Transformerless Power Supply

Author	Views	Views Today	Rank	Comments
	162,068	61		107

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

Parts

Part	Total Qty.	Description	Substitutions
C1	1	0.39uF 250V Capacitor
C2	1	220uF 25V Electrolytic Capacitor
D1	1	1N4741 11V Zener Diode (See Notes)
BR1	1	1 Amp 200V Bridge Rectifier
MISC	1	Line Cord, Board, Wire, Case

Notes

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.

A different value can be used for D1 to increase or decrease the voltage as needed.

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.

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.

If you are running the circuit from 220VAC, then use a capacitor rated at greater than 400V for C1.

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.

Related Circuits

Comments

Add A Comment

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

anonymous Transformerless Power Supply Saturday, September 19, 2009 4:19:42 PM

it seems that a resistor must be in series with c1 but in this circuit it is not .Please tell me is this resistor need or no if it is how determine its value?

John Kandankerry Transformerless Power Supply Tuesday, July 28, 2009 10:59:56 PM

Very neat and compact cct. However, I want to design a transformerless cct to supply 120mA DC at 42 V to a cluster of LEDs. Pl. advise how I should alter/ redo this cct. Thanks John

Amit Singh Transformerless Power Supply Thursday, July 16, 2009 5:18:57 AM

I want to know sumthing. how do i know C1 or C2 values? if i want to make other non transformer circuit? i have downloaded a software for circuit designing. from http://electronis-lab.com . it designs me circuit and give me uf value but it do not specify VOLT of C1 or C2. how do i know this? the link is to download ELECTRONIC CIRCUIT DESIGN and it only 168 kb. " http://www.electronics-lab.com/downloads/schematic/index.html "

anonymous Transformerless Power Supply Friday, June 19, 2009 3:34:01 PM

renhe: this circuit can supply up to about 15mA and halogen bulb demand 100/12*1000 = 8333mA.

anonymous Transformerless Power Supply Sunday, June 07, 2009 6:06:14 AM

Where standby generators are required to take over, in case of mains supply failure, transformerless supply is used to operate relays. These relays switch over the AC load from the AC mains to the generator and back as required. But the relay coils work on 12 or 24volts DC. These relays are fitted on to the AC Mains supply panel which is accessible to only trained personnel. So the risk is as much as handling the mains equipment only. In such a situation without increasing the risk, the cost benifit is very subsatntial for the equipment manufacturer!

neonlight Transformerless Power Supply Wednesday, May 20, 2009 6:37:12 PM

Techineer, First of all great site and thank you for the info. (1)There is one part i dont understand though, why must you place the resistor between C2 and the cathode? And not in series with the capicitor, i may be tired or missing the point but could you please explain the reason? (2)Oke i have got another question can i calculate the resistor simply with u/i=r where U for Europe would be 230 AC and for the US 120 AC and I the current is U/R=I --> (1.4... * volts_ac)/2ðfC1 ? thanx, neonlight

renhe Transformerless Power Supply Saturday, February 14, 2009 11:06:06 PM

i want to ask anybody if the supply from this power supply can use to halogen bulb 100w 12volts? if can used this supply on this bulb? thank you..

anonymous Transformerless Power Supply Wednesday, December 31, 2008 12:00:28 AM

i have already made this transformer less power supply, but i have lot of question about this. all of them have been asked by other friends here. i also want to answer of these question, tell what i have to do find the answer.

Techineer Transformerless Power Supply Monday, December 29, 2008 11:07:24 PM

C1 is being used as a current limit and voltage dropping device. The reactance of 0.39 uF capacitor at 60 Hz is 6800 ohms, but it uses no power and does not heat up like a resistor would. The output of this supply will vary widely as more current is drawn from the output, as more voltage will be dropped across C1. To calculate the output voltage, the load current must be known.

The last 10 comments are currently shown. Show All Comments. Add A Comment

If you would like to leave a comment, you can do so using the form below. Comments can be things like suggestions, successes or failures, improvements, similar circuits, error reports, an answer to a previous commenter's question, or anything in between. However if you would like to ask a question it is suggested that you use the forum instead. The forum provides a more robust environment for discussion.

Important: If you post a technical question here, there is no guarantee it will be answered. All technical questions should be posted to the forum. The owner of this site generally does not answer questions in comments.

All comments are subject to approval before they are displayed here, so your comment will not appear immediately. This is done mainly to prevent spam and other abuse. If you wish to remain anonymous, simply enter "anonymous" for your name and/or email.

Name:
Email:
Subject:
Comments:
Anti Spam Code:	Please enter the exact text shown in the image above into the box below. Browser cookies must be enabled to comment on circuits.

Privacy Policy

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
anonymous	Transformerless Power Supply	Saturday, September 19, 2009 4:19:42 PM
it seems that a resistor must be in series with c1 but in this circuit it is not .Please tell me is this resistor need or no if it is how determine its value?
John Kandankerry	Transformerless Power Supply	Tuesday, July 28, 2009 10:59:56 PM
Very neat and compact cct. However, I want to design a transformerless cct to supply 120mA DC at 42 V to a cluster of LEDs. Pl. advise how I should alter/ redo this cct. Thanks John
Amit Singh	Transformerless Power Supply	Thursday, July 16, 2009 5:18:57 AM
I want to know sumthing. how do i know C1 or C2 values? if i want to make other non transformer circuit? i have downloaded a software for circuit designing. from http://electronis-lab.com . it designs me circuit and give me uf value but it do not specify VOLT of C1 or C2. how do i know this? the link is to download ELECTRONIC CIRCUIT DESIGN and it only 168 kb. " http://www.electronics-lab.com/downloads/schematic/index.html "
anonymous	Transformerless Power Supply	Friday, June 19, 2009 3:34:01 PM
renhe: this circuit can supply up to about 15mA and halogen bulb demand 100/12*1000 = 8333mA.
anonymous	Transformerless Power Supply	Sunday, June 07, 2009 6:06:14 AM
Where standby generators are required to take over, in case of mains supply failure, transformerless supply is used to operate relays. These relays switch over the AC load from the AC mains to the generator and back as required. But the relay coils work on 12 or 24volts DC. These relays are fitted on to the AC Mains supply panel which is accessible to only trained personnel. So the risk is as much as handling the mains equipment only. In such a situation without increasing the risk, the cost benifit is very subsatntial for the equipment manufacturer!
neonlight	Transformerless Power Supply	Wednesday, May 20, 2009 6:37:12 PM
Techineer, First of all great site and thank you for the info. (1)There is one part i dont understand though, why must you place the resistor between C2 and the cathode? And not in series with the capicitor, i may be tired or missing the point but could you please explain the reason? (2)Oke i have got another question can i calculate the resistor simply with u/i=r where U for Europe would be 230 AC and for the US 120 AC and I the current is U/R=I --> (1.4... * volts_ac)/2ðfC1 ? thanx, neonlight
renhe	Transformerless Power Supply	Saturday, February 14, 2009 11:06:06 PM
i want to ask anybody if the supply from this power supply can use to halogen bulb 100w 12volts? if can used this supply on this bulb? thank you..
anonymous	Transformerless Power Supply	Wednesday, December 31, 2008 12:00:28 AM
i have already made this transformer less power supply, but i have lot of question about this. all of them have been asked by other friends here. i also want to answer of these question, tell what i have to do find the answer.
Techineer	Transformerless Power Supply	Monday, December 29, 2008 11:07:24 PM
C1 is being used as a current limit and voltage dropping device. The reactance of 0.39 uF capacitor at 60 Hz is 6800 ohms, but it uses no power and does not heat up like a resistor would. The output of this supply will vary widely as more current is drawn from the output, as more voltage will be dropped across C1. To calculate the output voltage, the load current must be known.