A high-voltage power supply is one which generates a significantly higher output voltage than its input voltage. It may be an adjustable power supply, or the output may be fixed in voltage and current. Some high-voltage supplies output tiny amounts of current, while others can provide large amounts. These types of power supplies are often used in gas-based displays, scientific instrumentation and medical equipment. They can also power camera flashes, igniters and commercial radio transmitters.
The power supply output voltage may be as low as a few hundred volts or as high as many tens of thousands of volts. The power supply input can be from a battery, a low-voltage power supply or an alternating current (AC) source, depending on the design. Some supplies that produce a few thousand volts AC at relatively low currents are used in gas discharge and plasma displays. Ten kilovolt (kV) AC units may be used to power gas lasers. A high-voltage power supply producing a low direct current (DC) at about 2,000 volts often powers animal deterrent devices.
A high-voltage DC supply with extremely low current, such as 10kV at 500 microamperes (uA), is often found in electrostatic air cleaners. Precision DC supplies that are adjustable up to 30kV are common in electron microscopes and mass spectrometers. In these instrumentation supplies, the current is limited to just a few milliamperes (mA). Some types of X-ray equipment use a high-voltage power supply capable of 50kV at 5mA. Extreme care must be taken, as these power combinations can still be deadly despite the seemingly low currents.
Ignition systems and spark gap switches usually include DC supplies that can produce quick pulses of high current. This type of high-voltage power supply may produce dozens of 20-30kV pulses every second. It can also be found in triggers for camera flash units and in some devices designed to deliver electric shocks. Each high-current pulse is often created from a stored charge in a capacitor.
Very high-voltage AC supplies producing up to 20kV at just a few mA of current are less common. They usually include a means of adjusting the frequency of the AC voltage produced. A high-voltage power supply like this may be found in electrochemical applications, such as hydrogen and ozone production.
A high-current, high-voltage power supply is quite rare, sometimes producing 100kV at more than 20 amperes. These are usually found in special high-power radio frequency (RF) amplifiers, such as radar and radio transmitters. This type of power supply is also used in nuclear and other physics research.