Reference Design Eases Bus Converter Development

The IRDC2086-330W from International Rectifier (IR) is a reference design featuring the IR2086S dc bus converter control IC and DirectFET power MOSFET chipset. The reference design simplifies development of 48-V input brick or embedded power supplies for high-end server applications. The design is a 48-V to 9.6-V (35-A) unregulated dc bus converter that is 97% efficient, and is 30% smaller than quarter brick regulators. In addition, the IRDC2086-330W reduces the number of powertrain components from three ICs and 14 FETs to a single IC and eight FETs.

The reference design chipset consists of the IR2086S primary-side, full-bridge control IC plus eight power MOSFETs: four IRF6646 80-V DirectFET primary-side MOSFETs and four IRF6635 30-V DirectFET secondary-side synchronous MOSFETs. Small MOSFETs are used for bias switching (one IRF7830 80-V MOSFET in an SO-8) and the secondary clamp (two IRF6621 30-V Small Can DirectFET MOSFETs).

The IR2086S full-bridge controller operates at high frequency (programmable to 500 kHz), and features an integrated soft-start capacitor that gradually increases duty cycle to 50% over 2000 cycles. The soft start feature limits inrush current during start-up and maintains equal pulse widths for the high- and low-side MOSFETs in the full bridge throughout the start-up sequence.

The reference design includes the IRDC2086-330W fully assembled pc board, and a CD-ROM containing a User’s Guide, data sheets, pc board files and application notes. Available now, the IRDC2086-330W dc bus converter reference design is priced at $250 each.