| 摘要 |
A switched mode power supply and horizontal deflection system comprises a first oscillator circuit for generating horizontal rate synchronizing trigger pulses, having a voltage supply input terminal; a horizontal output stage; and, a second oscillator circuit for driving the output stage, operable at a horizontal rate responsive to the trigger pulses and free running at a different rate absent the trigger pulses. An overcurrent protection circuit for the horizontal output stage responds to an overcurrent condition which can occur during free running of the second oscillator circuit. A flyback transformer is coupled to the horizontal output stage and has a secondary side voltage supply coupled to the voltage supply input terminal for energizing the first oscillator circuit during operation of the output stage. An energy storage device, for example a large value capacitor, is coupled to the voltage supply input terminal for energizing the first oscillator circuit for a period of time after the horizontal deflection system is deactivated. The capacitor and a resistor form a timing network for the first oscillator circuit. The first oscillator circuit continues generating synchronizing trigger pulses and prevents operation of the second oscillator circuit at the free running frequency. A quick charging path for the energy storage device, for example a Zener diode in parallel with the resistor, minimizes operating time of the second oscillator circuit at the free running rate prior to the initiation of the synchronizing trigger pulses when the power supply and horizontal deflection system is activated.
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