Hi guys i am a newbie here..was wondering if someone could please advise me how to get -15v dc 3amps...from an input of -55v dc thanks.

 

Probably a fast switching buck converter, but I can't get the Texas Instruments Simple Switcher website to work with negative voltages right now.
You need to specify the range of the voltage supply, like -52 to -56 volts to get a proper design, and the range of the load. Is it always 3.00 amps? Probably not. What about allowable output voltage? -14.8 to -15.2?

I've been sick lately, but this is a start. Tell us some more numbers and you'll probably get a good answer soon.

 

Where is the -55Vdc came from?

 

Where is the -55Vdc came from?

Pretty much what I said. How stable is the -55 volt supply? Loads down to -50 volts when you use up 3 amps? Has noise on it from the generator? Lots to consider if you want something reliable.

 

Pretty much what I said. How stable is the -55 volt supply? Loads down to -50 volts when you use up 3 amps? Has noise on it from the generator? Lots to consider if you want something reliable.

The voltages at the torroid is 35v ac..after rectifying it jumps to 54v to be specific...tried the lm2576...getting +15 v ..which is good...need -15 v dont know how to work that..using a lm2576..i tried and busted one ic.

 

(Theoretically, 35 VRMS rectifies to less than 50 volts.) Did you make a rectifier for the negative voltage or do you need an inverting design to get -15VDC from +54VDC?

There is a way to do an inverting buck regulator with an LM2576, but it isn't the right voltage range. Need to keep searching.

 

(Theoretically, 35 VRMS rectifies to less than 50 volts.) Did you make a rectifier for the negative voltage or do you need an inverting design to get -15VDC from +54VDC?

There is a way to do an inverting buck regulator with an LM2576, but it isn't the right voltage range. Need to keep searching.

yes have made a rectifier ,its got +55v dc and -55vdc have used the positive rail to get +15v which works great using the lm2576hv ,but -15v is driving me nuts ....lol...well to give you an overall idea of the power supply ...it all started of with a audio 18 channel mixer ,which had a faulty smps, cant get hold of a similar smps ,so decided to make my own basic power supply ,being a 18 ch mixer i am guessing would need approx 3 amps..well thats the story .

 

34 minutes of searching and no joy. Chips labeled 3 amps won't do 3 amps when inverting from +15V to -15V. 60 volt chips are not numerous.
At this rate of progress, you might end up adding a 15VAC transformer to get a lower working voltage so you can find a regulator that will work for you.

ps, I don't think you need 3 amps for an audio mixer. Those things have outputs in the milliwatt range.

If you could get a -15V switcher, what would you feed it? 120 VAC?

 

Here's a switcher for $20, probably "plus shipping" or you might even use a wall wart style.

http://www.powersupplydepot.com/15-Volt-Power-Supply,-4A,-60W,-Switching,-Hengfu/16007-PS/

http://www.powersupplydepot.com/Power_Supplies/Adapter_Power_Supplies/

 

Here's a switcher for $20, probably "plus shipping" or you might even use a wall wart style.

http://www.powersupplydepot.com/15-Volt-Power-Supply,-4A,-60W,-Switching,-Hengfu/16007-PS/

http://www.powersupplydepot.com/Power_Supplies/Adapter_Power_Supplies/

thanks a lot mate will go through those sites ,thanks for your effort in searching for a solution ...appreciate it ,will let you know how i go,cheers...Ta

 

34 minutes of searching and no joy. Chips labeled 3 amps won't do 3 amps when inverting from +15V to -15V. 60 volt chips are not numerous.
At this rate of progress, you might end up adding a 15VAC transformer to get a lower working voltage so you can find a regulator that will work for you.

ps, I don't think you need 3 amps for an audio mixer. Those things have outputs in the milliwatt range.

If you could get a -15V switcher, what would you feed it? 120 VAC?

would feed it 220v ac..

 

That first switcher will work for your voltage and frequency.

http://www.powersupplydepot.com/15-Volt-Power-Supply,-4A,-60W,-Switching,-Hengfu/16007-PS/