Commutated scr regulator for a horizontal deflection circuit

Abstract

A retrace pulse voltage is applied to a first flyback transformer winding of a horizontal deflection circuit to develop retrace pulse voltages across other flyback transformer windings. Second and third windings of the flyback transformer are coupled in a series arrangement with a controllable switch across a source of input voltage. A regulator control circuit turns on the SCR at a controllable instant within the trace interval of each deflection cycle to generate input current in the series arrangement. When the retrace pulse voltage is applied to the flyback transformer first winding, the input current begins to decrease in magnitude, commutating off the SCR within the retrace interval. The leakage inductance associated with the series arrangement of flyback transformer second and third windings and the total reflected retrace pulse voltage developed by the two windings determine the instant within retrace that the SCR is commutated off. The third winding is loosely coupled with the first winding, whereas the second winding is tightly coupled with the first winding. By varying the second to third winding turns ratio, the amount of leakage inductance in the series arrangement may be varied without significantly altering the magnitude of the total reflected retrace pulse voltage.