Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Particular stable state circuit
Patent
1997-05-07
1999-03-09
Lam, Tuan T.
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Particular stable state circuit
327206, H03K 508
Patent
active
058806148
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a circuit arrangement for evaluating the output signal of an active sensor which is configured as a binary current signal, i.e., a square-wave signal with two different current levels.
German patent application No. 39 36 831 discloses a circuit arrangement for conditioning the output signal of a rotational speed sensor. The circuit arrangement includes a trigger circuit or flipflop having change-over thresholds which are varied in response to a coupling factor that influences the output voltage of the sensor. A circuit arrangement of this type is appropriate for use in passive and active sensors. When evaluating the output signal of an active sensor which issues a binary current signal, however, a current/voltage conversion by way of a serially connected load impedance of a relatively low ohmic value would be necessary to provide a sufficient operating voltage for the active sensor. This impedance would require a great load capacity to withstand a short-circuit of the sensor line with respect to the supply voltage. In addition, a high degree of accuracy of the impedance would be necessary because the signal identification of the sensor depends on this accuracy. Impedances of this type are complicated, and the high energy consumption is a shortcoming. Identification of sensor errors would be possible only by additional circuit structure. Overlapping of the range of function and range of error identification is not possible with such a circuit arrangement when used in an active sensor.
OBJECT OF THE INVENTION
It is an object of the present invention to provide a circuit arrangement which ensures a reliable identification of the output signal of an active sensor issuing a binary current signal even with unfavorable voltage tolerances and tolerances of structural elements. Further, leakage currents or shunts (as long as they do not exceed a predetermined extent) which are inevitable in practical operations, should not impair the evaluation of the sensor signal. However, short-circuits of the sensor lines to ground or relative to the current supply, short-circuits among the sensor lines and interruptions of the sensor lines should be perceptible nevertheless. In addition, the circuit arrangement should be especially appropriate for application as an integrated circuit.
SUMMARY OF THE INVENTION
It has been found that this object may be achieved by the circuit arrangement described in patent claim 1. The special features of the circuit arrangement of the present invention include that signal currents proportional to the sensor current are produced from the sensor current by way of a current mirror circuit, the current induced by a current mirroring operation is drawn from a (stabilized) voltage source by way of an ohmic resistance, whereby a binary voltage signal corresponding to the sensor output signal is generated, the voltage signal is sent to a flipflop which has a variable change-over threshold and compares the voltage signal with a reference value composed of a reference voltage and a hysteresis voltage, and the change-over threshold of the flipflop is responsive to the reference value.
A current mirroring operation of the type according to the present invention may easily be achieved by an integrated circuit. The relatively high sensor current is converted by way of the current mirror into a lower current which can be evaluated with low energy consumption. The lower current is drawn from a stabilized voltage source by way of an ohmic resistance in order to generate a voltage signal which can be evaluated by way of a flipflop and is indicative of the course of the sensor signal.
In a preferred aspect of the present invention, the reference voltage is varied as a function of the actual sensor current, which is influenced by leakage currents, shunts, the magnitude of the supply voltage, etc., or as a function of the transformed current that is derived by a current mirroring operation. The change-over threshold of the flipflop is thereby adap
REFERENCES:
patent: 4532437 (1985-07-01), Bodig et al.
patent: 4947091 (1990-08-01), Fukuoka
patent: 5014675 (1991-05-01), Koiwa
patent: 5218298 (1993-06-01), Vig
Japanese Publication 56-145757 vol. 7 No. 132 (Jun. 9, 1983).
Japanese Publication 61-165572 vol. 12 No. 232 (Jun. 30, 1988).
Search Report of the German Patent Office for Application P4434180.6.
English Translation of the International Preliminary Examination Report of International Appl. No. PCT/EP95/03655.
Fey Wolfgang
Zinke Olaf
Zydek Michael
ITT Manufacturing Enterprises Inc.
Lam Tuan T.
Lewis J. Gordon
Twomey Thomas N.
LandOfFree
Circuit arrangement for evaluating the output signal of an activ does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Circuit arrangement for evaluating the output signal of an activ, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Circuit arrangement for evaluating the output signal of an activ will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1325103