JPS5526788A - Oscillation circuit - Google Patents

Abstract

PURPOSE:To prevent the drawing effect of synchronism from varying even if the amplitude of an oscillation output varies, by providing a constant-current circuit and current Miller circuit to the vertical synchronizing saw-tooth-waveform deflecting signal ocsillation circuit of a TV receiver. CONSTITUTION:When switch 16 is OFF while switch 25 is ON, capacitor C18 is charged and when its charge potential reaches a constant value, the output of comparator 19 is inverted to open switch 16 and to close switch 25, so that charge of C18 will be discharged. At this time, transistor Tr 26 conducts and the plus input voltage of comparator 19 falls from Vh in charging down to Vl. According to the discharge of C18, the minus input terminal voltage of comparator 19 falls down to approximate Vl and at this time, an external synchronizing signal is inputted, releasing switch 32. Consequently, a current is flowed to Tr46 of current Miller circuit 41 via constant current circuit 40 to increase the plus input terminal voltage of comparator 19 and the output of comparator 19 is inverted to attain synchronization. This timing depends upon the synchronizing signal output waveform of circuit 41 and even if oscillation output amplitude adjustment resistance 13 is varied in value, the synchronous drawing frequency will not vary.