Digital Feedback Control of a Full-Bridge DC-DC Converter with Input Voltage Based Gain Scheduling

Digital feedback control of a full-bridge DC-DC converter, using a gain scheduled PI controller, is presented in this paper. Input voltage to the converter varies over a large range, as a result, controller gain designed for one particular input voltage may not give the optimum performance. Consequently, gain of the digital PI controller is made a function of the varying input voltage, and such a strategy leads to the system bandwidth and phase margin having a constant optimum value. This in turn gives a better transient response, both with changes in load as well as changes in input voltage. A low cost 16 bit PIC microcontroller, which has an inbuilt ADC and a PWM generation module, is used for implementing the proposed digital controller. The experimental results from a 50 W prototype have been provided to show the effectiveness of this control strategy.