Technology Front
Primary-Side Switcher Cuts Power Supply Size and Cost While Improving Efficiency and Performance
Published: Sep 04,20141411 Read
Diodes Incorporated introduced the AP3988 off-line, side-switching controller designed to cut costs and improve power supply performance in chargers, ADSL adapters and home appliance supplies.
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By providing primary-side control, the device eliminates the requirement for opto-couplers and secondary-side control circuitry, reducing component count, board space requirements and cost. Primary-side regulation results in higher efficiency with less heat generated in the power supply, which increases reliability.
Additional benefits include improved output voltage and current accuracy, enhanced over-voltage and short-circuit protection, and better EMC performance, achieved by frequency dithering.
The AP3988 switcher regulates output voltage using piece-wide pulse frequency modulation, in which analog levels are represented as fixed-duration pulses of varying repetition rate. Transistors with 700VCBO are built into the device and start-up current is typically just 0.2µA.
This switcher has integral cable voltage drop compensation of 5% of nominal voltage and adjustable line voltage compensation.
The AP3988 controller is designed for use in 5.5W adapters and is offered in the SO-7 package.