Blanking Circuit for Switched Motor Control System
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
In a switched motor control system a transistor bridge switches current through a motor in either direction. Transitions of an analog input waveform are detected by a comparator to switch the bridge. Sensitivity to input noise is removed by a blanking circuit which blanks the response of the comparator after a good transition in either direction. The blanking circuit is not in series with the comparator which avoids additional phase delays, and equal mark/space operation is provided. Fig. 1 shows the position of the blanking circuit within a motor control loop. FETs T1 to T4 form a bridge around the motor. At any time either T1 and T4 or T2 and T3 can conduct to switch current in either direction through the motor. Amplifier A2 has a differential input from resistors RSENSE.