Buck Converter High-Side Switch

[Fish4Fun]

As a hobbyist I have had an interest in SMPS power supplies for quite some time, but have never gone past casual study of them. I understand the theory, but have difficulty with the actual implementation of things like a high-side switch mechanism for a P-Channel Mosfet.

My goal is to define a high-side switch control mechanism that will allow me to use a uController in a prototype circuit. I want to be able to use various inductors and Mosfets at different switching frequencies and duty cycles w/o designing a specific high-side switch control.

This is what I am thinking:

In simulation, it works well enough. @ 170Vdc the gate of Q3 varies between 170V and 155V. The Specs on the mosfet state that full turn-off occurs @ Vgs = -10V and Vgs can handle constant +/-20V and transient Vgs of +/-30V.

Q2 can be a fairly low voltage switch as most of the voltage is dropped by D3. The current through Q2 is fairly small, ~1.47mA. Obviously lower total resistance in the voltage divider formed by R1 & R6 will supply higher current, and thus a better switching waveform to the gate of Q3.

My question is, will the Zener/voltage divider form a viable way of switching a P-Channel mosfet? If not, is there a simple way of controlling the Gate of the P-Channel mosfet (Q3)?

Thanks in advance!

Fish

 

[Fish4Fun]

Things have come a long way since the last time I tried to solve this problem. It appears the best answer is something like this:

http://www.fairchildsemi.com/ds/FA%2FFAN73711.pdf

Which precludes needing to use a P-Channel mosfet altogether, very cool.

So, since I missed the "High Side Gate Driver IC Revolution", can anyone one recommend a particular High Side Gate Driver wrt simplicity and flexibility of design. (Again, my objective is to create a test platform where I can quickly change out switches, inductors and output filters to prototype various current/voltage regulated supplies.)

Thanks,

Fish