I am currently in the final stages of a project that aims to provide traction control for a small D.C motor. My motor is driven by a H-Bridge, into which i am feeding PWM to each Half-Bridge enable pin, with one PWM being the inverse of the other. So in other words when my duty cycle is 50% the motor will not move, and when duty cycle is 100% full voltage across motor. My problem occurs on the rising and falling edges of each PWM signal, my H-Bridge will be turning on one side at the same time the other half bridge is turning off, the switching times for each half bridge will overlap and cause shoot-through or short circuit. I have come up with a solution to this problem using two 555 monostables combined with some XOR and NOT gates however this is quite large, leaving more places for things to go worng, andding extra cost due to the fact i am doing this whole process twice for two individual motors. If anybody could recomend a better solution that would be great. Surely there must be a more efficient way of getting round this problem? Even a simple IC that i can purchase?

AdrianD

 

I am currently in the final stages of a project that aims to provide traction control for a small D.C motor. My motor is driven by a H-Bridge, into which i am feeding PWM to each Half-Bridge enable pin, with one PWM being the inverse of the other. So in other words when my duty cycle is 50% the motor will not move, and when duty cycle is 100% full voltage across motor. My problem occurs on the rising and falling edges of each PWM signal, my H-Bridge will be turning on one side at the same time the other half bridge is turning off, the switching times for each half bridge will overlap and cause shoot-through or short circuit. I have come up with a solution to this problem using two 555 monostables combined with some XOR and NOT gates however this is quite large, leaving more places for things to go worng, andding extra cost due to the fact i am doing this whole process twice for two individual motors. If anybody could recomend a better solution that would be great. Surely there must be a more efficient way of getting round this problem? Even a simple IC that i can purchase?

AdrianD

it would be helpful if you put a schematic

 

I'd use a PSoC microcontroller. You can get a miniprog from www.digikey.com for cheap. All you need to do is wire up (graphically) PWM blocks (8/16bit) and call them in assembly to start. You can read an analog input and directly write the value to the PWM compare register.

Steve