There are relatively few ICs that manage power on the secondary side of an isolated supply. Although FETs have replaced diodes on modern synchronous buck converters, there has not been a similar effort to replace the diodes in the secondary of isolated supplies. International Rectifier's IR1167 SmartRectifier IC simplifies secondary SR (synchronous rectification) for ac-dc power converters and improves power density for high-power flyback and resonant half-bridge converters, enabling smaller, cooler designs.

The IR1167 is independent of the primary-side controller. It uses IR's proprietary HVIC (high-voltage IC) technology for directly sensing and controlling secondary-side rectification. In addition to controlling high-power flyback secondary sections, the SmartRectifier is the first commercial IC for resonant half-bridge converters. Compared with discrete current-transformer-based designs, the IR1167 increases power-subsystem efficiency by at least 1%. Independence from the primary side means that the IR1167 operates in variable frequency mode as well as at low-power "burst modes," providing a compliance path for the 1W standby initiative, and the CEC (California Energy Commission's) 80Plus requirements.

Traditional CT (current-transformer) control circuits waste energy, because large reversing current is required to sense polarity shifts. In contrast, IR's new SmartRectifier IC employs a new technique for precise, direct voltage sensing across the SR MOSFETs. The IR1167 uses IR's proprietary HVIC technology, making it compatible with all MOSFET gate types. The SmartRectifier technique allows small surface-mount SO-8 parts to replace large TO-220 packages.