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. 30, 1999
Filed:
Mar. 02, 1998
Yasunori Kurihara, Fukuoka, JP;
Hiroshi Sakata, Tokyo, JP;
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Abstract
A comparison circuit (4) is formed by a Schmidt buffer (4a) which has first and second threshold values and a buffer (4b) whose threshold value is larger than the first threshold value but smaller than the second threshold value. An integrating circuit (3) and the comparison circuit (4) function as a timer circuit which operates in accordance with comparison of the three values. An input signal (IN) decreases from a reference voltage signal (V6). A control signal becomes an H level after a time which is determined by a time constant of the integrating circuit (3) and the threshold value of the buffer (4b), and a detect signal (FO) is outputted after a time which corresponds to a difference between the second threshold value and the threshold value (which is equal to or shorter than a response time of the circuit (4)). During monitoring of a d.c. voltage which is applied to a drive circuit of a semiconductor element by means of a hysteresis operation, chattering of the detect signal is prevented which otherwise occurs despite an unstable hysteresis operation within a monitoring circuit when the d.c. voltage varies above and below a set value in a short period of time.