Re: free wheeling diode
HINDI said:
Hi
i am using msr860 as a free wheeling diode across the h- bridge mosfets for both the high and the low but after a short while of operation it fails and goes cocked and then shorted "1 minute ".
it was noted that the -ve portions due to the back emf of the voltage signal had been removed after adding the freewheeling diodes but still there is a high voltage spikes on the riesing edges of the switching signal .
where the h- bridge is 24VDC 15 amp , and 20khz .
i don't know what may cause although it has a sutable ratings for may load .
so , what may cause this problem ?
and how to remove this rising edge spikes ?
salam
hindi
You have parasitic inductace on wrong place in high frequency domain, possible in conductor between components... - and component itself...
if you have ringing and spike in ns-time domain - you handle in really world frequency in many MHz on your circurit - and need thinking RF...
in many time not easy to point out exact place of inductance
ie distributed on long cords in wide area loop and depend of
layout and cords orientation.
You need thinking with HF and RF eyes and make fast shifting current
on a small short and closed loop as possibly.
---
most common, scanty, methode to fix this problem (after design...) is a slow down fast rising edges with capacitance and RC-network on rigth place - and also freewheel diodes.
this soloution called 'snubber network' and possible to find lot of information her in EDAboard if seaching with word 'snubber', and also on google...
you need understud 'why' - to make best possible solution on your circurit...