Abstract: A phase shift control method for a charging circuit is disclosed. The charging circuit includes a primary conversion circuit, a first secondary conversion circuit, and a second secondary conversion circuit. The controller causes a phase angle difference ? between an ON/OFF waveform of power switches in the primary conversion circuit and an ON/OFF waveform of power switches in the first secondary conversion circuit. The controller collects an output current (Io1) and an output voltage (Vo1) of the first secondary conversion circuit, collected by the first secondary current collector and the first secondary voltage collector, carries out comparison and calculation between the collected output current and output voltage and a preset output current and output voltage, and adjusts the magnitude and positive and negative of the phase angle difference ? according to the comparison result.

Abstract: An automatic tracking apparatus is provided for maintaining alignment of music rolls in player organs and player pianos using an improved, air pressure controlled, sensing and control device. More particularly this system incorporates an air pressure sensing device utilizing a piston/cam controlled pendulum to operate a pneumatic alignment device.