If you have not heard of flyback transformers, that doesn’t mean you may not have worked with one in the past. This particular type of transformer may also be known as a line output transformer or a LOPT.
This is a special type of transformer that is not used in all types of applications but typically reserved for switched-mode power supplies or SMPS.
It can be used for both high and low voltage and is considered a very reliable, durable, and dependable transformer for these types of applications.
The Origins
The origins of flyback transformers are actually very specific. They were originally designed for use in the cathode ray tube or CRT systems and were developed to control the movement of the electronic beam within the tube.
When flyback transformers are provided with a DC supply, typically from a transistor and the switch is turned on, there is a build-up of the current in the system. Unlike an inducer, the secondary winding is connected to a diode in a series, which prevents the development of a secondary current.
This continues to build, and when the switch is cycled off, the current that is stored or contained in the primary winding will naturally collapse. This energy that has been building up will then be stored in the magnetic core. Once the output winding voltage reaches a set level, it begins to flow in a descending ramp, the opposite of the ramp used to create the energy.
The Design Features
In discontinuous mode flyback transformers, the secondary current may completely discharge, or reach a zero level. With a continuous mode there is some level of energy that is always present in the core.
In almost all of the flyback transformers the primary winding is around a ferrite rod, and then the secondary winding will be loosely around that primary. The proximity of the two windings tends to reduce any leakage and result is a very efficient system. This is further enhanced by the use of an enameled wire for the outside winding.
While originally used for CRT for televisions, the flyback transformers of today can also be found in computer monitors. In these types of applications replacing the transformer may need to also include an upgrade or a reload of the firmware in the system to ensure optimal performance as there can be variations between transformers, even within the same model and manufacturer.
