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psu problem
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p.larner:
HI,i have a transfo with a tap giving 37v raw ac,once rectified and smoothed i guess it will be about 40+v,is there any regulator ic that can take that voltage?,i need something like a lm723 but good for say a 50v input not the 723's 37v max,any ideas what i can use?,i want to build a 40+v bench psu with it.
TimFox:
To start:  37 V rms from a transformer will give more than 50 V after a bridge rectifier and unloaded filter capacitor.
Also, if the 37 V is specified at a given load current, the voltage will be even higher with no load.
You could use a 723 in a floating circuit, with a higher-voltage pass transistor.
E.g.,  https://www.circuitstoday.com/floating-regulator
p.larner:
on the schematic on the linked page,can a 27v zenner be used as i have some 27v half watt ones,if so will max output be 27v?.
rdl:
There's a high voltage version of the LM317 available that will handle up to 60 volts input-output differential.
mariush:
peak dc voltage will be sqrt(2) x AC Voltage  - 2 times voltage drop on diode inside bridge rectifier

In your case, around V dc peak = 1.414 x 37 - ~1.6 = ~50v  - you'll want to use 63v or even 75v rated electrolytic capacitors


LM317HV can do 60v : https://www.digikey.com/en/products/detail/texas-instruments/LM317HVT-NOPB/212662


Note that you won't be able to do much of a bench power supply with just a linear regulator, because linear regulators work by dissipating the difference between input voltage and output voltage as heat and a to-220 regulator on a very good heatsink can dissipate maybe 10-20 watts.

So for example if you want 5v output and 100mA, you're already producing  (50v - 5v ) x 0.1A = 4.5 watts as heat.

You may want to get a switching regulator to produce around 5v higher than desired, then use a linear regulator to output the exact voltage.

If you want to keep it fully linear, usually it's done by using transformers with multiple secondary windings and using relays to connect windings together for higher voltage.
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