High-frequency soft switching control method and system of four-switch Buck-Boost converter

Abstract

The invention provides a high-frequency soft switching control method and system for a four-switch Buck-Boost converter, and the method comprises the following steps: collecting an input voltage Vin, an output voltage Vo and an output current Io of a topological circuit of the four-switch Buck-Boost converter, and respectively representing the input voltage Vin, the output voltage Vo and the output current Io as a feedforward input voltage Vinffw, a feedback output voltage Vofdb and a feedback output current Iofdb; on the basis of a linear interpolation table look-up method, switching time parameters T1 and T2 are obtained through calculation; calculating a switching time parameter T3 through a PI regulator; and after the switching time parameters T1, T2 and T3 are added with dead time Tdead, PWM waveform digital signals of four switching tubes Q1, Q2, Q3 and Q4 in a topological circuit of the four-switch Buck-Boost converter are synthesized, and closed-loop control is completed. According to the scheme, inductive current sampling is not needed, the circuit design complexity is reduced, a linear interpolation look-up table method is adopted when T1 and T2 are calculated, the calculation data size is reduced, the calculation time is short, high-frequency control can be achieved, and the control method for achieving high-frequency soft switching is simple.

Description

Technical Field

[0001] The present invention relates to the technical field of converter control, and particularly to a high-frequency soft-switching control method and system for a four-switch Buck-Boost converter. Background Art

[0002] DC / DC converter technology is widely used in fields such as aerospace, national defense, industry, and electric vehicles. Among them, on-vehicle DC / DC converters are an important part of the power system of electric vehicles. At present, electric vehicles are gradually moving towards an 800V high-voltage platform. As a circuit topology that supports a wide voltage range and has both step-up and step-down functions, the four-switch Buck-Boost (FSBB) is more suitable for the front stage of the 800V platform for power conversion. On-vehicle DC / DC converters have relatively strict requirements for volume, power, and efficiency, and on-vehicle DC / DC converter technology is also developing towards high frequency, high power density, and high efficiency.

[0003] The current mainstream control methods for the FSBB topology are multi-modal modulation and inductor current quadrilateral modulation. Among them, multi-modal modulation is hard-switching control, which has large losses in high-frequency switching power supplies, and the control logic is complex. The calculation requires high chip performance and cannot meet high-frequency operation, making it difficult to meet the requirements of the electric vehicle industry. For inductor current quadrilateral modulation, for example, the patent with the patent number CN118984029A discloses a control method for realizing quadrilateral current mode and zero-voltage soft switching, which requires sampling the inductor current. Sampling the inductor current will increase some losses and reduce the efficiency. At the same time, the inductor current is not accurate during high-frequency sampling, which cannot ensure accurate control of the switching tubes and increases the uncertainty of the system. Summary of the Invention

[0004] Based on the problems existing in the above-mentioned prior art, the present invention aims to solve the technical problems that when using multi-modal modulation and inductor current quadrilateral modulation to control the FSBB topology in the prior art, the control strategy is complex, the calculation time is long, the loss is large, resulting in low efficiency, and the inductor current sampling is inaccurate during high-frequency operation, unable to meet high-frequency operation.

[0005] The present invention provides a high-frequency soft-switching control method for a four-switch Buck-Boost converter, which includes the following steps:

[0006] Collect the input voltage V in of the topology circuit of the four-switch Buck-Boost converter, o the output voltage V o and the output current I in_ffw , and respectively represent them as the feed-forward input voltage V o_fdband the feedback output current I o_fdb ;

[0007] Calculate the switching time parameters T 1 and T 2 , including:

[0008] According to the conditions of achieving soft switching and minimizing the effective value of inductor current, construct the calculation formulas for the switching time parameters T 1 , T 2 . The independent variables in the formula are the feed-forward input voltage V in_ffw and the feedback output current I o_fdb ;

[0009] Take multiple values of the feed-forward input voltage V in_ffw and the feedback output current I o_fdb respectively, and substitute them into the calculation formulas of T 1 , T 2 to obtain the corresponding T 1 , T 2 values, so as to create a two-dimensional linear interpolation lookup table for T 1 and a two-dimensional linear interpolation lookup table for T 2 ;

[0010] According to the collected feed-forward input voltage V in_ffw and the feedback output current I o_fdb , respectively look up the switching time parameters T 1 and T 2 in the two-dimensional linear interpolation lookup table for T 1 and the two-dimensional linear interpolation lookup table for T 2 ;

[0011] Calculate the switching time parameter T 3 through the PI regulator;

[0012] Add the dead time T 1 , T 2 , T 3 to the switching time parameters T dead , and synthesize the PWM waveform digital signals of the four switching tubes Q 1 , Q 2 , Q 3 , Q 4 in the topology circuit of the four-switch Buck-Boost converter to complete the closed-loop control.

[0013] According to an embodiment of the present invention, the calculation formulas for the switching time parameters T 1 , T 2 are:

[0014]

[0015] Wherein, T s is the switching period, C oss is the capacitance value of the parasitic capacitances of the four switching transistors, L is the inductance value, V o_ref is the output voltage reference value, which can be obtained by looking up in the one-dimensional linear interpolation lookup table of V o_ref . The independent variable of the one-dimensional linear interpolation lookup table of V o_ref is the feed-forward input voltage V in_ffw , and the corresponding relationship between V in_ffw and V o_ref is related to the functional scenario of the four-switch Buck-Boost converter; I rate is the rated output current value, λ 1 is the calibration proportionality coefficient of T 1 , σ 1 is the error correction parameter of T 1 , λ 2 is the calibration proportionality coefficient of T 2 , σ 2 is the error correction parameter of T 2 .

[0016] According to an embodiment of the present invention, the values taken by the feed-forward input voltage V in_ffw and the feedback output current I o_fdb are respectively close to the measured values of the input voltage V in and the output current I o in the topology circuit of the four-switch Buck-Boost converter.

[0017] According to an embodiment of the present invention, after obtaining the switching time parameter T 1 from the two-dimensional linear interpolation lookup table of the switching time parameter T 2 and the switching time parameter T 1 from the two-dimensional linear interpolation lookup table of the switching time parameter T 2 , they need to be respectively filtered by an IIR filter.

[0018] According to an embodiment of the present invention, the calculation formula of the switching time parameter T 3 is:

[0019] E(k) = V o_fdb -V o_ref ;

[0020]

[0021] Wherein, E(k) is the voltage error value, K p is the proportional regulation coefficient of the PI regulator, K i is the integral regulation coefficient of the PI regulator, K p and K iThe value of

[0022] The present invention also provides a high-frequency soft-switching control system for a four-switch Buck-Boost converter to implement the high-frequency soft-switching control method of the four-switch Buck-Boost converter, which includes:

[0023] An acquisition module that acquires the input voltage V in of the topology circuit of the four-switch Buck-Boost converter, o the output voltage V o and the output current I in_ffw , and respectively represents them as the feed-forward input voltage V o_fdb , the feedback output voltage V o_fdb and the feedback output current I

[0024] An interpolation table generation module that, according to the conditions for realizing soft switching and minimizing the effective value of the inductor current, derives the calculation formulas for the switching time parameters T 1 , T 2 , and thus makes a two-dimensional linear interpolation lookup table for T 1 and a two-dimensional linear interpolation lookup table for T 2 ;

[0025] A lookup table module that, according to the feed-forward input voltage V in_ffw and the feedback output current I o_fdb , respectively looks up the switching time parameters T 1 and T 2 in the two-dimensional linear interpolation lookup table for T 1 and the two-dimensional linear interpolation lookup table for T 2 ;

[0026] A PI regulator that compares the feedback output voltage V o_fdb with the output voltage reference value V o_ref and calculates the switching time parameter T 3 ;

[0027] A PWM waveform synthesis module that adds the dead time T 1 , T 2 , T 3 to the switching time parameters T dead , and synthesizes the PWM waveform digital signals of the four switching tubes Q 1 , Q 2 , Q 3 , Q 4 in the topology circuit of the four-switch Buck-Boost converter to complete the closed-loop control.

[0028] According to an embodiment of the present invention, the high-frequency soft-switching control system of the four-switch Buck-Boost converter further includes an IIR filter, which is used to obtain the switching time parameters T 1 and T 2 from the look-up table module, and then perform filtering processing on T 1 and T 2 respectively.

[0029] The beneficial effects of the present invention are as follows:

[0030] The high-frequency soft-switching control method and system for a four-switch Buck-Boost converter provided by the present invention do not require sampling of the inductor current, reducing the complexity of circuit design, reducing costs, and improving efficiency; when calculating T 1 and T 2 , the linear interpolation look-up table method is used, which reduces the amount of calculation data while ensuring control accuracy, does not occupy a large amount of chip storage resources, has strong adaptability to digital control chips, and the control method for realizing high-frequency soft switching is relatively simple, with stable control, fast calculation, decoupling the calculation of each stage parameter, minimizing the jitter risk between the critical points of each working condition, improving the circuit stability, and increasing the algorithm integration and the practicability of the control method. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0032] Figure 1 is a schematic flowchart of a high-frequency soft-switching control method for a four-switch Buck-Boost converter provided by an embodiment of the present invention;

[0033] Figure 2 is a topological circuit diagram of a four-switch Buck-Boost converter in an embodiment of the present invention;

[0034] Figure 3 is a waveform diagram of the inductor current of a four-switch Buck-Boost converter in an embodiment of the present invention;

[0035] Figure 4 is a high-frequency soft-switching control block diagram of a four-switch Buck-Boost converter in an embodiment of the present invention;

[0036] Figure 5 is a schematic diagram of the PWM waveforms of the four synthesized switching tubes in an embodiment of the present invention;

[0037] Figure 6 It is a schematic structural diagram of a high-frequency soft-switching control system for a four-switch Buck-Boost converter provided by an embodiment of the present invention. Specific implementation manners

[0038] The following descriptions of the embodiments are made with reference to the attached drawings, which are used to illustrate specific embodiments in which the present invention can be implemented.

[0039] The present invention provides a high-frequency soft-switching control method for a four-switch Buck-Boost converter, and its process is as Figure 1 shown, including the following steps:

[0040] S1: According to the conditions that satisfy realizing soft switching and minimizing the effective value of the inductor current, construct the calculation formulas of the switching time parameters T 1 and T 2 , and the independent variables in the formulas are the feedforward input voltage V in_ffw and the feedback output current I o_fdb ;

[0041] S2: Take multiple values of the feedforward input voltage V in_ffw and the feedback output current I o_fdb respectively, and substitute them into the calculation formulas of T 1 and T 2 respectively to obtain the corresponding T 1 and T 2 values, so as to make a two-dimensional linear interpolation lookup table of T 1 and a two-dimensional linear interpolation lookup table of T 2 ; among them, the breakpoints of the two-dimensional linear interpolation lookup table of T 1 and the two-dimensional linear interpolation lookup table of T 2 are both the feedforward input voltage V in_ffw and the feedback output current I o_fdb ;

[0042] S3: Collect the input voltage V in , output voltage V o and output current I o of the topological circuit of the four-switch Buck-Boost converter, and represent them as the feedforward input voltage V in_ffw , feedback output voltage V o_fdb and feedback output current I o_fdb respectively;

[0043] S4: According to the collected feedforward input voltage V in_ffw and feedback output current I o_fdb , in the two-dimensional linear interpolation lookup table of T 1 and the two-dimensional linear interpolation lookup table of T 2The switching time parameters T are respectively obtained from the two-dimensional linear interpolation lookup table 1 and T 2 ;

[0044] S5: Calculate the switching time parameter T 3 ;

[0045] S6: Add the dead time T 1 、T 2 、T 3 to the switching time parameters T dead , and synthesize the PWM waveform digital signals of the four switching tubes Q 1 、Q 2 、Q 3 、Q 4 in the topology circuit of the four-switch Buck-Boost converter to complete the closed-loop control.

[0046] The following combines Figures 2 - 5 to describe in detail a high-frequency soft-switching control method for a four-switch Buck-Boost converter provided by the present invention.

[0047] As Figure 2 shown is the topology circuit diagram of the four-switch Buck-Boost converter in the embodiment of the present invention. Among them, the switching tube Q 1 and the switching tube Q 2 conduct complementarily, and the switching tube Q 3 and the switching tube Q 4 conduct complementarily, and there is a phase shift between the two bridge arms. The input voltage V in , output voltage V o and output current I o of the acquisition circuit are respectively represented as the feed-forward input voltage V in_ffw , feedback output voltage V o_fdb and feedback output current I o_fdb . Compared with the existing technology where the inductor current collected is alternating current, the output current I o collected in this embodiment is direct current, which has lower requirements for the circuit, thereby reducing the circuit design complexity.

[0048] Derive the calculation formulas of T 1 and T 2

[0049] As Figure 3 shown is the inductor current waveform diagram in the embodiment of the present invention. By controlling the on / off of the four switching tubes to control the inductor current waveform, the switching time parameters T 1 、T 2 、T 3 、T 4 corresponding to the four switching tubes are as follows:

[0050]

[0051] Wherein, Q 1_off 、Q 2_off 、Q 3_off 、Q 4_off are respectively the time-domain coordinates of the turn-off moments of the switching transistors Q 1 、Q 2 、Q 3 、Q 4 .

[0052] Wherein, T 1 is the moment when the switching transistor Q 1 and the switching transistor Q 4 are conducting simultaneously. At this time, energy is stored in the inductor and the inductor current rises. T 2 is the moment when the switching transistor Q 1 and the switching transistor Q 3 are conducting simultaneously. At this time, energy transfer occurs between the input side and the output side. The slope change in the T 2 stage is related to the transient values of the input voltage and the output voltage. Figure 3 As shown, it is the state where the input voltage V in is greater than the output voltage V o . T 3 is the moment when the switching transistor Q 2 and the switching transistor Q 4 are conducting simultaneously. At this time, the inductor discharges and the inductor current drops; T 4 is regarded as the regulation margin, and the corresponding relationship is:

[0053] T s = T 1 + T 2 + T 3 + T 4 (2)

[0054] Wherein, T s is the switching period. The constraint conditions for the control method of the embodiment of the present invention to adjust T 1 、T 2 、T 3 are:

[0055] T 1 + T 2 + T 3 ≤ T s (3)

[0056] Figure 3 The judgment condition for realizing soft switching in

[0057]

[0058] In the formula, I 0 ,I 1 ,I 2 ,I 3 is the inductor current value at each inflection point of the inductor current waveform of the four-switch Buck-Boost converter, I ZVS_Vin is the input voltage V in Zero voltage turn-on current threshold, I ZVS_Vo is the output voltage V o Zero voltage turn-on current threshold, calculated as:

[0059]

[0060] In the formula, C oss is the parasitic capacitance of the four switch tubes in the four-switch Buck-Boost converter, T dead is the dead time, and L is the inductance of the inductor.

[0061] Ignoring the dead zone, the following derivation can be obtained under steady-state conditions: 0 ,I 1 ,I 2 ,I 3 With T 1 , T 2 , T 3 The calculation formula is:

[0062]

[0063] To maximize efficiency, in addition to meeting the soft switching conditions, it is also necessary to minimize the effective value of the inductor current to reduce circuit losses, that is, to control the inflection points of the inductor current at I ZVS_Vin and I ZVS_Vo At this time, the four-switch Buck-Boost converter operates in FCCM mode in the full power range, achieving soft switching while ensuring the minimum effective value of the inductor current. Based on the conditions of achieving soft switching and minimizing the effective value of the inductor current, T is derived under rated operating conditions. 1 The calculation formula is:

[0064] Under rated conditions I ZVS_Vin Less than I ZVS_Vo To ensure the soft switching of all tubes, according to formula (4), let:

[0065] I 0 =-I ZVS_Vo =-I 1 (7)

[0066] Combining equations (4), (5) and (6) with equation (7), we can obtain:

[0067]

[0068] As Figure 2 , by introducing the load percentage variable and for voltage stabilization control during the operation of the converter, V o can be regarded as a constant, that is, the load rate can be equivalently expressed as:

[0069]

[0070] In the formula, η is the load rate, I o is the output current, and I rate is the rated output current value.

[0071] For convenient digital control, the time length quantity is normalized to convert it into a duty cycle signal, and at the same time, the calibration proportionality coefficient λ 1 is introduced:

[0072]

[0073] In the formula, V o_rate is the output voltage under rated conditions, and V in_rate is the input voltage under rated conditions.

[0074] From formulas (8) and (9), the full-power calculation formula is obtained:

[0075]

[0076] In the formula, T 1 / T s is the numerical value of the duty cycle signal of T 1 . In actual control, there are partial error ranges for physical quantities, so σ 1 is introduced. σ 1 is the error correction parameter of T 1 , and its theoretical value is 0.

[0077] As Figure 2 , in the FSBB topology, Q 1 , Q 2 form the Buck leg, and Q 3 , Q 4 form the Boost leg. The FSBB can be regarded as the cascade of Buck and Boost. From formula (1) and ignoring the dead zone, we get

[0078]

[0079] In the formula, D buck is the duty cycle signal of the Buck leg, D boost is the duty cycle signal of the Boost leg. The voltage gain relationship of the cascade of Buck and Boost is:

[0080]

[0081] Combining equations (12) and (13) gives the FSBB voltage gain formula:

[0082]

[0083] As Figure 3 in the example, when V in is greater than V o , the inductor current shows an upward trend. At this time, I 2 is greater than I 2 . According to equations (4) and (5), it can be known that the relationship between I 1 and I 2 is related to V 1 and V in . That is, in the T o stage, if V 2 is greater than V in , the slope of the inductor current is positive at this time, and I o is always greater than I 2 . The limiting condition for realizing soft switching is that I 1 is greater than I 1 ; similarly, when V ZVS_Vo is less than V in , the limiting condition for realizing soft switching is that I o is greater than I 2 . The formula for the relationship between the soft-switching current threshold and the input and output voltages in the T ZVS_Vin stage can be obtained: 2 In the formula, I

[0084]

[0085] is the minimum current threshold for realizing soft switching. ZVS

[0086] Figure 3 As can be seen, the T 2 stage is a process of energy transfer between the input side and the output side. The duration of T 2 is proportional to the transferred energy. Here, the maximum energy transfer is used as the boundary condition, that is, let T 4 be 0. From equations (2) and (3), we can get:

[0087] T 1 +T 2 +T 3 =T s (16)

[0088] Similar to T 1 , for convenient digital control, the time length is normalized and converted into a duty cycle signal, and λ 2 is introduced:

[0089] λ2 = 2T s (17)

[0090] According to Equation (6), the full power range calculation formula obtained is:

[0091]

[0092] In the formula, σ 2 is the error correction parameter of T 2 , and its theoretical value is 1.

[0093] For the accuracy of formula expression and the stability of circuit control, the output voltage V o in Equations (11) and (18) is replaced by the reference output voltage V o_ref , where V o_ref is the output voltage reference value, which can be obtained from the one-dimensional linear interpolation lookup table of V o_ref . As shown in Table 1, the independent variable of the one-dimensional linear interpolation lookup table of V o_ref is the feedforward input voltage V in_ffw , and the corresponding relationship between V in_ffw and V o_ref is related to the functional scenario of the four-switch Buck-Boost converter.

[0094] Table 1 One-dimensional linear interpolation lookup table of V o_ref

[0095]

[0096]

[0097] After making the table of V o_ref , one independent variable can be reduced when calculating T 1 and T 2 ; and the input voltage V in is replaced by the feedforward input voltage V in_ffw (V in_ffw is equal to V in ); the output current I o is replaced by the feedback output current I o_fdb (I o_fdb is equal to I o ); thus, we get:

[0098]

[0099] Table 2 gives the numerical values of the parameters in the topological circuit of the four-switch Buck-Boost converter in this embodiment, thereby determining the constants in Equation (19).

[0100] Table 2 Numerical values of each parameter in the topological circuit of the four-switch Buck-Boost converter

[0101] Parameter Name Value L 30 uH <![CDATA[C oss > 82 pF <![CDATA[T dead > 100 ns <![CDATA[T s > 25 us <![CDATA[I rate > 3.6A <![CDATA[V o_rate > 696V <![CDATA[V in_rate > 648V

[0102] Make T 1 and T 2 's linear interpolation lookup table

[0103] Let σ 1 = 0, σ 2 = 0.927, and substitute the multiple values of the feedforward input voltage V in_ffw and the feedback output current I o_fdb into the calculation formulas of T 1 and T 2 respectively, to obtain the corresponding T 1 and T 2 values, thus making the two-dimensional tables of T 1 and T 2 . The breakpoints (independent variables) of the table are V in_ffw and I o_fdb . In order to reduce the data volume of the table, when taking values of the feedforward input voltage V in_ffw and the feedback output current I o_fdb , the values taken by the feedforward input voltage V in_ffw are 70% - 140% of the rated input voltage in the topological circuit of the four-switch Buck-Boost converter, and the values taken by the feedback output current I o_fdb are 0 - 125% of the rated output current in the topological circuit of the four-switch Buck-Boost converter. The two-dimensional tables of T 1 and T 2 are shown in Table 3 and Table 4 as follows:

[0104] Table 3 Two-dimensional linear interpolation lookup table of T 1

[0105]

[0106] Table 4 Two-dimensional linear interpolation lookup table of T 2

[0107]

[0108]

[0109] It should be noted that Table 1, 3, and 4 only show partial data in the linear interpolation table. During actual work, the data can be appropriately expanded.

[0110] Look up the table to obtain the switching time parameters T 1 and T 2 ​​

[0111] As Figure 4 , the input V in_ffw and I o_fdb , due to the adoption of linear interpolation and through the reasonable distribution of data, precise control can be achieved under the condition of greatly reducing the table data. The IIR is a digital filter that filters the high-frequency current signal in the control process to increase the stability of the loop. After calculation by the two-dimensional linear interpolation look-up table method and IIR filtering, T 1 and T 2 are obtained.

[0112] Calculate the switching time parameter T 3

[0113] Continue to refer to Figure 4 , by adjusting T 3 to achieve the control of the output voltage. For the convenience of writing into the digital control chip, each link is discretized to obtain the formula:

[0114] E(k) = V o_fdb - V o_ref

[0115]

[0116] In the formula, V o_fdb is the feedback output voltage value (V o_fdb is equal to V o ); E(k) is the voltage error value, K p is the proportional regulation coefficient of the PI regulator, K i is the integral regulation coefficient of the PI regulator. The values of K p and K i will affect the dynamic performance of the circuit; after obtaining T 1 , T 2 , T 3 , add the dead zone to synthesize the PWM digital signals of the four switching tubes to complete the closed-loop control; among them, adjusting T 1 and T 2 can control the inductor current waveform, and adjusting T 3 can achieve the stabilization of the output voltage to minimize the effective value of the inductor current, thereby realizing soft switching.

[0117] Synthesize the switching time parameters T 1 , T 2 , T 3

[0118] As Figure 5 shown, the four switching tubes Q 1 , Q 2 , Q 3 , Q 4The PWM waveform diagram, combined with Equation (1), shows that T 1 , T 2 , T 3 and Q 1 , Q 2 , Q 3 , Q 4 correspondence of the PWM signals, Q 1 is the main switch of the Buck leg, Q 4 is the main switch of the Boost leg, Q 1 lags behind Q 4 , there is a phase difference.

[0119] The embodiment of the present invention also provides a high-frequency soft-switching control system for a four-switch Buck-Boost converter to implement the high-frequency soft-switching control method of the four-switch Buck-Boost converter. The structural schematic diagram of the high-frequency soft-switching control system of the four-switch Buck-Boost converter is as shown in Figure 6 . It includes an acquisition module, an interpolation table generation module, a look-up table module, a PI regulator, a PWM waveform synthesis module, and an IIR filter. Among them, the acquisition module acquires the input voltage V in , output voltage V o and output current I o of the topological circuit of the four-switch Buck-Boost converter, and respectively represents them as the feed-forward input voltage V in_ffw , feedback output voltage V o_fdb and feedback output current I o_fdb ; the interpolation table generation module is used to derive the calculation formulas of the switching time parameters T 1 , T 2 according to the conditions that meet soft-switching and the minimum effective value of the inductor current, so as to make a two-dimensional linear interpolation look-up table of T 1 and a two-dimensional linear interpolation look-up table of T 2 ; the look-up table module is used to look up the switching time parameters T in_ffw and feedback output current I o_fdb in the two-dimensional linear interpolation look-up table of T 1 and the two-dimensional linear interpolation look-up table of T 2 to obtain the switching time parameters T 1 and T 2 respectively; the PI regulator is used to compare the feedback output voltage V o_fdb with the output voltage reference value V o_ref and calculate the switching time parameter T 3 ; the PWM waveform synthesis module is used to add the dead time T 1 , T 2 , T 3 to the switching time parameters Tdead , the PWM waveform digital signals of the four switching transistors Q 1 , Q 2 , Q 3 , Q 4 in the topology circuit of the four-switch Buck-Boost converter are synthesized to complete the closed-loop control; the IIR filter is used to filter the switching time parameters T 1 and T 2 respectively after they are obtained by the look-up table module. 1 and T 2 are filtered respectively.

[0120] In summary, the high-frequency soft-switching control method for a four-switch Buck-Boost converter provided by the present invention does not require sampling of the inductor current, reduces the complexity of circuit design, reduces costs, and improves efficiency; when calculating T 1 , T 2 , the linear interpolation look-up table method is adopted, which reduces the amount of calculated data while ensuring the control accuracy, does not occupy a large amount of chip storage resources, has strong adaptability to digital control chips, and the control method for realizing high-frequency soft switching is relatively simple, the control is stable, the calculation is fast, decouples the calculation of each stage parameter, minimizes the jitter hidden danger between the critical points of each working condition, improves the circuit stability, and increases the algorithm integration and the practicability of the control method.

[0121] It should be noted that although the present invention is disclosed as above with specific embodiments, the above embodiments are not intended to limit the present invention. Those of ordinary skill in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention is subject to the scope defined by the claims.

Claims

1. A high-frequency soft-switching control method for a four-switch Buck-Boost converter, characterized in that: The following steps are involved: Collect the input voltage V of the four-switch Buck-Boost converter topology circuit in , output voltage V o and output current I o , and are respectively expressed as the feedforward input voltage V in_ffw , feedback output voltage V o_fdb and feedback output current I o_fdb ; Calculate the switching time parameters T1 and T2, including: According to the conditions of achieving soft switching and minimizing the effective value of the inductor current, the calculation formula of the switching time parameters T1 and T2 is constructed. The independent variable in the formula is the feedforward input voltage V in_ffw and feedback output current I o_fdb ; The feedforward input voltage V in_ffw and feedback output current I o_fdb Take values ​​multiple times and substitute them into the calculation formulas of T1 and T2 respectively to obtain the corresponding T1 and T2 values, thereby making a two-dimensional linear interpolation lookup table of T1 and a two-dimensional linear interpolation lookup table of T2; According to the collected feedforward input voltage V in_ffw and feedback output current I o_fdb , the switching time parameters T1 and T2 are respectively obtained in the two-dimensional linear interpolation lookup table of T1 and the two-dimensional linear interpolation lookup table of T2; The switching time parameter T3 is calculated by the PI regulator; Add the dead time T after the switch time parameters T1, T2, and T3 dead , synthesize the PWM waveform digital signals of the four switch tubes Q1, Q2, Q3, and Q4 in the topology circuit of the four-switch Buck-Boost converter to complete the closed-loop control.

2. The high-frequency soft-switching control method of a four-switch Buck-Boost converter according to claim 1, characterized in that: The calculation formula for the switching time parameters T1 and T2 is: Where, T s is the switching cycle, C oss is the capacitance of the parasitic capacitors of the four switching tubes, L is the inductance of the inductor, V o_ref is the output voltage reference value, which can be obtained by V o_ref The one-dimensional linear interpolation lookup table is checked, V o_ref The independent variable of the one-dimensional linear interpolation lookup table is the feedforward input voltage V in_ffw , V in_ffw and V o_ref The corresponding relationship is related to the functional scenario of the four-switch Buck-Boost converter; I rate is the rated output current value, λ1 is the calibration proportional coefficient of T1, σ1 is the error correction parameter of T1, λ2 is the calibration proportional coefficient of T2, σ2 is the error correction parameter of T2.

3. The high-frequency soft-switching control method of a four-switch Buck-Boost converter according to claim 1, characterized in that: The feedforward input voltage V in_ffw and feedback output current I o_fdb When the feedforward input voltage V in_ffw The value is 70% to 140% of the rated input voltage in the topology circuit of the four-switch Buck-Boost converter, and the feedback output current I o_fdb The value taken is 0 to 125% of the rated output current in the topology circuit of the four-switch Buck-Boost converter.

4. The high-frequency soft-switching control method of a four-switch Buck-Boost converter according to claim 1, characterized in that: After the switching time parameters T1 and T2 are respectively found in the two-dimensional linear interpolation lookup table of the switching time parameter T1 and the two-dimensional linear interpolation lookup table of the switching time parameter T2, they need to be filtered by IIR filters respectively.

5. The high-frequency soft-switching control method of a four-switch Buck-Boost converter according to claim 1, characterized in that: The calculation formula of the switching time parameter T3 is: E(k)=V o_fdb -V o_ref ; Where E(k) is the voltage error value, K p is the proportional adjustment coefficient of the PI regulator, K i K is the integral adjustment coefficient of the PI regulator. p and K i The value of will affect the dynamic performance of the circuit.

6. A high-frequency soft-switching control system for a four-switch Buck-Boost converter, used to implement the high-frequency soft-switching control method for a four-switch Buck-Boost converter according to any one of claims 1 to 5, characterized in that: include: The acquisition module collects the input voltage V of the topology circuit of the four-switch Buck-Boost converter in , output voltage V o and output current I o , and are respectively expressed as the feedforward input voltage V in_ffw , feedback output voltage V o_fdb and feedback output current I o_fdb ; An interpolation table generation module is used to derive the calculation formulas of the switching time parameters T1 and T2 according to the conditions of achieving soft switching and minimizing the effective value of the inductor current, thereby making a two-dimensional linear interpolation lookup table of T1 and a two-dimensional linear interpolation lookup table of T2; The table lookup module is used to calculate the feedforward input voltage V in_ffw and feedback output current I o_fdb The switching time parameters T1 and T2 are respectively obtained in the two-dimensional linear interpolation lookup table of T1 and the two-dimensional linear interpolation lookup table of T2; PI regulator is used to feedback the output voltage V o_fdb With the output voltage reference value V o_ref Make comparison and calculate the switching time parameter T3; PWM waveform synthesis module, used to add the dead time T after the switching time parameters T1, T2, T3 dead , synthesize the PWM waveform digital signals of the four switch tubes Q1, Q2, Q3, and Q4 in the topology circuit of the four-switch Buck-Boost converter to complete the closed-loop control.

7. The high frequency soft switching control system of the four-switch Buck-Boost converter according to claim 6, characterized in that: It also includes an IIR filter, and the IIR filter is used to filter T1 and T2 respectively after the table lookup module obtains the switching time parameters T1 and T2.

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