International Rectifier Introduces New IR1175 Synchronous Rectification ICJanuary 30, 2000 by Jeff Shepard
International Rectifier (IR, El Segundo, CA) introduced the IR1175 synchronous rectification IC (SRIC), a single-chip, application-specific IC designed to provide optimized gate drive for the MOSFETs configured as synchronous rectifiers in the secondary side of an isolated dc/dc converter. The IR1175 SRIC programs the gate drives to ensure that the losses through the synchronous rectifiers are minimized and the parasitic diodes do not conduct.
According to IR, the IR1175 SRIC boosts dc/dc converter efficiency to 90 percent at 3.3V output when used with IR application-specific HEXFET power MOSFETs. In operation, the IR1175 SRIC uses a modified phase lock loop to lock the switching frequency of the secondary-side synchronous rectification MOSFETs to the primary-side switching action. This allows the secondary-side MOSFETs to be pre-fired with full programmable control of turn-on transition lead time, as well as the dead time and overlap between gate drive signals. Pre-firing the MOSFETs eliminates parasitic diode conduction, and all the output current is now conducted through the active channels of the MOSFETs with lower losses.
"The operation of the IR1175 SRIC is designed to be independent of the primary-side topology, and it can be used in both forward and active clamp converters. Our new IR1175 SRIC is the easiest and most practical way to implement more efficient synchronous rectification," said David Tam, VP of the IR Power IC Group. According to IR, using the new device with IR application-specific MOSFETs allows designers of even the simplest forward converter to match the efficiency of patented active-clamp topologies with their expensive licensing fees.
According to IR, development of commercial dc/dc converters using the IR1175 SRIC is underway at leading manufacturers of telecom power converters. Samples of the IR1175 SRIC are available from IR on the Internet, as well as through IR distributors and the customer service line. In quantities of 10,000, the new devices cost $2.95 each. Volume production is scheduled for March 2000.