Staggering switching signals for multiple cold cathode...

Details Staggering switching signals for multiple cold cathode... Staggering switching signals for multiple cold cathode...

2006-11-28

2006-11-28

Wong, Don (Department: 2163)

Electric lamp and discharge devices: systems

Plural load device systems

C315S2090SC, C315S307000

Reexamination Certificate

active

07141941

ABSTRACT:
In order to minimize switching-induced electromagnetic interference in a power supply switching circuit of the type used to control the AC power for multiple high voltage devices, such as cold cathode fluorescent lamps employed for backlighting a large scale liquid crystal display, the gating signals that are used to switch lamp-driving inverter circuits ON and OFF are staggered, or slightly offset in time, so that no two switching devices will be switched at the same time. By slightly offset in time is meant that the time differential between any pair of switching signals is relatively small compared to the period of the switching signal frequency. This has the effect of spreading out and thereby diminishing the magnitude of the spectral content of both capacitively and inductively coupled transients that are produced at switching times of the inverter circuits.

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