Drive signal generator and image display apparatus
First Claim
1. A drive signal generation circuit which performs gradation control on a load by a drive signal having a stepped waveform, the drive signal being obtained by performing wave height-value modulation and pulse width modulation in combination using a multistage potential source (V(n−
- 1)<
Vn) having a potential range from V1 to Vn (n;
an integer equal to or larger than
2), and in which if the wave height value corresponding to input gradation data is Vm (2≦
m≦
n;
m;
an integer), the drive signal is caused to rise in such a manner that each output Vk (2≦
k≦
m;
k;
an integer) is produced one slot after the output V(k−
1) to increase the wave height value from off level to Vm in a stepping manner, one slot corresponding to a unit time of the pulse width modulation, and the drive signal is caused to fall in such a manner that each output V(k−
1) (1≦
k≦
m−
1) is produced one or two slots after the output Vk to reduce the wave height value from Vm to off level in a stepping manner, said drive signal generation circuit comprising;
a start pulse output circuit for generating a pulse with which a start of the output V1 is synchronized;
an end pulse output circuit which outputs a pulse with which an end of the output Vm is synchronized;
a first delay circuit which produces a plurality of delayed outputs by successively delaying one slot at a time the pulse with which the start of the output V1 is synchronized;
a second delay circuit which produces a plurality of delayed outputs by successively delaying in one-slot steps the pulse with which the end of the output Vm is synchronized;
a circuit which generates the pulse with which the start of the output V1 is synchronized, the pulse with which the end of the output Vm is synchronized, and a control signal for setting the pulse width of each output Vk (1≦
k≦
n) from the delayed outputs; and
a pulse width generation circuit which produces a pulse width signal of each output Vk (1≦
k≦
n) by the control signal.
1 Assignment
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Accused Products
Abstract
A drive signal generation circuit which performs gradation control on a load by a drive signal having a stepped waveform. In a case where the wave height value corresponding to input gradation data is Vm (2≦m≦n), the drive signal is caused to rise in such a manner that each output Vk (2≦k≦m) is produced one slot after the output V(k−1) to increase the wave height value V0 (reference potential) to Vm in a stepping manner. One slot corresponds to a unit time of the pulse width modulation. The drive signal is caused to fall in such a manner that each output V(k−1) (1≦k≦m−1) is produced one or two slots after the output Vk to reduce the wave height value from Vm to off level in a stepping manner. A delay circuit is used to delay signals slot by slot. A selection is made from delayed signals according to luminance data to determine a waveform. The circuit is also designed to enable the drive signal waveform rise position to be changed.
33 Citations
26 Claims
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1. A drive signal generation circuit which performs gradation control on a load by a drive signal having a stepped waveform, the drive signal being obtained by performing wave height-value modulation and pulse width modulation in combination using a multistage potential source (V(n−
- 1)<
Vn) having a potential range from V1 to Vn (n;
an integer equal to or larger than
2), and in which if the wave height value corresponding to input gradation data is Vm (2≦
m≦
n;
m;
an integer),the drive signal is caused to rise in such a manner that each output Vk (2≦
k≦
m;
k;
an integer) is produced one slot after the output V(k−
1) to increase the wave height value from off level to Vm in a stepping manner, one slot corresponding to a unit time of the pulse width modulation, andthe drive signal is caused to fall in such a manner that each output V(k−
1) (1≦
k≦
m−
1) is produced one or two slots after the output Vk to reduce the wave height value from Vm to off level in a stepping manner, said drive signal generation circuit comprising;
a start pulse output circuit for generating a pulse with which a start of the output V1 is synchronized;
an end pulse output circuit which outputs a pulse with which an end of the output Vm is synchronized;
a first delay circuit which produces a plurality of delayed outputs by successively delaying one slot at a time the pulse with which the start of the output V1 is synchronized;
a second delay circuit which produces a plurality of delayed outputs by successively delaying in one-slot steps the pulse with which the end of the output Vm is synchronized;
a circuit which generates the pulse with which the start of the output V1 is synchronized, the pulse with which the end of the output Vm is synchronized, and a control signal for setting the pulse width of each output Vk (1≦
k≦
n) from the delayed outputs; and
a pulse width generation circuit which produces a pulse width signal of each output Vk (1≦
k≦
n) by the control signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
- 1)<
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9. A drive signal generation circuit which generates a drive signal for gradation control on a light-emitting device, the drive signal having a waveform formed by selecting a signal level from a plurality of n wave height values corresponding to different light-emitting states, said drive signal generation circuit comprising:
-
a circuit A which outputs a raise signal with which a rise in the waveform of the drive signal is synchronized;
a circuit B which outputs at least (n−
1) number of delayed signals with an incremental delay of a predetermined time period from the raise signal; and
a circuit C which outputs the drive signal having a rising shape formed in the waveform of the drive signal in such a manner that the signal level is raised in synchronization with the raise signal from a signal level corresponding to an off state of the light-emitting device to the lowest of the n wave height values, and is thereafter increased to the higher wave height value one step at a time in synchronization with the delayed signals with the delay of the predetermined time period until a predetermined wave height value determined by input gradation data is reached. - View Dependent Claims (10, 11, 12, 13, 16, 18, 19, 20)
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14. A drive signal generation circuit which generates a drive signal for gradation control on a light-emitting device, the drive signal having a wave form formed by selecting a signal level from a plurality of n wave height values corresponding to different light-emitting states, said drive signal generation circuit comprising:
-
a circuit D which outputs a fall-causing signal with which a fall in signal level from a predetermined wave height value to a wave height value one step lower is synchronized;
a circuit E which outputs at least n number of delayed fall-causing signals with an incremental delay of a predetermined time period from the fall-causing signal; and
a circuit C which causes the signal level to fall to the wave height value one step lower than the predetermined wave height value in synchronization with the fall-causing signal, and thereafter causes the signal level to fall to the lower wave height values one step at a time in synchronization with the delayed fall-causing signals selected according to the input gradation data. - View Dependent Claims (15, 17)
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21. An image display apparatus comprising:
-
a plurality of scanning wirings and a plurality of modulation wirings connected in a matrix configuration;
light-emitting devices provided in correspondence with points of intersection of said scanning wirings and said modulation wirings; and
a drive signal generation circuit which generates a drive signal for performing gradation control on each of said light-emitting devices according in an input luminance signal, wherein the drive signal is obtained by modulation which is a combination of wave height-value modulation and pulse width modulation, and has a waveform in which the wave height value is successively increased in a stepping manner from a rise start point determined by a gradation value in a luminance signal related to the drive signal, and is successively reduced in a stepping manner from a fall start point determined irrespective of the gradation value.
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22. An image display apparatus comprising:
-
a plurality of scanning wirings and a plurality of modulation wirings connected in a matrix configuration;
light-emitting devices provided in correspondence with points of intersection of said scanning wirings and said modulation wirings; and
a drive signal generation circuit which generates a drive signal for performing gradation control on each of said light-emitting devices according to an input luminance signal, wherein the drive signal is obtained by modulation which is a combination of wave height-value modulation and pulse width modulation, and wherein, in a time period during which one of said plurality of scanning wirings is selected, each of part of the plurality of drive signals for gradation control on the plurality of light-emitting devices connected to the selected one of the scanning wirings has a waveform in which the wave height value is successively increased in a stepping manner from a rise start point determined by a gradation value in a luminance signal related to the drive signal, and is successively reduced in a stepping manner from a fall start point determined irrespective of the gradation value, and each of the other drive signals has a waveform in which the wave height value is successively reduced from a fall start point determined by a gradation value in a luminance signal related to the drive signal, and is, before the start of falling, successively increased in a stepping manner from a rise start point determined irrespective of the gradation value.
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23. A control method of controlling a light-emitting device by a drive signal which is wave height-value controlled with respect to a plurality of discrete wave height values, and which is pulse width controlled with respect to discrete pulse widths, said method comprising:
-
forming a digital video word including a plurality of subwords from gradation data;
selecting a part of a plurality of signals each having a predetermined difference in time from a predetermined timing on the basis of a part of, not the whole of, the plurality of subwords to produce a plurality of pulse width control signals in each of which a predetermined active time is specified; and
controlling the pulse width of each wave height value of the drive signal according to the active time. - View Dependent Claims (24, 25, 26)
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Specification