Converter makes standby mode efficient

27 May 2008

An off-line switched mode converter saves component count, and ensure efficiency in standby mode.

The VIPer17 converter from STMicroelectronics eliminates the need for external sensing components and start-up resistor by virtue of a high-voltage start-up current generator. It integrates an 800V avalanche-rugged MOSFET and has constant-current operation with an adjustable set point for use with all mains voltages in SMPSs up to 12W.

The converter can reduce system standby power and average power consumption to meet Energy Star and Blue Angel energy-saving initiatives. In standby mode, or other light-load conditions, the convert automatically enter burst mode to maximise efficiency. For example, the VIPer17’s typical standby power consumption of 50mW can be reduced to 30mW when used in an optimised transformer design, according to the company.

Protection features include adjustable over-voltage and overload protection, hysteretic over-temperature protection and two levels of over-current protection. When a fault is detected, the auto-start function prevents damage to the power supply or the load. An integrated soft start function is active at start-up or after a fault to reduce stress on the secondary diode and to help prevent transformer saturation.

PWM operation with switching-frequency jittering also enables designers to reduce EMI at the switching frequency, saving costs through reduced shielding in consumer products, home appliances and lighting systems.

The converter is packaged in a seven-pin, through-hole DIP (N type) and in a D type, surface mount package. The layout incorporates a double island for the power MOSFET and controller, claimed to maximise reliability.

Variants are the VIPer17LN/LD with 60kHz fixed switching frequency and the VIPer17HN/HD with 115kHz.

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