Control circuit and process for a cathode ray tube display control apparatus

A control process of a power supply provided for delivering a supply current to an inductor connected in series with a horizontal deflection yoke of a cathode ray tube display for displaying pictures comprised of successive lines, said inductor being the primary coil of a low/high transformer operatively connected for delivering a rectified low-pass filtered biasing voltage to the anode of the display, said low-pass filtering having a first time constant corresponding to the duration of a plurality of pictures, said control circuit comprising the following steps:

• generating a monitoring voltage substantially proportional to said biasing voltage and controlling said supply current so as to keep said monitoring voltage equal to a reference voltage;
• and
• measuring the cathode current supplied to the cathode of the display and adding to said monitoring voltage a compensation voltage corresponding to said cathode current, low-pass filtered with a second time constant corresponding to the duration of a small number of lines and high-pass filtered with said first time constant.

A control circuit of a power supply that delivers a supply current to an inductor of a cathode ray tube display, said inductor being a primary coil of a low/high transformer operatively connected to deliver a rectified low-pass filtered biasing voltage to an anode of the display, said low-pass filtering having a first time constant corresponding to a duration of a small number of pictures, said control circuit comprising:

• feedback circuitry constructed and arranged to generate a monitoring voltage substantially proportional to said biasing voltage and for controlling said supply current so as to keep said monitoring voltage equal to a reference voltage;
• and
• feedforward circuitry constructed and arranged to measure a cathode current supplied to a cathode of the cathode ray tube display and for adding to said monitoring voltage a compensation voltage corresponding to said cathode current, low-pass filtered with a second time constant corresponding to the duration of a small number of lines and high-pass filtered with said first time constant.

A method for delivering a supply current to an inductor of a cathode ray tube display, said inductor being a primary coil of a low/high transformer operatively connected to deliver a rectified low-pass filtered biasing voltage to an anode of the display, said low-pass filtering having a first time constant corresponding to a duration of a plurality of pictures, comprising:

• generating a monitoring voltage substantially proportional to said biasing voltage and controlling said supply current so as to keep said monitoring voltage equal to a reference voltage;
• and
• measuring a cathode current supplied to the cathode of the display and adding to said monitoring voltage a compensation voltage corresponding to said cathode current, low-pass filtered with a second time constant corresponding to the duration of a small number of lines and high-pass filtered with said first time constant.