What is a Bench Power Supply?

Mal Baxter

A bench power supply is a desktop or modular device that delivers electrical energy to one or more electrical loads. Typically occupying a technician's bench, it may convert alternating (AC) or direct current (DC) loads from one form to another, with outputs supplying preset amounts of voltage and amperage. These devices differ in amounts of energy they can provide, number of outputs, duration and stability of supply under various load conditions, and whether the energy they supply is continuous or pulsed. The equipment is used for testing, maintenance, and product development.

An oscilloscope can be used to measure the efficiency of the power transfer through the bench power supply.
An oscilloscope can be used to measure the efficiency of the power transfer through the bench power supply.

Many varieties of bench power supply devices are available; they usually transfer power from a main source to lower voltages at varied efficiencies. Voltages and amps can be adjusted to user-defined parameters. These sources can power-test equipment for building or fault-finding, and spare the trouble of maintaining a stable source of power for DC or battery-operated components. AC supplies might generate power for computer components and other demanding applications. Numerous types of devices can include variable or constant voltage/current supplies, multiple output, programmable, and multirange supplies.

Power does not transfer at 100% efficiency, but can dissipate through heat. This requires that a source be able to produce greater power than required by the application. Output voltage can be regulated with load or line voltage changes. A bench power supply converts input power to a constant voltage and current output, and may even convert AC to DC power. The efficiency of the interaction between power supply and power monitoring can be aided by the use of an oscilloscope, which multiplies current and voltage waveforms.

DC power supplies take AC from a source for conversion to direct current. Two forms of bench power supply approach this task differently. Linear power describes the process of converting power from a greater to a lesser source: for example, using the electricity from a 110-volt (V) wall socket to convert into 12-V energy needed to power a small electronic component that would otherwise drain batteries.

Switching power refers to the practice of stepping up, stepping down, or inverting input voltage. Supply design specifications include voltage and current ranges, type and number of outputs, and programmability. Two other considerations include the amount of periodic and random deviations a device may introduce, called ripple and noise.

The least expensive bench power supply products, usually DC, serve common electromechanical and electronic hobbyist applications. Midrange supplies cost more, equipped for the multiple outputs and voltage ranges needed for laboratory work. These devices tend to offer more precise efficiency and metering; they may also provide needed linear or switching functionality. Higher-end equipment provides more programmability, higher voltage capabilities, and multiple independent outputs. These devices may also interface with computers to extend their capabilities, and can serve laboratory, research, and development applications.

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