Light-emitting device, display device, and LED display device
An anode line control circuit provided corresponding to each of anode lines includes a first resistor connected to a control terminal of a first switching element, which controls the supply of a power supply voltage to the anode line, and a second switching element connected to a second resistor connected to one end of the anode line. When the first switching element changes from an OFF state to an ON state, the second switching elements corresponding to the anode lines other than the anode line connected to the first switching element are maintained in the OFF state.
1. A light-emitting device using an LED as a light source, the light-emitting device comprising:
a plurality of LED units each constituted by one or a plurality of LEDs, the plurality of LEDs being divided up into a plurality of blocks;
a plurality of power supply lines provided corresponding to the plurality of blocks in a one-to-one manner, and connected to upstream ends of the LED units included in the corresponding blocks;
a switching circuit configured to switch, between the plurality of power supply lines, a supply destination of a power supply voltage for driving the LEDs, to drive the plurality of LED units a block at a time;
a plurality of lighting control lines respectively connected to downstream ends of a number of the LED units equal to a number of the plurality of blocks; and
an LED drive circuit configured to control a current supplied to the LED included in each of the plurality of LED units, the LED drive circuit being connected to the plurality of lighting control lines,
wherein the switching circuit includes a plurality of power supply line control circuits provided corresponding to the plurality of power supply lines in a one-to-one manner,
each of the power supply line control circuits includes
a first switching element including a control terminal, a first conduction terminal to which the power supply voltage is applied, and a second conduction terminal connected to the corresponding power supply line,
a first resistor, a first control signal being applied to one end of the first resistor and the other end of the first resistor being connected to the control terminal of the first switching element,
a second switching element including a control terminal to which a second control signal is applied, a first conduction terminal, and a second conduction terminal to which a predetermined potential is applied, and
a second resistor, one end of the second resistor being connected to the corresponding power supply line and the other end of the second resistor being connected to the first conduction terminal of the second switching element, and
when, of two of the power supply lines to which the power supply voltage is continuously supplied, the power supply line to which the power supply voltage is supplied first is defined as a first power supply line of interest, and of the two power supply lines, the power supply line to which the power supply voltage is supplied subsequently is defined as a second power supply line of interest, at a time at which the first switching element corresponding to the second power supply line of interest changes from an OFF state to an ON state based on the first control signal, a plurality of the second switching elements respectively corresponding to the plurality of power supply lines other than the second power supply line of interest are maintained in the OFF state based on the second control signals.
2. The light-emitting device according to claim 1 ,
wherein, when the supply destination of the power supply voltage is switched from the first power supply line of interest to the second power supply line of interest,
during a period from a time at which the first switching element corresponding to the first power supply line of interest changes from the ON state to the OFF state based on the first control signal to a time at which the first switching element corresponding to the second power supply line of interest changes from the OFF state to the ON state based on the first control signal, the plurality of second switching elements respectively corresponding to the plurality of power supply lines other than the second power supply line of interest change from the ON state to the OFF state based on the second control signals, and
during a period after a time at which the first switching element corresponding to the second power supply line of interest changes from the OFF state to the ON state based on the first control signal, the plurality of the second switching elements respectively corresponding to the plurality of power supply lines other than the second power supply line of interest sequentially change from the OFF state to the ON state based on the second control signals.
3. The light-emitting device according to claim 1 ,
wherein, when the supply destination of the power supply voltage is switched from the first power supply line of interest to the second power supply line of interest,
during a period from a time at which the first switching element corresponding to the first power supply line of interest changes from the ON state to the OFF state based on the first control signal to a time at which the first switching element corresponding to the second power supply line of interest changes from the OFF state to the ON state based on the first control signal, after the second switching element corresponding to the first power supply line of interest changes from the OFF state to the ON state based on the second control signal, the plurality of the second switching elements respectively corresponding to the plurality of power supply lines change from the ON state to the OFF state based on the second control signals,
during a period after a time at which the first switching element corresponding to the second power supply line of interest changes from the OFF state to the ON state based on the first control signal, the plurality of the second switching elements respectively corresponding to the plurality of power supply lines other than the second power supply line of interest sequentially change from the OFF state to the ON state based on the second control signals, and
the second switching element corresponding to the second power supply line of interest is maintained in the OFF state based on the second control signals during a period in which the power supply voltage is supplied to the second power supply line of interest.
4. The light-emitting device according to claim 1 ,
wherein, when the supply destination of the power supply voltage is switched from the first power supply line of interest to the second power supply line of interest,
during a period before a time at which the first switching element corresponding to the first power supply line of interest changes from the ON state to the OFF state based on the first control signal, the second switching element corresponding to the first power supply line of interest changes from the OFF state to the ON state based on the second control signal,
during a period from a time at which the first switching element corresponding to the first power supply line of interest changes from the ON state to the OFF state based on the first control signal to a time at which the first switching element corresponding to the second power supply line of interest changes from the OFF state to the ON state based on the first control signal, the second switching element corresponding to the first power supply line of interest changes from the ON state to the OFF state based on the second control signal, and
the second switching element corresponding to the first power supply line of interest is maintained in the OFF state based on the second control signal during a period excluding a predetermined period during which the supply destination of the power supply voltage is switched from the first power supply line of interest to the second power supply line of interest.
5. The light-emitting device according to claim 1 ,
wherein the switching circuit includes a plurality of adjustment circuits provided corresponding to the plurality of power supply line control circuits in a one-to-one manner, and
each of the adjustment circuits generates, based on one adjustment signal, the first control signal and the second control signal supplied to the corresponding power supply line control circuit.
6. The light-emitting device according to claim 5 ,
wherein each of the adjustment circuits includes
a first delay circuit configured to output a signal generated by delaying the adjustment signal by a first time period having a predetermined length,
a first NOT circuit configured to output a logical inversion signal of the adjustment signal,
an AND circuit configured to output a signal representing a logical product of the signal output from the first delay circuit and the signal output from the first NOT circuit,
a second delay circuit configured to output, as the second control signal, a signal generated by delaying the signal output from the AND circuit by a second time period having a predetermined length, and
a second NOT circuit configured to output, as the first control signal, a logical inversion signal of the signal output from the first delay circuit.
7. A display device comprising:
a display panel including a display portion configured to display an image; and
the light-emitting device according to claim 1 , provided on a back surface of the display panel to emit light onto the display portion.
8. An LED display device comprising
the light-emitting device according to claim 1 ,
wherein the plurality of LED units are classified into K types based on luminescent colors, and
each of picture elements is constituted by the K types of the LED units.