Patent ID: 8390212

Claim:
A light-emitting element driving control circuit comprising: a control circuit configured to turn on or off a transistor based on an input control signal, the transistor being connected in series with a light-emitting element and an inductor connected in series, the transistor being configured to control increase and decrease of a driving current of the light-emitting element; a maximum-value detection circuit configured to detect a maximum value of the driving current; and a control signal generation circuit configured to generate the control signal for turning on the transistor to increase the driving current at a speed corresponding to a level of a power supply voltage when the driving current is smaller than the maximum value and turning off the transistor for a predetermined period to decrease the driving current at a speed corresponding to a level of a forward voltage of the light-emitting element when the driving current reaches the maximum value, wherein the control circuit is configured to turn on the transistor when the control signal becomes one logic level and turn off the transistor when the control signal becomes the other logic level; and the control signal generation circuit is a one-shot pulse circuit configured to output a pulse signal of one logic level as the control signal when the driving current is smaller than the maximum value and output the pulse signal of the other logic level as the control signal for the predetermined period when the driving current reaches the maximum value, wherein the turning on and turning off of the transistor is based on the detection result of the maximum-value detection circuit.