Simple Bench Power Supply 10A

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ortiko

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Hello this is my first post and thought to start with a project...

I have started and almost finish the PS i will present below
Main thought is to make the simplest circuit i could find and have a 10A power supply for my lab needs.

Any ideas or suggestions to make it better are welcome

Will start with circuit that is not mine design.

That was found at

**broken link removed**

 
I had the transformer and thought to make something with it
and i did...





 

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I was just reading the datasheet for the LM350.... There is a cracking design for a 0 ~ 10 amp bench supply using 4 in parallel.

Watching with interest...
 
Very nice, but you are going to have problems.

36v AC input, when rectified and smoothed by the capacitor will give you about 50 volts DC.

The 10,000uF electrolytic is rated at 40v
The L200 regulator is rated at 40v MAX input.
You are over running this devices.

When you draw current from this PSU, the pass transistors will get very hot as they will be dissipating:

Dissipation = (50volts - OutputVolts) x OutputCurrent Watts

Let us know how it works when you have finished it.

JimB
 
After that i connected everything to test and the test rezualts were very disapointing...

with 4A load in about 30sec the MJ15003 gets very HOT

Only the transistors get very hot.
Not the L200 either the emitter resistor.

Except the above problem with a very slight movement of the potensiometer the voltage changes very fast.
Maybe i have made a mistake with connections but i have double checked it
 
I found out by searching the circuit that i have a mistake with connections of R4
As written from the author R4 and R2 top i thought this must be connected parallel....

Below i have drawn the connection and will make changes this afternoon



Hope this will solve the very short changes of volts with very small movement of the potentiometer.
 
ortiko said:
After that i connected everything to test and the test rezualts were very disapointing...

with 4A load in about 30sec the MJ15003 gets very HOT
Click to expand...

Didn't you read post #5? - simple calculations show it's going to run VERY hot, and only two pass transistors and 'small' heatsinking isn't going to work.

I'm also surprised that C1 hasn't 'exploded' yet, as it's much too low a rating.
 
Yes i did but just whantet to test it first
I will add two mj15003 and bigger heatsink

Don't be surprised because i used 63v 10000uf cap...
and also explosions occur when you connect wrong polarity on the capacitor
My connections on this capacitor are ok
 
35-40 years ago I did this project. Different parts. Too much heat!
My transformer had a center tap. I added a high/low switch. (10A)
If the switch is in the (high) the circuit is the same as yours.
If the switch is in the (low) the voltage on C1 is 1/2 so the voltage across the transistors is lower.
 
I dont think my transformer has this option




It is 30-0-30 and have done the bellow to mak it 0-30

 
I have a linear power supply manufactured by Harrison Labs, which was purchased by HP. It was called a "Fixed voltage power supply, selectable 0-32 V, 10A"

The heat sink is huge. Fan cooled. Heavy. You have to change the transformer taps based on the voltage range you want.

It did have fold back current limiting. Shorted leads, would result in 10A at nearly no voltage.

Some thing very similar to this one: https://gsaauctions.gov/gsaauctions/aucdsclnk?sl=71QSCI13388026

The front Panel consists of a power switch, lamp, Fuse(s), 2 large meters, binding posts, and a min-max recessed screwdriver adjust. Min and Max pots are accessible through the case top.
 
Last edited:
I decided not to use the big transformer and use this one at below pic.
It is 24V and i have the desired voltage. Not more than 32V dc





Tested again with this transformer and everything ok.

I found out that one of the transistors get very hot when i drain 4A and the other one is barely hot...
The Mj15003 connected to R3 gets very hot

Is this normal?
 
Those transistors should really be matched for Hfe. Take a look at the voltages across the emitter resistors. If the Hfe is vastly different, you could see this problem.
 
ortiko said:
I found out that one of the transistors get very hot when i drain 4A and the other one is barely hot...
The Mj15003 connected to R3 gets very hot

Is this normal?
Click to expand...

Probably - you can balance them a little better by increasing R2 and R3, try 0.33 ohms instead of 0.2 ohms.

However, it doesn't really matter - as one gets hot the other will start to take up the load - that's how the balancing works.
 
I am back with some updates...

Want to make it a bit modern PS and used the transistors below.
2sc 5200

Bought some new heatsink for them...



And started installing them





Will use this for the fan...


Very soon i will post testing resaults...
 
Nigel Goodwin said:
Probably - you can balance them a little better by increasing R2 and R3, try 0.33 ohms instead of 0.2 ohms.

However, it doesn't really matter - as one gets hot the other will start to take up the load - that's how the balancing works.
Click to expand...


I made this significant changes with the toshiba transistors and tested the PS again but the test results were almost the same as with MJ's...
one transistor connected to R3 starts to get very hot with load connected and the other is not hot
Have some pics with the temp of eatch 2sc5200



and the other connected emiter to R2



The voltage of the one that gets very hot on emiter is 13.77V

and at the other is 14.10V



The resistors on emiters are 15W 0.22Ohm
 
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