High Resolution DPWM in a DC-DC Converter Application Using Digital Sigma-Delta Techniques

This paper demonstrates a DC-DC converter application in which a multi-bit digital sigma-delta modulator pre-processes the duty-cycle value before application to the DPWM, increasing the effective resolution of the DPWM dramatically. In this method, the DPWM duty-cycle command is pre-processed by a multi-bit digital sigma-delta modulator, so that the DPWM quantization noise is shaped in frequency. As a result, the total quantization noise at the output of the DC-DC converter is reduced, and the effective resolution of the DPWM in the control loop is increased dramatically. A prototype converter was seen to perform with an effective DPWM resolution of at least 11 bits, with an actual DPWM resolution of less than 6 bits