Comments on: Transformerless Capacitor Dropper Power Supply

By: BenUs

BenUs — Sun, 08 May 2022 04:44:06 +0000

hi, i want build 12v 10amp power supply, but based calculation above, capacitor i must use is ridiculous
V = I x R
R = V / I
R = (230-0,7-12) / 10
R = 217,3 / 10
R = 21,7 ~~ = 22ohm == Xc1

Xc1 = 1/(2πfC)
C = 1/(2 π f Xc1)
C = 1 /(2 x 3,14 x 50 x 220)
C = 1 / 69080
C = 0,00001447596F
C = 14.47596uF
see?? Ridiculous! There no mylar, MKM, MKP with value above 2uF

But i am looking at computer PSU, accumulator charger any powersupply/charger/adaptor with high current and they only use 100n,680n,1uf, how can they increase current??

By: Steve

Steve — Thu, 03 Dec 2020 15:51:00 +0000

From an electrical safety point of view it is extremely dangerous to use a transformerless supply, because there is no isolation between the mains input and the DC output.
The size of transformer required for these low current projects is very small and worthy of the expense.
Please do not enclose this circuit in a metal box – that is too risky.
Items like this need to be enclosed in an insulating container made of ABS or better still polycarbonate to provide better mechanical protection.

By: Paul Robbins

Paul Robbins — Mon, 02 Nov 2020 06:36:45 +0000

In reply to Chand Sayyad. Put a 240R load on it

By: Ligo George

Ligo George — Sun, 11 Oct 2020 15:27:54 +0000

In reply to TheTranscendentian. Capacitor is a reactive component, it won't dissipate energy like a resistor.

By: TheTranscendentian

TheTranscendentian — Sun, 27 Sep 2020 22:39:50 +0000

That’s a cool circuit. I have wondered weather voltage dropping with an AC capacitor would dissipate lots of waste heat and be inefficient.

So, if you can get 40mA out of this circuit, does that mean the input mA is around 2.5mA and does this circuit have around 80% voltage conversion efficiency?

By: Ligo George

Ligo George — Fri, 10 Jul 2020 01:25:45 +0000

In reply to Sk Khoo. I am not an expert in this but I think we should be good using RMS value. With peak we will get the maximum value at a particular instant, similarly there is a minimum value also. So I think while using RMS value we will get continues average power dissipation.

By: Sk Khoo

Sk Khoo — Wed, 08 Jul 2020 11:58:34 +0000

230V is RMS value, the V peak could go up to 230 X 1.4142 = 325V , is not you VR1 voltage too low ?

By: Ligo George

Ligo George — Wed, 22 Apr 2020 11:22:17 +0000

In reply to Surendra Rahalkar. It will still give you approximately 12V, since we are using zener diode regulator.

By: Surendra Rahalkar

Surendra Rahalkar — Wed, 22 Apr 2020 07:16:40 +0000

Dear Sir,
What will happen if Load is decreased ( Open load resistance)?

By: Ligo George

Ligo George — Sun, 16 Feb 2020 06:46:06 +0000

In reply to Chand Sayyad. How did you arrived at value 2.2uF ?