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:
Aug. 24, 1999
Filed:
Sep. 27, 1996
Atsuo Yamaguchi, Tokyo, JP;
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Abstract
A PLL circuit is disclosed which can achieve a locked state in a short time. The PLL circuit has a phase comparator, a loop filter and a voltage controlled oscillator. The phase comparator is provided with frequency adjusting (or matching) circuits that are operative to charge the loop filter when it is detected that an oscillation frequency of the voltage controlled oscillator is lower than a frequency of an input signal, so as to increase the oscillation frequency of the voltage controlled oscillator, until it is detected that an oscillation frequency of the voltage controlled oscillator is higher than the frequency of the input signal. Similarly, the loop filter is discharged when it is detected that an oscillation frequency of the voltage controlled oscillator is higher than a frequency of an input signal, so as to decrease the oscillation frequency of the voltage controlled oscillator, until it is detected that an oscillation frequency of the voltage controlled oscillator is lower than the frequency of the input signal. The phase comparator is further provided with phase adjusting (or matching) circuits for adjusting a phase of an output of the voltage controlled oscillator to a phase of the input signal after the oscillator frequency of the voltage controlled oscillator is adjusted to the frequency of the input signal. Thus, a time required to adjust the oscillation frequency of the voltage controlled oscillator can be considerably reduced.