Abstract:
A completely passive and self-contained solid-state circuit interrupter for removing DC power while mating and unmating connectors is integrated into a connector housing. An electronic mechanism is employed to de-energize the power contacts while the mating connectors are more than a predetermined distance apart.

Description:
FIELD OF THE INVENTION 
     The present invention relates to interconnection power cables. More particularly, the present invention relates to the passive connection and disconnection of a DC (direct current) power cable. 
     BACKGROUND OF THE INVENTION 
     Complex computer systems employ numerous workstations connected to numerous peripheral computer devices. With the improvement in technology, it is common for one or more of these computing devices to require configuration changes and/or upgrades. Such changes are made to the computer device with the DC (direct current) power disconnected. In order to keep as much of the computer system operational, service personnel typically disconnect and connect the power cable of the particular computing device. This cable includes the DC power for the computer device being serviced. DC power is left on so that DC power is applied to the rest of the system. When an electronic device such as a peripheral is connected to an active computer bus, the power drawn immediately upon insertion or removal of DC power may be sufficient to cause transient voltages to appear on the bus resulting in component damage and/or bus data error. This problem is particularly acute in parallel systems sharing a common bus wherein a transient on one peripheral can cause data errors in all machines connected to the bus. Further, exposed pins can short the DC power bringing down the other bus connected devices or, worse, causing loss of data. Additionally, power on the connector with exposed pins is hazardous to personnel during connection/removal of the DC power. 
     The DC power as well as other computer signals are often supplied to each computer device through a plug and connector. These are commonly used in computer devices and well known to those in the art. These connectors have a plurality of male pins that mate with a corresponding female receptacles pins. Both the male and female ends may be adapted for termination of a wire harness. This arrangement of a connector plug/receptacle on the end of a wire harness is called a “pendant connector.” A connector with power applied is called a “hot-plug.” It is analogous to the hot insertion and hot removal of computing devices on a powered up host computer bus. 
     Typically, power removal is accomplished through electromechanical circuit breakers wherein AC (alternating current) power is removed to large portions of equipment. This requires field maintenance personnel to know where these circuit breakers are located and to remember to disconnect the AC power. Even if this is accomplished, the circuit breakers often are used to power large areas including lighting circuits as well as the receptacle outlets powering the computing device of interest. 
     It is less disruptive to personnel using the computer equipment to disconnect low voltage DC prior to unmating of equipment connectors powering a specific computing device. In this manner the rest of the computer network remains functional during the maintenance or servicing of a particular computer device. However, the disconnection of an energized power cable poses a safety hazard for personnel and, therefore, requires extreme caution. Further, exposed power contacts may contact objects creating shorts to ground or injecting unwanted voltage transients onto the power lines. This creates a risk of loss of data and loss of compute capability. 
     A number of devices have been disclosed for computer bus isolation to minimize bus transients during the hot removal and hot insertion of circuit boards, peripherals, etc., e.g., such devices are described in U.S. Pat. Nos. 5,586,271 and 5,210,855. These devices are bulky and do not assure power removal and application without operator intervention. 
     Further, U.S. Pat. No. 2,573,920, entitled Coupled Actuated Magnetic Switch, describes a plug with an internal magnet arranged to remove AC power from a receptacle outlet containing a magnetic switch when the plug is removed therefrom. This arrangement removes high voltage AC power to prevent short circuits and hazards to personnel. It does not address removal of DC power from a pendant connector. Further, no provision is made for electronic circuitry that can be adapted to apply/remove the power in various ways such as buffering to limit inrush current or bus transients. 
     Other approaches that passively protect circuitry during hot connect/disconnect of connectors have required reconfiguration of the connector pins, additional circuitry external to the connector, and/or additional wires in the connector harness. One approach requires reconfiguration of the connector to have pins of different lengths. This entails creating specialized connectors with different configurations for different connector applications. Another implementation employs a mechanical interlock switch for a rack/tray assembly whereby inrush currents are managed whenever plugging and unplugging the racks/trays. This switching method is not adapted to connectors on pendant cords nor is a proximity switch employed. 
     SUMMARY OF THE INVENTION 
     The present invention employs a proximity switch to determine when mating connectors are in close proximity to each other. Proximity switches are “passive” in that they rely on various types of physical phenomena such as magnetism or capacitive discharge rather than actuation by an operator. The present invention thereby provides a passive mechanism that is contained within a connector housing; requires no additional external wiring; and removes electrical power prior to connector unmating and applies power only after connection during connector mating/unmating. An LED (light emitting diode) or other indicator may be incorporated to provide visual indication of voltage condition. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The FIGURE is an exploded view drawing of an exemplary implementation of the present invention. 
    
    
     DETAILED DESCRIPTION 
     Referring to the FIGURE, an active mating connector arrangement of the present invention is generally shown at  10 . Connector arrangement  10  includes mating connector assemblies  12  and  14 . Connection assembly  12  has a connector  16  supported in a housing  18  formed by upper and lower housing portions  20 ,  22 . Connector  16  carries a plurality of terminals which have conductors of a cable  24  terminated thereto. Connector  16  may also be a power connector on a device to which a power cable is connected. Connector assembly  14  has a connector  26  supported in a housing  28  formed by upper and lower housing portions  30 ,  32 . Connector  26  also carries a plurality of terminals. Connectors  16  and  26  are mating connectors whereby one of these connectors carries male terminals (pins) while the other connector carries corresponding female terminals (sockets). Connectors  16  and  26  are shown as power D-shell connectors, although other connector types are contemplated by the present invention, such as commonly used for connection of DC power. One of the unused terminal locations of connector  16  has a magnetic member  34  located therein. One of the terminal locations of connector  26  has a member  36  installed therein, this location corresponding to the aforementioned terminal location on connector  16 . Members  34  and  36  are part of a proximity switch. Proximity switches are well known and are commercially available. These switches are “passive” in that they rely on various types of physical phenomena such as magnetism or capacitive discharge rather than actuation by an operator. 
     A power switch (MOSFET)  38  is mounted and electrically connected to a circuit card assembly  40  mounted within housing  28 . The power switch  38  is located to receive (communication with) the proximity switch. Conductors of a cable  42  which carry DC power are electrically connected to (terminated at) circuit card assembly  40 . Circuit card assembly  40  is secured in housing  28  by any known means (not shown) including being held in place by receiving slots in the housing, secured to standoffs or post with threaded screws or even potted into the housing. A heat sink  44  may be mounted to circuit card assembly  40  in thermal contact to help dissipate heat. Particularly in applications where the circuitry of the circuit card assembly  40  may be required to transfer large amounts of power. Under these circumstances considerable heat may be generated making heat sink  44  necessary. 
     When connectors  16  and  26  are mated (connected) the proximity switch actuates (i.e., members  34  and  36  sufficiently couple magnetically) causing actuation of the power switch  38 . Such magnetic proximity switches have an internal hinged electrical contact (not shown) and stationary electrical contact (not shown). In the presence of a magnetic field the hinged contact is caused to move and make electrical contact with the stationary contact hence actuating the magnetic proximity switch. The proximity switch is set to actuate (thus actuating power switch  38 ) when the mating connectors are close enough to assure that the mating terminals of connectors  16  and  26  are sufficiently engaged for a reliable power connection. The distance so required is called the “engagement gap”. The engagement gap is a function of the particular connector chosen, however, this gap is typically of the order of 0.375 in. (8.63 mm). In response to actuation of the power switch  38 , circuitry of the circuit card assembly  40  is arranged to connect the DC power from the cable  42  to the terminals of connector  26  (through the power switch), such being readily apparent to one skilled in the art. DC power is thus enabled to flow from the (input) cable  42  through the circuit card assembly  42  to the terminals of connector plug  26  to terminals of connector  16  and to (output) cable  24 . Conversely, the proximity switch is unactuated when connectors  16  and  26  are disengaged (disconnected) a distance equal to or greater than the engagement gap. Then power switch  38  interrupts the power connection. 
     An indicator (e.g., a light emitting diode (LED))  46  is electrically mounted on the circuit card assembly  40  and is visible through an opening  48  in housing  28 . Circuitry of the circuit card assembly  40  is configured to cause the indicator  46  to illuminate when the DC power is enabled to the terminals of connector  26  thereby providing a technician with a visual indication when the connector is mated (connected) and power is applied. Power for the circuitry of the circuit card assembly  40  is sourced from cable  42 , or may be provided by any other suitable means, such as a battery. 
     The present invention thereby provides a passive mechanism that is contained within a connector housing; requires no additional external wiring, and removes electrical power prior to connector unmating and applies power only after connection during connector mating/unmating. Another advantage of the present invention is the ability for field retrofit. The actuating pin can easily be installed in the field. At that time or a later time the active connector plug/harness assembly can be replaced as one piece without the need to disassemble and reconfigure the connector plug in the field. 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.