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-   -   Is there any thing wrong with this design (http://www.diyaudio.com/forums/power-supplies/230726-there-any-thing-wrong-design.html)

tony Ma 23rd February 2013 09:43 PM

Is there any thing wrong with this design
 
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Dear All,

I have a question with this design for PS

The input is 320 V AC and the out put is 400V DC

I am wondering why Resistor #5 (68K 3W) always very hot?

Can some one give me some clue?

tks

AJT 23rd February 2013 09:58 PM

what is the dissipation of that Resistor #5 (68K 3W)? in my case, i use that 3 watt to dissipate less than 1 watt...

vacuphile 23rd February 2013 10:18 PM

Does it actually work at all? I really don't see how you could subject an LM317 to these voltages. How could you send AC straight through a 10mH inductor? What happens if you put 100uF straight over AC? Where does the DC come from? Etc.

sofaspud 23rd February 2013 10:27 PM

That was my initial thought, too, vac. But he has a rectifier box there on the AC input. I don't understand the zener bypass, or the pot wiper to nowhere, or...
so best for me to leave it alone.:)

vacuphile 23rd February 2013 10:29 PM

Sofaspud,thanks, had overlooked it. And you are also right about your last point.

AJT 23rd February 2013 10:35 PM

the zener could be a 27volt one, together with the mje13005 ensures that the vin-vout rating of the lm317 is never exceeded....

sofaspud 23rd February 2013 10:40 PM

Sure. I should've realized. Thanks, Tony.

AJT 23rd February 2013 10:43 PM

welcome, the circuit reminds me of the maida regulator....http://www.diyaudio.com/forums/tubes...regulator.html

vacuphile 23rd February 2013 10:49 PM

Quote:

Originally Posted by Tony (Post 3383414)
the zener could be a 27volt one, together with the mje13005 ensures that the vin-vout rating of the lm317 is never exceeded....

You are completely right!

mirlo 23rd February 2013 11:41 PM

LM 317 adjust pin is 1.25 V below output V. R5 dissipates about 2.35 W = (400-1.25)^2/68000.

The 5k pot is much too large. For 400 V out you need about 213 Ohms there, so you will be using only 4% of the pot, voltage adjustment will be way too sensitive.


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