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A Novel Synchronous Rectification With Directly Frequency Tracking for Automotive Alternator

Few practical products of synchronous rectification (SR) in the automotive alternator has been reported, though the driving technology of SR is abundant. Continuously and statistically changing switch frequency caused by rotor speed poses a significant challenge to the driving circuit design under the specified application area. In this article, a directly frequency tracking (D-FT) method is first proposed to ensure the switching tube's safe conduction time adapted to the rotor speed, making the SR immune to circuit oscillation or spurious ringing. The proposed self-driven circuit generates correct gate driving signals requiring no additional sensing circuits or sensors for detecting rotor speed. A hardware algorithm based on the D-FT method is built, which is convenient to implement to other kind of alternators and systems. This method is verified by prototype simulation and practical tests under the alternator test bench. A six-phase full bridge is trial-manufactured after the driver chip's tape out and performs well under 0–150 A output current and 0–18 000 r/min rotor speed. The test results show that the Verband der Automobilindustrie standard efficiency of the proposed rectifier obtains an 8% improvement compared to that of the conventional diode rectifier.