Power saving circuit for magnetic focus amplifier using switchable resonance capacitors

摘要

A circuit for driving a focus coil with a constant amplitude current in response to receiving a focus control signal and a horizontal scan rate signal, comprising: (a) a variable capacitance circuit connected to the focus coil to form a series combination of the focus coil and the variable capacitance circuit; (b) an amplifier circuit for receiving and amplifying the focus control signal and in response applying an amplified focus control signal to the series combination; and (c) a control circuit for receiving the horizontal scan rate signal and in response setting a predetermined capacitance of the variable capacitance circuit to obtain minimal voltage of the amplified focus control signal applied to the series combination of the focus coil and the variable capacitance circuit while maintaining constant current amplitude.