On Semiconductor Trading, Ltd.

Feng Xu

Yoshio Fujimura

Shinichi Yamamoto

A control circuit of a light-emitting element comprises a rectifying unit (), a switching element (), a transformer () having a first winding (L) which generates a magnetic field using a current controlled by switching of the switching element (), a second winding (L) which is magnetically coupled to the first winding (L) and which generates a current flowing to an LED (), and a third winding (L) which is magnetically coupled to the first winding (L) and which generates a voltage (Sfbk), and an averaging capacitor () which averages a voltage derived by superposing a voltage (Srec) rectified by the rectifying unit () and the voltage (Sfbk), and a voltage averaged by the averaging capacitor () is applied to the first winding (L), so that light is emitted from the LED ().

Control circuit of light-emitting element

A control circuit of a light-emitting element comprises a rectifying unit () which full-wave rectifies an alternating current power supply, a switching element (), a reference voltage generating unit () which generates a reference voltage (Vref), and a comparator () which receives a voltage (Srec) rectified by the rectifying unit (), compares a comparative voltage (Vcmp) corresponding to a current flowing to an LED () and the reference voltage (Vref), and controls switching of the switching element () according to a comparison result, wherein the reference voltage generating unit () comprises a voltage dividing circuit having a transistor (Q) in which a resistance value between a source and a drain is changed according to the voltage rectified by the rectifying unit (), and outputs, using the voltage dividing circuit, the reference voltage (Vref) according to the voltage (Srec) rectified by the rectifying unit ().

Growing community of inventors

Gunma, Japan

Feng Xu