Buck-Boost Converter Boot Refreshing Mode for Ripple Reduction

The patent introduces an intermediary boot refreshing mode between buck and boost modes. When the converter detects that input and output voltages are close (within a threshold range), it transitions to this intermediate mode which performs boot strap capacitor refreshing operations. This prevents direct mode switching that would cause high output ripple and efficiency loss, while still enabling relatively fast transitions through controlled boot refreshing pulses.

The patent implements dynamic mode switching based on real-time voltage monitoring. The control circuit continuously compares input and output voltages and dynamically adjusts the operating mode accordingly. When voltages are close, it activates the boot refreshing mode; otherwise, it operates in standard buck or boost mode. This dynamic adaptation maintains output voltage stability without requiring permanently complex circuitry.

The patent employs feedback control through PWM (pulse width modulation) that monitors the switching frequency and adjusts duty cycles to maintain operation above audible thresholds. The control circuit receives feedback about the current operating state and dynamically adjusts switching parameters to prevent frequency drop into the audible range, thereby eliminating acoustic noise while maintaining acceptable efficiency through optimized duty cycle control.