Electronic transformers are designed especially for low-power applications. They are used in computers, radio frequency (RF) devices, and lighting. Electronic transformers are used to insulate circuits and to provide high to alternating-but-low impedance. They are also used to modify or maintain frequency response and wave shape at varying potentials. Because electronic equipment uses electron tubes, electronic transformers must provide appropriate bias voltage values for proper operation. Since weight and space are important considerations in designing electronic equipment such as handheld devices, electronic transformers are smaller and lighter than older power transformers.
There are many different types of electronic transformers. Flyback transformers (FBT) or line output transformers (LOPT) are designed to produce a very high output voltage from a relatively low input voltage. Pulse transformers interface a pulse forming network (PFN) and a load. By matching the impedance of the load to the PFN, they maximize power-transfer efficiency. Rectifier transformers produce a DC voltage or current and are used to drive a diode or thyristor. RF transformers are used for impedance matching over the RF spectrum. Switch mode transformers or switching transformers provide an energy storage element for transferring energy to input-to-output in discrete packages. These electronic transformers are used in switching power supplies, regulators, and converters.
Electronic transformer types include LAN transformers, gate drive transformers, and toroidal cores. Local area network (LAN) or telecommunications transformers are used in applications that require high bandwidth and fast switching speeds. The signal is isolated between primary and secondary grounds. Gate drive or trigger transformers are used to drive high-speed switching devices such as field-effect transistors (FETs) or insulated-gate bipolar transistors (IGBTs). Toroidal core transformers consist of copper wire wrapped around a cylindrical wire. Electronic transformers that are designed in this way prevent the magnetic flux that occurs within the coil from leading.
Selecting electronic transformers requires an analysis of winding turns and performance specifications. There are four choices for winding turns: step-up, step-down, variable, and one-to-one. Performance specifications for electronic transformers include operating temperature, power rating, operating frequency range, maximum primary voltage rating, and maximum secondary voltage rating. Because electronic transformers with use with several nominal voltages require more than one primary winding, the maximum voltage for the application is required.