| Abstract |
A method is proposed to estimate the high-frequency inductor current in a half-bridge circuit. Modern wide-bandgap semiconductors such as GaN allow for multi-megahertz switching frequencies. As a result, the frequency content of the inductor current also increases. The conversion delay of an analog-to-digital converter results in a difference between the measured and instantaneous inductor current, especially when the current slope exceeds tenths of milliamps per nanosecond. To overcome this problem, the inductor current is estimated on a digital controller in real-time and the output voltage and current are used for feedback purposes. A slower closed-loop reduced-order observer is developed and extended with an extrapolator to calculate the inter-sample response at a very high frequency. The closed-loop reduced-order observer uses the difference between the measured and estimated output voltage and consequently ensures robustness for model inaccuracies and non-linearities present in the power converter. The extrapolator is running in open-loop but uses the calculated error during the previous update cycle of the closed-loop observer. The proposed estimator is tested in simulation and verified on a field programmable gate array (FPGA). Both the reduced-order closed-loop observer and open-loop extrapolator are merged into a single block to minimize the computational effort in the FPGA. |
