Patent ID: 11871492
Assignee: ROHM CO., LTD.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H  Y | IPC H

Claim 10:
11. A light emitting element drive device comprising:
a driving circuit configured to supply a variable drive current to a light emitting unit including one or more light emitting elements, so that the light emitting unit is configured to emit light;
a drive reference voltage generation circuit configured to generate a drive reference voltage defining an upper limit value of the drive current, and supply the drive reference voltage to the driving circuit; and
a specific external terminal,
wherein:
the drive reference voltage generation circuit is operable selectively in a first mode to generate the drive reference voltage regardless of the state of the specific external terminal, or a second mode to generate the drive reference voltage in accordance with a second mode current through the specific external terminal,
the drive reference voltage generation circuit includes a reference current generation circuit configured to generate a reference current commonly in the first mode and in the second mode, a current superimposing circuit configured to generate the second mode current only in the second mode out of the first and second modes, and a current mirror circuit configured to generate an output side current proportional to an input side current, so as to generate the drive reference voltage in proportion to the output side current, and
in the first mode the input side current is equal to the reference current, and in the second mode the input side current is equal to the reference current plus the second mode current.