Inductor Current Decoupling-Based Voltage Balancing Method for Multilevel DC-DC Converters Using a Single Current Sensor Measurement

Mitigating voltage imbalances in series or flying capacitors is critical for the reliable operation of multilevel DC-DC converters. Conventional voltage balancing techniques rely on individual voltage measurements for each capacitor, requiring multiple sensors that increase system cost and hardware complexity. To provide a more cost-effective solution, this article proposes a novel voltage balancing method that utilizes a pre-existing inductor current sensor to balance all series and flying capacitor voltages, significantly reducing the number of voltage sensors. The proposed method leverages special inductor current sampling and decoupling techniques to calculate capacitor voltage values, enabling voltage balancing for all capacitors with only a single current sensor. An alternating modulation strategy is introduced to address the case where the decoupling method fails when the duty cycle equals 0.5. The key contribution is a novel voltage balancing method that eliminates the need for additional voltage sensors, and it can be seamlessly integrated into a conventional control system. Additionally, the accuracy requirements of the proposed method for the sensor are also analyzed, and the results show that this method can tolerate certain errors, and common current sensors can meet the requirements. Experimental results from a five-level DC-DC converter prototype validate the effectiveness of the proposed inductor current decoupling-based voltage balancing method.