Method of driving a lamp, lamp driving apparatus, and liquid crystal display device having the same
View Patent ↗A lamp driving apparatus includes a change rate calculating section, a dimming transforming section and a power supplying section. The change rate calculating section calculates a change rate signal from an image signal corresponding to the image. The dimming transforming section outputs a digital dimming signal and an analog dimming signal, in response to a dimming signal provided from an external device and the change rate signal. The power supplying section provides the lamp with power, in response to a vertical synchronizing signal, the analog dimming signal and the digital dimming signal. Thus, although an instantaneous lamp current is increased, life and characteristics of the lamp will not be adversely influenced, and motion blur of a moving image may be removed.
1. A liquid crystal display (“LCD”) device comprising:
a panel section displaying an image using a liquid crystal layer;
a lamp section providing the panel section with light;
an image signal processing section providing the panel section with an image signal that is supplied from an external device; and
a lamp driving section driving the lamp section based on a change rate of the image signal, wherein the lamp driving section comprises:
a dimming transforming section outputting an analog dimming signal and a pulse-width modulation (“PWM”) dimming signal.
2. The LCD device of claim 1 , wherein the lamp driving section decreases an emission duty cycle of a lamp of the lamp section, and increases a current that is supplied to the lamp section during a period when the change rate is relatively high.
3. The LCD device of claim 1 , wherein the lamp driving section maintains an emission duty cycle of the lamp and a current that is supplied to the lamp section during a period when the change rate is relatively low.
4. The LCD device of claim 1 , wherein the light driving section comprises:
a change rate calculating section calculating a change rate signal from the image signal; and
a power supplying section providing the lamp with power based on a vertical synchronizing signal corresponding to the image signal and the analog and PWM dimming signals,
wherein the dimming transforming section outputs the analog dimming and PWM dimming signals, in response to a dimming signal that is supplied from an external device and the change rate signal.
5. The LCD device of claim 4 , wherein the change rate calculating section is an MPEG decoder.
6. The LCD device of claim 4 , wherein the dimming transforming section comprises:
a storing section storing an analog dimming reference value;
a comparator comparing the change rate signal and the reference change rate signal that is supplied from an external device, to output a comparative-determining signal;
an adder adding the comparative-determining signal and the analog dimming reference value, to output the analog dimming signal;
a subtracter subtracting the comparative-determining signal from a dimming signal that is supplied from an external device, to output the subtracted dimming signal; and
a PWM transforming section transforming the subtracted dimming signal into a PWM dimming signal, and outputting the PWM dimming signal.
7. The LCD device of claim 4 , wherein the dimming transforming section provides the power supplying section with a PWM dimming signal having a normal “on” interval, and an analog dimming signal having a normal level, when the calculated changes rate is smaller than or equal to the reference change rate, and provides the power supplying section with a PWM dimming signal having a short “on” interval that is relatively shorter than the normal “on” interval, and an analog dimming signal having a high level that is relatively higher than the normal level, when the calculated change rate is greater than the reference change rate.
8. The LCD device of claim 1 , wherein the image signal processing section comprises,
a timing control section that receives a first signal and a first synchronizing signal, to output a second image signal, a second synchronizing signal and a third synchronizing signal;
a data driver outputting a data signal to the panel section, in response to the second image signal and the second synchronizing signal; and
a gate driver outputting a gate signal to the panel section, in response to the third synchronizing signal, wherein the timing control section comprises a change rate calculating section calculating a change rate signal from the first image signal.
9. The LCD device of claim 8 , wherein the lamp driving section comprises:
a power supplying section providing the lamp section with power based on a fourth synchronizing signal corresponding to the image signal and the analog and PWM dimming signals,
wherein the dimming section outputs the analog dimming and PWM dimming signals, in response to a dimming signal that is supplied from an external device and the change rate signal.
10. The LCD device of claim 9 , wherein the fourth synchronizing signal is a vertical synchronizing signal.
11. The LCD device of claim 9 , wherein the dimming transforming section comprises:
a storing section storing an analog dimming reference value;
a comparator comparing the change rate signal with the reference change rate signal that is supplied from an external device, to output a comparative-determining signal;
an adder adding the comparative-determining signal and the analog dimming reference value, to output the analog dimming signal;
a subtracter subtracting the comparative-determining signal from a dimming signal that is supplied from an external device, to output the subtracted dimming signal; and
a PWM transforming section transforming the subtracted dimming signal into a PWM dimming signal, and outputting the PWM dimming signal.
12. The LCD device of claim 8 , wherein the change rate calculating section comprises:
a first memory configured to store an image signal corresponding to the n-th frame, and output an image signal that is stored corresponding to the (n−1)-th frame;
a second memory configured to store an image signal corresponding to the (n−1)-th frame, and output an image signal that is stored corresponding to the (n−2)-th frame; and
a comparative-determining section that compares image signals of the (n−1)-th frame that are provided from the first memory with image signals of the (n−2)-th frame that are provided from the second memory to provide the lamp driving section with the change rate signal.
13. The LCD device of claim 12 , wherein the comparative-determining section outputs the change rate signal based on a change rate of a histogram corresponding to the image signal of the (n−2)-th frame and the image signal of the (n−1)-th frame, respectively.
14. The LCD device of claim 12 , wherein the comparative-determining section outputs the change rate signal based on an edge change rate of an object corresponding to the image signal of the (n−2)-th frame and the image signal of the (n−1)-th frame, respectively.