A phase-shift control method for a four-switch boost-buck converter

Abstract

The application discloses a phase-shifting control method of a four-switch converter, and belongs to the field of wide-range DC-DC converters in the field of power electronics. The four-switch converter is controlled based on a phase-shifting control strategy. The peak current in the converter is taken as an optimization target, and a soft switching condition is taken as a constraint condition. The four-switch converter is controlled in a phase-shifting mode under the condition that all the switches realize soft switching and the peak value of the series inductance current is optimized. Multi-mode smooth switching and constant frequency control are realized by the phase-shifting control of the four-switch converter. Wide voltage input and wide-range load output are realized on the basis of multi-mode smooth switching. The efficiency of the converter is improved on the basis of realizing constant frequency control, soft switching and current peak value optimization. Therefore, the application can realize wide voltage input, wide-range load output, ensure that all the switches realize soft switching and improve the efficiency of the converter.

Description

TECHNICAL FIELD

[0001] The present application relates to a phase-shift control method of four-switch buck-boost converter, belonging to the field of wide-range DC-DC converter in power electronics. BACKGROUND

[0002] The development of new energy expands the use of batteries and fuel cells, and photovoltaic power generation also needs power electronic converters that can adapt to a wide range of input voltages. Non-isolated boost and buck converters are still the mainstream converter topology. Figure 1 The four-switch buck-boost converter circuit topology targeted by the present application is shown. The four-switch buck-boost converter used for batteries and fuel cells not only needs to achieve high-efficiency power conversion, but also needs to adapt to a wide range of input voltages and a wide range of load power changes.

[0003] When the input voltage is close to the output voltage, the on-off delay or duty cycle limit of the four-switch buck-boost converter will cause a dead zone problem, which will cause poor output voltage regulation and potential instability. In order to solve the dead zone problem of the dual four-switch buck-boost converter, in 2013, the article "An nonlinear state machine for dead zone avoidance and mitigation in asynchronous noninverting buck-boost converter" was published in IEEE Trans. Power Electron, which introduced a nonlinear state machine to solve this dead zone problem, but the converter works in inductor current continuous mode, which cannot achieve circuit soft switching and has large loss.

[0004] In order to realize the zero voltage turn-on of the four-switch buck-boost converter, in 2016, the article "The zero Voltage switching(ZVS) critical conduction mode(CRM) buck Converter With tapped-inductor" was published in IEEE Trans. Power Electron, which adopts critical continuous mode(CRM) control, and the output voltage and zero voltage turn-on are jointly regulated by duty cycle and switching frequency, but the buck-boost mode has large current stress and low efficiency. At the same time, for a wide range of load changes, the switching frequency changes greatly, which has a bad influence on electromagnetic compatibility and efficiency.

[0005] In order to reduce the circuit loss of the four-switch buck-boost converter, in 2019, the article "A Constant Frequency ZVS Control System for the Four-Switch Buck-Boost DC-DC Converter With Reduced Inductor Current" was published in IEEE Trans.Power Electron, in which the constant frequency control of the four-switch buck-boost converter was realized, but the control method was based on offline operation, and the optimal control of the converter was realized through table lookup, and the mode was single, and accurate efficiency optimization control could not be realized through real-time calculation.

[0006] In order to meet the demand of wide range of power supply voltage and wide range of load power change, and at the same time reduce the circuit loss as much as possible, a phase shift control strategy is needed to realize the control method of the four-switch buck-boost converter which can realize the smooth switching between modes in the global range. SUMMARY

[0007] In order to solve the problem that the prior art method cannot meet the control of the four-switch buck-boost converter with wide voltage, wide load and low loss, the main purpose of the present application is to provide a phase shift control method of the four-switch buck-boost converter, which realizes the phase shift control of the four-switch buck-boost converter under the condition of realizing soft switching and series inductance current peak optimization of all switches, realizes multi-mode smooth switching and constant frequency control through the phase shift control of the four-switch buck-boost converter, realizes wide voltage input and wide range load output on the basis of realizing multi-mode smooth switching. On the basis of realizing constant frequency control, soft switching and current peak optimization, the efficiency of the converter is improved; therefore, the present application can realize wide voltage input, wide range load output, and at the same time ensure that all switches realize soft switching and improve the efficiency of the converter.

[0008] The purpose of the present application is realized by the following technical scheme.

[0009] The phase shift control method of the four-switch buck-boost converter disclosed by the present application is for the four-switch buck-boost converter. The primary side and the secondary side of the main circuit of the four-switch buck-boost converter are both half-bridge circuits, and the two half-bridges are connected together through a series inductance, the primary side is connected to a battery, and the secondary side can be connected to any load, and the power control is realized by controlling the phase shift angle corresponding to the voltage waveforms of the two half-bridges of the primary side and the secondary side of the converter.

[0010] The phase shift control method of the four-switch buck-boost converter disclosed by the present application comprises the following steps:

[0011] Step one: through the voltage reference V refand secondary voltage feedback V o The voltage error obtained by subtraction is outputted by the output voltage controller to control the phase shift angle Where the phase shift angle is defined as the phase difference corresponding to the neutral lines of the primary side and secondary side square waves.

[0012] Step two: define the voltage gain M = V o / V in Where V in is the input voltage, V o is the output voltage of the secondary side. Define D1 and D2 as the duty cycles of the primary side and secondary side voltage waveforms respectively. According to the value of M and the size of the phase shift angle , the working modes of the circuit are distinguished.

[0013] There are five working modes. When and M < 1, the circuit works in mode 1; when and M < 1, the circuit works in mode 2; when and M > 1, the circuit works in mode 3; when and M > 1, the circuit works in mode 4; when M = 1, the circuit works in mode 5.

[0014] Step three: taking the peak current in the converter as the optimization target and taking the soft switching of all switches as the constraint condition, control equations corresponding to the five working modes in step two are constructed respectively, and the boundary conditions of mode division are given.

[0015] For mode 1, mode 2, mode 3, mode 4 and mode 5, the boundary conditions are as follows:

[0016]

[0017] Taking the peak current in the converter as the optimization target and taking the soft switching of all switches as the constraint condition, the control equations corresponding to the five working modes are constructed according to the relationship between the phase shift angle and the duty cycles D1 and D2 as follows:

[0018] When M < 1,

[0019]

[0020]

[0021] When M > 1,

[0022]

[0023]

[0024] When M = 1,

[0025]

[0026] wherein I ZVS1 and I ZVS2 is the minimum current value for the mode 1 and mode 3 switch tubes to realize zero-voltage turn-on, I zvs0 is the given soft-switching current of the soft-switching constraint condition, L r is the series inductance value, T s is the switching period, i o is the output current, and alpha is the duty cycle coefficient under the mode 2 and mode 4, which is used to match the hardware circuit, and the theoretical value is 1, and the value in the actual circuit is less than 1.

[0027] Step four: obtaining the phase shift angle from step one The duty cycles D1 and D2 obtained in step three generate the driving signals corresponding to the primary side and secondary side switch tubes, and the signals are used to drive the four switch tubes to work, so that the phase shift control of the four switch tube step-up and step-down circuit is realized.

[0028] Step five: comparing the inductance current with the given soft-switching current I zvs0 through a current comparison circuit to generate a signal, and the soft-switching current I zvs0 in step four is controlled, so that the zero-voltage turn-on of the circuit is realized.

[0029] The converter is composed of a series inductance and a primary side half-bridge and a secondary side half-bridge;

[0030] The primary side half-bridge comprises two switch tubes Q1 and Q2, the secondary side half-bridge comprises two switch tubes Q3 and Q4, the switch tube Q1 and the switch tube Q2 form a bridge arm, the source electrode of Q1 is connected to the drain electrode of Q2, the switch tube Q3 and the switch tube Q4 form a bridge arm, the source electrode of Q3 is connected to the drain electrode of Q4, and the source electrode of the switch tube Q1 is connected to one end of the series inductance L r , and the other end of the series inductance L r is connected to the source electrode of Q3.

[0031] Advantageous effects:

[0032] 1. The phase shift control method of the four switch tube step-up and step-down converter disclosed in the application realizes the phase shift control of the four switch tube step-up and step-down converter through steps one to four under the condition that all switch tubes realize soft switching and the series inductance current peak value is optimized, realizes the multi-mode smooth switching and constant frequency control through the phase shift control of the four switch tube step-up and step-down converter, realizes the wide voltage input and wide range load output on the basis of realizing the multi-mode smooth switching, and improves the converter efficiency on the basis of realizing the constant frequency control.

[0033] 2. The phase-shift control method of the four-switch boost-buck converter disclosed in the present application, voltage setting is compared with secondary voltage, and the phase-shift angle control quantity of the half-bridge on both sides of the converter is obtained through the voltage controller The control quantity of the internal duty cycle D1 and D2 is obtained by using the relationship between the duty cycle and the phase-shift angle The driving signals of the four switches of the full-bridge on both sides are generated through the duty cycle and the phase-shift angle. The phase-shift control of the four-switch boost-buck converter is realized.

[0034] 3. The phase-shift control method of the four-switch boost-buck converter disclosed in the present application, the peak current in the converter is optimized in step three, the peak current of the four-switch boost-buck converter is optimized, and the efficiency of the converter is improved on the basis of the current peak optimization.

[0035] 4. The phase-shift control method of the four-switch boost-buck converter disclosed in the present application, the soft switching condition is used as a constraint condition in step three, and the soft switching current is controlled through an external circuit in step five, the soft switching of all switches of the four-switch boost-buck converter is realized, and the efficiency of the converter is improved on the basis of the soft switching.

[0036] 5. The phase-shift control method of the four-switch boost-buck converter disclosed in the present application, on the basis of the above-mentioned three beneficial effects, wide voltage input, wide range load output can be realized, and at the same time, all switches realize soft switching, and the efficiency of the converter is improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The four-switch boost-buck converter circuit topology schematic diagram of the present embodiment is shown;

[0038] Figure 2 The closed-loop control block diagram of the present application is shown;

[0039] Figure 3 The waveform diagram of the Mode1 internal switching of the present application is shown;

[0040] Figure 4 The waveform diagram of the Mode2 internal switching of the present application is shown;

[0041] Figure 5 The waveform diagram of the Mode3 internal switching of the present application is shown;

[0042] Figure 6 The waveform diagram of the Mode4 internal switching of the present application is shown;

[0043] Figure 7 The waveform diagram of the Mode5 internal switching of the present application is shown;

[0044] Figure 8 The driving signal generation method, wherein: Figure 8(a) is the generation logic of the drive signal, Figure 8 (b) is the generation logic of the external trigger signal;

[0045] Figure 9 The flow chart of the phase-shift control method of the four-switch boost-buck converter disclosed in the present application. DETAILED DESCRIPTION

[0046] The present application will be further described below in conjunction with the drawings and examples, and the technical problems solved by the technical solutions of the present application and the beneficial effects are also described. It should be pointed out that the described examples are only intended to facilitate the understanding of the present application and do not have any limiting effect on it.

[0047] As Figure 1 shown is a four-switch boost-buck converter circuit topology schematic diagram, the converter is composed of four switches, and both the primary side and the secondary side are composed of two switches. The primary side half-bridge includes two switches Q1 and Q2; the secondary side half-bridge includes two switches Q3 and Q4; the switch Q1 and the switch Q2 form a bridge arm, and the source of Q1 is connected to the drain of Q2; the switch Q3 and the switch Q4 form a bridge arm, and the source of Q3 is connected to the drain of Q4; one end of the series inductor L r is connected to the source of Q1, and the other end of the series inductor L r is connected to the source of Q3. The drain of Q1 is the positive electrode of the input voltage, the source of Q2 is the negative electrode of the input voltage, the drain of Q3 is the positive electrode of the output voltage, and the source of Q4 is the negative electrode of the output voltage. V in and V o are the primary side battery voltage and the secondary side output voltage respectively, and the voltage gain M of the converter is defined as V o / V in .

[0048] Q1 is turned on at the beginning of the switching period, and is turned off at D1, and the drive signal of Q2 is complementary to it and has a dead time; Q3 is turned on at , and is turned off at the time mentioned in 4, and the drive signal of Q4 is complementary to it and has a dead time;

[0049] As Figure 9 shown, the phase-shift control method based on the four-switch boost-buck converter disclosed in the present embodiment, the specific control steps are as follows;

[0050] Step one: as Figure 2 shown, the voltage error obtained by subtracting the secondary side voltage feedback V o from the voltage reference V ref is outputted by the output voltage controller, and the control amount is the phase shift angle wherein the phase shift angle is defined as the phase difference corresponding to the neutral line of the primary side and the secondary side square wave.

[0051] Step two: define voltage gain M = V o / V in where V in is the input voltage, V o is the output voltage on the secondary side. Define D1, D2 as the duty cycle of the primary and secondary voltage waveforms, respectively. According to the value of M, the size of the phase shift angle , the working mode of the circuit is distinguished.

[0052] There are five working modes in total. When and M < 1, the circuit works in mode 1; when and M < 1, the circuit works in mode 2; when and M > 1, the circuit works in mode 3; when and M > 1, the circuit works in mode 4; when M = 1, the circuit works in mode 5.

[0053] Step three: taking the peak current in the converter as the optimization target, and taking the soft switching of all switches as the constraint condition, control equations corresponding to the five working modes in step two are constructed respectively, and the boundary conditions of mode division are given.

[0054] For mode 1, mode 2, mode 3, mode 4, and mode 5, the boundary conditions are as follows:

[0055]

[0056] Taking the peak current in the converter as the optimization target, and taking the soft switching of all switches as the constraint condition, control equations corresponding to the five working modes are constructed respectively according to the relationship between the phase shift angle and the duty cycle D1, D2 as follows:

[0057] When M < 1,

[0058]

[0059]

[0060] When M > 1,

[0061]

[0062]

[0063] When M = 1,

[0064]

[0065] where I ZVS1 and I ZVS2The minimum current value for the zero-voltage turn-on of the switch tubes of mode 1 and mode 3, I zvs0 The given soft switching current for the soft switching constraint condition, L r The series inductance value, T s The switching period, i o The output current, and the duty cycle coefficient under mode 2 and mode 4, which is used to match the hardware circuit, and the theoretical value is 1, and the value in the actual circuit is less than 1.

[0066] After integration, the unified control strategy for mode 1, mode 2, mode 3, mode 4 and mode 5 is

[0067]

[0068]

[0069] Step four: the phase shift angle obtained from step one Step three obtains the duty cycles D1 and D2 to generate the corresponding driving signals of the primary side and secondary side switch tubes, which are used to drive the four switch tubes to work and realize the phase shift modulation of the four switch tube boost-buck circuit; as shown in Figure 8 (a),

[0070]

[0071] Where T d is the period count value of the counter. The falling edge of the Q2 driving signal and the rising edge of the Q1 driving signal are located at the zero moment of the switching period; CMP1 corresponds to the falling edge of the Q1 driving signal and the rising edge of the Q2 driving signal; CMP2 corresponds to the rising edge of the Q3 driving signal and the falling edge of the Q4 driving signal; and the falling edge of the Q3 driving signal and the rising edge of the Q4 driving signal are triggered to be generated through the comparison circuit.

[0072] Step five: the inductor current is compared with the given soft switching current I zvs0 through the current comparison circuit to generate a signal to control the soft switching current I zvs0 in step four, so as to realize the zero-voltage turn-on of the circuit. As shown in Figure 8 (b), when the inductor current is less than the given comparison value, a pulse signal is generated through the digital circuit to trigger the controller to reset the Q3 driving signal and set the Q4 driving signal.

[0073] Figure 3 The driving signal and the inductor current waveform corresponding to mode 1 are shown in Figure 4 The driving signal and the inductor current waveform corresponding to mode 2 are shown in Figure 5 The driving signal and the inductor current waveform corresponding to mode 3 are shown in Figure 6 The driving signal and the inductor current waveform corresponding to mode 4 are shown inFigure 7 Drive signal and inductor current waveforms corresponding to mode 5.

[0074] The above detailed description of the specific description, the purpose, technical solutions and beneficial effects of the invention are further described in detail, it should be understood that the above description is only a specific embodiment of the present application, and is not used to limit the protection scope of the present application, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A phase-shifted control method for a four-switch boost-buck converter, characterized in that: The control object is a four-switching-tube step-up / down converter; the primary side and the secondary side of the main circuit of the four-switching-tube step-up / down converter are both half-bridge circuits, two half-bridges are connected together through a series inductor, the primary side is connected with a storage battery, and the secondary side can be connected with any load; the power control is realized by controlling the phase-shifting angles corresponding to the voltage waveforms of the two half-bridges of the primary side and the secondary side of the converter; The wide-range input voltage can be adapted, the wide-range power regulation can be realized, and the low loss is achieved; The method comprises the following steps: Step one: the voltage error is obtained by subtracting the voltage reference V ref and the secondary side voltage feedback V o The output voltage controller outputs the voltage error as a phase shift angle control φ, where the phase shift angle φ is defined as the phase difference corresponding to the neutral lines of the primary side and secondary side square waves. Step two: define voltage gain M=V o / V in , define D1, D2 as the duty cycle of the primary side and secondary side voltage waveform respectively; according to the value of M and the size of the phase shift angle φ, distinguish the working mode of the circuit; In step two, There are five operating modes, when 0≤φ≤φ c And when M < 1, the circuit operates in mode 1; when φ c <φ≤φ m When M < 1, the circuit operates in mode 2; when 0 ≤ φ ≤ φ c And when M>1, the circuit operates in mode 3; when φ c <φ≤φ m When M>1, the circuit operates in mode 4; when M=1, the circuit operates in mode 5. In step three, the relationship between D1, D2 and φ is obtained by taking the peak current in the converter as the optimization target; In step three, From the relationship between the phase-shifting angle φ and D1, D2, the following equation is obtained When M < 1, when M > 1, When M = 1, where φ s = 2φ / π, I ZVS1 and I ZVS2 is the minimum current value for the mode 1 and mode 3 switch tubes to realize zero-voltage turn-on, and α is a duty ratio coefficient, which is less than 1. For mode 1, mode 2, mode 3, mode 4 and mode 5, the following equation is established ； In step four, the driving signals corresponding to the switching tubes of the primary side and the secondary side are generated by using φ obtained in step one and D1 and D2 obtained in step three, the signals are used for driving the four switching tubes to work, and the phase-shifting modulation of the four-switching-tube step-up / down converter is realized; Step five: The inductor current is compared with the given soft switching current I zvs0 by the current comparison circuit to generate a signal to control the soft switching current I zvs0 in step four to realize the zero voltage turn-on of the circuit.

2. The phase-shifted control method of the four-switch boost-buck converter according to claim 1, wherein: In step five, When the inductor current is lower than the given soft switching current I zvs0 , the drive signal is generated to make the secondary side switch Q3 off and Q4 on to control the secondary side half bridge. When the current does not reach the given soft switching current I zvs0 , the secondary side switches Q3 and Q4 are not operated.

3. The phase-shifted control method of the four-switch boost-buck converter according to claim 1, wherein: In step four, The driving signal realization method of each switching tube is Q1 is turned on at the starting moment of the switching period and is turned off at D1 moment, and the driving signal of Q2 is complementary to Q1 and has a dead time; Q3 turns on at (D1 + φ / π - D2)Ts / 2, and turns off at the time when the inductor current is lower than the given soft switching current I zvs0 Q4 turns on at (D1 + φ / π - D2)Ts / 2, and turns off at the time when the inductor current is lower than the given soft switching current I 4. The phase-shifted control method of a four-switch boost-buck converter as claimed in claim 1 or 2, characterized in that: The converter is composed of a series inductor and a primary side half-bridge and a secondary side half-bridge; The primary side half-bridge comprises two switching tubes Q1 and Q2; the secondary side half-bridge comprises two switching tubes Q3 and Q4; the switching tube Q1 and the switching tube Q2 form a bridge arm, and the source of the switching tube Q1 is connected to the drain of the switching tube Q2; the switching tube Q3 and the switching tube Q4 form a bridge arm, and the source of the switching tube Q3 is connected to the drain of the switching tube Q4; the source of the switching tube Q1 is connected to one end of a serial inductor L r , and the other end of the serial inductor L r is connected to the source of the switching tube Q3.

5. The phase-shifted control method of a four-switch boost-buck converter as claimed in claim 3, characterized by: The converter is a bidirectional topology structure, the primary side and the secondary side can be interchanged according to the requirement, and any load can be connected.

Images