BiCMOS combination PFC/PWM controllers

Unitrode Corp. (Merrimack, NH) recently announced the UCC38500 family of BiCMOS combination PFC/PWM controllers. According to Unitrode, the controllers provide easy and cost-effective compliance to IEC 1000-3-2 harmonic reduction requirements for cost-sensitive off-line equipment. The company claims that by combining the power factor correction (PFC) and pulse width modulation (PWM) control functions, the controllers offer a high level of integration and eliminate overhead associated with two distinct controllers. The synchronization between the two stages and the modulation offset, where the PFC stage is leading-edge modulated and PWM stage is trailing-edge modulated, is designed to allow maximum cancellation of ripple in the bulk capacitor. The company also claims that a controlled start-up of the PWM stage minimizes converter implementation costs. The PFC section of these controllers operates with the average current mode controlled boost power architecture. The PWM section implements peak current mode control with 50 percent maximum duty cycle and is claimed to provide complete control solutions for popular isolated converter topologies, such as single-ended forward and flyback and 2-switch forward. The PWM also features a simple interface to optocouplers for feedback signal processing. According to Unitrode, any line-connected power converter requiring PFC can benefit from the increased integration and lower implementation cost offered by the UCC38500. The combination of PFC voltage options and PWM stage start-up options are offered through Unitrode's available variations of the family: UCC38500/01/02/03. In quantities of 1,000, pricing will be from $2.64 each.