A power supply (or power supply unit) is an electrical device that supplies electric power to a load.
Electrical power is primarily available in two forms: alternating current (AC) and direct current (DC). The required form depends on the specific electrical equipment.
Generally, the power supplied by power plants through transmission lines is AC. Devices that require DC must convert the AC to DC.
Devices that convert AC to DC are called AC adapters, AC-DC converters, or DC power supplies.
Other types of power supplies include DC-DC converters, which convert DC voltages, and AC power sources, which convert AC voltages and frequencies.
A power supply designed to output high voltage is called a high-voltage (HV) power supply. When it provides a DC output, it is specifically known as a high-voltage DC power supply.
DC power supplies have positive (+) and negative (-) output terminals. A DC power supply can be used as a positive power supply by setting the negative pole to the ground potential, and as a negative power supply by setting the positive pole to the ground potential. It can also be used as a floating power supply, where neither terminal is referenced to ground, providing galvanic isolation for the output.
HV-DC power supplies are available in the positive (P) type, which can output only positive polarity; the negative (N) type, which can output only negative polarity; the reversible (R) type, which can switch polarity; and the PN type, which has output terminals for both positive and negative polarities.
Power supplies that can continuously alternate between positive and negative polarities include AC power sources, bipolar power supplies, bipolar amplifiers, and HV amplifiers. The AC power source provides a more stable AC than an AC power source supplied by an electrical outlet. It can also simulate regional AC power sources at different frequencies and voltages.
Bipolar power supplies and amplifiers are four-quadrant devices, meaning they can operate as both a source (supplying power) and a sink (absorbing power). Typically, we define "bipolar power supplies" as units with a built-in function generator, while "bipolar amplifiers" amplify an external input signal. Among the bipolar amplifiers, high-speed and HV products are called HV amplifiers.
A power supply that functions as both a DC power supply (source) and a DC electronic load (sink), and can return the absorbed power to the AC power grid, is called a bidirectional or regenerative power supply. This capability is ideal for applications like battery cycle testers, which repeatedly charge and discharge batteries to evaluate their performance.
Other application-specific power supplies include those for electrostatic chucks used in semiconductor manufacturing equipment and piezoelectric drivers for piezoelectric devices.
