Peter F Scheller

US Patent:

54732387, Dec 5, 1995

Filed:

Oct 18, 1993

Appl. No.:

8/138315

Inventors:

Paul W. Latham - Lee NH
Peter K. Scheller - Rochester NH

Assignee:

Allegro Microsystems, Inc. - Worcester MA

International Classification:

H02P 540
H02P 602

US Classification:

318560

Abstract:

A disc drive circuit includes a pair of DC busses across which are directly connected a disc actuator power amplifier and a three phase spindle motor power amplifier which may be comprised of three circuit branches, each branch having two NMOS transistors connected in series with the junction therebetween connected to one of three spindle motor terminals. A transistor switch is connected between a DC supply source and the DC busses for disconnecting the busses from the voltage source only when the supply voltage drops below a nominal operating voltage range. In one embodiment a full wave diode rectifier is also directly connected across the pair of busses and further connected to the three motor terminals, whereby when the switch is open the back e. m. f. of the free spinning spindle motor energizes the actuator amplifier enabling parking of the actuator heads. In another embodiment the drain to channel regions of the six NMOS transistors are adapted to assume the role of a full wave rectifier.