DC-DC Conversion

I did it with a couple amps I built. I just used zeners with some pretty big power resistors. Thats how they usually did it anyway.

greg

"news.gatech.edu" wrote in news:el4dli$t8b$ snipped-for-privacy@news-int.gatech.edu:

A voltage regulator IC (lm317/337, 7815/7915, etc) would probably be a good to start.

----== Posted via Newsfeeds.Com - Unlimited-Unrestricted-Secure Usenet News==----

----= East and West-Coast Server Farms - Total Privacy via Encryption =----

The LM317HV might survive in that job

but the LM337HV would be vulnerable.

You can protect a linear regulator against out-of-range supply voltages in a variety of ways, but it can be a bit tricky.

For low-powered op amp circuits, a power resistor and high-disipation zener can be a lot easier and much more reliable (unless you really know what you are doing).

But it will most likely not result in top notch HiFi performance. Worst case you get motor-boating because some PSRR ain't enough. The real way to do it is to drop it to, say 25V with a transistor/zener. Then plop nice regulator chips in there to create clean supplies.

Well, if you are going to get fussy, use up about half the 56V to 25V gap with a dropping resistor, and stabilise the voltage at the collector of your transistor with a decent-sized capacitor to ground - do it right, and you will roll of the high frequency rejection from the frequency where the linear regulator starts losing high frequency ripple rejection.

Worth it if you need about 120dB of PSSR up to a MHz or so.

Surprising there isnt already a lower voltage needed for the input stage etc,

With a disipative dropper (ie linear regulator/resistor+zener) the amount of power wasted would be very significant with more than a few leds, assuming the voltages are generated form a transformer you could feed the AC from the transformer through a capacitor, probably a bipolar electrolytic, then regulate with a zener. make sure the capacitor is adequatly rated for the amount of ripple current continously.

so for example if you ac voltage is 40volts and you need 100ma, 22uf might do.

Alternativly if you arange to connect the leds in series it would draw less current anyway.

Colin =^.^=

When I built power amps in my wild days I always sprung for a little extra transformer that supplied the preamp stages and other miscellania. And I made sure the big one came on afterwards.