Electronic Circuits and electronic circuits, electronic schematics plus an extensive resource for hobbyists, inventors and engineers

DiscoverCircuits.com has links to 45,000+ electronic circuits, cross-referenced
into 500+ categories.    We have searched the web to help you find quick design ideas.

HOME Schematics Hobby Corner Dave's Circuits Electronic Resources Contact Info
Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches
Welcome to DiscoverCircuits.com - online since 2002

See Media Kit for
Advertising Opportunities

Attention Designers:  Please alert us by eMail if we have linked to sites
where your original material has been copied without your permission.
We will change to the LINK to your site.  
Thank you.

 

Circuits designed by David Johnson, P.E.
Last Updated on: Wednesday, October 18, 2017 05:04 AM

List of Dave's Circuit Designs

The contents & graphics of Discovercircuits.com are copyright protected.
LINKING to Dave's circuits is permitted but DO NOT COPY any files to your WEB SITE server

More  AC-DC Power Supplies

Low Power AC to DC Power Supply

When you need some DC power fully isolated from the AC power line, this circuit may be just the ticket.  The circuit uses an inexpensive tiny off-the-shelf 5mH common mode filter coil from with a split bobbin as a high frequency transformer.  The circuit routes short 130v pulses to the primary winding of the coil every half cycle of the 60Hz line frequency.  It uses a silicon bilateral voltage triggered switch called a “sidac” to discharge a 0.1uF high voltage capacitor.  
By winding about 10 turns of wire on the secondary of the common mode coil, enough voltage is produced to charge up a 470uF capacitor through a bridge rectifier to activate a 5v regulator.  The amount of power produced by discharging the 0.1uF capacitor is enough to provide about 20ma of current from the regulated supply.  For many applications, this is sufficient power.  If more power is needed, the value of the 0.1uF capacitor could be increased.  For 240vac, 50Hz power lines, the value of the 0.1uF capacitor should be decreased to 0.047uF with a 600v rating and a 280v sidac should be used.

A “SIDAC” operates much like a two terminal TRIAC.  The device has a large negative resistance characteristic.  Once the trigger voltage is exceeded, the device switches on and forms a low impedance current path.  The current continues to flow until it drops below the device’s holding current, at which the device switches off again. The switch can handle about 20 Amps of peak current, which is perfect for quickly discharging a capacitor.  The energy stored in a capacitor is 0.5CV^2, where C is the capacitance in farads and V is the voltage.  A 0.1uF capacitor charged up to 130v stores 845 microjoules of energy.  Since the capacitor is discharged 120 times per second, the maximum power available from this type of circuit is 100mw.  For 240v systems, I would recommend a 280v sidac and a 0.047uF capacitor, rated at 600v. With those changes, the power available will increase to about 200mw.

6.8mH Common Mode Coil Sidac

Click on Drawing Below to view PDF version of Schematic

Low Power AC to DC Power Supply designed by David Johnson


More  AC-DC Power Supplies

Master Category List - Dave's Circuits
eMail David A. Johnson, P.E. about this circuit

 


Imagineering Ezine    Discover Solar Energy Dave Johnson & Associates Faraday Touch Switches



 About Us   |  Advertise on DiscoverCircuits.com   |   Report Broken Links  |    Link to DiscoverCircuits.com  |   
Privacy Policy


Discovercircuits.com endeavors to credit original designers.   Please alert us by eMail so we can
delete links to material that have been copied without your permission
.   Thank you.


© Copyright of all original material on this website is the property
of David A. Johnson, P.E. (Dave Johnson & Associates ) unless otherwise noted.  

Linking is ALLOWED but COPYING any content or graphics to your web site is EXPRESSLY PROHIBITED.
All material is provided "as is" without guarantees or warranty of any kind, either expressed or implied.