HUT64652A - Circuit arrangement for controlling signals - Google Patents

Abstract

In evaluating signals from optical sensors in particular, it is often necessary to reliably recognize different levels of useful signals. For example, marks of various thicknesses are arranged on the headwheel motor rotor, so that the narrow marks provide detection signals having a reduced maximum value and the wide marks provide signals having a high maximum value. The first signals are used to switch the head-barrel motor and the latter to switch the magnetic heads of a VCR. Given the tolerances of the marks and components of the evaluation circuit, the distinction between the different amplitudes of the signals is not always ensured. In order to overcome this disadvantage, a signal regulator circuit maintains the average value of the maximum values of selected signal portions at a constant level. This circuit is useful in video recorders, in compact disc players, for generally controlling signal parts.

Description

'When evaluating / evaluating optical sensors, we often need to safely recognize different useful signal levels. For example, the rotor of a jet engine has markings of different widths, the sensor marks of the narrow markings give a low peak value, the wide markings give a high peak value. The first signals are used to commute the headstock and the latter signals are used to switch the magnetic heads of the video recorder. Due to the tolerances of the markings and the evaluation circuit, the distinction between signal amplitudes is not always guaranteed. The present invention relates to a control circuit which maintains a constant average of the peak values of the selected signal components. The present invention relates to video recorders, CD players (generally, for controlling signal components).

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Representative:

Gödölle, Kékes, Mészáros & Szabó

Patent Attorneys Working Community

Budapest

Circuit arrangement for signal control

Applicant: Deutsche Thomson-Brandt GmbH, Villingen-Schwenningen Γ Inventors: GLEIM, Günter, Viliingen, pt

ROTHERMEL, Albrecht, Viliingen gOTHS'KNE'L _; (fa *, Ot

Date of filing: 21.05.1991

Priority: 28.05.1990 (P 40 17 124.8JE) / yiitivvi <' ¹ F'> 1 / OL'3 tt

The present invention relates to a circuit arrangement for controlling signals of different amplitudes to maintain a predetermined signal level. Signals of various levels are produced, for example, by photocells. By drawing a line pattern on the circumference of a motor rotor, a light-sensitive element produces pulses which are used, for example, to commutate and phase regulate the motor. Within the line pattern, narrow strips of constant width, evenly perpendicular to the scanning direction, may be assigned to a wide strip, which may then serve, for example, as a reversing signal for switching the recording and playheads of a magnetic recording device. . The line pattern has tolerances on the lines. The efficiency of the photocell also has tolerances, so the peak values of the signals they emit are not constant. It is known to adjust the reference level R of the photocell signal to a constant value. thus, the height of the signal pulses generated will be independent of the coupling factor of the photocell. However, with such a measure, there may be differences in the beam path of the light barrier, such as the beam alignment, and differences in line width between different line patterns still lead to different signal amplitudes, making it difficult to discriminate between the two levels.

It is an object of the present invention to provide a structure of signal control that is independent of the characteristics and tolerances of the transmitter. The present invention addresses this object by the features set forth in the patent claim. Other embodiments of the invention are set forth in the dependent claims.

The invention has the advantage that, for example, a light barrier consisting of a light source, an optical aperture and a light receiver can be constructed with greater tolerances and thus more economically, which also makes the construction of a motor rotor onto which such a line pattern is applied more economical.

The invention will now be described, by way of illustration, in an exemplary embodiment, wherein:

Figure 1 illustrates the principle of the invention; the

Figure 2 illustrates a detailed exemplary embodiment of the invention; the

Figure 3 is a diagram illustrating the operation of the invention.

Fig. 1 shows a known transducer 1 consisting of a light source 2 and a light receiver 3, between which there is a movable aperture 4 with optical markings. For example, the markings on the optical blind 4 are mechanically rigidly connected to the head drum of a head drum motor. They consist, for example, of dark stripes 5 and 5 'which are evenly spaced along the periphery and serve to synchronize and phase regulate the motor. The strips 5 'are distinguished from the strips 5 by their greater width. They are used, for example, to produce a reverse signal. Depending on the width of the stripes that pass through the photocell, the output of the encoder 1 produces a pulse signal S of different peak value. The 5 'wide stripes give the peak A2 and the narrow strips 5 give the peak A1. The peak pulses Al have a precise and constant pulse-pause ratio t1: t2 at any number of revolutions of the motor and thus of the aperture 4. The generated sensor signal is applied to one of the (+) inputs of a comparator 6 which has a reference voltage Uref at the other (-) input corresponding to the average of the positive peaks of the desired peak pulses A1. thus, for a sufficiently long period of time, nearly half of the peak Al pulses are

higher than the reference voltage, but the other half smaller. When the predetermined reference voltage Uref is exceeded, the output of the comparator 6 switches to the upper level and switches on a power source of value II which charges a capacitor 7. This change is amplified by a regulator voltage amplifier 8, which produces a voltage drop at its output. In this way the light source 2 is controlled brighter. Otherwise, that is, under reference voltage or between the strip marks, the output of comparator 6 is low, so that power source 12 is charged, which charges the capacitor in the opposite direction. The signal change at the output of the comparator 6 results in a voltage increase at the output of the regulator voltage amplifier 8 and adjusts the light source darker. The currents II and 12 are adjusted to approximately correspond to the half-pulse-pause ratio of the sensor signal, i.e., a large current II during the duration of the pulses t1 and a relatively small current 12 during the duration t2 of the pauses. The ratio of currents II and 12 in the practically tested circuit of FIG. 2 is about 50: 1.

Figure 2 illustrates a detailed embodiment of the claimed arrangement, which is described below.

This arrangement is particularly suitable for integrated switching technology. Connect the + Vcc supply voltage to the Pl connection of the arrangement. The P2 connection is connected to the ground potential of the supply voltage. The light-sensitive element 3, for example a phototransistor, is connected to the P3 connection and is connected to a Vcc supply voltage via a resistor 11. The P4 connection is connected to a Vcc power supply via a 10-series resistor and a light emitting element 2, such as a light-emitting diode. A capacitor 7 is connected to terminal P4, the other end of which is connected to terminal 5. The P6 connector can be used to remove the master switch signal and the P7 connector to remove the commutation pulses. By using the reference current Iref and TI, the currents (11 + 12) and (12) are generated by the current mirrors T2, T3 and T4, T5. The ratio of 12 to Il is about 1:50. The generated sensor signal S is compared by three comparators K1, K2, K3 with three threshold values S1, S2 and S3 given by resistors W1, W2, W3 and W4. As soon as the first S1 threshold set by the comparator OFF is reached, it generates a pulse at the output of P7. As long as the pulse peaks of the sensor signal S are below the threshold value S2, which corresponds to the value specified for control, the output of the comparator K2 is at ground potential, so the current 11 + 12 is led to ground via transistor T6. The transistor T8 connected as a diode is closed and a current 12 flows, which charges the capacitor 7 until the sensor signal S reaches the threshold S2. At this moment, the output of the comparator K2 goes to the upper state, thereby closing the transistor T6. In this case, the current 11 + 12 is no longer conducted with transistor T6, but at the node behind transistor 8, the capacitor 7

• · is divided into 12 currents flowing through the transistor 5. The base current of the T9 transistor can be neglected. The charging time constant of the capacitor 7 is chosen so large that in steady-state operation the charge of the capacitor changes only slightly with each pulse. Thus, the retracted control state occurs exactly when the average of the peak pulses has reached the switching threshold of the comparator K2. The voltage at the P5 connection of capacitor 7 is amplified by a control amplifier consisting of transistors T9, T10 and Tll. The amplified control signal is applied to the light emitter 2 so that it is brighter at lower peaks and vice versa. Here, the capacitor 7 acts as an integrator with the amplifier. When the third threshold S3 is reached, the output of comparator K3 goes to the upper state and the transistor T7 is opened, and then the current II is brought back to ground potential. In this case, the current 12 serves to charge the capacitor 7. The voltage at the P5 connection decreases and the voltage at the P4 connection increases, thereby reducing the current flowing through the light emitting element 2.

Figure 3 shows the effect of the measures of the invention. 3a. and 3b. Figures 1 to 5 show the output pulses of two different conventionally controlled sensors. It will be appreciated that the average of the positive peak values of the pulses M1 is in Fig. 3a. 3b, and greater than that of FIG. 3b. The average peak positive M2 of the sensor of FIG.

3c. and 3d. Figures 1 to 5 show pulse diagrams for two different sensors when using the method of the present invention. Here, the mean values of the positive peak pulses M3 and M4 are the same as the lower peak values, while the peak-to-peak values of the pulses are of different magnitudes.

The invention is not limited to the use described above, as an example of a signal produced by a line pattern on the circumference of a motor rotor.

The control circuit of FIG. 2 also operates and behaves in the same way for other similar signals to input P3. For example, the signals may come from a light barrier in a heating strip, in which case they are not necessarily steep-edged pulses.

Claims (5)

Patent claims A switching arrangement for controlling pulse-shaped signals of approximately periodic repetition, comprising a first group of amplitudes having an oscillation about a first mean value and a second group of oscillations about a second mean value, characterized in that the amplitudes are controlled such that their first group pulse the number of waveforms exceeding one of the required peaks (S2) and the number of pulse waveforms in the first group that do not reach the required peak (S2) are approximately equal over a sufficiently long period, and thus the first group the mean of its peak values is kept constant and signals from the second group above a predetermined threshold (S3) have no or only a minor influence on the control. A circuit arrangement according to claim 1, characterized in that a first comparator circuit (K2) is provided, the first input of which is provided with a reference voltage corresponding to the average of the amplitudes of the signals of the first group and the second input of the pulse shape signal to be controlled. the output signal of the first comparator circuit (K2) activates a first DC current generator (12) during the pulse breaks to charge the regulator voltage integrator (7, 8) or activates a second current generator (II) for the pulses discharging the regulator voltage integrator (7, 8). The circuit arrangement according to claim 1 or 2, characterized in that a second comparator circuit (K3) is selected which selects above-average signal components of the first group of signals and disables them for control. A circuit arrangement according to claim 2, characterized in that the two current generators (II, 12) are set such that the current of the current generator (12) for charging the integrator is equal to the current of the current generator for discharging the integrator. fixed relationship. The circuit arrangement according to claim 4, characterized in that the current ratio of the two current generators (II, 12) corresponds to the half pulse pause ratio of the first group of signals. The authorized person; ZDQU.u, bluish .. MFSZA OSftS