An accurate phase detection method for realizing ZVS of high frequency inverter in wireless power transmission

Compared with traditional plug-in charging method, wireless power transmission (WPT) is recognized as a more convenient and safer means for electric power transfer. To enhance efficiency of the whole system and reduce EMI, zero-voltage switching (ZVS) of primary inverter should be achieved, while maintaining constant current charging for battery. Consequently, the phase of primary resonant current must be detected precisely, while using frequency modulation and phase shift control (FM-PSC) simultaneously. In this paper, an enhanced phase detection methodology (EPDM) is proposed by using double D flip-flops and a reference signal. A second-order chebyshev low-pass filter is adopted to obtain high dynamic response and steady-state accuracy for resonant current phase detecting. A prototype phase detection board is built up and experimental results convincingly demonstrate the phase angle can be detected accurately. Meanwhile, a 300W WPT prototype is fabricated to verify the validity of the phase angle detection method.