Pitney Bowes Inc.

Scott T Potter

Edilberto I Salazar

Sungwon R Moh

Frank D Ramirez

A circuit for controlling a current in a load, the circuit includes: structure for connecting the circuit to a source of power, the power source connecting structure including a power switch having off and on operating modes; structure for connecting the circuit to a supply of a pulse width modulated (PWM) control signal, the PWM supply connecting structure including an AND gate having first and second input structure and an output structure, one of the first and second input structures connected for receiving the PWM control signal, and the AND gate output structure connected to the power switch for operating the switch; structure for monitoring the current in the load, the monitoring structure including a differential amplifier, the differential amplifier having an instantaneous output voltage signal proportional to the load current when the power switch is in the on operating mode, structure for comparing a value derived from the instantaneous signal to a high reference voltage signal and a low reference voltage signal and providing a first comparison signal, structure for providing a peak reference voltage signal in response to the first comparison signal, structure for comparing the peak reference voltage signal and instantaneous output voltage signal and providing a second comparison signal; and structure for providing a signal corresponding to the second comparison signal to the other of the first and second input structures of the AND gate for operating the power switch in consideration of the comparison between the peak reference voltage signal and instantaneous output voltage signal.

Load current limiting circuit for PWM controlled brushless motor

An integrated circuit driver for a brushless motor having an encoder which includes a plurality of Hall-effect sensors operative for providing commutation information to a motor controller includes a commutation decoding section for decoding the commutation information from the Hall-effect sensors and an analog current limiter. The current limiter includes a circuit for dynamically switching the current limit values for current in the motor between a high current limit value and a low current limit value based on the average or RMS value of the motor winding current. The current limit values must be provided externally. A Hall-effect sensor quadrature encoder is provided on the integrated circuit and a selection switch allows for the selection of a quadrature output from an external optical encoder or the internal Hall-effect sensor encoder.

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Fairfield, CT, United States of America

Scott T Potter