| 摘要 |
<p>PURPOSE:To enable the early detection of abnormality, by a method wherein, the information of all printing elements on a printing head is transmitted from a detection circuit to a detection circuit of a preceding or succeeding digit, whereby the information of all the printing elements is obtained from a first digit or last-digit detection circuit. CONSTITUTION:Abnormality detection circuits 5 are provided correspondingly to respective LEDs 6. A diagnostic circuit 7 detects an electric current flowing to the LED 6, generates an output of a logical value 1, and adds the output to one input terminal of an anticoincidence circuit 8. To the other input terminal thereof, an output from a corresponding AND gate 3 is added. The anticoincidence circuit 8 generates an output of a logical value 1 at the time of such an abnormality that the LED 6 is lighting in the absence of image data Din or that the LED 6 fails to light in the presence of image data Din and adds the output to one input terminal of an AND gate 9 through an inverter 10. To the other input terminal of the AND gate 9, an output from the abnormality detection circuit 5 of a succeeding digit is added. A power source voltage V of a logical value 1 is applied to the other input terminal of an AND gate 9 of the abnormality detection circuit 5 of a last digit. Thus, the normal operation of all of the LEDs 6 and LED drive circuits results in a logical value 1 outputted from the abnormality detection circuit 5.</p> |
