The power supply is an energy converter that provides the required electric power.
There are two types of electrical energy, namely alternating current (AC) and direct current (DC), and the type required depends on the 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 that can be converted to a higher output voltage is called a high-voltage (HV) power supply. High voltage (HV) is also abbreviated as HV and is sometimes referred to as an HVDC converter.
DC power supplies have "plus" (+) and "minus" (-) terminals, which are referred to as positive and negative electrodes, respectively. 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, whereby neither the pole at the ground potential nor the negative pole is the return.

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, bipolar amplifiers, and HV amplifiers can operate as sources (power supplies) and sinks (loads), depending on the high-speed input signal. We refer to products with a built-in signal source as bipolar power supplies and products that amplify signals from external sources as bipolar amplifiers. Among the bipolar amplifiers, high-speed and HV products are called HV amplifiers.

A power supply that has the functions of a power supply and an electronic load and regenerates the power at the time of the electronic load to the supply network is called a bidirectional power supply (regenerative power supply). A battery cycle tester repeatedly tests the charge and discharge of a battery.
Other application-specific power supplies include those for electrostatic chucks used in semiconductor manufacturing equipment and piezoelectric drivers for piezoelectric devices.