05866998 is referenced by 21 patents and cites 4 patents.

A power-switched driver circuit for a disc drive that provides accurate back emf detection in PWM mode. In one embodiment, a power transistor is coupled between the low side drivers and ground. During the off time of a PWM cycle, all of the high side drivers are off and the current recirculates through two of the low side drivers. The power transistor is off. This disconnects the motor from ground and allows the voltage on the center tap of the motor to be about half of V.sub.cc, which allows the back emf of the motor to be detected during the off time using a conventional comparator as the back emf approaches a zero crossing. During the on time of a PWM cycle, the power transistor is on.

In an alternative embodiment, a power transistor is coupled between the high side drivers and V.sub.cc. During the off time of a PWM cycle, all of the low side drivers are turned off and the current recirculates through two of the high side drivers. The power transistor is off, disconnecting the motor from V.sub.cc and allowing the voltage on the center tap of the motor to be about half of V.sub.cc. This enables the back emf of the motor to be detected during the off time using a conventional comparator as the back emf approaches a zero crossing.

Title
Circuit for improving back emf detection in pulse width modulation mode
Application Number
8/957088
Publication Number
5866998
Application Date
October 24, 1997
Publication Date
February 2, 1999
Inventor
Paolo Menegoli
Milpitas
CA, US
Agent
Lisa K Jorgenson
Theodore E Galanthay
Assignee
STMicroelectronics
TX, US
IPC
H02K 23/00
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