PHASE LOCKED LOOP CIRCUIT

摘要

PURPOSE:To improve the follow-up property of output frequency to objective frequency by comparing the rise edge of an input signal with that of a feedback signal and obtaining phase difference information twice in one period. CONSTITUTION:The title circuit is constituted so that phase difference information is outputted twice in one period from a difference between the leading edge of an input signal measured by a phase comparator 1 and a pulse width measuring circuit 2 and the trailing edge of a feedback signal. Phase control operation is executed by an arithmetic circuit 3 consisting of a microcomputer e.g., based upon the phase difference information. Phase coincidence is executed by outputting a corresponding frequency signal from a variable frequency oscillation circuit 9 in accordance with the computed result.