Constant power foldback mechanism programmable to approximate safe operating area of pass device for providing connection to load
IPC분류정보
국가/구분
United States(US) Patent
등록
국제특허분류(IPC7판)
G05F-001/569
G05F-001/10
출원번호
UP-0520018
(2006-09-13)
등록번호
US-7538528
(2009-07-01)
발명자
/ 주소
Heath, Jeffrey Lynn
출원인 / 주소
Linear Technology Corporation
대리인 / 주소
McDermott Will & Emery LLP
인용정보
피인용 횟수 :
7인용 특허 :
8
초록▼
System and methodology for supplying power to a load using a pass device for connecting the load. A current limit circuit prevents current supplied to the load from exceeding a current threshold. A foldback circuit modifies the current threshold in accordance with a prescribed condition. The foldbac
System and methodology for supplying power to a load using a pass device for connecting the load. A current limit circuit prevents current supplied to the load from exceeding a current threshold. A foldback circuit modifies the current threshold in accordance with a prescribed condition. The foldback circuit is configured to vary the current threshold in accordance with an approximate safe operating area of the pass device.
대표청구항▼
What is claimed is: 1. A system for supplying power to a load, comprising: a pass device for providing a connection to the load, a current limit circuit for preventing current supplied to the load from exceeding a current threshold, and a foldback circuit for modifying the current threshold in acco
What is claimed is: 1. A system for supplying power to a load, comprising: a pass device for providing a connection to the load, a current limit circuit for preventing current supplied to the load from exceeding a current threshold, and a foldback circuit for modifying the current threshold in accordance with a prescribed condition, the foldback circuit being configured to vary the current threshold in accordance with an approximate safe operating area of the pass device, and for reducing the current threshold when a voltage across the load is below a pre-set value. 2. A system for supplying power to a load, comprising: a pass device for providing a connection to the load, a current limit circuit for preventing current supplied to the load from exceeding a current threshold, and a foldback circuit for modifying the current threshold in accordance with a prescribed condition, the foldback circuit being configured to vary the current threshold in accordance with an approximate safe operating area of the pass device, and for monitoring a voltage across the load to correspondingly vary the current threshold so as to maintain a substantially constant level of DC power dissipated by the pass device. 3. The system of claim 2, wherein the maintained level of DC power corresponds to a maximum amount of dissipated power safely handled by the pass device. 4. A system for supplying power to a load, comprising: a pass device for providing a connection to the load, a current limit circuit for preventing current supplied to the load from exceeding a current threshold, and a foldback circuit for modifying the current threshold in accordance with a prescribed condition, the foldback circuit being configured to vary the current threshold so as to approximate a safe operating area of the pass device. 5. The system of claim 4, wherein the foldback circuit is configured for monitoring a voltage across the pass device to correspondingly vary the current threshold so as to maintain a substantially constant level of DC power dissipated by the pass device. 6. The system of claim 5, wherein the maintained level of DC power corresponds to a maximum amount of dissipated power safely handled by the pass device. 7. The system of claim 4, further comprising a foldback control circuit for controlling the foldback circuit so as to select variable values of the current threshold. 8. A system for supplying power to a load, comprising: a pass device for providing a connection to the load, a current limit circuit for preventing current supplied to the load from exceeding a current threshold, and a foldback circuit for modifying the current threshold in accordance with a prescribed condition, the foldback circuit being configured to vary the current threshold in accordance with an approximate safe operating area of the pass device, and for maintaining the current threshold at a first level when a voltage across the load is between a first voltage value and a second voltage value. 9. The system of claim 8, wherein the foldback circuit is configured for reducing the current threshold below the first level when the voltage across the load is below the first voltage value. 10. The system of claim 9, wherein the foldback circuit is configured for increasing the current threshold above the first level when the voltage across the load is above the second voltage value. 11. The system of claim 10, wherein the foldback circuit is configured for monitoring a voltage across the pass device to increase the current threshold above the first level. 12. The system of claim 11, wherein the foldback circuit is configured in accordance with an approximate safe operating area of the pass device when the current threshold varies with respect to the first level. 13. The system of claim 8, wherein the foldback circuit is configured for monitoring the voltage across the load to reduce the current threshold below the first level. 14. A system for supplying power to a powered device (PD) over a communication link, comprising: a power supply device having an output port for providing power to the PD over the communications link, the power supply device being configured to supply power via a semiconductor device, a current limit circuit for preventing an output current of the power supply device from exceeding a current threshold, and a foldback circuit for modifying the current threshold in accordance with a prescribed condition, the foldback circuit being configured to vary the current threshold so as to approximate a safe operating area of the semiconductor device. 15. The system of claim 14, wherein the power supply device is configured for supplying power to the PD over an Ethernet link. 16. The system of claim 15, wherein the foldhack circuit is configured for monitoring a voltage at the output port to modify the current threshold. 17. The system of claim 15, wherein the foldback circuit is configured for monitoring a voltage across the semiconductor device to modify the current threshold. 18. The system of claim 15, wherein the foldback circuit is configured for maintaining a constant level of DC power dissipated by the semiconductor device to approximate the safe operating area of the semiconductor device. 19. A method of supplying power to a load connected via a pass device, comprising the steps of: limiting current supplied to the load to a current threshold value, and varying the current threshold value so as to approximate a safe operating area of the pass device. 20. The method of claim 19, wherein the current threshold value is varied to maintain a constant level of DC power dissipated by the pass device so as to approximate the safe operating area of the pass device.
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이 특허에 인용된 특허 (8)
Itoh,Kohzoh; Tanaka,Shunsei, Constant-voltage power circuit with fold back current limiting capability.
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