| 摘要 |
Circuitry to control a power supply of a degaussing coil of a cathode ray tube, said degaussing coil is coupled to a main voltage supply through a switching device the circuitry has inputs coupled to a direct source of current of a switched mode power supply, the switched mode power supply comprises a switched mode transformer with primary windings coupled to the main source of voltage, and secondary windings and the switched mode power supply is switched in a first range of frequencies when the power supply is in a "standby" mode and in a second range of frequencies when the power supply is in an "on" mode wherein said circuitry comprising a detecting circuit which detectes a change in the range of switching frequencies when the power supply is switched from standby to on, the detecting circuit having an input coupled to a direct current source being downstream of a primary winding of the switched mode transformer and an output coupled to an input of a control circuit of the switching device the control circuit, having an output to carry an output signal having an "on" state and an "off" state, the "on" state lasting for a predetermined duration after a change in a value present at the output of said detection circuit, the change occurring when the power supply is switched to the "on" mode, in the "on" state of said signal at the output of said control circuit, the switching device is on and current coming from the main is flows through the degaussing coil and in the "off" state of said signal the switching device is off and no current is circulates in the degaussing coil.
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