The Si9118/Si9119 are a BiC/DMOS current-mode pulse width modulation (PWM) controller ICs for high-frequency dc/dc converters. Single-ended topologies (forward and flyback) can be implemented at frequencies up to 1 MHz. The controller operates in constant frequency mode during the full load and automatically switches to pulse skipping mode under light load to maintain high efficiency throughout the full load range. The maximum duty cycle is easily programmed with a resistor divider for optimum control.