这个同步整流控制器是如何工作的

各位大神 帮忙看一下 这个电路红色圆圈部分是根据什么选取的？ 红圈1里面（左下角）的电路频率是和65KHZ相近的，是怎么计算出来的，算了好久都没对，红圈2（右上角）的吸收电路怎么选值，依据是什么呢？现在打算做成1MHz,不知道怎么改动，请高手们指教小弟，第一次做好多不懂。

红圈1部分 手册上是这样说的 LLD circuit with components with value close to typical 65 kHz flybackapplication (adjust to used application is needed)。

Using a simple and cost effectivepeak detector implemented with a diode D1, resistors R1through R3 and capacitors C2 and C3, the load level can be sensed.

The SR MOSFET drainvoltage drops to ~ 0 V when ISEC current is flowing. Whenthe SR MOSFET is conducting the capacitor C2 charges-up,causing the difference between the LLD pin and VCC pin toincrease, and drop the LLD pin voltage. As the loaddecreases the secondary side currents flows for a shorter ashorter time. C2 has less time to accumulate charge and thevoltage on the C2 decreases, because it is discharged by R2and R3. This smaller voltage on C2 will cause the LLD pinvoltage to increase towards VCC and the difference betweenLLD and VCC will go to zero. The output voltage thendirectly reduces DRV clamp voltage down from itsmaximum level. The DRV is then fully disabled when ICenters disable mode. The IC exits from disable mode whendifference between LLD voltage and VCC increases overVLLD_REC. Resistors R2 and R3 are also used for voltagelevel adjustment and with capacitor C3 form low pass filterthat filters relatively high speed ripple at C2. This low passfilter also reduces speed of state change of the SR controllerfrom normal to disable mode or reversely. Time constantshould be higher than feedback loop time constant to keepwhole system stable.

说说您的高见，给小弟指点指点，谢谢！