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

krishna
Transformerless Power Supply
Friday, April 25, 2008 6:50:17 AM
can u give us design for transfomerless power supply 230V ac to 24V dc
Corey
115VAC to 24VDC ~6A Transformerless Power Supply?
Thursday, April 24, 2008 5:10:11 PM
looking for a schematic for a resticked space power supply... and as we all know, a transformer to handle this would be huge and too large for the space available in my project... any help would be great... thanks...
Moin-ud-din
Transformerless Power Supply
Thursday, April 10, 2008 4:57:17 AM
Sir, thanks i read your design tips. It was a nice document. I want to design a transformerless 200mA power supply kindly tell me how much value of capacitor i could used. regards, Moin-ud-din
tanH thiagarajan
230vac-24vdc-12vdc Transformerless Power Supply
Wednesday, April 09, 2008 10:55:33 PM
i need circuit diagram of a tranformerless power supply. input 230vac reduce to 24vdc and reduce it again to 12vdc and again to 5vdc. plz send it to my email.. i'm glad if someone help me..
tanH thiagarajan
240vac- 24vacTransformerless Power Supply
Saturday, April 05, 2008 11:40:18 AM
i would like to know more about this 240vac-24vac transformerless power supply.. if can i want it's circuit diagram.. i'm glad if someone help me..thank you..
poojaonymous
Transformerless Power Supply
Wednesday, March 26, 2008 6:22:22 AM
Can anyone help me out with 110 to 230VAC supply for transformerless with output of 6VDC 500ma circuit for battery charging. plz reply to my mail.
Mike
Transformerless Power Supply
Monday, February 25, 2008 11:05:28 AM
Please help me to design a 120vac to 12v dc 300mA tramsformerless power supply. Any schematic diagram.
chibuzo nnonyelu
Transformerless Power Supply
Saturday, February 23, 2008 9:01:46 AM
Please can I use this circuit on 220V AC power supply
HC
Transformerless Power Supply
Friday, February 15, 2008 2:23:05 AM
i need a transformerless power supply for 240vac input and 24vdc 1amp output. can somebody help me. thanks. best regards. HC
Nuno
Transformerless Power Supply
Monday, February 04, 2008 12:17:13 PM
Just to remember all that this kind of circuit works by capacitive reactance (C1) and is very limited in terms of current that it can supply. The maximum supplied current can be calculated by Ohm's law I = V/R, where I: represents current, V: voltage (mains in this case), and R: resistence (capacitive reactance in this case Xc). Where Xc=1/(2.Pi.f.C), Xc: capacitive reactance; Pi: 3.14; f: frequency; C: capacitance. As one can see, to increase current is necessary decrease the capacitive reactance (Ohm's Law), and for that we need to increase capacitance (capacitor size). Above 20-30mA this is no longer feasible because the capacitor becomes too big and expensive, so above these currents it is better to choose other method of conversion (Transformer or SMPS- switch mode power supply ).
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