| 摘要 |
<p>PURPOSE:To enhance the speed of temperature rise when the set temperature is changed to a higher temperature while the set temperature is held, by making the conduction of a bidirectional switching element bidirectional when the difference between the set temperature and a detected temperature is larger than a certain value. CONSTITUTION:At the beginning of power supply, the conduction of a bidirectional switching element 3 is made bidirectional by operations of a self-holding means 34 and a timing device 36, and full-wave power supply to a heater 2 is performed to raise the heater to a maximum temperature; and after a certain time, the conduction of the element 3 is made unidirectional to hold the set temperature. If the set temperature is changed to a higher temperature while the set temperature is held, the difference between the set temperature and a detected temperature is larger than a certain value. Then, the half-wave power supply is switched to the full-wave power supply to raise the temperature to the changed set temperature, and thereafter, the changed set temperature is held by the half-wave power supply. Thus, the speed of temperature rise is enhanced when the set temperature is changed to a higher temperature while the set temperature is held.</p> |
