Ricoh Company, Ltd.

Kyushu Institute of Technology

Seiya Abe

Tsuyoshi Ueno

Yuuki Oka

Tetsuya Satoh

A drive circuitincludes a power source; current control units-to-configured to control the amount of currents supplied to a light emitting element in accordance with a pulse modulation signal; and a calculation unitconfigured to change a duty ratio of a pulse modulation signal. The current control units-to-include a first switching elementconfigured to be switched on/off in accordance with a pulse modulation signal; and a second switching elementconfigured to be switched on/off in accordance with an inversion signal of the pulse modulation signal input to the first switching element; and an inductor. The first switching elementand the inductorare serially connected between the power source and the light emitting element. The second switching elementis connected between groundand a contact pointof the first switching elementand the inductor. The two or more current control units-to-are connected in parallel.

Drive circuit and light emitting device

A drive circuit is configured to supply a current to a light emitting element. The drive circuit includes a plurality of switching elements configured to switch between ON/OFF states with a modulation signal, a capacitor connected in parallel with the light emitting element, and a control module configured to control the switching elements so that a voltage of the capacitor does not become lower than a threshold.

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Fukuoka, Japan

Seiya Abe