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Simplifying H-bridge

Thread starter #1
Hi everyone,

I am currently trying to build a PWM H-bridge, it has a power line of 12 V and the arduino uno provides the PWM. The MOSFETS I have are: IRLZ44S (N-channel) and FQD11P06TM (P-channel). Basically, the p-type MOSFETS go in the upper side of the circuit and the n-channel go at the bottom. I would be building 6 of these circuits to run 6 motors in an ROV. At the moment I am using this circuit (see image below) but I have been told that it might have problems due to problems of straight through currents which could burn the MOSFETS so I would have to add some capacitors. I honestly don't know which resistor values I should use and where to place the capacitors (or their values). Any help will be appreciated. I am more than welcome to accept a different H-bridge circuit which is simpler than the other one as it uses BJTs and, ideally, I would only like to use a simple circuit with only 4 transistors (the MOSFETS). Thank you for your support.
 

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MikeMl

Well-Known Member
Most Helpful Member
#2
Horrible h-bridge. The way to guarantee no shoot-through is to use four port pins per bridge, and drive each FET gate separately. They used to make driver chips which took care of sequencing and delays of the gate drives to prevent shoot-through...
 
Thread starter #3
Hi, thank you for your reply. If it is possible, could you post a schematic of the circuit you are talking about so that I can have an idea ?
 
Thread starter #5
Hi, thanks for the link but I already know what PWM is. I was thinking if, perhaps, introducing a delay in my arduino code could get me away with this. However, how big should the delay be (I am using arduino uno PWM) ?
 
#6
Don't knpw if this helps but if you search eBay for "H bridge module" there are plently to choose from...I've used one in a project and it saved me a pile of work.
 
Thread starter #7
Hi, thank you all for your replies but I still do not know how to fix this circuit. Please if someone knows a better (and simpler) H-bridge than this one would you posting it, please ? Or at least tell me exactly how to fix this one ? I am still learning how to design circuits and I can't use an IC H-bridge. Please any help would very much appreciated.
 

dknguyen

Well-Known Member
Most Helpful Member
#8
Modify the circuit so the Arduino has individual control of each transistor rather than controlling pairs of transistors. Then you can delay the timings to prevent shoot-through. You have no control when one transistor turns on and another turns off if you you control pairs of transistors with the same signal.

Normal deadtime delays are some microseconds (I'd go with 10 or tens of microseconds if you don't know). How short you can get away with depends on how quickly your transistors turn on and off though which is dependent on how hard you drive the MOSFET gates.
 

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