Power overload protection for a system unit

Details Power overload protection for a system unit Power overload protection for a system unit

1999-10-08

2002-07-16

Sircus, Brian (Department: 2839)

Electricity: electrical systems and devices

Safety and protection of systems and devices

With specific current responsive fault sensor

Reexamination Certificate

active

06421215

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention relates to powering system units. In particular, the invention relates to providing a computer system with a reliable power supply for use in environments and applications that place high demands on system reliability, for example in the telecommunications industry.
Deregulation and privatization is causing unprecedented competition in the worldwide telecommunications market. This climate of fierce competition has meant that service providers must introduce new, more sophisticated and user-friendly services at an accelerated pace to retain or attract subscribers, while not compromising traditional telecommunications company (telco) service quality.
These pressures of competition have also placed high demands on Network Equipment Providers (NEPs). Traditionally, NEPs have designed, built and supported proprietary computing equipment, as the strict telco requirements could not be met by the commercial computing sector. Those requirements include the so-called Telcordia Technologies Network Equipment Buildings Systems (NEBS) tests. However, due to the lead times required to design and test such proprietary equipment, and the cost of supporting such equipment, there is a need to find another route, at least for the supply of the more cost and performance sensitive sectors within the telco industry.
A major concern of the telco sector is the reliability of systems. To address this issue, many prior systems, for example for providing the function of a telco server computer, have employed redundant computer systems. In such a redundant computer system, two or more processing sets are provided, typically with each being configured on a separate motherboard and with a mechanism for voting between the processing sets to determine whether one is faulty. Each of the processing sets may include one or more processors. If the voting system determines that one of the processing sets is faulty, then the other one or more processing sets can continue to function. In such systems, other multiple versions of other of the components of the system can be provided. For example, it is known to provide three power supply units such that if one of the power supply units fails, the system can continue to function with power from the remaining two power supply units.
In order to keep up with the ever-increasing demands of the telco industry, and in order to provide equipment at reasonable cost and within reasonable time scales, it would be desirable to use as many off-the-shelf computer system components as possible, rather than having to design and test each system in its entirety from scratch. For example, it would be desirable to select components designed for the commercial computing sector. However, such equipment is typically not designed with the stringent requirements of the telco industry in mind.
Accordingly, it is an aim of the present invention to address the provision of cost-effective equipment that can meet technical demands of the telco environments, while also meeting the modern commercial demands of that environment.
SUMMARY OF THE INVENTION
Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Combinations of features from the dependent claims may be combined with features of the independent claims as appropriate and not merely as explicitly set out in the claims.
In accordance with one aspect of the invention, there is provided a power distribution sub-system for a system unit. The power distribution sub-system includes connections for receiving power from n+m power supply units, where n and m are integers and n power supply units are required to power the system. The power distribution sub-system further comprises:
a common power rail to which the power supply units are connectable;
a current sensor for detecting a current greater than n*Imax, where Imax is the maximum power output of a power supply unit, the current sensor being operable to output an overcurrent signal when the sensed current exceeds n*Imax; and
a controllable shunt, connected to receive the overcurrent signal and operative to shunt the power rail to ground on receipt of the overcurrent signal, thereby to discharge any stored charge to ground.
A requirement of the telco sector is the ability safely to power down a system in the event of an overcurrent (short) situation to reduce overheating and fire risks. By providing the overcurrent protection as part of the power distribution sub-system rather than in the power supply units, it is only necessary to secure the system for n*Imax (where Imax is the maximum current that can be output by a power supply), rather than (n+1)*Imax, which would be needed if each power supply separately included its own overcurrent protection. By providing a shunt in the power distribution sub-system charge to be discharged from all of the power supplies and the system circuitry in a controlled manner, minimizing shock and fire dangers.
In an embodiment of the invention, the controllable shunt is a transistor, for example a silicon controlled rectifier (SCR), a Metal Oxide Semiconductor Field Effect transistor (MOSFET), an Insulated Gate Bipolar Transistor (IGBT), etc.).
Where there are a plurality of power rails, a corresponding plurality of controllable shunts can be provided, each shunt being connected to receive the overcurrent signal and being operative to shunt the corresponding power rail to ground on receipt of the overcurrent signal, thereby to discharge any stored charge to ground. The current sensing could be provided for all power rails or only selected power rails, as required. The current sensor can also be operable to cause the power supply units to be turned off on detecting an overcurrent situation.
In an embodiment of the invention, a power distribution board carried the power distribution system, including the current sensor and the controllable shunt. The power distribution board can form part of a power sub-frame sub-assembly for the system unit. The power distribution board can be provided with connectors for connecting with removably mounted power supply units and can distribute the power from the power supplies for various system components.
In a particular example of the invention, n is 2 and m is 1.
In accordance with another aspect of the invention, there is provided a system unit comprising electronic circuitry and a power distribution sub-system. The power distribution sub-system comprises connections for receiving power from n+m power supply units, where n and m are integers and n power supply units are required to power the system. The power distribution sub-system further comprises: a common power rail to which the power supply units are connectable;
a current sensor for detecting a current greater than n*Imax, where Imax is the maximum power output of a power supply unit, the current sensor being operable to output an overcurrent signal when the sensed current exceeds n*Imax; and
a controllable shunt, connected to receive the overcurrent signal and operative to shunt the power rail to ground on receipt of the overcurrent signal, thereby to discharge any stored charge to ground.
A latched shutdown of the power supply units is also effected on detecting an overcurrent.
The system unit can be a computer system unit including processing circuitry. The system can be rack mountable.
In accordance with a further aspect of the invention, there is provided a method of providing protected power a system unit where power is supplied by n+m power supply units, n and m being integers and n power supply units being required to power the system. The method comprises:
providing power in common from the power supplies to a common power rail;
sensing current on the power rail; and
shunting the power rail to ground on sensing a current greater than n*Imax,
where Imax is the maximum power output of a power supply unit, thereby to discharge any stored charge to ground.
It will be appreciated from the above that the provision of a power distribution subsys

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