HELP - DC45V to DC30V voltage regulator - diyAudio
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Old 27th June 2013, 02:41 PM   #1
diyAudio Member
Join Date: Jun 2013
Unhappy HELP - DC45V to DC30V voltage regulator


I m new in the forum! Im spanish.

I have a question about voltage regulators.
I need help with chips or boards.

I have a rectifier board with voltaje out @DC45V.
Can I convert the DC45V to DC30V though a circuit?
Ive been looking at the LM317, but the max. voltage input is 40V.

On the other hand, alternatively,
I have a toroidal transformer @AC230V to AC30V.
Can I convert the AC30V to AC21V though a circuit?

Ive been looking at Ebay, and Ive found this item, but I dont know if it will work:
DC to DC AC to AC Converter Board Step Down Voltage Regulator Module 12-48V New | eBay

Please, help me.

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Old 27th June 2013, 03:34 PM   #2
diyAudio Member
Join Date: Jan 2002
Location: Tyrone Ga. U.S.A.
Depending on how much current you need the TL783c might work out for you. It is much like the LM317T but with a voltage rating of 125v and a .7A max output current.
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Old 27th June 2013, 03:44 PM   #3
Minion is offline Minion  Canada
diyAudio Member
Join Date: May 2006
Location: Cowican Bay , vancouver island
the LM317 will work to regulate 45v down to 30v ..... the 40v for the lm317 is the Voltage Differential not the max input voltage .....
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Old 28th June 2013, 02:42 PM   #4
diyAudio Member
Join Date: Jun 2013

Thank you very much Woody and Minion.

I've been checking the items LM317 and LM317T.
LM317 provides a maximum current of 1.5A

My rectifier has a dual output DC45V-0V-45V (100W).
I need an output DC30V-0V-30V and ~3.15A
(LM parts >4A for safety).

Ive though to use this units:
LM338 (5A) (1 for each 30V)
- Reference Voltage 3V < (Vin - Vout) < 35V
- Current Limit at 15V@25C provides 5A

Click the image to open in full size.

What do you think?

Alternatively, I would like to make this circuit:

10 Amp Regulated Power Supply Circuit
Click the image to open in full size.

But LM107 is obsolete, and I don't find an equivalent part.

LM107 ~~ LM318 for this circuit?

thank you very much.
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