Misc circuits

• +5v from RS-232 using LM78L05
• Advanced polarity protection with MOSFETs - Advanced Power Switching and Polarity Protection for Effects
• A Simple Capacitance Multiplier Power Supply For Class-A Amplifiers - A mentohd which providess good noise filtering but no actual voltage regulation
• Automaatti-sulake - This is an automatic fuse circuit for 24V power. Thsi circuit uses transistors which control an output relay. The text of this document is in Finnish.
• Circuit combines power supply and audio amplifier - This circuit can helpful if you must transfer dc power and audio over a pair of copper wires. The circuit uses only one IC, the well-known LM317, a low-cost power-supply regulator. Using this chip, you can modulate the adjustment-pin input with the audio signal from an electret condenser microphone, connected between the output and the adjustment terminals of the IC.
• Clamping circuit dissipates minimal power - quasi-linear regulator
• Drive high-voltage varactor diodes from just 5V - how to connect two International Rectifier (El Segundo, CA) PVI1050s photovoltaic-isolator ICs in series to provide a 20V tuning drive for the varactor diode
• Electronic Fuse for Power Supply - This circuit offers effective protection against overcurrent in power supply with output voltage through to 45V DC and output current form 0.1A to 5A.
• High-Voltage EL Lamp Driver
• Micropower, 10ppm/°C, +/-5v reference
• MOSFET replaces switch - you can use a single-pole switch to turn a bipolar power supply on and off without consuming extra power
• Power switch provides soft start
• Quickly discharge power-supply capacitors - A perennial challenge in power-supply design is the safe and speedy discharge, or "dump," at turn-off of the large amount of energy stored in the postrectification filter capacitors. If you let the capacitors self-discharge, dangerous voltages can persist on unloaded electrolytic filter capacitors for hours or even days. This design idea gives one alternative approach for faster discharge than normal bleeder resistors provide.
• Rectification using a Gyrator Circuit
• Series Lamp Limiter - connect a 100W lamp bulb in series with the supply to the equipment being repaired to avoid very nadty high short circuit current is something goes seriously wrong, useful for power supply testing and repairing
• Smoke Detector Power Supply - This power supply normally supplied power from AC mains power source thrpgh transformer nad charges a battery. When AC mains power dissapears, the power is supplied from the battery.
• Soft-Start Circuit For Power Amps - This circuit reduces the current spike large transformers take when switched on.
• Soft Power On Tester for Amplifiers - The worst thing that can happen is that when you turn an electronics device you are fixing on, it immediately pops a fuse - or worse yet a valuable part you've just installed! If you don't have a variac with a current meter so that you can make power on gradual, the next best thing is this widget. It can be whipped up from parts in your local home supplies store.
• Time-delay relay reduces inrush current - A transformer switching onto a line can sometimes cause a circuit breaker to trip or a fuse to blow. This phenomenon occurs even if the transformer presents no load, such as when the secondary is open. The problem arises because of the heavy magnetizing inrush current in the transformer. This design solves the problem in one way.
• Transistors offer thermal protection for controller - You can use standard bipolar transistors to implement a low-cost thermal-shutdown circuit for switched mode power supply.
• Transistor latch improves on/off circuitry
• Versatile power-supply load uses light bulbs - Improvising loads for bench-testing and designing power supplies is often a frustrating and sometimes hazardous experience. Many electronic loads are on the market but are usually expensive and of laboratory-type precision and often represent overkill for the average designer. Incandescent light bulbs make excellent loads, able to handle large amounts of power. Moreover, they come in small packages and require no heat sinks. The drawback is that the resistance of an incandescent lamp changes dramatically with the power input. A simple approach to this control problem is to pulse-width-modulate a power MOSFET in series with the load.
• Voltage follower with 1G ohm input resistance

Transformerless power supplies

Transformerless power supplies are very useful in some applications, but remeber that eliminating the transformer eliminates the safety factor. You should this type of power supply only if the circuit you want to power has no external connections to anything else (unless they are properly isolated from the rest of the circuit). Line isolation is essential for safety with respect to electrical shock - no part accessible to the user must be connected to either side of the power line. A regular transformer provides this automatically.

• Off-line power supply requires few parts - This simple non-isolated off-line power supply can provide up to 150 mA 5V and uses only a handful of components from 110-230V AC input voltage. Note that the low voltage output is directly connected to the mains; it can not be used when the low voltage part can be touched.
• Transformerless mains power supply - This power supply does not really excel in power efficiency, but it is the cheapest and most compact solution for a small power supply. Note that the low voltage output is directly connected to the mains; it can not be used when the low voltage part can be touched. With the component values of the schematic, the circuit can supply 12V /15mA max.
• Transformerless supply fits CATV applications - coaxial CATV systems derive their power from a 60-Hz square wave that shares the center conductor with the television channelsm this circuit generates 10 mA at 5V DC from it

Tesla Coil

Tesla coil is high voltage technology discovered by Nikola Tesla over 100 years ago. A Tesla coil is a high-voltage air-core resonant transformer. The Tesla coil achieves a great gain in voltage in a very different way than a conventional transformer. Tesla coil's voltage gain is based upon the different impedances of the primary and secondary circuit components.
Tesla coils are extremely dangerous. The entire circuit of a Tesla coil contains deadly levels of voltage and current. A Tesla coil can radiate high voltage sparks many feet out into the air that will strike anything including you. Extreme caution must be exercised whenever operating a Tesla coil. Tesla coils can generate huge amounts of radio frequency interference (should preferably operated only inside a shielded room). Tesla coil operation involves high energy electrical discharge, high voltages, and often high speed rotary gaps. For the beginner, there are plenty of ways to injure or kill yourself. Safety is an important part of fun, successful tesla coiling.

• 500,000 Volt Tesla Coil - 18" sparks
• Cheap and Quick Tesla Coil - uses neon transformer and spark gap
• Homepage of K.Ukkonen - lost of Tesla Coil links
• Jochen's High Voltage Page
• Make myself a Tesla Coil
• Matt Behrend's Tesla Coil Web Site - This site is devoted entirely to the high voltage technology discovered by Nikola Tesla over 100 years ago. This site was created for the purpose of providing useful information to anyone who is interested in actually building a Tesla coil, or just curious about the technology.
• Nikola Tesla Page, tesla coils
• Solid State Tesla Coil/High Voltage Generator
• Tesla Coil Calculations - coils and capcitors
• Tesla Coil Mailing List Page - The tesla coil mailing list covers the topics of tesla coil construction, operation, measurement, and use. Topics range from sources of materials, opinions of commercial tesla coil kits, measurement of electical fields, photography of coils, construction techniques, etc.
• Tesla Coil Page
• Tesla coil pictures
• Tesla Coil Safety Information - This document is provided to assist the amateur in understanding the significant dangers associated with tesla coils.
• The Electrum Project - some technical information about a very large tesla coil project
• TUBE-type Oscillator-Driven Tesla Coil

High voltage experimenting

• Capacitor Discharge Ignition Circuit (CDI)
• Circuit to Get High Voltage from an Ignition Coil
• High Frequency Plasma Circuit - circuit utilzes a flyback transformer that has wire windings added to its ferrite core to make high frequency high voltage, transformer is driven into resonance at 20 to 170Khz
• High Voltage Experimenter's Handbook
• Ignition Coil \ Flyback Transformer Based high voltage generators - Flyback transformer driver circuit with protection/advanced features
• Jochen's High Voltage Page - lots of high voltage circuits and experiments
• Measuring high voltages - simplest way to get at least a rough value of tension is to measure the maximum distance the voltage can arc over
• Pulse Generator Schematic - Can be used to evaluate high voltage pulse characteristics of zeners and MOV'
• Sam Barros' Powerlabs - tesla coils, high voltage experiments, microwave, chemistry, cryogenics
• Science & Technology of high voltage generators - A page on high voltage multipliers, a circuit on driving flybacks (with a large capacitor as protection) and power supplies
• Snock's High Voltage Page - detailed explanation on flyback, ignition coil circuits and pictures of various transformers
• Solid State Tesla Coil/High Voltage Generator

Stun gun circuits

• 1800 Volt Stun Gun

Special application power supplies

• HeNe laser power supply
• Tiny tiny invertor design - run off of 3V, and charges up a little 1 uf 250V cap all the way up in about 30 seconds

Power supply monitoring and protection circuits

• 220V Mains Monitor - With this circuit you will be able to monitor the quality of the mains. There are 4 distinct sections, each supervising a parameter pertinent to the quality of the supply line. There are sections for noise, spikes, voltage and flutter.
• Circuit breaker monitors leakage current - This residual-current circuit breaker continuously monitors the supply lines for any leakage current and immediately disconnects the supply if necessary.
• Circuit breaker has programmable delay - this circuit provides overload and short-circuit protection to a 5V power-supply output
• Circuit protects against ac-line disturbances - operates by switching off the power supply upon detection of undervoltage or overvoltage conditions
• Circuit safely applies power to ICs - Supervisory circuits normally monitor a microprocessor's supply voltage, asserting reset to the IC during power-up, power-down, and brownout. In this way, the circuit ensures that the supply voltage is stable before the microprocessor boots, thus preventing code-execution errors. This circuit works so that is connect power to sensitive ICs only when they are at safe level.
• Circuit senses high-side current - The accurate, high-side, current-sense circuit does not use a dedicated, isolated supply voltage, as some other schemes do.
• Comparator detects failed telecomm supplies - detects when telecomm power supply's 48V output drops below its nominal value, uses an isolated comparator to monitor two 48V telecomm supplies (of either polarity)
• Current limiter provides latch-up signal - current-limiting circuit both signals a latch-up condition and prevents latch-up-induced overcurrent destruction of a CMOS IC or group of ICs
• Current limit protects power bus - protects a power bus from a load short within a guaranteed 2 µsec response time
• Detect Fan Failure With A Single Transistor
• Double-ended flashing voltage monitor using LM10 - can detect an over and under-voltage condition and flash LED
• Electronic fuse emulates fast- or slow-blow fuses - The electronic-fuse circuit in this article combines the properties of a current transducer and a solid-state relay to disconnect low power at preset levels. Using this circuit lets you avoid the bother of stocking and replacing fusible links.
• Fuse Monitor / Alarm - a simple way to see if a fuse has blown without removing it from its holder
• High-current trip - electronic fuse circuit will quickly break the circuit when the current exceeds about 50A
• Mains power failure alert
• Microamps monitor dual-supply batteries - low-power circuit monitors two 9V batteries in a dual-supply configuration and turns on the Battery Low LED if either battery voltage drops below its limit
• Monitor high-side current without an external supply
• Optocoupler extends high-side current sensor to 1 kV
• Overload and reverse-current circuitry protects battery and load - there are numerous circuits can protect against backward installation of batteries and other overcurrent-causing conditions
• Over Voltage Protection - describes crowbar technique that provides a useful defence for fast over voltage spikes and transients that could cause damage to more sensitive components
• Power-Supply Failure Alarm - alarms with beep when mains power feed fails
• Protection for your Electrical Appliances - very low-cost circuit to save your electrically operated appliances from the effects of sudden tripping and resumption of mains supply, this circuit switches off the mains supply to the load as soon as the power trips
• Simple Current-Limiter And Power Switch Offer Overcurrent Protection
• Single LED indicates two power states - uses a single bicolor LED to indicate both power-on and blown-fuse conditions
• The fuse monitor - a neon glow lamp indicates by remaining lit that the fuse is in order, by blinking that the fuse has blown and by remaining off that there is no power
• The main voltage monitor - main voltage monitor that is simply a lamp that glows when the main voltage is present, designed for 230V AC, can be adapted to 110V AC operation
• Two-lead solid-state breaker resets itself - simple dc circuit breaker can protect a power supply from the ever-present screwdriver or even isolate a satellite's dual power system from a short circuit in one subsystem

DC to AC converter and UPS circuits

Have you ever wanted to run a TV, stereo or other appliance while on the road or camping? Well, a power inverter should solve that problem. An inverter is an electrical device that converts 12-volt power into mains power (120V 60Hz AC or 230V 50 Hz AC typically). Typically you run an inverter off of your car's battery or off of a deep-cycle battery that you buy specifically to power the inverter. An inverter is usually a very easy and inexpensive solution to get mains power where it is not normally available if you can keep your power demands in the 200-watt range.
With around 300 watts of continuous power inverter you can run items like desktop computers, monitors, full size fax machines, battery chargers and AC adapters for notebook computers, cellular phones, camcorders, small power tools, drills, mid-sized TVs, soldering guns, and a variety of rechargeable equipment on the road. If you have a higher power inverter, you can run more devices or more powerful devices. With a lower power converter you can use only devices which use less power. Power inverters are also very useful in solar power system which generally use low voltage batteries (usually 12V DC) to be able to run mains powered devices in them.
The three most common outputs for inverters are square wave, modified sinewave (sometimes called a quasi sinewave), and sinewave outputs. Most devices with variable speeds such as electric drills, or devices with chargers such as cordless drills or screwdrivers, can behave irrationally when operating with modified sine or square wave inverters. Small wall based chargers (called wall warts) can have overheating problems with modified sine or square wave inputs. Some computers and stereo equipment use switching power supplies that utilize SCR's and Triacs as well. These pieces of equipment may experience the same troubles with non-sinewave power. True sine wave output allows connected loads and equipment to operate the same as they would from utility supplied power. Unfortunately the true sine wave output inverters are more expensive than the ones which use square wave or modified sinewave.
Generally you can buy a small 150- or 300-watt quasi-sine-wave inverter for about $50. Higher power or true sinewave models cost generally more.
An Uninterruptible Power Supply (UPS) is a device that sits between a power supply (e.g. a wall outlet) and a device (e.g. a computer) to prevent undesired features of the power source (outages, sags, surges, bad harmonics, etc.) from the supply from adversely affecting the performance of the device. UPS devices generally consist of some form of internal battery, inverter and intelligent switching electronics. When normal mains power is available, it is supplied to the devices connected to UPS. When mains power is not available, the devices connected to UPS output are powered by the inverter circuit inside the UPS. UPS devices aren't designed to let you keep working for a long period of time after power outage; they're designed to give you enough time to shut your system down in the normal manner.
NOTE: Most of the circuits below have square wave output and are not suitable for driving sensitive electronics equipments. The AC from those inverters can damage some equipments connected to them.

General articles

• A Simple Tool for Interactive Design of Inverters - this paper presents a simple method to predict the losses in the power semiconductors of an inverter where the output sinewave is obtained by pulse-width modulation of a high frequency carrier
• How Emergency Power Systems Work - A wide variety of natural disasters can cause long-term power outages. An UPS or battery and inverter can provide emergency power for some time, but there are also other alternatives for this.
• Modified Sinewave and Sinewave Waveforms - three most common outputs for inverters are square wave, modified sinewave and sinewave outputs, this paper will look at these waveforms, and how different types of loads behave when operating from them
• Power Converter Survives High-Energy, Low-Frequency Surges - article on UPS design

Circuits

• 24 Volt DC to 110 Volt AC Power Inverter - Converts the power from two 12 volt batteries to AC to power a drill or whatever
• 5W Inverter - A single transistor is all you need for this simple inverter. The main aim of this circuit is to provide a suitable supply for all kind of low power battery chargers that normally connect to the mains such as mobile phones, electric shavers, etc, even an electronic neon light rated at 5W.
• Basic 200 W power inverter - 12V DC to 110V 60 Hz AC, up to 200W continunous, square wave output
• Building a dc to ac converter - Otherwise known as a dual axis drive corrector, this unit is intended to provide 240 volts/50 Hz (or 120 volts/60 Hz with minor modifications) for a right ascension (ra) drive and a reversible declination motor. The supply requirement is from 11 to 16 volts d.c. at 500 mA. The overall output frequency is adjustable from 47.5 Hz to 52.5 Hz or from 40 Hz to 60 Hz on the remote unit. This frequency is stabilised against voltage or temperature change.
• DC/AC inverter - 12V DC to 110V AC
• DC to AC power inverter - convert 12V DC to 120V AC, based on SCRs and FETs
• Inverter - takes 12 VDC and steps it up to 120 VAC
• Inverter offers design flexibility - works from a 12V car battery and produces mains voltage with closed-loop voltage regulation
• SCR Inverter - outputs 300V 400Hz, waveform is vaguely sinusoidal, 5W output power
• The I2K Power Inverter - This circuit is a 2kVA 12VDC to 120VAC inverter for power backup. This description of the inverter is preliminary and incomplete.

UPS techology

• Uninterruptible Power Supply (UPS) FAQ - This is a FAQ document on Uninterruptible Power Supplies. It is intended to provide a starting point for those people that want to find out what they are, what they do, and what's available. Most of this document is very US-centric. The power numbers, companies and services all emphasize US consumer needs.
• Uninterruptable Power Supply Reference Design - Application note from Microchip
• Uninterruptible Power Supply Types - Most people know that UPSes exist, but many seem to think that there is just one kind of device that goes by that name. In fact, there are several different major designs in use for UPS models. Those who sell these devices share much of the blame for this situation, because too often, the different kinds of UPS are all called the same, generic name.
• UPS Semiconductor Technologies

Computer power supplies

Computer power supplies

The power supply converts the alternating current (AC) line from your home to the direct current (DC) needed by the personal computer. In a personal computer (PC), the power supply is the metal box usually found in a corner of the case. The power supply is visible from the back of many systems because it contains the power-cord receptacle and the cooling fan.

General information

• ATX /ATX12V Power Supply Design Guide
• Atx-virtalähteen liitin - This document describes ATX power connector pinout and wire colors. The text of this document is in Finnish, but most of the information is usable even if you do not understand that language.
• How PC Power Supplies Work - This article tells basics how PC power supplies work.
• Pentium II power supplies: too young to smoke - Most dc/dc power supplies for high-speed µPs don't meet the CPU manufacturer's specs, and some fail at a tender age. If you recognize the problems and understand dc/dc-converter design, your supply can live long—and you can prosper.
• Power Supply Wattage - This article has table of some power consumption values (in watts) for common items in a personal computer.
• Recycling Obsolete Computer Power Supplies: Computer Power Supplies Contain Useful Parts - There are many parts in old computer power supplies that are useful in electronics projects.

Project pages for car PC power supplies

• 38W Computer PSU for 12V input voltage
• DC-DC Power Supply from car 12V to PC motherboard
• Homemade CAR MP3 Player - includes desing for PC power supply which works in car
• Mobile MP3 player power supply - information on powering small industrial PC motherboard from car +12V power
• Power Supply for car PC based MP3 player
• Schematics for 12v PC Power Supply

Power connector pinouts

• 3.5" floppy disk drive power connector
• 5.25" floppy/hard disk power connector - used for harddisks & 5.25" peripherals
• ATX Motherboard Power
• Background on the ATX power supply
• Motherboard Power Connector - AT power supply pinout
• PC power supply connectors - AT power supply connector pinout and information
• Power Good Signal - how AT power supply "power good"-signal works

Battery information and circuits

Normal batteries have generally 1.5V per cell voltage (except some Lithium cells which have 3V voltage). The batteries which have higher voltage output are built genrally from many 1.5V cells in series all put inside same "case". Rechargeable batteries have generally somewhat different lower voltages and capacity than their their "only once usable" counterparts. Normal alkalines are 1.5V each, but Ni-Cd batts are only 1.2V each. If you use four of them for instance, you only get 4.8V instead of 6V. You can make up for it by adding a cell for each four cells, so five cells will give you 6V. That's probably why some equipment instructions don't allow them. Another reason could be that NiCd batteries have enormous short-circuit current capability (easily tens of ampreres or more) compared to many traditional batteries (causes greater risk of fire in case of short circuit). NiCd batteries are easy to charge at slow charge mode. Just apply a charging current, typically around 50 mA for 500mah cells, for 12-14 hours to change them. It does not hurt the batteries if you charge the batteries at the current with somewhat longer times (even few times longer) than needed. When batteries are are charged after they are full, the applied power is converted to heat, so NiCd batteries should start to become warm then. Some will say sinking C/10 (50mA for 500 mAh battery) indefinately into NiCd is acceptable but this is not a recommended practice. NiCd batteries can also be charged faster with special "smart chargers" which use controlled higher current to the batteries until they are charged and stop this current when batteries are full (the charger has special sense circuitry for this). Exercise extreme precaution when handling and testing NiCd batteries. NiCd batteries include some amount of cadmium (Cd), which is dangerous material for enviroment. Do not throw NiCd batteries away with your trash. You should bring those batteries to recycling. When discharging NiCd battery packs be cautious about over-discharge. Individual NiCd cells can go to zero volts but in a battery pack letting them drop below 1V each may reverse and ruin a weak cell since they are in series. In some applications NiCd batteries are replaced with higher capacity NiMH batteries. Those batteries have pretty much similar characteristics to NiCd (except that they need somewhat different charger). NiCad and NiMh cell voltages are identical. There is some difference at end of charge and used by sophisticated chargers. NiMh are sensitive to overcharge. NiMh should be preferably be always charged with "smart chargers" designed to charge NiMh batteries. NiMh batteries can also be charged with constant current C/10 (50mA for 500 mAH cell) current, but you should avoid excessive overcharge because this will shorten battery life. Compared to Nicad NiMh are nearly twice the capacity, can be recharged from any level, selfdischarge more tha twice as fast, have about half the full cycle number life, and are not as robust when charging. Many new small gadgets like cellular phones use Li-ion batteries. Li-ion batteries have a high energy density. Exercise extreme precaution when handling and testing Li-ion batteries. Do not short circuit, overcharge, crush, drop, mutilate, penetrate, apply reverse polarity, expose to high temperature or disassemble them. Only use the Li-ion battery with the designated protection circuit (cellular phone batteries usually have this). Abuse of Li-ion can cause "explosion" like happening, because in short circuit the case temperature can get very high and the electrolyte inside Li-ion battery is highly flammable. Car batteries are built are lead acid cells. They have a cell voltage of around 2 volts (means 6 cells in series makes 12V battery). Normal 12V car battery is designed to be quite robust. It can be carged with almost any reasonably current limited constant voltage source of around the nominal voltage of the battery (for example 13.5V for 12V car battery). Car batteries are built for heavy currents but DO NOT deep discharge them, only shallow discharge. If you repeatedly run a car battery down to much below 50% of capacity you will seriously shorten its life. Warnings on car batteries: Car batteries contain dangerous acid hare heavy, so handle carefully. Charging car batteries can generate highly flammabble hydrogen, so it is best to charge those only in well ventilated spaces. Car batteries have very large short circuit current (hundreds of amperes), so do not short circuit them (a fuse near battery terminal is essential for safety to avoid wire fires in short circuit happens). There are also other types of lead acid cells than car batteries. Some are designed for deep discharge use and some for some other applications. Generally lead acid batteries don't like to be discharged below 1.67 volts per cell (10V for a 12V battery) and their full capacity can only be extracted if the load current is something like C/10 or C/20 (where C is the barrery capcity in Ah and resulting current is in A). Short list of most common battery characteristics:
• Lead Acid: most economical for larger power applications where weight is of little concern (cars, boats, wheelchairs, emergency lighting, UPS systems), low energy density (30-50 Wh/kg), available in low cost versions, cell voltage 2V, voltage limiting rather than current limiting is used for charging
• Sealed lead acid (SLA,Gelcell): maintenance-free lead acid battery with electrolyte in moistened separators, enclosure is sealed, used for wheeled mobility, typical charge times are 8 to 16 hours, must always be stored in a charged state, 200 to 300 discharge/charge cycles
• Nickel Cadmium (NiCd): mature and well understood technoogy used in chargeable batteries used in many applications (power tools, two-way radios, video cameras), standard against which other batteries are usually compared, not very good energy density (45-80 Wh/kg), cell voltage 1.25V, life cycle 1000-1500 charges
• Nickel-Metal Hydride (NiMH): higher energy density (60-120Wh/kg) compared to the NiCd at the expense of reduced cycle life, no toxic metals, used in mobile phones and laptop computers, cell voltage 1.25V, life cycle 300-500 charges
• Lithium Ion (Li-ion): fastest growing battery system, high-energy density (110-160 Wh/kg) and lightweight, technology is fragile and a protection circuit is required to assure safety, applications in notebook computers and cellular phones, cell voltage 3.6V, life cycle 500-1000 charges
• Lithium Polymer (Li-polymer): uses a dry solid polymer electrolyte, cell thickness measuring as little as one millimeter, suffers from poor conductivity (high internal resistance)
• Lithium Ion Polymer (Li-ion polymer): uses a combination of dry polymer electrolyte combined with some gelled electrolyte, ultra-slim geometry, high energy density (100-130 Wh/kg), used in mobile phones, cell voltage 3.6V, life cycle 300-500 charges, promotional reasons most battery manufacturers mark this kind of battery simply as Li-polymer
• Reuasable Alkaline: Special alkalinen battry which can be charged few times (energy density 80 Wh/kg), cell voltage 1.5V, life cyle around 50 cyled of 50% charge/recharge

General battery information

• 10 things to know about batteries - mostly about video camera batteries
• Battery Backup Applications Handbook
• Car Battery and Deep Cycle Battery FAQ - This web site contains the free consumer information about car and deep cycle storage batteries.
• Proper handling helps make the most of Li-ion batteries - Li-ion batteries pack the most power per unit volume, but excessive charging or discharging can damage or destroy the battery and its surroundings, carefully designed circuits help you avoid such dire outcomes
• Sizing Up The Benefits Of Integrated Battery Electronics
• Smart-battery technology: power management's missing link - you no longer need to view a battery as a power-generating element whose characteristics are beyond your knowledge and controla
• PSpice models nickel-metal-hydride cells - nickel-metal-hydride (NiMH) battery model accurately predicts the discharge characteristics of an NiMH cell (or groups of cells)
• Testing batteries: The more things change, the more they stay the same - Despite new chemistries, improved manufacturing methods, "smart"-battery technologies, and a host of Information Age uses, batteries for consumer applications continue to rely heavily on functional testing for characterization and evaluation.
• The Video Battery Handbook - guide to the care and feeding of video batteries
• Varta Battery Know-how
• What is the perfect battery? - We often get puzzled by announcements of new batteries that are said to offer very high energy densities, deliver 1000 charge/discharge cycle and are paper-thin. Are they real? Perhaps - but not in one and the same battery.

General charging circuits

• 6 volt lead acid battery chargerkit - lead acid charger that uses the uc3906 chip
• Charger delivers 2.5A with 96% efficiency
• Constant Current Battery Charger
• GellCell Battery Charger - circuit to charge a GellCell or other lead-acid type battery, includes sense circuit
• Optimizing high-frequency battery-charger performance for worldwide applications - providing power for electric vehicles for worldwide use requires knowledge of energy-conserving and high-efficiency technologies
• Remote charging circuit uses three-wire sensing - remote voltage sensing usually uses a four-wire sensing system, this system works with three wires
• Sealed Lead-Acid Battery Charger Circuit - A very effective and simple sealed lead acid battery charger
• Shunt battery charger provides 1A continuous current - a shunt method is preferable than series regulation in solar-powered systems
• Solar Panel Charge Controller / Low Voltage Disconnect Circuit - Lead acid charger, with battery voltage monitor, power comes from solar panels
• Solar charger for lead-acid batteries - Solar lead acid charger, with battery voltage monitor, for 12V battery
• Step-up/step-down current source charges batteries
• Trickle Charger - Explains what trickle charging is, contains some basic trickle charging circuits.
• VK3EM Sealed Lead Acid Battery Charger MK II - A high-tech lead acid charger, uses the uc3906 chip

Battery chargers for NiCd batteries

• Battery charger indicates rate of charge - a single LED indicates whether the battery charger s delivering a trickle charge or a fast charge, cricuit designed to charge 2-14 cells
• Constant Current Nicad Charger - The schematic for this charger is pretty simple. You can charge from 1 to 20 +/- nicads at a constant current of from 20 to 200 ma +/-.
• Make Your Own Simple Rx/Tx Battery Charger with Peak Detect - This circuit is designed to peak charge Rx and Tx batteries. It's programmed for a C/2 charge rate for 250mAh and 500mAh batteries (charge currents of 125mA or 250mA). It'll charge Rx from 12V at the field, Tx from a 15V supply (like a car w/engine running). Use a 15-18V supply to charge at home (you should be able to find wall cubes with this rating). It is based on a Maxim IC, the MAX713.
• Ni-Cd Batteries Charger - A very basic circuit that takes approximately 12-15 hours of charge AA-batteries at 50mA charging current.
• Nicad Battery Charger - uses a single transistor as a constant current source
• NiCd or NiMh battery charger - This charger can be used for AAA, AA and Baby C batteries. This battery charger is based on MAX712/MAX713.

Li-ion battery chargers

• Charge Li-ion batteries from ac line voltage - converts energy from 120V ac to a regulated voltage or current as necessary to charge two Li-ion cells in series
• Supply derives 5 and 3.3V from USB port - This circuit derives its power from a USB port and produces 5 and 3.3V supply rails for portable devices, such as digital cameras, MP3 players, and PDAs. The circuit allows the port to maintain communications while, for example, charging a lithium-ion battery. IC2 boosts the battery voltage, VBATT, to 5V, and IC3 buck-regulates that 5V output down to 3.3V.

Lead-acid battery cargers

• Charge Monitor for 12V Rechargeable Lead-acid Battery
• Dual rate battery charger - charges 2-10 amp-hour lead-acid 12V battery packs in about 6 hours
• Lead-acid charger signals end of charge - lead-acid battery charger that works with either gel- or wet-cell, lead-acid, 12V batteries
• Sealed Lead-Acid Battery Charger Circuit
• Sealed Lead Acid Battery Charger Design Documentation - based on the UniTrode UC3906 Integrated Circuit
• VK3EM Sealed Lead Acid Battery Charger Mk II

Combined power supplies and batery chargers

• Buck-converter charger also provides system power - switching regulator provides the charge-voltage setpoint with current regulation, and second switching regulator provides 5V system power

Battery discharging circuits

• Battery Discharge Monitor - pdf file
• Simple circuit safely deep-discharges NiCd battery

Battery backup circuits

• Battery-backup converter uses one NiCd cell - this dc/dc converter allows you to replace a five- or six-unit string of NiCd coin cells with one cell

Battery protection

• Battery-protection circuit allows surges - circuit monitors two lithium-ion batteries and protects both of them against overcharging, overdischarging, and undervoltage
• Circuit prevents deep discharge of batteries - to avoid the deep discharge that can destroy or shorten the life of a rechargeable battery, you must disconnect its load before the discharge is complete
• Circuit protects battery from overdischarge - In some applications, it is undesirable to overdischarge the battery, because it could irreversibly reduce the battery's capacity and the number of discharge/charge cycles. This circuit protects a single NiMH (nickel-metal-hydride) cell by disconnecting the load from the battery when it getting discharged enough.
• Overload and reverse-current circuitry protects battery and load - there are numerous circuits can protect against backward installation of batteries and other overcurrent-causing conditions

Battery status sensors

• Digital/Analog Hybrid Circuit Calculates Battery Life
• LED flasher indicates low-battery condition
• Phantom power battery test circuit - LED will light when battery is over 42 volts
• Simple circuit monitors battery voltage - monitors four NiCd rechargeable batteries and causes the LED to flash if the voltage of the batteries goes lower than 4V
• Test batteries without a voltmeter - This circuit an easy approach to testing batteries without exiting the voltmeter. The battery holders in sizes AAA, AA, C, and D make this tester so much faster than a voltmeter.

Normal battery chargers

Bascially all types of alkaline cells can be recharged, although the battery manufacturers discourage this (dangers of overcharging and battery leaking). You will need a special charger for charging alkaline cells (normal NiCd chagers are not suitable for this). There are some special alkaline cells nowadays which chan be charged better than normal alkaline cells. The best practice is not to discharge completely the cell or battery but rather to give a short charge often. Do not attempt to recharge a totally discharged cell or a cell showing even the slightest sign of damage.
• Alkaline Charger - This circuit was specifically designed to recharge alkaline cells. It will take around 1 day for a discharged AA cell or 9V battery and up to several days for a large D type cell to carge.

Other battery circuits

• Battery desulfator for lead-acid batteries - based on ome Power magazine article

Switchers

A switching power supply is a device transforming the voltage from one level to another. Typically it is taken from the mains and transformed to the DC levels that logic requires in a PC or a battery loader. The main differences between the linear and switched-mode regulator are in the size, weight and efficiency.
Since a switched-mode converter can operate at significantly high frequencies, then a smaller transformer using ferrite cores can be used. Also since the high rectified mains voltage is chopped, then energy storage for hold-up can be accomplished on the primary side of the step-down transformer and so much smaller capacitors than the linear counterpart can be used. A switching-mode power supply (SMPS) is a power supply that provides the power supply function through low loss components such as capacitors, inductors, and transformers -- and the use of switches that are in one of two states, on or off. The advantage is that the switch dissipates very little power in either of these two states and power conversion can be accomplished with minimal power loss, which equates to high efficiency. Usually a switching-mode power supply is circuit that operates in a closed loop system to regulate the power supply output. Although the benefits of switched-mode techniques are great, there is a penalty paid in the increased noise present at both input and output of the supply due to the power switching techniques. Also the associated control circuitry is much more complicated than its linear counterpart.
The switching mode power supply contains a transformer/coil and to make this as small as possible, the internal switching frequency has to be quite high, something typically in the range between 20KHz and 1MHz. This also makes the device noiseless to human ears. The oscillator noise is often conducted onto the input and output lines with a frequency that varies with the load.
There are many different types of withing power supplies. Off Line Switching Mode Power supply is a power supply in which the ac line voltage is rectified and filtered without using a line frequency isolation transformer. After rectifications and filtering the voltage is converted to the needed voltage using a swithing regulator circuit, which usually provides also isolation function (power goes though high frequency transformer). The typical PC power supplies (AT and ATX power supplies for example) are built in this way.
For DC/DC type conversion there are many alternatives. One option is to use switched capacitor converter (usullay used for voltage doubling or negative voltage generation). Switched capacitor type converters are generally used only for low power applications. More often used technique for low and high power is switched inductor converter. This converter type can be used for converting voltage up, voltage regulation and for current regulation.
Designers often categorize power converters into two basic types: isolated and nonisolated. These categories refer to the relationship between the input power ground and the output power ground. Many applications require isolation between the two grounds. The isolation requirement often stems from various safety agencies, and the main purpose of isolation is to protect personnel from exposure to dangerous voltage levels. In some cases, the grounds must have sufficient isolation so that applying a potential of 1500V or more between them shows no indication of breakdown. An isolated power-converter design imposes several extra design challenges on a power-supply designer.
Switchers are suitable for many applications, but not to all. Unless you're willing to spend a great deal of blood, sweat, and tears on the job, it's a bad idea to try to use a switching power supply to power a sensitive analog circuit. Switch-mode power supplies tend to generate impressive amounts of noise - conducted through the power supply rails, radiated, induced, etc. - and this noise can quite easily cross-couple onto your analog signal lines. For some analogue applications switchers are suitable, but then you need to use a very "quiet" switcher type.

Articles

• 1V, 100A supplies: Plugging efficiency leaks - ICs that consume 1V, 100A are just around the corner. Manufacturers of regulator ICs and power semiconductors are busy designing circuits and devices that fulfill that lofty requirement.
• All About Switching Power Supplies - two practical design examples, pdf file
• A New Continuous-Time Model for Current-Mode Control - conference paper in pdf format
• A simple guide to selecting power MOSFETs - As power-supply size and performance demands increase, selecting the right switching devices becomes more complex. A straightforward method simplifies the selection process, speeds your development, and helps you to optimize your design.
• Ceramic capacitors in dc/dc-input filters: OK, but watch out for those transients - Designers now have new reasons to use ceramic, rather than tantalum, capacitors. But be careful.
• Circuit trade-offs minimize noise in battery-input power supplies
• Comparator improves regulator's efficiency - UC384X family of current-mode PWM regulators requires a current shunt or some other component to develop a voltage proportional to the output current, in this example an extra amplifier reduces necessary voltage drop need so reduces losses
• Consider IGBTs over power MOSFETs at frequencies to 100 kHz - evaluating the performance of IGBTs and high-voltage power MOSFETs for switching applications requires a common set of applications and assumptions
• Crossing the boundary: strategies for feedback across an isolation barrier - Designers often categorize power converters into two basic types: isolated and nonisolated. These categories refer to the relationship between the input power ground and the output power ground. Many applications require isolation between the two grounds. Various isolated design approaches have their options, difficulties, and trade-offs.
• Current Doubler Topology: Myth and Reality
• Design Tips - information on transformer measuring and design and also general power supply design
• Effective MOS Transistors Drive Circuits For Bridge Converters
• Feedback isolation augments power-supply safety and performance - properly designed isolated feedback is crucial to maintaining safety on many power supply designs
• Finding the keys to flyback power supplies produces efficient design - quick tutorial on flyback-power-supply design may help clear out some of the cobwebs
• Friendly software eases power-supply design - free software from power-products vendors saves you time and effort when you are configuring and characterizing swoiched mode power-supply designs
• History of Switched Mode Power Supplies - The document describes various switched mode power supply techniques pre 1987. This document is a good introduction to various switched mode power supply techniques.
• IC and capacitor improve isolated supply - many isolated power supplies typically use an optocoupler and a reference to provide feedback to a controller to maintain a constant output voltage, this uses different method to provide controlled output voltage
• Isolated Feedback Techniques for Power Supplies
• Isolated power conversion: making the case for secondary-side control - Two designs with the PWM control on the secondary side highlight the benefits of secondary-side control and point the way toward more optimum architectures for future converter designs.
• Leakage Inductance: Living With Leakage Elements in Flyback Converters - review of the magnetic and electric models of the two-winding and three-winding transformers
• LIER circuit helps power-supply efficiency - leakage-inductance, energy-recovery (LIER) circuit ecovers energy stored in the primary leakage inductance and delivers the recovered energy to one of the power supply's outputs
• Little ICs generate big voltages - ICs and small modules simplify the task of generating the high voltages for displays and their associated backlights
• Low-voltage power sources keep pace with plummeting logic and µP voltages
• Method provides self-timing for synchronous rectifiers - Synchronous rectifiers are MOSFETs, driven in such a way as to perform a rectifying function. They often take the place of diodes in the output-rectification stage of switching power converters, because of their lower on-state power loss. In power circuits, synchronous rectifiers are often complicated to use because of timing issues. This document gives some solutions to solve this problem.
• Modify your switching-supply architecture for improved transient response - by taking a different approach to switching-supply design, you can develop an architecture that improves overall supply performance in critical transient specifications
• Power Converter Survives High-Energy, Low-Frequency Surges - high-energy, low-frequency surge transients can damage electronic circuits, unless the circuit configuration is equiped to handle this type of transient
• Powering New-Generation Microprocessors - there is pressure to abandon inefficient linear regulators on PC motherboards with switching power supplies
• Saturable bead improves reverse recovery - this circuit uses a saturable inductor bead to control the switching diode's reverse-recovery time and, therefore, to reduce EMI in swtiching power supply
• Simplified calculation of magnetic and electrical losses in unity power factor boost regulators
• Smart Solid-State Fuse Helps Designers Cure Boost-Converter Ailments - The challenge is to get desired load disconnect while retaining use of the humble catch diode and unadorned boost topology
• SMPS switch mode power supplies design - oftware tools and design examples
• Spice predicts differential conducted EMI from switching power supplies - not only can predict the exact EMI levels produced by a switched-mode power supply, but also can produce plots that allow you to easily evaluate your design and the effectiveness of the EMI filter
• Spreadsheet simplifies switch-mode power-supply flyback-transformer design - designing flyback transformers for switch-mode power supplies involves many calculations, this spreadsheet helps it
• Synchronous rectification aids low-voltage power supplies - synchronous rectifiers can improve switching-power-supply efficiency, particularly in low-voltage, low-power applications
• Switching converter uses planar magnetics - planar-magnetics technology is growing in popularity as a design option for dc-dc converters
• Switching-Mode Power Supply Design - A good power electronics circuit design hypertext with problem silving tips
• Switching-regulator design lowers noise to 100 µV - extending unconscionable amounts of bypass capacitors, ferrite beads, shields, Mumetal, and aspirin to ameliorate noise-induced effects is no longer the only way to tackle switching-regulator noise, there are nowadays low-noise ICs available
• Switching regulators demystified - Key to good design of switching-regulator circuits is a solid understanding of the fundamental theory of operation.
• Switching-regulator supply provides low-noise biasing for varactor diodes - Low-voltage systems often need a locally generated high voltage. Even for an application as noise-sensitive as varactor-diode biasing, a carefully planned switching-regulator-based design and layout can provide the necessary bias voltage.
• Tandem hookups enhance utility of dc/dc units - flexibility you can gain by connecting isolated, compact dc/dc converters in parallel or series allows low-cost, standard parts to meet system needs with minimal cost and space penalties
• Transistors tame perfidious leakage inductance - In flyback converters that use primary regulation, the loose coupling between the power secondary and the primary auxiliary windings often results in poor cross-regulation. This situation arises mainly from the leakage inductance but also comes from the level of the primary clamp voltage. This short article showss the circuitry you can adopt to avoid the leakage-inductance problems.
• Troubleshooting and Repair of small Switchmode Power Supplies
• Two diodes change demagnetization-signal polarity - some ideas for flyback design
• V2 Architecture Provides Ultra-Fast Transient Response in Switch Mode Power Supplies

Step-up converters

• 2 Watt Switching Power Supply - from 6V to 14V
• +30V power supply with +5V - This is a power supply which makes about +30V with +5V power supply. The high DC voltage (up to +50V) is made with the alternating voltage using the voltage amplification rectification circuit.
• 6V to 12V Converter - This circuit can provide up to 800mA of 12V power from a 6V supply. The circuit is simple, about 75% efficient and quite useful.
• 9-100v P.S.U. - This is the circuit for powering battery valve radio sets. It gives out 100V DC.
• Battery booster delivers 75W - uses isolated DC/DC converter in a nonisolated configuration to boost a 48V battery voltage to 60V
• Boost converter controls 12V fan from 5V supply - temperature-controlled PWM boost converter allows operation of a 12V brushless dc fan from a 5V supply
• Boost converter generates three analog rails
• Coilless step-up converter yields dual outputs - provides regulated 5 and 3V supplies from a wide input range without the need for inductors
• Converter has high efficiency at low loads - micropower components and circuit design of this converter enable it to maintain 90% efficiency for load currents below 8 mA, circuit outputs 5V DC
• DC to DC Converter - will produce a 85V voltage from +3V, usable for low power applications
• DC to DC Converter - low power converter which converts 3V to 85V, uses standard 12 VAC center tapped power transformer and single bi-polar NPN transistor
• Hex inverter makes low-cost switching regulator - simple and low-cost circuit converts 5V to 12V
• High power 12 V to 300 V invertor for high repeat rate medium power strobes
• High-voltage circuits for electrostatic microphones - circuits that can generate the required high-voltage for electrostatic microphones used in bat detectors, circuit can be used to generate a voltage of about 70V using a current of about 4 mA at 6V input voltage
• Li-ion boost circuit uses no inductors - circuit to mainstain regulated 3.3V supply for portable applications
• Low-cost switcher converts 5 to 24V - low-cost, three-transistor low power boost switching regulator
• One 9V battery gives +18, +25, +33V - how to make voltage booster using MAX1044 charge pump converter IC
• Panel meter power supply - isolated 9.1V 2-5 mA output from 8-30V input, in pdf format, text in Finnish
• Single cell lights any LED - This circuit allows you to light any type of LED from a single cell whose voltage ranges from 1 to 1.5V. This range accommodates alkaline, carbon-zinc, NiCd, or NiMH single cells. The circuit's principal application is in LED-based flashlights, such as a red LED in an astronomer's flashlight, which doesn't interfere with night vision. White LEDs make handy general-purpose flashlights. You can use the circuit in Figure 1 with LEDs ranging from infrared (1.2V) to blue or white (3.5V).
• Step-up/step-down converter takes 2 to 16V inputs - switcher where input can range above and below the regulated voltage, circuit accommodates a wide range of input and output voltages and supplies output currents as high as 500 mA

Step-down converters

• 3.3-V Supply Taps Power From The 12 V PCI Bus
• 5-to-1.8V Converter Works Without Magnetics
• Add trimmable current limit to dc/dc supply - you can add a simple, two-transistor circuit to a standard, step-down dc/dc converter to provide an adjustable limit for the output current
• Bipolar transistor boosts switcher's current by 12 times - This circuit uses a minimal number of external parts to raise the maximum output current of a 0.5A buck switching-regulator IC to more than 6A.
• Boost controller drives buck converter - by adding an external switching transistor, you can use a step-up dc/dc converter to step down voltages to produce an efficient battery-powered power supply, this example circuit can step down inputs as low as 2V to outputs as low as 1.25V, with efficiency as high as 80%
• Buck converter works efficiently from phone line - A switching converter provides an inexpensive way to generate 5V, 18 mA (48V, 5 mA maximum) directly from a standard phone line.
• Buck regulator generates flexible VTT for PECL - circuit to generate output which can both source and sink current
• Circuit provides 1.5V, 7A bus termination
• Inductorless converter provides high efficiency - produces a regulated 2V output with as much as 100 mA of load-current capability from 2.4 to 6V input voltage
• SEPIC generates 5V at 100 mA - Some applications require an input voltage higher than the breakdown voltage of the IC supply pin. In boost converters and SEPICs (single-ended primary-inductance converters), you can separate the VIN pin of the IC from the input inductor and use a simple zener regulator to generate the supply voltage for the IC. This design shows a SEPIC that takes a 4 to 28V input and generates 5V at 100 mA.
• Single resistor improves V2 converter - V2 control offers a significant improvement in transient response by using two voltage feedbacs, example circuit is for generatign voltages in 1.8-3.3V range
• Step-up/step-down converter takes 2 to 16V inputs - switcher where input can range above and below the regulated voltage, circuit accommodates a wide range of input and output voltages and supplies output currents as high as 500 mA
• Supply derives 5 and 3.3V from USB port - This circuit derives its power from a USB port and produces 5 and 3.3V supply rails for portable devices, such as digital cameras, MP3 players, and PDAs. The circuit allows the port to maintain communications while, for example, charging a lithium-ion battery. IC2 boosts the battery voltage, VBATT, to 5V, and IC3 buck-regulates that 5V output down to 3.3V.
• Switched-capacitor regulator provides gain - switched capacitor idea to convers 12V to 3.3V or 5V
• The MIC4680 Switching Regulator - simple circuit which outputs +5V
• Three-input supply powers 3.3V portables - single-ended primary-inductance converter accepts input voltages ranging from 3 to more than 6V and produces a regulated 3.3V, 200-mA output
• Wall-cube dc/dc converter is 85% efficient - ubiquitous 12V wall cube generates an unregulated dc voltage of 8 to 18V, depending on line voltage and load, this circuit generates a regulated 5V 400 mA from it very efficiently

Dual polarity output power supplies

• ±12V supply accepts 9 to 30V inputs - delivers more than 3.6W at ±12V and operates from inputs of 9 to 30V
• Current source forms unusually simple regulator - simple regulator uses a switching current source to drive a pair of shunt zener regulators, circuit produces ±15V dual outputs, for total output power of approximately 400 mW form 100-400V DC source
• Inverter forms high-efficiency rail-splitter - switched-capacitor voltage inverter can be used as "rail splitter" to provide bipolar, dual-rail power supply
• Simple DC-DC Converter Allows Use of Single Battery - Have you ever wanted to build a circuit to run off a single 9 Volt battery only to find you needed levels like +12 and -12 Volts? The thought of multiple batteries might have put you off. Why not use a simple DC to DC converter?
• Simple regulator provides ±12V - simple circuit can provide ±12V from a 5V input using only one switching-regulator IC and a few off-the-shelf components

Negative voltage generation

• +9V *and* -9V from one battery! - The MAX1044 is a charge pump converter - it uses a capacitor as a "bucket" to pump charge from one place to another. It can be used to generate negative voltage easily.
• Autotransformer regulator inverts 12V to produce ­12V - prodices output of 200 mA
• Circuit tricks increase LCD contrast - lack of a negative voltage to bias the LCD backplane severely limits the available LCD contrast on many displays, this circuit generates it
• Circuit variations produce negative voltages - you can easily configure basic switched-capacitor converters to also do some negative conversions
• DC/DC controller generates negative supply - a switch-mode power-supply controller plus a diode-capacitor network generate the modest negative supply current needed for op amps or for LCD bias, without inductors
• Negative Voltage Generator - takes in +12V and outputs around -11V
• One 9V battery gives +18, +25, +33V - This circuit is based on MAX1044 is a charge pump converter.
• Power inverter is bidirectional - This circuit can generate a negative output from a positive supply or a positive output from a negative supply. This example circuit is for ±9V and has 100 mA current rating.
• Simple boost converter generates ­27 and ­87V - generates the voltage levels necessary for standard telephones from 12V
• Voltage inverter - This circuit inverts the polarity of the input voltage (5-12V DC). The output is limited to less that 200mA. This power supply circuit is based on 555 timer and capacitor pump technique.

DC-DC converters with isolation

• Flyback circuit provides isolated power conversion - convert an unregulated 48V line to an isolated 5V, 15W output
• Isolated telecomm converter handles 25W - telecomm applications in the central office require an isolated 5V supply derived from ­48V, this gives out 5V at 5A from an input voltage of ­36 to ­72V
• Low-power converter has galvanic isolation - this simple dc/dc converter provides a 12V, 150-mW output using only a few components and a small transformer, CD4049 forms an oscillator that operates at approximately 200 kHz and runs the converter, regulated output
• Off-hook phone line supplies 150 mW - circuit draws current in the off-hook condition, delivering as much as 150 mW of isolated poser while allowing normal voice or data communications over the phone line
• Push-pull driver provides isolated 5V at 1A - regulated 5V input to an isolated 5V output with 1A current-output capability

Mains powered switchers

• 13.8 V / 15 A from a PC Power Supply - Depending on the PC model, power supplies are rated anywhere between 150 and 240 W. They are mainly primary switching power supplies with power switches arranged in a half-bridge configuration. This article describes how to modby a PC power supply to give 13.8 V output at high current. Most power supply units are designed according to the same principle (half-bridge configuration) and hence the following described modification should be applicable also to power supplies from other producers.
• CoolSET TDA16831..-34 for OFF-Line Switch Mode Power Supplies
• Electronic transformer dims halogen lamp - switched-mode power supply for a halogen lamp, commonly known as an electronic transformer, is a clever and simple device which can be enhanced with dimming control
• Miniature off-line supply delivers low power DC - simple circuit which takes 120V AC and outputs regulated 5V 30mA which is isolated from the mains line
• Open-loop power supply delivers as much as 1W - For VCRs, TVs, and other equipment that requires a standby mode, you must supply power to a µP when other components are asleep. Any active power-supply circuit also needs to be more cost- effective than the standard structure using a metallic transformer. This circuit is simple switcheer that takes 230V AC and outputs 10V 90mA
• Step-down rectifier makes a simple dc power supply - 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

Other switching circuits

• 5V Supply Derives Power From 3-Wire RS-232 Port - The circuit of Figure 1 produces a semi-regulated 5V output from an RS-232 port. Unlike a PC-mouse supply or comparable circuits that rely on the modem-control signals DTR and RTS, this one operates with a 3-wire port (GND, Rx, and Tx), and obtains power only from the Tx line. The output current-about 8mA-is sufficient for CMOS microcontrollers and other low-power circuits.
• Switch intelligently controls current - this circuit can intelligently control ac or dc current when connected in series with a load