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Power Supplies / Converters: AC to AC
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Power Supplies -- Main Page


Last Updated: January 01, 2018 04:02 AM


Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:
0VAC to 280VAC Variable Isolated AC Voltage  -  I designed and built this circuit about 25 years ago.  It came in handy for many projects that were powered from 120 VAC, 240 VAC and 277 VAC.  It provides complete isolation from the power line.  It uses two 1:1 isolation transformers that are wired in parallel . . . Hobby Circuit designed by David A. Johnson P.E.-July 08, 2000

10W Amplifier using TDA2003  -  Here is the circuit diagram of a 10W audio amplifier using the popular TDA2003 IC from SGS Thomson.  The IC can easily deliver 10W to a 4 Ohms load at 18V DC supply voltage.  The IC can be also operated from 12V and that makes it applicable in car audio systems__ 

20ma Current Loop Tester  -  A while back I needed to test a circuit at 240vac.  Since I needed to safely test the circuit using my oscilloscope, I needed the 240vac to be fully isolated from the power line.  So, to step up the voltage, I bought a small isolation transformer from Digikey . . . Circuit by Dave Johnson P.E.-November 02, 2004

4-20ma Current Loop Tester  -  This circuit injects an adjustable current through a wire loop.  Using a digital current meter, the current can be adjusted from near zero to over 24 milliamps . . . Circuit by Dave Johnson P.E.-November 03, 2004

A Transformerless Power Supply  -  Power Supply Circuits:  This circuit will supply up to about 20mA at 12 volts.  It uses capacitive reactance instead of resistance - so it doesn't generate very much heat.  The circuit was designed to provide a cheap, compact power supply for CMOS logic circuits that require only a few milliamps.  The logic circuits were then used to control mains equipment, using an optically-isolated TRIAC. __ Designed by Ron J.

AC Couple Analog Signals without a DC Bias Source  -  02/03/00 EDN Design Ideas:  A conventional ac-coupling circuit in a single-supply system comprises a series capacitor and a shunt resistor to ground.  Unfortunately, negative peaks of  input signal can exceed 0.   3V input operating-range limits of an ADC, such as  LTC1402 serial 12-bit sampling ADC.  To avoid going below ground, circuit must return  shunt input __ Circuit Design by Joseph Luis Sousa, Linear Technology Corp, North Chelmsford, MA

AC Current Monitor  -  This circuit uses a small AC current transformer from Magnetek to produce an isolated voltage proportional to the AC current in the primary winding.  The transformer contains a single turn primary with a low 0.  001-ohm resistance.  It can easily handle 30 . . . Hobby Circuit designed by David A. Johnson P.E.-July 10, 2006

Algorithm tests for point location  -  08/03/00 EDN Design Ideas:  A recent software project approximated the phase-space trajectory (also known as a strange attractor) of a certain dynamic system by using several nonoverlapping triangles.  It became necessary to determine whether particular opera __ Circuit Design by Lawrence Arendt, Manitoba HVDC Research Centre, Winnipeg, Canada

Algorithm Transforms Filter Coefficients  -  01/21/99 EDN Design Ideas:  To synsize infinite-impulse-response (iiR]-filter functions, expressed as H (z], you commonly use analog prototype-filter functions, expressed as H (s], using  bilinear-z transform.  This operation entails some algebraic complexity in calculating  filter coefficients.  The simple algorithm shown here transforms  prototype-filter coefficients (W0, W1, W2]to  iiR digital-filter coefficients (U0, U1, U2].  These coefficients transform from __ Circuit Design by Frank Vitaljic, Bellingham, WA

An Acoustic Transformer Powered Super-High Isolation Amplifier  -  Application Note__ National Semiconductor

Application Of Ultra-Low-Power Converters In The Iot  -  it is predicted that there will soon be 25 billion permanently-connected sensors to implement the internet of Things (ioT) in real time. But the challenge is how these devices connected across__  10/20/2016 - EFY

Balun Transformers  -  Application Note__ MiniCircuits.com

Caps Provide Voltage Boost to Series Regulator  -  This circuit adds some capacitors and diodes to a traditional transformer type series regulator circuit to extend the normal operating range.  It can insure regulation during low line voltage conditions or it can squeeze a few more watts out of a plug-in-the-wall power adapter power supply . . . Circuit by David A. Johnson P.E.-December 24, 1998

Classic Plus & Minus DC Power Supply  -  This is a classic example of a regulated DC power supply that produces both a positive 15v and a negative 15v from a 20vac wall adapter . . . Circuit by David A. Johnson P.E.-December 13, 2004

Connect Line-Level Signal to Phono Input   -  The circuit does two functions: signal level attenuation and inverse RiAA filtering.  The signal attenuation is needed to convert the 500 mV signal to 2.5 mV signal.  The inverse-RiAA filtering is needed to make the frequency response of the system flat (same equalization that is used when music is transferred to vinyl in the studio).  The picture blow shows the frequency response of the ideal inverse-RiAA filter __ Designed by Tomi Engdahl

Convert 1 to 5V Signal to 4- to 20-Ma Output  -  04/19/12  EDN Design Ideas:  Despite the long-predicted demise of the 4- to 20-mA current loop, this analog interface is still the most common method of connecting current-loop sources to a sensing circuit.  This interface requires the conversion of a voltage signal—typically, 1 to 5V—to a 4- to 20-mA output.  Stringent accuracy requirements dictate the use of either expensive precision resistors or a trimming potentiometer to calibrate out the initial error of less precise devices to meet the design goals.   __ Circuit Design by Thomas Mosteller, Linear Technology Corp

Deemphasis Converter  -  The standard preemphasis time constant for FM broadcast in North America is 75 µs.  In Europe and most other places, it is 50 µs.  It's easy to change the deemphasis-network capacitors in a conventional tuner to convert from one standard to the other. However, this can't be done for DSP tuners such as the Sangean HDT-1X or Sony XDR-F1HD that implement deemphasis in firmware. These HD Radio tuners may be of interest overseas for their performance on analog FM. There also may be times when you want to use a 75-µs tuner on 50-µs signals without making internal modifications. __ Designed by Brian Beezley K6STI

Design High-Performance Pulse Transformers In Easy Stage  -  03/16/95  EDN Design Ideas:  raightforward circuit models aid analyzing and designing high-performance pulse transformers.  Practical design becomes easy, once you understand the fundamentals - Both analog and digital designers use pulse transformers to perform a multitude of functio __ Circuit Design by Vincent J Spataro, GEC Marconi Electronic Systems Corp

Everything you wanted to know about wideband, low-frequency transformers  -  11/23/00 EDN-Design ideas Wideband, low-frequency transformers are useful components in various passive circuits, such as the return-loss bridge (Reference 1 , Figure 2).  Figure 1a shows a conventional transformer.  If you connect the transformer windings differently, you can configure a transmission-line transformer (Reference 2 , Figure 1b).   __ Circuit Design by Richard Kurzrok, Queens Village, NY

Floating Supply for LCD Panel Meter  -    NOTE: Scroll down - Did you ever install one of those low-cost LCD panel meters in a project only to discover that it requires a floating power supply? I just did!  The meter cannot share a DC ground with the voltage to be measured. The above circuit came to the rescue.  It draws about 4 or 5 mA from the 9 volt supply and can supply up to 2 mA at 9 volts to the LCD meter or other load but the two capacitors isolate the grounds. Works like a champ!   __  Contact:  Charles Wenzel of Wenzel Associates, Inc.

Flyback provides isolated power conversion  -  01/07/99 EDN Design Ideas:  NOTE:  Mulitple ideas, Scroll to find this one.  A common requirement in telecommunications systems is to convert an unregulated 48V line to an isolated, accurate dc supply voltage.  The circuit in Figure 1 provide as a 5V, 15W output.  The circuit uses a UCC3809 primary-side controller, which can also control other single-ended converters.  The topology uses peak-current-mode control with a fixed-frequency oscillator.  The design is cost-efficient   Page includes several designs. __ Circuit Design by Philip Cooke, Unitrode Corp, Merrimack, NH

Grounding & Shielding  -  describes basic audio transformer uses like balanced in/out and signal splitters__ 

How RF transformers work & how they are measured  -  Application Note__ MiniCircuits.com

Introduction, Definition of terms, Q&As-tran14-2  -  Application Note__ MiniCircuits.com

Isolated AC Current Monitor  -  This circuit uses a small AC current transformer from Magnetek to produce an isolated voltage proportional to the AC current in the primary winding.  The transformer contains a single turn primary with a low 0.  001-ohm resistance.  It can easily handle 30 . . . Circuit by David A. Johnson P.E.-July 10, 2006

Isolated AC Voltage Spans 0VAC to 280Vac  -  I designed and built this circuit about 25 years ago.  It came in handy for many projects that were powered from 120 VAC, 240 VAC and 277 VAC.  It provides complete isolation from the power line.  It uses two 1:1 isolation transformers that are wired in parallel . . . Circuit by David Johnson P.E.-July 08, 2000

Isolation Transformer Circuits  -  A while back I needed to test a circuit at 240vac.  Since I needed to safely test the circuit using my oscilloscope, I needed the 240vac to be fully isolated from the power line.  So, to step up the voltage, I bought a small isolation transformer from Digikey . . . Circuit by David Johnson P.E.-May 29, 2011

Isolation Transformer Passes Millihertz Signal  -  08/04/94 EDN Design Ideas:  You can successfully use an ordinary low-cost line transformer as an isolation transformer in ac circuits that require floating sources.  However, at frequencies below 20 to 30 Hz, high distortion and excessive phase shifting occur.  The simple circuit in __ Circuit Design by George Kassabian, University of California, San Diego, CA

Isolator Transformer for Audio Lines  -  if you want to do the ground loop elimination in audio path, you have to cut the galvanic connection but pass the whole audio range.  The simplest and most common way to do the isolation is use audio transformer which is meant for audio use.  Transformers for audio use have some problems like __ Designed by Tomi Engdahl

Got Designs?
Please eMail
if you want me to link to and/or post your original design Thanks.


            Power Supplies / Converters: AC to AC:   #'s - K      L - Z 
Power Supplies -- Main Page


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