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Simplifying H-bridge design

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cadena:
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.


 

JagV12:
If you want a cheap and simple circuit, search the web for "arduino PWM H-bridge" and you'll find plenty of ready made circuits (dirt cheap L298N dual channel board is rated for 35V and 2A max, not that bad !)

But if you want to learn electronics, have a look at the (IRLZ44S and FQD11P06TM) datasheet and look what happens when Gate voltage ramps from 0V to 12V on the left (or right) branch of the bridge. If both transistors are conductive at the same time  :bullshit:, you're in trouble...

cadena:
Hi, thanks for your reply. I am trying to build the H-bridges using MOSFETS rather than ICs where I can't see what is going on and also trying to not spendore since I am nearly over budget. I am trying either to solve this circuit or find another one which uses N and P channel MOSFETS.

cadena:
I was thinking, could this be solved by writing down a delay in the arduino code ? If this could be solved in this manner, how long should the delay be ( I am using arduino uno PWM) ?

JagV12:
You can't use software delays here because the same optocoupler drives both top and bottom switches. If you just do a forward-reverse H bridge, you can use RC delays (+ diode) to create a Break before Make switching. But the slow Gate voltage change creates a slow Off-On transition => efficiency loss. Adding Schmitt Triggers is a solution.

But you're right, software delay is OK if you use 4 output pins instead of 2 and control each transistor individually (or 2 if you drive Forward (TopLeft-BottomRight) and Reverse (TopRight-BottomLeft) switches as a pair with the appropriate logic gates). Once again, search the web, there should be many nice solutions out there...

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