| 摘要 |
PURPOSE:To reduce generated noise by converting a current flowing through a sensor to voltage to peak hold it in the other half wave of a feeding cycle to a heater. CONSTITUTION:When temperature of a heater 2 is low, its impedance ZT is high, consequently collector current IC is small and peak holding voltage VT attains to a value close to DC voltage Vcc for a circuit. When temperature of the heater 2 becomes high the VT drops from the VCC. Further, when a zero pulse generating circuit 20 is not actuated, a TR25 is on, thereby a temperature setting voltage VS is raised to the VCC, and an output VO of a comparator 24 is made to be Low, but when a zero pulse is generated to make VZ to the VCC, the TR25 turns off to lower the the VS. At this time, if VT>VS, the output VO of the comparator is increased to the VCC to trigger the power controlling element 9 through a resistance 26 and the heater 2 is permitted to conduct. When VT<VS,the heater 2 does not conduct. |
