Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
  • H03K5/01—Shaping pulses
  • H03K5/08—Shaping pulses by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding
  • H03K5/082—Shaping pulses by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding with an adaptive threshold
  • H03K5/084—Shaping pulses by limiting; by thresholding; by slicing, i.e. combined limiting and thresholding with an adaptive threshold modified by switching, e.g. by a periodic signal or by a signal in synchronism with the transitions of the output signal

Definitions

• Circuit arrangement for processing an inductive transmitter signal
• the invention relates to a circuit arrangement for processing an inductive transmitter signal which is fed via an input resistor to an input of a comparator connected to an amplitude-dependent tracking device for a trigger threshold, the other input of which is connected to a reference potential.
• the inductive transmitter signal is evaluated via a bridge circuit.
• the inductive transmitter signal is raised to half the supply voltage via one part of the bridge and fed to one input of a comparator, while the other input of the comparator is also connected to half the supply voltage via the other part of the bridge.
• the resistors in the inductive sensor branch are usually discrete, while the resistors in the reference branch are preferably integrated.
• the time constant of the tracking device is namely adapted to the motor dynamics, so that the trigger threshold is not sufficiently tracked. Further timing errors can arise from asymmetries and tolerances of components of the tracking device or from the not always exact course of the interrupt-triggering edge of the inductive transmitter signal.
• Another circuit arrangement for processing an inductive transmitter signal is specified in DE 32 26 073 C2.
• two different circuit parts are provided, one circuit part being used only in the event that the inductive transmitter signal is relatively small, while the other circuit part is used for larger inductive transmitter signals and to track the switch-on trigger threshold.
• This circuit arrangement requires a corresponding effort.
• the invention has for its object to provide a circuit arrangement of the type described in the introduction, in which inductive transmitter signals with relatively small amplitudes can also be reliably evaluated with less effort and time errors are largely avoided.
• Voltage dividers are avoided by reference to ground, and a constant potential is maintained throughout, so that the basic hysteresis of the comparator remains tied to ground and does not go away, as is the case with the circuit arrangement assumed as the starting point due to the different tolerances and additional temperature drifts is. In this way, smaller amplitudes can also be evaluated and / or comparators with larger basic hysteresis can be selected, so that the signal-to-noise ratio can be increased. Because of the fixed basic trigger threshold in the zero crossing of the inductive sensor signal, the time error, for example with regard to the inductive sensor signal tapped by a sensor wheel, is also minimal, even when the sensor wheel is not running smoothly and the associated amplitude modulations.
• a larger signal-to-noise ratio is also achieved in that the tracking of the downshift trigger threshold can run freely, whereas with previous ones Circuit arrangements frequently bracketing the maximum tracking to a relatively low value in order to limit the time error. Further advantages of the present circuit arrangement are a small chip area requirement for integration and a low wiring effort.
• a simple construction of the circuit arrangement with reliable function is such that the tracking device has a peak value rectifier circuit with which the peak voltage value of a half-wave can be stored, so that the tracking device is further designed such that from the stored
• Voltage peak value is derived via a converter resistor with a weighted evaluation current, which is supplied as a reference variable to a current source that can be switched on at the input of the comparator, and that the current source is switched on by a switch when the zero crossing is detected in one direction at the input of the comparator and when the passage is recognized by the downshift trigger threshold shifted with the guide variable in the sense of the inductive transmitter signal amplitude, the switch is separated from the input by means of the switch.
• the switch can be actuated in a simple manner in that an actuation input of the switch is connected to the output of the comparator.
• the peak value rectifier circuit has a circuit resistor connected between the inductive transmitter and the input resistor, a rectifier diode connected in series therewith and a capacitor connected to its cathode and connected to ground, and that the converter resistor is between the rectifier diode and the capacitor is connected.
• a clamp circuit with two diodes is provided, the first diode being connected with its cathode to the supply voltage and with its anode at the input of the comparator and the second diode with its anode to ground and with its cathode to the input of the comparator sen, so excessively large signal amplitudes of the inductive transmitter, which can be many times larger than the supply voltage, are limited to a manageable value.
• a further advantageous embodiment is such that the current source is connected to the voltage supply with its connection remote from the input of the comparator.
• a preferred use of the circuit arrangement is that the speed and / or the angular position of the crankshaft of an internal combustion engine are detected. Current disturbances can be suppressed by adapting the time constant of the peak value rectifier circuit to the motor dynamics.
• Fig. 1 is a schematic representation of the basic principle of
• Circuit arrangement Fig. 2 shows the circuit arrangement of Figure 1 with a
• Fig. 4 shows an inductive transmitter signal with trigger times and an associated output signal.
• An IG inductive sensor has one connection + to ground, while its other connection - has one
• Input resistor RE is connected to the non-inverting input + of a comparator KO with a certain basic hysteresis.
• the inverting input - of the comparator KO is connected to ground as the reference potential U R.
• the trigger points are thus zero V + hysteresis / 2 or zero V - hysteresis / 2.
• FIG. 2 shows a circuit arrangement in which an amplitude-dependent tracking device for a trigger threshold is additionally provided compared to the circuit arrangement according to FIG. 1.
• a series circuit comprising a circuit resistor RS, one connected to it with its anode
• a converter resistor Rx is connected between the cathode of the rectifier diode D3 and the capacitor C, the other connection of which is led via a switching element for multiplication by a factor k to a current source SQ.
• the current source SQ is connected on the one hand to a supply voltage VCC and on the other hand via a switch SCH at the input + of the comparator KO.
• the actuating input of the switch SCH is connected to the output of the comparator KO.
• a peak value rectifier circuit is formed by the switching resistor RS, the rectifier diode D3 and the capacitor C, which stores the peak value of the positive half-wave of the inductive transmitter signal u G.
• the circuit resistance RS limits the current for charging C. The greater the circuit resistance RS, the less the positive amplitude of the current signal is loaded.
• the stored voltage is converted into an evaluation current i B via the converter resistor Rx.
• This amplitude-dependent evaluation current i B serves as a reference variable for the current source SQ, which is located at the input + of the comparator KO.
• the current source SQ is switched on after detection of the zero crossing from positive to negative signal amplitude of the inductive transmitter signal.
• the voltage at input + of comparator KO is raised by the value i B xkx RE via input resistor RE, so that the switch-back point is also shifted to the same extent.
• FIG. 4 shows the switching points of the processes described at the zero crossing of the signal amplitude, that is to say at the basic trigger threshold GSCHW, and at the switchback point, that is to say at the tracked switchback trigger threshold NSCHW, together with the resulting output signal u A of the comparator KO shown.
• FIG. 2 also provides a clamp circuit with two diodes D1 and D2, the first diode D1 having its cathode connected to the supply voltage and its anode connected to the input + of the comparator KO, while the second diode is connected to it Anode to ground and with their
• Cathode is at the input + of the comparator KO. This will Inductive encoder signal that can assume values many times higher than the supply voltage VCC, for example limited to the value of the supply voltage VCC.
• the reference to ground potential always results in a time-accurate triggering at the zero crossing of the inductive transmitter signal, so that the output signal u A is switched on the corresponding edge practically without a time error.
• the larger signal amplitudes are used to improve the Störabsta ⁇ d.
• the zero crossing from negative to positive signal amplitude of the inductive sensor signal u G could also be used for the basic triggering and the falling signal edge for the downshift triggering.
• FIGS. 3A and 3B make clear that a tracked trigger threshold, for example to half the value of the amplitude (FIG. 3A), brings about a substantial suppression of the time error t compared to a fixed trigger threshold FSCHW. Nevertheless, a certain time error can occur with such a tracking of the trigger threshold as a result of non-ideal signal edges or because of the tolerances of the tracking device.
• Another reason for the timing error is that, for example, when tracking the speed and / or position of the crankshaft of an internal combustion engine, the tracking device is adapted to the engine dynamics and does not immediately follow the changes in amplitude of the inductive transmitter signal. With the described triggering in the zero crossing, the time errors are minimized.

Landscapes

• Physics & Mathematics (AREA)
• Nonlinear Science (AREA)
• Transmission And Conversion Of Sensor Element Output (AREA)
• Manipulation Of Pulses (AREA)

Priority Applications (2)

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Publications (1)

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ID=7763772

Family Applications (1)

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Citations (4)

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• 1995
  • 1995-06-07 DE DE1995120690 patent/DE19520690A1/de not_active Ceased
• 1996
  • 1996-06-05 WO PCT/DE1996/000984 patent/WO1996041414A1/de not_active Application Discontinuation
  • 1996-06-05 JP JP9500078A patent/JPH10504160A/ja active Pending
  • 1996-06-05 KR KR1019970700623A patent/KR100377036B1/ko not_active IP Right Cessation
  • 1996-06-05 EP EP96919629A patent/EP0774177A1/de not_active Withdrawn

Patent Citations (4)

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