need help about Power design.~~

[wontall]

i need high-precision Power with 3 ports out in 1A(+12.00v,-12.00v,+500v).
I have already designed +12.00v with high precision .
the next, i wanted to use dc-dc to change +12.00v to +5.00v and to
-12.00v. but the problem is that: when i do it like this way, the other two
out ports volage can not keep the high precision as the 12.00v does.

what can i do~~ :idea:

 

[alphi]

One DC-DC circuit can not generate two precise output voltage!
1st:use two dc-dc to do .
2nd:use one dc-dc circuit,then use a LDO to generate another output.

 

[wontall]

One DC-DC circuit can generate two output voltage,really is not preciouse enough. I think the reason of it maybe is that many DC-DC IC are be designed by switch-power, as we konw , The switch power can not generate preciouse voltage as the linar-power does.you know,many
inductance make precious volage impossible.
SO Can anyone can tell me which DC-DC IC can generate preciouse voltage.or CAN GIVE ME ANOTHER IDEA?

THANKS` :?: :idea:

 

[alphi]

switchmode power supply can generate precise voltage!!!
the difficult of precise voltage with dc-dc is ripple/noise and loop controling.
much inductor can reduce ripple,but I think you can use more useful idea to do it!
1st: using zero ripple of switchingmode power supply,suggesting cuk topo.
2st: increase frequency to reduce filter and reduce ripple.
3st: increase loop response speed.
and more......

 

[wontall]

alphi
you are so kind~~!!!!!!!!!!!!!!!!!!!!!!!!!! :wink:
i am a newbie from china,you know ,english is not my mother language
you suggest me that:"1st: using zero ripple of switchingmode power supply,suggesting cuk topo."
but i can understand "cuk topo". what is "cuk topo" i can not search it by google

 

[Cluricaun]

Hi

He is reffering CUK topology, I have no good papers or URLs I am afraid but you can try here for more info. Or search for CUK topology.

hxxp://www.boostbuck.com/TheFourTopologies.html
hxxp://www.analogzone.com/col_0106.htm



Nt very much of information but i hope it helps a little.
/Cluricaun

 

[Mr.Cool]

you might also consider using current mode PWM controller IC as you can get a much faster response to transients. for example, unitrode 1844A or related families

Mr.Cool

 

[alphi]

you can use google to find it,many ic company have many cuk dc-dc chip for special application.that is best reference for you!