JP2002071832A - Infrared detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a human body by positively eliminating influences from popcorn noise without resulting in increase of the number of parts or enlargement of a circuit. SOLUTION: A control circuit 7 turns off switching circuits 3, 5, and 8 during a standby mode, turns on the switching circuit 3 to lower a conversion impedance of an I/V converting circuit 2 for just a predetermined time from a point of time a predetermined determination signal is inputted from a level determining part 6, turns on the switching circuit 5 to lower a gain of a voltage amplifying part 4 just the predetermined time from the point of time the predetermined determination signal is inputted from the level determining part 6, and turns on the switching circuit 8 just a predetermined time from a point of time where both switching circuits are turned off to directly connect the level determining part 6 with a driving circuit 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared detector for detecting infrared radiation energy, and more particularly to an infrared detector for detecting infrared radiation energy emitted from a human body or the like.

[0002]

2. Description of the Related Art In recent years, for the purpose of energy saving and the like, various electric appliances which detect movement of a human body and operate efficiently have been proposed. Such an electric device generally has a built-in infrared detecting device for detecting a human body. This infrared detection device includes, for example, a pyroelectric element that detects a change in infrared radiation energy in a predetermined detection area, and outputs a human body detection signal indicating that a human body has been detected when the change amount is equal to or more than a predetermined level. It is supposed to. Then, the electric device performs an operation such as ON / OFF of a power switch according to a human body detection signal output from the infrared detection device.

[0003]

An electric device incorporating the above-mentioned infrared detection device malfunctions if the infrared detection device erroneously outputs a human body detection signal due to factors other than the human body. In order to avoid such a situation, it is necessary for the infrared detection device to accurately detect a human body while minimizing the influence of noise and the like.

[0004] One of the causes of erroneous detection of a human body in an infrared detection device is noise called popcorn noise. This popcorn noise concentrates mechanical stress on the pitching part and microcrack part caused by the difference in the coefficient of thermal expansion of the pyroelectric substrate that constitutes the pyroelectric element and the circuit board that mounts the electronic components, and unnecessary charges are generated. This is caused by the charge output from the pyroelectric element as a current.

Therefore, there has been a demand for an infrared detector which eliminates the influence of popcorn noise and avoids erroneous detection. As an example of such an infrared detector, a configuration as shown in a block diagram of FIG. Can be considered.

[0006] This infrared detecting device includes a pyroelectric element 101.
, A current-voltage (I / V) conversion circuit 102, a first voltage amplification unit 103, a second voltage amplification unit 104, and a human body detection unit 1.
05, a popcorn noise detection unit 106, a control circuit 107, and switch circuits 108 and 109.

The pyroelectric element 101 includes a lens system and collects infrared radiation energy in an infrared detection area. The pyroelectric element 101 outputs a current corresponding to a change in the amount of collected infrared light to I
/ V conversion circuit 102. I / V conversion circuit 102
Converts the input current into a voltage and outputs the voltage to the first and second voltage amplifiers 103 and 104. The first and second voltage amplifiers 103 and 104 amplify the input voltage.

The first voltage amplifying section 103 is given the characteristics of a band-pass filter centered at about 1 Hz, and the second voltage amplifying section 104 selects a higher frequency than the first voltage amplifying section 103. For this purpose, a characteristic of a high-bandpass filter that passes components of several tens of Hz or more is provided.

This is because the output signal from the pyroelectric element 101 has a frequency component centered at about 1 Hz due to the movement of the human body, and the output signal due to popcorn noise (see FIG. 3A described later). This is because it shows a waveform that rises much faster than that caused by the movement and then immediately decays.

Thus, the voltage amplified by the first voltage amplifier 103 is used for detecting a human body, and the voltage amplified by the second voltage amplifier 104 is used for detecting popcorn noise. As described above, by amplifying the output of the I / V conversion circuit 102 by the voltage amplifying units 103 and 104 having different filter characteristics, the infrared detecting device can change the amount of infrared light due to the movement of the human body and generate popcorn noise. Can be distinguished from others.

[0011] The popcorn noise detection unit 106 has a second
When the amplitude of the voltage signal output from voltage amplification section 104 is equal to or greater than a predetermined amplitude, a predetermined popcorn noise detection signal is output to control circuit 107. When the popcorn noise detection signal is input, the control circuit 107 operates the switch circuits 108 and 109 to respectively adjust the conversion impedance of the I / V conversion circuit 102 and the gain of the first voltage amplification unit 103 for a predetermined time. Lower (reset state). As a result, the human body detection unit 105
Determines that the amplitude of the output of the first voltage amplification unit 103 does not reach the predetermined level, and does not output the human body detection signal. This can prevent erroneous detection due to popcorn noise.

As described above, the first and second voltage amplifiers 1
By giving different filter characteristics to 03 and 104, it is possible to realize an infrared detecting device that can distinguish between popcorn noise and movement of a human body.

However, in the configuration shown in FIG. 7, the order of the filter and the like increase in order to obtain the filter characteristics required on the semiconductor integrated circuit. The increase in the area of the resistor occupying the circuit causes an increase in the size of the circuit. On the other hand, in recent years, miniaturization of electrical equipment has been rapidly progressing, and accordingly, there has been a strong demand for miniaturization of infrared detectors. Therefore, reduction in the number of external components and miniaturization of circuits have become indispensable.

The present invention has been made in view of the above,
An object of the present invention is to provide an infrared detection device capable of accurately detecting a human body by reliably removing the influence of popcorn noise without increasing the number of parts or increasing the size of a circuit.

[0015]

According to the present invention, there is provided first conversion means for detecting a change in infrared radiation energy in a predetermined detection area, converting the change into a current, and outputting the current, and outputting the first conversion means. A second converting means for converting the supplied current into a voltage and outputting the voltage, a voltage amplifying means for amplifying and outputting a signal in a predetermined low frequency range among the voltage signals output by the second converting means, Level determining means for outputting a predetermined determination signal when the voltage signal output by the voltage amplifying means is equal to or higher than a predetermined level; resetting means for resetting the conversion operation of the second conversion means; Reset control means for resetting the conversion operation of the second conversion means for a predetermined reset time by the reset means; and a reset release time by the reset control means. When the determination signal is output to the Luo predetermined human body detection time is obtained and a detection control means for outputting a predetermined human body detection signal (claim 1).

According to this configuration, a change in the infrared radiation energy in the predetermined detection area is detected, the change is converted into a current and output, and the current is converted into a voltage and output, and the converted voltage is output. Among the signals, a predetermined low frequency band signal is amplified and output, and when the amplified voltage signal is equal to or higher than a predetermined level, a predetermined determination signal is output.

When the determination signal is output, the resetting means resets the conversion operation of the second conversion means for a predetermined reset time. The determination signal is reset within a predetermined human body detection time from the time when the reset is released. When output, a predetermined human body detection signal is output.

As a result, when the amplified voltage signal is caused by popcorn noise, the voltage signal rises rapidly and then attenuates immediately thereafter. No output is made and no human body detection signal is output. On the other hand, when the amplified voltage signal is due to the human body, the voltage signal changes slowly, so that the determination signal is output within the human body detection time from the time when the reset is released, and the human body detection signal is output. The Rukoto.

Therefore, with a simple configuration only by setting a predetermined human body detection time from the reset release point, it is possible to reliably prevent a signal due to popcorn noise from being erroneously detected as a human body.

In this specification, "resetting the conversion operation of the second conversion means" means to hold the voltage level output from the second conversion means at zero or a constant value irrespective of the input current level. Shall be included.

Further, in the infrared detecting apparatus according to the first aspect, the second reset means for resetting the voltage amplifying means, and the voltage amplifying means is controlled by the second reset means when the determination signal is output. Second reset control means for resetting for a second reset time, wherein the reset release time by the reset control means and the reset release time by the second reset control means are set to different times from each other; Outputs the human body detection signal when the determination signal is output within the human body detection time from the time point when both resets are released by the reset control means and the second reset control means (claim 2).

According to this configuration, the time at which the reset of the conversion operation of the second conversion means is released and the time at which the reset of the voltage amplifying means are released are set to different times from each other. Is constituted by switching means such as transistors and relays, by delaying the time at which the resetting of the voltage amplifying means is released, amplification of switching noise generated by the resetting of the conversion operation of the second converting means is reduced. Because of the prevention, the possibility of erroneous detection due to noise can be reduced.

In this specification, "resetting the voltage amplifying means" means to reduce the gain of the voltage amplifying means to a predetermined level (including 1) or to reduce its output voltage to zero (ground). Shall be included.

In each of the above structures, a driving means for operating a load based on the human body detection signal may be provided. According to this configuration, it is possible to operate the load only when a human body is detected.

[0025]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an electric configuration of a lighting control device which is an embodiment of an electric device having an infrared detecting device according to the present invention, and FIG. 2 (a) shows an I / V conversion. FIG. 3B is a circuit diagram illustrating a part of the circuit 2, FIG. 3B is a circuit diagram illustrating an example of the I / V conversion circuit 2, and FIG. 3 is a timing chart illustrating the operation of the I / V conversion circuit 2 when popcorn noise is input. It is a chart.

As shown in FIG. 1, the illumination control device includes a pyroelectric element 1, a current / voltage (I / V) conversion circuit 2, a switch circuit 3, a voltage amplifier 4, a switch circuit 5, It comprises an infrared detecting device 9 provided with a judging section 6, a control circuit 7, and a switch circuit 8, a driving circuit 10 and a lamp 11.

The pyroelectric element 1 includes a converging lens and the like, focuses infrared radiation energy in a predetermined detection area on a light receiving surface, and outputs a current corresponding to a change in the amount of received infrared light to the I / V conversion circuit 2. Is what you do.

The I / V conversion circuit 2 converts the current SIN input from the pyroelectric element 1 into a voltage SOUT and outputs the voltage SOUT to the voltage amplifying unit 4. This is to reset the conversion operation.

In FIG. 2, an I / V conversion circuit 2 charges a capacitor 21 with an input current SIN from a pyroelectric element 1 (FIG. 1).
Is configured to generate an output voltage SOUT with respect to a reference voltage (operating point) VREF input through the switch.

In order to prevent the conversion efficiency of the input current SIN from lowering, the resistance of the resistor 23 connected to the inverting input terminal of the operational amplifier 22 is set to a very large value, for example, several T (Tera) Ω. , Thereby making the CR time constant very large.

Therefore, the waveform of the popcorn noise is
As shown in FIG. 3A, the waveform rapidly rises and then immediately attenuates. However, when the input current SIN is popcorn noise, the output waveform is the CR of the I / V conversion circuit 2.
Since the time constant is very large, as shown in FIG.
The operating point VR rises sharply and then gradually decays.
You will settle in EF.

As shown in FIG. 2, in this embodiment, the switch circuit 3 is constituted by, for example, an FET, its gate is connected to the control circuit 7, and its source and drain are connected to both ends of the capacitor 21, respectively. Therefore,
When the switch circuit 3 is turned on by the control circuit 7 when the input current SIN is input, both ends of the capacitor 21 are short-circuited, and a buffer state is established. As shown in FIG. It will attenuate.

Returning to FIG. 1, the voltage amplifying section 4 amplifies the voltage SOUT input from the I / V conversion circuit 2. This voltage amplifying unit 3 is given the characteristics of a band-pass filter centered at about 1 Hz. This is because the change signal of the amount of infrared rays due to the movement of the human body has a frequency component centered at about 1 Hz. The switch circuit 5 resets the voltage amplifying unit 4 when turned on. In the present embodiment, the gain of the voltage amplifying unit 4 is reduced by a predetermined level as compared with the case where the voltage amplifying unit 4 is turned off. The level determination unit 6 determines whether or not the voltage amplified by the voltage amplification unit 4 is equal to or higher than a predetermined level, and outputs a predetermined determination signal (turns on the output signal) when the voltage is equal to or higher than the predetermined level. .

The control circuit 7 has the following functions: In an initial state (standby mode), the switch circuits 3, 5, 8
Is turned off; the switch circuit 3 is turned on for a predetermined time T1 from the time when the predetermined judgment signal is input from the level judgment unit 6 to lower the conversion impedance of the I / V conversion circuit 2 (reset state); The switch circuit 5 is turned on for a predetermined time T2 from the time when the predetermined determination signal is input from the level determination unit 6 to lower the gain of the voltage amplifying unit 4 (reset state); The switch circuit 8 is turned on for a predetermined time T3 (human body detection mode period) from the time when the power supply returns to the off state, and the level determination unit 6 and the drive circuit 10 are directly connected.

When a predetermined judgment signal is output from the level judgment unit 6 when the switch circuit 8 is turned on, the drive circuit 10 operates only while the judgment signal is being output or for a predetermined time slightly longer than that. A drive current is supplied to the lamp 11 to turn on the lamp 11.

Next, the operation procedure of the infrared detector 9 will be described with reference to the flowchart of FIG.

In FIG. 4, in the initial standby mode, the switch circuits 3, 5, and 8 are turned off (step S10). Next, it is determined whether or not there is a determination signal, that is, whether or not the amplitude of the output voltage from the voltage amplifier 4 is equal to or greater than a predetermined amplitude (step S20).
If there is no determination signal (NO in step S20), the process returns to step S10, and if there is a determination signal (YES in step S20), each of switch circuits 3 and 5 has a predetermined time T
1 and T2 are turned on (step S30).

Next, it is determined whether or not both of the switch circuits 3 and 5 are turned off (step S40), and the process waits until both of them are turned off (NO in step S40), and when both are turned off (step S40). YES), the switch circuit 8 is turned on for a predetermined time T3, and the mode is set to the human body detection mode (step S50).

This mode is continued until the switch circuit 8 is turned off after the predetermined time T3 has elapsed (NO in step S60), and when the switch circuit 8 is turned off (YES in step S60), the process proceeds to step S10. Return to standby mode.

Next, the operation of each unit when a signal is output from the pyroelectric element will be described with reference to the timing charts of FIGS. FIG. 5 shows a case where a signal from a human body is input, and FIG. 6 shows a case where popcorn noise is input.

First, in FIG. 5, at time t1, the switch circuits 3, 5, and 8 are turned off in the standby mode.
At time t2, when the human body is detected and the output signal of the voltage amplifying unit 4 exceeds a predetermined level, the output signal of the level determining unit 6 is turned on and the switch circuits 3 and 5 are turned on. At this time, when a human body is detected, the amplitude of the output signal of the voltage amplifying unit 4 changes gradually as shown in the figure.

First, the switch circuit 3 is turned off at time t3 after a predetermined time T1 has elapsed from time t2. further,
At time t4 after a predetermined time T2 has elapsed from time t2, the switch circuit 5 is turned off and the switch circuit 8 is turned on.

When the switch circuit 8 is turned on at time t4, the output signal of the voltage amplifying section 4 is still higher than the predetermined level, so that the output signal of the level judging section 6 remains on. Is turned on.

When the output signal of the voltage amplifying section 4 becomes lower than the predetermined level at time t5, the output signal of the level judging section 6 is turned off, whereby the input signal of the drive circuit 10 is also turned off. Then, at time t6 when a predetermined time T3 has elapsed from time t4, the switch circuit 8 is turned off, and the operation returns to the standby mode.

The human body detection mode is a mode from when the switch circuit 8 is turned on at time t4 until a predetermined time T3 elapses. During this time, when the output signal of the voltage amplifying section 4 becomes higher than the predetermined level, the level judging section 6, the output signal of the drive circuit 10 is turned on.

Next, in FIG. 6, at time t11, the switching mode is switched to the standby mode in the same manner as in FIG.
8 is turned off.

At time t12, when the output signal of the voltage amplifying section 4 becomes higher than a predetermined level due to popcorn noise, the output signal of the level judging section 6 is turned on and the switch circuits 3 and 5 are turned on.

Next, since the input signal is popcorn noise, the output signal of the voltage amplifying unit 4 rises rapidly as shown in the figure, and then rapidly attenuates. The output signal of the level determination unit 6 is turned off.

Next, as in the case of FIG.
The switch circuit 3 is turned off at time t14 after a lapse of a predetermined time T1 from. Further, a predetermined time T from time t12
At time t15 after 2 has elapsed, the switch circuit 5 is turned off and the switch circuit 8 is turned on.

The human body detection mode is set until the predetermined time T3 elapses after the switch circuit 8 is turned on at time t15, but if the input signal is popcorn noise, the switch circuit 8 is turned on at time t15. When
Since the output signal of the voltage amplifying unit 4 is already lower than the predetermined level, the output signal of the level determining unit 6 is off, and the input signal of the drive circuit 10 is off. Therefore, when the input signal is popcorn noise, the driving circuit 10
The input signal to is never turned on.

Then, at time t16 when a predetermined time T3 has elapsed from time t15, the switch circuit 8 is turned off, and the operation returns to the standby mode.

As described above, according to the present embodiment, in the standby mode, the switch circuit 8 is turned off and the infrared detector 9 is turned off.
Signal is not output from the
Is higher than a predetermined level and a predetermined judgment signal is output from the level judgment section 6, the switch circuits 3 and 5 are turned off once, and the conversion impedance of the I / V conversion circuit 2 and the voltage amplification section 4 are turned off. Is reduced to a reset state, the switch circuits 3 and 5 are turned off, and the switch circuit 8 is switched off for a predetermined time T3 from the time when the reset state is released.
Is turned on and the human body detection mode is set, so that if the first input signal is caused by popcorn noise, the output signal of the voltage amplifying unit 4 is already lower than a predetermined level when the reset state is released. Therefore, it is possible to reliably prevent a signal due to popcorn noise from being erroneously detected as a human body detection signal, with a simple configuration without increasing the number of components.

If the initially input signal is due to the human body, it is a slowly changing signal having a frequency component centered at about 1 Hz. During the detection mode, the output signal of the voltage amplifying unit 4 becomes higher than a predetermined level and a predetermined judgment signal is output from the level judgment unit 6, so that the detection by the human body can be reliably performed without overlooking the signal. can do.

Here, in the present embodiment, the switch circuit 5 is turned on at the time when the switch circuit 3 is turned off from on and the reset state of the I / V conversion circuit 2 is released (for example, time t3 in FIG. 5). The time when the voltage amplifier 4 is released from the reset state by returning from on to off (for example, time t
The effect of delaying 4) will be described.

When the switch circuit 3 is turned on, the I / V conversion circuit 2 is put in a buffer state, so that the output signal level of the I / V conversion circuit 2 immediately attenuates to the operating point VREF. When the switch circuit 3 is turned off and the reset state is released, the switching noise causes electric charges to be accumulated on the side of the resistor 23 (FIG. 2) having a very high resistance value. The waveform of the output voltage SOUT of the conversion circuit 2 sharply rises, and thereafter gradually decreases due to a large time constant, and the level reaches the operating point VREF.

Here, when the switch circuit 5 is already turned off at the time when the switch circuit 3 is turned off, or when the switch circuit 5 is turned off immediately after the time when the switch circuit 3 is turned off, the switching noise is generated. Since a voltage of about 1 Hz is amplified by the voltage amplifying unit 4, this causes erroneous detection.

However, according to the present embodiment, the time at which the reset state of the voltage amplifier 4 is released is delayed with respect to the time at which the reset state of the I / V conversion circuit 2 is released. It is possible to prevent the switching noise due to the OFF from affecting the next stage circuit.

As for the time difference between the reset release times of the two (T2-T1 in this embodiment because the reset starts at the same time), the voltage level of about 1 Hz of the switching noise due to the turning off of the switch circuit 3 can be ignored. It may be set to the time until it drops to the extent.

The switching noise caused by the reset release of the voltage amplifying unit 4 does not significantly affect the entire circuit because there is no circuit that amplifies the voltage level in the subsequent stage.

The present invention is not limited to the above-described embodiment, but may employ the following modifications.

(1) In the above embodiment, the switch circuits 3 and 5 are simultaneously turned on, and the I / V conversion circuit 2 and the voltage amplifier 4 are simultaneously reset. However, the present invention is not limited to this. May be reset. In this case, if the reset release timings are different from each other, the influence of the switching noise can be reduced as described above.

(2) In the above embodiment, the switch circuit 5
The resetting of the voltage amplifying unit 4 by turning on is to reduce the gain by a predetermined level as compared with when the voltage is off, but is not limited to this, and the gain is set to 1 (no amplification).
Or the output voltage may be set to the ground level.

(3) In the above embodiment, the illumination control device controls the on / off of the lamp 10, but is not limited to this. For example, the present invention is applied to general electric equipment in which a load is operated by a driving unit when a human body is detected, such as an intrusion alarm device in which a load is replaced by a lamp and a buzzer is generated by the driving circuit 10 when a human body is detected, or the like. Can be.

[0064]

As described above, according to the first aspect of the present invention, a predetermined judgment signal is output when the amplified voltage signal is equal to or higher than a predetermined level, and reset when this judgment signal is output. Means for resetting the conversion operation of the second conversion means for a predetermined reset time, and outputting the predetermined human body detection signal when the above determination signal is output within a predetermined human body detection time from the time when the reset is released. Therefore, with a simple configuration, it is possible to reliably prevent a signal due to popcorn noise from being erroneously detected as a human body.

According to the second aspect of the present invention, the time at which the reset of the conversion operation of the second converting means is released and the time at which the reset of the voltage amplifying means are released are set to different times. In addition, amplification of noise generated by canceling the reset of the conversion operation of the second conversion means is prevented, and the possibility of erroneous detection due to noise can be reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an electrical configuration of a lighting control device which is an embodiment of an electric device including an infrared detection device according to the present invention.

FIG. 2A is a circuit diagram showing a part of an I / V conversion circuit,
(b) is a circuit diagram showing an example of the I / V conversion circuit.

FIGS. 3A, 3B, and 3C are timing charts illustrating the operation of the I / V conversion circuit when popcorn noise is input.

FIG. 4 is a flowchart showing an operation procedure of the infrared detection device.

FIG. 5 is a timing chart showing the operation of each unit when a signal from a human body is input.

FIG. 6 is a timing chart showing the operation of each unit when popcorn noise is input.

FIG. 7 is a block diagram illustrating an example of an infrared detection device capable of preventing erroneous detection due to popcorn noise.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Pyroelectric element (1st conversion means) 2 Current-voltage conversion circuit (2nd conversion means) 3 Switch circuit (reset means) 4 Voltage amplifier 5 Switch circuit (2nd reset means) 6 Level determination part 7 Control circuit (reset) Control means, detection control means, second
Reset control means) 8 switch circuit (detection control means) 9 infrared detection device 10 drive circuit 11 lamp T1 predetermined time (predetermined reset time) T2 predetermined time (predetermined second reset time) T3 predetermined time (Predetermined human body detection time)

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shinji Sakamoto 1048 Kazuma Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. Inventor Yorinobu Murayama 1048 Kadoma Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Works F-term (reference) 2G065 AB02 BA13 BC03 BC14 BC22 BD04 CA12 DA20

Claims (2)

[Claims] 1. A first conversion means for detecting a change in infrared radiation energy in a predetermined detection area, converting the change into a current and outputting the current, and converting the current output by the first conversion means into a voltage. Converting means for amplifying and outputting a signal of a predetermined low frequency range among the voltage signals output by the second converting means, and a voltage output by the voltage amplifying means. Level determining means for outputting a predetermined determination signal when the signal is equal to or higher than a predetermined level; resetting means for resetting the conversion operation of the second converting means; (2) reset control means for resetting the conversion operation of the conversion means for a predetermined reset time;
An infrared detection device comprising: detection control means for outputting a predetermined human body detection signal when the determination signal is output within a predetermined human body detection time from the time point when the reset by the reset control means is released. 2. The infrared detecting device according to claim 1, wherein said second reset means resets said voltage amplifying means, and said second reset means sets said voltage amplifying means to a predetermined voltage when said determination signal is output. A second reset control means for resetting for a second reset time, wherein a reset release time by the reset control means and the second reset control means;
The detection control means is set to a time different from the reset release time by the reset control means, and the detection control means sets the determination signal within the human body detection time from the release time of both resets by the reset control means and the second reset control means. An infrared detection device that outputs the human body detection signal when is output.