testbench power supply

R!f@@

Joined Apr 2, 2009
9,725
I don't understand why you are using opamps as current sense when u have current limit given via resistors.

If u design it can u explain the operation.

U need to simulate the circuit using simulator. I don't thing any one here have enuf time to draw the circuit and simulate it for u.

You have to wait for a while for a proper response. As for me I need u to explain the opamps together with the PIC part.

Have a look at here post 23. Which I used to work with, it's not complete though.
 
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blind2_man

Joined May 12, 2008
33
IC2A measure the current I_SEMSE and this is the input on ADC input. The output is also compared via IC2B with I_OUT generated by microcontroller on the PWM output, in this way you can setup the current limit by digital command.
R20 and R34 are the potentiometers to give the U target and I target, measured by 2 ADC inputs.
IC3A give you the digital reference setting for U.
I have simulated parts of this schematic. I looking for somebody to , just have a look on the schematic , I if he sees something is out of place....
 

bountyhunter

Joined Sep 7, 2009
2,512
Next step will be to make a PCB.
.
Actually, the next step is to build the prototype (breadboard) and fix all the things that don't work right.

I'm not understanding why you would do a design based on the LM723 which is a 35 year old part. If you are ging to use discrete op amps, you can use them for voltage and current amps so the 723 is redundant. You can also use a much better reference than the 723 has like an LM4041.

Attached is a basic lab type linear reg design with both voltage and current control loops.
 

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blind2_man

Joined May 12, 2008
33
@bountyhunter First prototipe was a Lm723 power supply , then I make a second one and add pic and operationals to measure current and setup the voltage target and current target. If I can remove LM723 will be great.
This is the third prototipe and the current limiting has not been proven yeat, also the second prototipe had a 4x7dig display, now it has been replaced with LCD 2 rows.
I will come back with update schematic.
 

bountyhunter

Joined Sep 7, 2009
2,512
@bountyhunter First prototipe was a Lm723 power supply , then I make a second one and add pic and operationals to measure current and setup the voltage target and current target. If I can remove LM723 will be great.
This is the third prototipe and the current limiting has not been proven yeat, also the second prototipe had a 4x7dig display, now it has been replaced with LCD 2 rows.
I will come back with update schematic.
Forgive me if this is a dumb question: are you saying you have already built up three operating prototype boards?

As to:

If I can remove LM723 will be great.
You certainly can. The schematic I attached is a complete generic linear reg with both voltage and current control loops (current limiting is included). The 723 is a low performance chip to build cheap power supplies.
 

Thread Starter

blind2_man

Joined May 12, 2008
33
First prototype was started with this:
power.JPG
Second one is very close to schematic posted, major diference is I use 7seg display and the current limiting has not been used/tested.
The 3th protoptype is this one, trying to activate current limiting.
Also the transformer has been replaced from 35W(1A sec) to 100W(4A secondary). Following to replace the bridge(did not found yeat part) and power transitor 2n3055(2A max)
If you are intrested I can attach full schematic/ layout and software when I get home for second version.
 
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