Electronic Design

Synchronous-Rectification Device Boosts Low-Voltage DC-DC Efficiency

Tailored to boost the power-conversion efficiency of low-voltage dc-dc isolated converters, the IR1176 is the newest member of International Rectifier's application-specific synchronous-rectification IC (SRIC) line. This device is primarily optimized for isolated voltage converters with a voltage output down to 1.5 V. Combined with the synchronous IRF7822 HEXFET, the SRIC enhances 1.5- and 1.8-V dc-dc converter efficiency.

Internal tests show that in-circuit efficiency is 86% for a 1.8-V, 40-A converter with a 48-V input. Likewise, the IR1176 provides 85% conversion efficiency for a 1.5-V, 40-A output with a 48-V input. It also controls gate-drive circuits to minimize losses in secondary-side, synchronous-rectification MOSFETs. Since the IR1176 operates independently of the primary-side topology, it can be used to implement simple forward topologies without resorting to patented active clamp or gate-drive compensation circuits.

By using a modified PLL to lock the switching frequency of secondary-side synchronous-rectification MOSFETs to the primary side, the IR1176 lets designers prefire secondary-side MOSFETs with fully programmable control of turn-on transition lead time, the dead time, and the overlap between gate-drive signals. Prefiring the MOSFETs eliminates parasitic diode conduction, ensuring that all output current conducts via the active MOSFET channels.

Housed in 20-lead SSOPs and DIPs, the IR1176 costs $3.50 each in 10,000-piece quantities.

International Rectifier Corp., 233 Kansas St., El Segundo, CA 90245-4359; (310) 252-7105; www.irf.com.

See associated figure.

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