| 摘要 |
Through operated alternately between a charging phase and a discharging phase, a charge pump converts an input voltage source into a drive voltage for being supplied to a light emitting diode. A current setting unit determines a reference current. A current regulating unit has a current regulating terminal and a feedback detecting terminal. The current regulating terminal is coupled to the light emitting diode so as to control a current flowing through the light emitting diode to be proportional to the reference current. The feedback detecting terminal provides a feedback signal representative of a current regulation characteristic voltage. Based on a difference between the feedback signal and a reference voltage source, an error amplifier generates an error signal. A variable resistance unit is coupled between the input voltage source and the charge pump for adjusting a variable resistance in response to the error signal.
|
