An Isolated Capacitor-Compensated Current Sensing Method for High-Frequency Resonant Converters

In high-frequency resonant converters, current transformers (CTs) are commonly used to measure the currents of the resonant tank for protection, feedback control, synchronous drive, etc. However, CTs may generate large power losses when measuring high-frequency large currents, which makes it difficult to miniaturize. This letter proposed an alternative isolated current sensing method. The method uses a transformer and a resistor to compensate the resonant capacitor to obtain the current flowing through the capacitor. Compared with the CTs, the proposed method can be much smaller and more efficient, because the current flowing through the transformer is significantly reduced. In the experiments, the transformer size of the proposed method is only 1/7 of that of the CT. The transformer temperature in the proposed method is only 54.7 °C, while that in the CT is as high as 116 °C when simultaneously measuring a 1 MHz, 12.5 A current. Besides, the experimental results show that the proposed method has good linearity and wide bandwidth.