Quasi-Resonant PWM Controller from Diodes Incorporated Optimizes Efficiency in Power Adapter Applications

PLANO, Texas --- Diodes Incorporated introduces the AP3301. This quasi-resonant (QR) PWM controller enables the implementation of high-performance, cost-effective power supplies that are capable of meeting DOE6/COC Tier 2 efficiency requirements at all load levels. Targeting the key market of AC-DC adapters for set-top box and gaming console applications, this controller also meets the auxiliary power requirements of ATX/BTX computer motherboards and is suited for use in open-frame switching power supplies.

Multiple operating modes allow the AP3301 to achieve optimal efficiency at different load levels: Under low- or no-load conditions, the IC uses a burst mode to minimize standby power consumption while operating at a minimum switching frequency of approximately 20kHz to avoid audible noise. At intermediate loads, a valley-lock QR mode with frequency foldback improves efficiency and EMI performance. For heavy loads, or under low-line input conditions, the controller enters a continuous conduction mode (CCM) at a fixed 62kHz switching frequency for optimum conversion efficiency. A built-in frequency dithering function helps reduce EMI emission in both CCM and QR modes.

The AP3301 provides comprehensive protection features for enhanced system reliability. These include: AC-input brown-out protection, cycle-by-cycle current limit, precise output over-voltage protection, internal over-temperature protection, overload protection, and a pin fault-protection circuit, which detects floating or short connections on key signal pins and disables PWM switching to protect the power system.

With just minor changes to external components, the SOT-26 packaged AP3301 provides a pin-compatible replacement solution for Diodes’ existing AP3105/AP3125 PWM controllers. For further information, visit http://www.diodes.com


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