Can we put 24V zener diodes between drain and source of the MOSFETs in an H-Bridge?

Thread Starter

aaditpj

Joined Jul 3, 2014
7
Can we put 24V zener diodes between drain and source of the MOSFETs in an H-Bridge so that the max voltage given to the Motor coil is between 0 and 24V(assuming we are using 24V supply). Thus we can prevent the high voltage spikes caused due to the oscillation created by the RLC components of the circuit. Thus protecting the MOSFETs from high voltage spikes.
 

crutschow

Joined Mar 14, 2008
23,474
In a MOSFET H-bridge, the substrate diodes usually protect the MOSFETS from the spike voltages of an inductive load.
If you drawn the substrate diodes on the schematic you will see how that works.
 

Thread Starter

aaditpj

Joined Jul 3, 2014
7
In a MOSFET H-bridge, the substrate diodes usually protect the MOSFETS from the spike voltages of an inductive load.
If you drawn the substrate diodes on the schematic you will see how that works.
I saw that but when I do the simulation on multisim at 28kHz switching frequency the voltage spikes go from -60V to 60V.
 

Bordodynov

Joined May 20, 2015
2,416
You observe voltage surges due to parasitic inductances (in some models of transistors they are taken into account). Conventional zener diodes can be inertial. Avalanche breakdown can occur with a delay of ~ 300ns (Spice models do not reflect this). Use special restrictive diodes. For example Transils.
 

crutschow

Joined Mar 14, 2008
23,474
You could try a series RC damping circuit across each MOSFET to suppress the spikes.
Start with something like 0.1μF and 1k ohms.
 
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