| 摘要 |
PURPOSE:To control the heater voltage to a given value, by controlling the control winding of a saturable transformer according to the output of the voltage variation detecting winding provided to the heater transformer. CONSTITUTION:The flyback pulse based on the variation from a variation voltage detecting winding 8 is detected at an average value detection circuit 21 and fed to the base of an error amplifying transistor TR18 via a sensitivity adjusting variable resistor 17. In this case, when the average value of pulse of increased, the base voltage of TR18 increases and the collector voltage is reduced. Accordingly, the base voltage of TR19 is dropped and the collector current is reduced. Thus, the control current flowing to the control winding 7b of the saturable transformer 7 is reduced. Accordingly, the inductance of the controlled winding 7a is increased, the primary current of the heater transformer 2 is reduced and the average value of the heater voltage can always be kept at a constant value. |
