Design Of Pulse Train Controlled PCCM Buck-Boost Converter Based On FPGA

Traditional analog switching power supply control technology can’t overcome some shortcomings of its existence. It has been unable to meet the needs of rapid development of power electronics technology. Digital control technology can realize complex control strategies, and flexibility and reliability of the system can have greatly improved. Therefore, using the digital control technology to replace the analog control technology is the inevitable trend of switching power supply development. Due to the rapid, confidentiality, flexibility and other advantages field programmable gate arrays(FPGA) has been widely concerned.The control policy of switching power supply is an important factor in its performance. Traditional pulse width modulation(PWM) technology is based on the linear control theory. Under this kind of control mode converter has poor robustness, transient characteristics shortcomings and so on. To meet the requirements of electronic equipment of switch power supply, people have been trying to use a better control technology to improve the performance of the switch power supply. Pulse train(PT) control technique which is proposed in recent years is a new type of non-linear switching power supply control technology. It has been widely studied due to the simple control circuit and good transient characteristics, etc. At present, the study of PT control technology is mostly for converter working in the inductor current discontinuous conduction mode(DCM), whose load capacity is poor.Based on PT control principle and considering the equivalent series resistance of inductor and capacitor, this paper puts forward a new method of voltage type PT control, which contains two pseudo continuous control variables and makes the Buck-Boost converter work in inductor current pseudo continuous conduction mode(PCCM). The working principle of the converter and its high and low voltage control pulse energy are analyzed in detail. At the same time by comparing with the voltage type PT control DCM Buck-Boost converter we can conclude that the load capacity of PCCM converter is greatly improved. The voltage type PT PCCM Buck-Boost converter circuit simulation model is established in MATLAB/Simulink environment, and compared its simulation waveforms with theoretical analysis. The voltage sampling comparison circuit, isolating circuit, current sampling circuit and driver circuit is analyzed and designed. The digital control module is designed in the Quartus II software. After completing the design of PT control PCCM Buck-Boost converter experiment circuit based on FPGA, collecting its experimental waveforms, which are compared with the simulation waveforms. The analysis result reflects the new control method is feasible, and validates the correctness of theoretical analysis and the study of simulation.