Variable power supply with range 0 VDC to 24VDC

[crutschow]

Problem is power dissipation at 24Vdc/250mA, should decapitate
6W. too much high

Are you talking about switch mode power supply?

Yes, a switching power supply would have much higher efficiency and thus lower dissipation.
But note that switching supplies have a higher output noise level (from the switching process) so that could be a problem if you are trying to power sensitive analog circuits.
Also switch-mode supplies must be laid out carefully on a board with a very good ground layout (using a ground plane preferably) or they may not work properly.

 

[kushal nandanwar]

Yes, a switching power supply would have much higher efficiency and thus lower dissipation.
But note that switching supplies have a higher output noise level (from the switching process) so that could be a problem if you are trying to power sensitive analog circuits.
Also switch-mode supplies must be laid out carefully on a board with a very good ground layout (using a ground plane preferably) or they may not work properly.

I have try with LM2576, but can't get zero voltage. 1.2V is minimum.

 

[crutschow]

I have try with LM2576, but can't get zero voltage. 1.2V is minimum.

Not many switching regulators are adjustable down to zero volts.
Here's one that goes to 0.6V minimum.
If you really need to go to 0V you could add a silicon junction diode in series with the output (with some loss in regulation stability).

 

[KlausST]

Hi,

Are you talking about switch mode power supply?

--> SEPIC

Klaus

 

[kushal nandanwar]

Hi,


--> SEPIC

Klaus

Can you provide me reference design.

 

[KlausST]

Hi,

there are IC manufacturers.
TI, LT, NSC, ST... and a lot of others.

Usually they have selection guides. Look for SEPIC, look for application notes, look into the datasheets.
LT has good documents (for sure good ICs also).

I´d say you can´t get better informations than directely from the manufacturers. They want to sell their ICs ;-)

Klaus

 

[crutschow]

Klaus, since the input voltage is always higher than the output voltage I don't understand why you suggested a SEPIC design which are generally more complicated(?).

 

[KlausST]

Hi,

you are right.

But 1V voltage drop for a step down is not much headroom. And if the input voltage drops a little (is it stabilized?) then you can not guarantee a regulated output voltage of 24V.
Here the benefit SEPIC has it´s benefit.

(But i had a wrong idea because of output voltage 0V.)
With both circuits (stepdown and SEPIC) you need to manipulate feedback voltage to get an output range of 0..24V.
(Here the SEPIC is no benefit)


Klaus