US 12,408,244 B2
Light-emitting element driving circuit
Masaaki Nakayama, Kyoto (JP)
Assigned to Rohm Co., Ltd., Kyoto (JP)
Filed by ROHM CO., LTD., Kyoto (JP)
Filed on Sep. 19, 2023, as Appl. No. 18/469,880.
Application 18/469,880 is a continuation of application No. PCT/JP2022/009095, filed on Mar. 3, 2022.
Claims priority of application No. 2021-049795 (JP), filed on Mar. 24, 2021.
Prior Publication US 2024/0015864 A1, Jan. 11, 2024
Int. Cl. H05B 45/10 (2020.01); H05B 45/325 (2020.01)
CPC H05B 45/10 (2020.01) [H05B 45/325 (2020.01)] 9 Claims
OG exemplary drawing
 
1. A light-emitting element driving circuit comprising:
a reception terminal and a transmission terminal connectable to an external controller;
a communication circuit configured to
receive a reception signal from the controller via the reception terminal and
transmit a transmission signal to the controller via the transmission terminal;
a dimming signal generator configured to generate a dimming signal;
a constant-current circuit configured to
pass a current in a light-emitting element and
be turned on and off based on the dimming signal;
a first buffer provided between the transmission terminal and the communication circuit, with an output side of the first buffer connected to the transmission terminal and an input side of the first buffer connected to the communication circuit; and
a determination circuit configured to determine whether the controller is connected or not based on a first signal at the output terminal of the first buffer and a second signal at the input terminal of the first buffer,
wherein
if the determination circuit determines that the controller is connected, the communication circuit is enabled to process a signal received via the reception terminal, and the dimming signal generator generates the dimming signal based on a command from the communication circuit, and
if the determination circuit determines that the controller is not connected, the communication circuit is disabled from processing the signal received via the reception terminal, and the dimming signal generator generates the dimming signal based on a pulse signal fed to the reception terminal or the transmission terminal.