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Bipolar chopper
drivers are by far the most widely used drivers for
industrial applications. Although they are typically more
expensive to design, they offer high performance and high
efficiency. Bipolar chopper drivers use an extra set of
switching transistors to eliminate the need for two power
sources. Additionally, these drivers use a four transistor
bridge with recirculating diodes and a sense resistor that
maintains a feedback voltage proportional to the motor
current. Motor windings, using a bipolar chopper driver, are
energized to the full supply level by turning on one set
(top and bottom) of the switching transistors. The sense
resistor monitors the linear rise in current until the
required level is reached. At this point the top switch
opens and the current in the motor coil is maintained via
the bottom switch and the diode. Current "decay" (lose over
time) occurs until a preset position is reached and the
process starts over. This "chopping" effect of the supply is
what maintains the correct current voltage to the motor at
all times.
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