LLC Resonant Converter Ripple Compensation Circuit

The patent replaces the analog filtering circuit (mechanical/electrical system with physical components like resistors, capacitors, and inductors) with a digital filtering approach implemented through a microcontroller. The digital filter uses software algorithms to achieve the same ripple suppression function without requiring additional physical filtering components, thereby reducing fabricating cost and layout space while maintaining the ability to filter low frequency ripple.

The patent implements a feedback mechanism where the microcontroller monitors the output voltage and uses this information to dynamically adjust the gain of the LLC input voltage at low frequency. By continuously measuring the actual output and comparing it with the reference, the system can apply corrective gain adjustments without causing excessive phase shifts that would lead to instability. The feedback loop ensures that gain increases are applied in a controlled manner that maintains system stability while still suppressing low frequency ripple.

The patent changes the approach from using a traditional analog gain filter that modifies zero and pole locations to a digital gain adjustment method. The microcontroller implements gain control by digitally scaling the PWM duty cycle based on the error signal, which increases low frequency gain without introducing the phase shifts associated with analog filter zeros and poles. This parameter change in the control method achieves the desired gain increase while maintaining system stability.