Cold cathode tube lighting device, tube current detecting circuit used in cold cathode tube lighting device, tube current controlling method and integrated circuit
AssigneeNEC LCD Technologies, Ltd.
InventorNobuaki Honbo
Life of this patent
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Abstract
A cold cathode tube lighting device is provided which is capable of achieving stable luminance when driven by applying driving pulses to input terminals on both sides of each of two or more cold cathode tubes. Each of currents flowing through coils in each of coil units on both sides of each of two or more cold cathode tubes is detected by voltage detecting sections and a tube current flowing through each of the cold cathode tubes based on a value obtained by adding each of the currents using an adder and a duty ratio of each of driving pulses is controlled so that the tube current becomes a specified current value to keep the luminance of the cold cathode tubes constant.
Claims20
A cold cathode tube lighting device for lighting two or more cold cathode tubes by applying driving pulses with different phases to be output from each of inverters through each of ballast elements used to make uniform a tube current of each of said cold cathode tubes to input terminals on both sides of each of two or more cold cathode tubes comprising:
- a tube current controlling unit to detect each current flowing through each of ballast elements based on a voltage detected by a voltage detecting section and to detect a tube current flowing through each of said cold cathode tubes based on the detected each current flowing through each of ballast elements and to control so that said tube current becomes a specified current value,
- wherein each ballast element is a coil unit, and each coil unit is bridged by a voltage detecting section.
A tube current controlling method to be used in a cold cathode tube lighting device which applies driving pulses with different phases to be output from each of inverters through each of ballast elements used to make uniform a tube current of each of said cold cathode tubes to input terminals on both sides of each of two or more cold cathode tubes, wherein each ballast element is a coil unit, and each coil unit is bridged by a voltage detecting section, said tube current controlling method comprising:
- detecting each current flowing through each of ballast elements based on a voltage detected by said voltage detecting section, and
- detecting a tube current flowing through each of said cold cathode tubes based on the detected each current flowing through each of said ballast elements and exerting control so that said tube current becomes a specified value.
Dependencies are inferred from the claim text.