problem with high current tec driver

[robmcw]

I am trying to design a TEC driver 15V 15A using a full h-bridge. Rather than using a high side driver IC I chose to use two PFETs and two NFETs.

I am switching (50KHz)the supply using the NFET. I noticed using a simple RC snubber is not removing the first high spike although is removing the resonance.

If I follow snubber suggestions, the Csnubber should be x2 - x4 my FET output capacitance but this does not seem to be enough to fully dampen the resonance. Using a much larger value dumps all the energy into my Rsnubber.

I've made various attempts to clamp the spike (below the max FET voltage) but all seem to get too hot.

Anyone been down this path before? or any tips? I am sure I am missing some basic part to the design.

I have attached my schematic (one half of the h-bridge)

Thanks

 

[MacGyverS2000]

Is there any particular reason you chose to go with something other than the high-side driver?

Dan - Owner

http://www.Hi-TecDesigns.com

 

[electricuwe]

Yes, you are missing some basic part to the design.

Provide a freewheeling path into which the current driven by the inductance can commutate when you turn off the NFET.

 

[OperaHouse]

You could try a diode into a capacitor with parallel resistor to limit the peak. Problem it is doing what it is supposed to do, be a boost converter. Just what is a TEC.

 

[VEBill]

I assume TEC is Thermal Electric Cooler (a Peltier device).