Introduction: Simple 12VAC to 32VDC LED Driver
I designed this simple and cheap circuit to allow me to use existing halogen 12VAC power-supplies to power 20-100 Watt LEDs. It will work with conventional transformers or switch-mode types, as long as they produce 12VAC. When the AC swings up, and the input is positive, it charges capacitor C1 to 16 Volts. When the input goes negative it charges C2 to 16 volts. The capacitors are connected in series so the voltage across them is 16+16=32 Volts, which is just right to power the LED chips. The size of the capacitors is crucial, the more current the LEDs draw, the bigger the capacitance has to be. Start with a minimum capacitance 470 uF for 20W and work your way up into the the thousands for 100Watt LEDs. If you notice flicker in the light you need more capacitors. Under load, the voltage is a little lower, and perfect for running the LEDs at full brightness with a safety margin. You could place a diode in series with the LED if you wish to lower the voltage further for a greater safety margin, and make them last longer. Now you can replace halogens without having to buy plug-packs or modifying anything, Enjoy! PS:- The circuit can be used anywhere there is an AC voltage that needs to be stepped up, eg amplifier power-supplies
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