By continuing to use this site, you are consenting to our use of cookies. I even wait to the end of a duty cycle before enabling the output drivers. For a better experience, please enable JavaScript in your browser before proceeding. On the subject of clamping diodes: Welcome to our site! Where I have had trouble is with a reversal pumping up the supply.

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The get diode is in the wrong direction to clamp the motor voltage. But you also have to study the driver chip outputs to see if any resistance will help at all during power up and power down. Perhaps you need a better startup sequence. My advise to you In theory, one could use the Mosfet’s internal body diode.

Micrel MIC4424CN FET Driver

Hi, A lot of things could have happened. If they have a little internal resistance though that helps too. Small motor circuits usually can get away with this. I guess the obvious is to add the correct pullup and pulldown resistors to both gate driver input and gate.

A fuse isnt a fwt idea but sometimes they are not fast enough. The PIC outputs are in the high impedance state while configuring the PWM module and the output drivers are enabled afterwards. The resistors would be there for protection against non recurring cross conduction. I even wait to the end of a duty cycle before enabling the output drivers.


Deadtime is the very short period one must have between the time a Mosfet is turned off and the time the opposite Mosfet is turned on. How do I connect additional clamping diodes to a full bridge?

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I was running the unloaded motor at a frequency and would just change it in my code, so I disconnected the circuit from Vin, did the quick change in code, recompiled, reprogrammed the PIC and connected the Vin again, this took around seconds. Futterama Member Feb 7, When building custom H bridges I always add some logic to prevent such situations happening i. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.

Forums New posts Search forums. This protection mechanism is best implemented at the driver IC-Mosfet’s gate interface. You can do this at startup and while operating normally. But these seem pretty fast. I have had the circuit working just fine and my code seems to work like it should, I could run the motor at different duty cycles and different frequencies.

That would help prevent blowout from false turn on no matter how it occurred power up, power down, bad dead time setting, any false signal.

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In the end, it will be far cheaper and easier than replacing transistors and ICs. I think the first thing to do is to add a resistor to Vin fft the short circuit current is limited, I actually looked for a 10A fuse yesterday, the fuse would be easier to replace than the MOSFETs and drivers, frt I’m running low on replacements. In practice, with the current levels you are working with, it may be better if an external diode conducts that current. In other words, is the time in which both Mosfets are completely off between transitions.


You can always “deadbug” a resistor across G-S. Click here to register now.

You want to make sure all the transistors are off before anything else, and while the PIC comes up to cet. The body diode will clamp it. I supose you could just divide the 12 volts down, but that will slow it down a bit so you would need to be careful on reversals.

Usually the power supply has enough capacitance to absorb the spike. You can leave the resistors in there if it doesnt bother the motor top speed too much and they are properly sized vet take the power.

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