regulating smps output at a lower voltage

[doors666]

I am new here and its my first post.

I have a 24-0v 20A smps. I need to lower and regulate the voltage to about 21v without loosing on the current capability. any suggestions on how do i go about it.

 

[Tahmid]

The SMPS PCB might have an on-board potentiometer that you can adjust to change the output voltage. If not, you can adjust the values of the feedback resistors to get 21V output.

Hope this helps.
Tahmid.

 

[doors666]

thanx, but thats not an option. I cant change the smps. I need to get the full 24v and then lower it.

 

[Tahmid]

Why do you need the 21V in the first place? Just curious.

If you're going to be operating at approximately constant currents and very strict regulation on 21V isn't required, you can add a few diodes. But you must keep in mind the associated power dissipation.

If the load will be constant, you could also use a resistor to drop the voltage.

These are both linear regulation, voltage reduction actually (not regulation really), techniques. You'll have to deal with power dissipation of about 60W!

You should use a switching regulator for better efficiency. The downside would be the cost and complexity involved.

Hope this helps.
Tahmid.

 

[doors666]

Why do you need the 21V in the first place? Just curious.

If you're going to be operating at approximately constant currents and very strict regulation on 21V isn't required, you can add a few diodes. But you must keep in mind the associated power dissipation.

If the load will be constant, you could also use a resistor to drop the voltage.

These are both linear regulation, voltage reduction actually (not regulation really), techniques. You'll have to deal with power dissipation of about 60W!

You should use a switching regulator for better efficiency. The downside would be the cost and complexity involved.

Hope this helps.
Tahmid.

chip i am using wants max input of 22v, so the 21v need. i dont need exact value, but it shouldnt drop too much. about 20v min. I guess that isnt exactly regulated.
I would probably need about 25 amps capability to use 20a from the smps. cost is of course an issue, dont want it to be expensive.

dont really want to use resistor due to power dissipation, it will also be probably the sausage type, not suitable. For diodes, it will be 5 diodes in series with the correct ratings right and bypass caps right? Would this give me 'almost regulated' output. Any other ideas? also saw something on the web about using multiple lower powered regulator chips, how good is that option.