[SOLVED] Linear voltage regulators

Hello guys. Is there any regulator that can accept 50V max input and can output ±15V? Can't find on the net.
Any help is very much appreciated.

By nature, a linear voltage regulator can't invert the input voltage. For the negative part, you are asking about an inverting boost converter or similar.

FvM said:

By nature, a linear voltage regulator can't invert the input voltage. For the negative part, you are asking about an inverting boost converter or similar.

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I'm sorry, there's an error on my question. I'll rephrase it.
Is there any regulator that can accept +50V max input and can output +15V and -15V for -50V?

For the positive side, Texas Instruments TL783 (700mA can handle Input versus Output difference of up to 125V). For the negative side the lowest input voltage I can find is -40V.


You could always make your own voltage regulator circuit (which would allow you to spec the parts to make whatever voltage you want).

Here is a simple way to make regulated bipolar supplies:



As the scope traces show, the incoming supplies vary between 30 and 50 V amplitude. The loads receive regulated +15 and -15 V.

The loads can draw different amounts of current.

The transistors need to be rated to handle the voltage and the power dissipated.

If the accuracy of the suggested discrete regulator isn't sufficient, a standard negative regulator (e.g. 7915) with transistor/Z-diode pre-regulator is the most simple solution.

BradtheRad said:

Here is a simple way to make regulated bipolar supplies:



As the scope traces show, the incoming supplies vary between 30 and 50 V amplitude. The loads receive regulated +15 and -15 V.

The loads can draw different amounts of current.

The transistors need to be rated to handle the voltage and the power dissipated.

Click to expand...

Thank you guys.

Sorry but I don't have that much experience on designing circuits. Could you please tell me the values and types of transistors and Z-diodes that I could use on this circuit?

Thanks again.

sinCERA said:

Could you please tell me the values and types of transistors and Z-diodes that I could use on this circuit?

Thanks again.

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Sorry, I should have labelled the zener diodes as 15.6 to 15.7 V. This falls between the standard values of 15 and 16V.
Only if you are lucky will the zener you buy have the exact right amount. Or else you will need to 'bend' the value a bit, if you want exactly 15V output.

The transistors must be able to carry the current you require.
They must withstand over 50V.
They will dissipate a certain amount of watts as heat, which can be calculated based on the current they will carry, and the voltage they will drop. If they get overly hot then you will need to build heatsinks.

My schematic shows a barebones method. It lacks the advantages of a commercial regulator IC. You may find the 7815 and 7915 are suitable to control operation through the transistors.

A discrete transistor solution for negative voltage with quite descent performance could be something like this:

By adjusting resistor R7 you can trim the output voltage, but I simulated the circuit, and it gave pretty exactly -15V as it is.
One advantage is, that all components are readily available types and values, and the circuit is very suitable for relatively high input voltages.
Note, that MOSFET M1 may dissipate a lot of heat, depending on your load. Therefore it should have a heat sink in most cases.
(By using P-MOSFET and a NPN transistor one can easily build similar circuit for positive voltages, too.)

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Thanks for contributing guys to solve my problem..
I really appreciate it much..