Flyback Transformer – Working, Advantages & Applications

Flyback Transformers are electrical transformers that produce high voltage signals and strong boosting capacity at a high frequency. They can be operated over a range of input voltage & load conditions. Also known as coupled inductors, they provide circuit isolation and encourage both positive or negative output voltages. Usually, these transformers are designed as voltage converters or circuit isolators. Then, they are used for flyback converters and installed for other applications.

In this article, we’re going to discuss some key things you should know about flyback transformers to find out if they are ideal for your applications.

Flyback Transformer

How do Flyback Transformers work?

The working of flyback transformers is based on the flyback topology. When it is time for operation, they are installed along with electronic devices in an integrated circuit. Owing to this, the functioning of the transformers shows some changes, but the topology is the same. Below are the steps that depict how they operate in real-time.

  1. The flyback transformer is powered by a switch when it is installed in an integrated circuit. When you turn the switch on, the DC voltage passes through the primary winding.
  2. When this ramp current passes through the primary winding, it generates magnetic inductance.
  3. This inductance is stored as magnetic energy in the transformer’s gap until there is a command from the secondary winding. The energy storage depends on the flyback topology.
  4. The secondary winding is integrated with a diode that transfers the current to electronic devices. When the diode commands current, the magnetic energy stored in the gap is passed to the secondary winding.
  5. Finally, the current is transmitted to the diode and then to the electronic device.

On an input of 230 V, these transformers give an output of 20,000 V. Not only this, they can also operate at very low voltages, from 5 V to 12 V.

Advantages of Flyback Transformers

  • A flyback transformer is a cost-effective choice for stepping power up & down because it is made using lesser components.
  • It is smaller, lighter & easier to install in your electrical system.
  • It is easy to operate across a range of input voltage.
  • It can supply multiple voltages while it is isolated from the primary winding.
  • It can regulate multiple voltages in a single control.
  • It is produced using only a few components as compared to other SMPS.
  • Its primary winding is separated from the output.
  • It contains circuit isolation which prevents electrical hazards & provides greater safety to things in proximity to high-energy electrical devices.

Major Flyback transformer Applications

Flyback transformers are a popular choice for isolated power supply designs up to 120 Watts. Other major applications are:

  • LED Fixtures
  • Solar Microinverters
  • Telecommunications
  • AC-DC Power Supply
  • CRT Displays, like Television & Computer Monitors
  • Capacitor Charging
  • Battery Charging
  • Industrial Motors
  • Generators
  • Pumps
  • Electric Converters
  • Power over Ethernet (PoE)

Designing of Flyback Transformers

The designing & construction of a flyback transformer differs from that of conventional transformers. It is made using a few electrical components, such as primary switch, mutually coupled inductor, input & output capacitor, & output rectifier or diode. Here are the steps involved in the construction of these transformers.

  1. First, the primary coil is wound around a ferrite rod or bobbin, which forms the initial part of the inductor circuit.
  2. Then, the secondary coil is wound around the primary coil, which forms the second part of the inductor circuit. This construction of the secondary winding over the primary winding helps to reduce leakage inductance.
  3. The secondary coil is now wrapped with a film insulation to provide dielectric material for high voltage assembly.
  4. Next, a gapped ferrite core is used between the primary & secondary windings. The gap in the core induces magnetic reluctance. As a result, the magnetic field lines remain within the core gap & winding.

Further, it is also integrated with a switch, input & output capacitor, and output rectifiers in electronic applications. When the switch is turned on, it allows the flow of voltage through the primary winding.

The capacitors store electric current when they are attached to the transformer assembly. The primary winding energizes the core gap while the output rectifier stops the secondary current flow.

Things to Consider while designing Flyback Transformers

You can produce flyback transformers in unique designs & configurations, but there are a few things you should consider before designing them to suit your requirements. They include:

  • Maximum size & weight
  • Switching frequency
  • Input voltage
  • Power & output voltage
  • Type of mounting
  • Performance & Efficiency
  • Estimate of costing

How can you test a Flyback Transformer?

A flyback transformer can be tested in several ways. If you want to check for defects in the winding, you can use a line operated potential transformer. If there is open winding, the tester will show a high impedance in the windings, and if there is a short circuit, it will show lower impedance. In modern testers, a graphical display can also show the quality of the winding.

If you are looking for defects in the capacitor’s opening, there will be a lot of noise. A tic-tac like noise will be seen on the monitor. While in the shorting of the capacitor, the display will be empty, showing a power blink. If this happens, you need to replace the old capacitor and install a new one.

Some other common issues that are found in the transformer include crack in the core, shorting of windings, and external arcing to ground. All these issues can be tested using the line-operated tester. You can also try a multimeter to check the continuity of the circuit and examine the amount of voltage at any ‌point.

Conclusion

Flyback transformers are an efficient & cost-effective choice for your industrial applications. With advancements in technology, they are gaining importance for several applications, particularly renewable energy. The quality of flyback transformers has a direct influence on their performance, hence you must source them from trusted manufacturers & suppliers in the market.

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