# Making power supply without power integration ic

#### idrbur

Joined Jan 11, 2018
43
I am trying to build a SMPS without a power integration IC(e.g tny267) . I'd actually like to build the one in image.but I am not good at drawing schematic by tracing the connections. I searched online but couldn't find anything. So , if anyone could help me with a schematic I would really appreciate that .
the bigger transistor on the board is MJE13003, the smaller one is SS9014 and the 4 pin ic on side a rectifier.
The red arrows indicate mains connection points and blue ones indicate output point

#### AlbertHall

Joined Jun 4, 2014
12,071
The problem here is the transformer.
You might be able to find a transformer supplier/manufacturer that have example circuits using their transformaers.

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#### Ramussons

Joined May 3, 2013
1,271
Search for discrete smps transformer in Digi-key website

#### AlbertHall

Joined Jun 4, 2014
12,071
Search for discrete smps transformer in Digi-key website
I get '0 results' for that search in both the US and UK Digikey sites?

#### ronsimpson

Joined Oct 7, 2019
2,156
This power supply looks dangerous.
Where is the primary to secondary spacing? On the PCB and I don't see it in the transformer.
The PCB spacing around the transistor looks too small.

#### atferrari

Joined Jan 6, 2004
4,629
I'd actually like to build the one in image.but I am not good at drawing schematic by tracing the connections. I searched online but couldn't find anything.
The one you show does not present much of a difficulty; even have the traces explicitly staring at you.

You need paper, pencil, eraser, multimeter, patience and decision of being not lazy.

Even if you do not have the PCB with traces openly at sight, just draw the mimic distribution of components identifying pins (numbering them is better).

The idea is to identify what pins connect to what other ones. All wrt to all. Method, that is all you need.

First thing: identify ground (I call it always common for myself) is what will help produce an idea of the circuit in your mind.

Second: identify power rails.

I did this to get a full circuit of an LX750 IIRC EPSON printer. It allowed me to conduct a nice brain surgery (microprocessor replacement) to convert it in a basic coil winding machine.

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#### idrbur

Joined Jan 11, 2018
43
The one you show does not present much of a difficulty; even have the traces explicitly daring at you.

You need paper, pencil, eraser, multimeter, patience and decision of being not lazy.

Even if you do not have the PCB with traces openly at sight, just draw the mimic distribution of components identifying pins (numbering them is better).

The idea is to identify what pins connect to what other ones. All wrt to all. Method, that is all you need.

First thing: identify ground (I call it always common for myself) is what will help produce an idea of the circuit in your mind.

Second: identify power rails.

I did this to get a full circuit of an LX750 IIRC EPSON printer. It allowed me to conduct a nice brain surgery (microprocessor replacement) to convert it in a basic coil winding machine.
I want to do that but the thing is rhe circuit connects 220v mains and I am not that experience. I just don't wanna blow thing up

#### idrbur

Joined Jan 11, 2018
43
The problem here is the transformer.
You might be able to find a transformer supplier/manufacturer that have example circuits using their transformaers.
The supply I showed you in image is damaged so I was just remove the transformer from it

#### AlbertHall

Joined Jun 4, 2014
12,071
I was searching on the digikey site and got no hits - curiouser and curiouser.

#### ronsimpson

Joined Oct 7, 2019
2,156
I find "self oscillating" power supplies are hard to design. They are very dependent on transistor gain, transformer inductance, transformer saturation level, resistor tolerances, capacitor values, temperature, and other unknows factors. I find the prototype will work but production will not. When production does work it will stop when a new batch of transistors show up. The regulation is poor.

I try not to make them. I design power supplies. When I need a 12V 500mA supply I go to the "used junk" store. They have a huge bin for $0.50 each. I have a huge fin. Amazon has a set of five 12V 1A supplies for$19.99 new. Now I see I can get one for $11, two for 11.95, three for$13...........