Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

AC to AC step down converter circuit 110V AC to 40V AC, not a transformer

Status
Not open for further replies.

average_male

Newbie level 3
Joined
Nov 10, 2008
Messages
4
Helped
2
Reputation
4
Reaction score
1
Trophy points
1,283
Activity points
1,305
Hello,

Aside from using a transformer, how could I supply my circuit with 40V AC [500mA (12VA) or more] given a standard 110V AC (standard wall power)?

My goal is to make a self-contained project box that houses its own power supply circuit rather than using a bulky transformer.

Any key terms to search against or part numbers or URL references [minus google.com :)] would be greatly apprecieated.

Thanks,
Moe
 

If you need DC then you can use a line operated switching regulator which can be made quite small.

For AC you will need to use a standard bulky transformer.
 

Here are a couple of theoretical alternatives to a transformer, since you ask...

Your specs imply a load of 80 ohms. You want to drop mains AC to about 1/3 its voltage.

If this load is constant then you can install a 600mH coil inline with the mains AC. This particular henry value will create 160 ohms of impedance at 60 Hz. The coil will be about the same size as a transformer. It must handle 700mA peak (56 W).

Or theoretically you can install an 11.6 uF capacitor inline. That is the value that creates 160 ohms of impedance at 60 Hz. It is risky to reduce mains AC by capacitive drop, which is why you won't see it recommended for more than small current needs (such as an LED). You are asking for 700 mA peak.

A bulky transformer remains the most reliable method.
 

Actually, I can supply my project box with 40VDC, so I am guessing they make a 110V AC to 40V DC converters? What would I search for if I need such a thing?

Thanks,
Moe
 
Last edited:

40V is higher than the everyday range of DC adapters.

If you want to include the power supply in your project enclosure, there's always the idea of making your own.

The easy type is a full-wave bridge supply. It uses a transformer, full-wave bridge rectifier, and smoothing capacitor. A fuse is a good idea. And a switch if you need one.

The transformer can be between 35 and 40 V. Rated to provide 500mA (or up to 1A to provide a cushion). By using a transformer you are isolated from mains AC.

Diodes should be 100V reverse rating. 1 A (or 3A for a cushion).

The smoothing capacitor can be 1000 uF to 2200 uF. It depends on how much ripple you can tolerate.

A switched-coil supply is another option (as Crutschow stated). It will be harder to design and construct one. You won't have isolation from mains AC, unless you use a flyback which contains a transformer.
 

Status
Not open for further replies.

Similar threads

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top