# regulator on power supply

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#### podgymax

##### New Member

The output of this circuit is 53V. How to regulate this circuit to have a fixed voltage and current 2A? Do I need to add some chips? Any help or recommendations would be greatly appreciated!!!

Sorry for the wrong picture...
(the ele. cap on this circuit is 2200uF/100V, not 50V)
(IN5401 diode and 220-48 transformer)

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#### ericgibbs

##### Well-Known Member
The output of this circuit is 53V. How to regulate this circuit to have a fixed voltage and current 2A? Do I need to add some chips? Any help or recommendations would be greatly appreciated!!!

(the ele. cap on this circuit is 2200uF/100V, not 50V)
hi,
What fixed voltage do you want at a current of 2Amps.??

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#### audioguru

##### Well-Known Member
What is a 1N4008?
The 1N4001 to 1N4007 have a max allowed continuous current of only 1A.
They will smoke with 2A.

#### mrimi

##### New Member
sorry for that,i have same problem can u help me how u calculate the capacitor c1

#### podgymax

##### New Member
Sorry for the wrong picture...I am using IN5401 diode and 220-48 transformer

And the C1 is just for low-pass filter, so can have a DC output.

and I want to have a fixed 48V 2A

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#### Hero999

##### Banned
That doesn't look right to me.

If you have a 48V transformer the rectifier voltage should be about 66.5V, more unloaded.

You can't have 48V fixed at 2A, Ohm's law says that current is proportional to the load resistance. What I think you mean is you need a fixed voltage of 48V with a current capability of 2A.

You'll need a 40V transformer with a LM317 and a by pass transistor. The capacitor will need to be 6800µF and rated to at least 70V (100V is a typical rating), 2200µF is far too small. This should be fine as long as you don't need short circuit protection.

#### podgymax

##### New Member
I can't find 40V transformer in the shop. And if I used lm317, can I set the output become 48Vdc?

Sorry for my awful expression; actually, what I want is to regulate this circuit.

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#### podgymax

##### New Member
and wt I want is current max is 2A (not fixed)

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#### bokbaard

##### New Member
I don't think we are getting through to you
Current cannot be fixed at 2A, unless you have a 24 ohm load connected to it permamently

You regulate(fix) the voltage at 48V (or whatever you want, using whatever regulator and the suggested calculated resistor values).
Then, IF your diodes are 2A capable, and your transformer can deliver 2A, you can have a regulated 48V and a maximum usable current of 2A, so "max 2A" yes, "fixed 2A" no

#### podgymax

##### New Member
Yes...is max 2A...then how should I regulate this circuit to fixed 48V

#### bokbaard

##### New Member
Well the datasheet will teach you about the values for resistors around it.
Note, without pass transistor, the 317 will fry, its rated at 1.5 A (according to the datasheet)
The LM150 is a 3A regulator, should work better.
To get 48V, make sure the LM\'s can output that much (as your inpout will be slightly higher).

#### audioguru

##### Well-Known Member
The adjustable regulators do not have a 0V connection so normally they do not have much voltage across them.
But with this fairly high voltage supply, the regulator will blow up if the output is shorted to 0V because then the input to output voltage on the regulateor will far exceed its voltage rating.

#### Hero999

##### Banned
I can't find 40V transformer in the shop.
What about a transformer with two 20V secondariness?

audioguru said:
The adjustable regulators do not have a 0V connection so normally they do not have much voltage across them.
True but this can be fixed with zeners and transistors. If it only needs to survive a short term short, a 39V zener across the LM317 will do, if it needs to survive a long term short extra transisors need to be added.

#### podgymax

##### New Member
If I design to use TL494 to regulate the circuit, how should I change to use this chip? And do I need to change the transistor to mosfet as the current can be 2A?

#### Hero999

##### Banned
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