0-30V Stabilized Power Supply

[dracu_n_dulap]

;D yes allready found it and the ic too i will place an order as soon as posible. thank you.

 

[limbo243]

Hello!

Yesterday I got an oscilloscope to see if there is an output voltage ripple.
And I have to say: I was not able to see a ripple. Not even by 0,05V/div.
I measured  it by 30V 0A; 30V 3A; 1V 3A;... with current limiting and without
My power supply works very fine!  ;D

Thx for all your help!
bye Markus

 

[PicMaster]

I can't remeber now and I know the Schematic say 28V AC but for the TLE2141 or MC34071 does the transformer have to be 28V AC or can it be a 30V AC ?

Looking at the data sheets the OPA445 is 45V and the other 44V. Only I thought I ordered 10 OPA455 but wrote the wrong part number down which was good really becasue when I did find the right part number I was shcoked to see they where

 

[limbo243]

Hello PicMaster!

Have a look at my post from August 27, 2009, 05:18:37.
I posted my schematic with my bill of materials. I built this power supply and it works perfectly!
I used a 2x30V/230VA transformer in order to build a dual version.
Link to transformer: http://shop.conrad.at/ce/de/product/518458/RINGKERNT2X30V230VA

My tip for using a 30V transformer: Build up the circuit with D15 (in my schematic). And then measure the positive supply voltage. If there are 44V you don't need D15. If the voltage is higher - use a Zener-diode which fits to your circuit. For example:

Positive Supply: 45V
Max OAMP Supply: 44V
45V-44V= 1V Zener-Diode.

In my circuit, I did not need D15, although I used a 30V transformer!
I don't know if the OPA445 will work. The MC34072 I used was 0,97

 

[audioguru2]

The OPA445 opamp is rated for a positive and negative 45V supply which is a total of 90V. It needs a different circuit to the latest one, U2 and U3 use a -5.6V supply and is similar to the original circuit. Its total supply was 48V.

A 30VAC/4.3A transformer will be about 31VAC without a load. Its peak voltage is 43.8V and the rectifier bridge will drop it to 42.4V without a load which is fine for MC34071 or TLE2141 opamps that have a rating of 44V. A 28VAC transformer will be safer.

 

[PicMaster]

Thanks guys I shall give it ago and see how i get on  ;D

 

[msr2009]

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!

 

[audioguru2]

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.

 

[Hero999]

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

No, the voltage on the capacitor will be about 32.5V with a 24V transformer.

 

[audioguru2]

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.

 

[msr2009]

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

 

[audioguru2]

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.

 

[msr2009]

But I can't just use 24VAC and get a maximum output of 25VDC ? I'll need to make modifications to the circuit ?

thanks !

 

[audioguru2]

Your power supply will have a maximum regulated output of about 25VDC because the voltage from your transformer is too low for 30VDC.

You should modify the voltage setting pot so that it cannot be adjusted higher than about 25VDC where the output will be full of ripple.

 

[Hero999]

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.

 

[ulli12]

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

 

[audioguru2]

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.

 

[mendimano1]

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

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[audioguru2]

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.

 

[mendimano1]

Hello Audioguru, thanx for tips, and please if you could sent me a latest schematic with parts list. regards