External-Sync Power Supply with Universal Input Voltage Range for Monitors

External-Sync Power Supply with Universal Input Voltage Range for Monitors

This paper describes the design of a low−cost 90 W
flyback switching power supply for a multi−sync color
monitor. In order to minimize the screen interference from
the switching noise, the power supply can be automatically
synchronized at the fixed frequency of the horizontal
scanning frequency (15 to 32 kHz) of the color monitor. The
line and load regulations of the power supply are excellent.
Also, a new universal input−voltage adaptor enables the
power supply to operate at two input voltage ranges, 90−130
Vac or 180−260 Vac. It can minimize the ripple current
requirement of the input bulk capacitors and the stresses on
the power switch. The design demonstrates how to use
recently introduced components in a low−cost power
supply. The state−of−the−art perforated emitter
epi−collector bipolar power transistor MJE18004 and
opto−isolator MOC8102 are utilized.