| 摘要 |
PURPOSE:To prevent breakdown of a preheating controlling transistor by connecting a first diode, with its forward direction reversed, in parallel to the preheating controlling transistor while connecting a second diode, with its forward direction equalized to that of the first diode, in series to the first diode. CONSTITUTION:A first diode 17 is connected, with its forward direction reversed, to a transistor 13 while a second diode 18 is connected, with its forward direction equalized to that of the first diode 17, to the first diode 17. When a capacitor 4 is charged with electricity in the direction of such polarity as illustrated, it causes electric discharge by means of the diode 17 via a center tap in the primary coil 6 of an oscillating transformer 5 and thence via one of transistors, and consequently the voltage of the capacitor 4 is added between the base and emitter of the transistor 13 but it is not impressed on the transistor 13. Also when the capacitor 4 is charged with electricity in the direction of polarity against such polarity as illustrated, it is charged with electricity via the diode 18, and consequently the voltage of the capacitor 4 is added between the collector and emitter of the transistor 13 but it is not impressed on the transistor 13. This can prevent the breakdown of the preheating controlling transistor 13. |
