A zvs control method and system for a four-switch buck-boost converter

Abstract

The present application belongs to the field of step-down-step-up converter control, and particularly relates to a ZVS control method and system for a four-switch Buck-Boost converter. The present application divides a switching cycle into three segments for ZVS control through the design of first, second, third and fourth time nodes, removes the circulating current freewheeling link in the existing quadrilateral inductance current control, reduces the effective value of inductance current, and improves the power transmission efficiency of the converter. The present application also sets a targeted constraint control condition, simultaneously realizes online real-time constant voltage closed loop and minimum on-state loss ZVS control of each working mode, effectively reduces the on-state loss of the converter, and is simple and easy to implement. When switching between working modes, the present application increases the corresponding jump value of the output of the PI regulator in the ZVS constant voltage closed loop control corresponding to the converter, ensures that the voltage gain of the converter remains unchanged before and after mode switching, stabilizes the output voltage before and after the jump, and thus avoids voltage distortion caused by mode switching.

Description

Technical Field

[0001] This invention belongs to the field of buck-boost converter control, specifically relating to a ZVS control method and system for a four-switch Buck-Boost converter. Background Technology

[0002] Buck-boost converters not only solve voltage conversion problems when the input and output voltage ranges overlap, but also function as voltage regulators to precisely adjust constantly changing input voltages to the required stricter limits. They can also be applied to redundant power supply designs. Functionally, they can handle all types of voltage conversion and can be used as a general-purpose tool for DC / DC voltage conversion. Therefore, they have always attracted attention and are used in applications with a wide input voltage range, such as new energy power generation systems, distributed power systems, energy storage systems, communication power systems, electric vehicle power supply systems, and power supply systems for portable electronic devices and RF power amplifiers.

[0003] like Figure 1 The four-switch Buck-Boost converter shown has the aforementioned wide voltage range buck-boost capability, and compared with traditional Buck-Boost, Cuk, Zeta, and Sepic buck-boost converters, it has advantages such as identical input and output polarity, low voltage stress on the switching transistors, and fewer passive components. In order to significantly reduce the size and cost of reactive components and improve the switching frequency and dynamic response characteristics of the converter, soft-switching control of this topology has become a research hotspot. Based on whether auxiliary devices or auxiliary switches are added, the soft-switching control methods of non-inverting Buck-Boost converters can be divided into three categories: (1) Zero voltage transition (ZVT) control by adding active auxiliary circuits; (2) Zero voltage switching (ZVS) control by adding passive auxiliary devices; (3) Digital control soft-switching scheme without adding any auxiliary devices.

[0004] In their papers "A novel low-loss modulation strategy for high-power bi-directional buck+boost converters" and "A novel low-loss modulation strategy for high-power bidirectional buck+boost converters," Waffler S and Kolar JW proposed a quadrilateral inductor current ZVS control strategy (hereinafter referred to as the quadrilateral control method). This strategy achieves ZVS switching of all switching transistors by providing a negative compensation current at the beginning and end of each pulse cycle. This is a purely digitally controlled soft-switching scheme that does not require any additional active or passive components, thus improving efficiency while maintaining a low component count and the simplicity of power electronic circuits. Its control timing diagram is shown below. Figure 2 As shown. However, the paper only provides the steady-state calculation process, lacking a closed-loop control strategy and a calculation scheme for reducing the effective value of the inductor current.

[0005] In the paper "A constant frequency ZVS control system for the four-switch buck-boost DC-DC converter with reduced inductor current" by Zhou ZJ, Li HY, and Wu XK, closed-loop control was implemented based on the quadrangle control method, and a scheme to reduce the effective value of the inductor current was proposed. In the paper "An Improved Quadrangle Control Method for Four-Switch Buck-Boost Converter With Reduced Loss and Decoupling Strategy" by Liu Q, Qian QS, Zheng M, et al., an improved quadrangle control method was proposed to reduce losses and decouple compensation to improve system stability. However, the inductor current in the quadrangle control methods of the above schemes all have circulating freewheeling links, which increases the effective value of the inductor current and the on-state loss of the converter, and reduces the power transmission efficiency of the converter. In addition, the values ​​of each control variable need to be pre-calculated offline during the control process, and the execution of the control scheme requires the use of multidimensional lookup tables and linear interpolation methods, resulting in a large amount of computation and overall control complexity. Summary of the Invention

[0006] The purpose of this invention is to provide a ZVS control method and system for a four-switch Buck-Boost converter, which solves the problems of existing ZVS control methods for four-switch Buck-Boost converters having circulating current freewheeling links and requiring all control variable values ​​to be pre-calculated offline, resulting in increased effective value of inductor current and converter conduction losses, as well as complex overall control.

[0007] To achieve the above objectives, this invention provides a ZVS control method for a four-switch Buck-Boost converter. The four-switch Buck-Boost converter includes first, second, third, and fourth switches and an inductor connected at both ends between the first and third switches, and between the second and fourth switches, respectively. Within each switching cycle of the four-switch Buck-Boost converter, three time periods are defined, consisting of the first, second, third, and fourth time nodes. Based on the minimum conduction loss ZVS constraint conditions corresponding to different operating modes of the four-switch Buck-Boost converter, the current waveform of the inductor is controlled accordingly within each time period.

[0008] The first and fourth time nodes are the start and end times of the switching cycle, respectively; the second and third time nodes are the switching times of the first and second switching transistors, respectively.

[0009] The beneficial effects of the above technical solution are as follows: by designing the first, second, third and fourth time nodes, a switching cycle is divided into three segments for ZVS control, eliminating the circulating current freewheeling link in the existing quadrilateral inductor current control, significantly reducing the effective value of the inductor current, and improving the power transmission efficiency of the converter; and setting the minimum on-state loss ZVS constraint condition, thereby reducing the on-state loss of the converter.

[0010] Furthermore, based on the minimum on-state loss ZVS constraint condition corresponding to different operating modes of the four-switch Buck-Boost converter, the method for controlling the current waveform of the inductor in different time periods is as follows:

[0011] Based on the minimum on-state loss ZVS constraint condition corresponding to different operating modes of the four-switch Buck-Boost converter, the values ​​of the corresponding control variables are determined; by adjusting the control variables, the current waveform of the inductor is controlled accordingly in different time periods.

[0012] The beneficial effects of the above technical solution are as follows: by independently analyzing the characteristics of each working mode of the converter, setting targeted minimum conduction loss ZVS constraint control conditions and corresponding control variables for specific adjustment, the minimum conduction loss ZVS control of each working mode can be achieved at the same time while simplifying the calculation process, which can effectively reduce the conduction loss of the converter.

[0013] Furthermore, the minimum on-state loss ZVS constraint for the Boost mode of the four-switch Buck-Boost converter is:

[0014]

[0015] Among them, i L(0) i L(2) and i L(3) These are the inductor currents at the first, third, and fourth time nodes, respectively; I0 is the minimum current required to charge and discharge the output capacitors of the two switching transistors in the half-bridge of a four-switch Buck-Boost converter.

[0016] The control variables include the switching frequency corresponding to the switching cycle and the duty cycle of the trigger pulses of the first and second switching transistors within each switching cycle:

[0017]

[0018] f = 1 / t³

[0019] Where t0, t1, t2 and t3 are the first, second, third and fourth time nodes, respectively; D1 and D2 are the duty cycles of the trigger pulses of the first and second switching transistors in each switching cycle, respectively; and f is the switching frequency corresponding to the switching cycle.

[0020] The beneficial effects of the above technical solution are as follows: Based on the characteristics of the converter's Boost operating mode, targeted minimum conduction loss ZVS constraint control conditions and corresponding control variables for specific adjustment are set. On the basis of simplifying the calculation process, minimum conduction loss ZVS control is achieved for each operating mode, which can effectively reduce the conduction loss of the converter.

[0021] Furthermore, the minimum on-state loss ZVS constraint for the Buck operating mode of the four-switch Buck-Boost converter is as follows:

[0022]

[0023] Among them, i L(0) i L(1) and i L(3) These are the inductor currents at the first, second, and fourth time nodes, respectively; I0 is the minimum current required to charge and discharge the output capacitors of the two switching transistors in the half-bridge of a four-switch Buck-Boost converter.

[0024] The control variables include the switching frequency corresponding to the switching cycle and the duty cycle of the trigger pulses of the first and second switching transistors within each switching cycle:

[0025]

[0026] f = 1 / t³

[0027] Where t0, t1, t2 and t3 are the first, second, third and fourth time nodes, respectively; D1 and D2 are the duty cycles of the trigger pulses of the first and second switching transistors in each switching cycle, respectively; and f is the switching frequency corresponding to the switching cycle.

[0028] The beneficial effects of the above technical solution are as follows: Based on the characteristics of the converter's Buck operating mode, targeted ZVS constraint control conditions for minimizing conduction loss and corresponding control variables for specific adjustment are set. On the basis of simplifying the calculation process, the minimum conduction loss ZVS control of each operating mode is realized at the same time, which can effectively reduce the conduction loss of the converter.

[0029] Furthermore, the minimum on-state loss ZVS constraint for the Buck-Boost operating mode of the four-switch Buck-Boost converter is as follows:

[0030] i L(0) =i L(3) =-I0

[0031]

[0032] In the formula, i L(0) and i L(3) These are the inductor currents at the first and fourth time nodes, respectively; I0 is the minimum current required to charge and discharge the output capacitors of the two switches in the half-bridge of a four-switch Buck-Boost converter; f Buck-Boost This refers to the switching frequency corresponding to the switching cycle in Buck-Boost operating mode. This refers to the switching frequency of the Buck-mode converter with an input voltage of U' at the same output power, compared to the current Buck-Boost operating mode; where U1 is the input voltage of the four-switch Buck-Boost converter, U' is the minimum input voltage in Buck operating mode, and I... out This represents the output current of the four-switch Buck-Boost converter.

[0033] The beneficial effects of the above technical solution are as follows: Based on the characteristics of the Buck-Boost working mode of the converter, targeted ZVS constraint control conditions for minimizing conduction loss and corresponding control variables for specific adjustment are set. On the basis of simplifying the calculation process, the minimum conduction loss ZVS control of each working mode is realized at the same time, which can effectively reduce the conduction loss of the converter.

[0034] Furthermore, when switching between Boost mode and Buck-Boost mode, the output of the PI regulator in ZVS control is set to meet the following conditions in both Buck-Boost and Boost modes:

[0035]

[0036] Among them, V PI-Buck-Boost V is the output of the PI regulator in ZVS control during Buck-Boost operation. PI-Boost U1' is the output of the PI regulator in ZVS control during Boost mode; U2' is the input voltage corresponding to the switching point between Boost mode and Buck-Boost mode; and U2 is the output voltage of the four-switch Buck-Boost converter. 1-Boost (U1') represents the duty cycle of the trigger pulse of the first switch in each switching cycle during the Boost operating mode when the four-switch Buck-Boost converter operates in U1' mode. 1-Buck-Boost (U1') is the duty cycle of the trigger pulse of the first switch in each switching cycle when the four-switch Buck-Boost converter is operating in U1' mode.

[0037] The beneficial effects of the above technical solution are as follows: when the converter switches between Boost operating mode and Buck-Boost operating mode, a corresponding jump value is added to the output of the PI regulator in the ZVS constant voltage closed-loop control of the converter. This ensures that when the converter switches modes, as the calculation formula of the control quantity corresponding to the constraint control condition changes, the output of the PI regulator can jump simultaneously, and the voltage gain of the converter remains unchanged before and after the jump, so that the output voltage is stable before and after the jump. This allows the converter to achieve smooth mode switching and avoids voltage distortion caused by mode switching.

[0038] Furthermore, when switching between Buck operating mode and Buck-Boost operating mode, the output of the PI regulator in ZVS control is set to meet the following conditions in both Buck-Boost and Buck operating modes:

[0039]

[0040] Among them, V PI-Buck V is the output of the PI regulator in ZVS control during Buck operation mode. PI-Buck-BoostU1 is the output of the PI regulator in ZVS control during Buck-Boost operation; U2 is the input voltage corresponding to the switching point between Buck operation mode and Buck-Boost operation mode; D is the output voltage of the four-switch Buck-Boost converter. 1-Buck (U1") represents the duty cycle of the trigger pulse of the first switch in each switching cycle during the Buck operating mode when the four-switch Buck-Boost converter operates in U1”. 1-Buck-Boost (U1") is the duty cycle of the trigger pulse of the first switch in each switching cycle when the four-switch Buck-Boost converter is operating in U1” mode.

[0041] The beneficial effects of the above technical solution are as follows: when the converter switches between Buck operating mode and Buck-Boost operating mode, a corresponding jump value is added to the output of the PI regulator in the corresponding ZVS constant voltage closed-loop control of the converter. This ensures that when the converter switches modes, as the calculation formula of the control quantity corresponding to the constraint control condition changes, the output of the PI regulator can jump simultaneously, and the voltage gain of the converter remains unchanged before and after the jump, so that the output voltage is stable before and after the jump. This allows the converter to achieve smooth mode switching and avoids voltage distortion caused by mode switching.

[0042] Furthermore, based on the minimum on-state loss ZVS constraint conditions corresponding to different operating modes of the four-switch Buck-Boost converter, the methods for determining the values ​​of the corresponding control variables include:

[0043] Based on the minimum conduction loss ZVS constraint condition corresponding to the Boost operating mode of the four-switch Buck-Boost converter, the switching frequency corresponding to the switching cycle and the duty cycle of the trigger pulses of the first and second switches in each switching cycle are determined as follows:

[0044]

[0045] In the formula, D1 and D2 are the duty cycles of the trigger pulses of the first and second switches in each switching cycle, respectively; f is the switching frequency corresponding to the switching cycle; U1 and U2 are the input and output voltages of the four-switch Buck-Boost converter, respectively; I out I0 is the output current of the four-switch Buck-Boost converter; I0 is the minimum current required to charge and discharge the output capacitors of the two switches in the half-bridge of the four-switch Buck-Boost converter; L is the inductance value of the inductor connected at both ends between the first and third switches, and between the second and fourth switches, respectively.

[0046] The beneficial effects of the above technical solution are as follows: it can calculate a part of the control variables by instantaneously detecting the parameters of the circuit and the reference constant, and simultaneously adjust another part of the control variables through the output of the closed-loop PI regulator; this simplifies the soft-switching calculation process, and through the real-time online detection and calculation of the DSP, it can simultaneously realize the real-time closed-loop control of the Boost mode frequency converter and the ZVS of each switching transistor, with minimal conduction loss, no need for offline pre-calculation, and no need to use multidimensional lookup tables and linear interpolation methods, making the overall control simpler and easier to implement.

[0047] Furthermore, based on the minimum on-state loss ZVS constraint conditions corresponding to different operating modes of the four-switch Buck-Boost converter, the methods for determining the values ​​of the corresponding control variables include:

[0048] Based on the minimum conduction loss ZVS constraint condition corresponding to the Buck operating mode of the four-switch Buck-Boost converter, the switching frequency corresponding to the switching cycle and the duty cycle of the trigger pulses of the first and second switches in each switching cycle are determined as follows:

[0049]

[0050] In the formula, D1 and D2 are the duty cycles of the trigger pulses of the first and second switches in each switching cycle, respectively; f is the switching frequency corresponding to the switching cycle; U1 and U2 are the input and output voltages of the four-switch Buck-Boost converter, respectively; I out I0 is the output current of the four-switch Buck-Boost converter; I0 is the minimum current required to charge and discharge the output capacitors of the two switches in the half-bridge of the four-switch Buck-Boost converter; L is the inductance value of the inductor connected at both ends between the first and third switches, and between the second and fourth switches, respectively.

[0051] The beneficial effects of the above technical solution are as follows: it can calculate a part of the control variables by instantaneously detecting the parameters of the circuit and the reference constant, and simultaneously adjust another part of the control variables through the output of the closed-loop PI regulator; this simplifies the soft-switching calculation process, and through the real-time online detection and calculation of the DSP, it can simultaneously realize the real-time closed-loop control of the Boost mode frequency converter and the ZVS of each switching transistor, with minimal conduction loss, no need for offline pre-calculation, and no need to use multidimensional lookup tables and linear interpolation methods, making the overall control simpler and easier to implement.

[0052] The present invention also provides a ZVS control system for a four-switch Buck-Boost converter, including a processor for executing program instructions to implement the ZVS control method for the four-switch Buck-Boost converter as described above.

[0053] This control system can achieve the same beneficial effects as the ZVS control method for the four-switch Buck-Boost converter described above. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the structure of a four-switch Buck-Boost converter in the background art of this invention;

[0055] Figure 2 This is the control timing diagram of the quadrilateral inductor current ZVS control strategy in the background art of this invention;

[0056] Figure 3 This is a control timing diagram of the ZVS control method for a four-switch Buck-Boost converter in an embodiment of the present invention.

[0057] Figure 4 In an embodiment of the ZVS control method for a four-switch Buck-Boost converter of the present invention, the effective value of the inductor current I when the power is 500W in Boost operating mode is... L A three-dimensional surface diagram formed by the input voltages U1 and t3;

[0058] Figure 5 In an embodiment of the ZVS control method for a four-switch Buck-Boost converter of the present invention, the effective value of the inductor current I in the Buck operating mode at a power of 500W is... L A three-dimensional surface diagram formed by the input voltages U1 and t3;

[0059] Figure 6 This is a schematic diagram of the control timing corresponding to the minimum on-state loss ZVS constraint in the Boost operating mode of an embodiment of the ZVS control method for a four-switch Buck-Boost converter according to the present invention.

[0060] Figure 7 This is a schematic diagram of the control timing corresponding to the minimum on-state loss ZVS constraint in the Buck operating mode of an embodiment of the ZVS control method for a four-switch Buck-Boost converter according to the present invention.

[0061] Figure 8 In an embodiment of the ZVS control method for a four-switch Buck-Boost converter of the present invention, the switching frequency f, input voltage U1, and load current i are as follows when the power is 500W in Boost and Buck operating modes: out A three-dimensional surface diagram showing the relationship between them;

[0062] Figure 9This is a block diagram of the ZVS constant voltage closed-loop control system corresponding to the ZVS control method of a four-switch Buck-Boost converter in an embodiment of the present invention.

[0063] Figure 10a This is a schematic diagram of the closed-loop steady-state waveform of an input voltage of 75V in the Boost operating mode when the output power is 500W in an embodiment of the ZVS control method of a four-switch Buck-Boost converter of the present invention.

[0064] Figure 10b This is a schematic diagram of the closed-loop steady-state waveform of a Buck-Boost converter with an input voltage of 100V in Buck-Boost operating mode when the output power is 500W in an embodiment of the ZVS control method of a four-switch Buck-Boost converter according to the present invention.

[0065] Figure 10c This is a schematic diagram of the closed-loop steady-state waveform of a four-switch Buck-Boost converter ZVS control method embodiment of the present invention, where the output power is 500W and the input voltage is 125V in Buck mode.

[0066] Figure 11a This is a schematic diagram of the closed-loop steady-state waveform of an input voltage of 75V in the Boost operating mode when the output power is 100W in an embodiment of the ZVS control method of a four-switch Buck-Boost converter of the present invention.

[0067] Figure 11b This is a schematic diagram of the closed-loop steady-state waveform of a Buck-Boost converter with an input voltage of 100V in the Buck-Boost operating mode when the output power is 100W, according to an embodiment of the ZVS control method of a four-switch Buck-Boost converter of the present invention.

[0068] Figure 11c This is a schematic diagram of the closed-loop steady-state waveform of a four-switch Buck-Boost converter ZVS control method embodiment of the present invention, where the output power is 100W and the input voltage is 125V in Buck mode.

[0069] Figure 12a This is a schematic diagram illustrating the output voltage change during the switching process of the converter from Boost mode to Buck-Boost and back to Buck mode when the power is 500W and the input voltage increases from 85V to 115V in an embodiment of the ZVS control method for a four-switch Buck-Boost converter according to the present invention.

[0070] Figure 12bThis is a schematic diagram illustrating the output voltage change during the switching process of the converter from Boost mode to Buck-Boost and back to Buck mode when the power is 100W and the input voltage increases from 85V to 115V in an embodiment of the ZVS control method of a four-switch Buck-Boost converter according to the present invention.

[0071] Figure 12c This is a schematic diagram illustrating the output voltage change during the switching process of the converter from Boost mode to Buck-Boost and then back to Buck mode when the power is 500W and the input voltage drops from 115V to 85V in an embodiment of the ZVS control method for a four-switch Buck-Boost converter according to the present invention.

[0072] Figure 12d This is a schematic diagram illustrating the output voltage change during the switching process of the converter from Boost mode to Buck-Boost and back to Buck mode when the power is 100W and the input voltage drops from 115V to 85V in an embodiment of the ZVS control method for a four-switch Buck-Boost converter according to the present invention.

[0073] Figure 13a This is a waveform diagram showing the output power switching from 500W to 100W when the input voltage is 80V in Boost mode, according to an embodiment of the ZVS control method for a four-switch Buck-Boost converter of the present invention.

[0074] Figure 13b This is a waveform diagram illustrating the switching of output power from 500W to 100W in Buck-Boost mode when the input voltage is 100V, according to an embodiment of the ZVS control method for a four-switch Buck-Boost converter of the present invention.

[0075] Figure 13c This is a waveform diagram showing the output power switching from 500W to 100W when the input voltage is 120V in Buck mode, according to an embodiment of the ZVS control method for a four-switch Buck-Boost converter of the present invention.

[0076] Figure 14 This is a schematic diagram of the efficiency curves of a four-switch Buck-Boost converter under a wide input voltage range and different power levels, as shown in an embodiment of the ZVS control method for a Buck-Boost converter according to the present invention. Detailed Implementation

[0077] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0078] An embodiment of a ZVS control method for a four-switch Buck-Boost converter

[0079] This embodiment presents a technical solution for ZVS control of a four-switch Buck-Boost converter. The specific structure of the four-switch Buck-Boost converter is described in [reference needed]. Figure 1 Including the first, second, third, and fourth switching transistors (corresponding to respectively) Figure 1 The switching transistors S1, S2, and S3 in the middle 1S and S 2S ) and the inductors whose two ends are respectively connected between the first and third switching transistors, and between the second and fourth switching transistors (corresponding to Figure 1 (The inductor L in the example); It should be noted that all "converters" mentioned in this embodiment refer to such a four-switch Buck-Boost converter structure.

[0080] Within each switching cycle of the four-switch Buck-Boost converter, three time periods are defined by the first, second, third, and fourth time nodes. The first and fourth time nodes represent the start and end times of the switching cycle, respectively; the second and third time nodes represent the switching times of the first and second switches, respectively. The specific timing diagram is shown below. Figure 3 As shown, t0, t1, t2 and t3 are the first, second, third and fourth time nodes, respectively.

[0081] Based on the minimum on-state loss ZVS constraint condition corresponding to different operating modes of the four-switch Buck-Boost converter, the current waveform of inductor L is controlled accordingly at different time periods, specifically as follows:

[0082] Based on the minimum conduction loss (ZVS) constraint condition corresponding to different operating modes of the four-switch Buck-Boost converter, the values ​​of the corresponding control variables are determined. In this embodiment, the control variables include the switching frequency f corresponding to the switching cycle and the duty cycles D1 and D2 of the trigger pulses of the first and second switches in each switching cycle; refer to Figure 3 These control variables correspond to the first, second, third, and fourth time nodes within each switching cycle, as shown in the following formula (for simplified calculation, the starting time t0 is set to 0):

[0083]

[0084] f = 1 / t³

[0085] By adjusting the control variables, the current waveform of inductor L can be controlled accordingly at different time periods, thus achieving ZVS control of the four-switch Buck-Boost converter; in the existing quadrilateral inductor current ZVS control strategy timing diagram (i.e. Figure 2 ) t3-T of the inductor current waveform P In the first segment, the converter does not transmit power to the load. This segment is a simple circulating current freewheeling link, which increases the converter's conduction losses. Compared with the prior art, the ZVS control method in this embodiment can eliminate the circulating current freewheeling link of the inductor current in the quadrilateral control scheme, reduce the effective value of the inductor current and the conduction losses of the converter, and improve the power transmission efficiency of the converter.

[0086] To achieve ZVS switching of the four switches in a four-switch Buck-Boost converter, the following conditions must be met:

[0087] |i L(0) |,i L(1) i L(2) ,|i L(3) |≥I0

[0088] Among them, i L(0) i L(1) i L(2) and i L(3) These are the inductor currents at the first, second, third, and fourth time nodes, respectively. Where I0 is the minimum current required to charge and discharge the output capacitors of the two switches in the half-bridge; C oss These are the output capacitors of each switching transistor; U1 and U2 are the input and output voltages of the four-switch Buck-Boost converter, respectively, and L represents... Figure 1 Let the inductance value of inductor L be given; let the initial value of the inductor current be i. L( t 0) =-I0, then the inductor current i in one switching cycle can be obtained. L( t ) The expression is:

[0089]

[0090] To achieve ZVS turn-on for each switch in a four-switch Buck-Boost converter, the inductor current needs to be -I0 at both times t0 and t3, i.e.:

[0091]

[0092] The relationship between t1, t2, and t3 can then be derived as follows:

[0093]

[0094] Based on the correspondence between the control variables and the first, second, third, and fourth time nodes within each switching cycle, the following formula is obtained:

[0095] D2=U1D1 / U2

[0096] like Figure 3 As shown, since switch S1 is only turned on between t0 and t2, the current flowing through switch S1 can be expressed as follows:

[0097]

[0098] Similarly, switch S2 is only turned on between t1 and t3, so the current flowing through switch S2 can be expressed as follows:

[0099]

[0100] The input power P1 of the four-switch Buck-Boost converter can be calculated as follows:

[0101]

[0102] Based on the correspondence between the control variables and the first, second, third, and fourth time nodes within each switching cycle, we can obtain:

[0103]

[0104] Similarly, the output power P2 of the four-switch Buck-Boost converter can be obtained as follows:

[0105]

[0106] Based on the correspondence between the control variables and the first, second, third, and fourth time nodes within each switching cycle, we can obtain:

[0107]

[0108] Due to the different input voltages U1 and power P1, the effective value of the inductor current I L The relationship between t3 and t3 is:

[0109] I L =f2(U1,t3,P1)

[0110] Then, based on this relationship, under a fixed power, I L The three-dimensional surface plot between U1 and t3 is as follows: Figure 4 As shown; the four-switch Buck-Boost converter includes three operating modes: Boost, Buck-Boost, and Buck. Figure 4 The document provides the effective value of the inductor current I when the power is 500W in Boost mode (since the input power equals the output power when the converter is running stably, the term "power" is used here for consistency). L The three-dimensional surface plots between U1 and t3, and the constraints of t3 must guarantee Figure 3 the inductor current i at time t2 L(2) is greater than or equal to I0 (3A in this embodiment); Figure 4 , when the input voltage U1 is fixed, I L decreases monotonically as t3 increases.

[0111] Similarly, Figure 5 shows a 3D surface plot of the inductor current RMS value I at a power of 500W under the Buck operation mode, the constraint condition of t3 in the drawing shall ensure that between U1 and t3 Figure 3 the inductor current i at time t1 L(1) is greater than or equal to I0; Figure 5 , when the input voltage U1 is fixed, I L decreases monotonically as t3 increases. It can be seen that, in the ZVS control method of this embodiment, when the power is fixed, a larger t3 corresponds to a smaller RMS value of the inductor current at the same input voltage point, so that the on-state loss of the converter is smaller; therefore, the following minimum on-state loss ZVS constraint is set, under the condition that soft switching of all switching tubes can be realized, each operation mode of the four-switch Buck-Boost converter has the maximum t3 value, so that each operation mode has the minimum on-state loss:

[0112] ① Minimum on-state loss ZVS constraint corresponding to the Boost operation mode:

[0113] As shown in Figure 3 , in the [t1, t2] phase of the Boost mode, the driving pulse u of the switching tube S1 g1 and the driving pulse u of the switching tube S2 g2 are at high level at the same time, S1 and S2 are turned on simultaneously, so the input voltage U1 and the output voltage U2 of the converter are directly connected through the inductor L. Since U1 < U2 always holds in the Boost mode, the inductor current continuously decreases in the [t1, t2] phase, that is, i always holds in the Boost mode L(1) > i L(2) .

[0114] From the above Figure 4 , it can be obtained that to minimize the on-state loss and maximize the efficiency of the converter in the Boost mode, it is necessary to minimize the RMS value of the inductor current, that is, to ensure the maximum t3 value; as shown in Figure 3 , for any operating point with fixed power and input / output voltage, as t3 increases, i L(1) and i L(2) decrease simultaneously, and i always holds in the Boost mode L(1) > i L(2) , then when i L(2)When reduced to I0, t3 increases to its maximum under the condition that soft switching of each switching transistor can be achieved; therefore, the minimum conduction loss ZVS constraint condition of the Boost operating mode in this embodiment is as follows:

[0115]

[0116] Among them, i L(0) i L(2) and i L(3) These represent the inductor currents at the first, third, and fourth time nodes, respectively; I0 is the minimum current required to charge and discharge the output capacitors of the two switches in the half-bridge of a four-switch Buck-Boost converter; the corresponding control timing diagram is shown below. Figure 6 As shown, Figure 6 The point marked by the dashed coil is the time node and inductor current value corresponding to the constraint condition.

[0117] Furthermore, when the converter is running stably, the equation P1 = P2 = U2I always holds. out Then, the three control variables f, D1, and D2 corresponding to the minimum on-state loss ZVS constraint condition for the Boost operating mode are calculated as follows:

[0118]

[0119] In the formula, D1 and D2 are the duty cycles of the trigger pulses of the first and second switches in each switching cycle, respectively; f is the switching frequency corresponding to the switching cycle; U1 and U2 are the input and output voltages of the four-switch Buck-Boost converter, respectively; I out I0 is the output current of the four-switch Buck-Boost converter; I0 is the minimum current required to charge and discharge the output capacitors of the two switches in the half-bridge of the four-switch Buck-Boost converter; L is the inductance value of the inductors connected at both ends between the first and third switches, and between the second and fourth switches, respectively.

[0120] Based on the minimum on-state loss ZVS constraint condition corresponding to the above Boost operating mode, adjusting these three control variables allows for corresponding control of the current waveform of inductor L in different time periods. This is because when the converter achieves closed-loop control, D2 = U1D1 / U2 always holds true, and U2 equals the output voltage reference value U. ref Therefore, the instantaneous detection circuit's U1 and i out And assign U2 the reference constant U of the output voltage. refSubstitute these values ​​into the above formula to calculate D1 and f; simultaneously, adjust D2 through the output of the closed-loop PI regulator; this simplifies the soft-switching calculation process and enables real-time online detection and calculation by the DSP, achieving real-time closed-loop control of Boost mode frequency converter and ZVS of each switching transistor, with minimal conduction losses. It eliminates the need for offline pre-calculation and the use of multidimensional lookup tables and linear interpolation methods, making the overall control simpler and easier to implement.

[0121] ②ZVS constraint for minimum on-state loss in Buck operating mode:

[0122] Similar to Boost mode, such as Figure 3 As shown, in the [t1,t2] phase of Buck mode, the driving pulse u of the switching transistor S1 g1 The driving pulse u of the switching transistor S2 g2 At the same time, the voltage level is high, and both S1 and S2 are turned on. Figure 1 The input voltage U1 and output voltage U2 are directly connected through inductor L; in Buck mode, U1 > U2, so the inductor current will continue to increase during the [t1,t2] phase, meaning that in Buck mode, i L(1) L(2) .

[0123] Depend on Figure 5 Therefore, in Buck mode, to minimize the converter's on-state losses and maximize efficiency, the effective value of the inductor current must be minimized, which requires ensuring the maximum t3 value. For example... Figure 3 As shown, for any operating point with fixed power and input / output voltage, as t3 increases, i L(1) and i L(2) They will decrease simultaneously. In Buck pattern, there is always i. L(1) L(2) Then when i L(1) When reduced to I0, t3 increases to its maximum under the condition that soft switching of each switching transistor can be achieved. Therefore, the minimum on-state loss ZVS constraint condition corresponding to the Buck operating mode in this embodiment is as follows:

[0124]

[0125] Among them, i L(0) i L(1) and i L(3) These represent the inductor currents at the first, second, and fourth time nodes, respectively; I0 is the minimum current required to charge and discharge the output capacitors of the two switches in the half-bridge of the four-switch Buck-Boost converter; the corresponding control timing diagram is shown below. Figure 7 As shown, Figure 7 ​​The point marked by the dashed coil is the time node and inductor current value corresponding to the constraint condition.

[0126] Similarly, the three control variables f, D1, and D2 corresponding to the ZVS constraint condition that satisfies the minimum on-state loss for the Buck operating mode are calculated as follows:

[0127]

[0128] In the formula, D1 and D2 are the duty cycles of the trigger pulses of the first and second switches in each switching cycle, respectively; f is the switching frequency corresponding to the switching cycle; U1 and U2 are the input and output voltages of the four-switch Buck-Boost converter, respectively; I out I0 is the output current of the four-switch Buck-Boost converter; I0 is the minimum current required to charge and discharge the output capacitors of the two switches in the half-bridge of the four-switch Buck-Boost converter; L is the inductance value of the inductors connected at both ends between the first and third switches, and between the second and fourth switches, respectively.

[0129] Similarly, based on the minimum on-state loss ZVS constraint condition corresponding to the Buck operating mode, adjusting these three control variables allows for corresponding control of the current waveform of inductor L in different time periods. This is because when the converter achieves closed-loop control, D2 = U1D1 / U2 always holds true, and U2 equals the output voltage reference value U. ref Therefore, the instantaneous detection circuit's U1 and i out And assign U2 the reference constant U of the output voltage. ref Substitute these values ​​into the above formula to calculate D1 and f; simultaneously, adjust D2 through the output of the closed-loop PI regulator; this simplifies the soft-switching calculation process and enables real-time online detection and calculation by the DSP, achieving real-time closed-loop control of Buck mode frequency converter and ZVS of each switching transistor, with minimal conduction losses. It eliminates the need for offline pre-calculation and the use of multidimensional lookup tables and linear interpolation methods, making the overall control simpler and easier to implement.

[0130] ③ The minimum on-state loss ZVS constraint for Buck-Boost operating mode:

[0131] Based on the three control variables f, D1, and D2 that satisfy the ZVS constraint for minimum on-state loss in Boost and Buck operating modes, we can obtain the switching frequency f, input voltage U1, and load current i in Boost and Buck operating modes. out A three-dimensional surface diagram showing the relationship between them (output power 500W), such as... Figure 8 As shown;

[0132] When the output power is 500W, the switching frequencies corresponding to the special input voltage points in the Boost and Buck modes of the three-stage inverter ZVS control are shown in Table 1 and Table 2 below, respectively:

[0133] Table 1. Switching frequency under wide input range in Boost mode at 500W power.

[0134]

[0135] Table 2 Switching frequency under Buck mode wide-range input at 500W power

[0136]

[0137] In this embodiment, the input voltage range for Boost mode is 50–92V, and for Buck mode it is 108–150V. Setting the input voltage range to 92–108V corresponds to Buck-Boost mode. When the converter enters this mode range, it maintains its switching frequency at the same power level corresponding to a 108V input. Thus, at a power of 500W, the converter's switching frequency ranges from 105–307kHz across the wide input voltage range of 50–150V. As the transmission power decreases, the converter's switching frequency gradually increases, and the upper limit of the switching frequency is determined by the characteristics of the switching transistor.

[0138] Because within the 92-108V input range for the same power, the switching frequency is highest (i.e., the shortest switching cycle) at an input voltage of 108V (the minimum input voltage in Buck mode, which can also be considered the switching point between Buck mode and Buck-Boost mode). Therefore, maintaining the switching cycle of Buck-Boost mode at the shortest switching cycle corresponding to a 108V input in Buck mode for the same power ensures the correct switching frequency across the entire Buck-Boost mode range. L(1) and i L(2) The values ​​of all values ​​are greater than I0, enabling ZVS turn-on of all switches; otherwise, if the Buck-Boost mode maintains the switching cycle corresponding to the 92V input in Boost mode, then when the converter operates near the 108V input operating point in Buck-Boost mode, because the maintained constant switching cycle is greater than the switching cycle corresponding to the 108V input point in the original Buck mode, it will cause the i value corresponding to the input point near 108V to be higher. L(1) If the value is less than I0, ZVS turn-on of all switching transistors cannot be achieved.

[0139] Therefore, in the 92–108V input range of Buck-Boost mode, to satisfy the minimum conduction loss (ZVS) constraint, the control variable f needs to maintain the switching frequency corresponding to the 108V input in Buck mode at the same power. Thus, the minimum conduction loss (ZVS) constraint for the Buck-Boost operating mode of the four-switch Buck-Boost converter is:

[0140] i L(0) =i L(3) =-I0

[0141]

[0142] In the formula, i L(0) and i L(3) These are the inductor currents at the first and fourth time nodes, respectively; I0 is the minimum current required to charge and discharge the output capacitors of the two switches in the half-bridge of a four-switch Buck-Boost converter; f Buck-Boost This refers to the switching frequency corresponding to the switching cycle in Buck-Boost operating mode. This refers to the switching frequency of the Buck-mode converter with an input voltage of U' at the same output power, compared to the current Buck-Boost operating mode; where U1 is the input voltage of the four-switch Buck-Boost converter, U' is the minimum input voltage in Buck operating mode, and I... out This represents the output current of the four-switch Buck-Boost converter.

[0143] Similarly, by adjusting these three control variables according to the minimum on-state loss ZVS constraint condition corresponding to the Buck-Boost operating mode, the current waveform of inductor L can be controlled accordingly at different time periods; this can be achieved by instantaneously detecting U1 and i... out And assign U2 the reference constant U of the output voltage. ref Substitute these values ​​into the above formula to calculate D1 and f; simultaneously, adjust D2 through the output of the closed-loop PI regulator. This simplifies the soft-switching calculation process and enables real-time online detection and calculation by the DSP, achieving real-time closed-loop control of Buck-Boost mode frequency converter and ZVS of each switching transistor, with minimal conduction losses. It eliminates the need for offline pre-calculation and the use of multidimensional lookup tables and linear interpolation methods, making the overall control simpler and easier to implement.

[0144] Furthermore, the block diagram of the ZVS constant pressure closed-loop control system corresponding to the control method in this embodiment is as follows: Figure 9As shown, since the calculation formulas for D1 and f are different between the three operating modes, a jump will occur during mode switching. In order to ensure smooth switching between modes and smooth and continuous voltage gain, it is necessary to adjust the output of the PI regulator to jump simultaneously when the calculation formulas for D1 and f jump during mode switching, and it is also necessary to ensure that the duty cycle generated by the PI regulator after the jump can make the voltage gain of the converter the same as before the jump.

[0145] The output of the PI controller in the three modes is represented by V. PI-Boost V PI-Buck-Boost and V PI-Buck It means, and as Figure 9 As shown, the output of the closed-loop PI controller is S. 2S Duty cycle D 2S V PI-Boost =D 2S-Boost V PI-Buck-Boost =D 2S-Buck-Boost Meanwhile, V PI-Buck =D 2S-Buck In Boost mode, D1 uses D. 1-Boost (U1') indicates that D1 in Buck-Boost mode is set to D. 1-Buck-Boost (U1') indicates that the limiting range of the PI regulator is set to 0 to 1. In this embodiment, the input voltage U1' = 92V is set as the switching point between Boost mode and Buck-Boost mode, and the input voltage U1” = 108V is set as the switching point between Buck-Boost mode and Buck mode. To ensure a smooth switching between Boost mode and Buck-Boost mode, the voltage gain of the converter on both sides of the mode switching point must be equal, that is, the following formula must be true:

[0146]

[0147] Here, x represents the jump variable that the PI regulator in Boost mode needs to add when switching between Boost and Buck-Boost modes. Based on the minimum on-state loss ZVS constraint condition corresponding to the Buck-Boost operating mode of the four-switch Buck-Boost converter, the jump variable x of the PI regulator can be calculated as follows:

[0148] x = 0.92(D) 1-Boost (92)-D 1-Buck-Boost (92))

[0149] Where 0.92 is... The value 92 is the value of U1'; that is, when switching between Boost mode and Buck-Boost mode, the output of the PI regulator in ZVS control in Buck-Boost mode and Boost mode must meet the following conditions:

[0150]

[0151] Among them, V PI-Buck-Boost V is the output of the PI regulator in ZVS control during Buck-Boost operation. PI-Boost U1' is the output of the PI regulator in ZVS control during Boost mode; U2' is the input voltage corresponding to the switching point between Boost mode and Buck-Boost mode; and U2 is the output voltage of the four-switch Buck-Boost converter. 1-Boost (U1') represents the duty cycle of the trigger pulse of the first switch in each switching cycle during the Boost operating mode when the four-switch Buck-Boost converter operates in U1' mode. 1-Buck-Boost (U1') is the duty cycle of the trigger pulse of the first switch in each switching cycle when the four-switch Buck-Boost converter is operating in U1' mode.

[0152] If the output of the PI regulator in ZVS control meets the above conditions in Buck-Boost and Boost modes, it can be guaranteed that when switching between Boost and Buck-Boost modes, the output of the PI regulator will change simultaneously with the change in the D1 calculation formula, and the voltage gain of the converter will remain unchanged before and after the change, thus ensuring the stability of the output voltage before and after the change, thereby enabling the converter to achieve smooth mode switching.

[0153] Similarly, when switching between Buck operating mode and Buck-Boost operating mode, the jump variable x of the PI controller is:

[0154] x = 1.08 (D 1-Boost (108)-D 1-Buck-Boost (108))

[0155] Among them, 1.08 is The value of 108 is the value of U1; that is, the output of the PI regulator in ZVS control in Buck-Boost mode and Buck mode satisfies the following conditions:

[0156]

[0157] Among them, V PI-BuckV is the output of the PI regulator in ZVS control during Buck operation mode. PI-Buck-Boost U1 is the output of the PI regulator in ZVS control during Buck-Boost operation; U2 is the input voltage corresponding to the switching point between Buck operation mode and Buck-Boost operation mode; D is the output voltage of the four-switch Buck-Boost converter. 1-Buck (U1") represents the duty cycle of the trigger pulse of the first switch in each switching cycle during the Buck operating mode when the four-switch Buck-Boost converter operates in U1”. 1-Buck-Boost (U1") represents the duty cycle of the trigger pulse of the first switching transistor in each switching cycle when the four-switch Buck-Boost converter operates in U1" mode. This ensures that when switching between Buck mode and Buck-Boost mode, the output of the PI regulator changes simultaneously with the change in the D1 calculation formula, maintaining a constant voltage gain before and after the change, thus ensuring stable output voltage and smooth mode switching.

[0158] When the output power is 500W, using the control method of this embodiment, the steady-state waveforms of the converter in each operating mode are as follows: Figures 10a-10c As shown; considering the conduction loss in the circuit and the stability of the system, I0 is set to 3A during the experiment;

[0159] Figure 10a The closed-loop steady-state waveform is shown in Boost mode with an input voltage of 75V and a switching frequency of 149kHz. L(0) =i L(3) =-3A, i L(2) =3A, and Figure 6 The minimum on-state loss ZVS constraint set in the original text is consistent; Figure 10b The waveform shown is the closed-loop steady-state waveform in Buck-Boost operating mode with an input voltage of 100V and a switching frequency of 122.9kHz. L(0) =i L(3) =-3A, i L(1) ≥3A, i L(2) ≥3A, consistent with the minimum on-state loss ZVS constraint condition corresponding to the Buck-Boost operating mode; Figure 10c The waveform represents the closed-loop steady-state waveform in Buck mode with an input voltage of 125V and a switching frequency of 233.5kHz. L(0) =i L(3) =-3A, i L(1) =3A, and Figure 7 The minimum on-state loss ZVS constraint set in the original text is consistent.

[0160] visible, Figures 10a-10c This demonstrates that the ZVS control method for the four-switch Buck-Boost converter proposed in this embodiment can simultaneously achieve constant voltage closed-loop control in each mode and ZVS switching of each switch, while ensuring that each mode meets the set minimum on-state loss ZVS constraint condition.

[0161] When the output power is 100W, using the control method of this embodiment, the steady-state waveforms of the converter in each operating mode are as follows: Figures 11a-11c As shown; Figure 11a This is the closed-loop steady-state waveform in Boost mode with an input voltage of 75V and a switching frequency of 488.8kHz, while maintaining i L(0) =i L(3) =-3A, i L(2) =3A, and Figure 6 The minimum on-state loss ZVS constraint set in the original text is consistent; Figure 11b The closed-loop steady-state waveform is shown in Buck-Boost operating mode with an input voltage of 100V and a switching frequency of 625.8kHz, still maintaining a value close to i. L(0) =i L(3) =-3A, i L(1) ≥3A, i L(2) The minimum on-state loss ZVS constraint for ≥3A is consistent with that of the Buck-Boost operating mode. Figure 11c This is the closed-loop steady-state waveform in Buck operating mode with an input voltage of 125V and a switching frequency of 684.9kHz, still maintaining close to i L(0) =i L(3) =-3A, i L(1) =3A, and Figure 7 The minimum on-state loss ZVS constraint set in the original text is consistent;

[0162] Figures 11a-11c It has been demonstrated that, even at a power of 100W, the ZVS control method for the four-switch Buck-Boost converter proposed in this embodiment still ensures that each mode satisfies the minimum on-state loss ZVS constraint. (Summary) Figures 10a-11c Therefore, the ZVS control method of the four-switch Buck-Boost converter in this embodiment is effective over the entire wide input voltage and power range of the converter.

[0163] When the power is 500W and 100W respectively, using the control method of this embodiment, the transient switching experimental waveforms of the converter between each operating mode are as follows: Figures 12a-12d As shown; Figure 12aWith a power rating of 500W, the input voltage increased from 85V to 115V. The converter switched from Boost mode to Buck-Boost and Buck mode. During the mode switching process, the output voltage remained stable at 100V without distortion. Figure 12b When the power is reduced to 100W, the input voltage still increases from 85V to 115V. The converter switches from Boost mode to Buck-Boost and Buck mode. During the mode switching process, the output voltage remains stable at 100V without distortion. Figure 12c At medium power of 500W, the input voltage drops from 115V to 85V. The converter switches from Buck mode to Buck-Boost and Boost modes. During the mode switching process, the output voltage remains stable at 100V without distortion. Figure 12d When the power is reduced to 100W, the input voltage still drops from 115V to 85V. The converter switches from Buck mode to Buck-Boost and Boost modes, and the output voltage remains stable at 100V without distortion during the mode switching process. Figures 12a-12d This demonstrates that the ZVS control method of the four-switch Buck-Boost converter in this embodiment can effectively ensure the smooth and continuous voltage gain during mode switching, thereby preventing voltage distortion caused by the switching of the converter's operating mode.

[0164] Using the control method of this embodiment, the experimental waveforms of the converter in each operating mode during load switching are as follows: Figures 13a-13c As shown. Among them. Figure 13a This is the waveform of the output power switching from 500W to 100W when the input voltage is 80V in Boost mode. It can be seen that the overshoot of the output voltage is 7V. The control method in this embodiment can adjust the output voltage to stabilize at 100V again within 12ms. Figure 13b This is the waveform of the output power switching from 500W to 100W when the input voltage is 100V in Buck-Boost mode. It can be seen that the overshoot of the output voltage is 6V. The control method in this embodiment can adjust the output voltage to stabilize at 100V again within 20ms. Figure 13c This is the waveform of the output power switching from 500W to 100W when the input voltage is 120V in Buck mode. It can be seen that the overshoot of the output voltage is 8V. The control method in this embodiment can adjust the output voltage to stabilize at 100V again within 28ms. Figures 13a-13c This demonstrates that the control method of this embodiment is robust to changes in converter load parameters.

[0165] Using the control method of this embodiment, the efficiency curves of the converter over a wide input voltage range and at different power levels are as follows. Figure 14 As shown; when the converter is operating in Buck-Boost mode (92V≤U in≤108V, U in When the input voltage is close to the output voltage, the effective value of the inductor current is minimized, resulting in minimal conduction losses and the highest efficiency of the converter, approaching 98.5%. When the converter operates in Boost and Buck modes, the further the input voltage is from the output voltage, the greater the effective value of the inductor current and the higher the conduction losses, leading to lower converter efficiency.

[0166] An embodiment of a ZVS control system for a four-switch Buck-Boost converter

[0167] This embodiment provides a technical solution for a ZVS control system for a four-switch Buck-Boost converter. The control system includes a processor that executes program instructions to implement the ZVS control method for the four-switch Buck-Boost converter as described in the above embodiment.

[0168] Since the specific working mode and working principle of the control system in this embodiment have been described in detail in the above embodiment of the ZVS control method for the four-switch Buck-Boost converter, they will not be repeated here.

[0169] This invention has the following characteristics:

[0170] 1) By designing the first, second, third and fourth time nodes, a switching cycle is divided into three segments for ZVS control, eliminating the circulating current freewheeling link in the existing quadrilateral inductor current control, significantly reducing the effective value of the inductor current, and improving the power transmission efficiency of the converter.

[0171] 2) By independently analyzing the characteristics of each working mode of the converter, setting targeted constraint control conditions and corresponding control variables, and simplifying the calculation process, online real-time constant voltage closed-loop and minimum conduction loss ZVS control of each working mode are realized simultaneously. This effectively reduces the conduction loss of the converter, and does not require the use of multidimensional lookup tables and linear interpolation methods in the control process. The overall control is simple and easy to implement.

[0172] 3) When the converter switches between operating modes, a corresponding jump value is added to the output of the PI regulator in the ZVS constant voltage closed-loop control corresponding to the converter. This ensures that when the converter switches modes, the output of the PI regulator can jump simultaneously with the jump of the calculation formula of the control quantity corresponding to the constraint control condition, and ensures that the voltage gain of the converter remains unchanged before and after the jump, so that the output voltage is stable before and after the jump, thereby enabling the converter to achieve smooth mode switching and avoiding voltage distortion caused by mode switching.

[0173] It should be understood that the above-described specific embodiments of the present invention are merely illustrative or explanatory of the principles of the present invention, and do not constitute a limitation thereof.

Claims

1. A ZVS control method for a four-switch Buck-Boost converter, the four-switch Buck-Boost converter comprising first, second, third, and fourth switches and an inductor with its two ends respectively connected between the first and third switches and between the second and fourth switches, characterized in that, Within each switching cycle of the four-switch Buck-Boost converter, three time periods are set, consisting of the first, second, third, and fourth time nodes; Based on the minimum conduction loss (ZVS) constraint condition corresponding to different operating modes of the four-switch Buck-Boost converter, the values ​​of the corresponding control variables are determined. By adjusting the control variables, the current waveform of the inductor is controlled accordingly in different time periods. The control variables include the switching frequency corresponding to the switching cycle and the duty cycle of the trigger pulses of the first and second switches in each switching cycle. Among them, the first and fourth time nodes are the start and end times of the switching cycle, respectively; the second and third time nodes are the switching times of the first and second switching transistors, respectively. The minimum on-state loss ZVS constraint for Boost operating mode is: ； The ZVS constraint for minimum conduction loss in Buck operating mode is: ； Among them, i L(0) i L(1) i L(2) and i L(3) These are the inductor currents at the first, second, third, and fourth time nodes, respectively; I0 is the minimum current required to charge and discharge the output capacitors of the two switching transistors in the half-bridge of a four-switch Buck-Boost converter. Based on the ZVS constraint for minimum on-state loss corresponding to the Boost operating mode, determine the control variables: ； Based on the ZVS constraint for minimizing on-state losses corresponding to Buck's operating mode, determine the control variables: ； In the formula, D1 and D2 are the duty cycles of the trigger pulses of the first and second switches in each switching cycle, respectively; f is the switching frequency corresponding to the switching cycle; U1 and U2 are the input and output voltages of the four-switch Buck-Boost converter, respectively; I out is the output current of the four-switch Buck-Boost converter; L is the inductance value of the inductor whose two ends are respectively connected between the first and third switches and between the second and fourth switches.

2. The ZVS control method for a four-switch Buck-Boost converter according to claim 1, characterized in that, The switching frequency corresponding to the switching cycle and the duty cycle of the trigger pulses of the first and second switching transistors within each switching cycle are as follows: ； ； Where t0, t1, t2 and t3 are the first, second, third and fourth time nodes, respectively; D1 and D2 are the duty cycles of the trigger pulses of the first and second switching transistors in each switching cycle, respectively; and f is the switching frequency corresponding to the switching cycle.

3. The ZVS control method for a four-switch Buck-Boost converter according to claim 1, characterized in that, The minimum ZVS constraint for the Buck-Boost operating mode of the four-switch Buck-Boost converter is: ； ； In the formula, i L(0) and i L(3) These are the inductor currents at the first and fourth time nodes, respectively; I0 is the minimum current required to charge and discharge the output capacitors of the two switching transistors in the half-bridge of a four-switch Buck-Boost converter. This refers to the switching frequency corresponding to the switching cycle in Buck-Boost operating mode. This refers to the switching frequency of the Buck-mode converter with an input voltage of U' at the same output power, compared to the current Buck-Boost operating mode; where U1 is the input voltage of the four-switch Buck-Boost converter, U' is the minimum input voltage in Buck operating mode, and I... out This represents the output current of the four-switch Buck-Boost converter.

4. The ZVS control method for a four-switch Buck-Boost converter according to any one of claims 1-3, characterized in that, When switching between Boost mode and Buck-Boost mode, the output of the PI regulator in ZVS control in both Buck-Boost and Boost modes must meet the following conditions: ； in, This refers to the output of the PI regulator in ZVS control during Buck-Boost operation. U1' is the output of the PI regulator in ZVS control under Boost mode; U2 is the input voltage corresponding to the switching point between Boost mode and Buck-Boost mode; U2 is the output voltage of the four-switch Buck-Boost converter. This refers to the duty cycle of the trigger pulse of the first switch in each switching cycle of the four-switch Buck-Boost converter when it is operating in U1' mode. This is the duty cycle of the trigger pulse of the first switch in each switching cycle when the four-switch Buck-Boost converter is operating in U1' mode.

5. The ZVS control method for a four-switch Buck-Boost converter according to any one of claims 1-3, characterized in that, When switching between Buck operating mode and Buck-Boost operating mode, the output of the PI regulator in ZVS control in both Buck-Boost and Buck operating modes must meet the following conditions: ； in, This refers to the output of the PI regulator in ZVS control during Buck operation mode. U1” is the output of the PI regulator in ZVS control under Buck-Boost operating mode; U1” is the input voltage corresponding to the switching point between Buck operating mode and Buck-Boost operating mode; U2 is the output voltage of the four-switch Buck-Boost converter. This refers to the duty cycle of the trigger pulse of the first switch in each switching cycle of the Buck converter when the four-switch Buck-Boost converter is operating in U1”. This refers to the duty cycle of the trigger pulse of the first switch in each switching cycle when the four-switch Buck-Boost converter is operating in U1”.

6. A ZVS control system for a four-switch Buck-Boost converter, characterized in that, Includes a processor for executing program instructions to implement a ZVS control method for a four-switch Buck-Boost converter as follows: The four-switch Buck-Boost converter includes a first, second, third, and fourth switch transistor and an inductor with its two ends connected between the first and third switch transistors and between the second and fourth switch transistors, respectively. In each switching cycle of the four-switch Buck-Boost converter, three time periods consisting of the first, second, third, and fourth time nodes are set. Based on the minimum conduction loss (ZVS) constraint condition corresponding to different operating modes of the four-switch Buck-Boost converter, the values ​​of the corresponding control variables are determined. By adjusting the control variables, the current waveform of the inductor is controlled accordingly in different time periods. The control variables include the switching frequency corresponding to the switching cycle and the duty cycle of the trigger pulses of the first and second switches in each switching cycle. Among them, the first and fourth time nodes are the start and end times of the switching cycle, respectively; the second and third time nodes are the switching times of the first and second switching transistors, respectively. The minimum on-state loss ZVS constraint for Boost operating mode is: ； The ZVS constraint for minimum conduction loss in Buck operating mode is: ； Among them, i L(0) i L(1) i L(2) and i L(3) These are the inductor currents at the first, second, third, and fourth time nodes, respectively; I0 is the minimum current required to charge and discharge the output capacitors of the two switching transistors in the half-bridge of a four-switch Buck-Boost converter. Based on the ZVS constraint for minimum on-state loss corresponding to the Boost operating mode, determine the control variables: ； Based on the ZVS constraint for minimizing on-state losses corresponding to Buck's operating mode, determine the control variables: ； In the formula, D1 and D2 are the duty cycles of the trigger pulses of the first and second switches in each switching cycle, respectively; f is the switching frequency corresponding to the switching cycle; U1 and U2 are the input and output voltages of the four-switch Buck-Boost converter, respectively; I out is the output current of the four-switch Buck-Boost converter; L is the inductance value of the inductor whose two ends are respectively connected between the first and third switches and between the second and fourth switches.

7. The ZVS control system for the four-switch Buck-Boost converter according to claim 6, characterized in that, The switching frequency corresponding to the switching cycle and the duty cycle of the trigger pulses of the first and second switching transistors within each switching cycle are as follows: ； ； Where t0, t1, t2 and t3 are the first, second, third and fourth time nodes, respectively; D1 and D2 are the duty cycles of the trigger pulses of the first and second switching transistors in each switching cycle, respectively; and f is the switching frequency corresponding to the switching cycle.

8. The ZVS control system for the four-switch Buck-Boost converter according to claim 6, characterized in that, The minimum ZVS constraint for the Buck-Boost operating mode of the four-switch Buck-Boost converter is: ； ； In the formula, i L(0) and i L(3) These are the inductor currents at the first and fourth time nodes, respectively; I0 is the minimum current required to charge and discharge the output capacitors of the two switching transistors in the half-bridge of a four-switch Buck-Boost converter. This refers to the switching frequency corresponding to the switching cycle in Buck-Boost operating mode. This refers to the switching frequency of the Buck-mode converter with an input voltage of U' at the same output power, compared to the current Buck-Boost operating mode; where U1 is the input voltage of the four-switch Buck-Boost converter, U' is the minimum input voltage in Buck operating mode, and I... out This represents the output current of the four-switch Buck-Boost converter.

9. The ZVS control system for a four-switch Buck-Boost converter according to any one of claims 6-8, characterized in that, When switching between Boost mode and Buck-Boost mode, the output of the PI regulator in ZVS control in both Buck-Boost and Boost modes must meet the following conditions: ； in, This refers to the output of the PI regulator in ZVS control during Buck-Boost operation. U1' is the output of the PI regulator in ZVS control under Boost mode; U2 is the input voltage corresponding to the switching point between Boost mode and Buck-Boost mode; U2 is the output voltage of the four-switch Buck-Boost converter. This refers to the duty cycle of the trigger pulse of the first switch in each switching cycle of the four-switch Buck-Boost converter when it is operating in U1' mode. This is the duty cycle of the trigger pulse of the first switch in each switching cycle when the four-switch Buck-Boost converter is operating in U1' mode.

10. The ZVS control system for a four-switch Buck-Boost converter according to any one of claims 6-8, characterized in that, When switching between Buck operating mode and Buck-Boost operating mode, the output of the PI regulator in ZVS control in both Buck-Boost and Buck operating modes must meet the following conditions: ； in, This refers to the output of the PI regulator in ZVS control during Buck operation mode. U1” is the output of the PI regulator in ZVS control under Buck-Boost operating mode; U1” is the input voltage corresponding to the switching point between Buck operating mode and Buck-Boost operating mode; U2 is the output voltage of the four-switch Buck-Boost converter. This refers to the duty cycle of the trigger pulse of the first switch in each switching cycle of the Buck converter when the four-switch Buck-Boost converter is operating in U1”. This refers to the duty cycle of the trigger pulse of the first switch in each switching cycle when the four-switch Buck-Boost converter is operating in U1”.

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