Backlight device and liquid crystal display apparatus
A backlight device includes: a plurality of LED elements arranged in a plurality of regions including a first region and a second region; a plurality of LED drive circuits configured to generate LED drive signals configured to drive the LED elements; a control circuit configured to outputs a vertical synchronization signal and current setting data configured to set luminance of the LED elements; and a time constant circuit that delays the vertical synchronization signal by a predetermined time. The LED drive circuits includes a first LED drive circuit associated with the LED elements in the first region. The time constant circuit includes a first time constant circuit connected to the first LED drive circuit. The first LED drive circuit is configured to receive the current setting data output from the control circuit and receive the first vertical synchronization signal delayed by the first time constant circuit.
1. A backlight device disposed on a back surface side of a liquid crystal display panel, the backlight device comprising:
a plurality of LED elements arranged in a plurality of regions including a first region and a second region;
a plurality of LED drive circuits configured to generate LED drive signal s configured to drive the plurality of LED elements, the plurality of LED drive circuits including a first LED drive circuit associated with LED elements in the first region and a second LED drive circuit associated with LED elements in the second region;
a control circuit configured to receive an image signal and output at least one vertical synchronization signal and current setting data configured to set luminance of each of the plurality of LED elements; and
at least one time constant circuit configured to delay the at least one vertical synchronization signal by a predetermined time,
wherein the at least one time constant circuit includes a first time constant circuit connected to the first LED drive circuit and/or a second time constant circuit connected to the second LED drive circuit, and
the first LED drive circuit is configured to receive the current setting data output from the control circuit, and receive a first vertical synchronization signal delayed by the first time constant circuit and/or the second LED drive circuit is configured to receive the current setting data output from the control circuit, and receive a second vertical synchronization signal delayed by the second time constant circuit.
2. The backlight device according to claim 1 ,
wherein the plurality of regions further include a third region,
the plurality of LED drive circuits further include a third LED drive circuit associated with LED elements in the third region,
the at least one time constant circuit includes at least two time constant circuits among the first time constant circuit, the second time constant circuit, and a third time constant circuit connected to the third LED drive circuit, and
at least two LED drive circuits of the first LED drive circuit, the second LED drive circuit, and the third LED drive circuit are configured to receive the current setting data output from the control circuit, and receive vertical synchronization signals delayed by predetermined times different from each other by the at least two time constant circuits.
3. The backlight device according to claim 1 ,
wherein the at least one time constant circuit includes a resistive element and a capacitance element.
4. The backlight device according to claim 1 ,
wherein the at least one time constant circuit is configured to be given two or more time constants.
5. The backlight device according to claim 4 ,
wherein the at least one time constant circuit includes a resistive element, two or more capacitance elements, and two or more transistors respectively connected to the two or more capacitance elements.
6. The backlight device according to claim 4 ,
wherein the at least one time constant circuit includes a transistor and a capacitance element.
7. The backlight device according to claim 1 , further comprising:
a current detection circuit connected to one of the plurality of LED drive circuits to which the at least one time constant circuit is connected, the current detection circuit being configured to detect a current of LED elements associated with the one of the plurality of LED drive circuits.
8. The backlight device according to claim 1 ,
wherein after receiving a vertical synchronization signal indicating start of a current vertical scanning period and before receiving a vertical synchronization signal indicating start of a next vertical scanning period, each of the plurality of LED drive circuits controls a current to be supplied to associated LED elements based on the current setting data regarding the current vertical scanning period.
9. The backlight device according to claim 1 ,
wherein the plurality of regions are arrayed in a matrix shape having a plurality of rows and columns, and
a difference between delay times Da of vertical synchronization signals received by two of the plurality of LED drive circuits corresponding to two regions adjacent in a row direction is greater than a difference between delay times Db of vertical synchronization signals received by two of the plurality of LED drive circuits corresponding to two of the plurality of regions adjacent in a column direction.
10. The backlight device according to claim 9 ,
wherein a difference between delay times Da of vertical synchronization signals received by two of the plurality of LED drive circuits corresponding to two of the plurality of regions adjacent in a row direction is constant regardless of a row.
11. The backlight device according to claim 9 ,
wherein a difference between delay times Db of vertical synchronization signals received by two of the plurality of LED drive circuits corresponding to two of the plurality of regions adjacent in a column direction is constant regardless of a column.
12. The backlight device according to claim 1 ,
wherein the at least one vertical synchronization signal includes a plurality of vertical synchronization signals, and
the at least one time constant circuit includes a plurality of time constant circuits that delay the plurality of vertical synchronization signals by a predetermined time.
13. A liquid crystal display apparatus comprising:
a liquid crystal display panel; and
the backlight device according to claim 1 .