Transformer Less AC to DC Power Supply Circuit Using Dropping Capacitor

Production of low voltage DC power supply from AC power is the first and most important challenge faced by many electronics developers and hobbyists. The straight forward technique is the use of a step down transformer to reduce the 230 V or 110V AC to a preferred level of low voltage AC.

But Circuitsgallery comes with the most appropriate method to create a low cost power supply by avoiding the use of bulky transformers. Yes, you can construct power supply for your development without a transformer. This circuit is so simple and it uses a voltage dropping capacitor in series with the phase line.

Transformer less ac to dc power supply circuit is also called as capacitor power supply circuit. It can generate 5V, 6V, 12V 150mA from 230V or 110V AC by using appropriate zener diodes.

Circuit Diagram of Transformer Less AC to DC Power Supply Circuit

Components Required for Capacitor Power Supply Circuit

1. Resistors (470kΩ, 1W; 100Ω)
2. Capacitors (2.2µF, 400V, X rated; 1000µF, 50V)
3. Bridge rectifier (1N4007 diodes x 4)
4. Zener diode (6.2V, 1W)
5. LED (Optional)

Working of Transformerless Capacitor Power Supply

• This transformer less power supply circuit is also named as capacitor power supply since it uses a special type of AC capacitor in series with the main power line.
• A common capacitor will not do the work because the mains spikes will generate holes in the dielectric and the capacitor will be cracked by passing of current from the mains through the capacitor.
• X rated capacitor suitable for the use in AC mains is vital for reducing AC voltage.
• A X rated dropping capacitor is intended for 250V, 400V, 600V AC. Higher voltage versions are also obtainable. The dropping capacitor is non polarized so that it can be connected any way in the circuit.
• The 470kΩ resistor is a bleeder resistor that removes the stored current from the capacitor when the circuit is unplugged. It avoid the possibility of electric shock.
• Reduced AC voltage is rectifiered by bridge rectifier circuit. We have already discussed about bridge rectifiers. Then the ripples are removed by the 1000µF capacitor.
• This circuit provides 24 volts at 160 mA current at the output. This 24 volt DC can be regulated to necessary output voltage using an appropriate 1 watt or above zener diode.
• Here we are using 6.2V zener. You can use any type of zener diode in order to get the required output voltage. 

Pinouts of Capacitor, Diode, Zener Diode and More

Conclusion

Do not touch at any points in the transformer less ac to dc power supply circuit. Because some points are at mains potential. Keep away from touching the points around the dropping capacitor to prevent electric shock, even after switching off the mains.

Great care should be taken to construct the circuit since there is no isolation between the mains and our circuit. Adequate spacing must be given between the components.