| 摘要 |
PROBLEM TO BE SOLVED: To normally drive ignition without adding a bypass capacitor even in a stricter noise environment.SOLUTION: An ignition device 1 comprises: a positive noise protection circuit 11; and a negative noise protection circuit 12, and clamps a positive voltage and a negative voltage of an alternating-current noise superimposed on a signal input line 10 at clamp levels +Vp and -Vn. If it is assumed that a threshold voltage is Vt, an L-level voltage of an ignition signal is VL, and an H-level voltage thereof is VH, the clamp levels +Vp and -Vn are set to satisfy (Vt-VH)<Vm<(Vt-VL). By so setting, asymmetry between positive and negative waveforms of the clamped alternating-current noise can be improved, a magnitude of an average voltage Vm of the clamped alternating-current noise can be reduced, and it is possible to suppress a fluctuation in a voltage level of the ignition signal on the signal input line 10. |
