Moderately HV regulators

I need to regulate an unregulated voltage (transformer->rectifier->filter caps) down to 80V. I can use an adjustable regulator for this since the only thing that matters is the input - output voltage difference and not the absolute voltage, correct?

speakerguy79 said:

I need to regulate an unregulated voltage (transformer->rectifier->filter caps) down to 80V. I can use an adjustable regulator for this since the only thing that matters is the input - output voltage difference and not the absolute voltage, correct?

Click to expand...

hi,
Is this OK.?

https://uk.farnell.com/1192057/semi...n-semiconductor-mc33363bdwg&_requestid=278119

That chip only goes to 6.5V? Otherwise looks like a very nice part.

The problem is that during power up or an accidental output short, the regulator will see the full input voltage. Thus normal design practice is to have the regulator capable of withstanding the full voltage.

speakerguy79 said:

That chip only goes to 6.5V? Otherwise looks like a very nice part.

Click to expand...

hi,
Are you reading the datasheet correctly.?

What's the input voltage?

Did you know an LM317 doesn't have a limit on the input voltage; it's the voltage drop that matters?

The maximum input-ouput differiential is 40V. This means with the standard LM317, the input voltage could be as high as 120V and you won't have any problems. The only trouble is capacitance on the output might cause a higher differiential on start up, so it's a good idea to stick a 39V zener diode across the LM317 to protect it.

Hi Speakerguy79,

There's also a high-voltage version of the popular LM317.

https://www.electro-tech-online.com/custompdfs/2008/08/tl783.pdf

However, the output current is limited to 750 mA.

on1aag.