Controllers Combine PFC, PWM

The UCC38500 family of BiCMOS combination PFC/PWM controllers provide easy and cost-effective compliance to IEC 1000-3-2 harmonic reduction requirements of cost-sensitive off-line equipment. By combining the power-factor-correction (PFC) and pulse-width-modulation (PWM) control functions, these controllers offer the highest level of integration and eliminate the overhead associated with two distinct controllers. The PFC section operates with the average-current-mode, controlled-boost power architecture of the firm’s UC3854 to provide an easy transition path for users while improving features such as multiplier linearity and current amplifier setup. The PWM section implements peak current mode control with 50% maximum duty cycle and provides complete control for isolated converter topologies such as single-ended forward and flyback, two-switch forward, and so on. The PWM section also features a simple interface to optocouplers for feedback signal processing.