| CPC H05B 45/30 (2020.01) [G02F 1/133603 (2013.01); G02F 1/133612 (2021.01); H01L 25/0753 (2013.01); H05B 45/10 (2020.01); H05B 45/46 (2020.01)] | 8 Claims |
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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.
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