Vertical tracking circuit

摘要

A regulator coupled to the main supply voltage generates a B+ scan voltage for a horizontal flyback transformer of a horizontal deflection circuit. A supply voltage is developed from a trace voltage in a flyback transformer secondary winding. The supply voltage is indicatiave of the horizontal deflection current amplitude. A decrease in mains supply voltage that cannot be compensated by the regulator, causes a corresponding decrease in the B+ scan and supply voltage and in a horizontal deflection current amplitude. The supply voltage is applied to the series arrangement of first and second resistors and a zener diode. A control voltage developed from the supply voltage, at a junction of the first and second resistors, is applied to a control terminal of a vertical deflection circuit for controlling the amplitude of the vertical deflection current. A decrease in the control voltage produces a greater proportional decrease in the vertical deflection current. The resulting decrease in the supply voltage causes a smaller proportional decrease in the control voltage. This enables the proportional decrease in vertical deflection current to be the same as that of the horizontal deflection current of providing raster width-to-height tracking.