WO1993015538A1

WO1993015538A1 - Power switch module

Info

Publication number: WO1993015538A1
Application number: PCT/US1993/001050
Authority: WO
Inventors: Michael A. Curran; Robert Valentine
Original assignee: Micro Industries
Priority date: 1992-02-03
Filing date: 1993-02-03
Publication date: 1993-08-05

Abstract

A power switch module with LED failure lamps for use with live board insertion techniques for computer systems. The power switch module may be a MOSFET in conjunction with a printed circuit board to be mounted on a fin shaped body.

Description

POWER SWITCH MODULE

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention relates generally to the insertion and the removal of a circuit device into a bus network, and more particularly, but not exclusively, to the insertion and removal of computer modules from a system which is under power.

Computers are becoming an ever increasing part of modern society. There have already been numerous examples where major disruption has occurred when a computer system has failed. Nonstop computer operation is already a requirement for many banks, hospitals, airlines, military applications, and communication systems. Up to now the solution to preventing disruption when a computer system fails is to provide a redundant system in conjunction with a primary system to go into operation when the primary system fails. This requires using two or more independent computer systems linked together. When one fails the other is ready to take its place.

Redundancy is one way of solving the failure problem and there are currently numerous commercial applications of this approach. However, there are drawbacks such as the expense (could be several hundred thousand dollars), the technical complexity of setting up such a system, and adverse effects on the speed of operation when redundant systems are connected. Examples of reasons for some computer system failures are such things as earthquakes, fires, power disruptions, and communication network failures.

Sometimes only one board or module mounted on a computer backplane may fail while the others remain functional. A computer module may also be replaced simply to change the programming function of the computer system. Coventional computer systems provide power for the boards in the system through connectors in a backplane. The backplane not only provides power to each board but it also provides the signals used to communicate between boards. In the past, in order to insert or remove boards from a system, it was necessary to turn off the main power to the system. In large system configurations or critical real time applications, it is not always possible to shut down a system to add or replace boards. This has resulted in the development of complex redundant systems as described above which allow the user to switch from one system to another to facilitate the upgrade or repair of equipment. The need for equipment that can be easily serviced and maintained without shutting down the entire system is becoming critical. The present invention facilitates board insertion and removal without shutting down system power. The present invention is accomplished by: switching of power to the board when it is inserted or removed; and, controlling the communications between boards as the power to the board is turned on and off. To control the power to the board it is necessary to switch all power connection either on or off when there are no board to board communications occurring. To accomplish this a controller with a terminal interface will provide the user with the ability to notify the system that a board is to be either inserted or removed and to identify the location. The controller will use a bus master priority scheme to assume control of the board-to-board communication. Once the controller has secured communications control, it will provide a signal to either turn on or off the power to the appropriate board location and allow board-to-board communications to proceed.

Each family of computer systems typically have a unique definition of the connector associated with a board location in the system. To implement the live insertion feature, the computer system must support multimaster communications capability. Therefore, the present invention is capable of being specifically designed for each family of computers. If one node on the backplane fails, it is usually possible for the remainder of the system to continue functioning in a diminished capacity. Bus traffic can be rerouted to another available server, pending replacement of the faulty module. The present invention enables live insertion (i.e.- while the power remains on) of faulty boards to be replaced. Downtime will be minimal and users of the system which are currently logged on to the system will be allowed to continue their work without significant disruption. The live insertion feature is implemented through an intelligent slot controller module on the backplane. This circuitry is capable of detecting changes in configuration, safely controlling power, and independently resetting a newly-inserted board. The present live insertion technique is compatible with the firmware which exists on most bus boards. The interconnect subsystem remains unchanged, and boards which implement the bus system architecture will function correctly in a special live insertion backplane. Applicant hereby incorporates by reference its other U.S. patent application entitled "Live Insertion of Computer Modules" filed on February 3, 1992.

The present invention of a live insertion power switch module is designed to provide power for an individual board in a computer system and to allow the power to be turned on or off without impacting the power provided to any other board in the system. The three approaches in use today to removing computer boards from systems include: turning off the power to all of the boards in the system; leaving power on to the board and removing it live; and, building two identical systems and when a board fails in one system switching the operations to the other system and turning off the power to the system with the failed board to allow for replacement. The first approach can be extremely time consuming and in many applications it is not practical to shut down the operation of the system simply to replace one board. The second approach can potentially damage the board if the board connections are not all broken simultaneously. This approach can disrupt board-to-board communications by causing power supply glitches which trigger false logic signals. The third approach addresses the board-to-board communications problem, but requires a significant amount of both hardware and software to insure that the transition can occur smoothly. The live insertion power switch module provides a method of isolating power to each board location in the system. The logic input also allows a controller or another board in the system to determine when it is safe to turn power on or off to minimize any disruption to board-to-board communications. Since it is possible to deal with boards on an individual basis, it is not necessary to maintain the level of operations software required to switch from one system to another.

The live insertion power switch module of the present invention is applicable in computer systems where more than one boar is required, and it is critical to maintain the operation of the system on a continuous basis. These requirements are typical of process control applications, telecommunications systems, defense and aerospace applications, industrial automation systems, and translation processing systems (credit cards, airline reservations, etc.). In a preferred embodiment of the present invention LED's may be mounted next to the connectors to indicate that power has either been turned on or turned off. This is an important feature to indicate whether the power switch module of the present invention has failed.

The foregoing and other objects and advantages will become more apparent when viewed in light of the accompanying drawings and following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of one embodiment of the switch module of the present invention for controlling one slot in which a board is plugged in;

FIG. 2 is a schematic view of the module of FIG. 1 for controlling a second slot;

FIG. 3 is a side elevation view of the switch module extrusion of the present invention;

FIG. 4 is a rear view of the switch module assembly of the present invention; FIG. 5 is a side view of the module of FIG. 4;

FIG. 6 is a view of the pin connectors on the module of the present invention;

FIG. 7 is a view of the solder side of a circuit board;

FIG. 8 is a section view of the circuit board of FIG. 7;

FIG. 9 is a plan view of a backplane assembly of FIG. 9; and FIG. 11 is a plan view of a backplane assembly with LED's to indicate switch module failure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT(S)

The live insertion power switch module of the present invention consists of a custom aluminum extrusion as shown in FIG. 3, discrete power MOSFETs for high current switch requirements and a printed circuit board (PCB) assembly that provides the components necessary to switch the voltage sources to the board (see FIG's. 1 and 2). The printed circuit board assembly also provides the isolation necessary to decouple the power source from all other boards in the system. The module is assembled by bolting the high current discrete MOSFET devices to the side opposite the fins on the aluminum extrusion (as shown in FIG 5) with their leads bent perpendicular to the surface (as shown in FIG 6). The PCB assembly mounts to the MOSFET leads and provides all of the connections necessary for the input voltages, the output voltages, and the logic input. Once the MOSFETs are soldered to the PCB assembly (shown in FIG's 7 and 8), the unit (as shown in FIG. 4) is placed in a mold and filled with thermally conductive epoxy to evenly distribute heat throughout the module during normal operation.

The power switch module receives a logic signal from a remote controller to indicate when it is possible to switch power on or off to the board controlled by the module. Upon transition from a logic high (1) to a logic low (0), all of the supply voltages associated with the board are turned on and remain on as long as the logic low (0) signal is present. For transitions from a logic low (0) to a logic high (1), all of the supply voltages associated with the board are turned off and remain off as long as a logic high (1) signal is present. All voltages required by the board may be supplied by the module and switched on or off simultaneously by the logic signal. The module provides a method of isolating power to each board location in the system. The logic input also allows a controller or another board in the system to determine when it is safe to turn power on or off to minimize any disruption to board-to-board communications. Since it is possible to deal with boards on an individual basis, it is not necessary to maintain the level of operations software required to switch from one system to another. The boards are mounted in slots on a backplane (as shown in FIG's 9 and 10), with modules in association with one or more boards. As shown in FIG. 11, LED's may be added to the power switch module circuitry to indicate whether the power switch module has failed. In one preferred embodiment of the present invention, surface mounted indicator lamps from Hewlett Packard Corporation (Model No. HSMH-TX00) were incorporated for this purpose. Equivalent or similar LED's could also be used.

It is thought that the techniques of the present invention and many of its attendant advantages will be understood from the foregoing description. It will be apparent that various changes may be made in the form and construction of the components thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages. The form of the invention described herein is merely a preferred or exemplary embodiment.

Claims

What is Claimed is:

A switch module apparatus, comprising: a body portion; at least one power MOSFET secured to said body; a printed circuit board assembly in association with said MOSFET for switching voltage sources to a board on which said apparatus is mounted, in a computer system. The apparatus of Claim 1, wherein said body is an aluminum extrusion.

The apparatus of Claim 1, wherein said body has fins for heat dissipation.

The apparatus of Claim 1, wherein said apparatus is placed in a mold and filled with epoxy. The apparatus of Claim 1, further comprising: at least one LED in association with said apparatus to indicate whether said apparatus has failed. A power switch module for use in live board insertion for computer systems, said module comprising; a body portion; means for controlling power on a slot-by-slot basis at a backplane of said computer system, said means in association with said body portion; and a circuit device in association with said means for controlling power, for providing voltage and logic.

7. The module of Claim 6, wherein said body portion is an aluminum extrusion.

8. The module of Claim 7, wherein said extrusion has fins for heat dissipation.

9. The apparatus of Claim 6, further comprising: at least one LED in association with said module to indicate whether said module is functioning.

10. The apparatus of Claim 6, wherein said means for controlling power is an FET.

11. The apparatus of Claim 10, wherein said FET is a MOSFET.