| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a lighting apparatus using light emitting diodes (an LED lighting apparatus) for achieving luminance adjusting function of each LED without increase in circuit area while the number of components is reduced. <P>SOLUTION: The LED lighting apparatus includes an LED column LB formed by connecting in series LEDs 21 to 2n, a constant current drive circuit 3 for switching the ON and off-states for constant current drive of the LED column LB in synchronization with a pulse width modulation signal EN, and an LED switching circuit provided for each LED 2i in the structure to switch the LED2i between the lighting state and low-luminance state or extinguished state in synchronization with a pulse width modulation signal S<SB>PWM</SB>i (i=1 to n) having the pulse width equal to the pulse width modulation signal EN or less. The LED switching circuit includes an LED control transistor 4i connected in parallel to the LED2i to control the current flowing through the LED2i and a transistor control circuit 5 for switching the LED control transistor 4i to the on-state and off-state in synchronization with the pulse width modulation signal S<SB>PWM</SB>i. <P>COPYRIGHT: (C)2010,JPO&INPIT</p> |
