The Texas Instruments UC2845D is a current-mode PWM controller designed for a range of isolated and non-isolated DC-DC converter topologies: boost, buck, flyback, and forward. It drives a single transistor stage and includes frequency control for setting the oscillator up to 500 kHz. The 48% maximum duty cycle is a hard limit for flyback and forward converters where transformer reset timing is critical — push past it and you risk core saturation on the next cycle. The controller operates from a 12 V to 28 V supply rail, typical for industrial power bricks and auxiliary supplies in motor drives or telecom equipment.
Package and mounting
The 48% duty cycle ceiling is the first thing to check when the MOSFET or transformer runs hot. The controller will not let the duty cycle exceed 48% per cycle, which forces the transformer to reset fully before the next on-time.