DETECTING CROSSOVER MOMENTS OF ALTERNATING VOLTAGES.

While controlling converters it is often necessary to synchronize the control circuits with a line voltage or a load voltage, especially in line commutated or load commutated converters. Normally this synchronization signal is noisy. The noise, which is mostly produced by the controlled converter itself or by other converters, leads to disturbances of circuits detecting the crossover moments of the synchronization signal. The application of filters has the effect of a detecting delay, which should be avoided to utilize the full range of the converter. A nonlinear crossover detection circuit is proposed which eliminates disturbances without delaying the detected signal. This type of detection circuit is qualified for synchronizing microcomputers in real-time converter control applications.