| 摘要 |
PURPOSE:To attain efficient operation even at the broad fluctuation of an input voltage, at the normal operation and preheating, by switching a switch means automatically depending on the presence of a horizontal frequency pulse of a cathode ray tube. CONSTITUTION:In selecting a switch S4 to the P.H position, a load 6 is turned off and a horizontal frequency pulse is switched off. Then, the potential of a base of a transistor (TR) 28 of the siwtch means 27 is lower than the collector potential, the switch means 27 is turned on, the oscillation of an oscillation circuit 31 is started and the oscillation output is impressed to the base of a TR 12 of a control circuit 5. When the switch S4 is operated and the output voltage is going to fluctuate, it is detected at detection resistors 24, 25 and 26, compared with a reference power supply 23 to change a voltage between the collector and the emitter of a TR 19. Thus, even if an input voltage +B is fluctuated, since the conductive period of a switching TR 1 is controlled, preheating is done with a stable output. |
