7 Summary and Adaptations

A resistive heating element can be driven with constant power to deliver a fixed temperature, without needing to measure the temperature. The closed loop, constant power example design presented here maintains the measured power in the load to within ±3.0% of the set level across power levels and variations in load resistance due to temperature changes. In this case ±3.0% variation in power corresponds to a temperature tolerance of about ±0.15°C at lower power (1W) and about ±0.75°C at higher power (9W). The temperature tolerance can vary depending on he heating element used. but can be calibrated during product design.

If the input voltage range, the heater resistance or the power required means higher current or a boost or buck-boost topology are required, then other I²C controlled converter devices can be used. Alternatively, a standard converter can be adjusted by summing a filtered PWM signal into the FB node.