Phase controlled servo system

摘要

972,256. Automatic temperature control systems. NORTH AMERICAN AVIATION Inc. Jan. 16, 1962, No. 1518/62. Heading G3R. A temperature control system comprises a resistance bridge supplied from a transformer 16 having two resistor arms 19, 15 and two thermistor arms 12, 13 responsive to the temperature, the bridge output being amplified by a transistor 18 and compared in phase with a reference circuit 21, 22 at the junction 20, the voltage at which point is amplified by transistors 28, 29, 60 and converted into a square wave output to drive an amplifier 33 which switches series connected transistors 34-36 for more or less of each negative half cycle of A.C. dependent on the temperature, the transistors 34-36 controlling the half wave current in a heater 3. Negative feed back is provided from transistor 34 by a heater 50 which gives the bridge a more rapid response. Direct current for the operation of the transistors is provided by a circuit 53-59. The output from the transistor 18 is large compared with that received from the circuit 21, 22, hence except at the lowest temperature, the latter's output is swamped.