High precision temperature control system for an Oven-Controlled crystal oscillator

Abstract

Environmental temperature is a highly influential factor regarding the stability of the crystal oscillator frequency. Thus, a high precision temperature control system is critical for improving the frequency stabilization of crystal oscillators. This paper proposes a temperature control system, including a high sensitive thermistor, precision reference voltage source and an instrumentation amplifier for the temperature measurement and preamplifier. System level MCU— MSC1210 acts as a main controller, and a novel way of the “interrupt + ribbon” strategy is adopted to realize real-time task scheduling. The PID controller program is crafted with the help of the “anti-integral saturated” and “bumpless transfer” algorithms. The cascade control system with the heating current of negative feedback is then realized using the triode tube consumption heating style. The results show that the temperature and fluctuation of heat voltage have almost no effect on the heating current when the heating system voltage fluctuates between 2.2 ~ 8V. Within those parameters, the temperature deviation remains within 0.01 degrees. Thus it can be seen that the high-performance temperature control system has a high anti-interference capability and a similarly high level of accuracy.