SLUAAB9A March 2021 – December 2021 UCC25800-Q1
In this case, the full-wave rectifier is used. The output voltage gain is halved compared with the one using voltage doubler. The output capacitor Cout still needs to be much larger (> 10 times) than the resonant capacitor. Or in other words, the output capacitor Cout can be considered as a high-frequency short at the switching frequency
Other than these three rectification methods, the center-tap method can also be used. However, the center-tap method can only be used with primary side resonant and it is less preferred.
It can also be shown that, with all these three rectification methods, the transformer secondary side is in series with a capacitor. Together with the primary side DC blocking capacitor, the transformer saturation caused by DC offset can be avoided.
Table 4-1 summarizes the difference among these three rectification methods. In this table, "n" represents the transformer primary-side to secondary-side turns-ratio (NP : NS).
Rectification Method | Resonant Capacitance | Voltage Gain |
---|---|---|
One resonant capacitor, voltage doubler | Cr | 1/n |
Two resonant capacitors, voltage doubler | 2Cr | 1/n |
One resonant capacitor, full-wave rectifier | Cr | 1/2n |