Converting 120V to 12V DC ~ 363 mA from live wire

Hi,

I understand there are adapters out there that already do this job, but I'm trying to avoid using a wall outlet all together. I'm looking to connect *to the live wires directly*, coming from the wall, and converting that down to 12v DC, ~363 mA through the means of either drivers, converters, or what have you. The most important detail I'm after is accomplishing this while keeping it as compact and flat as possible.

Instead of breaking an adapter apart and using the internal contents, is there anything any of you can recommend I buy/put together that can help me with this? Again, I'd like for it to be as small and compact as possible.

Thanks!

See attachment

Perhaps a bridge rectifier with ripple filter that feeds a simple high frequency PWM driven MOSFET to a capacitor with feedback that modulates the duty cycle so the capacitor stays charged to 12V -- not sure what your ripple requirement is, you left that little detail out. Might need to add some sort of current limiting to deal with inrush and an RFI filter to keep the PWM noise off the power lines. Also, make sure it's a capacitor that can handle the high frequency.

You could also do it with one or more series capacitors (in front of a bridge rectifier and ripple filter and 12V linear regulator or 12V zener -- something like that), but the capacitor would need to be rather large to accommodate ~363ma. But that is only recommended if the current demand is fairly steady, otherwise you'll seriously stress the regulator.

C = 1/(2πfXc)

Xc = (168-12)/363ma = 430Ω

C = 1/(2π60*430) = 6.2µF at around 250WVDC minimum

I would also add spike suppression at the 120VAC side unless you use a series cap with a voltage of at least 500V

Beyond that, it's a pretty complicated Switch Mode design.

Also, beware that such a circuit is EXTREMELY DANGEROUS!!! Only mess with this if you are experienced working with lethal voltages (as high as 170V)!!!! And only build it if you know how to isolate the circuit so it doesn't electrocute anyone!!!!!!!

120v to 16v transformer, bridge rectifier, 7812 voltage regulator, and a couple of filter caps.

It appears that what you need is a plain ordinary mains adaptor, either transformer/rectifier, or switched mode power supply which is smaller and lighter, but one which has a plug you can take off, as opposed to the type that is built into a plug.

Opening up an adaptor and using the internal circuit would still probably be the simplest option, unless you already have reasonable skills in electronic soldering and construction.

It will help us to advise you if you can tell us the purpose of this circuit, and what type of equipment you want to supply, and exactly what space the adaptor circuit has to fit into.

Can you please explain the size constrains. following are two schema
Scheme1:
Using transformer 15V/500mA as suggested by Mr. Clyde Purk. which includes:
1. Bridge rectifier or Half wave rectifier using 1N4007
2. LM7812 regulator.
3. 470uF/25V capacitor on input side of regulator
4. 100uF/25V capacitor on Output side of regulator

Scheme2:
Using Capacitive power supply. As explained by Mr. Steve Lawson. It is recommended to use X2 type of capacitor. Also these circuits will become bulky due to capacitors as current requirement increases. if the current required is below 100mA the this will be a good choice.
Use a 12V zener diode for regulation.

For smallest size, some sort of switch mode converter will be required -- this will allow physically smaller components, both because of higher frequencies and because switching rather than linear mode will produce much less heat.