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Variable Power Supplies
Power Supplies -- Main Page
Variable Power Supplies:   #'s - A       B - L         M - Z
 

Last Updated: October 24, 2017 02:55 PM

Circuits Designed by Dave Johnson, P.E. :

Nine-Volt Battery Eliminator - If you use 9v battery powered devices for long periods of time, you may get tired of constantly changing batteries.  The circuit below can be wired into any 9v battery powered device, drawing power from an external AC to DC power adapter.  I designed the circuit. . . Circuit by David A. Johnson P.E.-December, 2009

Touch Switch 240VAC - This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

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. . . Circuit by David A. Johnson P.E.-July, 2000

Voltage Boost - In this design a marginal AC to DC linear power supply provides a voltage boost, so it can maintain regulation at low line voltages.  The added components are wired at the AC input and the + DC output of an existing bridge rectifier circuit.  The components act as a full wave “charge pump” which will boost the DC output voltage across the main filter capacitor C3.  Without the boost circuit, when the AC line voltage drops to 105vac, the DC output voltage only reaches 11.5 volts, too low for a 12v voltage regulator. . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006


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

MIC2527 Voltage Drop, Packaging & PCB Layout-  App Note 30 -- MIC2527 Voltage Drop, Packaging, and PCB Layout __ Designed by Micrel

Mini-Drill Variable Power Supply-  T1 steps down AC voltage from 115VAC ( Tony van Roon's or 220VAC) to about 8VAC and is then rectified via bridge rectifier BR1 to about 11.52Vdc.  C1 filters off the AC ripple.  If you find the circuit output too noisy add another electrolytic capacitor over the output terminals.  Value can be between 10 and 100uF/25V.  The output voltage is variable with the 10K-potentiometer while keeping the current constant __ Designed by Tony van Roon  VA3AVR

Multiple Voltage Power Supply-  Schematic only, no circuit description __ Designed by Andy Wilson

National Semiconductor Dual High-Current Power Supply Kit-  The National Semiconductor Power Supply Kit is designed around the National LM2636, a synchronous buck regulator.  It provides over 28 amps of current with variable output voltages ranging from +1.3V to +3.3 V. __

Nine-Volt Battery Eliminator-  If you use 9v battery powered devices for long periods of time, you may get tired of constantly changing batteries.  The circuit below can be wired into any 9v battery powered device, drawing power from an external AC to DC power adapter.  I designed the circuit. . . Circuit by David A. Johnson P.E.-December, 2009

Over / Under-Voltage Protection Of Electrical Appliances-  This circuit protects refrigerators as well as other appliances from over and under-voltage.  Operational amplifier IC LM324 ( IC2) is used here as a comparator.  IC LM324 consists of four operational amplifiers,...__ Electronics Projects for You

Over/Under Voltage Cut-Out-  This over/under voltage cut-out will save your costly electrical and electronic appliances from the adverse effects of very high and very low mains voltages.  The circuit features auto reset and utilises easily available components.  It makes use of the comparators available inside 555 timer ICs__

Paralleled Voltage Regulators with Balanced Load Sharing-  Paralleling voltage regulators to provide mode load current is a common technique.  Forcing the amplifiers to share the load current equally is called ballasting.  Using a precision low offset voltage amplifier to sense the output current from each regulator requires just milli-ohms of resistance, typically just a pcb circuit trace.  Each amplifier then adjusts the output voltage of each regulator to force the output currents to be equal. __ Linear Technology/Analog Devices App Note, Mar 16th 2010

Part 1: 200W-48 AdvancedTCA Hot Swap Controller with I2C Input/Output Monitoring & Power Good Watchdog-  The LTC4261 negative voltage Hot Swap controllers allow a board to be safely inserted and removed from a live backplane.  Using an external N-channel pass transistor, the board supply voltage can be ramped at an adjustable rate.  The devices feature independently adjustable inrush current and overcurrent limits to minimize stresses __ Linear Technology/Analog Devices App Note, Mar 26th 2010

Part 2: 200W-48 AdvancedTCA Hot Swap Controller with I2C Input/Output Monitoring & Power Good Watchdog-  The LTC4261 negative voltage Hot Swap controllers allow a board to be safely inserted and removed from a live backplane.  Using an external N-channel pass transistor, the board supply voltage can be ramped at an adjustable rate.  The devices feature independently adjustable inrush current and overcurrent limits to minimize stresses __ Linear Technology/Analog Devices App Note, Mar 26th 2010

Power Supply (PSU 3)-  I have done some work with DC PSUs over the past few months but some of the designs were either complex or "basic performers".  I therefore decided that it was about right to produce a bench PSU that was simple enough to be made into another kit and have a reasonable performance too. __ Designed by Harry Lythall-SM0VPO

Power Supply Accepts Wide Input-Voltage Range-  02/17/11  EDN Design Ideas:  A SEPIC-based power supply runs from 1.5V to 20V.  The switching power supply in Figure 1 produces 3.3 V dc from an input voltage of 2.5 to 20V dc with high efficiency.  The circuit operates at an input voltage as low as 1.5V once it starts from a minimum of 2.5V dc, allowing the switcher to fully discharge a pair of alkaline cell batteries nearing end of life.  The power supply can also run efficiently off higher input voltages, such as 12V automotive power.  The heart of the circuit is a SEPIC (single-ended-primary-inductance-converter) -based switching power supply, which provide as an output voltage greater than or less than the input voltage (Reference 1). __ Circuit Design by Jim Windgassen, Northrop Grumman Undersea Systems, Annapolis, MD

Secure Bootstrap Operation under Light Load-  05/12/11  EDN Design Ideas:  Additional circuit lets a capacitor charge, preventing voltage dips.  A previous Design Idea highlights a potential issue of a bootstrap IC under light-load or prechargedload operation (Reference 1).  The circuit in Figure 1, with the additional circuit in the green box, fixes the problem of a voltage dip in the bus-voltage signal.  The waveforms in Figure 2 demonstrate how this problem takes place in buck converter IC1B when its output voltage, VBUS, dips below the regulation point at a fixed rate under no load.  By inspecting the other traces in Figure 2, you can conclude that the dip of VBUS occurs __ Circuit Design by Chee Hua How

Self switching Power Supply-  One of the main features of the regulated power supply circuit being presented is that though fixed-voltage regulator LM7805 is used in the circuit, its output voltage is variable.  This is achieved by connecting a potentiometer between common terminal of regulator IC and ground.  For every 100-ohm increment in the in-circuit value of the resistance of potentiometer VR1, __

Simple Circuit Variable Voltage Source-  The high current regulator below uses an additional winding or a separate transformer to supply power for the LM317 regulator so that the pass transistors can operate closer to saturation and improve efficiency.  For good efficiency the voltage at the collectors of the two parallel 2N3055 pass transistors should be close to the output voltage.  The LM317 requires a couple extra volts on the input side, plus the emitter/base drop of the 3055s, plus whatever is lost across the ( 0.1ohm) equalizing resistors ( 1volt at 10 amps) , so a separate transformer and rectifier/filter circuit is used that is a few volts higher than the output voltage __ Designed by Bill Bowden

Small Variable power Supply-  Features: 1.3-12.2 V, 1 A, over-current protection.  This is a simple but reliable device based one of the oldest integrated voltage regulators of them all - the LM723. __ Designed by Aaron Cake

Solar Panel Regulator-  This handy solar panel regulator measures the voltage across your battery or the charging current and will disconnect the panel to stop overcharging.  It works with 12V or 24V systems and has a 3.5-digit liquid crystal display.__ SiliconChip

Three-V supply Delivers 12V p-p to piezo speaker-  10/16/03  EDN Design Ideas:  Low-profile piezoelectric speakers can provide quality sound for portable electronic devices, but they require voltage swings greater than 8V p-p across the speaker element.  Yet, most portable devices include only a low-voltage pow __ Circuit Design by Royce Higashi and Tony Doy, Maxim Integrated Products, Sunnyvale, CA

Touch Switch 240VAC-  This is another capacitance based touch on/touch off switch, which can control power to a 200 watt 240vac load . . . Hobby Circuit designed by Dave Johnson P.E.-February, 2002

Use a Three-Phase Rectifier & Voltage Reducer for Offline Single-Phase Supplies-  EDN-Design Ideas -- 04/06/12  Missing diodes create gaps to allow voltage reduction. __ Circuit Design by JB Castro-Miguens, Cesinel, Madrid, Spain; C Castro-Miguens, University of Vigo, Spain; M Pérez Suárez, University of Vigo, Spain; and A Abal Pena, Tekplus, Vigo, Spain

Variable 3 to 24 Volt/3 Amp Power Supply-  This regulated power supply can be adjusted from 3 to 25 volts and is current limited to 2 amps as shown, but may be increased to 3 amps or more by selecting a smaller current sense resistor ( 0.3 ohm).  The 2N3055 and 2N3053 transistors should be mounted on suitable heat sinks and the current sense resistor should be rated at 3 watts or more.  Voltage regulation is controlled by 1/2 of a 1558 or 1458 op-amp.  The 1458 may be substituted in the circuit below, but it is recommended the supply voltage to pin 8 be limited to 30 VDC, which can be accomplished by adding a 6.2 volt zener or 5.1 K.  Page has several circuits, please scroll to find this one. __ Designed by Bill Bowden

Variable DC Power Supply-  This power supply is based on the LM317 Variable Regulator.  The input of the regulator needs to be around 28 Volts DC and it will output a DC voltage from 1.25vdc to 25 vdc.  To adjust the output voltage simply turn the 5k ohm pot.  The regulator will supply 1.5 amps of current Copyright 2000 [url=http://www.  home.  maine.  rr.  com/randylinscott/index.  html]Randy Linscott[/url]__

Variable DC Power Supply-  Voltage range: 0.7 - 24V; Current limiting range: 50mA - 2A __ Contact Flavio Dellepiane, fladello @ tin.it

Variable DC Power Supply-  A variable power supply with adjustable voltage and current outputs made with the L200 regulator. __ Designed by Andy Collison

Variable Dual LAB Power Supply-  Up to 800mA ( typical) output current at +/-25V. __ Designed by Rod Elliott  ESP

Variable HV power supply employs photovoltaic optocoupler-  07/14/14 EDN Design Ideas:  This unusual topology saved the day when a higher-voltage variable supply was needed. __ Circuit Design by sajjad Haidar

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. . . Circuit by David A. Johnson P.E.-July, 2000

Variable Laboratory DC Power Supply-  Voltage range: 0.7, 24V Current limiting range: 50mA, 2A A Variable DC Power Supply is one of the most useful tools on the electronics hobbyist's workbench.  This circuit is not an absolute novelty, but it is simple, reliable, "rugged" and short-proof, featuring variable voltage up to 24V and variable current limiting up to 2A.  Well suited to supply the circuits shown in this website.  You can adapt it to your own requirements as explained in the notes below. __

Variable load tests voltage sources-  07/19/01 EDN Design Ideas:  The circuit in Figure 1 serves as a variable, current-sink load for testing voltage sources.  You use digital commands to set the load current of the device under test over a wide range, independent- ly of the device under test's output voltage.  The circuit comprises an AD558 DAC, IC1, which provide as a reference voltage at Point A __ Circuit Design by Michele Frantisek, Brno, Czech Republic

Variable Power resistor load-  very useful and simple item __ Designed by Thomas Scherrer OZ2CPU

Variable Power Supply for the FM Transmitters-  This is a fairly simple, yet very versatile workbench power supply.  With a current limit of 1.5 amperes and a variable voltage from 2.7 volts to 16.5 volts on the output of the LM317T, this unit will come in very handy for your diversified electronic projects ( which usually include different DC voltages.  I have used it mainly for supplying my FM transmitters with different voltages, to see the different effects it has on the units.  In fact, I use it for all my FM transmitters.  It has served me well.  and is still serving proudly! __ Designed by braincambre500 @ yahoo.com

Variable Power Supply using a Fixed-Voltage Regulator IC-  A voltage regulator (also called a ‘regulator’) with only three terminals appears to be a simple device, but it is in fact a very complex integrated circuit.  It converts a varying...__ Electronics Projects for You

Variable Power Supply using Fixed Regulator-  This is a similar power supply that I used to power my FM Transmitter.  After suffering long problems with mains hum, this design using a pi filtered C-L-C approach.  This circuit offers excellent ripple rejection. __ Designed by David Celestin

Variable Power Supply with adjustable current limiting-  A Variable power supply with adjustable current limiting - new design! 0-14V output up to 5A current. __ Designed by Steven Weber, KD1JV

Variable Power Supply with Digital Control-  The most frequently used device in electronic workshops and laboratories is a universal power supply that provides a variable, fluctuation-free output.  Here we present a variable power supply with digital control...__ Electronics Projects for You

Variable Power Supply, 1-30V @ 1.5A-  This is a simple, but low-ripple power supply, and an excellent project if you're starting out in electronics.  It will suit your needs for most of your bench testing and prototype applications.  The output is adjustable from 1.2 volts to about 30 volts.  Maximum current is about 1.5 amps which is also sufficient for most of your tinkering __ Designed by Tony van Roon  VA3AVR

Variable Voltage & Current Power Supply-  Another method of using opamps to regulate a power supply is shown below.  The power transformer requires an additional winding to supply the op-amps with a bipolar voltage (+/- 8 volts) , and the negative voltage is also used to generate a reference voltage below ground so that the output voltage can be adjusted all the way down to 0.  Current limiting is __ Designed by Bill Bowden

Variable Voltage Regulator-  The LM317T is a adjustable 3 terminal positive voltage regulator capable of supplying in excess of 1.5 amps over an output range of 1.25 to 37 volts.  The device also has built in current limiting and thermal shutdown which makes it essentially blow-out proof.  , __

Variable Voltage Regulator-  As Ron suggests, controlling the output voltage from a regulator can be made variable in three ways __ Designed by Ron J.

Varying Brightness AC Lamp-  In this circuit, an SCR is used to slowly vary the intensity of a 120 volt light bulb by controlling the time that the AC line voltage is applied to the lamp during each half cycle.  The circuit is directly connected to the AC power line and should be placed inside an enclosure that will prevent direct contact with any of the components.  To avoid electrical shock, do not touch any part of the circuit while it is connected to the AC power line.  A 2K, 10 watt power resistor is used to drop the line voltage down to 9 volts DC.  This resistor will dissipate __ Designed by Bill Bowden

Voltage Boost-  In this design a marginal AC to DC linear power supply provides a voltage boost, so it can maintain regulation at low line voltages.  The added components are wired at the AC input and the + DC output of an existing bridge rectifier circuit.  The components act as a full wave “charge pump” which will boost the DC output voltage across the main filter capacitor C3.  Without the boost circuit, when the AC line voltage drops to 105vac, the DC output voltage only reaches 11.5 volts, too low for a 12v voltage regulator. . . . Hobby Circuit designed by Dave Johnson P.E.-July, 2006


Variable Power Supplies:   #'s - A       B - L         M - Z

 


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



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