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A New Approach to Circuit Breaker Design Using Silicon Carbide Switches - Nov 21
Mechanical circuit breakers can be low cost with minimal losses, but they operate slowly and wear out. Solid state versions overcome the problems and are becoming increasing viable as replacements at...
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Power Electronics Europe News
 
Quasi-resonant PWM controller boosts efficiency in power adapters

They enable the implementation DOE6/COC Tier 2 efficiency requirements at all load levels, in AC/DC adapters for set-top box and gaming console applications. The 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 controller to achieve optimal efficiency at different load levels. Under low- or no-load conditions, the IC uses a burst mode to minimise 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 fold-back 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. A built-in frequency dithering function helps reduce EMI emission in both CCM and QR modes.

Protection features 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.

 


 



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