Help needed building power supply

Feb 27, 2006 8 Replies
J

Hello,



I need some help in building a 12V dc power supply. I can find lots of documentation on building one from scratch and selecting a transformer for the initial AC supply voltage, but this is my problem. I wish to impliment this 12 Vdc into an audio amplifier and draw from its current transformer. I do not want to introduce another transformer. So, I am confused as there is not much documentation/theory for me to learn from. The exact requirements are 12Vdc @ 600 ma...no idea as for a max ripple voltage...LCD back light supply



I measured a +-38V dc after the rectifier diodes. I have a 12V regulator but I need to know how to get the 38V dc to a usable level for the regulator and have it filtered. Normal theory tells me to use a capacitive filter rated at twice the voltage of the supply. But, the regulator has a max input rating of 34Volts....so now I am lost.



Please, someone help or point me to some www.com where I can learn...again...every place I find assumes building a power supply based on a ideal transformer rating for the intended output voltage



Jerry


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G

The problem you have is dissapating at least 10 watts of heat. Going to need a big heat sink, and maybe some zener diodes to soak up a little voltage. There may be a switching device or just a plain DC to DC conveter you cn easily use. I added a supply in an amplifier by doing what you didn't want to do.

Maybe Gigablast or Google??

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J

Yes? You called ?:-)

...Jim Thompson

| James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC\'s and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | | http://www.analog-innovations.com | 1962 | It\'s what you learn, after you know it all, that counts.
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W

Take a look at the national semiconductor site. An LM2675-12 might do the trick.

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Look at the power supply on my site for the Cricket. I use a similar 5V regulator.

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Bill

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T

No, he does carpentry -- not circuit design.

Tim Wescott Wescott Design Services http://www.wescottdesign.com Posting from Google? See http://cfaj.freeshell.org/google/
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J

Actually, the turkeys who translated from the Greek texts to make the KJV did a lousy job.

*Tekton*, properly translated is **hand-worker**. generally thought to equate to the modern *itinerate day-laborer*.
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NOTE: Neither of these fools can make a proper HTML page:
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It makes perfect sense. If Joseph and his sons were cooped up in a carpenter shop in Nazareth, Jesus would not have been quite so able to spread his dogma widely.

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J

Thanks for the replies,

I was just doing some reseach and educating myself on switchers such as LM2576HV-12. I will try the circuit (fixed output voltage version) on page

11/12 on the below link be adequate for the 12V version?

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Sorry for the dual posts/topics...my newsgroup server is not getting messages to quicly so I thought no one was responding...

Jerry

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