Power Electronics Circuits
Which of the following correctly describes the operation of a flyback converter?
- AWhile the switch is on, energy is sent directly from the input to the output through the transformer, and while it is off, the secondary diode is reverse biased and nothing happens
- BWhile the switch is on, energy is stored in the transformer (a coupled inductor), and while it is off, it is released to the output through the secondary diode
- CIt converts the voltage with only a mains-frequency transformer and diodes, without any switch
Show answer and explanation
Answer: B. While the switch is on, energy is stored in the transformer (a coupled inductor), and while it is off, it is released to the output through the secondary diode
The transformer of a flyback converter works as an inductor with coupled primary and secondary windings. While the switch is on, the secondary diode is reverse biased, the primary current rises and magnetic energy is stored. When the switch turns off, the winding voltages reverse, the diode conducts and the stored energy is released to the output. With few parts it is widely used in small power supplies up to about 100 W, such as AC adapters, but the surge caused by the leakage inductance of the transformer must be suppressed with a snubber circuit.
- A. Sending energy directly to the output while the switch is on is how a forward converter operates.
- B. Correct. Like a buck-boost converter, it stores energy and then releases it.
- C. A flyback converter switches at high frequency.