« PreviousContinue »
United States Patent [w]
Demo et al.
US005821641A [ii] Patent Number:  Date of Patent:
5,463,261 10/1995 Skarda et al 395/283
5,542,049 7/1996 Kurokawa et al 395/280
5,619,076 4/1997 Layden et al 307/139
5,627,416 5/1997 Kantner 395/283
Primary Examiner—William M. Shoop, Jr.
Assistant Examiner—Peter Ganjian
Attorney, Agent, or Firm—Jenkens & Gilchrist
A device for enabling and disabling the supply ol power from a power source to a computer, the power source having a primary side and a secondary side, the device including an interlock switch connected to the computer, the interlock switch selectably positionable between open and closed positions; and two optocouplers coupled in parallel, both ol which are relerenced to the secondary side ol the power source. When the interlock switch is closed, the first optocoupler is active. This enables the supply ol power from the power source to the computer. When the interlock switch opens, the first optocoupler shuts off. This disables the supply ol power from the power source to the computer. Further when the interlock switch is opened, the second optocoupler is saturated. This overrides the regulation leedback circuitry from regulating the power supplied by the power source driving the power outputted to the computer to zero. When the interlock switch is closed, the second optocoupler operates in the linear region. This enables the regulation leedback circuitry to regulate the power supplied by the power source to the computer.
17 Claims, 2 Drawing Sheets
U.S. Patent Oct. 13,1998 sheet 1 of 2 5,821,641
SECONDARY SUPPLY POWER
REFERENCED INTERLOCK CIRCUIT
FIELD OF THE INVENTION
This invention relates to computer chassis interlock 5 circuits, and more particularly, to a safety interlock circuit for safely disconnecting the power source of a computer system, with a secondary side referenced interlock circuit.
BACKGROUND OF THE INVENTION 10
In computer systems utilizing power supplies capable of providing hazardous energies, which is often defined as anything greater than 240VA, it is highly desirable that the computer housing or enclosure be designed to prevent a user from coming into contact with conductors or surfaces that are connected to an output. Current technologies utilize interlock circuits that shut down the power supply when an attempt is made by the user to enter the chassis, such as when an access panel is opened. These interlock circuits are 2Q normally referenced to the main primary supply of the power supply. Further, these interlock circuits must meet certain requirements of single component fault tolerance and reliability. Meeting the requirements for single component fault tolerance is particularly difficult. 25
Many of the current technologies meet the interlock requirements by placing a two pole switch in the AC line input. Therefore, each of these interlock switches must carry full line current and voltage. Because of this, most of the interlock switches are large and expensive. The interlocking 30 of multiple panels requires multiple interlock switches and complex AC line wiring or complex mechanical arrangements to connect one switch to all the panels. If low voltage primary interlocks are used, the switch requirement is less stringent. However, double insulated wire must still be used 35 to connect these switches. Double insulated wiring for these low voltage primary switches is expensive and very cumbersome to route to multiple panels. As can be appreciated, the above described are just a few of the problems with current technologies of interlock circuits.
The present invention overcomes the above identified problems as well as other shortcomings and deficiencies of existing technologies by providing a low cost secondary side 45 referenced interlock circuit.
In particular the present invention provides an interlock system for connecting and disconnecting the supply of power from a power source to a computer, the power source having a main primary supply and a main secondary supply. 50 The interlock system includes an interlock switch connected to the computer, which is selectably positionable between open and closed positions. The interlock system further includes two optocouplers coupled in parallel, both of which are referenced to the secondary supply of the power source. 55 When the interlock switch closes, the first optocoupler becomes active, enabling the power source to supply power to the computer. When the interlock switch is opened, the first optocoupler shuts off, disconnecting the power source out of connection with the computer. Further when the 60 interlock switch is opened, the second optocoupler saturates, overriding regulation feedback circuitry to the power source. The regulation feedback circuitry regulates the power supplied by the power source to the computer. When the interlock switch is closed, the second optocoupler operates 65 in a linear mode enabling the regulation feedback circuitry with the power source.
BRIEF DESCRIPTION OF THE DRAWINGS
A more complete understanding of the present invention may be had by reference to the following Detailed Description when taken in conjunction with the accompanying Drawings wherein:
FIG. 1 is a functional block diagram of a computer system utilizing the present invention; and
FIG. 2 is a detailed schematic diagram of the present invention.
Referring now to FIG. 1, there is illustrated a block diagram of a computer system 10 utilizing the present invention. As depicted computer system 10 includes a computer 12, a power supply 15 including a main primary supply 14 and an auxiliary primary 14a, a main secondary supply 16, and an auxiliary secondary 16a, a primary/secondary power supply boundary 18, regulation feedback circuits 20, interlock circuit 22, and a switch 24.
As depicted interlock circuit 22 is coupled to switch 24, main secondary supply 16, and is further coupled to the main primary supply 14 of power supply 15 through regulation feedback circuits 20. Main primary supply 14 is further coupled to main secondary supply 16 through primary/ secondary power supply boundary 18. Main primary supply 14 and main secondary supply 16 of power supply 15 provide the power to computer 12.
Switch 24, which is referenced to the secondary supply, is generally a mechanical interlock switch which can be attached at various locations in the computer system 10, such as to a removable computer component module, a removable computer chassis panel, or an access door.
Computer system 10 is powered by main primary supply 14 and main secondary supply 16 of power supply 15. Main primary supply 14 and main secondary supply 16 provide the high input AC current to corresponding components of computer 12, (for example 3 volts at 30 amps, 5 volts at 40 amps and 12 volts at 27 amps). The auxiliary primary 14a controls the PWMs of the primary side of power supply 15. The auxiliary secondary 16a provides low voltage/low current to interlock circuit 22 and also generally powers the low power "housekeeping" devices of computer 12, such as an on-board clock or static RAM.
The primary/secondary power supply boundary 18 is an isolation space separating the main primary supply 14 from the main secondary supply 16 of power supply 15. Regulation feedback circuits 20 maintains and regulates the power supplied by power supply 15, to computer 10 according to selected power supply specifications.
In general operation, when switch 24 is closed, the main primary supply 14 and the main secondary supply 16 of power supply 15 provide power to computer 12. When switch 24 is opened, interlock circuit 22 interfaces with regulation feedback circuits 20 to force the primary side supply 14 to power down, and further immediately drains current to the circuits powered by the main primary supply 14. Interlock circuit 22 also shuts off the main secondary supply 16. A more detailed description of the operation of interlock circuit 22 is given below.
Referring now to FIG. 2, there is illustrated a more detailed schematic of interlock circuit 22 as shown in FIG. 1. As depicted interlock circuit 22 includes optocouplers 26 and 28, transistors 30, 32 and 34, diodes 36, 38 and 40, resistors 42, 44, 46, 48 and 50, and an interlock output pin 52. Optocoupler 26 includes an LED 26b and a transistor