Patent ID: 9137868
Filing Date: 2015-09-15
Classification: H05B

Abstract:
1. A light emitting element driving circuit comprising: a rectifying circuit configured to output a rectified voltage obtained by providing rectification to an AC voltage; a voltage-dividing circuit configured to output as a reference voltage, a divided voltage obtained by dividing the rectified voltage, the voltage dividing circuit including a first resistor coupled between the rectified voltage and a source of operating potential; a transistor configured to increase a driving current of a light emitting element in accordance with the rectified voltage when turned on and to reduce the driving current of the light emitting element when turned off; a control circuit configured to bring the transistor to an on state or an off state at predetermined intervals and to bring the transistor to the other of the on state or the off state when a voltage according to a current flowing through the transistor increases and becomes the reference voltage; and a voltage-dividing ratio adjustment circuit configured to set a voltage-dividing ratio of the voltage dividing circuit as a first voltage-dividing ratio to reduce the reference voltage when an amplitude of the rectified voltage is larger than a predetermined amplitude and to set the voltage-dividing ratio as a second voltage-dividing ratio to increase the reference voltage when an amplitude of the rectified voltage is smaller than the predetermined amplitude, the voltage dividing ratio adjustment circuit comprising a switch having a control terminal and first and second current carrying terminals, wherein the first resistor has a terminal connected to the first current carrying terminal a of the switch and a second terminal connected to the second current carrying terminal of the switch.