Appeal No. 1999-0260
Application 08/571,064
devices which have developed short circuits or otherwise consume
unexpected large amounts of power.
Appellants' primary embodiment (figure 1) provides a PC card
(60) connected to two separate voltages (Vcc and Vpp) through two
power lines (35 and 36) and PC card slot (50). These power lines
are each separately monitored by resistors (41 and 42) and
differential amplifiers (43 and 44). The outputs of the
amplifiers are supplied to a disjunctive circuit (OR-gate 39)
which outputs a logical sum of the two inputs as an over current
signal (OCS) to ON/OFF switch controllers (37 and 38). Each
controller operates upon a separate switch (31 and 32) so that
power to both power lines is terminated upon detection of an
over-current condition in either resistor (41 or 42).
In addition, the output of the disjunctive circuit is
forwarded to a register (23) and a driver (25). In response to a
high OCS signal that is accompanied by the over-current
detection, the driver is placed into a high impedance state and
the transmission of bus signals to the PC card is halted.
Independent claim 1 is reproduced as follows:
1. A power enabling mechanism, which controls supply of
operating power from an information processing apparatus to a
detachable input/output device, said mechanism comprising:
2
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