BACK EMF SENSING INTERFACE CIRCUIT

A back EMF signal from PWM driven motor is passed through an attenuation circuit. The attenuation circuit has a first mode of operation and a second mode of operation. The first mode of operation, used to sample a higher voltage back EMF signal during PWM on-time, applies the back EMF signal to a re...

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1. Verfasser: NOLAN DENNIS C
Format: Patent
Sprache:eng
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Zusammenfassung:A back EMF signal from PWM driven motor is passed through an attenuation circuit. The attenuation circuit has a first mode of operation and a second mode of operation. The first mode of operation, used to sample a higher voltage back EMF signal during PWM on-time, applies the back EMF signal to a resistive divider formed of a first resistor and second resistor connected in series. The second mode of operation, used to sample a lower voltage back EMF signal during PWM off-time, applies the back EMF signal to a circuit comprised of a transistor conduction path in series with the second resistor. A control signal, responsive PWM on-time and off-time state, controls switching between the first and second modes.