Power Integrations - DER580

This engineering report describes a 59 V (nominal), 118 W flyback reference design for a
power supply operating from 180 VAC to 264 VAC. The power supply output is designed
with a constant voltage / constant current characteristic for use in battery charger
applications. The charging circuit is optimized for a lead-acid battery. At charging
currents below ~0.5 A, the output voltage switches form the 59 V charging voltage to a
float voltage of 56 V to maintain battery charge without overcharging. This is a standard
feature for chargers intended for lead-acid batteries.

The design is based on the TOP267EG with no PFC input stage. It is designed to operate
without a fan, with a thermal switch reducing the current limit at elevated temperature
(thermal foldback) to enable continued charging at reduced output current without
thermal shutdown.