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# How to convert 1 power source to few regular supplies?

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#### ericmar

##### Full Member level 5
If I get a main power source using an AC-DC power adapter (12V@3A), is it possible to step down to few stable and regular supplies such as +3.3V, +5V, +9V and -9V? Can use voltage regulator such as 7805, 7809, 7909 to achieve?

Thanks for any help in advance!

If the range of your insulated power supply is grather than :

( +9v ) - ( -9v ) + ( 2 x ( Vdropout ) )

Is possible, but just if the load have low current consumption.

Obviously, the single 12V you said above doesn't mach this case. Instead, you have to use a switched power supply.

+++

Voltage regulators will be fine, you wont be able to supply more than your initial 3A (infact you'll have some losses), but we frequently make boards with +3.3, +5 and -5 from one psu using voltage regulators. I wouldn't design a board that didn't use voltage regulators even if I only wante 5V and Gnd; it protect's the chip's we're testing.

i think it is possible u can use the regultors in series to obtain the variable power supplies.U acn tap the o/p from the regulators.and use it but the main problem in \s the current consumption of the load u have just watch out. I have made two powersupplies with a 15v 3 amps adaptor for one of my projects first i regulated 12v form the o/p of the 12v i connected a 5v regulator it worked fine the current consumption is about 750 ma for the over all circuit

andre_teprom said:
If the range of your insulated power supply is grather than :

( +9v ) - ( -9v ) + ( 2 x ( Vdropout ) )

Is possible, but just if the load have low current consumption.

Obviously, the single 12V you said above doesn't mach this case. Instead, you have to use a switched power supply.

+++
Does it mean I have to use some kind of transformer to provide me a negative supply in order for the negative voltage regulator?

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