| 摘要 |
PURPOSE:To correctly perform the protective operation with a simple circuit structure without being affected by the ambient temperature by measuring the continuation time of the preheated nonstert state with a timer circuit and switching a circuit to the dimming mode. CONSTITUTION:A saturation detecting circuit DET is removed, and a serial circuit of a mode switch SW and a resistor R14 is instead connected between the connection point of a resistor R2 and a capacitor C2 constituting a time constant circuit and the base of a transistor Q5. The preheated nonstart state is detected by a detecting means Q4, timer means R2 and C2 detect that the preheated nonstart state is continued for a preset time or longer, inverter means Q1 and T1 are set to the dimming mode, thereby a circuit can be correctly protected without being affected by the ambient temperature. |
