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Browse Prior Art Database

Charge Controller for Power-On Plugging And Unplugging of Electronic Components

IP.com Disclosure Number: IPCOM000101413D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 3 page(s) / 112K

Publishing Venue

IBM

Related People

Kisacky, ET: AUTHOR [+4]

Abstract

During maintenance of electronic equipment, it is desirable to plug or unplug an electronic component while the system is powered up and operating. When voltage is first applied to a circuit card, an electrical transient is caused as the card capacitance charges up to the power supply voltage. The effect of this transient on the machine operation must be moderated to avoid system errors. In addition, provision may be required for application of multiple voltages in a specified order and perhaps initialization of the replaced part.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Charge Controller for Power-On Plugging And Unplugging of Electronic Components

       During maintenance of electronic equipment, it is
desirable to plug or unplug an electronic component while the system
is powered up and operating.  When voltage is first applied to a
circuit card, an electrical transient is caused as the card
capacitance charges up to the power supply voltage. The effect of
this transient on the machine operation must be moderated to avoid
system errors.  In addition, provision may be required for
application of multiple voltages in a specified order and perhaps
initialization of the replaced part.

      The disclosed design improves the art of the umbilical cord
approach by charging the card prior to plugging from the operating
power supply and does not apply power to the card until it is within
the chassis.  The design uses only passive electrical components for
the charging current controller and also includes a means to
discharge electrostatic charge generated during the
plugging/unplugging motion.

      The charge controller functional block diagram is shown in Fig.
1.  A schematic illustrating the connection between the card and
charge controller is shown in Fig. 2, and Fig. 3 is a simplified
equivalent circuit.  The two power supplies shown in Fig. 2 represent
the system operating power supplies, each providing a different
operating voltage.

      The isolation capacitor is selected to be a factor of ten or
more larger than the card capacitance.  Then in the approximation
that the card is charged entirely from the isolation capacitor, the
net voltage drop is about ten percent of the initial voltage.  Also
in this approximation the charging time constant is, to first order,
independent of the value of the isolation capacitor, the appropriate
capacitance element determining the charging time constant being the
card capacitance.

      The high frequency charging current is attenuated by the
ferrite devices, which do not saturate and lose their loss mechanisms
during the charging transient because the ferrite magnetization time
constant is much longer than the charging time constant.  Since these
ferrite devices do not introduce DC resistance in series with the
charging current, it is nece...