How to limit the voltage to 13.9V?

[yassin.kraouch]

Hi the input voltage is between 6V and 16V, i want also that the output is between 6V and 13.9 V, please have you an idea about this ?

 

[gadly]

Re: limit voltage to 13.9V

Is this a voltage reference or a power supply (etc...)? (determines how efficient/accurate the solution must be). For example, you could do it with a resistor and a zener diode if this is a simple reference and accuracy and efficiency are not important. Please give more detail on your specification/requirements.

 

[jeffrey samuel]

Re: limit voltage to 13.9V

if you use a resistance capable of dropping such a voltage then the lower cut off of 6v can not be maintained at the op and also take into consideration the resistance of the load as well in calculating the resistor

connect your ip in series with the calculated resistor and then your load the net op will be around your 6 - 13.9 V region but never have the same voltage 6v at op for an ip of 6v

 

[yassin.kraouch]

Re: limit voltage to 13.9V

this is not a voltage reference, this is w power supply, the consumption is about 500 mA, i want to not exced 13.9 V in my design

 

[jeffrey samuel]

Re: limit voltage to 13.9V

if the resistor is properly chosen then the op voltage will never exceed 13.9 V

 

[yassin.kraouch]

Re: limit voltage to 13.9V

if you use a resistance capable of dropping such a voltage then the lower cut off of 6v can not be maintained at the op and also take into consideration the resistance of the load as well in calculating the resistor

connect your ip in series with the calculated resistor and then your load the net op will be around your 6 - 13.9 V region but never have the same voltage 6v at op for an ip of 6v

i didn't understand the solution that you propose, can you please explain ?

 

[jeffrey samuel]

Re: limit voltage to 13.9V

just use a resistor in series with the source there will be a voltage drop

if you are going for fixed load (load impedance is constant) then the single resistor will suffice

but 1 thing is that in this design the desired 6V op for 6V ip is not possible

this is also solved as your ip has a range of about 6 t0 16V

just the resistor having low tolerance will suffice your need

 

[gadly]

Re: limit voltage to 13.9V

I think I know what you're trying to do. The easiest way is probably to use a low drop out linear regulator similar to the LM317, with the output programmed to 13.9V. The output will (more-or less) track the input at low voltages, until it gets to the programmed voltage and then it will stick at 13.9V as the input rises above* 13.9V. For an example, see the 5V VOUT vs. VIN characteristic on page 6 of the LM117 / 317 data sheet:

http://www.ee.buffalo.edu/courses/elab/LM117.pdf

But the output will always be below the input by an amount equal to the dropout voltage (usually 1 to 2 volts). If you want the output to be exactly equal to the input, you will need to use a switch mode power supply design which behaves the same way. This will also give you greater efficiency but will cost you more in terms of design effort, component count, circuit complexity etc. Hope this helps.

* Footnote: the input will have to be (13.9V + dropout voltage) before the output stays at 13.9V.

 

[jeffrey samuel]

Re: limit voltage to 13.9V

* Footnote: the input will have to be (13.9V + dropout voltage) before the output stays at 13.9V.

do we necessarily have to go to smps when we can achieve the same with a simple resistor

 

[Raza]

Re: limit voltage to 13.9V

You can use a series regulator and can limit the out put maximum voltage to 13.9 volts. How you will change the input voltage? Will it be supplied gradually changed, manually or auto? If manually you can use a variable supply regulator like LM317 or any LDO series regulator.
There are some circuits for your reference:
https://www.radio-electronics.com/i...rent_limiter/power_supply_current_limiter.php

**broken link removed**

Hope it helps.