ES2318983B2 - EVALUATION CIRCUIT FOR AN OPTICAL RECEIVER. - Google Patents

Abstract

Evaluation circuit for an optical receiver, which presents a voltage divider circuit, which is consisting of a measuring resistor (Rmess) and a first switching element (T1) and in which a voltage is applied power (Vdd). The first switching element (T1) is conductively connected to electricity through a receiver according to a radiation reception electromagnetic, and between the measurement resistance (Rmess) and the first switching element (T1) is taken a signal of evaluation (VIN). To avoid problems in the evaluation of measurement signals generated by the receiver (VE), in the case of excessive radiation from the receiver through strange light, is A circuit of additional current sources (ADF) is planned, which is connected in parallel to the measuring resistor (Rmess) and in the case of excessive radiation of the receiver causes a flow of additional current through the first switching element (T1), so that the first switching element (T1) works with a favorable signal / noise ratio also in the case of a excessive radiation from the receiver.

Description

Evaluation circuit for a receiver optical.

The invention relates to a circuit of evaluation for an optical receiver according to a circuit voltage divider, which is constituted by a resistance of measurement and a first switching element and in which it is applied a supply voltage, connected the first element of conductive switching of electricity according to a reception of electromagnetic radiation through a receiver and an evaluation signal being taken between the resistance of measurement and the first switching element, characterized by a circuit of additional current sources, which is connected in parallel to the measuring resistance and in the case of radiation excessive receiver, causes additional current flow to through the first switching element, so that the first switching element works, also in the case of a excessive radiation from the receiver, with a signal / noise ratio favorable. and especially to an evaluation circuit, as can be used, for example, in a push button switch sensitive to contact or in a remote control reception part or of communication.

Pushbutton switches sensitive to contact, especially infrared pushbutton switches, as used, for example, in command facilities of appliances, and remote control reception parts or communication usually contain an optical sensor, which it presents a receiver, which receives electromagnetic radiation, and a evaluation circuit for the evaluation of a measurement signal generated by the receiver of the optical sensor and for the generation of a corresponding evaluation signal for processing later. The basic structure of an evaluation circuit Conventional of this type is represented by way of example in the figure 3.

The evaluation circuit of Figure 3 it contains a voltage divider circuit, which is constituted by a measuring resistor R_ {mess} and by a transistor T1, and in which a supply voltage Vdd is applied. The signal of Measurement V E of the receiver connects the transistor T1 and the signal of evaluation V_ {IN} is taken between the measurement resistance R_ {mess} and transistor T1. In normal operation, the transistor T1 without activation, for example, of the switch button has high impedance, so that the signal of evaluation V_ {IN} has a high signal level. When activates the push button switch, transistor T1 is switched off impedance through the measuring signal V E of the receiver, of so that under the flow of current through the circuit of evaluation the signal level falls to a corresponding extent of evaluation V_ {IN}, which can be evaluated by a microprocessor connected as a switch activation button.

A generally known problem of such devices is the receiver's excessive radiation, for example to through strange light, which can cause a signal-to-noise ratio undesirable, so that through the evaluation circuit useful signals can no longer be evaluated. In the case of a radiation Excessive receiver becomes the low impedance transistor T1, such that the maximum current flow, determined through of Vdd and R_ {mess}, is reached through the circuit of evaluation, so that in the case of an activation of the push button switch is no longer possible since the flow of current and therefore a run of the devaluation signal V_ {IN}.

A possible proposal for the solution of problem is to reduce the measurement resistance R_ {mess} in the case of an incidence of strange light and in this way raise the possible current flow in the evaluation circuit. But with such a reduction in sensitivity to foreign light is it also reduces the useful signal at the same time, so that you can already adjust the signal / noise ratio in a way discretionally favorable.

Therefore, a task of the present invention is to reduce the sensitivity to strange light of a evaluation circuit for an optical receiver and at the same time maintain a useful signal or a sufficient signal / noise ratio high.

This task is solved through a evaluation circuit for an optical receiver with the characteristics of claim 1. The configurations advantageous and the developments of the invention are subject to the dependent claims.

The evaluation circuit for a receiver optical contains a voltage divider circuit, which is consisting of a measuring resistor and a first switching element and in which a voltage of power supply, the first switching element of conductive form of electricity in accordance with a reception of electromagnetic radiation through a receiver and being taken an evaluation signal between the measurement resistance and the first  switching element The evaluation circuit is characterized, in addition, by an additional current source circuit, which is connected in parallel to the measuring resistor and in the case of excessive radiation from the receiver, causes a current flow additional through the first switching element, so that the first switching element also works in the case of a excessive radiation from the receiver with a signal / noise ratio favorable.

In normal operation, that is, without excessive radiation from the receiver, the evaluation circuit works, in principle, as the conventional evaluation circuit represented in figure 3, since the circuit of sources of additional current does not essentially condition any current additional. However, in the case of excessive radiation from the receiver, although in a conventional evaluation circuit it is not no elevation of the current possible, for example with a keystroke, current source circuit additional feeds an additional current through the first switching element Since at the same time you can keep the measurement resistance at a high value of the resistance, the first switching element is switched through of the circuit of additional current sources to an area of operation with a sufficiently good signal / noise ratio, so that even in the case of excessive radiation from the receiver, a signal can be emitted from the evaluation circuit useful evaluable.

The first switching element is, by example, a photodiode or a phototransistor, and the resistance of measurement is in a more advantageous way a measurement resistor with a constant resistance value (high).

In a configuration of the invention, the circuit of additional current sources presents a circuit in series that is constituted by a first resistance and by a second resistor, which is connected in parallel to the measurement resistance; the resistance value of the first circuit resistance of additional current sources is (clearly) lower than the resistance value of the resistance measurement; and the second switching element is switched, in the case of excessive radiation from the receiver, to a conductive state Of electricity. The second switching element serves, by put it like this, as an additional current source for the first switching element

In an embodiment of the invention, the second switching element is a transistor, whose connection of door is, on at least one other resistance, in a way durable in the potential of the evaluation signal. In addition, the Additional current source circuit features a capacitor of current filtering, to maintain current flow additional through the first switching element, of a independent way of the oscillations of the signal potential of evaluation, in an essentially constant value. The circuit of additional current sources constituted in this way works relatively inert and is suitable, for example, for parts of Remote control or communication reception.

In an alternative embodiment of the invention, the second switching element is a transistor, whose door connection is activated through at least one other resistance and an accumulation capacitor at least in the times evaluation of the evaluation circuit for switching the Second switching element. In this case, for example, connect an accumulation capacitor connection with the voltage power while the other capacitor connection of accumulation is connected in each case before the times of evaluation of the evaluation circuit through a third element switching, preferably a transistor, which is activated at through a receiver control, with the signal potential of evaluation. The circuit of additional current sources constituted in this way it works relatively fast and is suitable, for example, for push-button switches sensitive to contact, in which the reception times, that is, the Evaluation times are known in advance.

A possible application of the invention is a push button switch sensitive to contact with an optical sensor, which it presents a receiver, which emits electromagnetic radiation, and a receiver that receives electromagnetic radiation, and with a circuit of evaluation according to the invention for the evaluation of a measurement signal, generated by the optical sensor receiver and for the generation of a corresponding evaluation signal.

Another possible application of the invention is a remote control or communication reception part, with a optical sensor, which has a receiver that receives radiation electromagnetic, and with an evaluation circuit according to the invention for the evaluation of a measurement signal generated by the receiver of the optical sensor and for the generation of a signal of corresponding evaluation.

The above as well as other tasks, characteristics and advantages of the invention will be better understood from the following description of preferred examples no Limitations with reference to the attached drawings. In these:

Figure 1 shows a block diagram schematic of an evaluation circuit for an optical receiver of according to a first embodiment of the present invention.

Figure 2 shows a block diagram schematic of an evaluation circuit for an optical receiver of according to a second embodiment of the present invention; Y

Figure 3 shows a block diagram schematic of a conventional evaluation circuit for a optical receiver

The following explains in detail the invention with the help of different embodiments with reference to figures 1 and 2.

The evaluation circuit represented in the Figure 1 is suitable in this case especially for use for remote control or communication reception parts. He evaluation circuit of figure 2, however, is suitable with preference for applications, in which reception times or of evaluation are known before, as for example in contact sensitive pushbutton switches, as used widely, for example, in appliance control parts electronic

The evaluation circuit of the first example of embodiment of figure 1 presents, as the evaluation circuit conventional described above with the help of figure 3, a voltage divider circuit, which is constituted by a measuring resistance R_ {mess} and by a first element of switching T1, for example a photodiode or a phototransistor and in which is applied a supply voltage V_ {DD}, by 5 V example. The evaluation signal V_ {IN} is taken between the measuring resistance R_ {mess} and the first element of T1 switching and is fed to a microprocessor (no represents) for further processing. The first element of T1 switching is conductively connected based on a measurement signal V E of the receiver (not shown), of so that, if necessary, a current flow is caused through of the evaluation circuit, which results in a signal corresponding evaluation V_ {IN}. Measuring resistance R_ {mess} and is in a more advantageous way a resistor with a constant high resistance value, to achieve a relationship favorable signal / noise

Additionally, this evaluation circuit presents a circuit of additional current sources A_ {add}, which is planned in parallel to the measurement resistance R_ {mess} and in the case of excessive radiation from the receiver must causing an additional current flow through the first switching element T1, to be operated in a work area with a favorable signal / noise ratio.

The additional current jumper circuit A_ {add} contains a series circuit, which is constituted by a first resistor R1, whose resistance value is clearly less than that of the measuring resistor R_ {mess}, and by a second switching element T2 in the form of a transistor. The gate connection of transistor T2 is connected through a second resistance R2 (relatively high) and a C1 capacity with the potential of the supply voltage V_ {DD} and connects through the second resistor R2 and a third R3 resistance (relatively high) with the signal potential of evaluation V_ {IN}. The values of resistors R2 and R3 are selected in this case so that in the case of a excessive radiation from the receiver, is applied in the door connection of the second switching element T2 a negative voltage such that the second switching element T2 is connected so conductive Then it can flow through the second element of T2 low impedance switching and second resistance relatively low R2 an additional current through the first switching element T1.

The operating mode of the circuit evaluation of figure 1 is as follows:

In the normal operation of the receiver, it is say without excessive radiation through strange light and without a signal reception, the first switching element T1 has a very high impedance. The level of the evaluation signal V_ {IN} is therefore very high (corresponds almost to the value of the supply voltage Vdd), which is evaluated through the microprocessor as no presence of a signal input. Since the evaluation signal V_ {IN} is essentially in the power supply voltage level Vdd, does not apply to the door connection of the second transistor T2 through the two resistors R2 and R3 essentially no negative voltage, of so that the second transistor T2 remains locked. He circuit of additional current sources A_ {add} does not feed in this case also no additional current, that is, that the evaluation circuit works like an evaluation circuit conventional.

If received now (always still without excessive radiation of foreign light) from the receiver a signal, then the first element of switching T1 through the measurement signal V_ {E} corresponding receiver at the moment of an impulse of the signal. Through the main circuit of the evaluation circuit a current flows, which causes a voltage drop across of the measurement resistance R_ {mess}, which has as consequence again a drop in the signal level of evaluation V_ {IN}. This race in the evaluation signal V_ {IN} is evaluated as input of the signal through the microprocessor. The height of the run in the evaluation signal V_ {IN}, in other words, the signal to noise ratio useful, is determined by the magnitude of the resistance of R_ {mess} measurement.

The circuit of additional current sources A_ {add} is conceived inert in such a way that neither during the short pulse of the signal, which is received by the receiver, feeds any additional current through the first element of  T1 switching. The evaluation circuit of the invention works, therefore, also here as an evaluation circuit conventional.

On the other hand, if excessive radiation occurs of the receiver through strange light, for example sunlight or artificial light sources, then the first element is switched switching T1 through the measurement signal V_ {E} corresponding receiver continuously conductive. Y this to the extent that the first switching element T1 has an impedance so low that the current through the first switching element T1 could theoretically be even greater, if this were allowed by the remaining evaluation circuit, especially the limitation through the measurement resistance R_ {mess}. The evaluation signal V_ {IN} is reduced from this way very strongly, clearly more than in the case of the Receiving a signal

Through the strongly reduced evaluation signal V_ {IN}, a strong negative voltage (against the potential of the supply voltage) is also applied to the gate connection of the second switching element T2, through which Switch the second transistor T2. By virtue of the second very low resistance R2 and the second very low impedance switching element T2, an additional current can flow through these two elements through the first switching element T1, which is clearly greater than that which is limited to through the measuring resistor R_ {mess}. The first switching element T1 is regulated in this way through the circuit of additional current sources A_ {add} again in an operating area with a signal-to-noise ratio.
favorable.

In the event that an impulse is now received from signal in this operating zone adapted from the first element T1 switching from the receiver, the first element is switched switching T1 through the measurement signal V_ {E} corresponding with an even lower impedance, so that the current flow can be further increased through the first switching element T1, which is possible under the circuit of additional current sources A_ {add} of the invention. Also in this case (signal impulse with a simultaneous excessive radiation of the receiver) can be recognized from this way a drop in the level in the evaluation signal V_ {IN}, which can be evaluated through the microprocessor.

Therefore, according to the circuit of A_ {add} additional current sources of the invention, it is guaranteed that the first switching element T1 is found always in an operating area with a signal / noise ratio good In addition, the resistance of R_ {mess} measurement, that is, it can still be maintained constant, so that also in the case of excessive radiation a clearly recognizable useful signal is generated as a signal of evaluation V_ {IN}.

The capacitor C1 in the circuit of sources of additional current A_ {add} is used for filtering oscillations (high frequency) in the signal level of V_ {IN} evaluation, which are not generated through the momentum of the signal, in order to make available in each case a flow of constant current through the first switching element T1. The capacitor C1 can therefore be designated as "current filtering capacitor".

As can be deduced from the previous explanations, the circuit of current sources additional A_ {add} only feeds an additional current to through the first switching element T1 when the receiver is found in the area of excessive radiation. In the state of normal operation of the receiver should not flow any current additional, so that the first switching element T1 is regulated in any case in a work area with a relationship signal / noise good enough.

With reference to figure 2, it is explained then a second embodiment of the present invention. In this case, the same elements and components are designated with the same reference signs as in the first embodiment example.

While the evaluation circuit of the first embodiment presents a circuit of sources of additional current rather inert A_ {add}, the circuit of evaluation of this exemplary embodiment of figure 2 is characterized by a rapid reaction time. As already mentioned, it is suitable, therefore, in a preferred manner for applications, in which the times of reception or evaluation times, such as in touch sensitive pushbutton switches, as used widely, for example, in appliance control parts electronic

The evaluation circuit of the second example of realization differs from the circuit of the first example of embodiment described above in the structure and in the mode of circuit operation of additional current sources   A_ {add}. As depicted in Figure 2, in this example of embodiment, especially the third resistor R3 is replaced in the circuit of additional current sources A_ {add} by means of a third switching element T3; he resistance value of the second resistor R2 is adapted in a corresponding way. The elements and components remaining are unchanged with respect to the first example of realization.

While the third switching element T3 in Figure 2 is configured as a switch, which can be formed, for example, by a Reed contact, in practice it is often advantageous to configure the third element of T3 switching as a transistor, which is activated through a controller control, which also activates, for example, the sensor optical contact sensitive push button switch.

The third switching element T3 closes in each case shortly before an expected signal pulse in the receiver, that is, for example, provided that the sensor emitter Optical emits electromagnetic radiation, that is, in each case little before an evaluation time of the evaluation circuit. With the T3 switch closed, applies to the door connection of the second switching element T2 the signal potential of evaluation V_ {IN}. In the normal operating state of the receiver (i.e., without excessive radiation), this potential corresponds approximately to the supply voltage Vdd, of so that the second switching element T2 remains blocked and the evaluation circuit works as in the case of previous embodiment example in a similar way to the circuit of conventional evaluation.

However, if the receiver produces radiation excessive, then applied on the second door connection switching element T2 through the radiator T3 closed a clearly negative signal (versus the voltage potential of power) and the accumulation capacitor C2 is charged. At instant of the evaluation, that is, when a reception is expected of a pulse of the signal through the receiver, it opens again the third switching element T3. The second element of T2 switching is conductively connected now through the accumulation capacitor C2, so that a flow can flow additional current through the first switching element T1, in a manner similar to the mentioned embodiment example previously, when an impulse signal is received. The circuit of additional current sources A_ {add} from the second example of realization forms a kind of circuit of "Sample & Hold. "

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Also the evaluation circuit of figure 2 it is guaranteed that the first switching element T1 (at least during the expected evaluation times) is always found in a work area with a favorable signal / noise ratio. Also here the measuring resistance R_ {mess} is one way more advantageous a resistance with a resistance value (high) constant, to be able to evaluate also in the case of radiation excessive receiver of the receiver a sufficiently large useful signal.

Claims (11)

1. Evaluation circuit for an optical receiver, with a voltage divider circuit, consisting of a measuring resistor (R_ {mess}) and a first switching element (T1) and in which a voltage of supply (Vdd), the first switching element (T1) has been connected in an electrically conductive manner in accordance with a reception of electromagnetic radiation through a receiver and an evaluation signal (V_ {IN}) is taken between the resistance of measurement (R_ {mess}) and the first switching element (T1), characterized by an additional current source circuit (A_ {add}), which is connected in parallel to the measuring resistor (R_ {mess}) and in the case of excessive radiation from the receiver, it causes an additional current flow through the first switching element (T1), so that the first switching element (T1) works, also in the case of excessive radiation from the receiver , with a favorable signal / noise ratio. 2. Evaluation circuit according to claim 1, characterized in that the first switching element (T1) is a photodiode or a phototransistor. 3. Evaluation circuit according to claim 1 or 2, characterized in that the measuring resistance (R_ {mess}) is a measuring resistance with a constant resistance value. 4. Evaluation circuit according to one of the preceding claims, characterized in that the circuit of additional current sources (A_ {add}) has a series circuit, consisting of a first resistor (R1) and a second element of switching (T2), which is connected in parallel to the measuring resistor (R_ {mess}); because the value of the resistance of the first resistance (R1) of the circuit of additional current sources (A_ {add}) is less than the value of the resistance of the measurement resistance (R_ {mess}); and because the second switching element (T2) is connected to a conductive state of electricity in the case of excessive radiation from the receiver. 5. Evaluation circuit according to claim 4, characterized in that the second switching element (T2) is a transistor, whose gate connection is in a lasting manner in the potential of the evaluation signal (V_ {IN}) through at least one other resistance (R2, R3). 6. Evaluation circuit according to claim 5, characterized in that the circuit of additional current sources (A_ {add}) has a current filtering capacitor (C1), to maintain a constant value the flow of additional current through the first switching element (T1), independently of the oscillations of the potential of the evaluation signal (V_ {IN}). 7. Evaluation circuit according to claim 4, characterized in that the second switching element (T2) is a transistor, whose gate connection is activated through at least one other resistor (R2) and which activates an accumulation capacitor ( C2) at least in the evaluation moments of the evaluation circuit for the switching of the second switching element (T2). 8. Evaluation circuit according to claim 7, characterized in that one connection of the accumulation capacitor (C2) is connected to the supply voltage (Vdd), while the other connection of the accumulation capacitor (C2) is connected to each case, before the evaluation times of the evaluation circuit, through a third switching element (T3) with the potential of the evaluation signal (V_ {IN}). 9. Evaluation circuit according to claim 8, characterized in that the third switching element (T3) is a transistor, which is activated through a receiver control. 10. Contact sensitive push button switch, with an optical sensor, which features a receiver that emits radiation electromagnetic and a receiver that receives radiation electromagnetic; and with an evaluation circuit according to a of claims 1 to 9 for the evaluation of a signal of measurement (V_ {) generated by the optical sensor receiver and for generating an evaluation signal (V_ {IN}) correspondent. 11. Part of receiving remote control or communication, with an optical sensor, that presents a receiver that receives electromagnetic radiation; and with an evaluation circuit according to one of claims 1 to 9 for evaluation of a measurement signal (V_ {) generated by the receiver of the optical sensor and for generating an evaluation signal (V_ {IN}) corresponding.