| 摘要 |
PURPOSE:To continuously correspond to the alteration of an augmentation heater even if the actual resistance of the augmentation heater receives disturbances by controlling the output power from a power control circuit in order that the difference between the respective detected values of voltage and current given to the augmentation heater is kept in a set value. CONSTITUTION:A first computing element 121 generates the difference epsilonr between the detected value nuf/n of a voltage detector 14 and the detected value K.If of a current detector 15 and a second computing element 122 compares the difference epsilonr with a constant voltage VZ generated in a constant voltage diode DZ so a to generate a reference value Vref based on the difference. A third computing element 123 compares the current detected value K.If with the reference value Vref so as to generate an error difference epsiloni from the difference and a pulse width modulating unit PWM 124 controls the pulse width of a switching pulse SP according to the error difference epsiloni. Since power is supplied to a heater 13 by controlling the voltage and the current in order that the heater 13 is always a constant resistance, the temperature of the heater 13 can be kept constant against any disturbance and the deterioration of the heater 13 can be kept the minimum.
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