Design and Evaluation of a Low-Cost High-Performance Σ-Δ ADC for Embedded Control Systems in Induction Heating Appliances

The advantages of resonant power converters, such as high efficiency and high power density, make them a suitable solution for domestic applications such as induction heating (IH) cookers. The control systems of these appliances require performing accurate and smooth power control while assuring the safety of the power devices. In order to accomplish these tasks, it is necessary to have information about the target output power, which is selected by the user, and the specific parameters of the output current. In this paper, a single-bit second-order sigma-delta (Sigma-Delta) analog-to-digital converter (ADC) is proposed to measure the magnitude of interest in resonant power converters. An optimized digital low-pass filter architecture is proposed to extract the output current from the digitized bit stream. This filter improves the accuracy while having low logic-resource consumption. The proposed ADC has been verified using a resonant inverter applied to the IH cooktop application. The inverter switching frequency is in the range of 40-80 kHz. A statistical analysis of the final measurement system has been performed to assess the system accuracy. The proposed system achieves good accuracy in the inverter operating range.