| 摘要 |
<p>PROBLEM TO BE SOLVED: To suppress a radiation noise without using an expensive power supply having a small transient distortion by providing a plurality of dummy loads each being roughly equal to a load of each light emitting element and a means for auxiliary controlling a current to be supplied to each dummy load from a power supply with respect to a driving current to be supplied to the light emitting element. SOLUTION: When an LED 121 is turned off, an LED lightening circuit 28 (n) allows a dummy-side current roughly equal to a driving current to flow through a dummy resistor 33. On the other hand, when the LED 121 is turned on, the current flowing through the dummy resistor 33 is stopped. As a result, even when the turning on and off of the LED 121 is repeated in response to a PWM pulse, a load applied to a constant current power source 28d is stabilized and a transient distortion is not generated. As the dummy load through which the current roughly equal to the driving current complementary flows is provided, it is unnecessary to use an expensive power supply for the LED and it is possible to reduce a noise generated in the power supply for the LED due to the transient distortion.</p> |
