US 12,082,319 B2
LED driving device, lighting device, and vehicle-mounted display device
Ryosuke Kanemitsu, Kyoto (JP); and Koji Katsura, Kyoto (JP)
Assigned to Rohm Co., Ltd., Kyoto (JP)
Appl. No. 17/778,525
Filed by Rohm Co., Ltd., Kyoto (JP)
PCT Filed Sep. 29, 2020, PCT No. PCT/JP2020/037019
§ 371(c)(1), (2) Date May 20, 2022,
PCT Pub. No. WO2021/106360, PCT Pub. Date Jun. 3, 2021.
Claims priority of application No. 2019-214181 (JP), filed on Nov. 27, 2019.
Prior Publication US 2023/0040250 A1, Feb. 9, 2023
Int. Cl. H05B 45/30 (2020.01); H05B 45/10 (2020.01); H05B 45/325 (2020.01); H05B 45/345 (2020.01); H05B 45/46 (2020.01)
CPC H05B 45/345 (2020.01) [H05B 45/10 (2020.01); H05B 45/325 (2020.01); H05B 45/46 (2020.01)] 13 Claims
OG exemplary drawing
 
1. An LED driving device comprising:
a DC-DC controller configured to control an output stage configured to generate from an input voltage an output voltage to supply the output voltage to an anode of an LED;
a constant current circuit configured to generate an LED current passing through the LED;
an LED terminal configured to be connected to a cathode of the LED;
a reference voltage generator configured to generate a reference voltage;
an LED current setter; and
a current setting terminal configured to be connectable to an external resistor,
wherein
the DC-DC controller is configured to perform control such that a voltage at the LED terminal remains equal to the reference voltage,
the reference voltage generator is configured to generate the reference voltage such that, as a set value of the LED current set by the LED current setter decreases, the reference voltage decreases,
the LED current setter includes a current generator configured to generate a first current in accordance with a resistance value of the external resistor, the LED current setter being configured to generate the current setting reference voltage in accordance with the first current,
the reference voltage generator includes a second resistor through which a second current passes in accordance with the first current, and
the reference voltage appears at one terminal of the second resistor.