Converters: AC to AC Circuits K-Z

AC to AC Converters (AC to AC Power Supplies and Transformer Circuits) Page 3
AC to AC: #-I J K-Z Converters -- Main Page
Last Updated on: Thursday, October 29, 2009 06:09 AM

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.

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

Line Driver uses Push-Pull Vacuum Tube Cascode Follower - AS021 Jenson Transformer Application Note (app note 6/07)

Line Driver with Feedback Around the Transformer - AS025 Jenson Transformer Application Note (app note 11/02)

Line Level 2-Way Splitter/Isolator- AS041 Jenson Transformer Application Note (app note 6/07)

Line Output/Flyback Transformer Tester - This is a 'ringer'-type tester I (Bob Barker) originally designed for in-circuit testing of Line Output (Flyback) transformers in TVs and computer monitors. After a couple of technician-years of evaluation in actual servicing situations, it's also proved to be helpful in locating shorted diodes, capacitors and deflection yokes in horizontal deflection stages. LOPT/FBT condition is shown on an 8 LED 'bargraph' display. (circuit / schematic design added 9/06)

Low Noise version of High Level Output Stage in 1031 - AS033 Jenson Transformer Application Note (app note 11/02)

Low Noise, High Isolation Line Receiver for Low-Z Sources - AS035 Jenson Transformer Application Note (app note 11/02)

Low-Z Line Isolator with Termination Switch - AS009 Jenson Transformer Application Note. For used with long 600 ohm lines that need termination (app note 5/02)

Method Sets Voltage in Multipleoutput Converters - 02/01/01 EDN-Design Ideas:.....(design idea added 05/03)

Mic Input Isolation for Mackie Mixers - AS057 Jenson Transformer Application Note (app note 11/02)

Mixed Feedback Drive for Audio Output Transformers - Technical paper from Lundahl Transformers in PDF format (added 4/02)

Modification for Mic Inputs of Mackie 1604 Mixer - AS058 Jenson Transformer Application Note (app note 6/07)

Novel circuit controls ac power - 01/07/99 EDN-Design Ideas: The simple and inexpensive power-control circuit in Figure 1 uses a readily available fan regulator with built-in phase control. Such fan regulators are limited to approximately 100W. The circuit in Figure 1 adds two SCRs and a few components to turn the humble fan regulator into a mighty power controller. The fan regulator operates with).....(design idea added 08/05)

Output Amplifier to Upgrade Neve BA282AV Circuit Board - AS084 Jenson Transformer Application Note (app note 6/07)

Parasitic Capacitance Effects in Step-Up Transformer Design - AN39 Linear Technology This note explores the causes of the large resonating current spikes on the leading edge of the switch current waveform. These anomalies are exacerbated in very high voltage designs. (app note added 7/06)

Passive Output for Crystal D/A Converters - AS093 Jenson Transformer Application Note (app note 6/07)

Passive Stereo Matrix for M-S Mic Technique - AS065 Jenson Transformer Application Note (app note 11/02)

Phantom Power the Realistic PZM Mic - AS070 Jenson Transformer Application Note (app note 6/07)

Phase Splitter with Symmetrical Outputs - AS060 Jenson Transformer Application Note (app note 11/02)

Power Supplies & Regulators - includes several designs, scroll down. new low power discrete switcher (added 7/03)

Power Supplies & Transformers - Basic structures of power supplies (added 4/02)

Proper Grounding Inside Equipment Avoids Ground Noise Coupling - AS085 Jenson Transformer Application Note (app note 6/07)

Provide J-Box Consumer to Studio Interfaces - AS081 Jenson Transformer Application Note (app note 04/03/02)

Real Mic Inputs & Phantom Power for Sony DAT - AS037 Jenson Transformer Application Note (app note 11/02)

Receiver for Very Long Line Applications - AS005 Jenson Transformer Application Note (app note 6/07)

Ribbon Mic Matching Transformer - AS067 Jenson Transformer Application Note (app note 6/07)

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.... ….(designed by David A. Johnson)

Signal transformer application - Coilcraft Power Magnetics Application Note (app note added 6/06)

Simple One IC Stage Mic Preamp - AS017 Jenson Transformer Application Note (app note 7/02)

Simple Switching Regulator - includes several designs, scroll down to find this one. When batteries..... (added 8/03)

Simplified Measurement of Output Impedance - AS048 Jenson Transformer Application Note (app note 6/07)

Single Stage Low-Noise IC Mic Preamp - AS018 Jenson Transformer Application Note (app note 6/07)

Single Stage Mic Preamp with Two DC Servos - AS019 Jenson Transformer Application Note (app note 6/07)

SRPP-Input Tube Amplifier For Headphones & Loudspeakers - This transformer-coupled design uses a series regulated push-pull input stage and a parallel-triode cathode bias output stage. The audio output transformer is hand-wound from a kit. The amp will drive both headphones and speakers. Designed by Tony Frazer (circuit design added 01/08)

Standard Musical Instrument or Synthesizer Direct Box - AS007 Jenson Transformer Application Note (app note 6/07)

Step Down Rectifier Makes a Simple DC Power Supply - 04/09/98 EDN-Design Ideas: -A simple and useful nonisolated rectifier features voltage step-down operation, acceptable Class A line-current harmonics, inherent short-circuit protection, and, optionally, a regulated output.....(design idea added 04/02)

Stereo Headphone Driver uses LM6325 Current Booster - AS044 Jenson Transformer Application Note (app note 6/07)

Stereo to Mono Combiner for Balanced Systems - AS080 Jenson Transformer Application Note (app note 6/07)

Sync Conversion for Magna-Tech 69C Repro Amplifier - AS039 Jenson Transformer Application Note (app note 6/07)

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 added 8/03)

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)

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)

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

Transformerless Power Supply (Aaron Cake) - (circuit / schematic design added 08/08/08)

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 ....(added 11/05)

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....(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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