Design and application of TEC controller Using in CCD camera

Thermoelectric cooler (TEC) is a kind of solid hot pump performed with Peltier effect. And it is small, light and noiseless. The cooling quantity is proportional to the TEC working current when the temperature difference between the hot side and the cold side keeps stable. The heating quantity and cooling quantity can be controlled by changing the value and direction of current of two sides of TEC. So, thermoelectric cooling technology is the best way to cool CCD device. The E2V's scientific image sensor CCD47-20 integrates TEC and CCD together. This package makes easier of electrical design. Software and hardware system of TEC controller are designed with CCD47-20 which is packaged with integral solid-state Peltier cooler. For hardware system, 80C51 MCU is used as CPU, 8-bit ADC and 8-bit DAC compose of closed-loop controlled system. Controlled quantity can be computed by sampling the temperature from thermistor in CCD. TEC is drove by MOSFET which consists of constant current driving circuit. For software system, advanced controlled precision and convergence speed of TEC system can be gotten by using PID controlled algorithm and tuning proportional, integral and differential coefficient. The result shows: if the heat emission of the hot side of TEC is good enough to keep the temperature stable, and when the sampling frequency is 2 seconds, temperature controlled velocity is 5°C/min. And temperature difference can reach -40°C, controlled precision can achieve 0.3°C. When the hot side temperature is stable at 25°C, CCD temperature can reach -23°C, and thermal noise of CCD is less than 1e-/pix/s. The controlled system restricts the dark-current noise of CCD and increases SNR of the camera system