BRUSHLESS DC MOTOR CONTROLLER
FSP33035
The figure below shows a three phase, three step, half wave motor controller. This configuration is ideally suited for
automotive and other low voltage applications since there is only one power switch voltage drop in series with a
given stator winding. Current flow is unidirectional or half wave because only one end of each winding is switched.
Continuous braking with the typical half wave arrangement presents a motor overheating problem since stator
current is limited only by the winding resistance. This is due to the lack of upper power switch transistors, as in the
full wave circuit, used to disconnect the windings from the supply voltage VM. A unique solution is to provide
braking until the motor stops and then turn off the bottom drives. This can be accomplished by using the Fault
Output in conjunction with the Output Enable as an over current timer. Components RDLY and CDLY are selected to
give the motor sufficient time to stop before latching the Output Enable and the top drive AND gates low. When
enabling the motor, the brake switch is closed and the PNP transistor (along with resistors R1 and RDLY ) are used
to reset the latch by discharging CDLY. The stator flyback voltage is clamped by a single zener and three diodes.
Three Phase, Three Step, Half Wave Motor Controller
16/28
2007-3-16
FOSLINK [ FOSLINK SEMICONDUCTOR CO.,LTD ]
