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0-30V Stabilized Power Supply


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hi any updates to this project

Why do you show an LT1038? it is obsolete and is not made anymore. It is impossible for it to dissipate 32V x 10A= 320W. Its datasheet shows that with a huge heatsink with fan or with liquid nitr

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Hello Guys !

I have a 24Vac x 25A transformer...

What I need to make to have more than 0-3A at output ? Let's say 0-5A

How much DC regulated can I expect with 24Vac at input ?

I'll make two boards and have a dual output power supply... there is a lot of "Amps" from my xformer :)

Thank you!

The voltage from your 24VAC transformer will allow the project to have a regulated max 25VDC output if the main filter capacitor has a high value. Add more output transistors and driver transistors for more Amps. The value of R7 determines the max adjustable Amps.

If your transformer has two 24V windings the one can be used for a positive supply and the other can be used for a negative supply or for a second supply.

Which circuit will you make? The original circuit in the project has errors.
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No, the voltage on the capacitor will be about 32.5V with a 24V transformer.

The rectifier bridge will have a voltage loss of about 2V.
The current-sensing resistor R7 uses 1.4V at 3A.
The output transistor has a max voltage loss of about 2V.
The driver transistor has a max voltage loss of about 1V.
The opamp U2 has a max voltage loss of about 2V.
The main filter capacitor will have ripple of about 2V p-p.
Then the regulated output is less than 25VDC.
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The voltage from your 24VAC transformer will allow the project to have a regulated max 25VDC output if the main filter capacitor has a high value. Add more output transistors and driver transistors for more Amps. The value of R7 determines the max adjustable Amps.

If your transformer has two 24V windings the one can be used for a positive supply and the other can be used for a negative supply or for a second supply.

Which circuit will you make? The original circuit in the project has errors.


AudioGuru,

I'm going to make the circuit of this thread (posted by Redwire and your partlist with red comments) is this ok ?

My transformer is 12+12VAC

How much current can I drive of each output transistor ?

thanks
Marcelo
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The circuit in this thread makes 0V to 30VDC at 3A. It uses a 28VAC transformer.
Yours will be different since your transformer's voltage is too low.
It will provide a max output current of 5A if you use 3 output transistors (each with a 0.33 ohm emitter resistor) and change R7 to 0.27 ohms/10W resistor and change one of the current-setting resistors.

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The rectifier bridge will have a voltage loss of about 2V.
The current-sensing resistor R7 uses 1.4V at 3A.
The output transistor has a max voltage loss of about 2V.
The driver transistor has a max voltage loss of about 1V.
The opamp U2 has a max voltage loss of about 2V.
The main filter capacitor will have ripple of about 2V p-p.
Then the regulated output is less than 25VDC.
Oh you're talking about the output voltage, I thoguht you were refering to the voltage on the filter capacitor.
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I noticed the new power supply schematic has 2 2N3055 power transistors in parallel.
The original schematic only has only one.
Is the "new" power supply also limited to 3A or is it 6A? (assuming the transformer & heatsink are ok)
If more than 3A is possible, does one only has to change the setting of the current trimpot?

thank you

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The single 2N3055 transistor in the original project got too hot (dissipating 89W) when the output voltage was low or was shorted and the current was set to 3A.

The modified and corrected circuit has a higher transformer voltage which causes even more heat so two 2N3055 transistors are used to share the heat (50W each).
Two output transistors use less total base current than one so the driver transistor is cooler.

Three output transistors can have a 5A output current. R7 is the current sensor and is changed from 0.47 ohms to 0.27 ohms for 5A output.

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  • 2 weeks later...

Hello, i have build the original version of power supply and it forked fine (with it unperfections as well), now im thinking to build the upgradet version with this schematics and parts list. anyone who haves god advices please send me. And if anyone haves the PCB for this version im asking him to post it or to send me. Regards

post-42880-14279143982446_thumb.gif

post-42880-14279143982672_thumb.png

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Hello, i have build the original version of power supply and it forked fine (with it unperfections as well), now im thinking to build the upgradet version with this schematics and parts list. anyone who haves god advices please send me. And if anyone haves the PCB for this version im asking him to post it or to send me. Regards

You have the schematic for one version (but not the latest) and the parts list for a much older version.
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Yes, it goes with the sketch you posted.    For the 5A version I would recommend the following:

1.    30VAC  7.2A  or higher  stepdown transformer
2.    R7 = 0.27, 10W resistor
3.    C1= 20,000 uf, 63V
4.    Q4, Q5 & Q6  (at least 3 paralleled ) NPN transistors on huge heatsinks.

Actually pretty minor changes since most of these parts are located off the PCB because of their size .  The basic PCB doesn't change much except to ensure the tracks are wide enough to handle the 5A.

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