Phase-locked loop synchronization with gated control

Many utility powered applications require synchronization with the line voltage for the operation of the controller. Such synchronization is typically accomplished using some phase-locked loop (PLL) mechanism, which serves to estimate the real time phase angle of the line voltage. This phase estimate then serves to determine signal timing for power control devices. Common phase detection methods using multipliers or zero-crossing detection require subsequent low-pass filtering for averaging purposes, resulting in longer system response, and increases in transient losses. A method is proposed on the basis that, for a sinusoidal reference signal, during the time interval of most significant slope, this signal is taken as instantaneously approximately proportional to it´s phase angle. A gating mechanism measures and acts on the instantaneous difference between the incoming signal and the locally synthesized signal of equal amplitude, which results in a faster estimate of the line phase angle and frequency