| 摘要 |
PURPOSE:To stabilize a current supplied to a focusing coil, by using sawtooth voltage for electrostatic deflection, and jointly using a comparative waveform of a chopper circuit for controlling the focusing coil, and executing pulse width duty control. CONSTITUTION:Sawtooth voltage for horizontal deflection synchronizing with a horizontal driving pulse applied to an input terminal is generated by a generator 2 and is applied to deflecting electrodes 6, 7. On the other hand, supply voltage applied to an electric power source input terminal 12 is applied to a focusing coil 15 through a transistor whose collector is grounded by a damper diode 22, and a filter formed by a choke coil 23 and a smoothing capacitor 24. The coil 15 is connected to a detecting resistance 16, and detecting voltage is compared with a reference voltage source 17, and is applied to one input terminal of a comparator. To the other terminal of the comparator, an output of the generator 2 is applied, and a comparative waveform output is applied to the base of the transistor 21 through a current limiting resistance 25, by which a negative feedback operation is executed. |
