Patent ID: 8638041

Claim:
A light-emitting element drive circuit system for driving a light-emitting element, comprising: a current circuit section that drives the light-emitting element at a preset drive current value; and a current value setting section that sets the drive current value so that the drive current value is changed in a curve or linearly with a predetermined slope during a preset transition period from a first current value to a second current value that is not equal to the first current value, and changed in a curve or linearly with a predetermined slope during a preset transition period from the second current value to a third current value that is not equal to both the first current value and the second current value, wherein the current value setting section sets the drive current value so that the drive current value is changed from the first current value to the second current value during a preset transition period starting from a first time point, maintained at the second current value during a period from a second time point to a third time point, the second time point being a time point that occurs after elapse of the preset transition period from the first time point, and changed from the second current value to the third current value during a preset transition period starting from the third time point, wherein the current value setting section comprises: a first calculation circuit that outputs a first serial current-setting data having a current value that is changed from a first current value to a second current value during a period from the first time point to the second time point, changed from the second current value to the first current value at the second time point, maintained at the first current value during a period from the second time point to the third time point, changed, during a period from the third time point to a fourth time point, from the first current value to a fourth current value that is not equal to all of the first current value, the second current value, and a third current value, and changed from the fourth current value to the first current value at the fourth time point; a second calculation circuit that outputs a second serial current-setting data having a current value that is maintained at the first current value from the first time point to the second time point, changed from the first current value to the second current value at the second time point, maintained at the second current value from the second time point to the fourth time point, and changed from the second current value to the third current value at the fourth time point; and an adder circuit that serially adds together the first serial current-setting data for respective time points and the second serial current-setting data for corresponding time points.