Patent ID: 6054823
Filing Date: 2000-04-25
Classification: F04D,H02H

Abstract:
An apparatus for sensing the rotation of a brushless DC fan motor, the apparatus comprising:a fan;a sense/driver circuit coupled to the fan to receive a sense input signal, the sense input signal including a fluctuating electrical effect caused by fan commutation events, the sense/driver circuit processing the sense input signal to generate a sense output signal from the electrical effect, the sense output signal being indicative of fan operation, the sense/driver circuit including an integrated circuit, the integrated circuit includinga sense input pin, the sense input pin being coupled to receive the sense input signal;a ground return pin, the ground return pin being coupled to a ground reference potential;a driver circuit, the driver circuit opening and closing a circuit to connect and disconnect power to the fan, the driver circuit including a control terminal and first and second current handling terminals, the first current handling terminal being coupled to the sense input pin, the second current handling terminal being coupled to provide a ground return path via the ground return pin;an integrated filter portion, the integrated filter portion including a filter input coupled to one of the first and second current handling terminals of the driver circuit, the integrated filter portion including a filter output for providing a filter output signal;a filter pin coupled to the integrated filter portion; anda level detecting circuit, the level detecting circuit having an input coupled to receive the filter output signal, the level detecting circuit generating the sense output signal from the filter output signal; anda capacitance, the capacitance coupled to the filter pin, the integrated filter portion and the capacitance comprising a filter, the filter deriving the filter output signal responsive to receiving a signal at the sense input pin, the filter output signal being indicative of the fan commutation events.