Electronic Design

Application-Specific MOSFET Tailored For Zero-Voltage Switching Supplies

A new series of HEXFET power MOSFETs targets high-frequency zero-voltage switched (ZVS) power-supply circuits. De-signed by International Rectifier, this line boosts efficiency and reduces EMI emissions. It also offers extremely low RDS(ON) at a breakdown voltage of 500 V. In addition, these devices boast a much faster reverse-recovery time.

"Typical reverse-recovery charge is 50% lower than that found in existing industry-standard MOSFETs," claims IR's product manager, Chris Bull. This translates into a typical reverse-recovery time of 150 ns for the ZVS-specific MOSFETs, enabling switching speeds up to 250 kHz.

According to Bull, the use of a faster reverse-recovery body diode eliminates failure due to dv/dt stress at higher frequencies. As a result, the MOSFET's ruggedness is improved. Plus, the RDS(ON) ranges from 0.095 to 0.280 Ù at a 500-V breakdown. By cutting conduction losses, the lower on-resistance increases the overall efficiency of ZVS-based ac-to-dc converters.

Also, the MOSFETs feature significantly lower gate capacitance, requiring lower gate-drive current. For example, typical input capacitance (CISS) ranges from 3000 to 9100 pF, while typical output capacitance (COSS) ranges from 300 to 930 pF. Reverse-transfer capacitance (CRSS) generally ranges from 20 to 56 pF.

The four initial members of this family include the IRFPS40N50L, the IRFBA31N50L, the IRFB17N50L, and the IRFBL17N50L. While the IRFPS40N50L is rated for a maximum drain current of 40 A, the IRFBL17N50L handles 17 A maximum of drain current. Typical RDS(ON) is 0.095 Ù for the 40-A unit, and 0.280 Ù for the 17-A version.

The new MOSFETs are available in packages ranging from the super-247 for the IRFPS40N50L to the super-D2PAK for the IRFBL17N50L. IR intends to expand this product line with parts rated for lower currents. Prices start at $1.94 each in quantities of 10,000.

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

See associated figure.

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