| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a constant-current driving circuit that can always and stably drive all LEDs with a constant current while utilizing PWM control. <P>SOLUTION: The constant-current driving circuit applies a DC voltage generated by boosting the voltage supplied from a power source 13 by means of a boosting circuit 7 to the LEDs 6 in a pulse-like state by controlling the DC voltage by means of a constant-voltage control unit 8. When the operations of the LEDs 6 are controlled by means of a control unit 2 and a PWM 3 and currents flow to the LEDs 6, the constant-voltage control unit 8 controls the magnitude of the voltages applied to the LEDs 6 by acquiring the information about the values of the currents flowing to the LEDs 6 from the potential difference between both ends of a resistor 4 and ON/OFF controlling the voltages applied to the LEDs 6 from the boosting circuit 7 to a high frequency based on the information. Consequently, the currents flowing to the LEDs 6 can be maintained constantly. <P>COPYRIGHT: (C)2006,JPO&NCIPI</p> |
