Transformerless Power Supply


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I have received a few emails asking for a transformerless power supply. Here is such a supply. This supply uses no heavy step down transformer and has an extremely low parts count. The circuit can be built very small and can supply small currents for small projects. The major downfall of this supply is that it is not isolated from the AC line and can only supply small currents.

Schematic

Schematic for Transformerless Power Supply

Parts

Part
Total Qty.
Description
Substitutions
C110.39uF 250V Capacitor
C21220uF 25V Electrolytic Capacitor
D111N4741 11V Zener Diode (See Notes)
BR111 Amp 200V Bridge Rectifier
MISC1Line Cord, Board, Wire, Case

Notes

  1. The value of C1 can be increased to increase the amount of current the circuit can supply. With the values shown, the circuit can supply up to about 15mA. Remember to increase the size of C2 also.
  2. A different value can be used for D1 to increase or decrease the voltage as needed.

  3. Please note that this circuit is not isolated from 120VAC. Because of this, the circuit must be treated with caution and encosed at all times. Do not work on the circuit (or any other circuits attached to it) when it is plugged in.
  4. You may want to add a resisor in series with C1 to limit current if the circuit is plugged in and the mains is at its full voltage.
  5. If you are running the circuit from 220VAC, then use a capacitor rated at greater than 400V for C1.
  6. If you want isolation from the AC line, you can connect up a small isolation transformer at the inputs of the circuit. Small 600ohm:600ohm audio transformers work nicely.

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Comments

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anonymous
Transformerless Power Supply
Tuesday, November 29, 2011 10:07:55 AM
could this circuit be possible in a photo switch streetlights?
XN
Transformerless Power Supply
Sunday, November 13, 2011 9:09:36 PM
is it possible to connect an LM317 after the bridge rectifier for the transformerless power supply...like this one on your page?
anonymous
Transformerless Power Supply
Sunday, November 13, 2011 9:18:22 AM
1. Please indicate polarity of C1. All 400v capacitors i find are rated + and - on the pins. C2 polarity is clear. 2. I am trying to convert from 220v ac to 30v dc supply, can i use 30V rated Zener diode and 45v rated C2 ?????
frq
Transformerless Power Supply
Tuesday, January 04, 2011 10:23:59 PM
I am searching for a transformerless power supply with high current rating. Output-12V,and high current rating
anonymous
Transformerless Power Supply
Wednesday, September 15, 2010 4:10:28 AM
hi. is it safe if 10th std make this circuit and show its working for a science woking model fair.
anonymous
Transformerless Power Supply
Sunday, September 05, 2010 3:09:13 AM
i, I would like to know what would happen if (line voltage : 220 - 240 v 50 Hz) : 1 what modifications would be neccessary to protect the circuit conditions. Thank you!
anonymous
Transformerless Power Supply
Thursday, April 22, 2010 3:00:36 PM
hi, could you pls tell me how much voltage does this curcuit supply ? thanks
Sundeep
Transformerless Power Supply
Sunday, February 07, 2010 6:35:47 AM
Hi, I would like to know what would happen if (line voltage : 220 - 240 v 50 Hz) : 1 The voltage drops to 120v 50Hz. 2 The circuit is switched on at line voltage 300v 50 Hz. what modifications would be neccessary to protect the circuit in both conditions. Thank you!
Ehet
Transformerless Power Supply
Friday, December 11, 2009 9:31:29 AM
Build this power supply in a case
camil
Transformerless Power Supply
Wednesday, September 23, 2009 7:32:44 AM
dear techineer, pls i would like to have detailed explanation on why each component is used esp. C1 and C2 thanks
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