Digital PWM Control for Isolated DC-DC Converters with Two Pulses Modulating PWM

Abstract

This paper describes a novel digital control solution for isolated DC-DC converter. Compared with non-isolated DC-DC converters, isolated ones need to realize isolation of control between primary and secondary side. In this paper, the whole digital control system is implemented using two FPGAs. The one on the secondary side includes a compensator (PI regulator), a high resolution digital PWM (DPWM), a modulator and a carrier transmitter. Another one on the primary side contains a carrier receiver, a demodulator and a subsidiary controller to fulfill some protection and generate synchronous signal. Several approaches to modulate and demodulate DPWM signal are proposed and analyzed. The modulated (or carrier) signals of PWM waveform and synchronous signals are transmitted between primary and secondary side through two very small signal transformers respectively to fulfill isolation.