A flyback transformer (FBT), also called a line output transformer (LOPT), is a special transformer,
which is used for conversion of energy (current and voltage) in
electronic circuits. It was initially designed to generate high current
sawtooth signals at a relatively high frequency. In modern applications
is used extensively in switched-mode power supplies for both low (3V) and high voltage (over 10 kV) supplies.It was invented as a means to control the horizontal movement of the electron beam in a cathode ray tube (CRT). Unlike conventional transformers, a flyback transformer is not fed with a signal of the same waveshape as the intended output current. A convenient side effect of such a transformer is the considerable energy that is available in its magnetic circuit. This can be exploited using extra windings that can be used to provide power to operate other parts of the equipment. In particular, very high voltages are easily obtained using relatively few turns of winding which, once rectified, can provide the very high accelerating voltage for a CRT. Many more recent applications of such a transformer dispense with the need to produce high currents and just use the device as a relatively efficient means of producing a wide range of lower voltages using a transformer much smaller than a conventional mains transformer would be.[citation needed]
The flyback transformer is used in the operation of CRT-display devices such as television sets and CRT computer monitors. The voltage and frequency can each range over a wide scale depending on the device. For example, a large color TV CRT may require 20 to 50 kV with a horizontal scan rate of 15.734 kHz for NTSC devices. Unlike a power (or 'mains') transformer which uses an alternating current of 50 or 60 Hertz, a flyback transformer typically operates with switched currents at much higher frequencies in the range of 15 kHz to 50 kHz.
