| 摘要 |
<p>PURPOSE:To exercise high-precision temperature control by detecting a current, flowing through a sensor, by a transistor (TR) and connecting a diode in parallel to the TR. CONSTITUTION:When the side (a) of an AC power source VAC has a negative potential, a current IT flowing through a sensor 3 is the collector current IC of a TR32 and integrated by a circuit of a capacitor 33 and a resistance 34 to be converted into a temperature signal potential VT. The current IT varies with the detected temperature of the sensor 3, so temperature control has high precision. If the power of the power source VAC rises, a potential VCC rises and the current of a current mirror circuit 30 also increases, so a set potential VS decreases to compensate decrease in potential VT. When the side (a) is positive, on the other hand, the current of the sensor 3 flows through the diode 35, so an exactly symmetic AC voltage is applied to the sensor 3, so that the deterioration of the sensor 3 due to polarization is prevented.</p> |
