Two relay switching circuit for fluorescent lighting controller
First Claim
1. A power-switching circuit for selectively switching power between a power source and a load, said power-switching circuit comprising:
- (a) first and third electrically-controllable switches connected in parallel between said power source and load;
(b) a second switch connected in series with said first switch, said second switch being electrically controllable; and
(c) means for sequentially closing said first, second and third switches in that order.
2 Assignments
0 Petitions
Accused Products
Abstract
In a fluorescent lighting controller, a switching circuit operates to selectively couple a bank of electronic ballasts to an AC power source (100-277 Volts, 50-60 Hertz). The switching circuit comprises a pair of relays, preferably connected in parallel, with one of such relays having a controllably conductive device, such as an electronic switch, and preferably a triac, connected in series therewith. With the relays open, an air gap isolates the power source and ballasts. In closing the relays in sequence, one relay provides a conductive path from the power source to the triac. After a suitable delay to allow the relay contacts to stabilize in the closed position, the triac is triggered to provide a conductive path from the power source to the ballasts, and a large current surge (as much as 300 amps) flow to the ballasts. After the current surge has subsided, the other relay is closed to provide a direct conductive path between the power source and ballasts. As a result of this arrangement, the switching circuit is low cost, compact and reliable over an extended period of time.
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Citations
24 Claims
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1. A power-switching circuit for selectively switching power between a power source and a load, said power-switching circuit comprising:
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(a) first and third electrically-controllable switches connected in parallel between said power source and load; (b) a second switch connected in series with said first switch, said second switch being electrically controllable; and (c) means for sequentially closing said first, second and third switches in that order. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A power-switching circuit for selectively switching power between an AC power source and an electronic ballast for a fluorescent lamp, said power-switching circuit comprising:
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(a) first and third electrically-controllable switches connected in parallel between said power source and electronic ballast; (b) a current-limiting second switch connected in series with said first switch, said second switch being electrically controllable; and (c) circuit means for sequentially closing said first, second and third switches in that order. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for switching power between an A.C. power source and a load, said method comprising the steps of:
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(a) providing a switching circuit comprising first and second switches connected in parallel between the power source and load, said first switch having a controllably conductive device in series therewith; (b) closing said first switch for a first predetermined time period; (c) after said first predetermined time period, rendering said controllably conductive device conductive for a second predetermined time period; and (d) thereafter closing said second switch. - View Dependent Claims (20, 21, 22, 23, 24)
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Specification