Control method and device of buck-boost converter

Abstract

The application discloses a control method and device of a Buck-Boost converter, and solves the problem of how to reduce circuit loss, and belongs to the technical field of electronic control.The application adopts two-degree-of-freedom control, one degree of freedom is used for controlling the duty ratio of one switch of the Buck-Boost converter, and the other degree of freedom is used for controlling the duty ratio of the other switch of the Buck-Boost converter, the voltage conversion ratio is controlled through the two degrees of freedom, and the maximum inductance current is controlled by compensating the one degree of freedom.The application controls the maximum inductance current while ensuring that the circuit has the functions of step-up and step-down, so that the inductance current stress and the circuit loss are reduced.

Description

Technical Field

[0001] This invention relates to a control method and device for a buck-boost converter, belonging to the field of electronic control technology. Background Technology

[0002] In many power circuits, the input and output voltage ranges are wide, requiring buck-boost functionality. The dual-transistor Buck-Boost circuit, with its simple operating principle and wide voltage ratio, is a typical example of a buck-boost circuit. However, for dual-transistor Buck-Boost circuits, employing buck-boost functionality without mode switching can lead to high inductor current stress, significant circuit losses, and demanding high-performance power switching devices. For instance, in some dynamic wireless charging systems, large mutual inductance fluctuations result in significant input voltage fluctuations at the receiver, leading to a wide input voltage range for the receiver's DC-DC converter. Simultaneously, the output, being a battery load, also has a wide voltage range, necessitating buck-boost functionality in the power converter. However, for dual-transistor Buck-Boost circuits, while providing buck-boost functionality, inductor current stress becomes a crucial factor limiting the current stress of power devices. How to reduce inductor current stress in dual-transistor Buck-Boost circuits while maintaining buck-boost functionality has become a current research hotspot. Summary of the Invention

[0003] To address the issue of reducing circuit losses, this invention provides a control method and apparatus for a buck-boost converter.

[0004] The present invention discloses a control method for a buck-boost dual-transistor Buck-Boost converter, the buck-boost dual-transistor Buck-Boost converter comprising two switching transistors, the method comprising:

[0005] Voltage reference value u ref and actual voltage u o The difference is processed by two PI controls. One PI control directly generates a control signal for one switch of the buck-boost converter, which compensates for the control signal generated by the other PI control. The compensated control signal is used to control the other switch of the buck-boost converter. The maximum value of the inductor current is controlled by controlling the amount of compensation.

[0006] As a preferred method, the other generated control signal is compensated to obtain a new control signal:

[0007] Adjustment signal u i and voltage reference value u refAn adjustment signal is generated by the regulator. The adjustment signal is subtracted from the control signal generated by the PI control to generate a new control signal. The new control signal is used to control the other switching transistor of the buck-boost converter.

[0008] The present invention also provides a control device for a buck-boost converter, wherein the buck-boost converter includes two switching transistors, and the control device includes a subtractor 1, a subtractor 2, a subtractor 3, a PI controller 1, a PI controller 2, a drive circuit 1, a drive circuit 2, and a compensation circuit.

[0009] Voltage reference value u ref and actual voltage u o Simultaneously, the input is fed to subtractor 1, the output of subtractor 1 is fed to PI controller 1, the output of PI controller 1 is fed to drive circuit 1, and the drive signal of drive circuit 1 is fed to one of the switching transistors of buck-boost converter 1.

[0010] Voltage reference value u ref and actual voltage u o Simultaneously, the signal is input to subtractor #2, and the output of subtractor #2 is input to PI controller #2. The compensation circuit is used to obtain the compensation signal. The compensation signal and the output of PI controller #2 are simultaneously input to subtractor #3. The output of subtractor #3 is input to drive circuit #2. The drive signal of drive circuit #2 is input to another switching transistor of buck-boost converter. The maximum value of inductor current is controlled by controlling the magnitude of the compensation signal.

[0011] Preferably, the compensation circuit includes a divider and a regulator;

[0012] Adjustment signal u i and voltage reference value u ref Simultaneously, the input is fed to the divider, and the resulting proportional signal is fed to the regulator. The regulator generates an adjustment signal, which is then used as a compensation signal and input to subtractor number 3. This control signal u... i The value of the inductor current is controlled by the size of the inductor.

[0013] The beneficial effects of this invention are as follows: This invention employs two degrees of freedom control. One degree of freedom controls the duty cycle of one switch in the buck-boost converter, and the other degree of freedom controls the duty cycle of the other switch in the same converter. By controlling the voltage transformation ratio together with these two degrees of freedom, and by compensating for one of the degrees of freedom, the maximum inductor current is controlled. This invention ensures that the circuit has buck-boost functionality while controlling the maximum inductor current to reduce inductor current stress and circuit losses. Attached Figure Description

[0014] Figure 1 A schematic diagram of a buck-boost converter with two transistors.

[0015] Figure 2 This is a schematic diagram illustrating the principle of the control strategy of the present invention;

[0016] Figure 3 This is a schematic diagram illustrating the specific control principle of the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0019] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the scope of the invention.

[0020] This embodiment describes a control method for a buck-boost dual-transistor Buck-Boost converter. The buck-boost dual-transistor Buck-Boost converter includes two switching transistors, and its structure is as follows: Figure 1 As shown, the control methods include:

[0021] Voltage reference value u ref and actual voltage u oThe difference is processed by two PI controls. One PI control directly generates a control signal for one switch of the buck-boost converter, which compensates for the control signal generated by the other PI control. The compensated control signal is used to control the other switch of the buck-boost converter. The maximum value of the inductor current is controlled by controlling the amount of compensation.

[0022] This implementation focuses on a dual-transistor Buck-Boost circuit, designing a new control strategy. While controlling the buck-boost voltage of the dual-transistor Buck-Boost circuit with two degrees of freedom, it can also control the maximum value of the inductor current, thereby controlling the inductor current stress and changing the circuit efficiency.

[0023] In this embodiment of the control method, a method for compensating another generated control signal to obtain a new control signal after compensation is as follows:

[0024] Adjustment signal u i and voltage reference value u ref An adjustment signal is generated by the regulator. The adjustment signal is subtracted from the control signal generated by the PI control to generate a new control signal. The new control signal is used to control the other switching transistor of the buck-boost converter.

[0025] Based on the technical solution, a control program is formed. The difference between the voltage reference value and the actual voltage is controlled by two PI controllers. One controller directly generates the S1 control signal, and the other controller subtracts the reference voltage value from the regulation signal generated by the regulator to generate the S2 control signal. The inductor current is controlled by controlling this fixed value. The control program is simple and feasible, and it is easy to implement using microcontroller programming.

[0026] like Figure 3 As shown, specifically, a voltage sensor is used to collect the output voltage, which is compared with a voltage reference value. Then, a PI controller generates a control signal, which, after passing through a drive circuit, forms a drive signal to control the switching transistor S1. Simultaneously, the difference between the voltage reference value and the actual voltage is used by the PI controller to generate a control signal. This control signal is then subtracted from an adjustment signal generated by a regulator and a reference voltage value, forming a new control signal. This new control signal, after passing through a drive circuit, forms a drive signal to control the switching transistor S2. This achieves the simultaneous control of voltage and inductor current.

[0027] This embodiment also provides a control device for a buck-boost dual-transistor Buck-Boost converter. The buck-boost dual-transistor Buck-Boost converter includes two switching transistors, and the structure of the buck-boost dual-transistor Buck-Boost converter is as follows: Figure 1As shown, the control device in this embodiment includes a subtractor No. 1, a subtractor No. 2, a subtractor No. 3, a PI controller No. 1, a PI controller No. 2, a drive circuit No. 1, a drive circuit No. 2, and a compensation circuit.

[0028] Voltage reference value u ref and actual voltage u o Simultaneously, the input is fed to subtractor 1, the output of subtractor 1 is fed to PI controller 1, the output of PI controller 1 is fed to drive circuit 1, and the drive signal of drive circuit 1 is fed to one of the switching transistors of buck-boost converter 1.

[0029] Voltage reference value u ref and actual voltage u o Simultaneously, the signal is input to subtractor #2, and the output of subtractor #2 is input to PI controller #2. The compensation circuit is used to obtain the compensation signal. The compensation signal and the output of PI controller #2 are simultaneously input to subtractor #3. The output of subtractor #3 is input to drive circuit #2. The drive signal of drive circuit #2 is input to another switching transistor of buck-boost converter. The maximum value of inductor current is controlled by controlling the magnitude of the compensation signal.

[0030] The control device in this embodiment ensures that the circuit has the function of step-up and step-down voltage regulation while controlling the maximum value of the inductor current to reduce inductor current stress and circuit losses. The compensation circuit in this embodiment includes a divider and a regulator;

[0031] Adjustment signal u i and voltage reference value u ref Simultaneously, the input is fed to the divider, and the resulting proportional signal is fed to the regulator. The regulator generates an adjustment signal, which is then used as a compensation signal and input to subtractor number 3. This control signal u... i The value of the inductor current is controlled by the size of the inductor.

[0032] This invention is primarily applied to Buck-Boost circuits with a wide input voltage range. Compared to traditional buck-boost control techniques, its key features are: it can control the maximum value of the inductor current while still meeting the buck-boost requirements, and it can achieve buck-boost without mode switching, effectively reducing circuit power and significantly improving circuit performance.

[0033] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A control method for a buck-boost converter, characterized in that, The buck-boost converter includes a switching transistor S1, a diode D1, and an inductor I. L The circuit consists of a switching transistor S2, a diode D2, and a capacitor. The drain of the switching transistor S1 and the cathode of the diode D2 are connected to the positive terminal of the capacitor, while the source of the switching transistor S1 and the cathode of the diode D1 are connected to the inductor I. L One end is connected simultaneously to the drain of switching transistor S2 and the anode of diode D2, and to inductor I. L The other end is simultaneously connected, with the source of switch S2, the anode of diode D1, and the cathode of capacitor all connected to the negative terminal of the input power supply; the method includes: Voltage reference value u ref and actual voltage u o The difference is controlled by two PI controllers. One controller directly generates the control signal for the switch S1 of the buck-boost converter and compensates for the control signal generated by the other controller. The new control signal is used to control the switch S2 of the buck-boost converter. The maximum value of the inductor current is controlled by controlling the amount of compensation. The method for compensating the other generated control signal to obtain a new control signal: Adjustment signal u i and voltage reference value u ref After division, an adjustment signal is generated by the regulator. The adjustment signal is subtracted from the control signal generated by the PI control to generate a new control signal. The new control signal is used to control the switching transistor S2 of the buck-boost converter.

2. A control device for a buck-boost converter, characterized in that, The buck-boost converter includes a switching transistor S1, a diode D1, and an inductor I. L The circuit consists of a switching transistor S2, a diode D2, and a capacitor. The drain of the switching transistor S1 and the cathode of the diode D2 are connected to the positive terminal of the capacitor, while the source of the switching transistor S1 and the cathode of the diode D1 are connected to the inductor I. L One end is connected simultaneously to the drain of switching transistor S2 and the anode of diode D2, and to inductor I. L The other end is connected at the same time, and the source of the switching transistor S2, the anode of the diode D1, and the negative terminal of the capacitor are simultaneously connected to the negative terminal of the input power supply. The control device includes subtractor No. 1, subtractor No. 2, subtractor No. 3, PI controller No. 1, PI controller No. 2, drive circuit No. 1, drive circuit No. 2, and compensation circuit. Voltage reference value u ref and actual voltage u o Simultaneously, the input is fed to subtractor 1, the output of subtractor 1 is fed to PI controller 1, the output of PI controller 1 is fed to drive circuit 1, and the drive signal of drive circuit 1 is fed to switch S1 of buck-boost converter. Voltage reference value u ref and actual voltage u o The input is simultaneously fed to subtractor #2, and the output of subtractor #2 is fed to PI controller #2. The compensation circuit is used to obtain the compensation signal. The compensation signal and the output of PI controller #2 are simultaneously fed to subtractor #3. The output of subtractor #3 is fed to drive circuit #2. The drive signal of drive circuit #2 is fed to the switching transistor S2 of buck-boost converter. The maximum value of the inductor current is controlled by controlling the magnitude of the compensation signal. The compensation circuit includes a divider and a regulator. Adjustment signal u i and voltage reference value u ref Simultaneously, the input is fed to the divider, and the resulting proportional signal is fed to the regulator. The regulator generates an adjustment signal, which is then used as a compensation signal and input to subtractor number 3. This control signal u... i The value of the inductor current is controlled by the size of the inductor.

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