Importance

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Abstract

A controller for regulating the current applied to the windings of a brushless DC motor by pulse width modulating transistors arranged in a six-switch bridge. Current feedback signals are obtained from sense resistors provided in the lower legs of the bridge circuit and are employed to generate a loop error signal. A bilateral arrangement of hysteresis comparator circuits monitors the current feedback signals and provides signals that disable the transistor switches when the current is sensed to be in excess of a safe level of operation for the transistors. The shutdown circuit continues its disablement of the transistors until the current is sensed to fall back within the designed range of control. To ensure smooth transition between regenerating and motoring modes, a circuit monitors both positive and negative excursions of the integrated error signal. When the error signal is sensed to exceed the operating range of the pulse width modulation circuitry, the sense of the motor excitation is reversed in order to produce the desired motor torque. An absolute value circuit enables the use of both positive and negative values of the error signal to control the production of pulses by the pulse width modulation circuit.

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First Claim