Method for switching double-tube Buck-Boost circuit mode

Abstract

The invention discloses a method for switching a double-tube Buck-Boost circuit mode, and relates to the field of circuit switching. In order to solve the problem that an existing Buck-Boost circuit is complex in mode switching mode, the output voltage of an IGBT switching tube S1 and the output voltage of an IGBT switching tube S2 are collected, and the duty ratio dbuck of the IGBT switching tube S1 and the duty ratio dboost of the IGBT switching tube S2 are obtained respectively; and judging whether 1-dboost-dbuck is less than 0 or not, if so, enabling the duty ratio dbuck of the IGBT switch tube S1 to be equal to 1, and adjusting the duty ratio dboost of the IGBT switch tube S2 according to the voltage reference value and the output voltage of the IGBT switch tube S2, and at the moment, the IGBT switch tube S1 is in a boost mode, and if not, enabling the duty ratio dboost of the IGBT switch tube S2 to be equal to 0, and adjusting the duty ratio dbuck of the IGBT switch tube S1 according to the voltage reference value and the output voltage of the IGBT switch tube S1, and at the moment, the IGBT switch tube S1 is in a buck mode. The invention is used for smoothly realizing buck-boost switching.

Description

Technical Field

[0001] The invention relates to the field of circuit switching and belongs to circuit mode switching technology. Background Art

[0002] Since the dual-tube Buck-Boost circuit has a simple working principle and can realize the buck-boost function, it can be applied to many wide voltage input and output range controls. However, since the dual-tube Buck-Boost circuit has two degrees of freedom, its control strategies are diverse, and the output characteristics of different modes are different, resulting in different output efficiencies of the circuit. In order to realize the buck-boost function and improve the circuit efficiency at the same time, Buck-Boost mode switching is adopted, which can effectively reduce the large stress of the inductor current, reduce circuit damage, and reduce the requirements for power switching devices. However, how to achieve mode prediction and smooth switching is the difficulty in realizing mode switching, so this has also become a hot research issue. At present, there are two main ways to realize mode switching. One is to judge the mode of the circuit according to the input and output voltage, but this method is complex to implement and it is not easy to realize smooth mode switching. The other is to use a dual modulation wave single carrier or a single modulation wave dual carrier. This method can indeed realize smooth mode switching, but in order to improve the waveform quality, it is often necessary to use a dual closed loop or input voltage feedforward control strategy, which is more complicated to implement, especially in digital circuits. Therefore. It is necessary to find a simple, efficient and easy-to-implement mode smooth switching strategy. Summary of the invention

[0003] The purpose of the present invention is to solve the problem of the complexity of the existing Buck-Boost circuit mode switching method, and propose a method for switching the dual-tube Buck-Boost circuit mode.

[0004] A method for switching a dual-tube Buck-Boost circuit mode, wherein the dual-tube Buck-Boost circuit includes an IGBT switch tube S1-S2, an inductor I L , diode D1-D2, resistor R, electrolytic capacitor C and DC power supply u dc ;

[0005] DC power supply dc The positive electrode is connected to the drain of IGBT switch tube S1, and the DC power supply u dc The cathode of the diode D1 is connected to the anode of the diode D1, the source of the IGBT switch tube S2, the cathode of the electrolytic capacitor C and one end of the resistor R; the cathode of the diode D1 is connected to the source of the IGBT switch tube S1 and the inductor I L One end of the inductor I LThe other end of the diode D2 is connected to the anode of the diode D2 and the drain of the IGBT switch tube S2 at the same time, and the cathode of the diode D2 is connected to the positive electrode of the electrolytic capacitor C and the other end of the resistor R at the same time;

[0006] The method includes the following:

[0007] Step 1: Collect the output voltage of IGBT switch tube S1 and the output voltage of IGBT switch tube S2, and obtain the duty cycle d of IGBT switch tube S1 respectively. buck and the duty cycle d of the IGBT switch tube S2 boost ;

[0008] Step 2: Determine whether it is 1-d boost -d buck <0, if yes, go to step 3, if no, go to step 4;

[0009] Step 3: Switch to boost mode, specifically: set the duty cycle of IGBT switch S1 to d buck =1, and adjust the duty cycle d of the IGBT switch tube S2 according to the voltage reference value and the output voltage of the IGBT switch tube S2 boost ;

[0010] Step 4: Switch to step-down mode, specifically: set the duty cycle d of the IGBT switch tube S2 to boost =0, and adjust the duty cycle d of the IGBT switch tube S1 according to the voltage reference value and the output voltage of the IGBT switch tube S1 buck .

[0011] Preferably, in step 1, a voltage sensor is used to collect the output voltage of the IGBT switch tube S1 and the output voltage of the IGBT switch tube S2.

[0012] Preferably, step 3 also includes: a No. 1 PI controller generates a PWM control signal according to the difference between the voltage reference value and the output voltage of the IGBT switch tube S2, and sends it to the No. 1 driver, and the No. 1 driver adjusts the duty cycle of the IGBT switch tube S2 according to the PWM control signal.

[0013] Preferably, step 4 also includes: the second PI controller generates a PWM control signal according to the difference between the voltage reference value and the output voltage of the IGBT switch tube S1, and sends it to the second driver, and the second driver adjusts the duty cycle of the IGBT switch tube S1 according to the PWM control signal.

[0014] The beneficial effects of the present invention are:

[0015] The present invention mainly designs a new control strategy for a dual-tube Buck-Boost circuit, so that the circuit has the function of stepping up and down, and can realize advance prediction control and thus realize smooth mode switching. At the same time, different control parameters are used for different modes to achieve better output smoothness, and the switching method of the present invention is simple.

[0016] The present invention adopts two degrees of freedom control. When controlling the boost, one degree of freedom controls the duty cycle d of S1. buck =1, another degree of freedom controls the duty cycle of S2 d boost , when controlling the voltage drop, one degree of freedom controls d boost = 0, another degree of freedom controls the duty cycle of S1 d buck ,Due to the advance prediction of the mode, different modes can use different adjustment parameters to achieve the optimal output performance and minimize the circuit power loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is the schematic diagram of the dual-tube Buck-Boost circuit;

[0018] Figure 2 A control block diagram of a method for switching a dual-tube Buck-Boost circuit mode. DETAILED DESCRIPTION

[0019] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0021] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0022] Example:

[0023] Combination Figure 1 and Figure 2 The present embodiment is a method for switching a dual-tube Buck-Boost circuit mode, wherein the dual-tube Buck-Boost circuit includes an IGBT switch tube S1-S2, an inductor I L , diode D1-D2, resistor R, electrolytic capacitor C and DC power supply u dc ;

[0024] DC power supply dc The positive electrode is connected to the drain of IGBT switch tube S1, and the DC power supply u dc The cathode of the diode D1 is connected to the anode of the diode D1, the source of the IGBT switch tube S2, the cathode of the electrolytic capacitor C and one end of the resistor R; the cathode of the diode D1 is connected to the source of the IGBT switch tube S1 and the inductor I L One end of the inductor I L The other end of the diode D2 is connected to the anode of the diode D2 and the drain of the IGBT switch tube S2 at the same time, and the cathode of the diode D2 is connected to the positive electrode of the electrolytic capacitor C and the other end of the resistor R at the same time;

[0025] The method comprises the following:

[0026] Step 1: Collect the output voltage of IGBT switch tube S1 and the output voltage of IGBT switch tube S2, and obtain the duty cycle d of IGBT switch tube S1 respectively. buck and the duty cycle d of the IGBT switch tube S2 boost ;

[0027] Step 2: Determine whether it is 1-d boost -d buck <0, if yes, go to step 3, if no, go to step 4;

[0028] Step 3: Switch to boost mode, specifically: set the duty cycle of IGBT switch S1 to d buck =1, and adjust the duty cycle d of the IGBT switch tube S2 according to the voltage reference value and the output voltage of the IGBT switch tube S2 boost ;

[0029] Step 4: Switch to step-down mode, specifically: set the duty cycle d of the IGBT switch tube S2 to boost =0, and adjust the duty cycle d of the IGBT switch tube S1 according to the voltage reference value and the output voltage of the IGBT switch tube S1 buck .

[0030] Specifically, a control program is formed according to the technical solution of this embodiment. First, the duty cycle d of the IGBT switch tube S1 is easily obtained in the digital circuit. buck and the duty cycle d of the IGBT switch tube S2 boost According to the formula M = 1-d boost -d buck Perform advance predictive control. When M<0, d buck =1, the duty cycle d is adjusted by feedback from the voltage reference value and the output voltage of the IGBT switch tube S2 boost , this is the boost mode; when M≥0, d boost=0, the duty cycle d is adjusted by feedback from the voltage reference value and the output voltage of the IGBT switch tube S1 buck , this is the buck mode; in the boost mode, one set of adjustment parameters is used, and in the buck mode, another set of adjustment parameters is used to achieve the optimal output waveform. This control logic only needs to collect the output voltage, and only needs a voltage sensor. The logic can be realized by a programmable control chip such as a single-chip microcomputer. It is easy to obtain the duty cycle feedback value in a control chip such as a single-chip microcomputer, so no additional duty cycle collection circuit is required. Figure 1 The schematic diagram of the dual-tube Buck-Boost circuit is given in the attached Figure 2 Give the control block diagram.

[0031] The elements used for collecting voltage are further defined below: In step 1, a voltage sensor is used to collect the output voltage of the IGBT switch tube S1 and the output voltage of the IGBT switch tube S2.

[0032] Step 3 is further defined below:

[0033] Step 3 also includes: the first PI controller generates a PWM control signal according to the difference between the voltage reference value and the output voltage of the IGBT switch tube S2, and sends it to the first driver, and the first driver adjusts the duty cycle of the IGBT switch tube S2 according to the PWM control signal.

[0034] Step 4 is further defined below:

[0035] Step 4 also includes: the second PI controller generates a PWM control signal according to the difference between the voltage reference value and the output voltage of the IGBT switch tube S1, and sends it to the second driver, and the second driver adjusts the duty cycle of the IGBT switch tube S1 according to the PWM control signal.

[0036] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in other described embodiments.

Claims

1. A method for switching a dual-tube Buck-Boost circuit mode, wherein the dual-tube Buck-Boost circuit includes an IGBT switch tube S1-S2, an inductor I L , diode D1-D2, resistor R, electrolytic capacitor C and DC power supply u dc ; DC power supply dc The positive electrode is connected to the drain of IGBT switch tube S1, and the DC power supply u dc The cathode of the diode D1 is connected to the anode of the diode D1, the source of the IGBT switch tube S2, the cathode of the electrolytic capacitor C and one end of the resistor R; the cathode of the diode D1 is connected to the source of the IGBT switch tube S1 and the inductor I L One end of the inductor I L The other end of the diode D2 is connected to the anode of the diode D2 and the drain of the IGBT switch tube S2 at the same time, and the cathode of the diode D2 is connected to the positive electrode of the electrolytic capacitor C and the other end of the resistor R at the same time; It is characterized in that The method comprises the following: Step 1: Collect the output voltage of IGBT switch tube S1 and the output voltage of IGBT switch tube S2, and obtain the duty cycle d of IGBT switch tube S1 respectively. buck and the duty cycle d of the IGBT switch tube S2 boost ; Step 2: Determine whether it is 1-d boost -d buck <0, if yes, go to step 3, if no, go to step 4; Step 3: Switch to boost mode, specifically: set the duty cycle of IGBT switch S1 to d buck =1, and adjust the duty cycle d of the IGBT switch tube S2 according to the voltage reference value and the output voltage of the IGBT switch tube S2 boost ; Step 4: Switch to step-down mode, specifically: set the duty cycle d of the IGBT switch tube S2 to boost =0, and adjust the duty cycle d of the IGBT switch tube S1 according to the voltage reference value and the output voltage of the IGBT switch tube S1 buck .

2. A method for switching a dual-tube Buck-Boost circuit mode according to claim 1, characterized in that: In step 1, a voltage sensor is used to collect the output voltage of the IGBT switch tube S1 and the output voltage of the IGBT switch tube S2.

3. A method for switching a dual-tube Buck-Boost circuit mode according to claim 1, characterized in that: Step 3 also includes: the first PI controller generates a PWM control signal according to the difference between the voltage reference value and the output voltage of the IGBT switch tube S2, and sends it to the first driver, and the first driver adjusts the duty cycle of the IGBT switch tube S2 according to the PWM control signal.

4. A method for switching a dual-tube Buck-Boost circuit mode according to claim 1, characterized in that: Step 4 also includes: the second PI controller generates a PWM control signal according to the difference between the voltage reference value and the output voltage of the IGBT switch tube S1, and sends it to the second driver, and the second driver adjusts the duty cycle of the IGBT switch tube S1 according to the PWM control signal.

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