Synchronous Rectification Control for Low-Current Detection

The patent introduces a current detection circuit as an intermediary component that measures the current flowing through the synchronous rectification FET. This circuit includes a sense resistor and operational amplifier that convert the small voltage drop across the low ON-resistance FET into a measurable voltage signal, enabling accurate current detection without requiring high ON-resistance FETs.

The patent replaces direct voltage measurement methods with a dedicated current sensing mechanism using Ohm's law conversion. By introducing a small sense resistor in series with the FET and using an operational amplifier to amplify the resulting voltage signal, the system substitutes indirect voltage detection with a specialized current measurement system that maintains accuracy even with very low resistance values.

The patent implements a control system that uses real-time current detection feedback to automatically adjust the gate drive signal to the synchronous rectification FET. The control circuit monitors the detected current and autonomously determines when to turn off the FET, eliminating the need for external prediction algorithms or complex timing circuits while optimizing efficiency.

The patent establishes a closed-loop feedback system where the current detection circuit continuously monitors the rectification current and feeds this information back to the control logic. This feedback mechanism enables precise control of the FET switching timing, ensuring the FET is turned off exactly when current reaches zero, thereby minimizing body diode conduction losses without requiring complex external control circuits.