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Current Sensing Resistors in an H Bridge Circuit

  1. Apr 5, 2009 #1
    I am using the UC3638 PWM chip to drive a motor. I was wondering if the current sensing resistors are required, and if someone could translate how they work? How are they used for peak current limit control and in their absence what happens?

    If more information is needed, its powered from a 12V 5A power source, using 2 complimentary half bridge mosfet chips, the Si4500DY.

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  2. jcsd
  3. Apr 8, 2009 #2


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    The current sensing just works via Ohm's Law, V = I*R

    In applications like this, you want to use a small resistor (usually less than an ohm, but I haven't read through the particular datasheet in great detail) because the higher your sensing voltage, the less voltage you have across your motor.

    You can often get away with not using the sense resistor (by replacing it with a wire / cable) but you don't get any current information (useful, for instance, in ensuring motors don't overheat or that a certain torque is applied).
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