of the BuckBoost converter is the Buck mode; When the reference duty cycle is greater than the Buck-mode duty cycle and less than or equal to the BuckBoost-mode duty cycle, it is determined that the current operating mode of the BuckBoost converter is the BuckBoost mode, including: when the reference duty cycle dMax < dLoopOut <= 1 + dMin, it is determined that the current operating mode of the BuckBoost converter is the BuckBoost mode; When the reference duty cycle is greater than the BuckBoost-mode duty cycle, it is determined that the current operating mode of the BuckBoost converter is the Boost mode, including: when the reference duty cycle 1 + dMin < dLoopOut <= 2, it is determined that the current operating mode of the BuckBoost converter is the Boost mode.

8. The operating mode switching method for the BuckBoost converter according to claim 5 or 6, characterized in that, When the reference duty cycle is less than or equal to the Buck mode duty cycle, the current operating mode of the BuckBoost converter is determined to be Buck mode. This further includes: when the BuckBoost converter switches back from BuckBoost mode to Buck mode, if the reference duty cycle dLoopOut <= When the BuckBoost converter is in Buck mode, it is determined that the current operating mode of the BuckBoost converter is Buck mode; and / or When the reference duty cycle is greater than the Buck - Boost mode duty cycle, it is determined that the current working mode of the Buck - Boost converter is the Boost mode, and it further includes: when the Buck - Boost converter switches from the Buck - Boost mode to the Buck mode, when the reference duty cycle <dLoopOut <= 2, it is determined that the current working mode of the Buck - Boost converter is the Boost mode.

9. The operating mode switching method for a BuckBoost converter according to any one of claims 2 to 6, characterized in that, Generate the Buck cell duty cycle and the Boost cell duty cycle based on the reference duty cycle, the current operating mode, the Buck cell compensation duty cycle, and the Boost cell compensation duty cycle, including: When the current operating mode is the BuckBoost mode, the calculation formulas for the Buck cell duty cycle and the Boost cell duty cycle are: dBuck = dLoopOut + dBuckComp ∈ [dMin, dMax]; dBoost = dLoopOut - 1 + dBoostComp ∈ [dMin, dMax]; When the current operating mode is the Buck mode, the calculation formulas for the Buck cell duty cycle and the Boost cell duty cycle are: dBuck = dLoopOut + dBuckComp ∈ [dMin, dMax]; dBoost = 0; When the current operating mode is the Boost mode, the calculation formulas for the Buck cell duty cycle and the Boost cell duty cycle are: dBuck = 1; dBoost = dLoopOut - 1 + dBoostComp ∈ [dMin, dMax]; Where dBuck represents the duty cycle of the Buck cell, dBoost represents the duty cycle of the Boost cell; dLoopOut represents the base duty cycle, dBuckComp represents the Buck cell compensation duty cycle in the current operating mode, dBoostComp represents the Boost cell compensation duty cycle in the current operating mode; dMax represents the maximum duty cycle of the switch, Dd represents the dead time duty cycle of the switch, dMin represents the minimum duty cycle of the switch; dLoopOut , This indicates that the BuckBoost converter is in buck mode. This indicates that the BuckBoost converter is in boost mode.

10. A BuckBoost converter control system, characterized in that, Including a BuckBoost converter, a sampling device, a reference duty cycle device, a non-linear controller, a duty cycle generation device, and a driving device; The sampling device is used to sample the sampling current and sampling voltage of the BuckBoost converter; The reference duty cycle device is used to generate a reference duty cycle based on the sampled current, sampled voltage, and reference voltage reference value of the BuckBoost converter. The nonlinear controller is used to obtain the current operating mode, Buck unit compensation duty cycle, and Boost unit compensation duty cycle of the BuckBoost converter based on the reference duty cycle. The duty cycle generation device is used to generate the Buck unit duty cycle and the Boost unit duty cycle based on the reference duty cycle, the current operating mode, the Buck unit compensation duty cycle, and the Boost unit compensation duty cycle; The driving device is used to control the switching transistors of the BuckBoost converter based on the duty cycle of the Buck unit and the duty cycle of the Boost unit to achieve consistent voltage gain.

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