Single-inductor dual-output Buck-Boost converter parameter design method

Abstract

This invention discloses a parameter design method for a single-inductor dual-output Buck-Boost converter. For the branch exhibiting negative voltage regulation in the single-inductor dual-output Buck-Boost converter, current control is employed, while for the branch without negative voltage regulation, voltage control is used. Then, using the operating mode and output ripple voltage as constraints, the parameters of the inductor and capacitor of the single-inductor dual-output Buck-Boost converter are designed. Furthermore, the range of control parameter values ​​is obtained using the Routh-Hulwitz criterion, and the control parameters are optimized using eigenvalue sensitivity. The design is then complete. This invention addresses the negative voltage regulation phenomenon in the output voltage of the single-inductor dual-output Buck-Boost converter by designing control parameters to suppress cross-influence between output branches.

Description

Technical Field

[0001] This invention belongs to the field of converter technology, specifically relating to a parameter design method for a single-inductor dual-output Buck-Boost converter. Background Technology

[0002] With the rapid development of power electronics technology, portable electronic devices, such as wearable devices and smartphones, have seen rapid growth. Single-Inductor Dual-Output (SIDO) DC-DC switching converters achieve dual outputs using a single inductor and have gained increasing attention due to their advantages such as no electromagnetic interference, simple structure, and high output accuracy.

[0003] SIDO DC-DC switching converters share the energy in a single inductor and work together as a whole to perform boost and buck functions. Therefore, there is cross-influence between their two output branches. Mild cross-influence affects the system's transient performance; severe cross-influence affects the system's stability. Furthermore, the transient mathematical models of SIDO DC-DC switching converter topologies, such as SIDO Boost, SIDO Buck-Boost, SIDO Flyback, and their derivatives, contain right-half-plane zeros. This type of system belongs to the category of non-minimum-phase systems. When a sudden increase (or decrease) in the duty cycle occurs, the output voltage initially exhibits a transient transition process, characterized by an initial decrease followed by an increase (or vice versa), known as negative modulation. A mild negative modulation can affect the system's transient performance; a severe negative modulation can also impact system stability. Furthermore, non-minimum-phase systems cannot be designed using traditional frequency domain methods, complicating controller design.

[0004] To suppress the cross-influence between the output branches of SIDO DC-DC switching converters, a large number of studies have been conducted. One such study is the stability and transient characteristics analysis of a current-mode controlled single-inductor dual-output switching converter [J]. Journal of Electrical Engineering, 2018, 33(6): 1374-1381. (The last sentence appears to be incomplete and possibly refers to a separate topic: continuous conduction mode of inductor current.) Taking the SIDO Boost converter as an example, the stability and transient characteristics of its current control are analyzed. The results show that, compared with voltage-type control, current-type control not only improves the transient response speed of the system but also effectively suppresses the cross-influence between output branches. Other literature proposes a ripple averaging model control for the CCM SIDO Buck-Boost converter and introduces the concept of a cross-adjustment factor to evaluate the influence of key circuit parameters on the system's cross-influence. The literature "Constant Valley Current-Type Frequency Conversion Control: Modeling and Analysis of CCM Single-Inductor Dual-Output Boost Converter" [J]. Proceedings of the CSEE, 2018, 38(23): 7015-7025+7135. Taking the CCM SIDO Boost converter as an example, a constant valley current-type frequency conversion control method is proposed. The transient performance and the improvement of cross-influence are analyzed by deriving the closed-loop output impedance and cross-influence transfer function. The literature *Exact feedback linearisation optimal control for single-inductor dual-output boost converter* [J]. IET Power Electronics, 2020, 13(11): 2293-2301. This paper describes the implementation of exact feedback linearisation optimal control for a CCM SIDO boost converter, aiming to improve system transient performance by optimizing the control law. While the above literature primarily studies the cross-influence of SIDO DC-DC converters, no reports have yet been found regarding the non-minimum phase characteristics of SIDO DC-DC converters containing RHPZ. Summary of the Invention

[0005] The purpose of this invention is to provide a parameter design method for a single-inductor dual-output Buck-Boost converter, and to design control parameters to address the negative adjustment phenomenon of the output voltage of the single-inductor dual-output Buck-Boost converter branch, thereby suppressing the cross-influence between the output branches.

[0006] The technical solution adopted in this invention is a parameter design method for a single-inductor dual-output Buck-Boost converter. For the branch of the single-inductor dual-output Buck-Boost converter exhibiting negative regulation, current control is used, while for the other branch without negative regulation, voltage control is used. Then, using the operating mode and output ripple voltage as constraints, the parameters of the inductor and capacitor of the single-inductor dual-output Buck-Boost converter are designed. Furthermore, the range of control parameter values ​​is obtained by combining the Routh-Herwitz criterion. Simultaneously, the control parameters are optimized using eigenvalue sensitivity, thus completing the design.

[0007] The invention is further characterized in that,

[0008] The specific steps are as follows:

[0009] Step 1: Establish the SIDO Buck-Boost converter model

[0010] The SIDO Buck-Boost converter model includes a main circuit, which is connected to two branches with identical circuit structures.

[0011] Step 2: Since the output voltage of the first-turned branch of the SIDO Buck-Boost converter exhibits a negative adjustment phenomenon, voltage control is used for branches without negative adjustment, and inductor current control is used for branches with negative adjustment. Calculate the control signals for voltage control and inductor current control.

[0012] Step 3: Design the SIDO Buck-Boost converter circuit parameters;

[0013] Step 4: Design the control parameters of the SIDO Buck-Boost converter based on the analysis of the eigenvalue sensitivity.

[0014] The main circuit of the SIDO Buck-Boost converter model includes the main power switches S0 and S3, as well as the power diode VD and the energy storage inductor. L Flowing L The current is i L The main input voltage source is v i The drive signal for S0 or S3 is V GS0 The duty cycle of S0 is d i The main circuit is connected to branches a and b, which have the same circuit structure. Branch a includes the branch a switch S1 and a filter capacitor. C a Load resistance R a The output voltage of branch a is v a The drive signal for S1 is V GS1 The duty cycles of S1 are respectively d a Branch b includes branch b switch S2 and filter capacitor. C b Load resistance R b The output voltage of branch b is v b The drive signal for S2 is V GS2 The duty cycles of S2 are respectively d bAnd satisfy d a + d b =1, in the SIDO Buck-Boost converter, the switch S1 in the middle branch a is turned on first.

[0015] Step 2: In the control of the SIDO Buck-Boost converter, voltage control is used for branch b without negative adjustment, specifically proportional-integral (PI) control, with PI3 as the controller. For branch a with negative adjustment, inductor current control is used, specifically outer-loop voltage PI control and inner-loop current PI control. PI1 is the controller for the outer-loop voltage PI control of branch a, and PI2 is the controller for the inner-loop current PI control of branch a. The control signals generated by the two branches of the SIDO Buck-Boost converter are then compared with a standard sawtooth wave signal by comparators after passing through the PWM generation circuit.

[0016] (39)

[0017] In equation (39), v e1 and v e2 These are the control signals for comparators CMP1 and CMP2, respectively. ,and i Lref Indicates the reference value of inductor current. k p1 and k i1 These represent the proportional and integral coefficients of the outer loop voltage controller PI1 in branch a, respectively. k p2 and k i2 These represent the proportional coefficient and integral coefficient of PI2, the inner loop current controller of branch a, respectively. k p3 and k i3 These represent the proportional and integral coefficients of the voltage controller PI3 in branch b, respectively.

[0018] Step 3 specifically involves:

[0019] Based on the operating principle and energy transfer mode of the SIDO Buck-Boost converter, determine the critical inductance of the SIDO Buck-Boost converter. L C for:

[0020] (40)

[0021] From the analysis of equation (40), it can be seen that when L > L C At this time, the converter operates in CCM mode; therefore, the inductor should be greater than 2. L C ;

[0022] Calculate the capacitor that meets the ripple voltage requirement. C ka and C kb for:

[0023] (41)

[0024] In equation (41), V PP-a and V PP-b These are the maximum output ripple voltages of branch a and branch b, respectively. V a , V b , V i , D i They are respectively v a , v b , d i steady-state value, f This indicates the system switching frequency.

[0025] Step 4 is as follows:

[0026] Characteristic root sensitivity The expression is:

[0027] (42)

[0028] In equation (42), b These are control parameters. l i These are the system's characteristic roots. q i , p i These are the Jacobian matrices. J The left and right eigenvectors; the eigenvalue sensitivity is a complex number, and s The absolute value reflects the degree of influence of the parameter on the system stability. p> When the value is 0, decreasing this parameter will improve the stability of the system, while increasing this parameter will decrease the stability of the system.

[0029] Let the system state variable be x =[x 1 x 2 x 3 x 4 x 5]=[ i L v a v b d i d b ],

[0030] The system state variables are obtained using the state-space averaging method:

[0031] (25)

[0032] Combining equations (25) and (39), we can obtain the Jacobian matrix of the CCM SIDO Buck-Boost converter. J for:

[0033] (43)

[0034] The closed-loop characteristic equation of the system described by equation (43) is:

[0035] (44)

[0036] In equation (44), a , b , c , d and e All of these are coefficients of the characteristic equation;

[0037] According to the Routh-Hurwitz criterion, when the system is stable, the control parameters must satisfy:

[0038] (45)

[0039] In equation (45), β =( ad e ) / a .

[0040] The beneficial effects of this invention are:

[0041] This invention presents a parameter design method for a single-inductor dual-output Buck-Boost converter. It proposes using current control for the branch exhibiting negative regulation and voltage control for the branch without negative regulation. Subsequently, using the operating mode and output ripple voltage as constraints, the parameter design methods for the inductor and capacitor are derived. Then, the Routh-Hulwitz criterion is used to obtain the range of control parameter values, and the characteristic root sensitivity is applied to optimize the control parameters. Compared to traditional voltage control, this method exhibits superior transient performance, effectively suppresses cross-influence between output branches, and has a simple control structure, making it valuable for engineering applications. Attached Figure Description

[0042] Figure 1 This is the circuit topology diagram of the SIDO Buck-Boost converter;

[0043] Figure 2 This is the control block diagram of the SIDO Buck-Boost converter;

[0044] Figure 3 This is the PWM generation circuit diagram for the SIDO Buck-Boost converter;

[0045] Figure 4 yes k p2 Trend graph of system eigenvalues ​​during change;

[0046] Figure 5 shows the load current of branch a. I a The simulation results of the sudden change are shown in Figure 5(a), where the load current of converter branch a under voltage control is shown. I a The simulation results of the sudden change are shown in Figure 5(b), which is the load current of converter branch a under the control of the present invention. I a Simulation results of the mutation;

[0047] Figure 6 shows the load current of branch b. I b The simulation results of the sudden change are shown in Figure 6(a), where the load current of converter branch b under voltage control is shown. I b The simulation results of the sudden change are shown in Figure 6(b), which is the load current of converter branch b under the control of the present invention. I b Simulation results of the mutation;

[0048] Figure 7 shows the input voltage. V i The simulation results of the sudden change are shown in Figure 7(a), where the input voltage under voltage control is shown. V iThe simulation results of the sudden change are shown in Figure 7(b), which is the input voltage under the control of the present invention. V i Simulation results of the mutation;

[0049] Figure 8 shows the load current of branch a. I a The experimental results of the mutation are shown in Figure 8(a), where Figure 8(a) shows the load current of converter branch a under voltage control. I a The experimental results of the mutation are shown in Figure 8(b), which shows the load current of converter branch a under the control of the present invention. I a The experimental results of the mutation are shown in the figure;

[0050] Figure 9 shows the load current of branch b. I b The experimental results of the sudden change are shown in Figure 9(a), where Figure 9(a) shows the load current of converter branch b under voltage control. I b The experimental results of the mutation are shown in Figure 9(b), which shows the load current of converter branch b under the control of the present invention. I b The experimental results of the mutation are shown in the figure;

[0051] Figure 10 shows the input voltage. V i The experimental results of the mutation are shown in Figure 10(a), where the input voltage under voltage control is shown in Figure 10(a). V i The experimental results of the mutation are shown in Figure 10(b), which shows the input voltage under the control of the present invention. V i The experimental results of the mutation are shown in the figure. Detailed Implementation

[0052] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0053] This invention discloses a parameter design method for a single-inductor dual-output Buck-Boost converter. The method employs current control for the branch exhibiting negative regulation in the single-inductor dual-output Buck-Boost converter, and voltage control for the other branch without negative regulation. Then, using the operating mode and output ripple voltage as constraints, the parameters of the inductor and capacitor of the single-inductor dual-output Buck-Boost converter are designed. Furthermore, the range of control parameter values ​​is obtained by combining the Routh-Herwitz criterion. Simultaneously, the control parameters are optimized using eigenvalue sensitivity, thus completing the design.

[0054] The specific steps are as follows:

[0055] Step 1: Establish the SIDO Buck-Boost converter model

[0056] The SIDO Buck-Boost converter circuit topology is as follows: Figure 1 As shown, the SIDO Buck-Boost converter model includes a main circuit, which is connected to two branches with identical circuit structures. The main circuit of the SIDO Buck-Boost converter model includes main power switches S0 and S3, as well as a power diode VD and an energy storage inductor. L Flowing L The current is i L The main input voltage source is v i The drive signal for S0 or S3 is V GS0 The duty cycle of S0 is d i The main circuit is connected to branches a and b, which have the same circuit structure. Branch a includes the branch a switch S1 and a filter capacitor. C a Load resistance R a The output voltage of branch a is v a The drive signal for S1 is V GS1 The duty cycles of S1 are respectively d a Branch b includes branch b switch S2 and filter capacitor. C b Load resistance R b The output voltage of branch b is v b The drive signal for S2 is V GS2 The duty cycles of S2 are respectively d b And satisfy d a + d b =1, in the SIDO Buck-Boost converter, the switch S1 in the middle branch a is turned on first.

[0057] Step 2: Since the output voltage of the first-turned branch of the SIDO Buck-Boost converter exhibits a negative adjustment phenomenon, voltage control is used for branches without negative adjustment, and inductor current control is used for branches with negative adjustment. Calculate the control signals for voltage control and inductor current control.

[0058] Dynamic stability analysis of the system with voltage control in branch a

[0059] according to Figure 1 And the state-space averaging method yields:

[0060] (25)

[0061] Select control variables u =[ u 1 u 2] T =[ d i d a ] T Output feedback quantity y = h ( x )= x 2. By rearranging and simplifying equation (25), the nonlinear system control model of the converter can be obtained as follows:

[0062] (26)

[0063] In equation (26),

[0064] , , .

[0065] Substituting equation (26) into equation (25), we get:

[0066] (27)

[0067] Analysis of equation (27) shows that the system's relative order c =1<3, in order to achieve coordinate transformation, the system needs to rebuild the output function. oh ( x ),in oh ( x The following conditions must be met:

[0068] (28)

[0069] In equation (28), L g1 oh ( x )and L g2 oh ( x ) are respectively oh ( x )along g 1( x )and g 2( x Lie derivative;

[0070] From the analysis of equation (28), we can obtain:

[0071] (29)

[0072] Since the output voltage of branch b does not exhibit negative adjustment, the new state variable of the system is... Take as:

[0073] (30)

[0074] Substituting equation (30) into equation (25), we obtain the nonlinear canonical form of the system after transformation as follows:

[0075] (31)

[0076] In equation (31), .

[0077] From the analysis of equation (31), we can see that the dynamics within the system are:

[0078] (32)

[0079] when g= At time 0, the zero dynamics of the system are:

[0080] (33)

[0081] Analysis of equation (33) shows that the system has an unstable zero dynamic.

[0082] Dynamic stability analysis of the system with current control in branch a:

[0083] Select output feedback quantity y = h ( x )= x 1. Substituting into equation (25), we get:

[0084] (34)

[0085] Analysis of equation (34) shows that the system's relative order c =1<3, and similarly, the new state variables of the system are taken as:

[0086] (35)

[0087] Substituting equation (35) into equation (25), we obtain the nonlinear canonical form of the system after transformation as follows:

[0088] (36)

[0089] From the analysis of equation (36), we can see that the dynamics within the system are:

[0090] (37)

[0091] when g= At time 0, the zero dynamics of the system are:

[0092] (38)

[0093] Analysis of equation (38) shows that the system does not have an unstable zero dynamic.

[0094] In summary, the analysis shows that when the output voltage is selected as the output variable for branch a, the system is unstable; when the inductor current is selected as the output variable for branch a, the system is stable. Therefore, in the control of the SIDO Buck-Boost converter, voltage control is used for the branch without negative adjustment (branch b), and inductor current control is used for the branch with negative adjustment (branch a).

[0095] The system control structure diagram is as follows: Figure 2 As shown, in the control of the SIDO Buck-Boost converter, voltage control is used for branch b without negative adjustment, specifically proportional-integral (PI) control, with PI3 as the controller. For branch a with negative adjustment, inductor current control is used, specifically outer-loop voltage PI control and inner-loop current PI control. PI1 is the controller for the outer-loop voltage PI control of branch a, and PI2 is the controller for the inner-loop current PI control of branch a. The control signals generated by the two branches of the SIDO Buck-Boost converter are then compared with a standard sawtooth wave signal via PWM after passing through comparators. Figure 3 As shown, Figure 3 In the middle, CMP1 and CMP2 are respectively... v e1 and v e2 The corresponding comparator, v ramp It is a standard sawtooth wave signal, and has

[0096] (39)

[0097] In equation (39), v e1 and v e2 These are the control signals for comparators CMP1 and CMP2, respectively. ,and i Lref Indicates the reference value of inductor current. k p1 and k i1These represent the proportional and integral coefficients of the outer loop voltage controller PI1 in branch a, respectively. k p2 and k i2 These represent the proportional coefficient and integral coefficient of PI2, the inner loop current controller of branch a, respectively. k p3 and k i3 These represent the proportional coefficient and integral coefficient of the voltage controller PI3 in branch b, respectively.

[0098] Step 3: Design the SIDO Buck-Boost converter circuit parameters;

[0099] Step 3 specifically involves:

[0100] Based on the operating principle and energy transfer mode of the SIDO Buck-Boost converter, determine the critical inductance of the SIDO Buck-Boost converter. L C for:

[0101] (40)

[0102] From the analysis of equation (40), it can be seen that when L > L C At this time, the converter operates in CCM mode; therefore, the inductor should be greater than 2. L C Once the inductance is determined, the capacitor value that meets the ripple requirements is calculated based on the inductance value.

[0103] The capacitor that meets the ripple voltage requirement is calculated based on the operating principle of the SIDO Buck-Boost converter. C ka and C kb for:

[0104] (41)

[0105] In equation (41), V PP-a and V PP-b These are the maximum output ripple voltages of branch a and branch b, respectively. V a , V b , V i , D i They are respectively v a , vb , d i steady-state value, f This indicates the system switching frequency.

[0106] Equations (40) and (41) provide the inductor and capacitor design principles to meet the requirements of the converter's operating mode. When the SIDOBuck-Boost converter uses current control for the RHPZ branch, the system is in minimum phase. Therefore, the circuit parameter design mainly considers the converter's operating mode and the output ripple voltage requirements.

[0107] Step 4: Design the control parameters of the SIDO Buck-Boost converter based on the analysis of the eigenvalue sensitivity. The control parameters not only affect the transient performance of the converter, but also the stability of the system.

[0108] Characteristic root sensitivity The expression is:

[0109] (42)

[0110] In equation (42), b These are control parameters. l i These are the system's characteristic roots. q i , p i These are the Jacobian matrices. J The left and right eigenvectors; the eigenvalue sensitivity is a complex number, and s The absolute value reflects the degree of influence of the parameter on the system stability. p> When the value is 0, decreasing this parameter will improve the stability of the system, while increasing this parameter will decrease the stability of the system.

[0111] Let the system state variable be x =[ x 1 x 2 x 3 x 4 x 5]=[ i L v a v b d i d b ],

[0112] System state variables:

[0113] (25)

[0114] Combining equations (25) and (39), we can obtain the Jacobian matrix of the CCM SIDO Buck-Boost converter. J for:

[0115] (43)

[0116] The closed-loop characteristic equation of the system described by equation (43) is:

[0117] (44)

[0118] In equation (44), a , b , c , d and e All of these are coefficients of the characteristic equation.

[0119] According to the Routh-Hurwitz criterion, when the system is stable, the control parameters must satisfy:

[0120] (45)

[0121] In equation (45), β =( ad e ) / a .

[0122] The following is an analysis of a set of SIDO Buck-Boost converter parameters: V i =30V, V a =10V, V b =20V, R a =10Ω, R b =20Ω, f =40kHz, according to equations (40) and (41) we can obtain C a = C b =470μF, L =500μH. To facilitate the analysis of the influence of control parameters on system stability, the range of control parameters can be obtained according to equation (45): when k p1 = k p3 =0.1, k i1 = k i2 =k i3 When =120, k p2 >0.0007, this article takes k p2 =0.15. Substituting into equation (43), the closed-loop characteristic roots of the system are shown in Table 1. As can be seen from Table 1, the real parts of the characteristic roots of the system are all negative, indicating that the system is stable at the equilibrium point.

[0123] Table 1 System Characteristic Roots

[0124]

[0125] To analyze the influence of control parameter b on the stability of the closed-loop system, the sensitivity of the control parameter can be obtained by substituting the given data into equation (42), as shown in Table 2.

[0126] Analysis of Table 2 shows that, k p2 It is more likely to affect system stability and reduce k p1 , k i2 and k p3 Increase k i1 , k p2 and k i3 It helps improve system stability.

[0127] Table 2. Sensitivity of characteristic roots to control parameters

[0128]

[0129] analyze Figure 4 It can be seen that when k p2 When the value decreases from 0.15 to 0.0006, the system characteristic roots l 5 and conjugate characteristic roots l 3,4 All move from the left half of the complex plane toward the imaginary axis, and when k p2 When <0.00065, the conjugate characteristic roots l 3,4 When the system moves beyond the right half of the complex plane beyond the imaginary axis, it becomes unstable, consistent with the sensitivity analysis results.

[0130] Simulation Analysis and Experimental Verification

[0131] (I) Simulation Analysis

[0132] To verify the correctness of the theoretical analysis, simulation circuits for both control and voltage control were built in the power electronics simulation software PSIM based on the SIDO Buck-Boost converter circuit parameters in Table 3 for comparison. Simulation analyses of load surges and input power supply voltage surges are presented below, with specific simulation results.

[0133] Table 3 SIDO Buck-Boost Converter Circuit Parameters

[0134]

[0135] Figure 5 shows the load current of branch a. I a Simulation results for a sudden increase from 1A to 2A. As shown in Figure 5(a), at 35ms, with branch a loaded, the maximum voltage overshoot caused by the self-disturbance of converter branch a under voltage control is 1.8V, and the maximum voltage overshoot of branch b caused by the load change of branch a is 5.0V. The system recovers to a stable state in 2.7ms. However, as shown in Figure 5(b), the maximum voltage overshoot caused by the self-disturbance of converter branch a under the control of this invention is 0.4V, and the maximum voltage overshoot of branch b caused by the load change of branch a is 0.06V. The system recovers to a stable state in 1.7ms. Therefore, the cross-influence of converter branch a on branch b under the control of this invention is less than that under voltage control.

[0136] Figure 6 shows the load current of branch b. I b Simulation results for a sudden increase from 1A to 2A. As shown in Figure 6(a), at 35ms, with branch b loaded, the maximum voltage overshoot caused by the disturbance of branch b itself under voltage control is 6.2V, and the maximum voltage overshoot of branch a caused by the load change of branch b is 2.1V. That is, the cross-effect of branch b on branch a is 2.1V, and the system recovers to a stable state in 3.2ms. However, as shown in Figure 6(b), under the control of this invention, the maximum voltage overshoot caused by the disturbance of branch b itself is 2.7V, and the maximum voltage overshoot of branch a caused by the load change of branch b is 0.15V. That is, the cross-effect of branch b on branch a is 0.15V, and the system recovers to a stable state in 2.0ms. Therefore, the cross-effect of the converter branch b on branch a controlled by this invention is less than that under voltage control.

[0137] Figure 7 shows the input voltage. V i Simulation results of a sudden voltage increase from 15V to 25V. As shown in Figure 7(a), V iDuring the sudden increase, the output voltage of the two branches of the voltage-controlled converter recovers to a stable state in 3.0ms; while as shown in Figure 7(b), the output voltage of the two branches of the converter in this paper recovers to a stable state in 1.2ms, and the maximum overshoot of the voltage of both branches is less than that of the voltage control.

[0138] (II) Experimental Verification

[0139] To further test the effectiveness of the control strategy, an experimental platform was built using the same parameters as the simulation. Similarly, the experimental part included system load disturbance immunity testing and input power supply voltage disturbance testing. Specific experimental results are as follows.

[0140] Figure 8 shows the load current of branch a. I a Simulation results of a sudden increase from 1A to 2A. As shown in Figure 8(a), when branch a is loaded, the voltage-controlled system recovers to a steady state in 8.0ms, and the maximum overshoot of branch b during the adjustment process is 8.8V; while as shown in Figure 8(b), the converter controlled by this invention recovers to a steady state in 3.8ms, and the maximum overshoot voltage of branch b during the adjustment process is 2.2V.

[0141] Figure 9 shows the load current of branch b. I b Simulation results for a sudden increase from 1A to 2A. As shown in Figure 9(a), when branch b is loaded, the converter under voltage control recovers to a stable state in 8.0ms, and the maximum overshoot of branch a during the adjustment process is 7.8V, that is, the cross-effect of branch b on branch a is 7.8V; while as shown in Figure 9(b), the converter under the control of this invention recovers to a stable state in 3.8ms, and the maximum overshoot voltage of branch a during the adjustment process is 2.2V, that is, the cross-effect of branch b on branch a is 2.2V.

[0142] Keep R a =10Ω, R b =20Ω, so that the input voltage V i Figure 10 shows the experimental waveforms of the two control strategies when the voltage changes abruptly from 15V to 25V. From Figure 10(a), it can be seen that the overshoot voltage of voltage control branch a is 3.8V, the overshoot voltage of branch b is 7.8V, and the settling time is 13.5ms. From Figure 10(b), it can be seen that the overshoot voltage of the control branch a in this invention is 1.8V, the overshoot voltage of branch b is 3.9V, and the settling time is 3.5ms.

[0143] In summary, the experimental results show that, compared with simultaneous voltage control of both branches, the proposed control strategy exhibits faster transient response and less cross-influence when input voltage and load disturbances occur. Compared with simulation results, the experimental results show larger transient settling time and overshoot voltage. This is because parasitic parameters exist in the components of the experimental circuit, and sensors are used in the control circuit, resulting in slightly larger experimental results than simulation results.

[0144] As can be seen from the above, the parameter design method of the single-inductor dual-output Buck-Boost converter of the present invention takes the CCMSIDO Buck-Boost converter as the research object, establishes a transient mathematical model, analyzes the negative voltage generation mechanism, and adopts current control for the first-conducting branch and voltage control for the second-conducting branch.

[0145] 1) The transfer function of the control / output of the first-conducting branch has a right-half-plane zero, while the transfer function of the control / output of the second-conducting branch does not. When a sudden change in duty cycle occurs, the output voltage of the first-conducting branch exhibits a negative adjustment phenomenon, while the output voltage of the second-conducting branch does not.

[0146] 2) The control of the first conducting branch can be converted into current control to solve the non-minimum phase characteristics of the system; the control of the second conducting branch can be kept as voltage control to simplify the system control structure.

[0147] 3) Compared to traditional voltage control, the method of using current control for the first-conducting branch and voltage control for the subsequent-conducting branch improves the system's transient performance and effectively suppresses cross-influence between output branches. Furthermore, the control structure is simple, easy to program, and has engineering application value.

Claims

1. A method of parameter design for a single-inductor dual-output Buck-Boost converter, characterized in that, The branch with negative regulation phenomenon of the single-inductor dual-output Buck-Boost converter is controlled by current, and the branch without negative regulation phenomenon is controlled by voltage; then, the parameters of the inductor and capacitor of the single-inductor dual-output Buck-Boost converter are designed under the constraints of the working mode and the output ripple voltage, and the range of the control parameters is obtained by combining the Routh-Hurwitz criterion, and the control parameters are optimized by using the eigenvalue sensitivity.

2. The single-inductor dual-output Buck-Boost converter parameter design method of claim 1, wherein, The method is implemented according to the following steps: Step 1: establishing a model of the SIDO Buck-Boost converter The model of the SIDO Buck-Boost converter comprises a main path, and the main path is connected with two branch circuits with the same structure; Step 2: the branch circuit without negative regulation phenomenon is controlled by voltage, and the branch circuit with negative regulation phenomenon is controlled by inductor current, and the control signals of voltage control and inductor current control are calculated; Step 3: designing the circuit parameters of the SIDO Buck-Boost converter; Step 4: designing the control parameters of the SIDO Buck-Boost converter according to the analysis of the eigenvalue sensitivity.

3. The single-inductor dual-output Buck-Boost converter parameter design method of claim 2, wherein, The main circuit of the SIDO Buck-Boost converter model comprises main power switch tubes S0 and S3, and further comprises a power diode VD and an energy storage inductor L , the current flowing through L is i L , the input voltage source of the main circuit is v i , the driving signal of S0 or S3 is V GS0 , the duty ratio of S0 is d i , the main circuit is connected with a branch a and a branch b which have the same circuit structure, the branch a comprises a branch a switch tube S1, a filter capacitor C a and a load resistor R a , the output voltage of the branch a is v a , the driving signal of S1 is V GS1 , the duty ratio of S1 is d a , the branch b comprises a branch b switch tube S2, a filter capacitor C b and a load resistor R b , the output voltage of the branch b is v b , the driving signal of S2 is V GS2 , the duty ratio of S2 is d b , and the following conditions are met d a + d b , and the branch a switch tube S1 is turned on first in the two branches of the SIDO Buck-Boost converter.

4. The single-inductor dual-output Buck-Boost converter parameter design method of claim 3, wherein, In the step 2, the branch circuit b without negative regulation phenomenon is controlled by voltage, and the controller is PI3, and the branch circuit a with negative regulation phenomenon is controlled by inductor current, and the controller of the outer ring voltage PI control of the branch circuit a is PI1, and the controller of the inner ring current PI control of the branch circuit a is PI2; the control signals generated by the two branch circuits of the SIDO Buck-Boost converter are compared with the standard sawtooth wave signal through the comparators after PWM, and the control signals are compared with the standard sawtooth wave signal through the comparators after PWM (39) In formula (39), v e1 and v e2 are the generated control signals of branch a and branch b respectively, and are also the control signals of the two comparators respectively, , and i Lref represents the inductance current reference value, k p1 and k i1 respectively represent the proportional coefficient and the integral coefficient of the outer ring voltage controller PI1 of branch a, k p2 and k i2 respectively represent the proportional coefficient and the integral coefficient of the inner ring current controller PI2 of branch a, k p3 and k i3 respectively represent the proportional coefficient and the integral coefficient of the voltage controller PI3 of branch b.

5. The single-inductor dual-output Buck-Boost converter parameter design method of claim 3, wherein, The step 3 is specifically: According to the working principle and energy transmission mode of the SIDO Buck-Boost converter, the critical inductance of the SIDO Buck-Boost converter is determined L C is: (40) From equation (40), it is known that when L < / L L < / L C the converter operates in CCM, and thus the inductance is selected to be greater than 2 L < / L C ; A capacitance that meets the ripple voltage requirement is calculated C ka and C kb is: (41) in formula (41), V PP-a and V PP-b are the maximum output ripple voltages of branch a and branch b, respectively, V a , V b , V i , D i are the v a , v b , v i 、d i steady state values of f denotes the system switching frequency.

6. The single-inductor dual-output Buck-Boost converter parameter design method of claim 3, wherein, The step 4 is specifically: Step 4.1: eigenvalue sensitivity analysis Eigenvalue sensitivity The expression for the eigenvalue sensitivity is: (42) In formula (42), b is a control parameter, λ i is a system eigenvalue, q i , p i are left and right eigenvectors of Jacobian matrix J respectively; the eigenvalue sensitivity is a complex number, and σ the absolute value reflects the influence degree of the parameter on the system stability, when σ> 0, reducing the parameter is conducive to improving the stability of the system, and increasing the parameter will reduce the stability of the system; Let the system state variable be x [ x 1 x 2 x 3 x 4 x 5] i L v a v b d i d b ] According to the state space average method, the system state variables are obtained: (25) Solving equations (25) and (39) simultaneously yields the Jacobian matrix of the CCM SIDO Buck-Boost converter J is: (43) The system closed-loop characteristic equation described in the formula (43) is: (44) In formula (44), a , b , c , d and e are coefficients of the characteristic equation. According to the Routh-Hurwitz criterion, when the system is stable, the control parameters need to satisfy: (45) In equation (45), β =( ad e ) / a .

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