JPS5526789A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To obtain definite synchronous oscillation by making an oscillation frequency synchronism adjustment point depend upon an external synchronous signal input level, by providing a current Miller circuit to the vertical synchronizing saw-tooth wave deflecting signal oscillation circuit of a TV receiver. CONSTITUTION:When 1st switch 16 is OFF while 2nd switch 25 is ON, capacitor C18 is charged up to a constant value and then the output of comparator 19 is inverted, and C18 is charged with switch 25 OFF while switch 16 is ON. At this time, transistor Tr26 turns ON and the plus input terminal voltage of comparator 19 falls from VH at the time of charge down to VL. When the minus input terminal voltage of comparator 19 falls down to approximate VL due to the discharge of C18, an external synchronizing signal is inputted and flows through current Miller circuit 40, causing the plus input terminal voltage of comparator 19 to rise by DELTAVL. Consequently, the output of the comparator is inverted. Timing (t1) or (t2) of this sybchronization depends upon the plus input terminal voltage VL level of the comparator and synchronizing signal output waveform DELTAVL of circuit 40 superposed upon it, so that definite synchronous oscillation will be carried out.