JPH0447674Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention is based on the invention that the detection signal output from a detector having DC characteristics such as a thermopile or thermistor bolometer and a preamplifier circuit connected thereto is higher than a reference signal. The present invention relates to a circuit that uses a comparator to discriminate whether it is large or small, and in particular is configured to automatically correct the temperature drift of the detector and preamplifier circuit by effectively utilizing the comparator used for the discrimination. The present invention relates to a completely new detected value discrimination circuit with a drift correction function.

[Conventional technology]

For example, when trying to detect the presence or absence of a person using a thermopile, conventionally the output from the thermopile is input to the signal input side of a comparator via a preamplifier, while the reference voltage power supply is connected to the reference input side of the comparator. By inputting a reference signal from the thermopile and preamp circuit, the comparator determines whether the detection signal from the thermopile and preamp circuit is larger or smaller than the reference signal, and whether the output of the comparator is at a high level or not. Depending on the low level, it is determined whether a person is within the field of view of the detector.

However, since a thermopile is extremely susceptible to temperature drift, the detection signal from the thermopile and preamplifier circuit becomes higher than the reference signal even when no one is present, causing the comparator to fail to discriminate. It often happens that the level of the output is reversed, leading to an erroneous determination that a person is present.

Conventional means to prevent malfunctions due to temperature drift include using a temperature-sensitive element (for example, a thermistor) in addition to the original detector, and dividing the output signal of the thermopile by the temperature signal of this thermistor. A temperature compensation circuit is used.

[The problem that the idea aims to solve]

However, if a special temperature compensation circuit is provided as in the conventional method described above, the detector itself will become more complicated, and the output of the thermopile and the sensor will be affected due to differences in heat capacity and installation position between the thermopile and the temperature sensing element. Since there is a time difference between the output of the thermal element and the output of the thermal element, the temperature drift cannot be sufficiently compensated for. In addition to the temperature drift of the thermopile, the preamplifier connected to the thermopile also has its own temperature characteristics, but the temperature compensation circuit cannot compensate for this temperature drift of the preamplifier as well. Furthermore, since the temperature characteristics of the temperature sensing element and the thermopile are generally different, the temperature compensation circuit itself cannot be constructed using a simple divider circuit and must have a very complicated circuit configuration. There are many problems such as.

The present invention was devised in view of the above-mentioned conventional circumstances, and its purpose is to reliably and accurately suppress the temperature drift of the detector and preamplifier without using a temperature-sensitive element, which has many problems as described above. An object of the present invention is to develop and provide a new and useful detected value discriminator circuit with a drift correction function that can perform compensation.

[Means to solve the problem]

In order to achieve the above object, the detected value discrimination circuit with a drift correction function according to the present invention includes a preamplifier on the output side of a detector having DC characteristics that appropriately amplifies the output of this detector and outputs a detected signal. At the same time, a comparator is provided on the output side of this preamplifier, and the detection signal is inputted to the signal input side of this comparator, while the reference input side of the comparator is connected to connected to the output side of the preamplifier via a delay device that delays and outputs the delayed detection output and an adder to which the delayed detection output is input as one input, and further higher than the rising voltage of the detection signal. The bias voltage is configured to be inputted as the other input of the adder via a switch means whose opening/closing is controlled based on the discrimination output from the comparator, and a person is not present within the detection field of the detector. When a person exists within the detection field of the detector, only the delayed detection output is input to the reference input side of the comparator. It is configured to be input to the reference input side of the comparator.

[Effect]

The effects exhibited by this characteristic configuration are as follows.

That is, according to the detected value discriminator circuit with a drift correction function according to the present invention, as will become clear from the description of the embodiments (particularly the detailed explanation of the operation) described later, the current value from the detector and preamplifier circuits By continuously comparing the detection signal at and the delayed detection signal past a certain period of time (that is,
Even if the detection signal from the detector and preamplifier circuit fluctuates due to temperature drift,
Since the delayed detection signal, which changes in accordance with the detection signal, is used as a reference signal in the comparator, the temperature drift of not only the detector but also the preamplifier connected to it can be constantly and accurately measured. It can be corrected over a very wide temperature range. Further, as mentioned above, since temperature drift can be corrected including the preamplifier, there is no need to use a highly accurate and expensive preamplifier, which is very economical. Furthermore, in the present invention, since the discrimination output from the comparator is specifically configured to be fed back to its reference input side, a reliable discrimination operation can be performed only when the original input is input to the detector. Therefore, since there is no malfunction like in the past, when determining the presence or absence of a person using a thermopile, for example, the determination can be made with very high accuracy.

〔Example〕

Hereinafter, specific embodiments of the present invention will be described based on the drawings.

FIG. 1 shows a first embodiment of a human presence/absence discriminating circuit constructed by applying a detected value discriminating circuit with a drift correction function according to the present invention.

In this figure, 1 is a thermopile as an example of a detector with DC characteristics, and 2 is the detector 1.
The detection signal output from the detector 1 and preamplifier 2 system circuit is directly input to the signal input side (-terminal) 3a of the comparator 3, and , are also input to the delay device 4. This delay device 4 outputs a delayed detection signal obtained by delaying the detection signal inputted from the detector 1 and preamplifier 2 system circuit by a certain period of time, and this delayed detection signal becomes one input of the adder 6. . Reference numeral 5 denotes an FET as an example of a switch means, the output of which becomes the other input of the adder 6. This switch means 5
is normally closed, and a bias voltage _Vs set to an appropriate magnitude is input to the other input side of the adder 6, but it is opened when the output of the comparator 3 turns to low level. be. The output of the adder 6 is input to the reference input side (+ terminal) 3b of the comparator 3.

Next, the operation of the detected value discrimination circuit with a drift correction function (person presence/absence discrimination circuit) configured as described above will be explained with reference to FIG. 2 as well.

In FIG. 2, A indicates the detection signal output from the detector 1 and the preamplifier 2 system circuit and is input to the signal input side 3a of the comparator 3, and B indicates the detection signal from the delay device. 4, and indicates a reference signal that is input to the reference input side 3b of the comparator 3. In this example, the detection signal A is input to the detector 1 and the preamplifier 2 system circuit. As shown in the figure, the temperature increases over time due to temperature drift.

First, when the switch means 5 is closed in a normal state where no one is present, the bias voltage V _s is input to the adder 6 and is added to the delay detection signal from the delay device 4. The reference signal B input to the reference input side 3b is higher than the detection signal A input to the signal input side 3a of the comparator 3. Moreover, this detection signal A is the negative terminal 3 of the comparator 3.
Since the reference signal (a) and the reference signal (b) are applied to the + terminal 3b, if this person does not exist within the detection field of view, the discrimination output (c) of the comparator 3 is at a high level H.

Next, when a person enters the detection field of view in the above-mentioned state, the detection signal A rises and the magnitude relationship with the reference signal B is reversed, and the discrimination output C of the comparator 3 changes to the low level L. Then, the switch means 5 opens and cuts off the bias voltage _Vs. Therefore, the reference signal ro decreases by the bias voltage V _s . If this bias voltage V _s is set slightly larger than the rising voltage of detection signal A, even if the delayed detection signal from delay device 4 rises after a certain period of time than detection signal A, the comparator 3 The discrimination output C maintains the low level L without changing its polarity.

Then, when there is no longer a person within the detection field of view and the detection signal A falls, the magnitude relationship with the reference signal B is reversed again, and the discrimination output C of the comparator 3 returns to the high level H.

In other words, even if the detection signal A fluctuates due to temperature drift of the detector 1 and preamplifier 2 system circuits, the reference signal B is also configured to fluctuate in accordance with the fluctuation of the detection signal A. During periods when malfunctions are likely to occur immediately after the rise and fall of the detection signal A, the discrimination output C of the comparator 3 is used to separate the detection signal A from the reference signal B. Therefore, despite fluctuations in the detection signal A due to temperature drift, a highly accurate discrimination output can be obtained from the comparator 3, and the presence or absence of a person can be accurately determined.

FIG. 3 shows a second embodiment in which the circuit configuration shown in FIG. 2 is simplified, and a so-called Schmitt trigger method is used in which the discrimination output from the comparator 3 is directly fed back to its reference input side 3b. I am using it. In this case, the difference voltage (H-L) between the high level H and the low level L in the discrimination output of the comparator 3
corresponds to the bias voltage _Vs in the above embodiment, so the differential voltage (HL) is set to an appropriate level. The operation of the device constructed in this manner is also substantially the same as that shown in FIG. 2, so its explanation will be omitted.

[Effect of idea]

As explained above, in this invention, DC
A preamplifier that appropriately amplifies the output of this detector and outputs a detection signal is connected to the output side of the detector having the characteristic, and a comparator is provided on the output side of this preamplifier, and the signal input side of this comparator is connected to the While the detection signal is inputted, the reference input side of the comparator is connected to a delay device that delays the detection signal for a certain period of time and outputs a delayed detection output, and the delayed detection output is inputted as one input. The adder is connected to the output side of the preamplifier via an adder, and the bias voltage larger than the rising voltage of the detection signal is connected to the adder via a switch means whose opening/closing is controlled based on the discrimination output from the comparator. When a person is not within the detection field of the detector, the sum of the delayed detection output and the bias voltage is input to the reference input side of the comparator. When a person is within the detection field of the detector, only the delayed detection output is input to the reference input side of the comparator, so that the output from the detector and preamplifier circuit is By continuously comparing the current detection signal and the delayed detection signal from a certain period of time past, in other words, even if the detection signal fluctuates due to temperature drift, the delayed detection signal, which changes in the same way, is used as the reference signal in the comparator. By using it as a sensor, the temperature drift of not only the detector but also the preamplifier connected to it can be corrected accurately at all times and over a very wide temperature range. Since temperature drift can be compensated for by including temperature drift, there is no need to use a highly accurate and expensive preamplifier. By configuring it to feed back to the detector, a reliable discrimination operation is performed only when the original input is input to the detector, and there is no malfunction like in the past. Various excellent effects are exhibited, such as being able to perform the determination with very high accuracy when determining the presence or absence of a person.

[Brief explanation of the drawing]

The drawings are for explaining specific embodiments of the present invention, and FIG. 1 is a circuit configuration diagram of a detection value discrimination circuit with a drift correction function (person presence/absence discrimination circuit) according to the first embodiment, and FIG. The figure shows a timing chart for explaining its operation, and FIG. 3 shows a circuit configuration diagram of a detected value discrimination circuit (presence/absence discrimination circuit) with a drift correction function according to the second embodiment. 1...Detector, 2...Preamplifier, 3...Comparator, 3a...Signal input side, 3b...Reference input side,
4...delay device, 5...switch means, 6...adder, _Vs ...bias voltage.

Claims (1)

[Scope of utility model registration request] A preamplifier that appropriately amplifies the output of this detector and outputs a detection signal is connected to the output side of the detector with DC characteristics, and a comparator is provided on the output side of this preamplifier, and the signal input side of this comparator is connected to While the detection signal is inputted, the reference input side of the comparator is connected to a delay device that delays the detection signal by a certain period of time and outputs a delayed detection output, and the delayed detection output is inputted as one input. A bias voltage greater than the rising voltage of the detection signal is connected to the output side of the preamplifier via an adder, and furthermore, a bias voltage greater than the rising voltage of the detection signal is connected to the output side of the preamplifier via a switch means whose opening/closing is controlled based on the discrimination output from the comparator. When a person is not within the detection field of the detector, the sum of the delayed detection output and the bias voltage is input to the reference input side of the comparator. and when a person exists within the detection field of the detector, only the delayed detection output is input to the reference input side of the comparator. Value discrimination circuit.