Electric lamp and discharge devices: systems – Current and/or voltage regulation
Reexamination Certificate
2000-06-08
2001-08-28
Philogene, Haissa (Department: 2821)
Electric lamp and discharge devices: systems
Current and/or voltage regulation
C315S307000, C315S077000, C315S149000, C315S158000
Reexamination Certificate
active
06281640
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to controlling the light intensity of a radio terminal, and in particular, to a device and method for controlling the brightness regardless of the capability of a light emitting device, thereby adaptively coping with a variation of the circumstances.
2. Description of the Related Art
A radio terminal uses a LED (Light Emitting Diode) for backlight, brightness of which is commonly fixed. Since the LED has a constant brightness, a user of the radio terminal can hardly sense the light in a bright place while he or she can easily sense the light in a dark place. Therefore, it is unreasonable for the LED to have constant brightness regardless of the circumstances. In addition, although the user can easily sense the light of the LED even at a low light intensity in the dark place, maintaining the constant brightness will cause a waste of the electric power. Therefore, there is a demand for a device and method for controlling the brightness of the LED according to circumstances.
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention to provide a device and method for controlling a light-emitting device in a radio terminal according to circumstances.
It is another object of the present invention to provide a device and method for controlling brightness of a radio terminal regardless of a capability of the light-emitting device.
To achieve the above objects, there is provided a device for controlling brightness of a radio terminal. In the brightness control device, a photometer measures brightness of incident light and generates an electric signal depending on the brightness. A light emitting device emits a light, and a power supply provides a voltage to the light emitting device in response to a control signal. A controller generates the control signal for enabling the power supply to provide the voltage to the light emitting device according to a brightness difference during light-on and light-off of the light emitting device. The controller comprises a switch for switching a signal output from the photometer to either a first input node or a second input node of a comparator; the comparator for generating a signal corresponding to a difference between the signals received at the first and second input nodes thereof; and a pulse density modulation (PDM) signal generator for generating a PDM signal for the signal output from the comparator as the control signal.
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patent: 5334914 (1994-08-01), Dean et al.
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patent: 6072281 (2000-06-01), Ogawa
Dilworth & Barrese LLP
Philogene Haissa
Samsung Electronics Co,. Ltd.
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