About 8566 readers of this Blog visited the transformer less power supply article posted and there are queries regarding the design of the circuit to power different types of gadgets. So one more circuit is posted here that can give 12 volt DC at 300 milli amperes current. This circuit uses AC capacitor to drop the AC power to generate 12 volt DC.
The main element of this power supply is three 1 uF 400 Volt X rated capacitors C1 through C3. Each 1 uF capacitor can give 100 mA output current. Since the three capacitors are connected parallel, 300 milli ampere current will be generated. The 1uF capacitor drops the 230 volt AC to around 50 to 60 volt AC depending on the AC input voltage. Resistor R1 is provided to bleed the stored current in the capacitors when the circuit is unplugged. Without R1, the capacitor retains around 400 volts for many days, which can give a fatal shock. Resistor R2 is also important to restrict the inrush current at power on. The 50-60 volt AC from the capacitor is rectified by the full wave rectifier formed of D1 through D4. After rectification, the DC will be regulated to 15 volt by the Zenerdiode. Resistor R3 limits the Zener current. By changing the value of Zener, output voltage from 6 volts to 30 volts can be produced. LED is provided to indicate power on status. This LED will consume 2 volts, so that output will be around 12-13 volts.
12 Volt Capacitor Power Supply
Note: This circuit has no galvanic isolation from the mains. So any short circuit can destroy the capacitor and the gadget connected to it. Do not use this circuit to power costly gadgets. It is better to add a safety fuse and MOV at the input to protect the power supply from damage.
Caution: This circuit is extremely dangerous if handled without precautions. Most points are at mains lethal potential and can give fatal shock. So do not try this circuit unless you are competent to handle high voltages. Do not touch any points when the circuit is connected to mains. Always enclose the circuit in a shock proof case.