JPH10239151A - Infrared detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an infrared detector that is reduced in size further while being made to have no malfunction due to noise. SOLUTION: At least a current/voltage conversion means 20 and a human body detection signal output means 50 are formed on the same P type semiconductor substrate 70 wherein the human body detection signal output means 50 is formed in an N well region 71 formed on the P type semiconductor substrate 70. A P channel field effect transistor has a gate 53G connected with the output end of a comparison means 40, a source 53S connected with a power supply 51 and a drain connected with an external load, e.g. an alarm delivery means.

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 energy radiated from a human body and detecting the presence or movement of the human body. And a miniaturized infrared detector.

[0002]

2. Description of the Related Art FIG. 9 is a circuit block diagram schematically showing a configuration of a conventional infrared detector. The conventional infrared detector 101 includes a commercially available pyroelectric sensor 10, a voltage amplifying unit 30 formed on a semiconductor substrate different from the pyroelectric sensor 10, a comparing unit 40, and a human body detection signal output unit 50. .

In the pyroelectric sensor 10, when heat of a human body or the like is detected, a pyroelectric element 11 that outputs a current corresponding to the heat is detected.
And current-voltage conversion means 20 for converting an output current output when the pyroelectric element 11 detects heat to a voltage. The pyroelectric element 11 and the current-voltage conversion means 20 are separately provided. Are formed on the substrates 12 and 13, which are sealed with a resin member 14.

The current-to-voltage conversion means 20 includes a current-voltage conversion resistor 21 for converting an output current output from the pyroelectric element 11 into a voltage, and a field effect transistor 22 such as a JFET for impedance conversion. The output current of several fA outputted from the pyroelectric element 11 by the energy of the weak infrared rays emitted from the human body is converted into a very small voltage of several tens μV, and the drain current of the field effect transistor 22 is reduced.
D to output. Therefore, the resistance 21
Requires a very high resistance value of 100 GΩ or more, and the impedance of the input section of the pyroelectric element 11 is extremely high.

The drain 22 of the field effect transistor 22
D is connected to an input pad 32 of a voltage amplifying unit 30 formed on a substrate 31 separate from the pyroelectric sensor 10.
The input pad 32 is a member formed via an insulating film on the semiconductor substrate 31 on which the voltage amplifying unit 30 is formed. The voltage amplifying unit 30 includes amplifiers 33, 33, capacitance units 34, 34, 34, resistors 35, 35, 35,
It is an RC-coupled amplifying circuit provided with a power supply 36, and amplifies a minute voltage signal output from the drain 22D of the field-effect transistor 22 only in a frequency band of about 0.1 to 10 Hz, so that human Only the frequency component of the output signal from the sensor 10 accompanying the movement is amplified, and the amplified voltage signal is output from the output terminal 37.

The comparing means 40 includes a window comparator section 41 and a logic gate circuit 42. When the voltage signal amplified by the voltage amplifying means 30 is input, the input voltage signal is compared with a threshold value. It has become. In this example, the window comparator unit 41 is provided with two threshold values, a threshold value determined by the resistor 43 and a threshold value determined by the resistors 43 and 44. A NAND circuit is used as the logic gate circuit 42. When the amplitude of the voltage signal exceeds a certain level, a signal (H level or L level) is output from the output section of the logic gate circuit 42 to the human body detection signal output means 50.

The human body detection signal output means 50 is usually a CMOS inverter constructed by connecting an N-channel field effect transistor 52 and a P-channel field effect transistor 53 in series with a power supply 51 for the purpose of reducing power consumption and the like. An output of the logic gate circuit 42 is connected to the gate 50G of the CMOS inverter circuit, and the output of the logic gate circuit 42 is connected to an external load circuit (not shown) such as an alarm issuing means whose terminal is grounded. Pad 54 is CM
The source is connected to the drain 50D of the OS inverter circuit, the source 52S of the N-channel field-effect transistor 52 is grounded, and the source 53S of the P-channel field-effect transistor 53 is connected to the power supply 51. The input pad 32 is a member formed via an insulating film on the semiconductor substrate 55 on which the human body detection signal output means 50 is formed.

When a signal output from the output section of the logic gate circuit 42 is input to the gate 50G, it is determined that a human body has been detected, and the signal is output to the output pad 54 as a voltage change.

[0009]

By the way, there has been a long-felt need for an infrared detector that has a smaller size, a higher S / N ratio, and a lower malfunction. In order to meet the demand for miniaturization, it is conceivable to form everything from the current-to-voltage conversion means 20 of the infrared detector 101 to the human body detection signal output means 50 at the subsequent stage on the same semiconductor substrate to form a one-chip IC. Can be

FIG. 10 is a circuit block diagram schematically showing an infrared detector in which a conventional circuit of the infrared detector 101 is directly formed into a one-chip IC, and FIG.
FIG. 1 is an explanatory diagram schematically illustrating a problem that occurs on a substrate when a conventional circuit is directly converted into a one-chip IC.
Here, a case where a P-type semiconductor substrate is used as a semiconductor substrate will be described as an example. Note that in FIGS. 10 and 11,
Members corresponding to those shown in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 11, reference numeral 60 denotes a current-to-voltage converter 20, a voltage amplifier 30, and a comparator 4.
0 shows a signal processing unit composed of “0” and “0”. Also,
62 indicates an input protection unit of the N-channel field effect transistor 52, 63 indicates an input protection unit of the signal processing unit 60, and 64 indicates an input protection unit of the P-channel field effect transistor 53. Also, Rx is the semiconductor substrate 70
Is the parasitic resistance formed on the substrate 70 when the N-channel field effect transistor 52 is formed.
i indicates a parasitic capacitance formed on the substrate 70 when the input protection unit 63 of the signal processing unit 60 is formed.

In the infrared detector 101A in which the conventional circuit is directly converted into a one-chip IC, the one-chip IC includes:
A very high impedance of 100 GΩ or more and a high gain, and a place where the voltage fluctuates digitally exist on the same substrate 70. Specifically, when the human body detection signal output means 50 is configured by a CMOS inverter circuit, the input protection unit 63 of the signal processing unit 60, P
The source 53S and the drain 53D of the channel field effect transistor 53 are formed on the same semiconductor substrate 70.

The source 53S of the P-channel field effect transistor 53 constituting the CMOS inverter circuit
The current flowing between the gate and the drain 53D is directly
0, the source 53S and the drain 50D
There is a problem that a part of the signal flowing from the substrate to the substrate 70 is transmitted through the substrate 70 and fed back to the input protection unit 63.

More specifically, a signal (H (1) or L (0)) output from the logic gate circuit 42 which detects a human body is supplied to the gate of the human body detection signal output means 50 constituted by a CMOS inverter circuit. When output to 54G, one of the N-channel field-effect transistor 52 and the P-channel field-effect transistor 53 is turned on,
The other is turned off and the drain 5 of the human body detection signal output means 50 is turned off.
A voltage having a variation width substantially equal to the power supply voltage VDD is output to 0D.

When a CMOS inverter circuit is formed as a human body detection signal output means 50 on the P-type semiconductor substrate 70, the substrate 70 is disposed between the drain 52D of the N-channel field effect transistor 52 included in the CMOS inverter circuit and the substrate 70. Are N-channel field effect transistors 52
There is a parasitic capacitance Cn formed at the time of formation of
In the CMOS inverter circuit constituting such an output unit, since the size of each transistor is large, the parasitic capacitance C
n is also very large.

When the output voltage is inverted, the drain 50D
Changes to a voltage VDD having a width of change substantially equal to the power supply voltage VDD.

[0016]

(Equation 1)

The electric charge is injected into the substrate 70. Substrate 70
Is grounded at each point and is fixed at the GND potential, but has a finite resistance value.
The steep change (digital change) of the voltage at 0D is transmitted to the substrate 70. Then, a steep change in the voltage output to the drain 50D is fed back to the input protection unit 63, and the fed-back signal is amplified by the voltage amplifying unit 30 and sent from the logic gate circuit 42 of the comparing unit 40 to the noise signal. As a result, the infrared detector 101A malfunctions, and if the conventional circuit is directly converted into a one-chip IC, the reliability of the infrared detector is impaired.

Further, in the worst case, if an output signal is output from the drain 50D to the output pad 54, it is always amplified and fed back to the output pad 54 via the input protection unit 63. Infrared detector 101A
However, there is a possibility that the oscillation state is always generated. The present invention has been made in order to solve the above problems, all circuits from the current-voltage conversion means to the human body detection signal output means at the subsequent stage are formed on the same semiconductor substrate,
It is an object of the present invention to provide an infrared detector which is reduced in size to one chip and has a circuit in which the infrared detector does not easily malfunction.

[0019]

In the infrared detector according to the present invention, when detecting heat of a human body or the like, a pyroelectric element for outputting a current corresponding to the heat, and the pyroelectric element detects the heat. Current-voltage conversion means for converting an output current to be output to a voltage, a voltage amplification means for amplifying an output signal output from the current-voltage conversion means, and a signal output from an output terminal of the voltage amplification means. The infrared detector, comprising: a comparison unit that compares the threshold value with the threshold value; and a human body detection signal output unit that outputs a detection signal that detects a human body in response to a signal output from the comparison unit. Means and a human body detection signal output means are formed on the same P-type conductive type semiconductor substrate, and the human body detection signal output means is formed in an N-well region formed on the P-type semiconductor substrate; Out of End gate is connected to a source connected to a power source, and is characterized in that a P-channel field effect transistor in which an external load such as an alarm issuance means to the drain is connected.

In the infrared detector according to the present invention, the current-voltage conversion means, the voltage amplification means, the comparison means and the human body detection signal output means are formed on the same P-type conductive semiconductor substrate. Can be reduced in size. In addition, a P-channel field effect transistor is used as the human body detection signal output means instead of a CMOS inverter circuit. As a result, the current when the gate of the P-channel field-effect transistor is turned on is reduced by the source-source voltage in the N-well region.
While flowing between the drains, it is difficult to flow to the P-type semiconductor substrate outside the N-well region, and the structure of the human body detection signal output means has no direct parasitic capacitance on the P-type semiconductor substrate. The charge generated when a voltage change occurs in the drain of the P-channel field-effect transistor is reduced, and the charge is transmitted through the P-type semiconductor substrate outside the N-well region to serve as an input part of the voltage amplification means. Since it is difficult to transmit to the protection unit, it is difficult to feed back via the input unit of the amplification unit.

According to a second aspect of the present invention, there is provided a voltage limiting circuit for limiting a voltage output from a drain of a P-channel field-effect transistor in parallel with the P-channel field-effect transistor of the infrared detector according to the first aspect. Are connected. Here, the voltage limiting circuit means a circuit that limits the voltage to a voltage value lower than the voltage value of the power supply potential to which the source is connected.

In the infrared detector according to the second aspect, a voltage limiting circuit is provided in parallel between the source and the drain of the P-channel field-effect transistor, and the voltage of the drain when the gate of the P-channel field-effect transistor is turned on is supplied to the power supply. Since the charge injected into the N-well region when the gate of the P-channel field-effect transistor is turned on is further reduced, the charge at the time when a voltage change occurs at the drain of the P-channel field-effect transistor is limited. Are hardly transmitted through the P-type semiconductor substrate outside the N-well region and to the input protection unit serving as the input unit of the voltage amplification unit and the output terminal of the current-voltage conversion unit.

Here, a specific example of the "voltage limiting circuit" is a Zener diode. According to a third aspect of the present invention, a constant current circuit is provided between the output terminal of the comparing means of the infrared detector according to the first aspect and the source of the P-channel field effect transistor and a power supply connected to the source. It is characterized by being connected in parallel.

In the infrared detector according to the third aspect, a constant current circuit is connected in parallel between the output terminal of the current-voltage conversion amplifying means and the source of the P-channel field effect transistor and a power supply connected to the source. The current between the source and the drain when the gate of the P-channel field-effect transistor is turned on is constant regardless of the magnitude of the external load connected to the output pad. Therefore, if the human body detection signal output means is constituted by a low current source so as to limit the amount of charge injected into the N-well region, the fluctuation in the potential of the P-type semiconductor substrate can be further reduced, and Since it is difficult to transmit to the input protection unit serving as the input unit of the voltage amplifying unit and the output terminal of the current-voltage conversion unit via the mold semiconductor substrate, it is difficult to feed back through the input unit of the amplifying unit.

In the infrared detector according to the present invention, when the heat of the human body or the like is detected, a pyroelectric element that outputs a current corresponding to the heat, and an output current that is output when the pyroelectric element detects the heat. To a voltage, a voltage amplifying means for amplifying an output signal output from the current-voltage converting means, and comparing a signal output from an output terminal of the voltage amplifying means with a predetermined threshold. An infrared detector comprising: a comparing unit; and a human body detection signal output unit that outputs a detection signal of detecting a human body in response to a signal output from the comparison unit. Means are formed on the same N-type semiconductor substrate, and
The human body detection signal output means is formed in a P well region formed in the N-type semiconductor substrate, the gate is connected to the output terminal of the comparison means, the source is connected to the ground, and the drain is provided with an alarm issuing means. An N-channel field-effect transistor to which an external load is connected is characterized.

In the infrared detector according to the present invention, since the current-voltage conversion means, the voltage amplification means, the comparison means and the human body detection signal output means are formed on the same N-type semiconductor substrate, the infrared detector can be downsized. Can be planned. In addition, the human body detection signal output means is not a CMOS inverter circuit but an N-channel field effect transistor. Thus, the current when the gate of the N-channel field-effect transistor is turned on flows between the source and the drain in the P-well region, but hardly flows to the N-type semiconductor substrate outside the P-well region. Since the configuration of the output means is eliminated from the transistor having the parasitic capacitance directly on the N-type semiconductor substrate, the charge generated when the voltage of the drain of the N-channel field-effect transistor changes in the N-type semiconductor substrate is reduced. Since it is difficult for the electric charge to propagate through the N-type semiconductor substrate outside the P-well region and to the input protection unit serving as the input unit of the voltage amplifying unit, it is difficult to feed back through the input unit of the amplifying unit.

According to a fifth aspect of the present invention, there is provided an infrared detector according to the fourth aspect, wherein the voltage which limits a voltage output from the drain of the N-channel field-effect transistor in parallel with the N-channel field-effect transistor of the infrared detector. A limiting circuit is connected. 6. The infrared detector according to claim 5, wherein a voltage limiting circuit is connected in parallel between a source connecting the power source of the N-channel field-effect transistor and the power supply and the output pad, and between the ground and the ground. The voltage of the drain when the gate of the effect transistor is turned on is limited to the power supply voltage or less, and the charge injected into the P-well region when the gate of the N-channel field effect transistor is turned on is further reduced. The electric charge when a voltage change occurs in the drain of the transistor hardly propagates through the N-type semiconductor substrate outside the P-well region and to the input protection unit serving as the input unit of the voltage amplifying unit.

Here, the "voltage limiting circuit" includes, for example, a Zener diode. According to a sixth aspect of the present invention, there is provided an infrared detector comprising a constant current circuit between an output terminal of the comparison means of the infrared detector according to the fourth aspect and a source of the N-channel field effect transistor and a power supply connected to the source. It is characterized by being connected in parallel.

In the infrared detector according to the present invention, a constant current circuit is connected in parallel between the output terminal of the current-voltage conversion amplifying means and the source of the N-channel field effect transistor and a power supply connected to the source. The current between the source and the drain when the gate of the N-channel field-effect transistor is turned on is made constant regardless of the magnitude of the external load connected to the output pad. Therefore, if the human body detection signal output means is constituted by a low current source so as to limit the amount of charge injected into the P well region, the fluctuation in the potential of the N-type semiconductor substrate can be further reduced, and Since it is difficult to transmit to the input protection unit serving as the input unit of the voltage amplifying unit via the semiconductor substrate, it is difficult to feed back through the input unit of the amplifying unit.

[0030]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) In this example, an example using a P-type semiconductor substrate will be described. FIG. 1 is a circuit block diagram schematically showing the configuration of the infrared detector according to the present invention.

When the infrared detector 1 detects heat of a human body or the like, the pyroelectric element 11 outputs a current corresponding to the heat.
A current-to-voltage converter 20 for converting an output current output when the pyroelectric element 11 detects heat to a voltage; a voltage amplifying unit 30 for amplifying an output signal output from the current-voltage converter 20; A comparing means 40 for comparing a signal output from the output terminal 37 of the amplifying means 30 with a predetermined threshold value;
And a human body detection signal output means 50 for outputting a detection signal for detecting a human body.

The infrared detector 1 differs from the conventional infrared detector 101 in that at least the current-voltage conversion means 20 and the human body detection signal output means 50 are formed on the same P-type semiconductor substrate 70. I have. More specifically, in this example, all of the current-voltage conversion means 20, the voltage amplification means 30, the comparison means 40, and the human body detection signal output means 50 are formed on the same P-type semiconductor substrate 70.

Further, the infrared detector 1 uses a P-channel field effect transistor (PMOS) as the human body detection signal output means 50. In this example, an N-well region 71 is formed in a predetermined region of a P-type semiconductor substrate 70 as a human body detection signal output unit 50, and a P-channel field effect transistor (PMOS) 53 is used in the N-well region 71. In that the human body detection signal output means 50
Conventional infrared detector 1 having MOS inverter circuit
01 is different.

A P-channel field-effect transistor (PMO)
S) The gate 53G of 53 is connected to the output terminal of the comparison means 40, the source 53S is connected to the power supply 51, and the drain 53D is connected to the output pad 54. The output pad 54 is connected to an external load (not shown) such as alarm issuing means whose terminal is connected to the ground.

In the infrared detector 1, the configuration of the current-to-voltage converter 20 is the same as that of the conventional current-to-voltage converter 20, and the output current output from the pyroelectric element 11 is Current-voltage conversion resistor 2 for converting to voltage
1 and a field effect transistor 22 such as a JFET for impedance conversion. The output current of several fA output from the pyroelectric element 11 by the weak infrared energy emitted from the human body is reduced by several tens μV. The voltage is output from the drain 22D of the field effect transistor 22 as an appropriate voltage. The pyroelectric element 11 is formed on a substrate 12 separate from the P-type semiconductor substrate 70, and the drain 22 </ b> D of the field effect transistor 22 is connected to the input pad 32 of the voltage amplifier 30.

The configuration of the voltage amplifying means 30 is the same as that of the conventional voltage amplifying means 30, and includes amplifiers 33, 33, capacitance means 34, 34, 34, and a resistor 3.
5, 35, and a power supply 36, and amplifies a minute voltage signal output from the drain 22D of the field effect transistor 22 only in a frequency band of about 0.1 to 10 Hz. Thus, only the frequency component of the output signal from the sensor accompanying the movement of the person is amplified, and the amplified voltage signal is output from the output terminal 37.

The structure of the comparing means 40 is the same as that of the conventional comparing means 40. The comparing means 40 includes a window comparator section 41 and a logic gate circuit 42. When the input voltage signal is input, the input voltage signal is compared with a threshold value. In this example, two threshold values are provided in the window comparator section 41, and a NAND circuit is used as the logic gate circuit 42. Therefore, when the amplitude of the voltage signal exceeds a certain level, the logic gate circuit 42 A signal (H level or L level) is output to the human body detection signal output means 50 from the output section of the above.

FIG. 2 is a diagram mainly showing the human body detection signal output means 50 of the infrared detector 1. FIG. 2A is a circuit diagram of the human body detection signal output means 50, and FIG. )
FIG. 4 is an explanatory diagram schematically illustrating a relationship between the human body detection signal output unit 50 and the input protection unit 63 of the voltage amplification unit 30. In FIG. 2, members corresponding to those shown in FIG.
Corresponding reference numerals are assigned and description thereof will be omitted. FIG.
Medium 60 is current-to-voltage conversion means 20, voltage amplification means 30
3 shows a signal processing unit constituted by the comparison means 40. 62 is a P-channel field effect transistor 5
3 denotes an input protection unit, 63 denotes an input protection unit of the signal processing unit 60, and Ci denotes a parasitic capacitance formed on the P-type semiconductor substrate 70 when the input protection unit 63 of the signal processing unit 60 is formed. I have. 64 has a terminal connected to the ground,
2 shows an N diffusion layer that defines a reference potential of the semiconductor substrate 70.

In the infrared detector 1, the current-voltage conversion means 20, the voltage amplification means 30, the comparison means 40 and the human body detection signal output means 50 are formed on the same P-type semiconductor substrate 70, so that the infrared detector can be downsized. Can be achieved. In addition, the infrared detector 1 uses the P-type semiconductor substrate 70 and uses the P-channel field effect transistor 5 instead of the CMOS inverter circuit type.
3 and a P-channel field effect transistor 53
Is connected to the output pad 54 to form an open drain structure.

Therefore, as is apparent from a comparison between FIG. 2 and FIG. 11, the infrared detector 1 employs a configuration in which the N-channel field effect transistor is eliminated from the human body detection signal output means 50. The parasitic capacitance Cn formed in the P-type semiconductor substrate 70 when the N-channel field-effect transistor 52 is formed, which exists in the circuit as shown in FIG.
Can be eliminated. Thus, when the gate 53G of the P-channel field-effect transistor 53 is turned on, noise transmitted from the drain 53D to the input protection unit 63 via the P-type semiconductor substrate 70 can be significantly reduced. Although a large parasitic capacitance exists between the drain 53D of the P-channel field-effect transistor 53 and the N-well region 71, the N-well region 71 is fixed to a low impedance by the power supply 51, so that the P-type semiconductor The parasitic capacitance is much smaller than when an N-channel field effect transistor is formed on the substrate 70.

When performing signal processing such as the infrared detector 1, the current-voltage conversion means 20, the voltage amplification means 30,
1 / f generated by an integrated circuit (IC) in which circuits such as the comparison means 40 and the human body detection signal output means 50 are formed.
Since noise becomes a problem, the amplifiers 33, 33 are replaced with P-channel field-effect transistors (PMOS) that are advantageous for low noise.
It is common practice to have an input configuration. Therefore,
Current-voltage conversion means 20, voltage amplification means 30, comparison means 4
If a P-type semiconductor substrate 70 is used as the semiconductor substrate forming the 0 and human body detection signal output means 50,
In order to form the amplifiers 33, 33 having a channel field effect transistor (PMOS) input configuration, the amplifiers 33, 33
In order to form the third P-channel field-effect transistor (PMOS), it is necessary to form an N-well region in the P-type semiconductor substrate 70. As a result, the P-channel field-effect transistor (PMOS) is , The P-type semiconductor substrate 70 and the amplifier 3
There is also an advantage that the substrate potentials of the input transistors 3 and 33 can be set freely. Therefore, the P-type semiconductor substrate 7
0, and the human body detection signal output means 50 is constituted by the P-channel field effect transistor 53.
It is also preferable from the advantage that the substrate potentials of the input transistors 3 and 33 can be freely set.

FIG. 3 further shows a human body detection signal output means 50.
Of the P-channel field-effect transistor 53 in parallel with the P-channel field-effect transistor 53
An example is shown in which a voltage limiting circuit 81 for limiting the voltage output from D is connected. As such a voltage limiting circuit 81, for example, a Zener diode 83 shown in FIG. 3B can be mentioned as a preferable example. The voltage limiting circuit 81 includes a P-channel field effect transistor 53
The circuit is not limited to the Zener diode as long as the voltage can be limited to a voltage value lower than the voltage value of the potential VDD of the power supply 51 to which the source 53S is connected.

As shown in FIG. 2, the human body detection signal output means 50
When only the P-channel field-effect transistor 53 is provided, when the gate 53G is turned on and off, the drain 5
The width of change of the 3D output voltage is substantially equal to the potential VDD of the power supply 51, but the voltage limiting circuit 81 such as the Zener diode 83 is connected to the P-channel field-effect transistor 53.
When the gate 53G is turned on and off, the change width of the output voltage of the drain 53D is limited to the Zener voltage. When a P-type semiconductor substrate is used, the N well region 71 of the P-channel
Although the potential is fixed to the potential VDD of 1, the potential of the P-type semiconductor substrate 70 varies via the N-well region 71 because the resistance of the N-well region 71 is not zero. In this manner, if the change width of the output voltage of the drain 53D is limited by using the voltage limiting circuit 81, the charge injected into the N well region 71 is limited. The voltage / current change in the drain 53D to the portion 63
Malfunction of the infrared detector 1 due to feedback through the P-type semiconductor substrate 70 can be reduced.

FIG. 4 shows a current-voltage conversion amplifying means 40.
Of the P-channel field-effect transistor 53 constituting the human body detection signal output means 50 and the power supply 51 connected to the source 53S.
Are connected in parallel. Incidentally, in FIG.
Indicates a NOT logic gate. Constant current circuit 90
Is composed of a P-channel field-effect transistor 91, an N-channel field-effect transistor 92, and a constant current source 93.

The NOT logic gate 100 is connected to the output terminal of the NAND logic gate 42. The output terminal of the NOT logic gate 100 is a P-channel field effect transistor 9
The source 91S is connected to the source 92S of the N-channel field-effect transistor 92 and the source 53S of the P-channel field-effect transistor 53. The drain 91D of the P-channel field-effect transistor 91 is connected to the drain 92D and the gate 92G of the N-channel field-effect transistor 92 and the gate 53G of the P-channel field-effect transistor 53. 92
Is connected to a constant current source 93, and the constant current source 93 is grounded.

In this circuit, for example, when H is output to the output terminal of the NAND logic gate 42, the output terminal of the NOT logic gate 100 outputs L, and at this time, the gate 91G of the P-channel field effect transistor 91 is Turns on, the gate 92G of the N-channel field effect transistor 92 turns off, and the gate 53 of the P-channel field effect transistor 53 turns on.
G is turned off. Then, when L is output to the output terminal of the NAND logic gate 42, the output terminal of the NOT logic gate 100 outputs H, and at this time, the gate 91G of the P-channel field effect transistor 91 turns off, and N
The gate 92G of the channel field effect transistor 92 turns on, and the gate 5G of the P channel field effect transistor 53 turns on.
3G is turned on.

When the gate 53G of the P-channel field effect transistor 53 is turned on, the gate 92G of the N-channel field effect transistor 92 is turned on, and the output pad 54 is provided between the source 53S and the drain 53D of the P-channel field effect transistor 53. Regardless of the size of the external load (not shown) connected to the
A constant current flows between the source 53S and the drain 53D.

Therefore, the human body detection signal output means 50 is composed of a low current source, and the constant current circuit 90 allows the drain 53D to be driven regardless of the size of an external load (not shown) connected to the output pad 54. If the output current is kept constant, the amount of charge injected into the N well region 71 is also limited, and the fluctuation in the potential of the P-type semiconductor substrate 70 can be further reduced. Through the semiconductor substrate 70 to the input protection unit 63,
Erroneous operation of the infrared detector 1 due to the feedback of the voltage / current change at the time can be reduced. (Embodiment 2) In this example, an example using an N-type semiconductor substrate will be described.

FIG. 5 is a circuit block diagram schematically showing the configuration of the infrared detector according to the present invention. The infrared detector 2 uses an N-type semiconductor substrate 70A, uses an N-channel field effect transistor (NMOS) 52 as the human body detection signal output means 50, and connects the human body detection signal output means 50 to a predetermined portion of the N-type semiconductor substrate 70A. Formed in the P-well region 71A formed in the region, the gate 52G is connected to the output terminal of the comparing means 40, the source 52S is connected to ground,
The point that the drain 52D is connected to the power supply 51 and the connection between the drain 52D and the power supply 51 is connected to an output pad 54 for connecting an external load circuit (not shown) such as alarm issuing means is detected by infrared rays. It is different from the container 1.

An N-channel field effect transistor (NMO)
S) The gate 52G of 52 is connected to the output terminal of the comparing means 40, the source 52S is connected to ground, and the drain 52D is connected to the output pad 54. The output pad 54 is connected to an external load (not shown) such as alarm issuing means whose terminal is connected to the ground.

The configuration of the current-voltage conversion means 20, the voltage amplification means 30, and the comparison means 40 is such that
The configuration is the same as that of the mold semiconductor substrate 70A except that the polarity is different. Therefore, the corresponding members are denoted by the corresponding reference numerals, and description thereof will be omitted. This infrared detector 2 differs from the conventional infrared detector 101 in that at least the current-voltage conversion means 20 and the human body detection signal output means 50 are formed on the same N-type semiconductor substrate 70A. More specifically, in this example, the current-voltage conversion means 2
0, the voltage amplifying means 30, the comparing means 40, and the human body detection signal output means 50 are all formed on the same N-type semiconductor substrate 70A.

Further, the infrared detector 2 uses an N-channel field effect transistor (NMOS) as the human body detection signal output means 50. In this example, the P-well region 71A is formed in a predetermined region of the N-type
N channel field effect transistor (NMOS) in 1A
52 is different from the conventional infrared detector 101 having a CMOS inverter circuit as the human body detection signal output means 50 in that the human body detection signal output means 50 is used.

FIG. 6 is a diagram mainly showing the human body detection signal output means 50 of the infrared detector 2. FIG. 6 (a) is a circuit diagram of the human body detection signal output means 50, and FIG. )
FIG. 4 is an explanatory diagram schematically illustrating a relationship between the human body detection signal output unit 50 and the input protection unit 63 of the voltage amplification unit 30. In FIG. 6, members corresponding to the members shown in FIG.
Corresponding reference numerals are assigned and description thereof will be omitted. still,
6, reference numeral 62 denotes an input protection unit of the N-channel field effect transistor 52, 63 denotes an input protection unit of the signal processing unit 60,
Ci indicates a parasitic capacitance formed on the N-type semiconductor substrate 70A when the input protection unit 63 of the signal processing unit 60 is formed. Reference numeral 64 denotes a P diffusion layer whose terminal is connected to the ground and defines a reference potential of the N well region 71A.

In the infrared detector 2, the current-voltage conversion means 20, the voltage amplification means 30, the comparison means 40, and the human body detection signal output means 50 are formed on the same N-type semiconductor substrate 70A. Can be achieved.
In addition, in the infrared detector 2, the N-type semiconductor substrate 70A
, The human body detection signal output means 50 is not composed of a CMOS inverter circuit, but is composed of only an N-channel field effect transistor 52, and a drain 53D of the N-channel field effect transistor 53 is connected to an output pad 54 to form an open drain structure. I have.

In the infrared detector 2, since the P-channel field effect transistor is eliminated from the human body detection signal output means 50, the parasitic capacitance formed on the N-type semiconductor substrate 70A when the P-channel field effect transistor 53 is formed. Cn can be eliminated. Thus, when the gate 52G of the N-channel field effect transistor 52 is turned on, it is possible to significantly reduce noise transmitted from the drain 52D to the input protection unit 63 via the N-type semiconductor substrate 70A.

In general, an N-channel field-effect transistor (NMOS) has a higher output current capability than a P-channel field-effect transistor (PMOS), and requires only a small area. There are advantages above. Moreover, the human body detection signal output means 5
0 is formed on the P-type semiconductor substrate 70A with an N-channel field effect transistor, since no parasitic capacitance is directly generated between the drain 52D of the N-channel field effect transistor 52 and the substrate 70A. Can be reduced.

FIG. 7 further shows a human body detection signal output means 50.
Of the N-channel field-effect transistor 52 in parallel with the N-channel field-effect transistor 52
An example is shown in which a voltage limiting circuit 81A for limiting the voltage output from D is connected. Such a voltage limiting circuit 81
As A, for example, a Zener diode 83 shown in FIG. 7B can be mentioned as a preferable example. still,
The voltage limiting circuit 81A is provided with a potential VD of the power supply 51 to which the source 52S of the N-channel field effect transistor 52 is connected.
The circuit is not limited to a Zener diode as long as the circuit can limit the voltage to a value lower than the voltage of D.

As described above, when the voltage limiting circuit 81A such as the Zener diode 83 is provided in parallel with the N-channel field-effect transistor 52, the change width of the output voltage of the drain 52D when the gate 52G is turned on and off is reduced to the Zener voltage. Limited. When the N-type semiconductor substrate 70A is used, the P-well region 71A of the N-channel field-effect transistor 52 is fixed at the reference potential,
Since the resistance of 1A is not zero, the potential of the N-type semiconductor substrate 70A fluctuates via the P-well region 71A. As described above, if the variation width of the output voltage of the drain 52D is limited by using the voltage limiting circuit 81A, the P well region 71A
The charge injected into the voltage amplifying means 30 is limited.
The malfunction of the infrared detector 2 due to the change in the voltage and the current at the drain 52D fed back to the input protection unit 63 via the N-type semiconductor substrate 70 to the input protection unit 63 can be reduced.

FIG. 8 shows the output terminal of the comparison means 40 and
The figure shows an example in which a constant current circuit 90A is connected in parallel between a source 52S of an N-channel field effect transistor 52 constituting the human body detection signal output means 50 and a power supply 51 connected to the source 52S. In FIG. 8, 100 is NOT.
The logic gate is shown. The constant current circuit 90A includes an N-channel field-effect transistor 94, a P-channel field-effect transistor 95, and a constant current source 96.

The NOT logic gate 100 is connected to the output terminal of the NAND logic gate 42. The output terminal of the NOT logic gate 100 is a P-channel field effect transistor 9
4, the source 94S is connected to the ground, and the drain 94D is connected to the gate 95G and the drain 95 of the P-channel field effect transistor 95.
D and the gate 5 of the N-channel field effect transistor 52
2G. The source 95S of the P-channel field-effect transistor 95 is connected to the ground, and the drain 95D is connected to the constant current source 96.

In this circuit, for example, when H is output to the output terminal of the NAND logic gate 42, the output terminal of the NOT logic gate 100 outputs L, and at this time, the gate 91G of the N-channel field effect transistor 94 is Turns on, the gate 52G of the N-channel field effect transistor 52 turns off, and the gate 95 of the P-channel field effect transistor 95 turns on.
G is turned on. When L is output to the output terminal of the NAND logic gate 42, the output terminal of the NOT logic gate 100 outputs H. At this time, the gate 94G of the N-channel field effect transistor 94 turns off,
The gate 52G of the channel field effect transistor 52 is turned on, and the gate 9 of the P channel field effect transistor 95 is turned on.
5G is turned on.

When the gate 52G of the N-channel field effect transistor 52 is turned on, the P-channel field effect transistor 95 is turned on, and the output pad 54 is connected between the source 52S and the drain 52D of the N-channel field effect transistor 52. Regardless of the magnitude of the external load, a constant current flows between the source 52S and the drain 52D by the current mirror.

Therefore, if the human body detection signal output means 50 is composed of a low current source and the output current output from the drain 52D is kept constant regardless of the size of the external load, the P well region 71A Since the amount of injected charge is also limited, the fluctuation of the potential of the N-type semiconductor substrate 70A can be further reduced, so that the voltage-current change at the drain 52D is supplied to the input protection unit 63 via the N-type semiconductor substrate 70A. Erroneous operation of the infrared detector 2 due to the feedback of.

[0064]

As described above in detail, in the infrared detector according to the first aspect, the current-voltage conversion means, the voltage amplification means, the comparison means and the human body detection signal output means are formed on the same P-type semiconductor substrate. As a result, the infrared detector can be reduced in size, and the human body detection signal output means is not a CMOS inverter circuit but a P-channel field-effect transistor. Since it is difficult to be transmitted to the input protection unit serving as the input unit of the means and is difficult to feed back through the input unit of the amplifying means, a malfunction is less likely to occur.

In the infrared detector according to the second aspect, a voltage limiting circuit is provided in parallel between the source and the drain of the P-channel field-effect transistor, and the voltage of the drain when the gate of the P-channel field-effect transistor is turned on is supplied to the power supply. Since the electric charge injected into the N-well region when the gate of the P-channel field-effect transistor is turned on is further reduced, the change in the voltage at the drain of the P-channel field-effect transistor is limited to the input portion of the voltage amplification means. It is difficult to transmit to the input protection unit and the output terminal of the current-voltage conversion unit, and it is difficult to feed back to the output pad via the input unit of the amplification unit, so that malfunction does not easily occur.

In the infrared detector according to the third aspect, a constant current circuit is connected in parallel between an output terminal of the comparing means and a source of the P-channel field effect transistor and a power supply connected to the source, and an output pad is provided. Since the current between the source and the drain when the gate of the P-channel field-effect transistor is turned on is constant irrespective of the magnitude of the external load connected to the, the human body detection signal output means is constituted by a low current source. , N
If the amount of charge injected into the well region is limited, P
A change in the voltage at the drain of the channel field-effect transistor is difficult to be transmitted to the input protection unit serving as the input unit of the voltage amplifying unit, and is difficult to feed back via the input unit of the amplifying unit.

In the infrared detector according to the fourth aspect, since the current-voltage conversion means, the voltage amplification means, the comparison means and the human body detection signal output means are formed on the same N-type semiconductor substrate, the size of the infrared detector can be reduced. Since an N-channel field effect transistor is used as a human body detection signal output means instead of a CMOS inverter circuit, a change in the voltage of the drain of the N-channel field effect transistor is applied to an input protection section serving as an input section of the voltage amplification means. Since it is hard to transmit and feedback is difficult via the input section of the amplifying means, a malfunction does not easily occur.

In the infrared detector according to the present invention, a voltage limiting circuit is connected in parallel between a source connecting the power source of the N-channel field-effect transistor and the power supply and the middle of a line connecting the output pad and ground. The drain voltage when the gate of the N-channel field-effect transistor is turned on is limited to the power supply voltage or less, and the charge injected into the P-type conductivity type well region when the gate of the N-channel field-effect transistor is turned on is further reduced. As a result, the charge at the time when a voltage change occurs at the drain of the N-channel field-effect transistor propagates through the N-type semiconductor substrate outside the P-well region, and the input protection unit and the current-voltage conversion unit serve as the input unit of the voltage amplification unit. And it is difficult to feed back to the output pad via the input part of the amplifying means, so that malfunction does not easily occur.

In the infrared detector according to the present invention, a constant current circuit is connected in parallel between the output terminal of the current-voltage conversion amplifying means and the source of the N-channel field effect transistor and a power supply connected to the source. Since the current between the source and the drain when the gate of the N-channel field effect transistor is turned on is made constant irrespective of the size of the external load connected to the output pad, the human body detection signal output means can be a low current source. If the configuration is such that the amount of charge injected into the P-well region is limited, a change in the voltage of the drain of the N-channel field-effect transistor is less likely to be transmitted to the input protection unit serving as the input unit of the voltage amplification unit. Since it is difficult to provide feedback via the input unit, malfunction is unlikely to occur.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram schematically illustrating an example of a configuration of an infrared detector according to the present invention.

FIG. 2 is a diagram mainly showing a human body detection signal output unit as an example of an infrared detector according to the present invention. FIG. 2A is a circuit diagram of the human body detection signal output unit, and FIG. 4) is an explanatory diagram schematically illustrating the relationship between the human body detection signal output unit and the input protection unit of the voltage amplification unit.

FIG. 3 is a diagram showing an example in which a voltage limiting circuit is connected in parallel to a P-channel field effect transistor constituting a human body detection signal output means. FIG. 3 (a) is a block diagram and FIG.
(B) is a figure which illustrates a circuit diagram.

FIG. 4 shows an example in which a constant current circuit is connected in parallel between the output terminal of the current-voltage conversion amplifying means and the source of a P-channel field effect transistor constituting the human body detection signal output means and a power supply connected to the source. 4A is a diagram illustrating a block diagram, and FIG. 4B is a diagram illustrating a circuit diagram.

FIG. 5 is a circuit block diagram schematically showing another example of the configuration of the infrared detector according to the present invention. You.

FIG. 6 is a diagram mainly showing a human body detection signal output unit of another example of the infrared detector according to the present invention. FIG. 6 (a) is a circuit diagram of the human body detection signal output unit, and FIG. FIG. 4B is an explanatory diagram schematically illustrating the relationship between the human body detection signal output unit and the input protection unit of the voltage amplification unit.

7 is a diagram showing an example in which a voltage limiting circuit is connected in parallel to an N-channel field-effect transistor constituting a human body detection signal output means. FIG. 7A is a block diagram, and FIG.
(B) is a figure which illustrates a circuit diagram.

FIG. 8 shows a constant current circuit connected in parallel between the output terminal of the current-voltage conversion amplifying means and the source of an N-channel field effect transistor constituting the human body detection signal output means and a power supply connected to the source. FIG. 7A shows an example, and FIG.
Is a block diagram, and FIG. 7B is a diagram illustrating a circuit diagram.

FIG. 9 is a circuit block diagram schematically showing a configuration of a conventional infrared detector.

FIG. 10 is a circuit block diagram schematically showing an infrared detector in which a circuit configuration of a conventional infrared detector is directly formed into a one-chip IC.

FIG. 11 is an explanatory diagram schematically illustrating a problem that occurs in a semiconductor substrate when a circuit configuration of a conventional infrared detector is directly converted into a one-chip IC.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 2 Infrared detector 20 Current-voltage conversion means 30 Voltage amplification means 40 Comparison means 50 Human body detection signal output means 52 N-channel field effect transistor (NMOS) 53 P-channel field effect transistor (PMOS) 54 Output pad 70 P-type semiconductor substrate 70A N-type semiconductor substrate 71 N-well region 71A P-well region 81, 81A Voltage limiting circuit 83 Zener diode 90, 90A Constant current circuit

────────────────────────────────────────────────── ─── Continuing on the front page (51) Int.Cl. ⁶ Identification code FI H04N 5/33 H01L 27/14 K (72) Inventor Toshio Fujimura 1048 Kadoma, Oji, Kadoma, Osaka Matsushita Electric Works, Ltd.

Claims (6)

[Claims] 1. A pyroelectric element that outputs a current corresponding to the heat of a human body when the heat is detected, and a current-voltage converter that converts an output current output when the pyroelectric element detects the heat into a voltage. Means, voltage amplifying means for amplifying an output signal output from the current-to-voltage conversion means, comparison means for comparing a signal output from an output terminal of the voltage amplifying means with a predetermined threshold value, A human body detection signal output unit that outputs a detection signal that has detected a human body in response to a signal output from the unit.In the infrared detector, at least the current-voltage conversion unit and the human body detection signal output unit The human body detection signal output means is formed in the same P-type semiconductor substrate, and the human body detection signal output means is formed in an N-well region formed in the P-type semiconductor substrate, and a gate is connected to an output terminal of the comparison means. Scan is connected to the power supply, and,
An infrared detector comprising a P-channel field-effect transistor having a drain connected to an external load such as alarm issuing means. 2. The device according to claim 1, wherein a voltage limiting circuit for limiting a voltage output from a drain of said P-channel field-effect transistor is connected in parallel with said P-channel field-effect transistor. Infrared detector. 3. A constant current circuit is connected in parallel between an output terminal of said comparing means, a source of said P-channel field effect transistor and a power supply connected to said source. The infrared detector according to 1. 4. A pyroelectric element that outputs a current corresponding to the heat of a human body or the like, and a current-voltage converter that converts an output current output when the pyroelectric element detects the heat into a voltage. Means, voltage amplifying means for amplifying an output signal output from the current-to-voltage conversion means, comparison means for comparing a signal output from an output terminal of the voltage amplifying means with a predetermined threshold value, A human body detection signal output unit that outputs a detection signal that has detected a human body in response to a signal output from the unit.In the infrared detector, at least the current-voltage conversion unit and the human body detection signal output unit The human body detection signal output means is formed in the same N-type semiconductor substrate, and the human body detection signal output means is formed in a P-well region formed in the N-type semiconductor substrate, and a gate is connected to an output terminal of the comparison means. The source is connected to the ground,
And an N-channel field-effect transistor having a drain connected to an external load such as alarm issuing means. 5. The infrared detector according to claim 4, wherein a voltage limiting circuit for limiting a voltage output from the drain of the N-channel field-effect transistor is connected in parallel with the N-channel field-effect transistor. vessel. 6. A constant current circuit is connected in parallel between an output terminal of said comparing means, a source of said N-channel field effect transistor, and a power supply connected to said source. The infrared detector according to 1.