US4549099A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Periodic signal detecting circuit including comparator circuit with variable threshold and varying time constant
Assignee: Denso Corp
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Filing: 1983-04-22
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Granted: 1985-10-22
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Expires: 2003-04-22
Abstract
Abstract A periodic signal detecting circuit including a comparator compares a threshold voltage varying with a time constant and an engine speed signal from an electromagnetic pickup coil so as to generate an output. The time constant is varied in accordance with the switching operation of a diode switch which is turned on and off in accordance with the comparator output. When the switch is in off condition, the threshold voltage is varied with the time constant which is changed successively.
Inventors
- 👤 Takashi Yamada
- 👤 Mamoru Shimamoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 02:54
CPC Classifications
H; H03; H03K; H03K5/00; H03K5/01; H03K5/08; H03K5/082; H03K5/086; H03K5/153
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
110 words
A periodic signal detecting circuit comprising: a comparator circuit for comparing an input periodic signal and a threshold voltage and generating an output changing from one state to another state when said signal exceeds said threshold voltage and changing from said another state to said one state when said signal decreases below said threshold voltage; and a threshold voltage generating circuit responsive to said comparator circuit output to generate said threshold voltage, said threshold voltage generating circuit including time constant setting means for varying said threshold voltage with a predetermined time constant and means responsive to said change of state of said comparator circuit output to vary said time constant.
Claim 2
Dependent Claim
110 words
A periodic signal detecting circuit comprising: a comparator circuit for comparing an input periodic signal and a threshold voltage and generating an output changing from one state to another state when said signal exceeds said threshold voltage and changing from said another state to said one state when said signal decreases below said threshold voltage; and a threshold voltage generating circuit responsive to said comparator circuit output to generate said threshold voltage, said threshold voltage generating circuit including time constant setting means for varying said threshold voltage with a predetermined time constant and means responsive to said change of state of said comparator circuit output to vary said time constant.
Claim 3
Dependent Claim
73 words
A circuit according to claim 1, wherein said threshold voltage generating circuit comprises a feedback resistor connected between an output terminal and a comparison input terminal of said comparator circuit, first time constant setting means including capacitor means connected to said feedback resistor, switch means characterized by turning on or off in response to said comparator circuit output, and second time constant setting means connected to said capacitor means through said switch means.
Claim 4
Dependent Claim
54 words
A circuit according to claim 2, wherein said first time constant setting means includes a unidirectional circuit connected in series with said capacitor means, wherein said unidirectional circuit conducts current in one direction only, and wherein means is provided to reduce said threshold voltage substantially to zero when said switch means is turned on.
Claim 5
Dependent Claim
67 words
A circuit according to claim 3, further comprising an electromagnetic pickup coil for generating a periodic signal waveform, signal lines for connecting the ends of said pickup coil to the input terminals of said comparator circuit, means connected to said signal lines for clamping said periodic signal waveform substantially to one polarity, and means for compensating said threshold voltage for zero-crossing detection of said periodic signal waveform.
Claim 6
Dependent Claim
31 words
A circuit according to claim 1, wherein said time constant setting means includes a plurality of time constant setting means for successively changing said time constant to vary said threshold voltage.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-10-21 | 1989-04-22 | 1989-10-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-10-21 | 1993-04-22 | 1993-10-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-10-21 | 1997-04-22 | 1997-10-22 | $7700.00 | Window Closed / Lapsed |