CN109067178B - A control system and method for smooth switching of modes of an in-phase buck-boost converter - Google Patents

Abstract

The invention relates to a control technology of an in-phase four-tube buck-boost converter, in particular to a control system and method for smooth mode switching of the in-phase buck-boost converter. The principle of the present invention is to clamp the minimum on-time of the power transistors SC and SB of the control circuit at t _min , and set the maximum on-time of the power transistors SA and SD to t _AD0 in Buck mode and Boost mode, and can realize the above The solved power tubes SA and SD are simultaneously turned on for the control of t _AD1 , and the control circuit realizes smooth mode switching. The control method of the present invention clamps the turn-on and turn-off time of the power tube during the mode switching process, eliminates the influence of the dead time on the output voltage, reduces the ripple of the system, and improves the stability of the system; and reduces the Buck-Boost The average inductor current in the mode improves the efficiency; the control method is simple to implement and can be used for any voltage-mode controlled non-inverting four-tube Buck-Boost converter.

Description

A control system and method for smooth switching of modes of an in-phase buck-boost converter

technical field

The invention relates to a control technology of an in-phase four-tube buck-boost converter, in particular to a control system and method for smooth mode switching of the in-phase buck-boost converter.

Background technique

The non-inverting four-tube buck-boost converter can boost and buck in a timely manner under a wide input voltage with low cost and high efficiency, and is widely used in power amplifiers, photovoltaic inverters and power supply for mobile devices.

In order to convert the voltage with high efficiency, the working modes of the non-inverting four-tube buck-boost converter are divided into Buck mode, Buck-Boost mode and Boost mode. Spikes generated during small mode switching. Figure 1A is a schematic circuit diagram of a control method for mode switching in the prior art, wherein capacitors C1, C2 and C3 are off-chip capacitors, SW1 and SW2 are the voltages across the inductor L, and SA and SC are power switches tube, SB and SD are synchronous rectifier power tubes. According to the input voltage VIN and output current requirements, the control circuit controls the on and off of the on-chip power transistor to adjust the output voltage VOUT. In the control circuit, the output sampling voltage V _S and the reference voltage VREF are used as the input terminals of the error amplifier Amp. The output signal of the error amplifier is VC, and VC is compared with the overlapping ramp signals VBoost and VBuck through the comparator COM1. The period of the ramp signals VBoost and VBuck is T _s , and the output signal controls the power transistors SA, SB, SC and SD through the driver circuit Driver. on and off.

As shown in Figure 1B, V _max and _VL are the maximum and minimum values of VBoost, and V _H and V _min are the maximum and minimum values of VBuck. When the system works in Buck mode, the error signal VC is only compared with VBUCK; when the system works in Boost mode, VC is only compared with VBoost; when the system works in Buck-Boost mode, VC is compared with VBoost and VBuck at the same time. When the driving signal VO1 is high level/low level, the power tube SA is turned on/off, and the power tube SB is turned off/on at the same time; when the driving signal VO2 is high level/low level, the power tube SD is turned on /Turn off, the power tube SC is turned off/on.

However, due to the existence of the dead time of the power tube, there are still voltage and current jumps during the switching between Buck mode and Boost mode in the same transition Buck-Boost mode, which affects the stability of the system. For example, when the system just enters Buck-Boost mode from Buck mode, since the low level duration of the signal VO2 controlling the power tube SD is lower than the dead time, the parasitic capacitance of the power tube is not fully charged and discharged, resulting in the power tube SC being too late to turn on. , the power tube SD has no time to turn off, the DC voltage conversion ratio remains unchanged, therefore, the output voltage decreases with the input voltage; as the input voltage continues to decrease, when the low level duration of VO2 increases to be higher than the dead time, When the charge and discharge of the parasitic capacitance of the power tube exceeds the threshold, the power tube SC and SD switch normally, and the DC voltage conversion ratio increases, resulting in a jump in the output voltage. The same goes for switching from Buck-Boost mode to Boost mode. Therefore, the influence of the dead time of the power tube on the output voltage must be eliminated to improve the stability of the output voltage during the mode switching process.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a control system and method for smooth mode switching of an in-phase buck-boost converter, which can eliminate the influence of power tube dead time on the output voltage during the mode switching process of the system, and realize smooth mode switching.

The above-mentioned technical problems of the present invention are mainly solved by the following technical solutions:

A control system for smooth switching of modes of an in-phase buck-boost converter is characterized in that a clamping component is added to the control circuit of the Buck-Boost converter, and the clamping component can convert the in-phase four in the Buck-Boost converter. The minimum conduction time of the power tubes SC and SB of the tube assembly is clamped at t _min , and the maximum conduction time of the power tubes SA and SD in Buck mode and Boost mode is set to t _AD0 , where t _min and t _AD0 are Set value, and define that the power tube SA and the power tube SC are turned on at the same time, and the working time is t _AC ; the power tube SA and the power tube SD are turned on at the same time, and the working time is t _AD ; the power tube SB and the power tube SD are turned on at the same time. The time is t _BD ; when the system works in Buck mode, t _AD +t _BD =T _s , t _AC =0; when the system works in Boost mode, t _AD +t _BD =T _S ,t _AC +t _AD =T _s , t _BD =0, t _AD0 =aT _s ; t _min =bT _s .

In the above-mentioned control system for smooth mode switching of a non-inverting buck-boost converter, the clamping component includes a clamping module and a pulse generating module that are connected in sequence, and the clamping component input is connected to the comparator of the Buck-Boost converter Component, the output is connected to the driver of the in-phase four-tube in the Buck-Boost converter.

In the above-mentioned control system for smooth switching of non-inverting buck-boost converter modes, the comparator component includes a comparator Com1, a comparator Com2, and a comparator Com3; the output sampling voltage V _S of the sampling resistor and the reference voltage VREF, As the input end of the error amplifier Amp; the output signal of the error amplifier is the error signal VC, the comparator Com1 compares the V _BUCK and V _BOOST sawtooth waves with the error signal VC, and outputs the control signals VO1 and VO2 to the clamping component Clamp; The devices Com2 and Com3 compare the signal V _H and the signal _VL with the error signal VC respectively to generate the control signal CON and output it to the clamping component Clamp, where V _H is the peak value of the V _Buck sawtooth wave, and V _L is the V _Boost sawtooth wave valley value.

In the above-mentioned control system for smooth mode switching of in-phase buck-boost converters, the in-phase four-tube component includes: a power switch tube SA, a power switch tube SC, a synchronous rectification power tube SB and a synchronous rectification power tube SD. , and connected to the drive module at the same time; one end of the inductor L is connected to the power switch SA and the synchronous rectification power tube SB at the same time, and the other end is connected to the power switch SC and the synchronous rectification power tube SD at the same time; the output of the synchronous rectification power tube SD is connected to the load. , the adjusted output voltage of the in-phase four-tube assembly is VOUT; the off-chip capacitor C1 is connected to the input of the in-phase four-tube assembly and grounded; the off-chip capacitor C2 is connected to the output of the in-phase four-tube assembly and grounded; the off-chip capacitor C3 is connected to the output of the error amplifier Amp and ground.

In the above-mentioned control system for smooth switching of in-phase buck-boost converter modes, t _AD0 =0.85T _s ; t _min =0.05T _s .

A control method for smooth switching of in-phase buck-boost converter modes, characterized in that, in a transitional Buck-Boost mode, in one switching cycle, the power transistors SA and SD are initially turned on, and then the power transistors SA and SC are turned on. turn on, and finally the power tubes SB and SD are turned on; and the minimum time that the power tubes SA and SC of the in-phase four-tube assembly in the Buck-Boost converter can be turned on at the same time in one switching cycle is clamped at t _min , The minimum time for the simultaneous conduction of power tubes SB and SD is clamped at t _min , and the maximum time for the simultaneous conduction of power tubes SA and SD in Buck mode and Boost mode is set to t _AD0 , where t _min and t _AD0 are The set value, and define that the power tube SA and the power tube SC are turned on at the same time and the working time is t _AC ; the power tube SA and the power tube SD are turned on at the same time The working time is t _AD ; the time when the power tube SB and the power tube SD are turned on at the same time is t _BD ; when the system works in Buck mode, t _AD +t _BD =T _s , t _AC =0; when the system works in Boost mode, t _AD +t _BD =T _s , t _AC +t _AD =T _S , t _BD =0, t _AD0 =aT _s ; t _min =bT _s .

In the above-mentioned control method for smooth switching of the in-phase buck-boost converter mode, the power tube SA and the power tube SC are turned on at the same time and the working time is t _AC ; the power tube SA and the power tube SD are turned on at the same time The working time is t _AD ; The time when the power tube SB and the power tube SD are turned on at the same time is t _BD ; when the system works in the Buck mode, t _AD +t _BD =T _s , t _AC =0, and there are

Among them, M _VBuck represents the DC voltage conversion ratio when the Buck mode is about to switch to the Buck-Boost mode, M _VBB1 represents the DC voltage conversion ratio when the Buck mode is just switched to the Buck-Boost mode, and M _VBB2 represents the DC voltage when it is about to switch to the Boost mode. Conversion ratio, M _VBoost represents the DC voltage conversion ratio when just switching to Boost mode; t _AD0 is the set maximum conduction time of power tubes SA and SD in Buck mode and Boost mode; if the mode is smoothly switched, the formula (3 ) is equal to Equation (4), Equation 5 and Equation 6 are equal; if the above two equations are equal respectively, it can be determined that at the moment of switching from Buck mode or Boost mode to Buck-Boost mode, the power tubes SA and SD are turned on at the same time. The time interval is t _tD1 .

In the above-mentioned control method for smooth mode switching of a non-inverting buck-boost converter, as the input voltage decreases, the working mode of the converter changes from Buck mode to Buck-Boost mode and then to Boost mode, specifically including:

Step 1: When the error signal V _C is lower than V _L , the system works in Buck mode, and the power tubes SA and SB control the voltage conversion ratio, where V _L is the valley value of the V _BOOST sawtooth wave;

Step 2: When the error signal _VC rises slowly and is higher than _VL , the minimum time t _min for the simultaneous conduction of the clamp power tubes SA and SC, the simultaneous conduction time of the power tubes SA and SD drops from t _AD0 to t instantaneously _AD1 . The time that the power transistors SB and SD are turned on at the same time becomes smaller as the _VC slowly rises, and the time that the power transistors SA and SD are simultaneously turned on becomes larger as the _VC slowly rises, until t _AD rises from t _AD1 to t _AD0 ;

Step 3: The error signal V _C continues to rise. At this time, the time when the power tubes SA and SD are turned on at the same time is always t _AD0 . The time when the power tubes SA and SC are turned on at the same time is no longer clamped, and increases with the rise of V _C. The time during which the power tubes SB and SD are turned on at the same time decreases with the rise of V _C until t _BD decreases to t _min ;

Step 4: When the error signal V _C continues to rise and is lower than V _H , the minimum time t _min for the simultaneous conduction of the clamping power tubes SB and SD; the time for the simultaneous conduction of the power tubes SA and SC increases as V _C slowly rises. becomes larger, the time that the power tubes SA and SD are turned on at the same time decreases with the slow rise of V _C until t _AD decreases from t _AD0 to t _AD1 , and V _C is equal to V _H at the same time; among them, V _H is V _BUCK sawtooth the peak of the wave;

Step 5: When the error signal V _C continues to rise and is higher than V _H , the system works in the Boost working mode, and no longer clamps the minimum time for the power tubes SB and SD to be turned on at the same time; the power tubes SA and SD are turned on at the same time. The time rises instantaneously from t _AD1 to t _AD0 , and the power transistors SC and SD control the voltage conversion ratio.

In the above-mentioned control method for smooth mode switching of the in-phase buck-boost converter, t _AD0 =0.85T _s ; t _min =0.05t _s .

Therefore, the present invention has the following advantages: the control method of the present invention clamps the turn-on and turn-off time of the power tube during the mode switching process, eliminates the influence of the dead time on the output voltage, reduces the ripple of the system, and improves the stability of the system The average inductor current in Buck-Boost mode is reduced, and the efficiency is improved; the control method is simple to implement and can be used in any voltage-mode controlled non-inverting four-tube Buck-Boost converter.

Description of drawings

Fig. 1A The control method of the traditional in-phase four-tube Buck-Boost converter.

FIG. 1B is a schematic waveform diagram of a control method of a conventional in-phase four-tube Buck-Boost converter.

Figure 2. The relationship between the error output voltage of the in-phase four-tube Buck-Boost converter and the DC conversion ratio.

Figure 3. Key control blocks to eliminate the effects of dead time.

Figure 4A shows the key waveforms of the proposed control method switching from Buck mode to Buck-Boost mode.

Figure 4B shows the key waveforms of the proposed control method switching from Buck-Boost mode to Boost mode.

Fig. 5 takes the LED constant current drive as an example, the system architecture diagram of the proposed control method.

Detailed ways

The technical solutions of the present invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

Example:

The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to such embodiments. The present invention covers any alternatives, modifications, equivalent methods, and arrangements made within the spirit and scope of the present invention. In order to provide the public with a thorough understanding of the present invention, specific details are described in the following preferred embodiments of the present invention, and those skilled in the art can fully understand the present invention without the description of these details.

The input voltage of the lithium battery will slowly decrease with time, generally from 4.7V to 2.7V. Since the duty cycle of the four power switches will not change suddenly, when the input voltage decreases, the output voltage will also decrease, the error signal VC will increase, and then the duty cycle will be adjusted to stabilize the output voltage. Under stable operation, when the input voltage has a small change ΔVIN, the output voltage change ΔVO is approximately linear with the input voltage small change ΔVIN, and the error signal change ΔVC and the output voltage change ΔVO are also approximately linear changes. Therefore, as shown in Figure 2, during the mode switching process of the converter, if the _voltage conversion ratio MV at the two critical points A and B is smooth and continuous, it means that the converter has achieved smooth mode switching.

As shown in Figure 1A, according to the volt-second balance and charge conservation, the DC characteristics of the in-phase four-tube Buck-Boost converter can be obtained, as shown in equations (1) and (2):

Among them, _IL is the average current flowing through the inductor, and _IO is the load current. The Buck-Boost mode is divided into three working states, that is, the power transistors SA and SC are turned on at the same time, and the working time is t _AC ; the power transistors SA and SD are turned on at the same time, and the working time is t _AD ; The time during which the power tubes SD are simultaneously turned on is t _BD . When the system works in Buck mode, t _AD +t _BD =T _s ,t _AC =0; when the system works in Boost mode, t _AD +t _BD =T _s ,t _AC +t _AD =T _s ,t _BD =0. When the load is constant, if t _AD + t _BD is much larger than t _AC , the average inductor current _IL can be reduced.

As shown in Fig. 2, due to the existence of dead time, at the two critical points A and B, it is difficult to determine the exact DC conversion _voltage ratio MV, resulting in discontinuous curve of the DC conversion _voltage ratio MV with respect to the error signal _VC .

The present invention ensures that MV is continuous and smooth by clamping the minimum on-time _{t min} of the power tubes SC and SB. Among them, the expressions of MV in the left neighborhood of point A and the right neighborhood of point A are (3)(4); the expressions of _MV in the left _neighborhood of point B and the right neighborhood of point B are (5)(6 ):

Among them, M _VBuck represents the DC voltage conversion ratio of Buck mode to be switched to Buck-Boost mode, M _VBB1 represents the DC voltage conversion ratio of just switching to Buck-Boost mode, M _VBB2 represents the DC voltage conversion ratio to be switched to Boost mode, M _VBoost represents the DC voltage conversion ratio just to switch to Boost mode. t _AD0 is the maximum on-time of the set power tubes SA and SD in Buck mode and Boost mode. If the mode is switched smoothly, equations (3) and (4) are equal, and equations (5) and (6) are equal. If the above two equations are equal respectively, then at the moment of switching from Buck mode or Boost mode to Buck-Boost mode, the time interval t _AD1 during which the power transistors SA and SD are turned on at the same time can be determined.

That is to say, as long as the control circuit can clamp the minimum on-time of power transistors SC and SB to t _min , set the maximum on-time of power transistors SA and SD to t _AD0 in Buck mode and Boost mode, and can To realize the control that the power transistors SA and SD solved above are simultaneously turned on for t _AD1 , the control circuit realizes smooth mode switching.

The following are specific examples. In order to provide the public with a thorough understanding of the present invention, the preferred embodiments of the present invention describe specific details, and those skilled in the art can fully understand the present invention without the description of these details.

As shown in Figure 3, VREF is the reference voltage, V _S is the output current sampling signal, the comparator Com1 compares the V _BUCK and V _BOOST sawtooth waves with the error signal VC, and outputs the control signals VO1 and VO2. The comparators Com2 and Com3 use V _H and _VL respectively to compare with the error signal VC, and generate the control signal CON to determine the operating mode. When CON is high level, the system works in Buck-Boost mode, and the pulse generating module Pulse and the clamping module Clamp start to work. VCL1 and VCL2 are clamping signals, and the low-level pulse width is clamped to t _min . The output signals of the clamp module Clamp are VAB and VCD. When the driving signal VAB is high/low, the power tube SA is turned on/off, and the power tube SB is turned off/on; when the driving signal VCD is high When the level/low level, the power tube SD is turned on/off, and the power tube SC is turned off/on.

Referring to Figure 4A, the converter switches from Buck mode to

The working process of Buck-Boost mode. When the error signal VC is higher than _VL , CON is a high level to start the pulse generator Pulse and the clamping circuit Clamp.

At the beginning of the converter switching from Buck mode to Buck-Boost mode, the falling edge of VCL1 is generated with a delay of T _s -t _min from the time when the rising slopes of VC and VBoost cross. At this time, the duration of VC higher than VBoost is less than t _min , clamps Vo2 high. As the error signal VC continues to rise, when the falling edge of VCL1 coincides with the falling edge of VBoost within one cycle, the falling edge of VCL1 is determined by the falling edge of VBOOST; at the same time, when VC is higher than VBoost for a duration greater than t _min , VO2 is no longer clamped, and the high-low level conversion is performed as shown in Figure 4A, that is, when VC is higher than VBoost, it is a low level, and vice versa. VCL1 and VO2 get VCD signal through logic AND circuit.

In the initial stage of the converter switching from Buck mode to Buck-Boost mode, the time interval between the crossing time of the rising slope of the error signal VC and VBoost and the crossing time of the falling slope is recorded as t ₁ (t). The time start delay t ₂ (t)=(T _s -t _AD0 )-t ₁ (t) generates a falling edge of VCL2. As the error signal VC continues to rise, when the rising edge of VCL2 coincides with the falling edge of VBuck in one cycle, the rising edge of VCL2 is determined by the falling edge of VBuck. VO1 performs high-low level conversion as shown in FIG. 4A, that is, when VC is higher than VBuck, it is high level, and vice versa. VCL2 and VO1 get the VAB signal through the logic AND circuit.

Referring to FIG. 4B , the working process of switching from the Buck-Boost mode to the Boost mode will be described. In the early stage of mode switching, VO1 performs high-low level conversion as shown in Figure 4B, that is, when VC is higher than VBuck, it is high level, otherwise it is low level; as the error signal VC continues to rise, when a switching cycle, VC When the duration below VBuck is less than _tmin , then VO1 is forced high. VCL2 is switched as shown in FIG. 4B , that is, the falling edge of VCL2 is generated when the error signal VC and the rising slope of VBuck cross, and switches to a high level after a fixed time of t _min . VCL2 and VO1 get the VAB signal through the logic AND circuit.

The time interval between the crossing of the rising slopes of the error signals VC and VBoost and the falling edge of VBuck is recorded as t ₃ (t), and the falling edge of VCL1 is generated with a delay of t _AD0 -t ₃ (t) from the falling edge of VBuck. At the same time, VO2 performs a high-low level conversion as shown in FIG. 4B , that is, when VC is higher than VBoost, it is a low level, and vice versa. VCL1 and VO2 get VCD signal through logic AND circuit.

When the error signal VC is greater than or equal to V _H , the control signal CON is at a low level, and the pulse generator Pulse and the clamping circuit Clamp are turned off; the converter enters the Boost working mode, and the transition working mode ends.

Referring to Figure 5, the dashed block diagram in the system architecture is the designed clamping circuit to ensure that the system can switch modes smoothly.

The foregoing has shown and described the basic principles and main features of the present invention and the advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments, and the descriptions in the above-mentioned embodiments and the description are only to illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have Various changes and modifications fall within the scope of the claimed invention. The claimed scope of the present invention is defined by the appended claims and their equivalents.

The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which the present invention pertains can make various modifications or additions to the described specific embodiments or substitute in similar manners, but will not deviate from the spirit of the present invention or go beyond the definitions of the appended claims range.

Claims (8)

1. A control system for smooth switching of in-phase buck-boost converter modes, characterized in that a clamping component is added in the control circuit of Buck-Boost conversion, and the clamping component can The minimum on-time of the power transistors SC and SB of the in-phase four-tube assembly is clamped at t _min , and the maximum on-time of the power transistors SA and SD in Buck mode and Boost mode is set to t _AD0 , where t _min and t _AD0 is the set value, and it is defined that the power tube SA and the power tube SC are turned on at the same time, and the working time is t _AC ; the power tube SA and the power tube SD are turned on at the same time, and the working time is t _AD ; the power tube SB and the power tube SD are at the same time. The turn-on time is t _BD ; when the system works in Buck mode, t _AD +t _BD =T _s , t _AC =0; when the system works in Boost mode, t _AC +t _AD =T _s , t _BD = 0, t _AD0 =aT _S ; t _min =bT _s , the input of the clamping component is connected to the comparator component of the Buck-Boost converter, and the output is connected to the driver of the in-phase four transistors in the Buck-Boost converter; the comparator component Including the comparator Com1, the comparator Com2, and the comparator Com3; the output sampling voltage V _S and the reference voltage VREF of the sampling resistor are used as the input terminals of the error amplifier Amp; the output signal of the error amplifier is the error signal VC, and the comparator Com1 converts V The sawtooth waves of _BUCK and V _BOOST are compared with the error signal VC, and the control signals VO1 and VO2 are output to the clamping component Clamp; the comparators Com2 and Com3 compare the error signal VC with the signal V _H and the signal _VL respectively, and generate the control signal CON , and output to the clamping component Clamp, where V _H is the peak value of the V _Buck sawtooth wave, and _VL is the valley value of the V _Boost sawtooth wave. 2 . The control system for smooth mode switching of an in-phase buck-boost converter according to claim 1 , wherein the clamp assembly comprises a clamp module and a pulse generation module connected in sequence. 3 . 3. The control system for smooth mode switching of an in-phase buck-boost converter according to claim 1, wherein the in-phase four-tube assembly comprises: power switch tube SA, power switch tube SC, synchronous rectification power tube SB and The in-phase four tubes composed of synchronous rectification power tubes SD are connected to the drive module at the same time; one end of the inductor L is connected to the power switch SA and the synchronous rectification power tube SB at the same time, and the other end is connected to the power switch SC and the synchronous rectification power tube SD at the same time. ; The SD output of the synchronous rectifier power tube is connected to the load, and the regulated output voltage of the in-phase four-tube assembly is VOUT; the off-chip capacitor C1 is connected to the input of the in-phase four-tube assembly and grounded; the off-chip capacitor C2 is connected to the output of the in-phase four-tube assembly and grounded; The off-chip capacitor C3 is connected to the output of the error amplifier Amp and grounded. 4 . The control system for smooth mode switching of in-phase buck-boost converters according to claim 1 , wherein t _AD0 =0.85T _s ; t _min =0.05T _s . 5 . 5. A control method for smooth switching of in-phase buck-boost converter modes, characterized in that, in the transitional Buck-Boost mode, in one switching cycle, the power transistor SA and SD are turned on at the beginning, and then the power transistor SA is turned on. And SC is turned on, and finally the power tubes SB and SD are turned on, and the minimum time that the power tubes SA and SC of the in-phase four-tube assembly in the Buck-Boost converter can be turned on at the same time in one switching cycle is clamped at t _min . , the minimum time for the simultaneous conduction of power transistors SB and SD is clamped at t _min , and the maximum time for the simultaneous conduction of power transistors SA and SD in Buck mode and Boost mode is set to t _AD0 , where t _min and t _AD0 It is a set value, and it is defined that the working time of the power tube SA and the power tube SC is turned on at the same time as t _AC ; the power tube SA and the power tube SD are turned on at the same time The working time is t _AD ; the power tube SB and the power tube SD are turned on at the same time. The time is t _BD ; when the system works in Buck mode, t _AD +t _BD =T _s , t _AC =0; when the system works in Boost mode, t _AC +t _AD =T _s , t _BD =0, t _AD0 = aT _s ; t _min =bT _s . 6. the control method of a kind of in-phase buck-boost converter mode smooth switching according to claim 5, it is characterized in that, power tube SA and power tube SC are turned on and work time is t _AC at the same time; Power tube SA and power tube SD is turned on at the same time and the working time is t _AD ; the time when the power tube SB and the power tube SD are turned on at the same time is t _BD ; when the system works in the Buck mode, t _AD +t _BD =T _s , t _AC =0, and there are

Among them, M _VBuck represents the DC voltage conversion ratio when the Buck mode is about to switch to the Buck-Boost mode, M _VBB1 represents the DC voltage conversion ratio when the Buck mode is just switched to the Buck-Boost mode, and M _VBB2 represents the DC voltage when it is about to switch to the Boost mode. Conversion ratio, M _VBoost represents the DC voltage conversion ratio when just switching to Boost mode; t _AD0 is the set maximum conduction time of power tubes SA and SD in Buck mode and Boost mode; if the mode is smoothly switched, let the formula ( 3) Equation (4) is equal, Equation 5 and Equation 6 are equal, it can be determined that at the moment of switching from Buck mode or Boost mode to Buck-Boost mode, the time interval during which the power tubes SA and SD are simultaneously turned on is t _AD1 . 7 . The control method for smooth switching of a non-inverting buck-boost converter mode according to claim 6 , wherein, as the input voltage decreases, the working mode of the converter changes from Buck mode to Buck-Boost mode to Boost again. 8 . mode, including: Step 1: When the error signal V _C is lower than V _L , the system works in Buck mode, and the power tubes SA and SB control the voltage conversion ratio, where V _L is the valley value of the V _BOOST sawtooth wave; Step 2: When the error signal _VC rises slowly and is higher than _VL , the minimum time t _min for the simultaneous conduction of the clamp power tubes SA and SC, the simultaneous conduction time of the power tubes SA and SD drops from t _AD0 to t instantaneously _AD1 . The time that the power transistors SB and SD are turned on at the same time becomes smaller as the _VC slowly rises, and the time that the power transistors SA and SD are simultaneously turned on becomes larger as the _VC slowly rises, until t _AD rises from t _AD1 to t _AD0 ; Step 3: The error signal V _C continues to rise. At this time, the time when the power tubes SA and SD are turned on at the same time is always t _AD0 . The time when the power tubes SA and SC are turned on at the same time is no longer clamped, and increases with the rise of V _C. The time during which the power tubes SB and SD are turned on at the same time decreases with the rise of V _C until t _BD decreases to t _min ; Step 4: When the error signal V _C continues to rise and is lower than V _H , the minimum time t _min for the simultaneous conduction of the clamping power tubes SB and SD; the time for the simultaneous conduction of the power tubes SA and SC increases as V _C slowly rises. becomes larger, the time that the power tubes SA and SD are turned on at the same time decreases with the slow rise of V _C until t _AD decreases from t _AD0 to t _AD1 , and V _C is equal to V _H at the same time; among them, V _H is V _BUCK sawtooth the peak of the wave; Step 5: When the error signal V _C continues to rise and is higher than V _H , the system works in the Boost working mode, and no longer clamps the minimum time for the power tubes SB and SD to be turned on at the same time; the power tubes SA and SD are turned on at the same time. The time rises instantaneously from t _AD1 to t _AD0 , and the power transistors SC and SD control the voltage conversion ratio. 8 . The control method for smooth mode switching of an in-phase buck-boost converter according to claim 5 , wherein t _AD0 =0.85T _s ; t _min =0.05T _s . 9 .

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