Because of high variety of types of electrical transformer used in electronic circuits we describe bellow in this article most used electrical transformer types.
The transformer is an electrical device that, by electromagnetic induction, transforms electric energy from one or more circuits to one or more other circuits at the same frequency, but usually at a different voltage and current value.
Also the transformer provides DC isolation between the input line and the output. It also performs a voltage step-up and/or stepdown function for the supply.
If the transformer is improperly designed, it would adversely affect the supply operation
and the reliability of the semiconductors.
All types of electrical transformers used in electronic circuits basically consists of two inductors. One of these inductors is meant for supplying alternating current from an external source and is referred as a Primary Winding. The other coil, in which Primary Winding induces the voltage, is known as Secondary Winding.
If two coils are placed near each other, the change in flux in one coil will cut the turns of the other coil and will induce a voltage in it. Then these two coils are said to have mutual inductance.
Types of electrical transformers used in electronic circuits are:
Power-supply transformers available in two types:
-step-down transformer that decreases the AC voltage
-step-up transformer that increases the AC voltage.
The AC output frequency from a transformer is always the same as the AC input frequency.
Bellow are described some types of electrical transformers used in electronic circuits.
Audio Frequency Transformer (AFT)
These transformers are used in audio amplifiers and are similar to the power transformers but differ in the constructions and material of the core
Audio frequency transformer is made to operate at audio frequencies in the range of 20 HZ to 20 kHz. They are similar to the power transformers but differ in the constructions and material of the core. They are always used to couple one stage to another and are available in both types as step up as well as step down transformers.
Radio Frequency Transformer (RFT)
Radio frequency (RF) transformers operate at very high frequencies and are generally used with capacitor to form resonant circuits.
Radio frequency transformer is also used for inter-stage coupling in electronic circuits, and for coupling a signal to and from antenna.
Intermediate Frequency Transformer (IFT)
Intermediate frequency range lies between the audio frequency and radio frequency range. These transformers are meant to operate at a fixed frequency, known as intermediate frequency.
IFT Transformers are also used in the inter-carrier (TV Receiver) sound section of television.
In autotransformer, same coil is used to provide turns for the primary as well as for the secondary. If whole part of the coil is used as a primary winding and small part of coil is used as a secondary winding, then it is called as step-down transformer.
If small portion of the entire winding is used as a primary winding and entire winding is used as a secondary winding, then it is known as step-up transformer. They are also provided with fixed or variable taps for varying the secondary voltage .
It reduces the possibility of electric shock from the equipment. It is also used in audio frequency equipment and to block the DC component.
Isolation transformer has two coils having 1 to 1 turn ratio, same numbers of turns for the primary winding and secondary winding, then the transformer formed is known.
Driver transformers are similar to inter-stage transformers but they are required to supply current (or base current) to the driver stage. Driver transformers are rated for primary and secondary impedance ratio.