Thomson Consumer Electronics Inc.

Steven C Wetta

Enrique Rodriguez-Cavazos

Lawrence E Smith

Sammy S Henig

The power demand of a dynamic audio load is monitored, for example, by sensing the voltage level of the power supplying the audio load. An audio load control signal corresponding to the power demand is generated. The audio load control signal is advantageously applied to a circuit for producing a side pincushion correction current, for modulating the side pincushion correction current by the audio load demand. The audio load modulated side pincushion correction current is used to modulate a horizontal deflection current in order to compensate for both side pincushion distortion and dynamic audio load induced raster width distortion. A filter network may also be provided for removing high frequency signal components from the audio load control signal.

Audio loading modulated side pincushion correction circuit

An SCR switch of a switch mode power supply is coupled between an unregulated supply voltage and a filter capacitor. A regulator oscillator generates trigger pulses for controlling a switching operation of the SCR switch of the power supply to produce an output supply voltage that energizes a deflection circuit. The regulator oscillator produces trigger pulses that are applied to the SCR switch during both power-up and power-off operation. A resistor coupled between the unregulated supply voltage and the filter capacitor maintains the filter capacitor charged during power-off operation to prevent the trigger pulses from causing the latching operation in the SCR switch throughout the power-off operation. In this way, an audible parasitic vibration sound is not being generated by the power supply during the power-off operation.

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Greenwood, IN, United States of America

Steven C Wetta