The RC peak absorption problem of Flyback's secondary rectifier diode 3

Adopting RCD absorption, the absorbed energy includes two parts: one is the DC energy on capacitor C, and the other is the peak energy converted from leakage inductance to C. Since the leakage inductance is very small, the peak current cannot be too large, so the energy is also very limited. Relatively speaking, only considering the DC energy consumed by R is enough. With the same parameters as above, the DC voltage on C is Vo+Ui/N=80V, and the resistance R is 47K, the energy consumption is 0.14W. Compared with 1.4W above, the "low-carbon" effect is extraordinary.diode

Let's talk about the characteristics of these two absorption circuits and other absorption circuits:

RC absorption: While absorbing the peak, it also absorbs the square wave energy output by the transformer. The absorption efficiency is low and the loss is large, but the circuit is simple and the absorption period is consistent with the switching frequency. It can be used in low standby power circuits;diode

RCD absorption: Suitable for all applications where RC absorbs leakage inductance peaks (including forward, reverse, full bridge, half bridge topologies, etc.), the absorption efficiency is higher than RC, but there is a situation where the energy stored in the capacitor (usually large) is constantly consumed, which is not suitable for use in low standby power circuits (including leakage inductance absorption of primary MOS transistors);diode

Let's discuss ZENER absorption again: it can be applied to primary MOS leakage inductance peak absorption, secondary rectifier voltage peak absorption, and can also be applied to low standby power circuits. It has the highest absorption efficiency and high cost, but ZENER voltage regulation parameters vary greatly and require careful design.diode