Index

• Switchers
• Articles and resources
• Step-up converters
• Step-down converters
• Dual polarity output power supplies
• Negative voltage generation
• DC-DC converters with isolation
• Mains powered switchers
• Other switching circuits
• Repairing
• Related pages

Switched Mode Power Supply Page

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 usedfor voltage doubling or negative voltage generation).Switched capacitor type converters are generally used only forlow power applications.More often used technique for low and high power is switchedinductor converter. This converter type can be used for convertingvoltage up, voltage regulation and for current regulation. A basic power conversion circuit uses a transformer to convert higher voltage ac or dc current to lower voltage dc current in order to operate microelectronics-based devices in automotive, computing, communications, consumer electronics, and industrial applications. Another common functional element found in power conversion circuits is an optocoupler and voltage reference combination that provides isolated feedback from the transformer's secondary side to a device in the primary side for control purposes. 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 tearson the job, it's a bad idea to try to use a switching power supplyto power a sensitive analog circuit. Switch-mode power supplies tendto generate impressive amounts of noise - conducted through the powersupply rails, radiated, induced, etc. - and this noise can quiteeasily cross-couple onto your analog signal lines. For some analogueapplications switchers are suitable, but then you need to use avery "quiet" switcher type.

Articles and resources

• Embedded or discrete? Two types of planars fit for telecom applications - Planar transformers commonly used in dc/dc converters come in two basic types: embedded, also known as the integrated version; and as a standalone component type, also known as a discrete. Both forms often use windings made from wide and flat copper that is an inherent part of multilayer printed-circuit boards. Copper foil from lead frames and other sources can also be used. In general, planar transformers, with their ideally flat windings stacked thinly, are touted for their low profile for today's telecom requirements. While low-profile structures are not necessarily confined to planar construction, the planar transformer offers other significant advantages over traditional types in many applications.    Rate this link
• Reduce EMI by sweeping a power supply's frequency - Switching power supplies can be notorious noise generators. You should prevent this noise, which is conducted, radiated, or both, from returning to the input source, where it can potentially wreak havoc on other devices operating from the same input power. The goal of an EMI (electromagnetic-interference) filter is to block this noise and provide a low-impedance path back to the noise source. The larger the noise, the greater the size, expense, and difficulty of the filter design. Power supplies that operate at a fixed frequency have their largest EMI emission at this fundamental, fixed frequency. This circuit makes the switching converter operate over multiple frequencies rather than one, thereby reducing the time average at any one frequency. This scheme effectively lowers the peak emissions.    Rate this link
• 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.    Rate this link
• Add an auxiliary voltage to a buck regulator - You often need more than one regulated output voltage in a system. A frequently used and reasonably simple way to create this auxiliary output voltage is to add a second winding to the output inductor, creating a coupled inductor or a transformer, followed by a diode to rectify (peak-detect) this output voltage. The biggest drawback of this approach is that the diode's voltage drop varies with temperature and load current and can have a 2-to-1 variation, resulting in poor output-voltage regulation. This circuit idea describes an alternative approach that replaces this diode with a p-channel FET.    Rate this link
• A New Continuous-Time Model for Current-Mode Control - conference paper in pdf format    Rate this link
• 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.    Rate this link
• Cascaded power converters find acceptance as performance demands increase - With performance requirements on the rise, the benefits of a cascaded topology may outweigh its complexity. As performance requirements for power conversion have increased over the years, topologies that were often overlooked because of their added complexity are now finding wide use. One example is the current-fed push-pull topology. This article examines several cascaded topologies that are part of the buck-regulator family.    Rate this link
• 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.    Rate this link
• Circuit trade-offs minimize noise in battery-input power supplies    Rate this link
• 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    Rate this link
• 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    Rate this link
• 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.    Rate this link
• DC-DC Converter Tutorial    Rate this link
• Ridley Engineering Design Tips - information on transformer measuring and design and also general power supply design    Rate this link
• Feedback isolation augments power-supply safety and performance - properly designed isolated feedback is crucial to maintaining safety on many power supply designs    Rate this link
• 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    Rate this link
• 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    Rate this link
• Isolated Feedback Techniques for Power Supplies    Rate this link
• 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.    Rate this link
• Lazar's Power Electronics Corner - Virtual power electronics library: switching power supply circuit, magnetics and pcb design basics, topologies app notes, free software, simulators and calculators, engineering references, news, links and other info for power supply designers and users.    Rate this link
• 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    Rate this link
• Little ICs generate big voltages - ICs and small modules simplify the task of generating the high voltages for displays and their associated backlights    Rate this link
• Lower dc/dc-converter ripple by using optimum capacitor hookup - Low-ripple-voltage positive-to-negative dc/dc converters find use in many of today's high- frequency and noise-sensitive disk drives, battery-powered devices, portable computers, and automotive applications. A positive-to-negative converter can have low output-ripple voltage if you place the capacitors to the right places. Low-ESR output capacitors, such as ceramics, help to minimize the output-voltage ripple in dc/dc converters.    Rate this link
• Low-voltage power sources keep pace with plummeting logic and ?P voltages    Rate this link
• 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.    Rate this link
• 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    Rate this link
• 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    Rate this link
• Simplified calculation of magnetic and electrical losses in unity power factor boost regulators    Rate this link
• Slave converters power auxiliary outputs - Creative possibilities exist in deriving auxiliary rails from dc/dc converters. Slave converters, which are based on "transfer-function coincidences," offer tremendous potential.    Rate this link
• 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    Rate this link
• SMPS switch mode power supplies design - oftware tools and design examples    Rate this link
• 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    Rate this link
• Spreadsheet simplifies switch-mode power-supply flyback-transformer design - designing flyback transformers for switch-mode power supplies involves many calculations, this spreadsheet helps it    Rate this link
• Synchronous rectification aids low-voltage power supplies - synchronous rectifiers can improve switching-power-supply efficiency, particularly in low-voltage, low-power applications    Rate this link
• Switching converter uses planar magnetics - planar-magnetics technology is growing in popularity as a design option for dc-dc converters    Rate this link
• Switching-Mode Power Supply Design - A good power electronics circuit design hypertext with problem silving tips    Rate this link
• Switching-regulator design lowers noise to 100 ?V - 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    Rate this link
• Switching regulators demystified - Key to good design of switching-regulator circuits is a solid understanding of the fundamental theory of operation.    Rate this link
• Switching regulators demystified By Tom Mathews - You can see the proliferation of switching regulators throughout the electronics industry. These versatile devices can perform many functions, including voltage regulation, current regulation, or both. The fundamental theory behind the operation of the switching regulator is relatively simple. However, like any engineering endeavor, close attention to detail is important to avoid problems and poor performance. Key to good design of switching-regulator circuits is a solid understanding of the fundamental theory of operation.    Rate this link
• 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.    Rate this link
• 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    Rate this link
• 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.    Rate this link
• Troubleshooting and Repair of small Switchmode Power Supplies    Rate this link
• Two diodes change demagnetization-signal polarity - some ideas for flyback design    Rate this link
• Use a microcontroller to design a boost converter - Boost converters, like other switchers, have traditionally received their control signals from a dedicated circuit. However, a recent trend is to integrate simple switching-power-supply building blocks into generic devices, such as microcontrollers. An excellent example of this concept is a microcontroller that combines digital and analog circuitry and makes it easier to build simple power supplies.    Rate this link
• Transformers for SMPS - The availability of new materials for transformers working in frequency range of above 1MHz and the advances made in power electronics have given the development of high-frequency transformers new impetus. It has become possible to operate SMPS with switching frequencies of up to 500 kHz due to the development of fast-switching transistors and HF power ferrites. In resonance transformers frequencies of even up to 3 MHz can be achieved. This document compares the diffent transformer types for SMPS.    Rate this link
• Hysteretic regulators provide high performance at low cost - Hysteretic voltage regulators offer the potential advantages of simplicity, fast response, 100%-duty-cycle operation, high efficiency at light loading, and low cost. They need no loop-compensation components to add delays; thus, response time to a load change is less than one switching cycle. What's the catch? You must be able to accept a switching frequency that is not precisely controlled and a sensitivity to noise that requires layout skill.    Rate this link
• Method provides overpower protection for quasiresonant supplies - The main characteristic of quasiresonant switch-mode power supplies is that they exhibit a varying frequency when the input voltage changes. For a widely varying line-voltage application, the peak current almost doubles between high and low input voltages for a constant output power. But quasiresonant controllers feature only overcurrent protection. This limitation is part of a structural problem. The controller monitors the peak current, and, when they reach the maximum allowed value, the controller circuitry detects an overload. Unfortunately, if the power supply delivers its nominal power at the lowest worst-case input voltage, it delivers more power for a higher input voltage. For a widely varying line-voltage application, this power could be more than three times higher. This fact is the consequence of the flyback equation.    Rate this link
• Constant-on-time buck-boost regulator converts a positive input to a negative output - Buck regulators find wide application as step-down regulators for converting large positive input voltages into a smaller positive output voltages.    Rate this link

Step-up converters

• 2 Watt Switching Power Supply - from 6V to 14V    Rate this link
• +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.    Rate this link
• Battery booster delivers 75W - uses isolated DC/DC converter in a nonisolated configuration to boost a 48V battery voltage to 60V    Rate this link
• Boost 3.3V to 5V with tiny audio amplifier - This charge-pump circuit quietly converts a 3.3V source to 5V at 500 mA. National's (www.national.com) LM4871LD power amplifier makes this design idea both possible and practical.    Rate this link
• 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    Rate this link
• Boost converter generates three analog rails    Rate this link
• Coilless step-up converter yields dual outputs - provides regulated 5 and 3V supplies from a wide input range without the need for inductors    Rate this link
• 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    Rate this link
• DC to DC Converter - will produce a 85V voltage from +3V, usable for low power applications    Rate this link
• 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    Rate this link
• Hex inverter makes low-cost switching regulator - simple and low-cost circuit converts 5V to 12V    Rate this link
• 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    Rate this link
• Li-ion boost circuit uses no inductors - circuit to mainstain regulated 3.3V supply for portable applications    Rate this link
• Low-cost switcher converts 5 to 24V - low-cost, three-transistor low power boost switching regulator    Rate this link
• One 9V battery gives +18, +25, +33V - how to make voltage booster using MAX1044 charge pump converter IC    Rate this link
• Panel meter power supply - isolated 9.1V 2-5 mA output from 8-30V input, in pdf format, text in Finnish    Rate this link
• 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).    Rate this link
• 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    Rate this link
• Get just enough boost voltage - Adding a current-mirror circuit to a typical boost circuit allows you to select the amount of boost voltage and to ensure a constant difference between the input and the output voltages. This circuit is useful for high-side-drive applications, in which a simple voltage doubler is unacceptable because of the voltage range of the components involved or where the input voltage can vary widely. You can also use the circuit at the front end of a power supply to ensure that the PWM controller has enough voltage to start correctly in low-input-voltage conditions. The circuit maintains a 10V difference between VIN and VOUT, but you can easily change it to provide other voltages.    Rate this link

Step-down converters

• 3.3-V Supply Taps Power From The -12 V PCI Bus    Rate this link
• 5-to-1.8V Converter Works Without Magnetics    Rate this link
• 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    Rate this link
• 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.    Rate this link
• 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%    Rate this link
• 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.    Rate this link
• Buck regulator generates flexible VTT for PECL - circuit to generate output which can both source and sink current    Rate this link
• Circuit provides 1.5V, 7A bus termination    Rate this link
• Gate-drive method extends supply's input range - Industrial and telecom applications often require a nonisolated, low-voltage supply from a high-voltage input. IC manufacturers have responded to that need with the application of high-voltage processes and offer control ICs that work to 50V and higher. That voltage is sometimes insufficient, and you need further design techniques to extend the input voltage. This buck converter represents one such technique. This example circuit generates regulated 12V 0.2A output from 20-110V DC input voltage.    Rate this link
• 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    Rate this link
• 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.    Rate this link
• 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    Rate this link
• 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    Rate this link
• 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.    Rate this link
• Switched-capacitor regulator provides gain - switched capacitor idea to convers 12V to 3.3V or 5V    Rate this link
• The MIC4680 Switching Regulator - simple circuit which outputs +5V    Rate this link
• 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    Rate this link
• Three parts provide tenfold increase in switcher current - Industrial-control circuits often derive their power from widely varying sources that can exceed the 40V maximum rating of popular switching ICs. This Design Idea presents a simple, flexible, and inexpensive buck switcher that converts an input voltage as high as 60V to 5V at several amps. The circuit is unique in that it boosts current with almost no compromise in performance, size, or cost. This circuit uses LM2597HV switcher IC.    Rate this link
• Use a 555 timer as a switch-mode power supply - This article shows how to turn a 555 PWM circuit into an switch-mode power supply with only one simple equation. The example circuit is set to oscillate at approximately 60 kHz at a high duty cycle. You can supply 5V at 1.5A with an input of 9 to 40V. With 12V input, 5V, 1.5A output efficiency is approximately 70%, and it drops to 65% with a 40V input.    Rate this link
• 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    Rate this link

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    Rate this link
• 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    Rate this link
• Inverter forms high-efficiency rail-splitter - switched-capacitor voltage inverter can be used as "rail splitter" to provide bipolar, dual-rail power supply    Rate this link
• 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?    Rate this link
• 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    Rate this link

Negative voltage generation

• ICL7660, MAX1044 Switched-Capacitor Voltage Converters - The MAX1044 and ICL7660 are monolithic, CMOS switched-capacitor voltage converters that invert, double, divide, or multiply a positive input voltage. They are pin compatible with the industry-standard ICL7660 and LTC1044. Operation is guaranteed from 1.5V to 10V with no external diode over the full temperature range. They deliver 10mA with a 0.5V output drop.    Rate this link
• Simple circuit converts 5V to ?10V - This switched-capacitor circuit doubles, inverts dc source. Normally, the MAX889T voltage inverter converts a positive input to a negative output voltage with an absolute magnitude lower than that of its input. But, in this circuit, produce a higher output voltage.    Rate this link
• +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.    Rate this link
• Autotransformer regulator inverts 12V to produce ?12V - prodices output of 200 mA    Rate this link
• 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    Rate this link
• Circuit variations produce negative voltages - you can easily configure basic switched-capacitor converters to also do some negative conversions    Rate this link
• 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    Rate this link
• Generating -5VDC from +5VDC - simple capacitor pump circuit based on 555 chip    Rate this link
• Generating -5 Volts From a 9 Volt Battery    Rate this link
• Negative Voltage Generator - takes in +12V and outputs around -11V    Rate this link
• One 9V battery gives +18, +25, +33V - This circuit is based on MAX1044 is a charge pump converter.    Rate this link
• Positive regulator makes dual negative-output converter - Some systems, such as optical networks, require more than one negative voltage. This circuit is a positive-to-dual-negative dc/dc converter that converts 5V to both -5V and -10V, using a positive buck regulator.    Rate this link
• 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.    Rate this link
• Simple boost converter generates ?27 and ?87V - generates the voltage levels necessary for standard telephones from 12V    Rate this link
• 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.    Rate this link
• Constant-on-time buck-boost regulator converts a positive input to a negative output - Buck regulators find wide application as step-down regulators for converting large positive input voltages into a smaller positive output voltages. You can reconfigure a buck regulator into a buck-boost circuit to convert a positive voltage into a negative voltage.    Rate this link

DC-DC converters with isolation

• Flyback circuit provides isolated power conversion - convert an unregulated 48V line to an isolated 5V, 15W output    Rate this link
• 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    Rate this link
• 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    Rate this link
• 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    Rate this link
• Push-pull driver provides isolated 5V at 1A - regulated 5V input to an isolated 5V output with 1A current-output capability    Rate this link

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.    Rate this link
• Build a 13.8V, 40A Switching Power Supply - This site details a homebrew 40A/13.8V Mains 220/110V AC Switching Supply Designed for Ham Radio Applications originally. Published design in several magazines, details homemade magnetics used in the supply. This compact and lightweight workhorse can power your whole HAM radio station!    Rate this link
• CoolSET TDA16831..-34 for OFF-Line Switch Mode Power Supplies    Rate this link
• 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    Rate this link
• 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    Rate this link
• 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 ?P 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    Rate this link
• 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    Rate this link

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.    Rate this link
• Switch intelligently controls current - this circuit can intelligently control ac or dc current when connected in series with a load    Rate this link

Repairing

• SMPS Test Jig - This is a tip how to to test power supplies that will not start without a load.    Rate this link

Related pages

• Computer power supplies    Rate this link
• Electronics Wiring Page    Rate this link
• Electrical Wiring Surge Suppression    Rate this link
• Power supplies    Rate this link