Abstract: A current magnitude sensing circuit for detecting a malfunction of a DC brushless fan. The current magnitude sensing circuit detects drops in the current magnitude in windings of a fan motor. Depending on the frequency of the current drops in the fan current, the current magnitude sensing circuit outputs either a high or a low voltage signal. The current magnitude sensing circuit operates by charging a capacitor beyond a certain voltage and thereby providing a high fan fail output signal when a fan is spinning too slowly for proper cooling of a device. Another capacitor is charged at a different time constant for setting the fan fail output of the current magnitude circuit low for indicating that the fan is spinning sufficiently fast.
Abstract: A method of updating characters within a multiplexed display used for displaying events including dynamic events which occur at a relatively faster rate. The display characters representing dynamic events are refreshed at a higher refresh frequency and more frequently during each display cycle. A plurality of display drivers including at least one grid driver controls the update and enablement of characters within the multiplexed display.
Type:
Grant
Filed:
August 16, 1996
Date of Patent:
September 14, 1999
Assignee:
Core Engineering, Inc.
Inventors:
Steven J. McKinney, Frank R. Aiello, Jr.
Abstract: A surge suppression circuit for gradually charging a capacitance of a device being hot plugged into a system, such as a disk drive being hot plugged into a RAID system. Without reliance on a permanently turned-on series element, such as a pass transistor, the surge suppression circuit uses a trigger circuit in combination with either a current limiting circuit or a slew rate control circuit. The current limiting circuit relies on a current sensing resistor in combination with a transistor that turns on when a voltage reaches a certain level across the current sensing resistor. The slew rate control circuit relies on a feedback mechanism that includes a capacitor and a resistor for maintaining a substantially constant rate of charging the capacitance of the device being hot plugged.