| 摘要 |
<p>A power supply device which can perform higher efficiency operation is provided by correctly setting a driving voltage of a load circuit. In the power supply device (100) for driving a light emitting diode (300), which is the load circuit, with a constant current, a constant current circuit (22) is provided on a drive path of the load circuit. A charge pump circuit (10), which is a voltage generating circuit, outputs a driving voltage to the light emitting diode (300). A monitoring circuit (30) monitors voltages at both ends of the constant current circuit (22). The monitoring circuit (30) includes a voltage source for generating a threshold voltage which follows voltage fluctuation with which the constant current circuit (22) can stably operate, compares the voltages at the both ends of the constant current circuit with the threshold voltage generated by the voltage source, and outputs the comparison results (Vs) to a control section (24). The control section (24) controls the charge pump circuit (10) based on the output from the monitoring circuit (30).</p> |
