Electronic Design

Offline Current-Mode Controller Expedites SMPS Design

The second CoolSET generation from Infineon Technologies packs a fixed-frequency PWM current-mode controller and a high-voltage power MOSFET in the same 8-pin plastic DIP. Its on-board CoolMOS-based power MOSFET handles breakdowns up to 800 V. And, CoolSET II members offer drain-source breakdowns of both 650 and 800 V for output currents of 1 to 3 A.

To enhance the controller's reliability, the MOSFETs include temperature sensing for rapid thermal shutdown when device temperature exceeds a set value. The MOSFETs additionally come with undervoltage lockout to prevent destruction of the transistor by the incorrect triggering of voltage levels.

An external shunt gives designers flexibility in optimizing the output transformer and diodes while reducing the load on the semiconductor. Other features include softstarting for a smooth turn-on at startup and autorestart, as well as a leading-edge blanking function for safe power-on. Also, the controller protects against overcurrent, overvoltage, and open loops.

In no-load conditions, the controller slashes standby power to less than 300 mW by lowering the switching frequency. To avoid audible noise, this is limited to 21 kHz. The device's normal switching frequency is 100 kHz. An applied burst mode further reduces standby power. No additional pin or external wiring is required to use these energy-saving techniques.

The controller targets compact, high-efficiency offline supplies like battery chargers for portable devices and adapters for consumer products. It suits auxiliary power supplies for PCs, where output-power requirements range from 10 to 47 W for a primary voltage of 85 to 265 V ac or 60 W for inputs of 190 to 265 V ac.

Initial members include the ICE2A165/265/365 and ICE 2A280. On-board power MOSFETs are rated at 650 V for the 2A165/265/365 and 800 V for the 2A280. In lots of 10,000, the 47-W output ICE 2A365 costs $0.82.

Infineon Technologies, 1730 North First St., San Jose, CA 95112; (408) 501-6000; www.infineon.com/coolset.

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