| 摘要 |
PURPOSE:To make stable the heater voltage, by comparing the average variation voltage of a heater transformer with a given voltage obtained at a constant voltage diode, and applying the voltage difference to the control winding of a saturable transformer. CONSTITUTION:The flyback pulse based on various variance produced on a variation voltage detecting winding 8 is detected at an average detection circuit 21 and fed to the base of an error amplification transistor TR18 via a sensitivity adjusting variable resistor 17. In this case, when the average value of the pulse increases, the base voltage is increased and the collector voltage is decreased. Accordingly, the base voltage of TR19 is decreased and the collector current is decreased. Thus, the control current flowing to the control winding 7b of the saturable transformer 7 is decreased. Accordingly, the inductance of the controlled winding 7a is increased and the primary current of the heater transformer 2 is reduced. Thus, the average value of the heater voltage can always keep a constant value. |
