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2.3. Flyback

It is also called reverse or backward converter. This circuit can supply an output signal with a voltage higher or lower than the in put voltage, but always with an opposite polarity to the latter one. Figure 7 shows a simplified schematic diagram of the converter. The operation cycle is as follows: During the Q on period, the L coil current increases linearly, and the coil stores energy. When Q is no longer on, the coil current keeps flowing, now discharging the stored energy, through diode D. This current charges the C output capacitor. Figure 8 shows the isolated version of this converter, where the coil has been changed to a transformer, which enables the output to be isolated from the input and, if multiple secondary taps are used, a converter with several outputs can be obtained.

Figure-7

Figure-7

Figure-8

Figure-8