Duty-cycle controlled inverter power supply for a television receiver

A television receiver, inverter power supply with duty-cycle control, comprising:

• a deflection winding;
• a deflection generator for developing scanning current in said deflection winding;
• a source of direct voltage;
• a power transformer including a primary winding and a supply winding;
• controllable switching means having a main current path coupled to said source and to said primary winding so that said on-off switching of the conduction in said main current path develops an alternating polarity voltage across said primary winding, thereby developing a supply voltage across said supply winding;
• control means coupled to said switching means for producing said on-off switching of the conduction in said main path, including a synchronizing transformer with a first winding that has said deflection current flowing therein to magnetically saturate the core of said synchronizing transformer during the entirety of each deflection cycle except during intervals within each deflection cycle that encompass the zero-crossover instants of the deflection current to develop across a second winding of said synchronizing transformer switching signals for said controllable switching means so as to synchronize the zero-crossover instants of said power transformer alternating polarity voltage to corresponding zero-crossover instants of said deflection current;
• means for developing a signal representative of the current in said main path;
• and
• means coupled to said control means and responsive to said main path current representative signal for adjusting the duty cycle of said on-off switching so as to oppose changes in the amplitude of the current in said main path.

A deflection synchronized switching power supply for a television display system, comprising:

• a deflection winding;
• a deflection generator coupled to said deflection winding for generating scanning current in said deflection winding during a deflection interval;
• a power transformer having primary and supply windings;
• a source of direct voltage coupled to said primary winding;
• signal means coupled to said deflection generator for developing first and second control signals indicative of the occurrence of the zero-crossover instants of said scanning current within the trace and retrace intervals, respectively, of said deflection interval;
• controllable switching means having first and second main current paths coupled to said power transformer;
• control means coupled to said switching means and responsive to said first and second control signals for alternately switching said first and second main current paths into conduction near a respective one of said zero-crossover instants so as to develop an alternating polarity rectangular-wave voltage across said transformer primary winding for generating a supply voltage across said supply winding;
• means for developing a control signal representative of the current in at least one of said first and second main current paths;
• and
• means coupled to said control means and responsive to said control signal for adjusting the duty cycle of said rectangular wave voltage so as to oppose changes in the magnitude of the current in said one main current path.