JP2001044815A - Illuminance sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an illuminance sensor that does not respond to changes in an external light due to an illumination light, but will immediately respond to the change in a natural light. SOLUTION: This illuminance sensor uses a solar battery SB to detect the lightness of external light and makes a variable impedance element VI conductive, when the external light is a prescribed value or over. A liquid crystal panel LC, whose transmittivity is adjusted by an external signal, is placed to an incident path of the external light to the solar battery SB. The transmittivity of the liquid crystal panel is controlled smaller, when the variable impedance element VI is conductive such that when the variable impedance element VI is not conductive. Furthermore, the transmittivity of the liquid crystal panel LC differs between the visible light region and infrared ray region. Thus, a hysteresis characteristic with respect to the illumination light and that with respect to natural light are made different. Then the illuminance sensor has the hysteresis characteristic, that does not respond to the illumination light or light of head light at night, even when the light is received as the external light but that immediately responds to a sun light at daybreak.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an illuminance sensor for generating an output according to the brightness of external light.

[0002]

2. Description of the Related Art Conventionally, there has been provided an automatic blinker which detects the brightness of external light and turns on an illumination load when the brightness becomes equal to or less than a specified value. As described in Japanese Patent Application Laid-Open No. 5-152924, for example, this type of automatic flasher is configured using a photovoltaic element such as a photodiode array and a variable impedance element formed of a depletion-type MOSFET. Something was done. That is, the surrounding light amount is detected by the photovoltaic element, and the variable impedance element is turned on when the output voltage of the photovoltaic element becomes equal to or less than a specified value.

The automatic blinker described in the above publication employs a configuration in which a capacitor is connected in parallel with a photovoltaic element, and the output voltage of the photovoltaic element changes instantaneously due to a momentary change in external light. Even if the operation of the variable impedance element is not affected, malfunction is prevented.

[0004]

However, according to the technology described in the above publication, while the lighting load is turned on when the surroundings are dark, such as at night, external light from a headlight of an automobile running in the vicinity is illuminated. If the light enters the photovoltaic element, the output voltage of the photovoltaic element increases for a relatively long time, and a malfunction may occur in which the variable impedance element becomes non-conductive because the capacitor cannot cope.

To solve this problem, it is conceivable to increase the capacitance of the capacitor. However, when the capacitance of the capacitor increases, the time from when the amount of light incident on the photovoltaic element changes to when the variable impedance element responds is considered. Becomes longer, the lighting load is turned on with a delay after the amount of external light (that is, brightness) is reduced, and the lighting load is turned off with a delay after the increase in the amount of external light, which causes a sense of incongruity. .

The present invention has been made in view of the above circumstances, and an object of the present invention is to prevent a response from a change in external light due to a headlight of an automobile or the like, but to sufficiently change the amount of external light. It is an object of the present invention to provide an illuminance sensor capable of changing an output without sometimes causing a time delay.

[0007]

According to a first aspect of the present invention, there is provided a photovoltaic element for generating a voltage corresponding to the brightness of external light, and a passing impedance is controlled in accordance with an output voltage of the photovoltaic element. A variable impedance element, and a light amount adjusting member disposed on at least a part of an incident path of external light to a light receiving surface of the photovoltaic element and having a transmittance controlled by an external signal corresponding to a passing impedance of the variable impedance element. Is provided. According to this configuration, the light amount adjusting member whose transmittance is controlled by an external signal corresponding to the passing impedance of the variable impedance element that changes according to the brightness of the external light is provided on the incident path of the external light to the photovoltaic element. Because of the arrangement, it is possible to add hysteresis to the relationship between the brightness of external light and the passing impedance of the variable impedance element. In other words, by providing an external signal so as to reduce the transmittance of the light amount adjusting member when the external light decreases, the sensitivity can be reduced when the amount of external light is small. Settings can be made so that malfunction does not occur even when light enters. Further, since there is no need to provide a delay element between the solar cell and the variable impedance element, when the change in the amount of external light is sufficiently large, the transmittance of the light amount adjusting member can be immediately increased without a time delay. it can.

According to a second aspect of the present invention, in the first aspect of the present invention, an external signal for controlling the light amount adjusting member is transmitted when the amount of light incident on the photovoltaic element becomes a specified value or less. Is set to decrease. According to this configuration, the sensitivity is reduced when the amount of external light is less than or equal to a specified value. It is possible to set not to respond.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the light amount adjusting member is a transmissive liquid crystal plate whose transmittance is changed according to the strength of an electric field applied to the liquid crystal. It is. According to this configuration, a liquid crystal plate is used as the light amount adjusting member, and the liquid crystal plate is driven by an electric field and has a very large impedance, so that the power consumption is small. That is, the variable impedance element is driven by the electromotive force of the photovoltaic element, and the power required for the external signal for controlling the light amount adjusting member is small, so that the operation can be performed with very small power.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the liquid crystal plate controls a transmittance of a part of an incident path of external light to the photovoltaic element. According to this configuration, the amount of incident light is controlled only by a part of the incident path of the external light to the photovoltaic element. Can be reduced, and this also makes it possible to adjust the hysteresis characteristics.

According to a fifth aspect of the present invention, in the third or fourth aspect of the present invention, a polarizing plate is disposed on each of the front and back sides of the liquid crystal plate, and the transmittance of the polarizing plate and the liquid crystal plate passes through each polarizing plate. Are set based on the relative angle of the vibration surface of. According to this configuration, the transmittance is adjusted according to the positional relationship of the vibrating surface of the light passing through the polarizing plate, so that the overall amount of light incident on the photovoltaic element can be adjusted.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the polarizing plate is provided in a part of a path of external light incident on the photovoltaic element. According to this configuration, since the amount of incident light is adjusted only in a part of the incident path of the external light to the photovoltaic element, the change in the amount of light due to the polarizing plate is compared with the case where the incident light amount of the entire incident path is adjusted. The width can be reduced.

According to a seventh aspect of the present invention, in the third aspect, the photovoltaic element is a single crystal solar cell and has sensitivity in a wavelength range extending between a visible light region and a near infrared light region, The liquid crystal plate has different transmittance characteristics between a visible light region and an infrared light region. According to this configuration, by combining the spectral sensitivity characteristic of the photovoltaic element and the transmittance characteristic of the liquid crystal plate, it is possible to increase the hysteresis for the illumination light and decrease the hysteresis for the natural light. In other words, it is possible to provide a hysteresis characteristic that does not respond even if illumination light or light from a headlight is incident as external light at night, and immediately responds if sunlight enters with dawn.

According to an eighth aspect of the present invention, in the seventh aspect of the present invention, the solar cell having a maximum sensitivity in an infrared light region is used as the solar cell. According to this configuration, by combining the spectral sensitivity characteristic of the photovoltaic element and the transmittance characteristic of the liquid crystal plate, it is possible to increase the hysteresis for the illumination light and decrease the hysteresis for the natural light.

According to a ninth aspect of the present invention, in the first aspect of the present invention, a filter having different transmittances in a visible light region and an infrared light region is added to an incident path of external light to a light receiving surface of the photovoltaic element. It was done. According to this configuration, the amount of light incident on the photovoltaic element can be adjusted according to the wavelength of light, and a desired hysteresis characteristic can be obtained.

According to a tenth aspect of the present invention, in the first aspect, the variable impedance element is made of a MOSFET and an output voltage of the photovoltaic element is applied to a gate and a source. According to this configuration, since the variable impedance element is driven by voltage, a large output current is not required as a photovoltaic element, and as a result, the size can be reduced.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An example in which an illuminance sensor of the present invention is used in combination with a switch element to form an automatic blinker will be described below. The illuminance sensor A shown in FIG. 1 is housed in one package and is formed so as to be handled as one part when assembling an automatic blinker, as described later. That is, an automatic blinker is configured by adding components such as a three-terminal bidirectional thyristor (hereinafter, referred to as a triac) Q as a switch element to the illuminance sensor A.

The illuminance sensor A uses a solar cell SB as a photovoltaic element that generates an output voltage according to the amount of ambient light. The solar cell SB includes a plurality of cells connected in series, and each cell is arranged in a matrix on one plane of one substrate.

A resistor R and a capacitor C are connected in parallel to the solar cell SB, and the positive electrode of the solar cell SB is connected to a control terminal of the variable impedance element VI. A high resistance is used for the resistor R. The variable impedance element VI has two depletion-type (normally-on) MOSFETs Q
1 and Q2 are connected in reverse series, the sources and the gates are commonly connected, the gate is connected as a control terminal to the positive electrode of the solar cell SB, and the source is connected to the negative electrode of the solar cell SB. . MOSFET Q1,
Q2 is connected in reverse series because MOSFET Q
This is to prevent the current flowing through the body diode when the MOSFETs 1 and Q2 are not conducting, and to make the resistance substantially constant regardless of the direction of the current when the MOSFETs Q1 and Q2 are conducting.

On the light receiving surface of the solar cell SB, a liquid crystal plate LC is disposed so as to overlap. As shown in FIG.
It has a configuration in which a liquid crystal is sandwiched between two transparent electrode glass substrates GB, and a polarizing plate PL is laminated on each of the front and back surfaces of a liquid crystal plate LC. With this configuration, the transmittance can be changed according to the voltage applied between the transparent electrodes provided on both glass substrates GB. A part of one glass substrate GB is extended more than the other glass substrate GB, and an electrode PE made of a transparent electrode (ITO film) is formed on the extended part.

The above-described solar cell SB, liquid crystal plate LC (polarizing plate PL), resistor R, capacitor C, and variable impedance element VI are housed in one package, thereby forming an illuminance sensor A. That is, as shown in FIGS. 2 and 3, these components are housed in a box-shaped package 10 made of synthetic resin having one open side. The package 10 includes components (a solar cell S) that constitute the illuminance sensor A.
B, resistor R, capacitor C, MOSFET Q1, Q2,
It is molded simultaneously and integrally with the metal frame 11 on which the liquid crystal plate LC) is mounted. Part of frame 11 is package 1
0, four terminal strips 12 are arranged in a row.
Two of the four terminal strips 12 are connected to both ends of the variable impedance element VI, and the other two are connected to both ends of the liquid crystal panel LC. It should be noted that wire bonding (not shown) is appropriately employed for connection between the frame 11 and the components. Inside the package 10, the MOSFETs Q1 and Q2 are sealed with an opaque resin 13, and the solar cell SB is sealed with a transparent resin 14.

By the way, in this embodiment, as described above, an automatic blinker is configured by externally attaching a triac Q or the like to the illuminance sensor A. The automatic blinker shown in FIG. 1 is of a two-terminal type, and a triac Q is connected in series to a series circuit of an AC power supply AC such as a commercial power supply and a load L such as a lighting load. That is, the power supply path from the AC power supply AC to the load L is turned on / off by the triac Q. ON / OFF of the triac Q is controlled by the illuminance sensor A described above. In other words, TRIAC Q
Of the variable impedance element VI (the drain of the MOSFET Q1) to the T2 terminal of the
The other end of the variable impedance element VI (MOSFET Q2
Are connected to the gate of the triac Q. A surge absorber ZNR is connected between the T1 terminal and the T2 terminal of the triac Q.

Further, the T1 terminal of the triac Q and the T2 terminal
A series circuit of resistors R2 and R3 is connected between the terminals,
A liquid crystal plate LC provided on the illuminance sensor A is connected in parallel to one resistor R3. That is, the voltage applied to the liquid crystal plate LC is a voltage obtained by dividing the voltage between both ends of the triac Q by the resistors R2 and R3. The liquid crystal plate LC used here is configured so that the transmittance decreases as the applied voltage decreases. Therefore, the transmittance is lower when the triac Q is on than when it is off. Here, since the liquid crystal plate LC is an element driven by a voltage, the power consumption is very small and the current passing through the load L is hardly affected.

As described above, the liquid crystal plate LC is a solar cell S
Since it is superposed on the light receiving surface of B, the amount of light incident on the solar cell SB also changes due to a change in the transmittance of the liquid crystal plate LC. In addition, since the amount of light incident on the solar cell SB decreases, the variable impedance element VI becomes conductive, and the triac Q
Is turned on, the transmittance of the liquid crystal plate LC is lowered, and conversely, when the amount of incident light on the solar cell SB increases, the variable impedance element VI becomes non-conductive and the triac Q is turned off. Since the transmittance of the liquid crystal panel LC is increased, the triac Q against external light is increased by the liquid crystal panel LC.
Means that a hysteresis characteristic is imparted to the on / off state.
In other words, when the triac Q is turned on, it is kept on and hardly turned off, and conversely, when the triac Q is turned off, it is kept off and hardly turned on. Here, the ratio of the light amount when the triac Q changes from off to on to the light amount when the triac Q changes from on to off is defined as a hysteresis magnification (= light amount (off → on) / light amount (on → off)). I will call it.
If the amount of light when the triac Q changes from off to on is constant, the higher the hysteresis magnification is, the smaller the amount of light from the triac Q changes from on to off. Will be higher.

As a result, when the triac Q is turned on at night and the lighting load, which is the load L, is turned on, the light from the lighting load or the headlights of the car is irradiated. Since the transmittance is reduced, the ON state of the triac Q is maintained. Since the capacitor C is connected in parallel with the solar cell SB, the capacitor C is charged even when light from a headlight or the like is irradiated when the triac Q is turned on at night, so that the voltage across the solar cell SB rises. During this time, the variable impedance element VI can be kept in a non-conductive state, and a malfunction such that the triac Q is immediately turned off can be avoided.

Here, the combination of the spectral characteristic of the transmittance of the liquid crystal plate LC and the spectral sensitivity characteristic of the solar cell SB will be specifically described. FIG. 5A shows the spectral characteristics of the transmittance of the liquid crystal plate LC and the spectral sensitivity characteristics of the solar cell SB.
It is set as shown in FIG. FIG. 5A shows the transmittance of the liquid crystal panel LC when the triac Q is off, and shows the transmittance of the liquid crystal panel LC when the triac Q is on.

That is, FIG. 5 shows the transmittance of the liquid crystal plate LC.
(A), the visible light region has a lower transmittance than the infrared light region, and when the transmittance is changed by changing the applied voltage, the light is transmitted in the visible light region. It is configured such that the change in the transmittance is greater than the change in the transmittance in the near infrared light region. That is, the transmittance of the liquid crystal plate LC is substantially constant in the infrared light region having a wavelength of 900 nm or more regardless of the on / off state of the triac Q, and the transmittance characteristics are set so that the transmittance changes significantly in the visible light region. I have. This is because the amount of light in the visible light region of a fluorescent lamp or an HID lamp generally used for illumination is considerably larger than that of the near-infrared light region. In order to reduce the change in the transmittance of the liquid crystal panel LC for natural light and to increase the change in the transmittance of the liquid crystal panel LC for illuminating light, utilizing the fact that many light and infrared light regions are included. It is.

On the other hand, the solar cell SB has a spectral sensitivity characteristic shown in FIG. 5B, is sensitive to light having a wavelength of 400 to 1200 nm (from the visible light region to the infrared light region), and is 950 nm. The maximum sensitivity is obtained for light having a wavelength in the vicinity (near infrared light region). Such a solar cell is obtained by a single crystal solar cell. That is, the solar cell SB has a sensitivity in a wavelength range from the visible light region to the infrared light region, and a maximum sensitivity in the near infrared light region.

As a result, the sensitivity of the combined liquid crystal plate LC and solar cell SB is relatively high in the near-infrared light region regardless of the on / off state of the triac Q, and is low in the visible light region when the triac Q is on. High when off.

Since sunlight has a spectral characteristic as shown in FIG. 6A and a fluorescent lamp has a spectral characteristic as shown in FIG. 6B, the output of the solar cell SB for each of them is shown in FIG. (A) and (b). FIGS. 7A and 7B show when the triac Q is off and when it is on. For sunlight, the output voltage of the solar cell SB changes with turning on and off the triac Q in the visible light region, but hardly changes in the near-infrared light region. Is in the visible light range, the output voltage of the solar cell SB greatly changes with the turning on and off of the triac Q.

As is clear from the characteristics shown in FIGS. 7A and 7B, even when illumination light is incident at night or the like, the solar cell SB
Does not increase, and as a result, the ON state of the triac Q is maintained. On the other hand, when sunlight comes in at dawn, light in the near-infrared light region generates a relatively large output voltage from the solar cell SB, and the triac Q can be immediately turned off. If the sunlight decreases in the evening, the light in the visible light region and the light in the near-infrared light region both decrease, so that the triac Q can be immediately turned on.

As shown in FIG. 8, the illuminance sensor A is mounted on a printed circuit board 21 together with a surge absorber ZNR and resistors R1, R2, R3 (only one is shown as a resistor R in the figure). It is stored in the case 20 together with the attached TRIAC Q. A pair of connecting legs 22a protrude from the heat radiating plate 22, and the distal ends of the connecting legs 22a are inserted into the connecting holes 21a provided in the printed circuit board 21, and are connected by caulking or soldering. Also,
The leads of the triac Q are soldered to the printed circuit board 21. In this state, the heat sink 22 is fixed to the case 20 using a pair of mounting screws 23. Two electric wires 24 connected to a series circuit of an AC power supply AC and a load L are also connected to the printed circuit board 21.

Case 20 for housing printed circuit board 21
Are bases 2 each formed of a synthetic resin in a box shape.
5 and the cover 26 are connected and formed by assembly screws (not shown). A light receiving cover 27 is attached to a portion of the cover 26 corresponding to the front of the illuminance sensor A, and external light enters the illuminance sensor A through the light receiving cover 27. A mounting bracket 29 is attached to the outside of the case 20 by a fixing screw 28, and the case 20 can be mounted on a house or the like using the mounting bracket 29.

As described above, in this embodiment, the change in the transmittance of the liquid crystal plate LC to natural light is reduced and the change in the transmittance of the liquid crystal plate LC to illumination light is increased.
The hysteresis magnification for natural light can be reduced, and the hysteresis magnification for illumination light can be increased. As a result, the transmittance of the liquid crystal panel LC is extremely low even when light from a headlight of a car is incident when the triac Q is turned on at night and the lighting load as the load L is lit. The on state of the triac Q is maintained. On the other hand, when the amount of sunlight increases at dawn, the transmittance of the liquid crystal panel LC with respect to natural light is low, so that the triac Q can be immediately turned off. In short, it is easy to respond to natural light, it is possible to quickly control the load L according to the change in ambient brightness, and it is difficult to respond to the change in brightness with respect to illumination light. Malfunction of the load L due to headlights or other lighting can be prevented.

(Second Embodiment) In this embodiment, the first
An example in which a filter is used in addition to the liquid crystal plate LC in the embodiment will be described. The filter used here has different transmittances in the visible light region and the infrared light region as shown in FIG. 9A, has a substantially constant transmittance in the visible light region, and has a near infrared light region. In this case, the transmittance is lower than in the visible light region.

By arranging such a filter on the incident path of external light to the solar cell SB in the first embodiment, the output voltage of the solar cell SB with respect to natural light can be changed as shown in FIG. ). That is, since an output as shown in FIG. 7A is obtained from the characteristics of the solar cell SB and the liquid crystal plate LC with respect to natural light as shown in FIG. 6A, a filter having the characteristics as shown in FIG. , The output of the solar cell SB becomes as shown in FIG. As a result, the hysteresis magnification for natural light can be adjusted according to the characteristics of the filter. Note that FIG. 9 shows when the triac Q is off, and shows when the triac Q is on. Other configurations and operations are the same as those of the first embodiment.

(Third Embodiment) As described in the first embodiment, since the polarizing plates PL are provided on both sides of the liquid crystal plate LC, the light passing through both polarizing plates PL By appropriately setting the relative angle of the vibrating surface, the transmittance including the liquid crystal plate LC and the polarizing plate PL can be adjusted. Here, for the sake of simplicity, a change in the vibration plane of light while passing through the liquid crystal plate LC is ignored. That is, assuming that the vibration plane of light is the same before and after the liquid crystal plate LC, both polarizing plates PL
When the oscillating surfaces of light passing through each other coincide, the transmittance of the polarizing plate PL is approximately 100%, and the transmittance decreases as the angle difference between the oscillating surfaces increases. For example, both polarizing plates P
When the vibration planes of the light passing through L coincide, the liquid crystal plate L
The transmittance of C and the polarizing plate PL is as shown in FIG. 5A, and the output voltage of the solar cell SB is as shown in FIG. 7A. On the other hand, if there is an angle difference between the vibration planes of the light passing through both polarizing plates PL, the liquid crystal plate LC and the polarizing plates P
The transmittance of L has characteristics as shown in FIG. 10A, for example, and therefore the output voltage of the solar cell SB is as shown in FIG.
The characteristics are as follows. Note that FIG. 10 shows when the triac Q is off, and shows when the triac Q is on. As described above, when the polarizing plate PL is used, it is possible to adjust the entire transmittance without changing the changing tendency of the transmittance with respect to the wavelength. For example, when the hysteresis magnification in the visible light region becomes too large when a filter is used as in the second embodiment, the hysteresis magnification can be reduced by appropriately adjusting the relative positional relationship of the polarizing plates PL. It can be adjusted to an appropriate range. Other configurations and operations are the same as those of the first embodiment.

(Fourth Embodiment) In each of the above-described embodiments, an example has been described in which a single crystal solar cell is used as the solar cell SB. However, the single crystal solar cell has a spectral sensitivity different from human luminosity characteristics. Because of the characteristics, the response of the illuminance sensor A may be uncomfortable. As described above, when a response close to the visibility characteristics of a person is required, an amorphous solar cell may be used as the solar cell SB. The spectral sensitivity characteristics of the amorphous solar cell are as shown in FIG. 11, which substantially matches the human visual sensitivity characteristics shown in FIG. That is, an effective output voltage is obtained for light having a wavelength of 400 to 700 nm, and the maximum sensitivity is 500 n.
m. Assuming that the spectral characteristic of the transmittance of the liquid crystal plate LC is as shown in FIG. 5A, the output voltage of the solar cell SB is as shown in FIG. Here, FIG. 12 shows when the triac Q is off and when it is on. As is clear from FIG. 12, when an amorphous solar cell is used, the hysteresis magnification becomes very large in the visible light region.
Therefore, as in the third embodiment, if the transmittance is adjusted by adjusting the relative position of the polarizing plate PL, the total transmittance of the liquid crystal plate LC and the polarizing plate PL can be reduced as shown in FIG.
The output characteristics of the solar cell SB with respect to natural light having the spectral distribution shown in FIG. 6A are as shown in FIG. 13B. FIG. 13 shows when the triac Q is off and when it is on. That is,
It is possible to reduce the hysteresis magnification. Other configurations and operations are the same as those of the first embodiment.

(Fifth Embodiment) In the present embodiment, the part for controlling the transmittance using the polarizing plate PL is a part of the view range of the solar cell SB. That is, in each of the above-described embodiments, the polarizing plate is provided so as to correspond to the entire area of the viewing range of the solar cell SB. However, in this embodiment, only a part of the viewing area of the solar cell SB is provided as shown in FIG. Light is attenuated by the polarizing plate PL. In other words, for the remaining area of the viewing range of the solar cell SB, the polarizing plate P
Dimming by L is not performed. That is, the polarizing plate P
While the dimming by L is performed, the decrease in the amount of light is smaller than in the case where the dimming is performed in the entire area of the solar cell SB, and the overall sensitivity can be increased. Other configurations and operations are the same as those of the first embodiment.

(Sixth Embodiment) In the present embodiment, the portion for controlling the transmittance using the liquid crystal plate LC is a part of the view range of the solar cell SB. That is, in each of the above-described embodiments, the transmittance of the liquid crystal plate LC is changed in the entire area of the viewing range of the solar cell SB. However, in the present embodiment, as shown in FIG. , Light is transmitted through the liquid crystal plate LC (the area where the light is transmitted is indicated by Da). In addition, light is not transmitted through the liquid crystal plate LC in the remaining region Db of the viewing range of the solar cell SB. Such a liquid crystal plate LC can be realized by not providing an electrode in a region that does not transmit light. Other configurations and operations are the same as those of the first embodiment.

(Seventh Embodiment) This embodiment is similar to FIG.
As shown in FIG. 6, an example in which the illuminance sensor A is applied to an automatic blinker that connects the AC power supply AC and the load L with three terminals is shown. In addition, a DC drive type electromagnetic relay is used as the switch element instead of the triac Q.

Since the electromagnetic relay is of a DC drive type, the illuminance sensor A also employs a configuration corresponding to DC, and one MOSFET Q3 is used as the variable impedance element VI. A resistor R and a capacitor C are connected in parallel to the solar cell SB, and the positive electrode of the solar cell SB is a MOSFET.
Connected to the gate of Q3. A high resistance is used for the resistor R. The variable impedance element SW is composed of a depletion type (normally-on type) MOSFET Q3. The gate is connected to the positive electrode of the solar cell SB as a control terminal, and the source is connected to the negative electrode of the solar cell SB.

The variable impedance element VI is connected in series with the relay coil Ry of the electromagnetic relay, and is connected in series between the variable impedance element VI and the relay coil Ry between the DC output terminals of a rectifier DB composed of a diode bridge for full-wave rectification of the AC power supply AC. The circuit is connected. The electromagnetic relay is a DC drive type, and a DC voltage higher than the operating voltage is applied to the relay coil R.
It is configured to turn on the contact r when applied to y. A resistor R4 is connected in series to one AC input terminal of the rectifier DB, and an AC power supply AC is connected to both ends of a series circuit of the rectifier DB and the resistor R4. A surge absorber ZNR is connected in parallel to a series circuit of the rectifier DB and the resistor R4. On the other hand, the contact r of the electromagnetic relay is inserted between the AC power supply AC and a load L such as a lighting load. That is,
The contact r is connected to a series circuit of an AC power supply AC and the load L, and power to the load L is turned on and off by turning on and off the contact r. Here, a smoothing capacitor C1 is connected in parallel to the relay coil Ry to smooth the output voltage of the rectifier DB and apply a substantially constant DC voltage to the relay coil Ry. Further, resistors R2 and R
3 are connected in series, and the above-mentioned liquid crystal panel LC is connected in parallel to one resistor R3. That is, the voltage applied to the liquid crystal plate LC is a voltage obtained by dividing the voltage across the contact r by the resistors R2 and R3. As described above, since the smoothing capacitor C1 is connected in parallel with the relay coil Ry, even when the contact r is turned on, such as at night, strong light is emitted and the variable impedance element VI becomes non-conductive. In addition, it is possible to avoid an erroneous operation in which the current continues to flow through the relay coil Ry by the capacitor C1, the contact r is maintained in the on state, and the contact r is immediately turned off.

As described above, in this embodiment, since the electromagnetic relay is used for controlling the energization of the load L, a heat radiating plate and components for preventing noise are not required.
0 is relatively small. Other configurations and operations are the same as those of the first embodiment.

[0045]

According to the first aspect of the present invention, there is provided a photovoltaic element for generating a voltage corresponding to the brightness of external light, and a variable impedance element for controlling a passing impedance according to an output voltage of the photovoltaic element. And a light amount adjusting member disposed on at least a part of an incident path of external light to a light receiving surface of the photovoltaic element and having a transmittance controlled by an external signal corresponding to a passing impedance of the variable impedance element. A light amount adjusting member whose transmittance is controlled by an external signal corresponding to the passing impedance of the variable impedance element that changes according to the brightness of the external light is disposed on the incident path of the external light to the photovoltaic element. Therefore, it is possible to add hysteresis to the relationship between the brightness of external light and the passing impedance of the variable impedance element. In other words, by providing an external signal so as to reduce the transmittance of the light amount adjusting member when the external light decreases, the sensitivity can be reduced when the amount of external light is small. Settings can be made so that malfunction does not occur even when light enters. Also, since there is no need to provide a delay element between the solar cell and the variable impedance element,
When the change in the amount of external light is sufficiently large, the transmittance of the light amount adjusting member can be immediately increased without causing a time delay.

According to a second aspect of the present invention, in the first aspect of the present invention, an external signal for controlling the light amount adjusting member is transmitted when the amount of light incident on the photovoltaic element becomes a specified value or less. The sensitivity is reduced when the amount of external light falls below a specified value, so the sensitivity is reduced when the amount of external light is reduced, such as at night. It is possible to set so as not to respond to headlights and the like.

According to a third aspect of the present invention, in the first or second aspect of the present invention, the light amount adjusting member is a transmissive liquid crystal plate whose transmittance changes according to the strength of an electric field applied to the liquid crystal. A liquid crystal plate is used as a light amount adjusting member. The liquid crystal plate is driven by an electric field and has a very large impedance, so that the power consumption is small. That is, the variable impedance element is driven by the electromotive force of the photovoltaic element, and the power required for the external signal for controlling the light amount adjusting member is small, so that the operation can be performed with very small power.

According to a fourth aspect of the present invention, in the third aspect of the invention, the liquid crystal plate controls a transmittance of a part of an incident path of external light to the photovoltaic element. Since the amount of incident light is controlled only by a part of the incident path of the external light to the power element, the change width of the amount of light due to the control of the liquid crystal plate can be reduced as compared with the case where the incident light amount of the entire incident path is controlled. Yes, this also allows the hysteresis characteristics to be adjusted.

According to a fifth aspect of the present invention, in the third or fourth aspect of the present invention, a polarizing plate is disposed on each of the front and back sides of the liquid crystal plate, and the transmittance of the polarizing plate and the liquid crystal plate is such that light passing through each polarizing plate is transmitted. The transmittance is adjusted according to the relative position of the vibrating surface of the light passing through the polarizing plate, so that the overall amount of light incident on the photovoltaic element can be adjusted. Become.

According to a sixth aspect of the present invention, in the fifth aspect of the present invention, the polarizing plate is provided in a part of an incident path of external light to the photovoltaic element. Since the amount of incident light is adjusted only by a part of the incident path of the external light to the power element, the variation width of the amount of light due to the polarizing plate can be reduced as compared with the case where the incident light amount of the entire incident path is adjusted.

According to a seventh aspect of the present invention, in the third aspect of the present invention, the photovoltaic element is a single-crystal solar cell and has sensitivity in a wavelength region extending between a visible light region and a near infrared light region, The liquid crystal plate has different transmittance characteristics between a visible light region and an infrared light region, and a combination of a spectral sensitivity characteristic of a photovoltaic element and a transmittance characteristic of a liquid crystal plate increases hysteresis with respect to illumination light. Thus, the hysteresis for natural light can be reduced. In other words, it is possible to provide a hysteresis characteristic that does not respond even if illumination light or light from a headlight is incident as external light at night, and immediately responds if sunlight enters with dawn.

According to an eighth aspect of the present invention, in the seventh aspect of the present invention, the solar cell having the maximum sensitivity in the infrared light region is used as the solar cell. The combination with the rate characteristic makes it possible to increase the hysteresis for the illumination light and to reduce the hysteresis for the natural light.

According to a ninth aspect of the present invention, in the first aspect of the present invention, a filter having different transmittances in a visible light region and an infrared light region is added to an incident path of external light to a light receiving surface of the photovoltaic element. Thus, the amount of light incident on the photovoltaic element can be adjusted according to the wavelength of light, and a desired hysteresis characteristic can be obtained.

According to a tenth aspect of the present invention, in the first aspect, the variable impedance element is made of a MOSFET and an output voltage of the photovoltaic element is applied to a gate and a source. Since it is driven, a large output current is not required as a photovoltaic element, and as a result, downsizing is possible.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is an exploded perspective view of the same.

FIGS. 3A and 3B show the same as above, wherein FIG. 3A is a front view with a liquid crystal plate removed, and FIG. 3B is a cross-sectional view.

FIG. 4 is a perspective view showing a liquid crystal plate used in the above.

FIG. 5 is an operation explanatory view of the above.

FIG. 6 is an operation explanatory view of the above.

FIG. 7 is an operation explanatory diagram of the above.

FIG. 8 is an exploded perspective view showing an automatic blinker using the above.

FIG. 9 is an operation explanatory view showing a second embodiment of the present invention.

FIG. 10 is an operation explanatory view showing a third embodiment of the present invention.

FIG. 11 is an operation explanatory diagram of the above.

FIG. 12 is an operation explanatory view of the above.

FIG. 13 is an operation explanatory view showing a fourth embodiment of the present invention.

FIG. 14 is an operation explanatory view showing a fifth embodiment of the present invention.

FIG. 15 is an operation explanatory view showing a sixth embodiment of the present invention.

FIG. 16 is a circuit diagram showing a seventh embodiment of the present invention.

[Explanation of symbols]

 LC liquid crystal plate PL polarizing plate Q1, Q2, Q3 MOSFET SB solar cell VI Variable impedance element

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Yoshinori Akinari 1048 Kazuma Kadoma, Osaka Pref. Matsushita Electric Works F-term (reference) 5J050 AA36 AA47 BB21 CC07 DD08 DD12 DD18 EE02 EE12 EE17 EE22 FF09 FF13

Claims (10)

[Claims] 1. A photovoltaic element that generates a voltage according to the brightness of external light, a variable impedance element whose passing impedance is controlled according to an output voltage of the photovoltaic element, and the photovoltaic element. And a light amount adjusting member disposed on at least a part of an incident path of external light to the light receiving surface and having a transmittance controlled by an external signal corresponding to a passing impedance of the variable impedance element. 2. An external signal for controlling the light amount adjusting member is set so as to decrease the transmittance of the light amount adjusting member when the light amount incident on the photovoltaic element becomes equal to or less than a specified value. The illuminance sensor according to claim 1, wherein 3. The illuminance sensor according to claim 1, wherein the light amount adjusting member is a transmissive liquid crystal plate whose transmittance is changed according to the strength of an electric field applied to the liquid crystal. 4. The illuminance sensor according to claim 3, wherein the liquid crystal plate controls a transmittance of a part of an incident path of external light to the photovoltaic element. 5. A polarizing plate is disposed on both sides of the liquid crystal plate, and transmittances of the polarizing plate and the liquid crystal plate are set by a relative angle of a vibration plane of light passing through each polarizing plate. The illuminance sensor according to claim 3 or 4. 6. The illuminance sensor according to claim 5, wherein the polarizing plate is provided on a part of a path of external light incident on the photovoltaic element. 7. The photovoltaic element is a single-crystal solar cell and has sensitivity in a wavelength range extending between a visible light region and a near-infrared light region, and the liquid crystal plate has a visible light region and an infrared light region. 4. The illuminance sensor according to claim 3, wherein transmittance characteristics of the illuminance sensor and the illuminance sensor are different. 8. The illuminance sensor according to claim 7, wherein the solar cell has a maximum sensitivity in an infrared light region. 9. The filter according to claim 1, wherein a filter having different transmittances in a visible light region and an infrared light region is added to an incident path of external light to a light receiving surface of the photovoltaic element. Illuminance sensor. 10. The variable impedance element is a MOS
The illuminance sensor according to claim 1, wherein an output voltage of the photovoltaic element is applied to a gate and a source of an FET.