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Linear regulator with wide Vin range...?

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treez

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Hello,

I am designing a linear regulator, which must provide 12mA , 9V from an input voltage of 12 to 100VDC.

The problem is that big resistance values are needed at 100Vin, but then these large resistances prevent enough base current from getting to the regulator’s transistors when at 12VDC.

Do you know of any better ways then the following?…..

https://i46.tinypic.com/n6p3th.jpg



TIP47 Datasheet:
https://www.fairchildsemi.com/ds/TI/TIP50.pdf

2N5550 Datasheet
https://www.fairchildsemi.com/ds/2N/2N5550.pdf
 

Replace R by a current source.

Something like this:

**broken link removed**

Note: Values of zeners and transistors used in the circuit are "random" :)
 
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Thanks, but Q2 would be dissipating about 400mW when vin = 100VDC.

Also, the 1N750 (4V7 zener) will drop too much voltage for when vin = 10VDC.

I realise your components etc are random but i dont see how i can change them to make the winning circuit that i seek.....maybe i should make the zener a forward biased series chain of two diodes........ummmmm, i dont know.
 

I said that the values were random --> is not a plug & play scheme.

With so much variation in voltage drop a resistance is unfeasible -> Use a current source.
Values and final scheme? --> What you need.

- If you need to drop down in the PNP Q -> 2 diodes instead of zener.

- Minimum dissipation Q pnp? -> Set to minimum collector current.

- Q npn? -> TO66 + heatsink if required.
 

This is a simple voltage regulator.



It's not exactly the same as current regulation, in case that makes a difference.

Watt ratings are ordinary except the 680 ohm resistor which needs to dissipate 12W when the supply is 100V.
 
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