Regulation and control method and system of four-switch buck-boost converter

Abstract

The invention provides a regulation and control method and system for a four-switch buck-boost converter, and the method comprises the steps: constructing an average state-space equation of the converter based on a continuous conduction mode according to an input voltage and an output voltage; based on the average state space equation, adjusting the first duty ratio and the second duty ratio, switching the working mode of the converter and matching the corresponding transfer function; wherein the first duty ratio is the conduction duty ratio of the first switch, and the second duty ratio is the conduction duty ratio of the fourth switch; and based on the transfer function of each mode, the inductive current ripple and the root-mean-square current are minimized by adjusting the first duty ratio and the second duty ratio. According to the method, the inductive current ripples and the root-mean-square current are remarkably reduced, so that the efficiency of the converter is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of converters, and in particular to a control method and system for a four-switch buck-boost converter. Background Art

[0002] Four-switch buck-boost (FSBB) converters are widely used in applications requiring efficient voltage regulation over a wide input and output voltage range, such as photovoltaic (PV) systems. However, existing technologies face significant challenges, including limited efficiency, high current ripple, and difficulty in seamlessly transitioning between buck, boost, and buck-boost modes. These limitations often result in higher power consumption, lower reliability, and suboptimal performance, especially in applications with highly variable voltage levels. Conventional buck-boost converters typically employ single-sided modulation schemes, which are inefficient in minimizing current ripple and rms current, leading to higher power consumption and thermal issues. Integrated buck-boost converters and multi-switch designs, while more efficient, often increase complexity and cost, and reduce adaptability to dynamic conditions.

[0003] In this regard, the present invention proposes an advanced modulation control scheme for FSBB converter, which overcomes the shortcomings of the prior art. Summary of the Invention

[0004] To address the shortcomings of the existing technology, the present invention proposes a control method and system for a four-switch buck-boost converter, which supports a wide input and output voltage range and ensures seamless operation between buck, boost, and buck-boost modes. The method adopts dual-edge modulation (TEM) and dual-mode TEM to significantly reduce the inductor current ripple and RMS current, thereby improving the efficiency of the converter.

[0005] To achieve the above objectives, the present invention provides, in one aspect, a control method for a four-switch buck-boost converter. The converter includes a first circuit and a second circuit, wherein the first and second circuits are cascaded between an input terminal and an output terminal. The first circuit includes an input capacitor, a first switch, and a second switch, wherein the input capacitor is connected in parallel to the input terminal, the second switch is connected in parallel to the input capacitor, and the first switch is connected in series between the input capacitor and the second switch. The second circuit includes an output capacitor, a third switch, and a fourth switch, wherein the output capacitor is connected in parallel to the output terminal, the fourth switch is connected in parallel to the output capacitor, and the third switch is connected in series between the output capacitor and the fourth switch. An input inductor is connected in series between the first and second circuits, and a load resistor is also connected in parallel to the output terminal.

[0006] The method includes:

[0007] According to the input voltage and output voltage, the average state space equation of the converter is constructed based on the continuous conduction mode;

[0008] Based on the average state-space equation, adjusting a first duty cycle and a second duty cycle, switching the operating mode of the converter and matching the corresponding transfer function; wherein the first duty cycle is the on-duty cycle of the first switch, and the second duty cycle is the on-duty cycle of the fourth switch;

[0009] Based on the transfer functions of each mode, the first duty cycle and the second duty cycle are adjusted to minimize the inductor current ripple and the root mean square current; wherein:

[0010] In the buck mode, the first duty cycle is adjusted by bilateral modulation TEM to minimize the inductor current ripple and the RMS current, where:

[0011]

[0012] Among them, I L,avg is the average steady-state current, I L,avg =v o / R, T is the switching period, f sw is the switching frequency, T=1 / f sw ;Δi L,降压 is the inductor current ripple in buck mode, I L,RMS is the root mean square current; v in and v o are the input voltage of the input terminal and the output voltage of the output terminal, R is the load resistance, d1 and d2 represent the first duty cycle and the second duty cycle respectively;

[0013] In the boost mode, the second duty cycle is adjusted by bilateral TEM modulation to minimize the inductor current ripple and the RMS current, where:

[0014]

[0015] Among them, Δi L,升压 is the inductor current ripple in boost mode, I L,avg =v o / (R(1-d2)), d2 represents the second duty cycle;

[0016] In the buck-boost mode, the first duty cycle and the second duty cycle are synchronously adjusted through dual-mode TEM modulation to minimize the inductor current ripple and the RMS current, wherein:

[0017]

[0018] Among them, Δi L,降压-升压is the inductor current ripple in buck-boost mode, I L,avg =v o d1 / (R(1-d2)).

[0019] In one embodiment of the present invention, based on the continuous conduction mode, the average state space equation of the converter is constructed as:

[0020]

[0021] Among them, v in and v o are the input voltage at the input end and the output voltage at the output end, i L is the current of the input inductor L, C is the output capacitor, R is the load resistance, d1 and d2 represent the first duty cycle and the second duty cycle respectively.

[0022] In one embodiment of the present invention, in the buck mode, the input voltage is greater than the output voltage, the second duty cycle is zero, the fourth switch is turned off, and the third switch is turned on;

[0023] The transfer function is:

[0024]

[0025] Where s is the complex frequency variable of Laplace transform;

[0026] By adjusting the first duty cycle, the complementary conduction of the first switch and the second switch is controlled to perform step-down regulation so that the output voltage v o (s) satisfies v o (s)=v in d1(s).

[0027] In one embodiment of the present invention, in boost mode, the input voltage is less than the output voltage, the first duty cycle is one, the first switch is turned on, and the second switch is turned off;

[0028] The transfer function is:

[0029]

[0030] By adjusting the second duty cycle, the complementary conduction of the third switch and the fourth switch is controlled to perform boost regulation so that the output voltage v o (s) satisfies v o (s)=v in / (1-d2).

[0031] In one embodiment of the present invention, in the buck-boost mode, the input voltage and the output voltage have no fixed magnitude relationship, and both the first duty cycle and the second duty cycle are non-zero;

[0032] The transfer function is:

[0033]

[0034] By adjusting the first duty cycle and the second duty cycle, the on and off states of the first switch, the second switch, the third switch, and the fourth switch are controlled so that the output voltage v o (s) satisfies v o (s)=v in d / (1-d), d1=d2=d.

[0035] In one embodiment of the present invention, the method further comprises:

[0036] Based on the transfer function of each mode, the minimum values ​​of the input inductor, output capacitor, and input capacitor are calculated.

[0037] In one embodiment of the present invention, in the buck mode, the input inductor is:

[0038]

[0039] In boost mode, the input inductor is:

[0040]

[0041] Among them, K ind is the current ripple factor, I out is the output current at the output terminal, is the maximum input voltage, is the minimum input voltage, L min is the minimum value of input inductance;

[0042] In buck mode, the output capacitance is:

[0043]

[0044] or,

[0045]

[0046] In boost mode, the output capacitance is:

[0047]

[0048] in, is the output voltage ripple, ΔV ot is the voltage regulation rate, is the minimum output voltage.

[0049] In buck mode, the input capacitance is:

[0050]

[0051] In boost mode, the input capacitance is:

[0052]

[0053] Among them, I om is the peak output current, is the peak-to-peak value of the input voltage.

[0054] Another aspect of the present invention provides a modulation control system for a four-switch buck-boost converter, comprising:

[0055] A four-switch buck-boost converter includes a first circuit and a second circuit, the first and second circuits being cascaded between an input terminal and an output terminal. The first circuit includes an input capacitor, a first switch, and a second switch. The input capacitor is connected in parallel to the input terminal, the second switch is connected in parallel to the input capacitor, and the first switch is connected in series between the input capacitor and the second switch. The second circuit includes an output capacitor, a third switch, and a fourth switch. The output capacitor is connected in parallel to the output terminal, the fourth switch is connected in parallel to the output capacitor, and the third switch is connected in series between the output capacitor and the fourth switch. An input inductor is connected in series between the first and second circuits, and a load resistor is also connected in parallel to the output terminal.

[0056] a PWM controller configured to control a first duty cycle and a second duty cycle, control the on and off states of the first switch, the second switch, the third switch, and the fourth switch, switch an operating mode, and match a corresponding transfer function; and minimize the inductor current ripple and the root mean square current by adjusting the first duty cycle and the second duty cycle based on the transfer function of each mode;

[0057] In the buck mode, the first duty cycle is adjusted by bilateral modulation TEM to minimize the inductor current ripple and the root mean square current, wherein:

[0058]

[0059] Among them, I L,avg is the average steady-state current, I L,avg =v o / R, T is the switching period, f sw is the switching frequency, T=1 / f sw ;Δi L,降压 is the inductor current ripple in buck mode, I L,RMS is the root mean square current; v in and v oare the input voltage of the input terminal and the output voltage of the output terminal, R is the load resistance, d1 and d2 represent the first duty cycle and the second duty cycle respectively;

[0060] In the boost mode, the second duty cycle is adjusted by bilateral TEM modulation to minimize the inductor current ripple and the RMS current, where:

[0061]

[0062] Among them, Δi L,升压 is the inductor current ripple in boost mode, I L,avg =v o / (R(1-d2)), d2 represents the second duty cycle;

[0063] In the buck-boost mode, the first duty cycle and the second duty cycle are synchronously adjusted through dual-mode TEM modulation to minimize the inductor current ripple and the RMS current, wherein:

[0064]

[0065] Among them, Δi L,降压-升压 is the inductor current ripple in buck-boost mode, I L,avg =v o d1 / (R(1-d2)).

[0066] In one embodiment of the present invention, the system further includes a microcontroller for calculating the minimum values ​​of the input inductance, output capacitance, and input capacitance based on the transfer functions of each mode.

[0067] From the above scheme, it can be seen that the advantages of the present invention are:

[0068] The control method for a four-switch buck-boost converter provided by the present invention reduces the inductor current ripple and the RMS value of the inductor current based on bilateral modulation TEM and dual-mode TEM control in different modes of buck, boost, and buck-boost, thereby improving the efficiency of the converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0069] Figure 1 is a schematic diagram of the structure of a four-switch buck-boost converter;

[0070] Figure 2 Schematic diagram of the overall flow of the converter control method;

[0071] Figure 3 shows the circuit conduction diagram of the buck mode;

[0072] Figure 4 It is the gate control signal of the buck mode;

[0073] Figure 5 shows the circuit conduction diagram of the boost mode;

[0074] Figure 6 is the gate control signal for boost mode,

[0075] Figure 7 This is the buck mode current waveform in CCM mode;

[0076] Figure 8 This is the boost mode current waveform in CCM mode. DETAILED DESCRIPTION

[0077] In order to make the above features and effects of the present invention more clearly understood, embodiments are given below and described in detail with reference to the accompanying drawings.

[0078] refer to Figure 1 As shown in Figure 1 The schematic diagram of the structure of the four-switch buck-boost converter is shown. The four-switch buck-boost converter includes a first circuit and a second circuit, the first circuit and the second circuit are cascaded between the input terminal and the output terminal, wherein the first circuit includes an input capacitor C in , first switch Q1, second switch Q SR1 , the input capacitor C in Connected in parallel to the input terminal, the second switch Q SR1 With the input capacitor C in The first switch Q1 is connected in series with the input capacitor C in With the second switch Q SR1 In one embodiment, the drain of Q1 is connected to the positive terminal of the input power supply, and the source is connected to Q SR1 Drain, Q SR1 The source is grounded. The second circuit includes an output capacitor C out , the third switch Q SR2 , the fourth switch Q2, the output capacitor C out The fourth switch Q2 is connected in parallel to the output terminal and the output capacitor C out connected in parallel, and the third switch Q SR2 Connected in series with the output capacitor C out Between the first circuit and the second circuit, an input inductor L is connected in series, and the output end is also connected in parallel with a load resistor R. In one embodiment, the source of the first switch Q1 is connected to one end of the inductor L, and the other end of the inductor L is connected to the drain of the fourth switch Q2 and the third switch Q SR2 Source; the source of the fourth switch Q2 is connected to the output capacitor C out The positive electrode and one end of the load R, the third switch Q SR2 The drain is connected to the source of Q2, and the third switch Q SR2The source is connected to the drain of Q2.

[0079] For the four-switch buck-boost converter, an embodiment of the present invention provides a control method for the four-switch buck-boost converter, referring to Figure 2 As shown, Figure 2 The overall flow chart of the converter control method is shown.

[0080] A method for controlling a four-switch buck-boost converter comprises at least the following steps:

[0081] Step S1: Based on the input voltage and the output voltage, and in continuous conduction mode, construct the average state space equation of the converter. The average state space equation of the converter is constructed as follows:

[0082]

[0083] Among them, v in and v o are the input voltage at the input end and the output voltage at the output end, i L is the current of the input inductor L, C is the output capacitor, R is the load resistance, d1 and d2 represent the first duty cycle and the second duty cycle respectively.

[0084] Step S2: Based on the average state-space equation, adjust the first duty cycle and the second duty cycle, switch the operating mode of the converter, and match the corresponding transfer function; wherein the first duty cycle is the on-duty cycle of the first switch, and the second duty cycle is the on-duty cycle of the fourth switch.

[0085] Among them, the four-switch buck-boost converter includes three modes: buck mode, boost mode, and buck-boost mode. The transfer function of each operating mode relates the duty cycle to the output voltage and the inductor current.

[0086] Figure 3 shows the circuit conduction diagram for buck mode, Figure 4 is the gate control signal for buck mode. In buck mode, the inductor and gate current waveforms are formed in continuous conduction mode (CCM), as shown in Figure 7 As shown. In buck mode, the input voltage v in Greater than the output voltage v o , at this time the second duty cycle is zero, the fourth switch Q2 is turned off, and the third switch Q SR2 The first switch and the second switch are turned on, and the voltage is stepped down by adjusting the first duty cycle d1 to control the complementary conduction of the first switch and the second switch.

[0087] In this buck mode, the transfer function is:

[0088]

[0089] Where s is the complex frequency variable of Laplace transform;

[0090] By adjusting the first duty cycle, the output voltage v o (s) satisfies v o (s)=v in d1(s).

[0091] Figure 5 The circuit conduction diagram of the boost mode is shown. Figure 6 is the gate control signal of the boost mode. In the boost mode, the inductor and gate current waveforms are formed in the continuous conduction mode (CCM), as shown in Figure 8 As shown. In boost mode, the input voltage v in is less than the output voltage v o , at this time the first duty cycle is 1, the first switch Q1 is turned on, and the second switch Q SR1 Turn off, and control the third switch Q by adjusting the second duty cycle d2 SR2 The complementary conduction of the fourth switch Q4 performs boost regulation.

[0092] In this boost mode, the transfer function is:

[0093]

[0094]

[0095] By adjusting the second duty cycle, the output voltage v o (s) satisfies v o (s)=v in / (1-d2).

[0096] For the buck-boost mode, the input voltage v in With the output voltage v o There is no fixed size relationship. At this time, the first duty cycle and the second duty cycle are both non-zero. By adjusting the first duty cycle and the second duty cycle, the on and off states of the first switch, the second switch, the third switch, and the fourth switch are controlled. In this state mode, the transfer function is:

[0097]

[0098] By adjusting the first duty cycle and the second duty cycle, the output voltage v o (s) satisfies v o (s)=v in d / (1-d), d1=d2=d.

[0099] Step S3: Based on the transfer functions of each mode, the first duty cycle and the second duty cycle are adjusted to minimize the inductor current ripple and the root mean square current.

[0100] In one embodiment, to improve converter efficiency, two-side modulation (TEM) and dual-mode TEM are employed to optimize the efficiency of the FSBB converter by minimizing both inductor current ripple and the RMS value of the inductor current. Two-side modulation (TEM) reduces the RMS value of the inductor current by minimizing the overlap between the switch on and off times, thereby reducing power consumption in the inductor and switching elements. Dual-mode TEM minimizes inductor current ripple by synchronizing the first duty cycle d1 and the second duty cycle d2 during the buck and boost phases, directly improving system efficiency.

[0101] In the buck mode, the first duty cycle is adjusted by bilateral TEM modulation to minimize the inductor current ripple and the RMS current, where:

[0102]

[0103] Among them, I L,avg is the average steady-state current, I L,avg =v o / R, T is the switching period, f sw is the switching frequency, T=1 / f sw ;Δi L,降压 is the inductor current ripple in buck mode, I L,RMS is the root mean square current; v in and v o are the input voltage of the input terminal and the output voltage of the output terminal, R is the load resistance, d1 and d2 represent the first duty cycle and the second duty cycle respectively;

[0104] In the boost mode, the second duty cycle is adjusted by bilateral TEM modulation to minimize the inductor current ripple and the RMS current, where:

[0105]

[0106] Among them, Δi L,升压 is the inductor current ripple in boost mode, I L,avg =v o / (R(1-d2)), d2 represents the second duty cycle;

[0107] In the buck-boost mode, the first duty cycle and the second duty cycle are synchronously adjusted through dual-mode TEM modulation to minimize the inductor current ripple and the RMS current, wherein:

[0108]

[0109] Among them, Δi L,降压-升压 is the inductor current ripple in buck-boost mode, I L,avg =v o d1 / (R(1-d2)).

[0110] Step S4: Calculate the minimum value of the input inductance, output capacitance, and input capacitance based on the transfer function of each mode.

[0111] Based on the characteristic parameters of the transfer function (such as L, C, and R), calculate the minimum values ​​of the input inductor L and output capacitor C to ensure that the hardware parameters match the model and achieve the theoretical performance of the transfer function.

[0112] Wherein, in buck mode, the input inductance is:

[0113]

[0114] In boost mode, the input inductor is:

[0115]

[0116] Among them, K ind is the current ripple factor, I out is the output current at the output terminal, is the maximum input voltage, is the minimum input voltage, L min is the minimum value of input inductance;

[0117] In buck mode, the output capacitance is:

[0118]

[0119] or,

[0120]

[0121] In boost mode, the output capacitance is:

[0122]

[0123] in, is the output voltage ripple, ΔV ot is the voltage regulation rate, is the minimum output voltage.

[0124] In buck mode, the input capacitance is:

[0125]

[0126] In boost mode, the input capacitance is:

[0127]

[0128] Among them, I om is the peak output current, is the peak-to-peak value of the input voltage.

[0129] In summary, the control method of the four-switch buck-boost converter provided by the present invention reduces the inductor current ripple and the root mean square value of the inductor current based on bilateral modulation TEM and dual-mode TEM control in different modes of buck, boost, and buck-boost, thereby improving the efficiency of the converter.

[0130] The embodiments of the present application are described above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of this application, ordinary technicians in this field can also make many forms without departing from the purpose of this application and the scope of protection of the claims, all of which are within the protection of this application.

Claims

1. A control method for a four-switch buck-boost converter, the converter comprising a first circuit and a second circuit, the first and second circuits being cascaded between an input terminal and an output terminal. The first circuit comprises an input capacitor, a first switch, and a second switch, the input capacitor being connected in parallel to the input terminal, the second switch being connected in parallel to the input capacitor, and the first switch being connected in series between the input capacitor and the second switch. The second circuit comprises an output capacitor, a third switch, and a fourth switch, the output capacitor being connected in parallel to the output terminal, the fourth switch being connected in parallel to the output capacitor, and the third switch being connected in series between the output capacitor and the fourth switch. An input inductor is connected in series between the first and second circuits, and a load resistor is also connected in parallel to the output terminal. It is characterized in that The method includes: According to the input voltage and output voltage, the average state space equation of the converter is constructed based on the continuous conduction mode; Based on the average state-space equation, adjusting a first duty cycle and a second duty cycle, switching the operating mode of the converter and matching the corresponding transfer function; wherein the first duty cycle is the on-duty cycle of the first switch, and the second duty cycle is the on-duty cycle of the fourth switch; Based on the transfer functions of each mode, the first duty cycle and the second duty cycle are adjusted to minimize the inductor current ripple and the root mean square current; wherein: In the buck mode, the first duty cycle is adjusted by bilateral modulation TEM to minimize the inductor current ripple and the RMS current, where: Among them, I L,avg is the average steady-state current, I L,avg =v o / R, T is the switching period, f sw is the switching frequency, T=1 / f sw ;Δi L,降压 is the inductor current ripple in buck mode, I L,RMS is the root mean square current; v in and v o are the input voltage of the input terminal and the output voltage of the output terminal, R is the load resistance, d1 and d2 represent the first duty cycle and the second duty cycle respectively; In the boost mode, the second duty cycle is adjusted by bilateral TEM modulation to minimize the inductor current ripple and the RMS current, where: Among them, Δi L,升压 is the inductor current ripple in boost mode, I L,avg =v o / (R(1-d2)), d2 represents the second duty cycle; In the buck-boost mode, the first duty cycle and the second duty cycle are synchronously adjusted through dual-mode TEM modulation to minimize the inductor current ripple and the RMS current, wherein: Among them, Δi L,降压-升压 is the inductor current ripple in buck-boost mode, I L,avg =v o d1 / (R(1-d2)).

2. The method according to claim 1, characterized in that Based on the continuous conduction mode, the average state space equation of the converter is constructed as: Among them, v in and v o are the input voltage at the input end and the output voltage at the output end, i L is the current of the input inductor L, C is the output capacitor, R is the load resistance, d1 and d2 represent the first duty cycle and the second duty cycle respectively.

3. The method according to claim 2, characterized in that In the buck mode, the input voltage is greater than the output voltage, the second duty cycle is zero, the fourth switch is turned off, and the third switch is turned on; The transfer function is: Where s is the complex frequency variable of Laplace transform; By adjusting the first duty cycle, the complementary conduction of the first switch and the second switch is controlled to perform step-down regulation so that the output voltage v o (s) satisfies v o (s)=v in d1(s).

4. The method according to claim 3, characterized in that In the boost mode, the input voltage is less than the output voltage, the first duty cycle is one, the first switch is turned on, and the second switch is turned off; The transfer function is: By adjusting the second duty cycle, the complementary conduction of the third switch and the fourth switch is controlled to perform boost regulation so that the output voltage v o (s) satisfies v o (s)=v in / (1-d2).

5. The method according to claim 3, characterized in that In the buck-boost mode, the input voltage and the output voltage have no fixed magnitude relationship, and both the first duty cycle and the second duty cycle are non-zero; The transfer function is: By adjusting the first duty cycle and the second duty cycle, the on and off states of the first switch, the second switch, the third switch, and the fourth switch are controlled so that the output voltage v o (s) satisfies v o (s)=v in d / (1-d), d1=d2=d.

6. The method according to claim 2, characterized in that Also includes: Based on the transfer function of each mode, the minimum values ​​of the input inductor, output capacitor, and input capacitor are calculated.

7. The method according to claim 6, characterized in that in, In buck mode, the input inductance is: In boost mode, the input inductor is: Among them, K ind is the current ripple factor, I out is the output current at the output terminal, is the maximum input voltage, is the minimum input voltage, L min is the minimum value of input inductance; In buck mode, the output capacitor C out for: or, In boost mode, the output capacitor C out for: in, is the output voltage ripple, ΔV ot is the voltage regulation rate, is the minimum output voltage; In buck mode, the input capacitor C in for: In boost mode, the input capacitor C in for: Among them, I om is the peak output current, is the peak-to-peak value of the input voltage.

8. A modulation control system for a four-switch buck-boost converter, characterized in that: Include: A four-switch buck-boost converter includes a first circuit and a second circuit, the first and second circuits being cascaded between an input terminal and an output terminal. The first circuit includes an input capacitor, a first switch, and a second switch. The input capacitor is connected in parallel to the input terminal, the second switch is connected in parallel to the input capacitor, and the first switch is connected in series between the input capacitor and the second switch. The second circuit includes an output capacitor, a third switch, and a fourth switch. The output capacitor is connected in parallel to the output terminal, the fourth switch is connected in parallel to the output capacitor, and the third switch is connected in series between the output capacitor and the fourth switch. An input inductor is connected in series between the first and second circuits, and a load resistor is also connected in parallel to the output terminal. a PWM controller configured to control a first duty cycle and a second duty cycle, control the on and off states of the first switch, the second switch, the third switch, and the fourth switch, switch an operating mode, and match a corresponding transfer function; and minimize the inductor current ripple and the root mean square current by adjusting the first duty cycle and the second duty cycle based on the transfer function of each mode; In the buck mode, the first duty cycle is adjusted by bilateral modulation TEM to minimize the inductor current ripple and the root mean square current, wherein: Among them, I L,avg is the average steady-state current, I L,avg =v o / R, T is the switching period, f sw is the switching frequency, T=1 / f sw ;Δi L,降压 is the inductor current ripple in buck mode, I L,RMS is the root mean square current; v in and v o are the input voltage of the input terminal and the output voltage of the output terminal, R is the load resistance, d1 and d2 represent the first duty cycle and the second duty cycle respectively; In the boost mode, the second duty cycle is adjusted by bilateral TEM modulation to minimize the inductor current ripple and the RMS current, where: Among them, Δi L,升压 is the inductor current ripple in boost mode, I L,avg =v o / (R(1-d2)), d2 represents the second duty cycle; In the buck-boost mode, the first duty cycle and the second duty cycle are synchronously adjusted through dual-mode TEM modulation to minimize the inductor current ripple and the RMS current, wherein: Among them, Δi L,降压-升压 is the inductor current ripple in buck-boost mode, I L,avg =v o d1 / (R(1-d2)).

9. The system according to claim 8, characterized in that in: In the buck mode, the input voltage is greater than the output voltage, the second duty cycle is zero, the fourth switch is turned off, and the third switch is turned on; The transfer function is: By adjusting the first duty cycle, the complementary conduction of the first switch and the second switch is controlled to perform step-down regulation so that the output voltage v o (s) satisfies v o (s)=v in d1(s); In the boost mode, the input voltage is less than the output voltage, the first duty cycle is one, the first switch is turned on, and the second switch is turned off; The transfer function is: Where s is the complex frequency variable of Laplace transform; By adjusting the second duty cycle, the complementary conduction of the third switch and the fourth switch is controlled to perform boost regulation so that the output voltage v o (s) satisfies v o (s)=v in / (1-d2); In the buck-boost mode, the input voltage and the output voltage have no fixed magnitude relationship, and both the first duty cycle and the second duty cycle are non-zero; The transfer function is: By adjusting the first duty cycle and the second duty cycle, the on and off states of the first switch, the second switch, the third switch and the fourth switch are controlled so that the output voltage v o (s) satisfies v o (s)=v in d / (1-d), d1=d2=d.

10. The system according to claim 9, characterized in that The invention also includes a microcontroller for calculating the minimum value of the input inductor, the output capacitor and the input capacitor based on the transfer function of each mode.

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