Adapter efficiency peaked with quasi-resonant PWM controller

October 12, 2016 // By Graham Prophet
The AP3301 quasi-resonant (QR) PWM controller (Diodes Inc.) enables the design of high-performance, cost-effective power supplies that are capable of meeting DOE6/COC Tier 2 efficiency requirements at all load levels.

Targeting the 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 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 20 kHz 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 62 kHz 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. The AP3301 is priced at $0.20 (1000).


Diodes Incorporated;