FPGA-Based High-Frequency Digital Pulse Width Modulator Architecture for DC-DC Converters

Abstract

Digital pulse width modulator is an integral part in digitally controlled Direct Current to Direct Current (DC-DC) converter utilized in modern portable devices. This paper presents a new Digital Pulse Width Modulator (DPWM) architecture for DC-DC converter using mealy finite state machine with gray code encoding scheme and one hot encoding method to derive the variable duty cycle Pulse Width Modulation (PWM) signal without varying the clock frequency. To verify the proposed DPWM technique, the architecture with control input of six, five and four bits are implemented and the maximum operating frequency along with power consumption results is obtained for different Field Programmable Gate Array (FPGA) devices. The post layout timing results are presented showing that architecture can work with maximum frequency of 326 MHz and derive PWM signal of 3.59 MHz. Experimental results show the implementation of the proposed architecture in low-cost FPGA (Spartan 3A) with on-board oscillator clock frequency of 12 MHz which is multiplied internally by two with Digital Clock Manager (DCM) and derive the PWM signal of 1.5 MHz with a time resolution of 1 ps.