There is no one universally agreed definition of what constitutes high voltage, and various industry standards are likely to have different voltage classifications. The International Electrotechnical Commission, which is recognised as a leading international standards organisation define high voltage circuits as those with more than 1000V for alternating current (AC) and at least 1500V for direct current (DC). This is distinguished from low voltage which is generally considered to be 50-1000V AC or 120-1500V DC. The United States Department of Energy (DOE) consider high voltage to be anything above 600V.

Power supplies are constrained by the amount of voltage and current that they can supply. Put simply, a power supply is a device that supplies electrical energy to one or more electric loads, and thus a high voltage power supply converts a lower voltage potential to a higher voltage potential, although as previously established definitions vary. Broadly speaking, typical high voltage power supplies range from 100V to 500kV with output power rating ranges from 1W to 40kW dependent on application, and operate from either DC or AC input voltages. The actual power of the supply is measured in watts, which equals voltage multiplied by current, however they are frequently categorised by their application rather than by their power capability.

Whilst many people remain unaware of the applications and uses of these power supplies, they are often used in equipment in which a consumer may have contact with. This includes baggage scanners at airports, and to assist certain industrial processes, for example deflection plates in Continuous Ink Jet Printers allow date codes and other information to be printed onto food and beverage containers, cosmetics, chemicals and pharmaceuticals.

High voltage power supplies have also become of fundamental importance across the medical industry and can be found in a variety of equipment including X-ray machinery and other large diagnostic equipment as well as applications used to remove unwanted hair, tattoos and other vascular treatments.

Other key market sectors include: semiconductors, instruments and inspection, scientific analysis and more specialised industrial applications such as electron beam welding, Electrostatic Flocking, Electron Beam Melting, Sputtering and many more.

Given the technical complexities and specific requirements posed by the various industries and pieces of equipment it is often necessary for organisations to consider a custom application in order to meet their specifications.