Electricity: electrical systems and devices – Safety and protection of systems and devices – Circuit interruption by thermal sensing
Reexamination Certificate
1999-03-29
2001-04-24
Sherry, Michael J. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
Circuit interruption by thermal sensing
C361S093200, C361S093800, C361S094000, C307S125000
Reexamination Certificate
active
06222716
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates generally to protection devices, and more particularly to those used in computer power bus lines, which power downstream electronic components and power management circuits.
Modern technologies have allowed more and more computers to be connected to one another by way of networking. Each computer may have numerous peripheral devices connected to it. Peripheral devices include not only the traditional ones such as a keyboard, a mouse, etc., but also those with new applications, e.g., a digital camera. In a typical network system, a hub is connected to a number of nodes, each of which may be connected to a number of sub-nodes. Each node or sub-node may be a computer or a peripheral device. Each sub-node may be connected to additional sub-sub-nodes, and so on. In such a network system, power is typically distributed to the various nodes and sub-nodes, etc. One example of such a network environment relates to the recent USB (Universal Serial Bus) standards, e.g., USB-IF, USB Specification, Rev. 1.1, 1998.
In such a network system, each network node is continuously monitored. Normal operation as well as fault conditions (e.g., overcurrent, over-temperature, under-voltage, etc.) are constantly reported to a control circuit. When a fault condition, e.g., overcurrent condition, occurs at one node or sub-node, it is important that any point of failure not affect the operation of the remaining portions of the network system. In other words, the failure must be localized and isolated in order to achieve high performance in a network system.
Various power bus line protection devices have been proposed. Most conventional protection devices include a power integrated circuit (PIC) switch that uses overload detection circuitry to continuously monitor current flowing to all ports controlled by the switch as well as the temperature of the switch. If the preset current limit of a port is exceeded, the “offending” port is turned off. If the preset temperature limit of the switch is reached as a result of an overcurrent status of a port, for example, all ports are usually turned off without regard to the non-overcurrent status of any of the other ports. This protection scheme has the potential to significantly reduce the dynamic operation range for the switch controlling multiple ports, because if only one port is overloaded, which causes the over-temperature status of the switch, all other ports are turned off nonetheless.
Another proposed protection scheme uses a temperature range for the switch as a reference guide for switching off the ports. If the temperature of the switch reaches the lower limit of the range, an overload detection circuitry monitors the temperature of the switch more closely, but no action is taken, in anticipation of a decrease in the temperature. If the temperature continues to rise and eventually reaches the higher limit of the temperature range, the port is switched off. Such a scheme, however, cannot reliably protect the switch against overload, because the temperature range creates an uncertain overload region. If the temperature of the switch stays near the high end of the range for a relatively long period of time, without ever reaching the higher limit of the range, there is a high probability that the switch will be permanently damaged.
Therefore, there is a need to provide a more reliable protection device and an improved PIC switch that increases the dynamic operation range of the conventional PIC switch, while ensuring normal operations.
SUMMARY OF THE INVENTION
The present invention provides a more reliable protection device and an improved PIC switch that increases the dynamic operation range of the conventional PIC switch, while ensuring normal operations.
According to one embodiment of the present invention, a switch device is provided and comprises first and second ports; a fault protection logic for detecting over-temperature status of the device and overcurrent status of each of the first and second two ports and for generating control signals based on the over-temperature status and the overcurrent status of each of the two ports; and a control logic, responsive to the control signals, for switching on and off the two ports. In this embodiment, if there is an over-temperature and there is an overcurrent at the first port, but there is no overcurrent at the second port, the protection logic controls the control logic to switch off the first port and after a predetermined time period, the protection logic re-checks the over-temperature status of the device and controls the control logic to switch off the second port if the over-temperature persists. The predetermined time period is preferably about 300 ms.
According to one aspect of the embodiment of the invention, if there is an over-temperature and the overcurrent status at each of the ports is the same, the protection logic controls the control logic to switch off both of the ports.
According to another aspect of the embodiment of the invention, the protection logic includes a current limit circuit and if there is no over-temperature, but there is overcurrent status at both of the ports, the current limit circuit causes the control logic to limit current flowing through each of the ports to a predetermined value. If there is no over-temperature and there is no overcurrent at the first port, but there is overcurrent at the second port, the current limit circuit causes the control logic to limit current flowing through the second port to the predetermined value. The predetermined value is preferably about 500 mA.
According to a further aspect of the embodiment of the invention, the control logic includes a flag control circuit for setting a flag for each of the ports if such port is switched off and for setting a flag for each of the ports if current is limited at such port.
According to another embodiment of the invention, a method for protecting a switch device having first and second ports is provided. The method comprises the steps of: (a) detecting an over-temperature status of the device; (b) detecting an overcurrent status of each of the first and second ports; (c) if there is over-temperature and there is overcurrent at first port, but there is no overcurrent at the second port, switching off the first port and waiting for a predetermined time period; (d) after waiting for the predetermined time period, re-checking the over-temperature status of the device; and (e) if, after waiting for the predetermined time period, the over-temperature persists, switching off the second port. The predetermined time period is preferably about 300 ms.
According to the method embodiment of the invention, if there is an over-temperature and the overcurrent status at each of the ports is the same, both of the ports are switched off. If there is no over-temperature, but there is overcurrent status at both of the ports, the current flowing through each of the ports is limited to a predetermined value. If there is no over-temperature and there is no overcurrent at the first port, but there is overcurrent at the second port, the current flowing through the second port is limited to a predetermined value. The predetermined value is preferably about 500 mA.
Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 4589052 (1986-05-01), Dougherty
patent: 4882502 (1989-11-01), Kobayashi
patent: 5003426 (1991-03-01), Yeh et al.
patent: 5111123 (1992-05-01), Hach et al.
patent: 5168414 (1992-12-01), Horstmann
patent: 5297014 (1994-03-01), Saito et al.
patent: 5436821 (1995-07-01), Inoue
patent: 5642072 (1997-06-01), Miyamoto et al.
patent: 5737169 (1998-04-01), Sellers
patent: 5894394 (1999-04-01), Baba et al.
patent: 5900683 (1999-05-01), Rinehart et al.
patent: 5969981 (1999-10-01), Kono
patent: 6000042 (1999-12-01), Henrie
patent: 92 06 466 U (1993-06-01), None
patent: 0 717 341 (199
Chiang Justin
Cogan Adrian I.
Wiener Paul
Huynh Kim
Sherry Michael J.
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