I need 15volts dual power supply for my TL072 subwoofer preamplifier. I'm getting around +38 ,0,-38v volts DC from my power amplifier. I have one option to use 7815 regulator but i think it's maximum voltage is only 35 volts.So is there any other regulator like 7815 that can withstand input voltage upto 40 volts DC?
Please help.
Thanks,
Sunny
Please help.
Thanks,
Sunny
So "fix" the LM317 and LM337 at +15 & -15.
Or lower the 38V using the LM317/LM337, then use your precious 7815/7915.
Or lower the 38V using the LM317/LM337, then use your precious 7815/7915.
Can you please give me the circuit diagram how to fix the LM317 and LM337 at +15 & -15?
Thanks,
Sunny
I don't have a diagram handy to upload, but you can find one easy enough in the datasheets or online. The resistors to set 15V are 220 ohms from the output to adjust pin and 2400 ohms from the adjust pin to ground.
I have the same question. 38v to 15v is a big step down. That's the reason I wodnt't try the 317/337 regs. I think they could overheat and blow easy, even with heatsink.
The 317/337 generally are happier with Vin about 35V (Max). The datasheet clearly shows this.
The simplest way of exploiting higher voltages is to pre-regulate.
Any linear regulator will be dissipating quite high power under these conditions so your heatsinks will need to be big enough to get rid of the heat.
The simplest way of exploiting higher voltages is to pre-regulate.
Any linear regulator will be dissipating quite high power under these conditions so your heatsinks will need to be big enough to get rid of the heat.
It would make much more sense and be far simpler to build a low power supply especially for the pre-amp.
I'm not sure what you are seeing. I'll (maybe) look after I type. The 317 doesn't care what it's input is. It's the in-out differential that matters. And it certainly won't overheat and blow up!
With a 25V drop and 100mA current (which is getting near worst case for the OP), it's only 2.5 watts dissipated by the regulator.
The danger is when under initial start up conditions. You must keep Vin-Vout less than 35V. Anything above this is a recipe for failure.
There must be more to the story. Where are you getting this 35V figure from? What start up conditions do you infer from the OP's app that make this relevant?
Oh geez. I have the NatSemi July2004 datasheet in front of me. Please kindly answer the previous two questions.
Even worse worst case: 30v drop and 250mA is still only 7.5W. With appropriate heatsink that 317 will run "happily" til the cows come home.
Even worse worst case: 30v drop and 250mA is still only 7.5W. With appropriate heatsink that 317 will run "happily" til the cows come home.
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LM317? It says nothing in the NatSemi datasheet other than input-output voltage 40V. I searched every reference to voltage.
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I agree, this is incorrect. The total difference between input and output voltage cannot exceed 40V, not the input voltage.
"Since the regulator is “floating” and sees only the input-to-output differential voltage,
supplies of several hundred volts can be regulated as long as
the maximum input to output differential is not exceeded, i.e.,
avoid short-circuiting the output."
"Input-Output Voltage Differential: +40V"
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