Normally, transformers are used to step down voltage from high AC voltage to a lower level before converting it to DC. But there is a simple way to convert 220V AC directly to approximately 12V DC without using a bulky transformer, using a capacitor dropper circuit
Components Required
- 225 k, 450V rated capacitor (to limit current) ►https://amzn.to/38nPr3u
- Resistors: 100 kΩ (2 W), 1 MΩ (for current limiting and discharging) ►https://amzn.to/3mJNlmS https://amzn.to/3joDh0n
- 470 µF capacitor (for smoothing output DC) ►https://amzn.to/3gFBX7y
- Zener diode (to regulate voltage) ►https://amzn.to/2Y29hzf
- Zero PCB (project board) ►https://amzn.to/3zsixuq
- 2-pin screw connector for mains input ►https://amzn.to/3zulsCG
Circuit
How It Works
This circuit uses a different approach than a traditional power supply, primarily relying on an X-rated capacitor to limit the current and drop the voltage.
- Capacitive Reactance: The high-voltage capacitor (225 k, 450V) acts like a tiny resistor for AC current, limiting the amount of current flowing into the circuit without dissipating much power as heat (unlike a resistor).
- Current Limiting Resistor: The 100 kΩ resistor prevents sudden inrush current and limits current further for safety.
- Rectification and Voltage Regulation: The current passing through the capacitor and resistor is AC but reduced. Using diodes (or a diode bridge) and a Zener diode, this AC is converted to DC and regulated to a stable 12V output.
- Smoothing Capacitor: The 470 µF capacitor smooths out the ripples in the DC output so that you get a steady voltage.
- Safety Resistor (1 MΩ): This resistor discharges the capacitor safely when the circuit is off, preventing electric shock from stored charge.
Important Safety Notes:
- This method is low-cost and compact but is not isolated from mains voltage. It can be dangerous if mishandled.
- Use insulation and work carefully to avoid shocks.
- This circuit is best for low-current applications (like powering small lamps or electronics), not heavy loads.
This transformerless power supply is an interesting way to get low-voltage DC from high AC mains in constrained spaces, but please emphasize safety clearly if you share this project.
Construction and Safety
⚠️ Safety Warning: This circuit connects directly to high-voltage AC mains (220V) and is extremely dangerous to touch or handle while plugged in. It is not electrically isolated and should only be constructed by experienced individuals and placed in a well-insulated enclosure.
Watch the full video tutorial here: How to convert AC to DC without transformer | convert from 220v AC to 12 DC with explanation