Buck Boost Converter using 2 Mosfets - Protection Suggestions

Thread Starter


Joined May 17, 2008
Please propose some real world protection for this circuit. I never had any experience with this.
Maybe flywheel diodes or extra coils, extra capacitors... i don't know.

Simulation is ok and functioning using NI Multisim. I will go on breadboard now.

Basic Topology on attachment - Buck Boost using 2 N mosfets on low side switch.
Voltages are below 30V DC, with output target of 15V.
So buck operation above 16V - Boost operation below 14V.

Q1 used for buck operation, while Q2 is off - low side switching topology
Q2 used for boost operation, while Q1 is on.
Referencing - feedback - output - will be on C2
Control - feedback reading - PWM on mosfets from Arduino (31Khz PWM Mod)

Mosfet gating on attachment.
33 ohm on gate and 150ohm for gate discharge - seems ok for 31Khz (tested already)
Added Zener 12V to protect the gate from overvoltage (designed to gate control with 10V as mosfet specs)
Extra diode in parallel.

Microcontroller signal using NPN / PNP amplification. How this is called?? I test it and is working.
Output of 2907 going to mosfet gate.

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