Susie Maestre

user Electronics Engineer

city Innovuze Solutions Inc.

  • PWM Motor Controller

  • Created: Oct 28, 2015

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The reference design as shown is a motor controller that uses Pulse Width modulation (PWM). The use of PWM for motor control is advantageous compared to other methods in that power loss in the switching because of the use of transistor. As a result,the switching transistor has a much reduced power dissipation giving it a linear type of control which results in better speed stability.

This design consists of quad comparators, transistors and few discrete components. The first quad comparator amplifier (U1) is a low voltage cut-off circuit that prevents the circuit from working if the voltage gets low enough, to prevent damage to the batteries. The second section with the second amplifier (U2) is a current monitor which cuts off the controller if there's a short or too much current being drawn. It measures the difference across the resistors to check the current. The circuitry consists of LM339N (U3) and some resistors form a relaxation oscillator. This circuitry is a clock generator that produces 12.8kHz triangular wave. The amplifier (U4) is the pulse width modulator and produces a square wave from the output of U3 and the throttle voltage. It then feeds into Q3 and Q4 transistors which drive the MOSFETs.

This design utilizes AH1815 from Diodes Incorporated. It is an ultra-low-sensitivity, micropower, omnipolar Hall effect switch IC designed for portable and battery-powered consumer equipment, home appliances, and industrial applications.It has been optimized to operate over the supply range of 2.5V to 5.5V and uses a micropower sleep function to give an average supply current of only 8μA. In this design, it is used as the throttle.



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