Power supply without the power

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Ian0

Joined Aug 7, 2020
13,132
So, are you saying that all transformerless power supplies, including those sold on the open market, are deadly?
Depends what you do with it. Guns are safe of no one pulls the trigger.
It is perfectly safe provided that every part of it, including the low voltage output is touch-proof and insulated to the same standards as mains live, because every part of it is at mains live potential.
 

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ricebridge

Joined Jun 24, 2017
30
Depends what you do with it. Guns are safe of no one pulls the trigger.
It is perfectly safe provided that every part of it, including the low voltage output is touch-proof and insulated to the same standards as mains live, because every part of it is at mains live potential.
Which is exactly my intention, it goes without saying.

So, is there anybody who could please answer my question?
 

timm27

Joined Dec 11, 2020
27
Which is exactly my intention, it goes without saying.

So, is there anybody who could please answer my question?
To create a transformerless 17V output from 230vAC you will need a switch mode design, but without isolation it will likely be dangerous! Most designs will use a 'buck' design. Mains powered LED lamps use this approach, but of course the 230v is entirely enclosed in the lamp base. Designs are proprietary so you probably won't get the answer here.
 

Lo_volt

Joined Apr 3, 2014
370
The supply you are working on is only good for low power, i.e. a few mW. As nsaspook noted, you are dropping a lot of power across the components because it is so inefficient.
It is possible to build a switching supply that will give you 17 volts at more than 1 amp. It won't be cheap nor will it be simple. As others have said, it will definitely be cheaper to buy an off the shelf product.
 

Thread Starter

ricebridge

Joined Jun 24, 2017
30
It is possible to build a switching supply that will give you 17 volts at more than 1 amp. It won't be cheap nor will it be simple. As others have said, it will definitely be cheaper to buy an off the shelf product.
I’m not interested in cheap or simple. I’m interested in the design as such.
 

Danko

Joined Nov 22, 2017
2,169
I’m not interested in cheap or simple. I’m interested in the design as such.
Transformerless power supply calculator

"This tool calculates output parameters of a transformerless power supply where a capacitor is used to drop the voltage.
The formulas and information come from Microchip application note AN954, written by Reston Condit.

The capacitor C1 must be X2 type capacitor.

Warning: transformerless power supplies provide no isolation from mains power, and are very dangerous. You must use isolation transformer whenever you want to connect anything, such as scope, DVM, or any other external equipment to the circuit. Even with isolation transformer high voltages are present, be very careful."

1742393063853.png
ADDED:
The schematic you show is half bridge and outputs 1/2 the current for a value of Capacitor. We are trying to get more power so use a full wave version.
See AN954:
1742394965427.png
 

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ronsimpson

Joined Oct 7, 2019
4,702
This tool calculates output parameters of a transformerless power supply where a capacitor is used to drop the voltage.
The schematic you show is half bridge and outputs 1/2 the current for a value of Capacitor. We are trying to get more power so use a full wave version.
----edited------
Here is a full wave version. I find the 24V Zener has a soft knew. It steels power even with a 20 ohm load. The output cap is much larger because there was too much ripple.
1742395108955.png
 
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Thread Starter

ricebridge

Joined Jun 24, 2017
30
Thank you. These are essentially the designs I have tried to emulate (sans the transistors, forget about them for now.) So why isn't this very bad engineering? And why won't I get more than a few volts out of it?
 

LowQCab

Joined Nov 6, 2012
5,101
Because the Components that You need are quite large.
A top-notch, completely Isolated, commercial Switching-Power-Supply
in a sealed "Bloc" Package is only ~20-bucks from DigiKey as per my previously provided link.

This is the type of solution You should be looking for ...........

I hope You don't wind-up killing yourself or someone You care-about.
But your foolish bravado about "knowing what you're doing" might just do the trick.

Sorry, but I just don't believe You when You say You just want to "learn how to do it".
You'll be laying a deadly-booby-trap for some unsuspecting soul,
then you'll have to live with it for the rest of your Life.
.
.
.
 

Ya’akov

Joined Jan 27, 2019
10,240
Capacitive Dropper type power supples were previously a prohibited subject here on AAC. The danger they pose was the reason. The rules were changed to provide and opportunity to discuss them in a context where the danger was minimal and the circuit was useful.

Unfortunately, this thread has neither of these attributes. Using a transformer-less supply of the capacitive dropper type with such a high power output is not safe nor is it useful. It is not a good example to others who might read the thread and ignore the safety warnings, nor is it a useful choice for the TS if he intends to apply it.

For these reasons, I am closing the thread to further replies.

[MODERATION]
 
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