The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Nov. 06, 1990
Filed:
Nov. 30, 1989
Eiji Itaya, Otawara, JP;
Yoshiaki Kumagai, Nishinasunomachi, JP;
Fujitsu Limited, Kawasaki, JP;
Abstract
A phase locked loop for extracting an output signal synchronized with an input signal. The present invention is structured so that a phase locked loop can prevent loss of control due to high frequency noise generated by a level conversion circuit in the feedback loop after oscillation of the VCO has stopped due to a failure. The phase locked loop includes an exchange circuit connected between an output of the phase detector and an input to the feedback loop. When the exchange circuit determines that the output of the phase detector is below a reference voltage, it applies a signal having a frequency which is lower than that of the input signal to the phase detector in place of a signal from a frequency divider in the feedback loop. In such a case, the phase detector outputs a pulse signal which restarts oscillation of the VCO and leads to normal phase control operation.