| 摘要 |
<p>PURPOSE:To control quickly and accurately the temperature to a set level by detecting a temperature range which includes a temperature to be detected among plural temperature ranges and controlling the electric power supplied to a heater by those temperature ranges. CONSTITUTION:A light-up ratio control circuit 3 detects an range including the temperature of a heater 1 by the output fed from FF9a-9e. In other words, it is detected that a certain prescribed range includes the temperature of the heater 1 when the outputs of FF9b, 9d and 9a are set at L levels with the outputs of FF9e and 9c set at H level respectively. The circuit 3 controls the light-up ratio according to each area. That is, a prescribed level is decided when the temperature of the heater 1 exists in a certain corresponding area. While an extremely high or low temperature is decided when the temperature of the heater 1 exists in another range. Thus the supply of power is stopped to the heater 1. In such a way, the temperature of the heater 1 can kept at reference level (a), i.e., a set temperature. This can reduce the ripple of temperature.</p> |
