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500kHz PWM controller breakthrough

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SILICONIX, represented by Braemac , has announced the first 500kHz PWM controller ICs to combine two integrated MOSFET drivers and integrated signal drivers for secondary synchronous rectification.

Designed to provide a compact and efficient solution for fixed telecom applications requiring power supplies in the range of 50W to 150W, the new half-bridge (Si9122, Si9123) and push/pull (Si9124) devices operate over a 12 to 72V input voltage range, drive both primary side MOSFETs, and provide timing for the secondary synchronous rectifiers.

Each device incorporates a secondary-side FET drive signal for synchronous rectification and a direct primary MOS drive (1A maximum) on the high and low side.

A high-voltage start-up circuit is also integrated. Use of low-on-resistance MOSFETs as secondary synchronous rectifiers provides a significant increase in the converter efficiency - as high as 92%, even for low output voltages - when compared to using Schottky diodes.

The new ICs are compliant with the ETSI 300 132-2 standard, handling input voltages up to 100V for 100ms. Voltage-mode control with voltage feed-forward compensation provides for line transient response.

Programmable features include an input voltage detector, soft-start, a current-limit, and a programmable oscillator frequency from 200 to 600kHz.

All three devices also offer short-circuit protection, either through frequency foldback (Si9122) or hiccup mode (Si9123, Si9124), in addition to undervoltage lockout and thermal shutdown.

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