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Sensor and Sensor-less Control

T30.2 - Gradient-Descent Sensorless Current Balancing for Multiphase LLC Converters

Thursday, March 26, 2026
8:40 AM - 9:00 AM CT
Location: 217B
This invention addresses current imbalance in multi-phase LLC converters using charge-based hysteretic control, with applications in battery chargers. It leverages existing capacitor voltage sensing inherent in hysteretic control to estimate average resonant currents without dedicated current sensors. By analyzing voltage slopes between predefined thresholds, the system infers phase currents and inputs them into a cost function, optimized via a gradient descent algorithm. The controller dynamically adjusts hysteretic band window sizes to minimize the cost, balancing currents while preserving total output current through an invariance transformation. This model-free, adaptive outer loop operates in real time, reducing current imbalance and output ripple. Unlike prior research that relies on extra hardware, complex trigonometric calculations, or additional sensing, this approach uses minimal components and is fully implementable in real-time digital logic. Applications include EV chargers, renewable energy systems, telecommunications, aerospace, and data centers.