12 Volt DC Power Supply Circuit

Posted on Feb 4, 2014

The schematic diagram below shows a simple trivial low-cost 12 volt DC 50W off-line SMPS switching power supply circuit. It can be used for DIY home projects or to learn operation of flyback converters. This PSU can work over a universal input AC line range 90-264 VAC. It provides a nominal 12V DC output at more than 4A load. Line and load regulation is better then 0. 5%.

12 Volt DC Power Supply Circuit
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The unit has overcurrent, overtemperature and overvoltage protections, as well as passive inrush current limiting. Output ripple are approximately 0. 2 V peak to peak in the range 0 to 20 MHz. If you need to get lower ripple, you may put an additional output capacitor or an LC filter outside of the feedback loop. This project is a modification of a 24V circuit that I`ve designed many years ago as a consultant for a small company. That company wanted a plug-in replacement to a cheap off-the-shelf AC to DC power supply, which had a long lead time. By the time I`ve completed the design and built a proto, they found the off-the-shelf part elsewhere in stock. So, they never proceeded with a manufacturing of this module. Accordingly, I have not tested this design beyond a basic DVT. You can build this circuit for personal use (at your own risk of course). But you are not allowed to republish the content of this page anywhere or use it for commercial purposes without my permission. To safely test or troubleshoot this circuit it is recommended to power it via an isolation transformer or from an isolated AC source. Also note that an offline single-transistor flyback converter generates internal voltages which may reach 600 V. Don`t try to play with this circuit unless you are of a legal age, understand power electronics and know how to deal safely with high voltage. You may want to take our quick power supply safety quiz. This AC...

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