JPH09229763A - Flame sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To heighten the degree of allowability for dispersion in production and discrimination precision of on/off of a flame by matching temperature characteristics of dark current between a pair of semiconductor ultraviolet sensors and detecting the difference of output voltage or output current between the two sensors. SOLUTION: A pair of semiconductor ultraviolet ray sensors 1b , 1c in which the long wave length end of an absorbed wave length band is in the neighborhood of 280nm or 290nm are provided, and one 1c of them is shielded with a metal light shielding film 7. Load resistors R1 , R2 grounding one terminal are connected to electrodes 5a , 5b respectively, an electrode 5c is connected to a power source VDD. Output current I1 of the sensor 1b and output current I2 of the sensor 1c are allowed to flow, and output voltages V1 , V2 are output. When dark current is not equal, regulation can be performed so that the output voltages V1 , V2 may be equal in dark. Because the output currents I1 , I2 are also changed for temperature change, its change part appears in the output voltages V1 , V2 as the change of the equal output voltage, and the difference between the output voltages is constant for the temperature change. The difference between the output voltages is detected with an amplifier 9, and an ultraviolet ray of wave length of 280nm or less emitted from a flame can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flame sensor for recognizing a specific wavelength component of radiated light from a flame using a photoconductive semiconductor ultraviolet sensor. More specifically, the wavelength range of light, which is a noise source such as sunlight or room light, is excluded from the emission wavelength range of the flame, and is approximately 200 nm to 280.
The present invention relates to a flame sensor that detects ultraviolet rays having a wavelength component of nm.

[0002]

2. Description of the Related Art As a flame sensor, a thermocouple type which uses a thermocouple to convert the heat generated by the flame into electric energy to detect the flame, and a hydrogen flame ionization detector to detect hydrogen ions in the flame A hydrogen flame ionization detector type that converts energy into energy to detect a flame and a photoelectric tube type that converts light energy generated by a flame into electrical energy by using a photoelectric tube to detect a flame are generally used.

[0003]

In the thermocouple type flame sensor, the temperature around the sensor does not change rapidly even after the flame as a heat source is extinguished, so that the flame state changes at the time of ignition, extinguishing, etc. There is a drawback that the range of use is limited, such that the transient response to is poor and that there is a problem in use in a hermetically sealed case where temperature changes are scarce. In the hydrogen flame ionization detector type flame sensor, the electrode part needs to be provided in the flame, and in order to adapt to a wide range from a small flame to a large flame, not only the electrode part but also the support part, etc., have high heat resistance. Since reliability is required, it is difficult to adapt to a flame whose shape and size change greatly, and its use range is limited to use in a water heater, a small boiler, or the like. The photoelectric tube type flame sensor is superior to the thermocouple type or hydrogen flame ionization detector type flame sensor in the accuracy of determining the on / off state of the flame, and can be installed at a distance from the flame. However, due to the structural restrictions of the photoelectric tube, it is difficult to miniaturize the flame sensor and to drive it at a low voltage, and in addition, the photoelectric conversion efficiency (quantum efficiency) for converting light energy into electrical energy is There is a problem that it cannot be said to be low enough to detect weak light particularly in the wavelength range of 200 nm to 280 nm emitted from a flame. More specifically, as shown in FIG. 8, the wavelength range of light to be detected by the flame sensor is obtained by excluding the wavelength range of light that is a noise source such as sunlight or room light from the emission wavelength range of flame. It is approximately 200 nm to 280 nm. However, when a fluorescent lamp is a main noise source in a room where sunlight is completely shielded, the wavelength range of light to be detected by the flame sensor is approximately 200 nm to 290 nm. Further, the emission spectrum of the flame becomes weaker as the wavelength becomes shorter, and is particularly remarkable at 240 nm or less. The photoelectric conversion efficiency (quantum efficiency) of the photoelectric tube has a long residual sensitivity region on the long wavelength side. Therefore, in order to sufficiently suppress the residual sensitivity in the wavelength region of 280 nm or more, the maximum sensitivity region is 200 nm to 2 nm.
It exists in the wavelength range of 20 nm, the quantum efficiency is 20% to 30% even in the highest sensitivity range, and it has a drawback that it falls to 5% to 10% in the detection wavelength range of 240 nm to 280 nm, which is the most important as a flame sensor. If the quantum efficiency in the wavelength range of 240 nm to 280 nm, which is the most important as a flame sensor, is to be improved, the residual sensitivity in the wavelength range of 280 nm or more will increase, and the SN ratio will be increased due to false detection of sunlight or room light. There is a drawback that it deteriorates, and there is a problem in using the photoelectric tube as a highly accurate flame sensor. The present invention uses a photoconductive semiconductor ultraviolet sensor instead of a phototube to detect ultraviolet rays in the light emitted from a flame in the wavelength range of 200 nm to 290 nm, particularly 200 nm to 280 nm with high efficiency and high accuracy. It is an object. A photoconductive semiconductor UV sensor has a predetermined absorption spectrum by selecting an appropriate band gap between the valence band and the conduction band of the semiconductor and has a high photoelectric conversion efficiency (quantum efficiency). It is possible to obtain a semiconductor ultraviolet sensor having a short residual sensitivity region on the long wavelength side and a sharp rise in the absorption wavelength edge. However, even when the semiconductor ultraviolet sensor does not receive light in the absorption spectrum, in the dark, when a voltage is applied to the semiconductor ultraviolet sensor, a dark current flows, and fluctuations of the dark current with respect to temperature changes cause the light in the absorption spectrum to change. Since it is larger than the difference from the bright current when receiving light, in order to use the photoconductive semiconductor UV sensor as a flame sensor, it is necessary to compensate for variations in dark current due to temperature changes due to on / off of the flame. . Especially 200nm to 280nm emitted from flame
In order to realize a semiconductor ultraviolet sensor that detects weak light in the wavelength range of 1), highly accurate temperature compensation is required as compared with other photoconductive semiconductor photosensors that have an absorption spectrum in the long wavelength range. The present invention is made to solve the problems of the above-described conventional flame sensor and the problems that occur when a photoconductive semiconductor ultraviolet sensor is used as a flame sensor. Has a high degree of determination accuracy and a high degree of freedom with respect to sensor installation conditions,
It is an object to provide a flame sensor having a wide application range.

[0004]

[Means for Solving the Problems]

[Structure] The first characteristic structure of the flame sensor according to the present invention for achieving this object is, as described in claim 1 of the scope of the claims, that the long wavelength end of the absorption wavelength range is 280 nm.
A point is that a pair of semiconductor ultraviolet sensors near or at 290 nm is provided, and one of the pair of semiconductor ultraviolet sensors is shielded from light. The second characteristic configuration of the flame sensor according to the present invention is, as described in claim 2 of the claims, a pair of semiconductor ultraviolet sensors having a long wavelength end in the absorption wavelength region near 280 nm or 290 nm. An optical filter having a short wavelength end in a transmission wavelength range near a long wavelength end in an absorption wavelength range of the pair of semiconductor ultraviolet sensors is provided to emit light in a specific wavelength range to one of the pair of semiconductor ultraviolet sensors. The point is to block light. A third characteristic configuration of the flame sensor according to the present invention is, in addition to the above-mentioned first or second characteristic configuration, as described in claim 3 of the scope of claims, in addition to the pair of semiconductor ultraviolet sensors. It is provided with a differential amplifier that detects the difference between the output current and the output voltage. A fourth characteristic configuration of the flame sensor according to the present invention is, in addition to the above-mentioned first or second characteristic configuration, a pair of semiconductor ultraviolet sensors as described in claim 4 of the claims. A voltage is applied between open electrodes at both ends of the pair of semiconductor ultraviolet sensors connected in series, and an output voltage or an output current is output from an intermediate electrode connected to both of the pair of semiconductor ultraviolet sensors. The point is to take out. A fifth characteristic configuration of the flame sensor according to the present invention is, in addition to the above-described fourth characteristic configuration, as described in claim 5 of the appended claims, a pair of semiconductor ultraviolet rays connected in series. There are two sets of sensors, a differential amplifier for detecting the difference in output voltage or output current from the intermediate electrodes of each set is provided, and one set of open electrodes on the side of the semiconductor UV sensor not shielded from light and the other set The open electrodes on the side of the semiconductor UV sensor, which are shielded from light, are connected to each other. A sixth characteristic configuration of the flame sensor according to the present invention is, in addition to the above-mentioned first to fifth characteristic configurations, all of the semiconductor ultraviolet sensors are the same as described in claim 6 of the claims. It is formed on the substrate. The seventh characteristic configuration of the flame sensor according to the present invention is, in addition to the above-mentioned third or fifth characteristic configuration, all of the semiconductor ultraviolet sensors, and The differential amplifier is formed on the same substrate.

The operation will be described below. According to the first characteristic configuration, the temperature characteristics of the dark current are matched between the pair of semiconductor ultraviolet sensors, and the difference between the output voltage or the output current of both sensors is detected, so that the variation with respect to the temperature change is large. The dark current components are canceled out, and the unshielded one of the pair of semiconductor ultraviolet sensors can function as an ultraviolet sensor in a predetermined wavelength range, and the shielded one can function as a thermistor for temperature compensation. . As a result, highly accurate temperature compensation is possible, the flame on / off determination accuracy is high, and a flame sensor with a wide range of application can be easily configured.

According to the second characteristic configuration, the temperature characteristics and the absorption spectrum of the dark current are matched between the pair of semiconductor ultraviolet sensors, and the difference between the output voltage or the output current of both sensors is detected. The dark current component, which fluctuates drastically with respect to the temperature change, is canceled out, and further, in the semiconductor ultraviolet sensor which is shielded from light, the long wavelength end of the absorption wavelength range of the semiconductor ultraviolet sensor is an incomplete crystal or a condition during the manufacturing process. Even when the variation reaches the wavelength range of sunlight or room light due to variations, the increase in bright current due to the sunlight or room light can be offset as a noise component, and the pair of semiconductor ultraviolet sensors can block light. The non-shielded one can function as an ultraviolet ray sensor in a predetermined wavelength range, and the shielded one can function as a thermistor for temperature compensation and an element for compensating for disturbing light. Than it is. As a result, highly accurate temperature compensation and turbulent light compensation are possible, the tolerance for manufacturing variations and the accuracy of flame on / off determination are high, and a flame sensor with a wide range of application can be easily configured. .

According to the third characteristic configuration, the difference between the output current or the output voltage of the pair of semiconductor ultraviolet sensors is detected by the differential amplifier, whereby the fluctuation of the dark current or the bright current due to sunlight or room light is detected. Is canceled out, and only the increase / decrease of the bright current with respect to the change of the ultraviolet intensity within the predetermined absorption wavelength range can be detected as the difference. Therefore, a simple circuit configuration using a differential amplifier can be used to turn on / off the flame. It is possible to provide a highly accurate flame sensor that can perform the determination and the process for the temperature compensation or the turbulent light compensation at the same time.

According to the fourth characteristic configuration, the fluctuation of the dark current due to the temperature change and the fluctuation of the bright current due to the disturbing light act equally between the pair of semiconductor ultraviolet sensors connected in series.
When the intensity of ultraviolet rays within a predetermined absorption wavelength range is constant, the resistance ratio between the two semiconductor ultraviolet sensors is always constant regardless of temperature change or the presence or absence of disturbing light. When there is no output current, the output voltage from the intermediate electrode is a resistance division of the input voltage applied to the open electrodes at both ends of a pair of semiconductor ultraviolet sensors connected in series. It becomes constant and follows only changes in the ultraviolet intensity within a predetermined absorption wavelength range. As a result, the process for the temperature compensation or the disturbance light compensation is automatically performed, and only the change amount of the bright current with respect to the change of the ultraviolet intensity within the predetermined absorption wavelength range is the output current when the output voltage is constant. If the output current is constant, it can be detected as a change in the output voltage.
With a simple circuit configuration in which a pair of semiconductor ultraviolet sensors are connected in series, it is possible to configure a flame sensor with high accuracy of flame on / off determination.

According to the fifth characteristic configuration, the output voltage or the output current at each intermediate electrode of the two pairs of semiconductor ultraviolet sensors connected in series is changed with respect to the change of the ultraviolet intensity within the predetermined absorption wavelength range. Since each change in the opposite direction, the change in the output voltage or output current with respect to the change in the UV intensity is doubled, making it easier to improve the light receiving sensitivity of the flame sensor. As a result of differentially amplifying a pair of output voltage or output current that changes with time, noise components due to fluctuations in power supply voltage, etc. are also canceled at the same time, which is highly tolerant of fluctuations in operating conditions and the accuracy of flame on / off determination It is possible to construct a very high flame sensor with a simple circuit configuration using a differential amplifier.

According to the sixth characteristic configuration, variations in absorption spectrum due to temperature characteristics of dark current, imperfections of crystals, and variations in conditions during the manufacturing process can be easily matched between the pair of semiconductor ultraviolet sensors. Therefore, it is possible to perform highly accurate temperature compensation and turbulent light compensation, and it is possible to easily configure a flame sensor that has high tolerance for manufacturing variations and high flame on / off determination accuracy.

According to the seventh characteristic configuration, since the components necessary for the flame sensor having the temperature compensation function and the disturbance light compensation function can be integrated on one chip, the number of parts constituting the flame sensor can be reduced and the flame can be reduced. The size of the sensor can be greatly reduced.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, an Al _x Ga _{1 -x} N photoconductor 1a, which is an example of a pair of semiconductor ultraviolet sensors 1 having a long wavelength end in the absorption wavelength region near 280 nm, is a physical vapor deposition method such as laser heating. Are formed on the sapphire substrate 2a, which is an example of the same substrate 2. If the composition ratio x of Al and Ga is selected in the range of 0.33 to 0.35, the band gap Eg is about 4.5 eV.
Therefore, the long wavelength end of the absorption spectrum of the Al _x Ga _1-x N photoconductor 1a is hν / Eg = 1240 / Eg (n
Since it is given by m), the long wavelength end of the absorption spectrum is approximately 275 nm. However, h is Planck's constant,
ν is the frequency of light. Further, n is formed on the Al _x Ga _{1 -x} N photoconductor 1a layer to form at least three electrodes necessary for constructing a pair of ultraviolet sensors.
The lower electrode 3 of the type GaN layer and the metal electrode 4 such as TiAl are vapor-deposited, and three electrodes 5a, 5b and 5c having a comb pattern as shown in FIG. 2 are formed through an exposure etching process. The lower electrode 3 of the pair of n-type GaN layers and the metal electrode 4 constitute the electrode 5a, 5b, or 5c. The metal of the metal electrode 4 is thermally diffused into the n-type GaN layer, and the metal electrode 4 and the lower electrode 3 of the n-type GaN layer are in pseudo ohmic contact. Furthermore, the metal electrode 4 and Al _x Ga
_{On the 1-x} N photoconductor 1a layer, for example, SiO ₂ or Al ₂ O ₃ which transmits at least a wavelength of 280 nm or shorter is transmitted.
The insulating protection film 6 is formed by vapor deposition, and an opening window for bonding the conductive wire to the metal electrode 4 is formed through an exposure etching process. A metal light-shielding film 7 is vapor-deposited and formed on the insulating protective film 6 so as to shield the light-receiving portion for only one of the pair of semiconductor ultraviolet sensors 1. As shown in FIGS. 1 and 2, the two electrodes 5a and 5c, the lower regions of the two electrodes 5a and 5c, and the two electrodes 5a and 5c.
The semiconductor ultraviolet sensor 1b that functions as one element is configured by the Al _x Ga _{1 -x} N photoconductor 1a layer in the region sandwiched by c. The region sandwiched between the two electrodes 5a and 5c is the light receiving unit 10. Also, the two electrodes 5b and 5c, the lower regions of the two electrodes 5b and 5c, and the two electrodes 5b,
The Al _x Ga _{1 -x} N photoconductor 1a layer in the region sandwiched by 5c constitutes the semiconductor ultraviolet sensor 1c for temperature compensation.
The pair of semiconductor ultraviolet sensors 1b and 1c are formed to have the same cross-sectional shape and planar shape except for the metal light shielding film 7. However, with respect to the planar shape, it may be desirable to take the matching of the directivity in consideration of the incident angle of the incident light.

FIG. 3 is an equivalent circuit diagram of the pair of semiconductor ultraviolet sensors shown in FIGS. 4 to 7 show circuit configurations of the flame sensor according to the present invention expanded from the equivalent circuit shown in FIG. In each of the drawings shown in FIGS. 4 to 7, temperature compensation is automatically performed, and the ultraviolet rays emitted from the flame are detected as an electric signal. As shown in FIG. 4, load resistors R1 and R2 with one terminal grounded
Are connected to the electrodes 5a and 5b of the pair of semiconductor ultraviolet sensors, respectively, and the electrode 5c is connected to the power supply V _DD . Output current I ₂ of the output current I _1, and the other semiconductor ultraviolet sensor 1c of the semiconductor UV sensor 1b each into the load resistors R1, R2, electrodes 5a, output 5b voltage V _1, V ₂ are output. Although the resistance value of the load resistor R2 is set to be equal to the resistance value of R1 in principle, a pair of semiconductor ultraviolet sensors 1b,
When the dark currents are not equal, such as when 1c is made from another chip, the output voltages V ₁ and V ₂ can be adjusted to be equal in the dark. Since the output currents I ₁ and I _{2 also} change in response to temperature changes, the change in the output current is equal to the change in the output voltage V ₁ ,
Will appear at the V _2, the difference between the output voltage becomes constant with respect to temperature changes. By detecting the difference in the output voltage with the differential amplifier 9, it is possible to detect the ultraviolet rays having a wavelength of 280 nm or less emitted by the flame.

As shown in FIG. 5, the electrode 5a is connected to the power source V _DD , the electrode 5b is grounded, and the semiconductor ultraviolet sensor 1b,
1c is used in a state of being connected in series. From electrode 5c,
An output voltage V ₃ obtained by resistance-dividing the power supply voltage V _DD by each resistance component of the two semiconductor ultraviolet sensors 1b and 1c is taken out. Since the semiconductor ultraviolet sensors 1b and 1c have the same conductivity in the dark, the same output currents I ₁ and I ₂ are obtained, and the output voltage V ₃ becomes half the power supply voltage V _DD . The R1 side of the series-connected resistors R1 and R2 is connected to the power supply V _DD , the R2 side is grounded, and the reference voltage V _ref is taken out from the midpoint. In principle, the resistance value of the resistor R2 is set equal to the resistance value of R1, the reference voltage V _ref is half the power supply voltage V _DD , and the output voltage V ₃ and the reference voltage V _ref are the same potential in the dark. Ammeter 1 provided between the midpoint and the electrode 5c
No current flows through 1. The semiconductor ultraviolet sensor 1b,
When the dark currents are not equal, such as when 1c is made from another chip, the output voltage V ₃ in the dark is the power supply voltage V _3.
Although it is displaced from the half value of _DD , it is possible to adjust the reference voltage V _ref to be equal to the output voltage V ₃ in the dark by adjusting the resistance value of the resistor R2. The output current I ₁ ,
Since I ₂ also changes with temperature, the output voltage V ₃ maintains a constant value. 280n radiating flame
Semiconductor ultraviolet sensor 1 for ultraviolet rays with wavelengths of m or less
Only b is sensitive and the output voltage V ₃ changes in the direction of increasing both the output currents I ₁ and I ₂ . As a result, a potential difference is generated between the midpoint and the electrode 5c, a current flows through the ammeter 11, and it operates as a flame sensor that is sensitive only to ultraviolet rays of a wavelength of 280 nm or less emitted by the flame regardless of temperature conditions.

As shown in FIG. 6, the ammeter 11 shown in FIG.
Instead of detecting the presence / absence of a current by using to determine whether the flame is on or off, the output voltage V ₃ and the reference voltage V
It is also a preferred embodiment that the difference in _ref is detected by the differential amplifier 9. In this case, since the variation range of the input voltage of the differential amplifier 9 does not vary with temperature changes, the design of the differential amplifier 9 is easier than the circuit configuration shown in FIG.

As shown in FIG. 7, it is also a preferred embodiment to replace the series-connected resistors R1 and R2 shown in FIG. 6 with another pair of series-connected semiconductor ultraviolet sensors 1c and 1b. In this circuit configuration, similarly to the circuit configurations shown in FIGS. 5 and 6, the output voltages V _3A and V _3B of the pair of semiconductor ultraviolet sensors of each set are half the power supply voltage V _{DD in} the dark regardless of temperature conditions. 280n of flame radiation
The output voltage V _3A rises with respect to ultraviolet rays having a wavelength of m or less,
The output voltage V _3B decreases. The fluctuation range of the output voltages V _3A and V _3B is the same as that of the output voltage V ₃ shown in FIG.
The difference voltage between the output voltages V _3A and V _3B , which is the input voltage of
Since the circuit configuration is doubled and the median value of the input voltage is always constant, the differential amplifier 9 can be designed more easily and the detection sensitivity is high.

As shown in FIG. 9, when the absorption spectrum 14 of the pair of semiconductor ultraviolet sensors 1 has residual sensitivity on the longer wavelength side than 280 nm, instead of providing the metal light-shielding film 7 shown in FIG. In a preferred embodiment, an ultraviolet ray transmitting filter 8a that transmits ultraviolet rays having a wavelength longer than 280 nm is provided on the insulating protective film 6 for one of the pair of semiconductor ultraviolet ray sensors 1 so as to shield the light receiving portion. is there. Examples of the ultraviolet transmission filter 8a that transmits ultraviolet rays having a wavelength longer than 280 nm include ultraviolet transmission filters UV28, UV30, manufactured by Hoya Corporation.
UV32, color compensating filters CC500, CL500, heat absorption filters HA50, HA30, ultraviolet transmission visible light absorption filters U360, U350, U340 and the like are mentioned as candidates, but preferably, as shown in the transmission spectrum 13 shown in FIG. An ideal filter is one that has a characteristic that the transmittance rises sharply. Specifically, the ultraviolet light transmitting filter 8a is adhered to the region where the metal light shielding film 7 shown in FIG. 2 is provided, or the pair of semiconductor ultraviolet light sensors 1 are formed of different chips and are individually assembled in different packages. In this case, the metal light-shielding film 7 is not provided and the ultraviolet transmission filter 8a is used for the light receiving window of one package. Further, the insulating protective film 6 is made of SiO ₂ or Al ₂ O.
_In the case of a glass-based material such as ₃ , if an insulating protective film having a composition close to the composition of the above-mentioned ultraviolet transmission filter 8a is formed only on the region that covers one light receiving portion of the pair of semiconductor ultraviolet sensors 1, the ultraviolet transmission filter It is possible to save the trouble of adhering 8a and improve the manufacturing efficiency.

As shown in FIG. 9, a semiconductor ultraviolet sensor 1
The product of the absorption spectrum 14 and the transmission spectrum 13 of the ultraviolet transmission filter 8a is the effective absorption spectrum 15 of the semiconductor ultraviolet sensor 1c shielded by the ultraviolet transmission filter 8a. Since the dark current is the thermal equilibrium current of the semiconductor ultraviolet sensor 1, its temperature compensation is as shown in FIGS. 4 to 7 regardless of whether the semiconductor ultraviolet sensor 1c is shielded by the metal light shielding film 7 or the ultraviolet transmission filter 8a. In the embodiment of the circuit configuration shown, the effects are exactly equivalent. When using the ultraviolet transmission filter 8a having the transmission spectrum 13 shown in FIG.
Even if turbulent light with a wavelength longer than 0 nm is incident on the flame sensor, both semiconductor ultraviolet sensors 1b and 1c output a bright current according to the absorption spectra 14 and 15. In the case of the ideal characteristic that the transmission spectrum 13 rises vertically from 280 nm, the absorption spectra 14 and 15 are 2
Since the semiconductor ultraviolet ray sensors 1b and 1c have the same output current in the wavelength region longer than 80 nm, the difference between the output voltages V ₁ and V ₂ shown in FIG. 4, the output voltage V ₃ shown in FIG. 5 or 6, The output voltages V _3A and V _3B shown in FIG. 7 do not change, and the noise component due to the disturbing light such as sunlight can be removed.
However, as shown in FIG. 9, the transmission spectrum 1
When 3 is steeper than 280 nm but gradually rises, the absorption spectra 14 and 15 have a difference in a wavelength range longer than 280 nm, and as a result, the semiconductor ultraviolet sensor 1
Although the output currents and the output voltages of b and 1c are different from each other, the residual noise component due to the disturbing light such as sunlight cannot be completely removed, but the residual noise component is greater than that when the metal light shielding film 7 shields the light. Can be suppressed and the noise signal ratio can be improved. As described above, even when the absorption spectrum 14 of the pair of semiconductor ultraviolet sensors 1 has residual sensitivity on the longer wavelength side than 280 nm, the ultraviolet transmission filter 8a that transmits the ultraviolet ray on the longer wavelength side than 280 nm is used. Thus, the embodiments shown in FIGS. 4 to 7 can be applied as they are.

(Another Embodiment) Another embodiment will be described below. As a pair of semiconductor ultraviolet sensors 1 in which the long wavelength end of the absorption wavelength region is near 280 nm, Al _x Ga _1-x
Mg having similar bandgap other than N photoconductor
You may use S, CaS, SrS etc. Also Al _x G
Since the relationship between the composition ratio x of Al and Ga of the a _1-x N photoconductor and the band gap changes in relation to the impurity concentration and the like, the composition ratio x is not necessarily limited to the range of 0.33 to 0.35. It is not something that will be done. The planar shapes of the electrodes and the light receiving portions shown in FIG. 2 are not particularly limited to the comb pattern. Also, by changing the direction and combining the same comb-shaped pattern,
It is also expected that the incident angle dependence of the light receiving sensitivity will be relaxed. The circuit configuration of the differential amplifier shown in FIG. 4, FIG. 6 or FIG. 7 is not particularly described in detail, but since the semiconductor ultraviolet sensor has a limited current driving capability, it is generally regarded as an independent semiconductor ultraviolet sensor. It is desirable to use the high input impedance differential amplifier used, and if it is constructed on the same substrate as the semiconductor UV sensor, MOSF
The use of a differential amplifier with ET input is desirable. Instead of the sapphire substrate shown in FIG. 1, a hexagonal SiC substrate or a high resistivity Si substrate may be used. When a Si substrate having a high resistivity is used, an n-type or p-type impurity diffusion region is selectively formed by thermal diffusion or ion implantation in a portion different from a region where a semiconductor ultraviolet sensor is formed, for example, a MOSFET. And the like, a high input impedance differential amplifier can be provided on the same substrate as the semiconductor ultraviolet sensor, and a small flame sensor can be configured with one chip. The long-wavelength end of the absorption wavelength range of the pair of semiconductor ultraviolet sensors 1 in the above-described embodiment is preferably near 280 nm from the emission spectrum of sunlight or room light that becomes disturbing light, but is not necessarily limited to near 280 nm. It is not necessary, for example, when a fluorescent lamp is the main noise source in a room where sunlight is completely shielded, the long wavelength end of the absorption wavelength range of the pair of semiconductor ultraviolet sensors 1 is 290n.
It may be near m. Furthermore, at least 200 nm to 280 is applied to one of the pair of semiconductor ultraviolet sensors 1.
If the ultraviolet rays of nm are shielded, the sensitivity of the compensating circuit for the disturbing light is improved, or an optical filter for shielding the disturbing light wavelength range is provided for both of the pair of semiconductor ultraviolet sensors 1. Therefore, it is possible to obtain the same effects as the temperature compensation and the disturbance light compensation in the above-described embodiment.

[0020]

As described above, according to the present invention,
High-accuracy temperature compensation and turbulent light compensation for semiconductor ultraviolet sensor is possible, tolerance to manufacturing variations and high accuracy of flame on / off determination, and simple flame sensor using semiconductor ultraviolet sensor with wide application range Can be supplied to.

It should be noted that reference numerals are added to the claims for convenience of comparison with the drawings, but the present invention is not limited to the constitution of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a pair of semiconductor ultraviolet sensors formed on the same substrate.

FIG. 2 is a plan view of a pair of semiconductor ultraviolet sensors formed on the same substrate.

FIG. 3 is an equivalent circuit diagram of a pair of semiconductor ultraviolet sensors.

FIG. 4 is a circuit configuration diagram of a flame sensor.

FIG. 5 is a circuit configuration diagram of a flame sensor.

FIG. 6 is a circuit diagram of a flame sensor.

FIG. 7 is a circuit configuration diagram of a flame sensor.

FIG. 8: Emission spectrum diagram of flame, sunlight, room light, and absorption spectrum diagram of phototube

FIG. 9: Emission spectrum diagram of flame, sunlight, room light, and absorption spectrum diagram of semiconductor ultraviolet sensor

[Explanation of symbols]

 1 Semiconductor Ultraviolet Sensor 2 Substrate 3 Lower Electrode 4 Metal Electrode 5a Open Electrode 5b Open Electrode 5c Intermediate Electrode 6 Insulation Protective Film 7 Metal Light Shielding Film 8 Optical Filter 8a Ultraviolet Transmission Filter 9 Differential Amplifier 10 Light Receiving Section 11 Ammeter 12 Incident Light

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display location H01L 31/10 H01L 31/10 A

Claims (8)

[Claims] 1. A flame sensor comprising a pair of semiconductor ultraviolet sensors (1) having a long wavelength end in the absorption wavelength range near 280 nm or 290 nm, wherein the pair of semiconductor ultraviolet sensors (1) comprises: A flame sensor with one side shielded from light. 2. A flame sensor comprising a pair of semiconductor ultraviolet sensors (1) having a long wavelength end in the absorption wavelength region in the vicinity of 280 nm or 290 nm, wherein the pair of semiconductor ultraviolet sensors (1) comprises: On the other hand, a flame sensor provided with an optical filter (8) having a short wavelength end of a transmission wavelength region near a long wavelength end of an absorption wavelength region of the pair of semiconductor ultraviolet sensors (1). 3. The flame sensor according to claim 1, further comprising a differential amplifier (9) for detecting a difference between output currents or output voltages of the pair of semiconductor ultraviolet sensors (1). 4. The pair of semiconductor ultraviolet sensors (1) are connected in series, and the open electrodes (5a, 5b) at both ends of the pair of semiconductor ultraviolet sensors (1) connected in series.
The flame sensor according to claim 1, wherein an output voltage or an output current is taken out from an intermediate electrode (5c) connected to both of the pair of semiconductor ultraviolet sensors (1) by applying a voltage therebetween. 5. A pair of semiconductor ultraviolet sensors (1) connected in series according to claim 4 are provided in two sets, and a difference in output voltage or output current from the intermediate electrode (5c) of each set is calculated. A differential amplifier (9) for detection is provided, and one set of open electrodes (5a) on the side of the semiconductor UV sensor which is not shielded from light and another set of open electrodes (5b) on the side of the semiconductor UV sensor which are shielded from light are connected to each other. A flame sensor connected to each. 6. The semiconductor ultraviolet sensor (1) is formed on the same substrate (2) all of the semiconductor ultraviolet sensor (1), 1, 2, 3,
The flame sensor according to 4 or 5. 7. All of the semiconductor ultraviolet sensors (1),
The flame sensor according to claim 3 or 5, wherein the differential amplifier (9) is formed on the same substrate (2). 8. A flame sensor comprising a pair of semiconductor ultraviolet sensors (1), wherein one of the pair of semiconductor ultraviolet sensors (1) is shielded from light, and a long wavelength end of the shielded wavelength range. A flame sensor having a wavelength of around 280 nm or around 290 nm.