INVERTER UNIT AND LIGHTING DEVICE EMPLOYING INVERTER UNIT

摘要

PURPOSE:To sustain the oscillation of inverter circuit stably by detecting the start of oscillation of inverter circuit and then stopping the operation of a surge preventing circuit or regulating the operation of a switching element for stopping oscillation. CONSTITUTION:Upon turn ON of power, a voltage is induced across a surge preventing circuit 5 by the charging current for a main smoothing capacitor 4 and thereby an oscillation stopping transistor 17 is turned ON while a main switching transistor 10 is turned OFF. Upon subsequent voltage drop of the surge preventing circuit 5, the oscillation stopping transistor 17 is turned OFF while the main switching transistor 10 is ready to be turned ON thus starting oscillation in an inverter circuit 9. Start of oscillation is detected based on a voltage appearing on the capacitor 19 and a LED 24 emits light to turn a phototransistor 27 ON and then turn a thyristor 7 ON thus stopping the operation of the surge preventing circuit 5.