Wave-shaping circuit
AssigneeNippondenso Co., Ltd.
InventorsKenji Kinoshita, Katsuhiko Shirai, Takashi Harada
Life of this patent
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Abstract
A wave-shaping circuit comprises a dynamic hysteresis generating circuit for generating a dynamic hysteresis voltage having a certain crest value and whose signal level attenuates at a speed proportional to a number of engine revolutions to mask an ignition noise superimposed on an input signal, and a threshold generating circuit for generating a threshold voltage whose signal level increases/decreases in proportion to the number of engine revolutions to mask an interference noise superimposed on the input signal and to reliably detect a minimum level of the input signal. Either the dynamic hysteresis voltage or the threshold voltage, whichever is higher, is selectively output as a comparison reference signal through a high-level selecting circuit.
Claims8
A wave-shaping circuit for an alternating analog output signal from a sensor which detects rotation speed of an engine, said wave-shaping circuit comprising:
- a comparator for comparing said alternating analog output signal with a comparison reference signal to provide a binary signal corresponding to said alternating analog output signal;
- frequency/voltage converting means for converting said binary signal to a voltage conversion signal which has a voltage value corresponding to a frequency of said binary signal:
- dynamic hysteresis voltage generating means for generating a dynamic hysteresis voltage responsive to said voltage conversion signal, said dynamic hysteresis voltage having a crest value and gradually decreasing over a time interval from said crest value;
- threshold voltage generating means for receiving said voltage conversion signal and generating a threshold voltage whose voltage level changes in proportion to said voltage conversion signal;
- and
- higher signal selecting means for selecting a higher one of said dynamic hysteresis voltage and said threshold voltage and providing said selected higher voltage to said comparator as said comparison reference signal.
A wave-shaping circuit for an alternating analog output signal from a sensor which detects rotation speed of an engine, said wave-shaping circuit comprising:
- a comparator for comparing said alternating analog output signal with a comparison reference signal to provide a binary signal corresponding to said alternating analog output signal;
- frequency/voltage converting means for converting said binary signal to a voltage conversion signal which has a voltage value corresponding to a frequency of said binary signal:
- dynamic hysteresis voltage generating means for generating a dynamic hysteresis voltage responsive to said voltage conversion signal, said dynamic hysteresis voltage having a crest value and gradually decreasing over a time interval from said crest value;
- threshold current generating means for receiving said voltage conversion signal and generating a threshold current whose current level changes in said voltage conversion signal;
- and
- higher signal selecting means for generating a dynamic hysteresis voltage and a threshold voltage from said dynamic hysteresis current and said threshold current, respectively, for selecting a higher one of said dynamic hysteresis voltage and said threshold voltage, and for providing said selected higher voltage to said comparator as said comparison reference signal.
Dependencies are inferred from the claim text.