LAZAR's POWER ELECTRONICS GUIDE SMPS SWITCHING POWER SUPPLY DESIGN BASICS
The electric energy obviously is not used in the form in which it was produced or distributed. All electronic systems require some form of energy conversion, which can be accomplished by different methods. In a power supply unit (PSU) electric energy transfers from a source to a load by using electronic circuits. Here I'll tell you some general things about it for those new to this subject. Note that of course, a PSU does not really supply power, it just converts it from one form to another, so "converter" would be a more accurate term for such a device. A typical application of a power supply is to convert utility AC voltage into a set of regulated DC voltages required for electronic equipment.
Back in the 70's, most PSE were linear, efficiency was around 50%, power density was less than one watt per cubic inch, and power factor was 0.5-0.7. Nowadays most PSUs are of SMPS type with efficiency over 90%, power density of tens of watts per cubic inch, and power factor up to 0.99. This type is the main subject of this site. WHAT IS IT? SMPS stands for switched mode power supply. It is an electronic device in which energy conversion and regulation is provided by power semiconductors that are continuously switching with high frequency between "on" and "off" states. An output parameter (usually output voltage) is controlled by varying duty cycle, frequency or a phase shift of these transitions.
HOW DOES IT WORK? The energy flow in any PSU is controlled by power semiconductors. However, in different systems they can operate in different modes. In legacy systems they worked in linear mode and excessive power dissipated in a series transistor. Unlike linear mode, a semiconductor that operates in a switching mode can control energy flow with low losses. Indeed, when a switch is "on", it has low voltage drop and will pass any current imposed on it; when it is "off", it blocks the flow of current. As the result, in such a circuit the power dissipation being product of voltage and current, can be relatively low in both states. That's why switch mode PSUs offer greater efficiency compared with linear ones. Such units are also smaller in size and lighter in weight due to the reduced size of passive components and lower heat generation. The industry trend toward miniaturization, advancements in semiconductor technology, as well as various energy efficiency regulations have made "switcher" the dominant type of PSU across practically the full spectrum of applications. For AC input applications most PSU manufactured today also include another conversion stage- a power factor correcting (PFC) front end. There is a huge variety of complete off-the-shelf power supplies and DC-DC modules on the market to meet most practical requirements and safety standards. Nevertheless, custom designs are still being done when there is a need for special characteristics or an unusual form-factor, particularly for harsh environment military applications or avionics.
In general, SMPS converters can be classified into four types according to the form of input and output voltages: AC to DC (also called off-line DC power supply), DC to DC (voltage or current converter), AC to AC (frequency changer or cycloconverter), and DC to AC (inverter).
Power supply design is a cross-disciplinary task. It involves the circuit, magnetics, thermal management, control and compliance issues. This site is SMPS/power electronics information guide. Here you will find a tutorial, tools, reviews, schematics, and other free online resources on all aspects of switching power supply design and selection, information on other energy conversion devices, as well as basic electrical engineering reference and electronic formulas.
POWER ELECTRONICS / SMPS DESIGN- THEORY & TUTORIALS TI (Unitrode) seminar books online
Power supply design tutorial - basic concepts and operation Glossary of energy conversion and power electronics technology terms
FREE SIMULATION SOFTWARE AND CALCULATORS
Find open source circuit simulation programs, working demos of analog and mixed-signal simulators, and other engineering
software & calculators
Quick online quiz- how well do you know power supply safety
PSU TOPOLOGIES: APPLICATION NOTES, GUIDES, SCHEMATICS
Switching mode converter topology selection
A review of standard computer PSU connectors and pinouts
The basics of switched mode regulators, design guides, SMPS circuit diagrams, and other design resources
PCB DESIGN OF ELECTRONIC CIRCUITS Layout guidelines for printed circuit board; Trace spacing for voltages;
Trace width calculator per IPC-2152;
Guidelines, calculators, and other PCB design resources.