Switchers ( 118 ) :

• Articles and resources

• 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.   
• 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.   
• 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.   
• 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.   
• 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.   
• 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.   
• DC-DC Converter Tutorial   
• 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   
• 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.   
• 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.   
• 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   
• 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.   
• Low-voltage power sources keep pace with plummeting logic and �P 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   
• 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   
• 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.   
• 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   
• 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 �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   
• 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   
• 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.   
   

• 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.   
• Battery booster delivers 75W - uses isolated DC/DC converter in a nonisolated configuration to boost a 48V battery voltage to 60V   
• 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.   
• 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   
• 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.   
   

• 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   
• 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.   
• 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   
• 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.   
• 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.   
• 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   
• Generating -5VDC from +5VDC - simple capacitor pump circuit based on 555 chip   
• Generating -5 Volts From a 9 Volt Battery   
• 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.    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.   
• 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.   
• 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!   
• 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 �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   
• 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   
   

• Repairing

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

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