| 摘要 |
PURPOSE:To suppress the secondary voltage of an ignition coil from being generated by discharging charges charged in a charging/discharging circuit at the predetermined time constant when an abnormality of an engine is detected so that the base current of darlington power transistors can be gradually decreased. CONSTITUTION:Darlington power transistors Tr29A, Tr29B are operated by a signal from an ignition control unit via a switching circuit 27, thereby the current through ignition coils 14A, 14B is controlled to generate sparks on ignition plugs 15A, 15B. The base voltage is applied to bases of the said Tr29A, Tr29B via a voltage feed switch circuit 30. When an abnormality is detected by a fail safe detection circuit (not shown in the figure), a signal ST is made invalid, a transistor Tr4 is turned on, a transistor Tr2 is turned off, the voltage feed from the said circuit 30 is shut off, on the other hand, capacitors C3, C4 are discharged, and the base current of the Tr29A, Tr29B is decreased gradually. |
