Please help with this power supply design

[EDA_hg81]

This power supply needs +2V to +15V adjustable DC voltage output and also requires 2A current sink ability.

Thanks for any ideas.

 

[alexan_e]

I'm not clear on what you are asking,
do you want a positive power supply that has variable output 2v to 15v and can source (provide) up to 2A?
What input voltage do you have?

Alex

 

[EDA_hg81]

I'm not clear on what you are asking,
do you want a positive power supply that has variable output 2v to 15v and can source (provide) up to 2A?
What input voltage do you have?

Alex

It has to be a positive power supply that has variable output 2v to 15v and but can sink up to 2A

It is hard to find one meet this requirements.

Thanks.

 

[alexan_e]

The sinking part is what i don't understand, can you please explain.
Where is the output going to be connected and you expect it to sink current?
It should be a load that already has higher voltage than the power supply.

Alex

 

[chuckey]

What you need is a shunt regulator. If you have a DC supply of say 17V with a 1 ohm resistor in series and you connect a "variable " zener diode to earth, then the output voltage will be set by the zener diode. so to get 15 V your "zener" must draw 2 A. If you want 2V output then your zener must draw 15 A. If some thing else tries to feed current in, its just soaked up by the zener.
So you get the picture. At low voltage and high current outputs, the beast dissipates a lot of heat. So you must have some sort of switching around the 1 ohm resistor so at low volt output you increase its value to 10 ohms, or even better use a switching regulator - scrs instead of diodes in the bridge rectifier. Another way would be to have a conventional regulator and at 1 mV above its set voltage the variable zener cuts in and soaks up any excessive current trying to increase its voltage output.
Frank

 

[EDA_hg81]

I really don't know there has variable zener.

Many my sincere thanks.

 

[alexan_e]

There isn't a variable zener but there are devices like TL431 ( https://www.fairchildsemi.com/ds/TL/TL431A.pdf ) that behave like a variable zener but is actually an integrated circuit.
chuckey is talking for a circuit like that but which will be able to work with high currents, is this what you want, a shunt regulator for 2A?

Alex

 

[saikat36]

Dear EDA_hg81,

What do u mean by 2A sink? Is it mean that ur PS must deliver 2A current to load or **** 2A current from the load?
Plz make it clear first.

 

[chuckey]

saikat36 to "sink" current is a valid electronic term. It means to absorb it with out any increase in voltage.
Frank

 

[Embedded_Geek]

You can use LM317 and use additional power transistors from input to output to get the desired current.

 

[saikat36]

Ok. Thanks