| 摘要 |
PURPOSE:To keep a high voltage, etc. of a cathode ray tube constant even when a horizontal frequency of an input signal is different by taking out a pulse voltage from a collector pulse of a horizontal output transistor to rectify and operating a chopper type switching power source circuit so as to keep the rectified voltage constant when the horizontal frequency is changed. CONSTITUTION:A chopper type switching power source circuit consists of a chopper transformer T1, a switching transistor Q1, a controlling transistor Q2, and an error detection amplifying transistor Q3. A horizontal pulse obtained from a flyback transformer T2 is applied to a base of the transistor Q1 through a resistance R3 and a diode D2 and a switching operation is carried out synchronously with a horizontal oscillating frequency. A collector pulse outputted from a horizontal output transistor Q4 is rectified and smoothed by a diode D4 and a capacitor C4 and this voltage is compared with a reference voltage determined by a zener diode D3, by the difference, the quantity of an operation of the Q2 is controlled, thereby, even if the horizontal frequency is changed, a base current of the Q1 is controlled and a voltage of a point D is kept constant. |
