In the quest for ever-greater power-supply efficiency, especially spanning light load to fully load, along with increasingly required power factor correction (PFC), designers have developed a wide array of topologies which address every source of loss and seek to minimize them.
The latest entry is the Fairchild Semiconductor FAN6920MR, a critical-mode PFC and quasi-resonant current-mode PWM controller targeting all-in-one (AOI) supplies, AC/DC notebook adapters, switching-mode power supplies (SMPS), LED LCD TV backlighting, and even LED area-illumination. A typical application circuit is shown in the figure:
Key features include:
- Integrated PFC and Flyback Controller
- Critical Mode PFC Controller
- Zero-Current Detection for PFC Stage
- Quasi-Resonant Operation for PWM Stage
- Internal Minimum tOFF 5μs for QR PWM Stage
- Internal 10ms Soft-Start for PWM
- Brownout Protection
- High /Low Line Over-Power Compensation
- Auto-Recovery Over-Current Protection
- Auto-Recovery Open-Loop Protection
- Externally Triggering Auto-Recovery Protection (RT Pin)
- Adjustable Auto-Recovery Over-Temperature Protection (RT Pin)
- VDD Pin and Output Voltage OVP (Auto-Recovery)
- Internal Over-Temperature Shutdown (140°C)
Among its other attributes, the dual-switch flyback controller recycles leakage current from the transformer and derating the MOSFET. It uses extended valley detection to detect up to the 9th or 12th valley voltage, thus reducing the switching losses at light load. Power consumption is under 0.3 W.
In a 19V/90W reference design measuring 65 x 90 mm, efficiency was between 89 and 91% for both 115 Vac and 230 Vac line inputs, with no-load consumption of about 0.195 W.
Price, packaging, and availability: The FAM6920MR is available now, and is housed in a 16-lead small outline package (SOP); it is priced at $0.82 (1000 pieces).
For more information: contact Fairchild Semiconductor Corp, or click here.