Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Current driver
Reexamination Certificate
1999-11-03
2001-05-22
Ton, My-Trang Nu (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Current driver
C327S424000
Reexamination Certificate
active
06236246
ABSTRACT:
BACKGROUND OF THE INVENTION
Write drivers for inductive write heads of the magnetic disc drive are employed to provide write current to the head. These inductive heads record data on the magnetic media by selective reversal of magnetic flux caused by a reversal of the direction of current through the write head winding. The write current is reversed by a command from an input signal representing data to be recorded. However, the current reversal generates voltage differences across the head during the reversal period, thereby requiring the voltage to recover to a nominal level to again achieve a steady-state flow of current in the opposite direction after the reversal. The voltage fluctuations cause delay in achieving steady-state current conditions, and also cause overshoot or “ringing” of the current waveform.
Numerous techniques have been employed to address the problem of overshoot, ringing and delays in reaching steady-state conditions. The present invention is directed to a voltage boost circuit that boosts the voltage at the nodes on opposite sides of the head, the boosting occurring in either positively or negatively, or both, to reduce delays in achieving steady-state current conditions and to reduce overshoot or ringing.
BRIEF SUMMARY OF THE INVENTION
A voltage boost circuit is provided for a write driver. The write driver has first and second nodes for connection to opposite sides of a write head winding. The voltage boost circuit includes a first and semiconductor devices, such as Schottky diodes, coupled to respective first and second nodes to conduct write current through respective first or second current switches of the write driver when a forward voltage across the respective first or second semiconductor device exceeds a design voltage. The first and second current switches are responsive to respective complementary first and second input signals to direct write current in opposite directions through the winding between the first and second nodes. First and second storage devices are connected to the respective first and second semiconductor devices, and first and second buffers are responsive to a first state of the respective first and second input signals to operate the respective first or second storage device to increase the forward voltage across the respective first or second semiconductor device.
In a preferred form of the voltage boost circuit, the first and second buffers are responsive to a second state of the respective first and second input signals to operate the respective first or second storage device to decrease the forward voltage across the respective first or second semiconductor device.
In an optional form of the invention, the write driver includes third and fourth current switches coupled to the first and second nodes to conduct write current through the write head winding. The voltage boost circuit additionally includes third and fourth semiconductor devices, such as Schottky diodes, coupled to the respective first and second nodes to conduct write current through the respective third or fourth current switch when a forward voltage across the respective third or fourth semiconductor device exceeds a second design voltage. Third and fourth storage devices are connected to respective third and fourth semiconductor device. The first buffer is responsive to the first state of the first input signal to operate the third storage device to decrease the forward voltage across the third semiconductor device, and the second buffer is responsive to the first state of the second input signal to operate the fourth storage device to decrease the forward voltage across the fourth semiconductor device.
In a preferred form of this optional version of the voltage boost circuit, the first and second buffers are responsive to the second state of the respective first and second input signals to operate the respective third or fourth storage device to increase the forward voltage across the respective third or fourth semiconductor device.
REFERENCES:
patent: 3731004 (1973-05-01), Cowpland et al.
patent: 3770986 (1973-11-01), Drehle
patent: 5751171 (1998-05-01), Ngo
patent: 5757215 (1998-05-01), Schuelke et al.
patent: 5894237 (1999-04-01), Brannon et al.
patent: 5990710 (1999-11-01), Ngo et al.
Leighton John D.
Ngo Tuan V.
Kinney & Lange , P.A.
Lucent Technologies - Inc.
Nu Ton My-Trang
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