LCD backlight converter having a temperature compensating means for regulating brightness
First Claim
1. An LCD backlight converter for regulating brightness, comprising:
- a cold cathode fluorescent lamp;
a pulse width modulator coupled to said lamp for providing voltage and current to said lamp;
a DC/DC power adapter supplying power to said pulse width modulator;
a temperature compensating device coupled to said pulse width modulator and said lamp, said temperature compensating device including a temperature sensor for detecting environmental temperature variation and a voltage divider for providing a signal in response to the temperature variation; and
a backlight feedback control circuit receiving the signal from said voltage divider and generating a first control signal for controlling the output voltage level of said DC/DC power adapter and a second control signal for controlling the output frequency of said pulse width modulator;
wherein both voltage and current provided to said lamp by said pulse width modulator increase or decrease according to the temperature variation.
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Accused Products
Abstract
A LCD backlight converter includes a temperature detection circuit arranged between a cold cathode fluorescent lamp and a backlight feedback control circuit. The temperature detection circuit has a sensor connected in series between a pulse width modulator and the cold cathode fluorescent lamp for detecting the environmental temperature. A DC/DC power adapter provides power to the pulse width modulator for driving the cold cathode fluorescent lamp. The output of the temperature detection circuit is sent to the backlight feedback control circuit that generates controls signals for controlling the output frequency of the pulse width modulator as well as the output voltage of a DC/DC power adapter. Appropriate driving voltage and current are provided to the cold cathode fluorescent lamp by the pulse width modulator according to the environmental temperature so that the lamp is normally turned on and maintains normal brightness.
44 Citations
3 Claims
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1. An LCD backlight converter for regulating brightness, comprising:
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a cold cathode fluorescent lamp; a pulse width modulator coupled to said lamp for providing voltage and current to said lamp; a DC/DC power adapter supplying power to said pulse width modulator; a temperature compensating device coupled to said pulse width modulator and said lamp, said temperature compensating device including a temperature sensor for detecting environmental temperature variation and a voltage divider for providing a signal in response to the temperature variation; and a backlight feedback control circuit receiving the signal from said voltage divider and generating a first control signal for controlling the output voltage level of said DC/DC power adapter and a second control signal for controlling the output frequency of said pulse width modulator; wherein both voltage and current provided to said lamp by said pulse width modulator increase or decrease according to the temperature variation. - View Dependent Claims (2, 3)
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Specification
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- Resources
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Current AssigneeTwinhead International Corporation
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Original AssigneeTwinhead International Corporation
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InventorsYeh, Henry
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Primary Examiner(s)VU, DAVID HUNG
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Application NumberUS09/286,382Time in Patent Office421 DaysField of Search315/149, 315/156, 315/157, 315/158, 315/159, 315/307, 315/224US Class Current315/149CPC Class CodesG09G 2320/041 Temperature compensationH05B 41/36 ControllingH05B 41/3927 by pulse width modulation H...
