Discrete BJT FET gate driver has problems

[treez]

Hello,

The attached Buck converter (LED driver) has a P mosfet driven by a discrete BJT gate driver.

The transistor Q1 is being driven into saturation, but still manages to switch the PFET off quickly (the turn OFF gate voltage plateau is only 82ns).

How can this be?, why is BJT Q1 not taking ages to turn off?, ...after all it was saturated

Also, the NPN Q2 suffers a periodic reverse voltage of -9V on its Vbe. Will this be OK?, ..since its only a spike, and not a persistent reverse voltage of -9V on the Vbe.

Here is datasheet for MMBT3904 showing max allowable Vbe on MMBT3904 is -6V
https://www.fairchildsemi.com/ds/2N/2N3904.pdf

(All waveforms below)
Schematic; PFET gate voltage; Q2 Vbe

- - - Updated - - -

by the way , the LTspice simulation "Buck" is also here...

 

[godfreyl]

Also, the NPN Q2 suffers a periodic reverse voltage of -9V on its Vbe.

You can fix that by moving the 22R resistor like this:

 

[D.A.(Tony)Stewart]

Q1 storage times are 150nS @6mA at 25'C assuming IC/Ib=10. In your case Ic/Ib= 3. Perhaps that affects the saturation time.

How is your overall efficiency P-led/P-in ?