GLOSSARY OF POWER ELECTRONICS TERMS
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GLOSSARY OF POWER ELECTRONICS TERMS |
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AC: alternating electric current (current that reverses direction) AC power supply: a PSU that generates an AC output voltage (also called inverter). Convection-cooled power supply: a PSU that is cooled from the natural motion of an air over the surfaces of its components. DC power supply: a PSU that converts AC input voltage into DC output voltage, i.e. into a voltage of a fixed polarity and specific value (which can be variable though). External power supply: a PSU that is located outside of the equipment and can power more then one electronic device See also: Isolation Isolation: absence of DC current pass between two circuits. In a PSU isolation is provided by transformers. Commercially available AC-DC PSU are normally isolating. Low input voltage DC-DC PSU are often non-isolating, such as a car phone charger. Note that isolation does not mean a complete absence of current path- some AC currents can still flow from input to output through physical and/or stray capacitance. Linear power supply: a PSU that regulates the output parameter (usually output voltage) by varying voltage drop across an electronic component placed in series with the load which dissipates unused power. This component may be a power semiconductor or a resistor. The regulation is accomplished by changing the semiconductor's effective resistance or by forcing extra current through the resistor. Off-line power supply: a PSU that processes electric power directly from AC line without using line frequency transformer. Such supply can still be isolating if it uses high frequency transformer in one of its power conversion stages. A typical off-line SMPS rectifies input AC line voltage, converts it into high-frequency AC voltage by using semiconductor power switches, steps that voltage up or down by using inductors and/or transformers, then rectifies it again and filters for DC output. An example of isolating off-line PSU is a computer switching power supply. PARD: Periodic and Random Deviation from the power supply's output DC voltage. Includes ripple and aperiodic noise. PARD is usually expressed in mV peak-to-peak or rms, at a specified bandwidth, typically 20 MHz. Power supply: a device that transfers electric energy from one form to another using electronic circuits. Also called Power Supply Unit (PSU). A common application of power supplies is to convert mains AC power into a low-level DC voltages required for an electronic equipment. Unlike generators, it does not need any moving parts. PSU: see Power supply. Regulated power supply: a PSU that maintains a given output parameter (usually output voltage) to within specified limits under varying operating conditions, such as input line, output load, ambient temperature. SMPS: see Switching power supply Switching power supply (switch mode, or SMPS): a PSU that incorporates power handling electronic components that are continuously switching on and off with high frequency in order to provide the transfer of electric energy. An output parameter (usually output voltage) is controlled by varying duty cycle, frequency or a phase shift of these transitions. SMPS frequency can vary typically from 20 kHz to several MHz. Uninterruptible power supply (UPS): a PSU that continues to supply electric power to the load for limited periods of time during a loss of utility's power or when the line voltage varies outside normal limits. UPS is normally implemented with a backup battery and an additional DC-AC inverter. Universal input power supply: a PSU that can operate at AC line voltages found anywhere in the world (typically from 90 to 264 VAC). Voltage converter: technically it is the same as a power supply, except the term "converter" is often used for a single-stage SMPS. A typical off-line switching power supply may consist of several cascaded voltage converters. The term converter also often implies an incomplete PSU, which may need additional components (filters, protective devices, housing, etc.). |
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