This paper describes a digital controller chip set for
high-frequency DC-DC power converters with galvanic isolation.
The secondary-side controller includes an A/D converter and a
transmitter that sends a digital error signal as serial data through
an opto-coupler. The primary-side controller includes a serialdata
receiver, a programmable digital PID regulator, and a highresolution
(10-bit) digital pulse-width modulator. The digital
error signal transmission through the isolation boundary
eliminates the problem of gain variation when the opto-coupler is
used in linear mode. The chip set is tested as a replacement for a
conventional analog current-mode controller in a 3.3 V, 20 A, 400
KHz DC power supply. Experimental results with the digital
controller show improved dynamic responses compared to the
responses obtained with the analog controller.