Converters: AC to AC Circuits

AC to AC Converters (AC to AC Power Supplies and Transformer Circuits)   Page 7
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Last Updated on: Friday, March 23, 2012 04:35 PM

Circuits Designed by Dave Johnson, P.E. :

Run Switching Type AC Power Adapters on DC
I have received a couple emails from people looking for inexpensive DC to DC converters, which can convert 40v to 60v DC into say +5 or +12v. Such input voltages are often found in new automotive and industrial applications with a typical DC voltage of 48 volts. It turns out that many, not all, but many, standard AC line operated power adapters, which use switch mode techniques, will indeed work great when supplied with DC instead of AC. The unit below works down to about 30v DC and delivers 500ma at 5v. If you draw less current, it will operate at even lower DC input voltages....

VARIABLE 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 for the140vac range and in series for the 280vac range. The selector switch also diverts power to the appropriate output socket to avoid mishaps in sending the wrong voltage to the load. My home-built unit also included an AC volt and amp meter to monitor the output. However, this circuit only indicates the AC power connections.

Variable AC Power Supply Circuit
In electronics, it is often handy to have a fully isolated variable AC power supply. With such a device you can safely test various AC powered circuits and even probe around in the circuit with an oscilloscope. The hobby circuit below was designed to provide up to 500 watts of AC over a range of zero volts to over 250vac....

Links to electronic circuits, electronic schematics, designs for engineers, hobbyists, students & inventors:

Telephone Ring Generator using 60hz Power Transformer - This ring generator will ring a telephone once every 10 seconds. The interval between rings can be lengthened or shortened by varying the value of the 1 Meg resistor. The 70 volt/ 30 Hz ring voltage is produced from the 120 volt side of a small 12.6 VAC power transformer.... [Design by Bill Bowden]

Teletronix LA2A Circuitry Modifications - AS091 Jenson Transformer Application Note (app note 6/07)

Theory & Construction of MIC Splitters - 5 page booklet in PDF format (added 4/02)

Three-Terminal Adjustable Regulators - The unregulated DC supply is a very common type and the simple regulator shown in fig. 1 may be added for projects that require a….(added 08/08/08)

Transformer Buys Lower Shutdown Current - 11/23/94 EDN-Design Ideas The step-up dc/dc converter in Fig 1 trades a slight loss in efficiency and a transformer in place of a less expensive inductor for two important advantages The inductor offers low shutdown current because the transformer eliminates a leakage path. The circuit stays in regulation, even....[Design Idea added 3/03] EDN is migrating links. This link is not verified. Search the "title" + "EDN" for new link.

Transformer Coupled Splitter - Active amplified transformer isolated signal splitter that enables hum-free connection of1-guitar to more than1-amp as well as having a direct output (added 5/02)

Transformer Driver Controls BiDirectional Switch - 07/17/97 EDN-Design Ideas You can use a transformer-driver IC to simply control a MOSFET on/off switch....[Design Idea added 3/03] EDN is migrating links. This link is not verified. Google the "title" EDN for new link.

Transformerless Microphone PreAmplifier - (circuit / schematic design added 6/06)

Transformerless Power Supply - Circuit designed by Ron J

Transformerless Power Supply (Aaron Cake) - I have received a few emails asking for a transformerless power supply. Here is such a supply. This supply uses no heavy step down transformer and has an extremely low parts count. The circuit can be built very small and can supply small currents for small projects. The major downfall of this supply is that it is not isolated from the AC line and can only supply small currents....

Transformerless Power Supply (jose pino) - Simple, low cost and easy to build power supply. Ideal for applications that doesn't requiere too much power. (5/28/2006)

Transformerless Power Supply (Len Galasso) - This power supply uses the reactance of a non-polarized capacitor at 60hz to step-down the voltage from the normal 117VAC level to about 20 volts or so, which is rectified by the diode….(Circuit design added 7/06)

Transformerless Power Supply (Ron J) - 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 desigusing an optically-isolated triac.... (added 6/03)

TTL Power Supply with ‘Crowbar’ protection - ….(electronic schematic added 08/08)

Tube Microphone Preamp Generic Input Stage - AS020 Jenson Transformer Application Note (app note 6/07)

Two JT-115K-E used in Symmetrical Mic Input Stage - AS047 Jenson Transformer Application Note (app note 6/07)

Ultra-High Performance Line Driver - AS027 Jenson Transformer Application Note (app note 6/07)

Ultra-High Performance Output Stage - AS026 Jenson Transformer Application Note (app note 6/07)

Unbalanced Long Line Driver/Isolator - AS056 Jenson Transformer Application Note (app note 08/08/08)

Unbalanced Polarity Inverter - AS042 Jenson Transformer Application Note (app note 08/08/08)

Universal Patchbay Isolation Application - AS046 Jenson Transformer Application Note (app note 08/08/08)

Upgrade of Active Balanced Input to Transformer Balanced - AS003 Jenson Transformer Application Note (app note 6/07)

Use Amplifier Phono Input as Line Level Input: Inverse RIAA Filter - 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... [Tomi Engdahl]

Using the JT-16-A with The Country Boy's Capacitor Microphone - AS076 Jenson Transformer Application Note (app note 6/07)

Variable AC Power Supply - In electronics, it is often handy to have a fully isolated variable AC power supply. With such a device you can safely test various AC powered circuits and even probe around in the circuit with an oscilloscope. The hobby circuit below was designed to provide up to 500 watts of AC over a range of zero volts to over 250vac.... [Hobby Corner Circuit by Dave Johnson]

Variable 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 for the140vac range and in series for the 280vac range. The selector switch also diverts power to the appropriate output socket to avoid mishaps in sending the wrong voltage to the load. My home-built unit also included an AC volt and amp meter to monitor the output. However, this circuit only indicates the AC power connections. …. [Designed by David A. Johnson]

Wheatstone Bridge Stereo to Mono Combiner Circuit - AS094 Jenson Transformer Application Note (app note 6/07)

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