Low voltage linear power supplies

Linear power supplies use dissipative regulator components to achieve regulation. This dissipative regulation means conversion of excessive power to heat. When using a linear regulator you have usually an unregulated power supply which gives somewhat higher voltage than your electronics needs. You put a dissipative regulator between the power source and your electronics circuit. This regulator keeps the voltage on the output stable (as long as the input voltage is high enough). The regulator itself converts the the power determined by voltage difference (unregulated voltage - output voltage) times output current to need.
Linear power supplies are generally easy to construct (there are very easy to use ICs for this or they can be built quite easily using discrete components) and can easily give good quality output voltage (stable output voltage and low noise). The disadvantage of them is low effiencely (lots of heat dissipated in power supply). The linear regulator used in regulated linear power supplies, utilises simple techniques of controlled energy dissipation to achieve a regulated output voltage independent of line and load variation. It is, therefore, inherently inefficient, especially when a wide input voltage range has to be catered for. When building a linear regualated power supply which takes mains voltage and outputs low voltage, the following parts are needed; a buly low frequency mains transformer, large heat-sinking is required to dissipate the heat generated by the regulating element and very large filter capacitors are required to store enough energy at the voltage to maintain the output for a reasonable length of time when the mains source is removed (during mains AC voltage zero crossing).

Theory

• A Designer's Guide to the L200 Voltage Regulator - STMicroelectronics Application Note in pdf format
• Change improves regulators reliability - standard circuit for adjustable, 3-terminal regulators (LM317, LM350, etc) suffers from a designed-in fault: If the potentiometer R2s wiper loses contact, the regulators output goes high
• DMOS delivers dramatic performance gains to LDO regulators - LDO regulators with pnp pass elements nearly obsoleted the early npn linear regulators
• Emitter-Follower Boosts Linear Regulator's Output Current - an external emitter-follower increases the output current while maintaining the low quiescent current of this LDO regulator
• Inside a Power-Cube Transformer - How those little things convert mains AC to safe low voltage DC
• Increasing Regulator Current - you can boost the available current output of 78xx series of voltage regulators with this circuit
• Keep linear regulators in their safe zone - thermal characteristics of regulators depend on their operating conditions and the system's load
• Method of Determining Secondary Current Ratings in D.C. Circuits
• Power supplies - theory
• Rectifier Applications Handbook
• Säädettävät regulaattorit - Example circuits how to use L200CV, LM317, LM317K and LM338K regulators.
• Transformer Facts Technical Bulletin No.1: Application Notes on Rectifier Transformers
• Tube Power Supply
• Understanding linear regulators - Linear regulators convert unregulated dc voltage to regulated dc voltage. are good vehicles to use to begin a voltage-regulator study.
• Unregulated Power Supply - sample circuits and some information which describes it's operation and calculation of component values
• Unregulated power supply design
• Using the 78xx Series Voltage Regulators
• Voltage regulators (stabilizers) 78xx a 79xx by ST - warning about some possible problem if the regulator load is too low
• Zener Voltage Regulator CALCULATOR

Unregulated power supplies

An unregulated power supply is by far the simplest linear power supply type. It consists of a mains transformer, rectifier and a output voltage filtering capacitor. The ac from the transformer secondary is rectified by a rectifier of some type. Typically a block rectifier or four individual diodes such as 1N4004 types are used as rectifier. In some applications a centre tapped transformer and two diodes are used for rectification. The principal advantage of a bridge rectifier is you do not need a centre tap on the secondary of the transformer. After the rectifier the power supplies generally have some form of filtering capacitor which converts the voltage from rectifier (varies between 0V and full rectifier voltage generally at twice of mains frequency) to a smooth DC voltage. An unregulated power supply generally gives somewhat higher output voltage when it is not loaded at all (genrally around 1.4 times nominal voltage). The output voltage starts to drop as the load increases, and they give the nominal output voltage at the nominal load current. If the load increses from this, the output voltage drips below nominal voltage until maximum output current is reached (after that some protective elements like overheating protector or fuse stops the excessive current from flowing). In general, most devices that are battery powered can handle a voltage of at least 10% higher. And they usually work also with somewhat lower voltages. This is because most transistors and Analog ICs are designed to work within a range of voltages. This is why an unregulated power supplies can be used with many such circuits. What is a "wall wart"? I'm sure you have a number of these things around; I sure do. These are those little (or not so little) black (but sometimes white) cubes with AC power connector blades on one face. You plug it into the wall and it converts the AC voltage to DC voltage at some specified current. Once you plug it into the AC outlet, it sits there like a black (or white) wart on your wall, thus the term of endearment, "wall wart." Typical wallwart includes an unregulated power supply as described above.
• 12V DC Power Supply - uses 12V 5A transformer and some basic components to give put unregulated +12V
• Dual Unregulated Power Supply for Audio Power Amplifiers - This kit is a quick, neat, and inexpensive way to provide a smoothed dual unregulated DC power supply suitable for powering many audio power amplifiers.
• Half-wave DC power supply - This is a simulation of a simple DC power supply based on a half-wave rectifier.
• Ian Purdie's Amateur Radio Tutorial Pages: Your Basic Power Supply Circuit - This is the circuit of a basic unregulated dc power supply.
• Power Supply for Battery Valve Radios - to make 90V DC and 1.5V DC for 7-pin valves used in old radios
• Reusing that Wall Wart, Revisited - This article gives ideas on how to decide to either reuse the unregulated Wall Wart as it is, or not.
• Unregulated Power Supply - basic operation described, useful general circuit for many different voltages

Fixed voltage regulated

• 12 Volt 30 Amp Power Supply - This circuit uses a single 7812 IC voltage regulator and multiple outboard pass transistors (TIP2955). This power supply can deliver output load currents of up to 30 amps.
• 12V RMS to 10V Voltage Regulator - will take a 12V RMS sinusoidal input from a transformer and provide a 10V DC output at 100 mA with very good regulation
• 12 Volt to 9 Volt DC Converter
• 48 Volt Phantom Power Supply - This is a simple 48 V regulated linear power supply design that will provide up to 60 mA of current. This circuit is based on the Texas Instruments TL783C high voltage adjustable linear regulator IC. This circuit is short circuit protected.
• 78xx regulator board - circuit board and ccircuit for making voltage regulators based on 78xx ICs, in pdf format, text in Finnish
• A constant 5 volts DC power supply - This is an example of a power supply to power anything requiring 5 volts DC. This circuit takes low voltage AC in (9-16V AC).
• Active preloading provides sinking capability - a simple add-on circuit enables a unipolar power supply, usually a current-sourcing circuit only, to sink current from a load
• Build a simple 13.8V Power Supply Unit - A power supply with output voltage of 13.8V and a current capacity of 5A.
• Car 12V converter - simple circuit to connect car 12V to 9V, 7.5V or 6V
• Circuit reduces VCC ripple in audio band - regulator circuit which reduces noise and ripple by at least 35 dB over the audio range of 100 Hz to 20 kHz and provides a clean source of 5V power for driving audio circuits in portable applications such as cellular phones and multimedia notebook computers
• DC power supply - simple circuit based on 78xx fixed voltage regulator IC, those ICs are available for some fixed voltages between 5 and 24V
• Discrete LDO Regulator - The discrete LDO design presented here came about because of the need for an LDO (low drop-out regulator) for 5V designs. There are better performing LDO parts, but they tend to be either single sourced or expensive. This one can be made from common components. The performance parameters are very crude : 5V nominal at up to 10mA from 6-16V.
• Explanamtion and experiment about regulated DC power supply - many power supply designs for different voltages, built from discrete components
• High Current Power Supply - takes very few parts and outputs up to 10A, regulation not very good
• Increasing Regulator Current - you can boost 78xx regulator output with one power transistor
• Linear supply uses switch-mode regulation - You can use simple circuits to implement small, regulated plug-in power supplies. This basic and versatile 5V supply uses a zener diode and an emitter-follower transistor.
• Logic PSU with Over Voltage Protection - 5 volt regulated power supply for TTL and 74LS series integrated circuits, includes output overvoltage fault protection
• Low-drop regulator - outputs 5V at 1A, constructed from discrete components, in postscript file format
• MOSFET circuit ups regulator's output current - use a current mirror and a power MOSFET to increase the output-current capability of an IC-voltage regulator
• Power Supply for Preamplifiers - gives +/-15V outputs and takes power from external AC power supply
• Power supply with +5V, +15V and -15V outputs
• Regulated 12 Supply - provides a regulated 12 volts at 0.5 amp to a load, built from discrete components
• Regulated 12 Volts DC Power Supply for Vacuum Tube Heaters - this 7812 based circuit circuit can be used with low-hum audio applications such as microphone preamps and for other applications that require well regulated 12 volts
• Regulated Power Supplies - many designs, for 6V to 400V, both tube and transistor based designs
• Regulator excels in noise and line rejection - certain electronic circuits require extremely low-noise power supplies and this circuit provides very good quality power output
• Regulator generates sub-bandgap voltages - 100-mA regulator that uses a dual linear-regulator IC to produce output voltages below 1.25V from 2.9 to 5.5V input-voltage range
• Sam's Schematic Collection of various circuits - includes many regulated power supply circuits
• Simple 5V power supply for digital circuits
• The Spyder - an Eight-Output Pedalboard Power Supply - outputs regulated 9V DC
• Ultra Low Drop Linear Regulator - MOSFET based linear voltage regulator with a voltage drop of as low as 60 mV at 1 ampere, output 12V up to 3A, includes short-circuit crow-bar protection to guard the components against over-stress during accidental short at the output
• Universal DC-DC Convertor - This circuit will generate a smaller DC output voltage from a larger DC input voltage.It is quick and simple to make and by changing the value of the zener diode, the circuit can be universally adapted to provide other output voltages. The circuit and all diagrams represent a DC convertor with 12V battery input and 9Volt DC output.
• Voltage Regulator - simple regulated 12V power supply using one transistor regulator circuit

Adjustable

• 0 - 300V Adjustable Power suppy - This is a simple circuit which can provide an adjustable voltage source of 0 to 330 Volt. The supply is short-ciruit proof: the current is limited to about 100mA.
• 1.2-25VDC at 4A power supply schematic - built using discrete transistors and 741 opamp, read circuit description
• 1A Variabe Power Supply - This circuit takes in 240V AC and outputs a regulated DC at voltage sange of 2-15V DC up to 1.5A.
• Adjustable power supply using LM317 - voltage regulator for 1.2V to 35V output voltages and up to 1A load
• Adjustable Power Supply - well filtered variable 1.2-30 volts at 5 amps using LM338K
• Build a Variable Voltage Supply for Cheap - This is a variable voltage 1.5A supply that can be built cheaply and used for bench experimeting. With a 24VDC wall wart, this board can produce anywhere from 23V to 1.2V
• Dual Power Supply - adjustable two output laboratory power supply with meters, circuit designed by Joel T. Retanan , 222k pdf file
• High Current Regulated Supply - uses pair of 3N3055 transistors to give out currents up to 15A
• L200 Regulator Circuit - easy to build a power supply with one single L200 IC, offers a variable current limit of up to 2 A, as well as voltage regulation
• Variable 3 - 24 Volt / 3 Amp Power Supply - regulated power supply can be adjusted from 3 to 25 volts and is current limited
• Self-switching Power Supply - output variable from 3.7V to 8.7V and supply switches itself off when no load is connected across its output terminals
• Simple regulator circuits for regulating DC power - regulators built from zener diodes and transistors
• Säädettävä jännitelähde 0-24V 4A - 0-24V 4A adjustable power supply, text in Finnish
• Säädettävät regulaattorit - adjustable regulators using L200CV, LM317T and LM338K regulators ICs, text in Finnish, but pictures are prettu much self explanatory and text not needed, output voltages in rage 1.2V..36V and current 1A..5A
• Variable Power Supply - based on versatile L200 voltage regulator, independent voltage (3-15V) and current (10mA-2A) limits
• Velleman K1823 Power Supply - This small power supply provides a regulated voltage between 1.5V and 35 volts at 1A that can be used in many applications. This is a full documentation of a kit sold by Velleman .

Dual polarity

• +/-15V power supply suitable for audio circuits - uses LM317 and LM337 regulator ICs
• DC Power Supply - outputs +5V, adjustable +0..15V and adjustable -0..15V
• Dual +/-15 Volt Power Supply - suitable for powering opamp circuits
• Dual Polarity Power Supply - supply is easy to build and adjustable from 0-15 volts
• Dual Polarity Power Supply - well documented +/-15v power supply using LM317 and LM337 regulators, schematics and parts lists are provided. Project description provides a solid understanding of what the circuit does.
• Electronic Regulated Power Supplies - low noise +-62V regulated power supply for audio applications with PSRR up into 80dB
• Op amp makes precise 9V-battery splitter - alkaline 9V batteries are ideal for many portable, handheld applications, this circuit generates a bipolar supply of 5V and ­2.3 to ­4V using a precision 5V reference and one op amp as a supply splitter
• Power Supply for Preamplifiers - low noise regulated +/-15V power supply
• Renkus-Heinz Controller Power Supply - outputs regulated +-15V
• Simple DC Adapter Power Supply - DC voltage "virtual earth" circuits
• Variable Dual Lab Power Supply - can supply from +/-1.2V up to about +/-25V, will current limit at around 800mA
• Voltage Inverter II - simple and inexpensive circuit can produce a dual (positive and negative) voltage from a single supply input, extremely useful for powering opamp and other circuits that require a dual voltage from a single battery

Negative voltage generating circuits

• Generating -5VDC from +5VDC - simple capacitor pump circuit based on 555 chip
• Generating -5 Volts From a 9 Volt Battery
• Voltage inverter - simple low power design based on 555

CD player adaptors

• Portable CD Player Adapter For Car - steps down the 12V from the lighter socket to 9V which is used by some CD players (Sony Discman)
• Walkman 3V Power Supply

Misc

• High-Current, Low-Voltage Shunt Regulator - up to 8 A shunt-regulator built around the TLV431 low-voltage, adjustable, precision shunt-regulator IC
• Take power out of PC RS-232 port
• Power supplies and transformers - basic structures of power supplies