JPS5781601A - Digital error signal detector - Google Patents

Abstract

PURPOSE:To reduce the noise, by providing a comparison pulse generating means, which corrects noise pulses of a narrow width included in a pulse width modulation signal into pulses of a width wider than that of noise pulses but narrower than that of normal pulses, and an adding circuit. CONSTITUTION:A circuit where a diode 17 as an adder is connected to the output of a monostable multivibrator as a comparison pulse generator 13 is added between an input terminal 11 of a pulse width modulation signal (g) and a low- pass filter 9. An output signal (m) of the monostable multivibrator 13 is operated by the rise of the input signal (g) to generate a pulse width Tm determined by a capacitor 24 and a resistance 27. The pulse width Tm is wider than the width T2 of noise pulses included in the signal (g) and is narrower than a width T1 of normal pulses. A K signal obtained by adding signals (m) and (g) is inputted to a filter 9 by the diode 17. The width T2 of noise pulses included in the signal (g) is corrected to the width T1. Thus, the influence of the pulse width T2 upon an output (h) of the filter 9 is weakened to reduce the noise.