0-30 Vdc Stabilized Power Supply

[audioguru2]

Hi Mongseng,
You want me to re-design the power supply for you?
I don't even have a half-decent power supply for myself. I just use a simple LM317 adjustable power supply like in our Projects section.

The LM317 can easily provide 1A, but it has a max current limiter instead of an adjustable  regulated current. Its minimum output voltage is 1.25V which is low enough for most applications.
Its datasheet shows how a single pot added to it converts it into an adjustable current regulator then a second one can be added in series as an adjustable voltage regulator.
With two LM317 IC's in series, they need a minimum input voltage of about 19V to work properly for a 12V output. ;D
 

 

[mongseng]

Hi audioguru,
Thanks for your reply.
I have a 16v, 5A transformer in hand. Can this transformer run for this project?
I really like this psu.
Thanks

 

[audioguru2]

I have a 16v, 5A transformer in hand. Can this transformer run for this project?

Hi Monseng,
If a few resistor values are changed in the circuit then the 16V/5A transformer can be used and the modified project will deliver 15V at 3.5A. ;D

 

[mongseng]

Thanks audioguru,
That is what i want. Can you please guide me which resistor and what value to change.

 

[audioguru2]

It will take me a few hours or days to redesign this project for your low-voltage transformer.
Just about every resistor wil need to be analysed. :'( :'( :'(

 

[mongseng]

Hi audioguru,
Didn't know so many works to be done with low volt transformer.
maybe I'll stay on 24v or 30v transformer.
Anyway, thanks for your reply.

 

[audioguru2]

Thanks, Mongseng. ;D
It is best to keep with the modified project.
Are you going to make it for 3A or 5A? ???

 

[Alun]

It will take me a few hours or days to redesign this project for your low-voltage transformer.
Just about every resistor wil need to be analysed. :'( :'( :'(

Just use a voltage doulbler on the output of the transformer, but you'll need to double the current rating of the transformer or half the output current.

 

[audioguru2]

Hi Alun,
A voltage full-wave voltage doubler for a 3A output would need 3 (or 4?) huge capacitors and powerful rectifiers. Another low-current doubler might be needed for the negative supply but instead a few resistors can have their values reduced.

 

[Alun]

I thought it'd take you hours to redesign it.  ;D Perhaps halving the output current (as I also suggested) miight be more sensible if you want to use a voltage doubler, but you'd still need pretty big capacitors anyhow.

 

[ruden]

there components with working voltage limits(like capacitors with WV of 50 volts,resistors of 1/4 W) that should br considered in applying other than the prescribed ivput AC voltage

 

[audioguru2]

Hi Ruden,
If you give the circuit an input voltage too low, the resistors won't supply enough current unless their value is reduced. Also the parts for the negative DC voltage will need adjustment.
If the input voltage is too high then the currents will be too high and cause resistors and transistors to overheat. Of course the max voltage limits of capacitors, ICs and transistors must be considered as well. ;D 

 

[Spagbol]

Hi all,

I like the design for this PSU and would like to build it, but with some changes.

It seems only U2 needs a high supply voltage to drive the output to 30v, U1 & U3 would be happy with a lower supply voltage. I'm wondering about changing the transistor o/p stage to have a voltage gain of 3 and then clamping the opamps supply voltage at say 20v using a zener so that any stock opamps can be used? (I have loads of TL082s and LM358s etc. so I'd like to use those).

I have 2 transformers I can use, a 24v ~100va and a 2x14v ~300va, as this limits the max o/p voltage I thought I'd add a preset pot to the top of P1 to limit the max output voltage according to what the transformer can cope with?

As I'm using dual op amps I thought the leftover amp could become a comparator with a thermistor for a thermal shutdown if the pass transistor becomes too hot?

I'm a bit rusty, so any comments on changing the transistor o/p stage (if feasible) would be welcome!

 

[audioguru2]

Hi Spagbol,
Welcome to our forum. ;D
You have an excellent idea to use gain in the supply circuit's output stage to reduce the high supply voltage requirement for the driver opamp. I have seen high power audio amps with very high supply voltages, gain in the output stages and opamp drivers. I have some circuits in the many on my hard drive and I will post one when I find them.

However, adding gain to a high power transistor stage reduces its bandwidth which might interact with the bandwidth of the opamp and make a nice oscillator!
Carefullly planned frequency compensation must be used.

You also have an excellent idea to use a preset control to fine-tune the voltage pot's max output voltage at its max setting.

You don't need a true thermistor to measure temperature. Since you have a spare opamp then an ordinary diode or a junction in a transistor can be used instead. A silicon junction's voltage drop decreases about 3mV for each degree C of increased temp. The opamp could amplify it perfectly. ;D
I would use the temp sensing circuit to control the speed of a fan.

 

[cyw1984]

Hello,
I am sorry for my poor English...also I am a newbie of electronic...
I really want to make this project for my first and serious project..


I want to ask somting abt this project...hope anybody can answer me...thanks you.

1. Which precise part is control current and control voltage..??How to separate them??

2. I would like to separate to make it. How can i separate the circuit and test for it??

3. If I use 0-10 V DAC's Vref to repace P1 and P2 ...how can i change the circuit..?
please draw the circuit for me...please..

4. And how to caculate the change part if I use another Vref of DAC??

5. Does any body have a right schematic??? coz i read the post know that the original schmeatic have some bug

Thanks for answering

 

[audioguru2]

1. Which precise part is control current and control voltage? How to separate them?

P1 controls the voltage and P2 controls the current. They are completely separate but the project's output voltage is reduced by the current regulator.

2. I would like to separate to make it. How can i separate the circuit and test for it?

Make it with the pots and measure the voltages at the pots. Then program your DACs to produce the same voltages.

3. If I use 0-10 V DAC's Vref to repace P1 and P2 ...how can i change the circuit..?
please draw the circuit for me...please..

You don't want to use your DAC's Vref, you want to use its outputs to replace the voltages from the pots. Simply remove the pots and apply the voltage from the output of each DAC to where the pot's slider was connected.
You will need to re-arrange the parts for external current control. P2 should be changed to a fixed resistor then the output from your DAC could be connected to the grounded end of R21.

4. And how to caculate the change part if I use another Vref of DAC?

Calculations won't be accurate due to the tolerance of resistors in the circuit. Just build it with pots and measure their voltages.

5. Does any body have a right schematic??? coz i read the post know that the original schmeatic have some bug.

The updated schematic is here in this forum, I am sorry I lost my copy on my old computer's broken hard drive. Here is the modified one's parts list:0-30V_Mod_parts_list.txt

 

[cyw1984]

Thanks audioguru, then
which part is Voltage reference and linear Voltage regulator???
I would like to test one by one~~Thanks

Is it all the part is voltage regulator??

Am I worng???

 

[audioguru2]

Hi Cyw,
That part of the circuit is more than only the voltage regulator.
U2 drives the darlington emitter followers connection of Q2 and Q4 and the ratio of R12/R11 plus 1 is the voltage gain. They have an extremely low output impedance and good voltage regulation because the open-loop gain of U2 is at least 200,000 and is reduced to just a few with the negative feedback through R12.
R7 is the current sensing resistor.
Q1 shuts down the output immediately when the project is turned off.

The voltage reference is fixed at 11.2V and feeds the voltage adjust pot. ;D

 

[cyw1984]

Hi Cyw,
That part of the circuit is more than only the voltage regulator.
U2 drives the darlington emitter followers connection of Q2 and Q4 and the ratio of R12/R11 plus 1 is the voltage gain. They have an extremely low output impedance and good voltage regulation because the open-loop gain of U2 is at least 200,000 and is reduced to just a few with the negative feedback through R12.
R7 is the current sensing resistor.
Q1 shuts down the output immediately when the project is turned off.

The voltage reference is fixed at 11.2V and feeds the voltage adjust pot. ;D

O...IC~~~

Can help me to remove the thing which not a voltage regulator....Thanks a lot

 

[audioguru2]

[Can help me to remove the thing which not a voltage regulator.

Why? All the parts are needed in the voltage regulator circuit.
If you use a DAC to provide a reference voltage, then you don't need the project's zener diode/opamp reference voltage circuit.