| 摘要 |
PURPOSE:To prevent an ignition coil from being burned due to a large amount of current applied to a power transistor when the power transistor short-circuits by making wires in resistor bodies arranged in wiring parts of a collector and an emitter of the power transistor break. CONSTITUTION:While connecting one end of an ignition coil to a collector of a power transistor 1, an emitter is provided with a resistor 2 for detecting currents. Further, a base is provided with a current limiting transistor 3 for short-circuiting base signals when the current reaches a specified value. And a resistor 2 is provided with a cut in part of it so that the cut part has a greater resistance value than the rest part. With this constitution, heat which is several ten times of normal condition is generated in the cut part of the resistor 2 when the power transistor 1 short-circuits to melt and break the resistor 2. Accordingly, the power transistor is prevented from being subjected to a large amount of current and the ignition coil is securely prevented from being burned or otherwise damaged.
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