Stability Analysis And System Design Of Digital Peak Current Controlled Boost Converters

In the traditional power electronic circuits, the realization of current control or voltage control in DC-DC converters is trough analog circuits. With the development of digital signal processing technology, digital control technology has been used more and more widely in switching converters because of its advantages, such as good flexibility, short development cycle and so on. Studies have shown that there exists complicated nonlinear behavior in DC-DC converters. Because of the effect of quantization error and delays, there are a few researches on the nonlinear characteristics of digital controlled DC-DC converters. Researches on the nonlinear characteristics of digital controlled DC-DC converters have vital significance for the development of nonlinear circuit theory and the optimization of parameter design in practical circuits.This thesis aims to establish a model of digital peak current controlled Boost converters, and then analyze and verify its stability. Firstly the basic operation principle of a Boost converter is introduced and the transfer functions of the main circuit are obtained through state space averaging method. The focuses of this thesis are modeling and stability analysis. The digital controller includes analog-to-digital conversions, a digital proportion-integration-differentiation compensator and a digital pulse width modulator. Issues including the sample-and-hold unit, quantization error and delays are discussed in this thesis. According to the operation principle of digital peak current control, the discrete z-domain model is established using the trailing-edge modulation and with the issues mentioned above taken into consideration. Meanwhile, a circuit simulation model is established and simulations with variable parameters are performed. The stability is analyzed combining with the distribution of the closed-loop system’s eigenvalues. We can find that there is nonlinear behavior in digital peak current controlled Boost converters.In this thesis, the realization of the hardware and the software of the system is presented. The hardware part includes the sampling circuit, analog to digital conversion circuit and driving circuit. The software part is mainly coded with VHDL. Its design and simulation is finished trough QuartusⅡ. What’s more, an experimental platform based on FPGA is established. Lastly, the correctness of the system design and the effectiveness and accuracy of the system model are verified by the experiment.