Battery Charger Circuit

[datta]

Hi,

Please find the application circuit of BQ24401. The IC controls the switch of a buck converter (current control mode).

In this i am not able to understand the buck stage. To be precise , i am not able to understand the role of transistor Q2 , diode D5 and capacitor C9. Also , they have put a hysteretic controller to add hysteresis to the current sense signal (Capacitor C7). Please help me. Thanks in advance

 

[ronv]

The circuit is there to speed up the turn off of the main transistor by shorting the base to emmiter for a brief period.

 

[datta]

Thanks ronv