# 2 x regulators for double current?

Discussion in 'General Electronics Discussion' started by qweets, Oct 18, 2010.

1. ### qweets

48
0
Sep 26, 2010
hello everyone : )

i have an old PSU for a HP printer that can output approx 18v @1.1amps
(which i believe is 19.8 watt)

My circuit however needs aprox 10v @1.5amps ( 15 watt)

I have two 10v regulators that offer 10v @ 1amp

So I wonder, can I use these 2 x regulators together in parallel with my PSU to provide my circuit with enough current?

thanks for any help. : )

2. ### Resqueline

2,848
2
Jul 31, 2009
The regulators themselves might be parallelled to get the required current, but here the PSU is the limiting factor with its 1.1A capacity.
Only by using a switchmode regulator off the PSU can you keep the wattage and get the neccessary higher current. It also needs to have a higher than 75% efficiency.

3. ### qweets

48
0
Sep 26, 2010

the regulators are "Linear voltage regulator,BA17810T 10V 1A" , i do not think they are switching type.?

i also have a PSU from an old PC ...i think it may be around 300watt with 12v

but i've just read the 10v regs need 12.5v minimum too work. ....typical. : /

hmm..not sure what to do now? I might look on ebay for a higher current psu? As i cant see a switching type regulator that will fit my bread & vero boards. not sure how that would work?

4. ### qweets

48
0
Sep 26, 2010
i just found a regulator that can output 2amps , so hopefully i'll be o.k with that and the 18v 1.1amp psu. fingers crossed. : )

thanks for your help. : P

5. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,418
2,788
Jan 21, 2010
You understand that unless it's a switchmode regulator that 2 amps out requires 2 amps in (actually a little more).

6. ### qweets

48
0
Sep 26, 2010
hi : )

i did not need the full 2amps, but yes i think i need to just buy a new ac/dc adaptor with a higher amp output.

I was told that I can up the amps in a step down conversion under certain situations.
So seems i need to disregard that in this instance.: /

thanks for your help : )

7. ### davennModerator

13,672
1,891
Sep 5, 2009
yes but the original PSU transformer still has to be able to supply the current you want
and the indication is that it cant.

D

8. ### qweets

48
0
Sep 26, 2010
thanks.: )

i just noticed a 10v 20 amp psu for sale. i wonder, would this have a standard 13 amp fuse in the plug? or a special fuse to provide the 20amps?

Last edited: Oct 19, 2010
9. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,418
2,788
Jan 21, 2010
I assume you're in the UK

That would have a mains fuse rated at around 2A as a guess.

I have no idea if/how the power supply might limit the output current.

10. ### qweets

48
0
Sep 26, 2010
yep, uk : )

So that would be 240v 2a converted to 10v 20a

Stepped down voltage, but the amps raised,

This is why i thought a 18v 1.1a psu might go to 10v 1.5a .

not to worry i have a psu that i may buy, should do the trick.

peace: )

11. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

25,418
2,788
Jan 21, 2010
The power supply you are talking about is either switchmode or has a transformer. Both devices can reduce voltage and increase current.

You are talking about a linear regulator which reduces the voltage but the current remains constant.

That's one reason why we use transformers to reduce the voltage before using a linear regulator to regulate the output voltage.