Electronics > Beginners
Regulated 9 volt dc power supply from 115 volt AC
fixit7:
I would like to build a regulated 9 volt D.C. power supply that uses 115 v AC to supply low current circuits.
The plan I found uses a power transformer, voltage regulator, zener diode, transistor, and some capacitors.
My wall transformer puts out .6 amp which is more than I need. There is no way to take it apart without destroying it.
It weighs 44 grams( or about 2 ounces) so I am wondering if it uses a power transformer?
fixit7:
I checked my scale. A 500 g calibration weight weighed 499.76 g.
https://www.dropbox.com/s/6f6y2ibp9as6bwt/9VoltPowerSupply.png?dl=0
golden_labels:
It”s most likely an SMPS. Nowadays it is unlikely to have transformer→rectifier→regulator scheme found in common consumer goods. Too bulky, too expensive, not really needed.
You may get those in an integrated, potted form for mounting on PCBs. See MYRRA 47201 as an example: 9V / 830mA / 7.5W / 80% eff / 100–240VAC input / 56g weight.
MarkF:
I would build the basic linear supply with a 9V three terminal regulator. As a bench supply.
I would stay away from a switching boost/buck regulator to eliminate the noise from the switching frequency.
(Unless you need to drop a lot of voltage across the regulator.)
fixit7:
I just need to supply less than 250 ma.
The weight of the circuit is not an issue.
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