A History Guide to the Flyback Transformer

A flyback transformer is a high voltage and a mid to high frequency transformer that used to only power CRT monitors and televisions. Also referred to as a line output transformer, they used to generate voltages ranging from 10 to 35kV.

Types of Flyback Transformers

Depending upon the age of the TV or CRT monitor, the flyback transformers can be classified into the following types:

6-8kV AC Flyback Transformers:: These flyback transformers were commonly installed in various color television sets of the 1980s. Generally, they are used in combination with a voltage multiplier. They have an absolute maximum output voltage up to 10kV at 15 kHz (PAL horizontal frequency). These transformers have many layers of insulation layers, and the primary winding is placed below the secondary. They are ideal for all low voltage applications with higher current needs.

Custom Flyback Transformer

10kV AC Compact Flyback Transformer:: These transformers are found in portable black and white television sets. Generally, they are used with an external rectifier block. The secondary winding of these transformers is typically dipped in epoxy. The maximum output voltage of these transformers 12-14kV AC. Hence they are not considered suitable for higher voltage applications and high output currents.

DC Flyback Transformer:: This transformer is similar to AC flyback in terms of construction and applications. However, it has a high voltage rectifier that is integrated into its secondary winding, which makes it a DC flyback. Also, it has considerably less secondary turns.

DC Flyback Transformer

Disc-shaped AC Flyback Transformer:: These transformers were common in black and white sets from the early 1960s up to the late 1970s. Generally, they are used along with a vacuum tube rectifier. They have maximum output voltage over 20kV AC at 15 kHz. 

Disc-shaped AC Flyback Transformer

DST flybacks (Diode-split Transformers): These DC flybacks can be found in every modern CRT TV-set manufactured after the mid-90s. They have an integrated high voltage filtering capacitor for dynamic focus. This capacitor allows the flybacks to hold a large amount of charge for a long time. Typically, they are able to provide an output voltage up to 30kV.

Today, flybacks have found many more uses in newer circuits. They are used extensively in switch-mode power supplies. They are often preferred due to their overall lower component count and reduction of PCB real estate.

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