JP4387905B2 - Semiconductor optical sensor device and information equipment incorporating the same - Google Patents

Semiconductor optical sensor device and information equipment incorporating the same Download PDF

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JP4387905B2
JP4387905B2 JP2004271393A JP2004271393A JP4387905B2 JP 4387905 B2 JP4387905 B2 JP 4387905B2 JP 2004271393 A JP2004271393 A JP 2004271393A JP 2004271393 A JP2004271393 A JP 2004271393A JP 4387905 B2 JP4387905 B2 JP 4387905B2
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illuminance
output
amplifier
circuit
comparator
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JP2006086425A (en
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英之 森
由貴子 瀧場
浩 鈴永
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株式会社東芝
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  The present invention relates to a semiconductor optical sensor device for an illuminance sensor, for example, a semiconductor optical sensor capable of detecting illuminance over a wide range from several lux to tens of thousands of lux, and an information device incorporating the same. It is about.

An illuminance sensor (semiconductor optical sensor device) is an optical sensor that outputs a linear output according to ambient illuminance (brightness), and is mainly used in mobile phones in accordance with ambient illuminance (brightness). It is used for ON / OFF control of a light emitting diode (LED) of a backlight or an operation unit (key (key) unit). For example, when the surroundings are bright, the backlight and the light emitting diodes of the key unit are turned off. When the surroundings are dark, they are used as an ambient illuminance sensor for suppressing unnecessary power consumption by turning on or adjusting the brightness.
In a cellular phone or the like, generally, on / off of a light emitting diode in a key part is controlled in a low illuminance range of about several lux to 100 lux. Since the conventional illuminance sensor has been used only for on / off control of the light emitting diode of the key portion, it is designed to output a linear output in a low illuminance range of several lux to 100 lux.
However, at present, power consumption of the liquid crystal backlight is increased by turning on and off the light-emitting diodes on the operation surface (key part), and by making the liquid crystal full color, and in order to obtain a high-quality display screen, The brightness control of the combined backlight is required. The luminance adjustment of the liquid crystal backlight is performed at a high illuminance of tens of thousands of lux due to the properties of the liquid crystal.

A conventional high-sensitivity illuminance sensor optimized for control of a conventional key unit cannot detect high illuminance of tens of thousands of lux because the output is saturated.
Also, in the case of an illuminance sensor with reduced sensitivity so that high illuminance of tens of thousands of lux can be detected, the output at low illuminance, which is the control illuminance of the key part, is indistinguishable from dark current etc. Therefore, there is a problem that detection becomes difficult.
As a conventional optical sensor device, Patent Document 1 describes a photoelectric switch circuit having two amplifiers having different gains and a comparator (binarization circuit). Two amplifiers are provided according to the purpose. Patent Document 2 describes a photodetection circuit having a wide dynamic range. Having a plurality of amplifiers having different gains, the output of each amplifier is first subjected to A / D conversion with coarse decomposition, and an amplifier whose conversion value is closest to the median of the output range is selected. Further, the low resolution A / D converter can be replaced with a comparator, and in that case, it is described that a comparator having a value corresponding to the gain of each amplifier is provided for each amplifier.
JP-A-6-294874 JP-A-5-63572

The present invention provides a semiconductor photosensor device capable of detecting illuminance in a wide range of illuminance from low illuminance of several lux to high illuminance of tens of thousands of lux, and information equipment incorporating the semiconductor photosensor device.

  According to one aspect of the semiconductor optical sensor device of the present invention, a photodiode unit, a plurality of amplifiers having different gain characteristics connected to the output of the photodiode unit, and a plurality of amplifiers corresponding to each of the plurality of amplifiers, A comparison voltage generation circuit for generating a plurality of different reference voltages and a logic signal provided corresponding to each of the plurality of amplifiers, comparing the output of the corresponding amplifier and the reference voltage, and based on the comparison result Is provided, and illuminance detection is performed based on logic signals of a plurality of bits from the plurality of comparators.

Digital output capable of accurate detection can be obtained at low illuminance of several lux to high illuminance of tens of thousands of lux.

Hereinafter, embodiments of the invention will be described with reference to examples and reference examples .

Reference example 1

First, Reference Example 1 will be described with reference to FIGS.
1 is a circuit block diagram of an illuminance sensor for explaining this reference example , FIG. 2 is a characteristic diagram for explaining the operation of the illuminance sensor of FIG. 1, and FIG. 3 is a logic circuit 1 constituting the illuminance sensor of FIG. For example, FIG. 4 is a characteristic diagram showing the relationship between the illuminance of light input to the illuminance sensor and the output of the illuminance sensor, and FIG. 5 shows the configuration and manufacturing method of the low-illuminance and high-illuminance photodiode parts of this reference example . It is a top view to explain.
As shown in FIG. 1, a photodiode unit 1 including a plurality of photodiode units having different illuminance characteristics is configured such that the output thereof is input to a first amplifier 3 via a switch (SW) 2. .

  The horizontal axis in FIG. 2 indicates the illuminance of light input to the illuminance sensor. 2A represents the output of the photodiode unit (abbreviated as PD), FIG. 2B represents the output of the mode detection circuit and the comparator (hereinafter referred to as a comparator), FIG. 2C shows the output of the illuminance sensor. FIG. 2A illustrates the illuminance state of light input to the illuminance sensor illustrated in FIG. FIG. 2C shows the output of the illuminance sensor corresponding to the state. FIG. 2A shows an illuminance-output characteristic line (1) when using a low-illuminance photodiode part and an illuminance-output characteristic line (2) when using a high-illuminance photodiode part. One of the characteristic lines is applied depending on the illuminance state of light input to the illuminance sensor.

The photodiode unit 1 includes a high-sensitivity low-illuminance photodiode unit (PD1) and a low-sensitivity high-illuminance photodiode unit (PD2). The first amplifier 3 includes at least one amplifier, converts the output (signal current) from the photodiode unit 1 into a voltage and amplifies the voltage, and outputs the output to the second amplifier 4. The second amplifier 4 includes at least one amplifier, and may have characteristics such as an amplification factor that are different from those of the first amplifier 3. This illuminance sensor has a mode detection circuit 8 that controls a switch 2 that switches the photodiode unit 1 when the output of the first amplifier 3 is monitored and reaches a certain illuminance. The switch 2 receives the output signal of the mode detection circuit 8 and switches the output signal that enters the first amplifier 3. The illuminance sensor further includes a reference voltage generation circuit 6 such as a band gap constant voltage circuit and a comparison voltage generation circuit 7 that generates a comparison reference voltage based on the output of the reference voltage generation circuit 6. The mode detection circuit 8 compares the output voltage of the comparison voltage generation circuit 7 with the output of the first amplifier 3 and controls the mode of the switch 2. The output of the second amplifier 4 is input to at least one (one in this reference example ) comparator 5, where it is compared with the output voltage of the comparison voltage generation circuit 7 to output a logic signal. The output of the comparator 5 is input to the logic circuit 9 and a digital output is output to the output unit 10. An example of the logic circuit 9 is shown in FIG. The illuminance sensor of this embodiment is formed on one semiconductor chip.

Next, the operation of the illuminance sensor of Reference Example 1 will be described with reference to FIG.
When light with a certain illuminance is irradiated to the illuminance sensor, the light is converted into a current in the photodiode unit 1 including the high-sensitivity low-illuminance photodiode unit (PD1) and the low-sensitivity high-illuminance photodiode unit (PD2). Is done. The photodiode unit for low illuminance has linear illuminance-output characteristics from several lux to several hundred lux. The photodiode portion for high illuminance has linear illuminance-output characteristics from several hundred lux to tens of thousands of lux. Photodiodes are not suitable for detecting the illuminance because they output saturation with respect to the illuminance outside the linear region. The switching illuminance EV1 is set within an illuminance range having linear illuminance-output characteristics between the low illuminance photodiode portion and the high illuminance photodiode portion. For example, the light receiving area has a high sensitivity so that a large photocurrent can be obtained from the high sensitivity low illuminance photodiode part for the same light incident on the illuminance sensor. The low illuminance photodiode part is large, and the low sensitivity high illuminance photodiode part is small. In addition to changing the area, the low-sensitivity photodiode for high illuminance may be covered with a neutral density filter, or both may be used in combination.

The difference between the low-illuminance and high-illuminance photodiode portions and how to make them will be described with reference to FIG. FIG. 5A shows an example in which the illuminance characteristics of the photodiode (PD) portion are changed depending on the area. The high-illuminance photodiode portion has a smaller area than the low-illuminance photodiode portion. In FIG. 5B, a plurality of photodiodes having a predetermined area are arranged, and the number of photodiodes used is switched according to the illuminance characteristics of the photodiode portion. A switch is attached to each photodiode (PD), and the switch is turned on and off to obtain a predetermined illuminance characteristic. The high-illuminance photodiode section has a smaller number of photodiodes than the low-illuminance photodiode section.
In the case of FIG. 5C, an element having the same area and structure is used for the photodiode (PD) of the photodiode portion, and a light shielding filter is formed on a part of the photodiode (PD) of the photodiode portion for high illuminance. And changing the illuminance characteristics.

  In the initial state, the switch 2 for switching the signal output from each photodiode unit entering the first amplifier 3 is connected to the low-illuminance photodiode unit (PD1). The relationship between the illuminance and the illuminance sensor output at this time follows the illuminance-output characteristic line (1) when the low illuminance photodiode portion of FIG. 2A is used (this is referred to as a low illuminance mode). When the mode detection circuit 8 detects that the incident light becomes strong, the illuminance becomes EV1 (see FIG. 2A), and the output of the first amplifier 3 has reached a predetermined “mode circuit threshold 1”. The output of the mode detection circuit 8 is inverted (0 → 1), and the switch 2 switches the mode to the high illuminance photodiode part (PD2) side. At this time, since the output of the first amplifier 3 falls, the mode detection circuit 8 maintains the mode state, and the threshold value of the mode detection circuit 8 is switched to a predetermined “mode circuit threshold value 2”. The relationship between the illuminance and the illuminance sensor output at this time follows the illuminance-output characteristic line (2) when the high illuminance photodiode portion of FIG. 2A is used (this is referred to as a high illuminance mode).

Once the illuminance falls to EV2 after entering the high illuminance mode, the mode detection circuit 8 detects that the output of the first amplifier 3 has fallen below “mode circuit threshold 2”, and outputs the output of the mode detection circuit 8 Invert (0 → 1)), and switch 2 switches the mode to the low-illuminance photodiode (PD1) side. At that time, the output of the first amplifier 3 rises, but the mode detection circuit threshold is switched to “mode circuit threshold 1”, so that the state is maintained.
The output potential of the first amplifier 3 is compared with a potential matched to the illuminance to be detected by the comparator 5. In this example, when the input light exceeds the comparison reference potential (detection illuminance 1, detection illuminance 2) generated by the comparison voltage generation circuit 7, the output of the comparator 5 changes from “0” to “1”. Since the present invention is a digital output, the illuminance thresholds to be detected are set to detected illuminance 1 (for example, 100 lux) and detected illuminance 2 (for example, 50000 lux). Further, with the detected illuminance 1 and detected illuminance 2, the logic circuit 9 can calculate the illuminance by calculating the output potential of the mode detection circuit 8 and the output of the comparator. For example, in this example, by taking AND and OR of the outputs of the mode detection circuit 8 and the first amplifier 3, three illuminance ranges as shown in FIG. 4 can be identified.

The logic circuit 9 is shown in FIG. 3, for example. As shown in the figure, the output 1 at the output unit 10 of the illuminance sensor is obtained by inputting and calculating the output of the mode detection circuit 8 and the output of the comparator 5 to an AND circuit (AND). For (output of mode detection circuit 8) / (output of comparator 5) 1/1, 0/1, 1/0, 0/0, output 1 is 1, 0, 0, 0, respectively. Similarly, the output 2 is obtained by calculating the output of the mode detection circuit 8 and the output of the comparator 5 by inputting them into an OR circuit (AND). When (output of the mode detection circuit 8) / (output of the comparator 5) is 1/1, 0/1, 1/0, 0/0, the output 1 is 1, 1, 1, 0, respectively. As shown in FIG. 4 , the illuminance sensor uses the low illuminance photodiode portion in the state 1, and the illuminance sensor for the low illuminance and the high illuminance according to the detected illuminance. In the state 3, the high-illuminance photodiode portion is used.
For the reference voltage circuit, a band gap circuit with little temperature change is used, and the voltage is compared with the illuminance to be detected by a voltage conversion circuit using a resistance voltage divider or operational amplifier, and supplied to the comparator. To do.
In this configuration, the sensitivity of the photodiode unit is adjusted so that the comparison reference potential of the comparator is one potential with respect to the illuminance to be detected. Of course, a plurality of comparison potentials and comparators may be prepared.

In this embodiment, by independently providing two photodiode parts having different illuminance characteristics for low illuminance and high illuminance and switching them, the illuminance from low illuminance of several lux to high illuminance of tens of thousands of lux is as follows: Digital output that can be detected accurately is obtained.

Reference example 2

Next, Reference Example 2 will be described with reference to FIGS.
This reference example is characterized in that it includes a plurality of comparators, whereas the reference example 1 uses one comparator. 6 and 7 are circuit block diagrams of the illuminance sensor for explaining this embodiment.
The photodiode portion used in this reference example may have the same characteristics as in Reference Example 1 , but is not limited to this. In addition, amplifiers having the same characteristics such as amplification degree may be used, or different amplifiers may be used. As shown in FIG. 6, the output of the photodiode unit 1 including a plurality of photodiode units having different illuminance characteristics is input to the first amplifier 3 via the switch (SW) 2. The photodiode unit 1 includes a high-sensitivity low-illuminance photodiode unit (PD1) and a low-sensitivity high-illuminance photodiode unit (PD2). The first amplifier 3 composed of at least one amplifier converts the output (signal current) from the photodiode unit 1 into a voltage, amplifies it, and outputs the output to the second amplifier 4 composed of at least one amplifier. The first and second amplifiers may have the same characteristics or may be different. The illuminance sensor has a mode detection circuit 8 that switches the photodiode unit 1 when the illuminance is monitored by monitoring the output of the first amplifier 3, and the switch 2 receives the output signal of the mode detection circuit 8 and receives the first signal. The output signal entering the amplifier 3 is switched.

  The illuminance sensor further includes a reference voltage generation circuit 6 such as a band gap constant voltage circuit and a comparison voltage generation circuit 7 that generates a comparison reference voltage based on the output of the reference voltage generation circuit 6. The mode detection circuit 8 compares the output voltage of the comparison voltage generation circuit 7 with the output of the first amplifier 3 and controls the mode of the switch 2. The output of the second amplifier 4 is input to at least one comparator 5 (one in this embodiment), where it is compared with the output voltage of the comparison voltage generation circuit 7 to output a logic signal. The output of the comparator 5 is input to the logic circuit 9 and a digital output is output to the output unit 10. The illuminance sensor of this embodiment is formed on one semiconductor chip.

Next, the operation of the illuminance sensor of Reference Example 2 will be described.
When light with a certain illuminance is irradiated to the illuminance sensor, the light is converted into a current in the photodiode unit 1 including the high-sensitivity low-illuminance photodiode unit (PD1) and the low-sensitivity high-illuminance photodiode unit (PD2). Is done. From the high-sensitivity low-illuminance photodiode portion, a larger photocurrent can be obtained for the same light incident on the illuminance sensor than the low-sensitivity high-illuminance photodiode portion.
In an initial state, the switch 2 for switching a signal output from each photodiode unit entering the first amplifier 2 is connected to the low-illuminance photodiode unit (PD1). The incident light becomes strong and the illuminance (EV1 in the first embodiment) corresponding to the threshold of the mode detection circuit 8 (“mode circuit threshold 1”) is obtained (see FIG. 2A ), and the output of the first amplifier 3 is When the mode detection circuit 8 detects that “mode circuit threshold value 1” is reached, the output of the mode detection circuit 8 is inverted, and the switch 2 is switched to the high-illuminance photodiode portion (PD2) side.

At this time, since the output of the first amplifier 3 is lowered, the mode detection circuit 8 maintains the mode state, the threshold of the mode detection circuit 8 is switched to “mode circuit threshold 2”, and the switch 2 has low illuminance. Switching to the photodiode part (PD2) side. Once the high illuminance mode is entered, when the illuminance falls to the illuminance (EV2 in the first embodiment) corresponding to “mode circuit threshold 1”, the mode detection circuit 8 indicates that the output of the first amplifier 3 is “mode circuit threshold 2”. ”Is detected, and the output of the mode detection circuit 8 is inverted. At that time, the output of the first amplifier 3 rises, but the threshold value of the mode detection circuit is switched to “mode circuit threshold value 1”, so that the state is maintained.
The output potential of the first amplifier 3 is compared with each of the plurality of output potentials of the comparison voltage generation circuit 7 according to the illuminance desired to be detected in each of the plurality of comparators 5.
The reference voltage circuit 6 uses a band gap circuit or the like with little temperature change, and generates a comparison potential that matches the illuminance to be detected by a voltage conversion circuit using a resistance voltage divider or an operational amplifier, and supplies it to the comparator. To do.

In Reference Example 1 , the sensitivity of the photodiode unit is adjusted by setting the comparison reference potential of the comparator as one potential for the illuminance to be detected. In this embodiment, a plurality of comparison potentials and comparators are prepared. . That is, a plurality of comparators 5 (comparator 1, comparator 2,..., Comparator n) are prepared. The comparison voltage generation circuit 7 generates n outputs corresponding to the number of comparators and inputs them to each of the plurality of comparators 5. Each comparator compares the output of the comparison voltage generation circuit 7 with the output of the second amplifier 4 and outputs the result to the logic circuit 9. The illuminance can be determined by calculating the output potential of the mode detection circuit 8 with the logic circuit 9. Further, by providing the necessary number of comparators and further calculating by the logic circuit 9, it is possible to reduce the number of output lines. For example, in the case of a 7-value detection number, output is possible with a combination of “0” and “1” of 3 bits (3 lines).

Next, another illuminance sensor of this reference example will be described with reference to FIG.
This example has the same basic structure as the illuminance sensor shown in FIG. Here, a structure in which the output of the storage device 11 such as a ROM is input to the comparison voltage generation circuit 7 is added. By making it possible to change with a storage device (ROM or the like) incorporating the comparison potential generation circuit, the detected illuminance can be easily changed as necessary. Furthermore, by making the storage device a rewritable storage device, such as an EPROM, it is possible to match variations factors such as sensitivity variations due to mounting by electrically rewriting the EPROM after mounting. Accuracy can be realized.
In this reference example, it is possible to provide not only two modes for high illuminance and low illuminance but also three or more modes such as for medium illuminance.
In this reference example , by separately providing two photodiode parts having different illuminance characteristics for low illuminance and high illuminance and switching them, in illuminance from low illuminance of several lux to high illuminance of tens of thousands of lux, Digital output that can be detected accurately is obtained.

Next, Embodiment 1 will be described with reference to FIGS.
Reference examples 1 and 2 are characterized by using two photodiode parts having different illuminance characteristics and switching them appropriately. In this example, however, the characteristics such as the two amplification factors are different. It is characterized in that the amplifier is switched appropriately. The illuminance characteristics of the photodiode portion used in this embodiment may be the same as or different from those of the photodiode portion used in the first and second embodiments. The same applies to the amplifier.
FIG. 8 is a circuit block diagram of the illuminance sensor for explaining this embodiment, and FIG. 9 is a characteristic diagram for explaining the operation of the illuminance sensor of FIG. The output of the photodiode unit 1 is input to the first amplifier 3. The first amplifier 3 converts the output (signal current) from the photodiode unit 1 into a voltage, amplifies it, and outputs the output to the second amplifier 4. The illuminance sensor further includes a reference voltage generation circuit 6 such as a band gap constant voltage circuit that is a basis of a comparison reference voltage of the comparator, and a comparison voltage generation circuit 7 that generates a comparison reference voltage based on the output of the reference voltage generation circuit 6. have.

Here, the second amplifier 4 includes a low illuminance amplifier 13 that requires high amplification and a high illuminance amplifier 14 that requires low amplification.
The low illuminance amplifier has linear input / output characteristics from several lux to several hundred lux by converting the input photocurrent into illuminance. Further, the high illumination amplifier has linear input / output characteristics from several hundred lux to several tens of thousands of lux. The output is constant with respect to the input outside the linear range. The switching illuminance is set within the range where the linear input / output characteristics of the low illuminance amplifier and high illuminance amplifier overlap.
The output of the second amplifier 4 is input to the comparator 5, where it is compared with the output voltage of the comparison voltage generation circuit 7 to output a logic signal. The comparator 5 includes a first comparator (comparator 1) and a second comparator (comparator 2). The output of the low-illuminance amplifier 13 is input to the first comparator, and the high-illuminance is input to the second comparator. The output of the amplifier 14 is input. The output of the comparator 5 is input to the logic circuit 9 and a digital output is output to the output unit 10. The illuminance sensor of this embodiment is formed on one semiconductor chip.

FIG. 9 shows the output potential of each amplifier and the characteristics of the comparator output for explaining the operation of the illuminance sensor of the first embodiment . When light with a certain illuminance is applied to the illuminance sensor, the light is converted into a current by the photodiode unit 1 and amplified to some extent by the first amplifier 3. The second amplifier 4 having the low illuminance amplifier 13 and the high illuminance amplifier 14 is amplified by a set amplification degree according to the illuminance desired to be detected, and is compared in the comparator 5 with the potential corresponding to the illuminance desired to be detected. Is done. Here, the illuminance to be detected is detected illuminance 1 and detected illuminance 2, the detected illuminance 2 is detected by the comparator 1, and the detected illuminance 1 is detected by the comparator 2. The potential adjusted to the detected illuminance 1 is the reference potential 1, and the potential adjusted to the detected illuminance 2 is the reference potential 2. In this example, when the input light exceeds the illuminance to be detected, the output of each comparator changes from “0” to “1”. That is, the output of the comparator 1 changes from “0” to “1” when the detected illuminance is 2, and the output of the comparator 2 changes from “0” to “1” when the detected illuminance is 1. It is.

  With the above configuration, the illuminance can be determined by looking at the comparator outputs “0” and “1”. As shown in FIG. 9C, the detected illuminance can be classified into state 1, state 2, and state 3. State 1 is lower than detected illuminance 1, state 2 is higher than detected illuminance 1, lower than detected illuminance 2, and state 3 is higher than detected illuminance 2. These states can be understood by detecting the output of the comparator 5 (comparator 1 / comparator 2). State 1 is 0/0, state 2 is 0/1, and state 3 is 1/1.

  Further, by installing the logic circuit 9, the output logic can be output in various combinations as required. For example, the AND circuit (AND) and the OR circuit (OR) shown in FIG. However, in FIG. 3, “mode detection” is read as “output of comparator 1” and “comparator detection” is read as “output of comparator 2”. In this case, the output 1 in the output unit 10 is obtained by inputting and calculating the output of the comparator 1 and the output of the comparator 2 into an AND circuit (AND). When (Comparator 1 output) / (Comparator 2 output) is 1/1, 0/1, 0/0, the output 1 is 1, 0, 0. Further, the output 2 in the output unit 10 is obtained by inputting and calculating the output of the comparator 1 and the output of the comparator 2 to an OR circuit (OR). When (Comparator 1 output) / (Comparator 2 output) is 1/1, 0/1, 0/0, the output 2 is 1, 1, 0. Therefore, when output 1 / output 2 is 0/0, it is state 1, when it is 0/1, it is state 2, and when 1/1, it is state 3.

The reference voltage generation circuit uses a band gap circuit with little temperature change, etc., and generates a comparison potential that matches the illuminance to be detected by a voltage conversion circuit using a resistive voltage divider or operational amplifier, and supplies it to the comparator .
In this configuration, the reference potential for comparison is adjusted with respect to the illuminance to be detected. However, the amplification factor of the amplifier may be matched with the reference potential as one potential. Of course, both the comparison potential and the amplification degree may be used.
Further, in the above example, the amplification degree of the high illuminance amplifier and that of the low illuminance amplifier are made different. However, the amplification degree of each amplifier may be the same, and the sensitivity of the photodiode portion may be made different. In other words. A low-sensitivity photodiode portion may be used for high illuminance, and a high-sensitivity photodiode portion may be used for low illuminance. Of course, both the sensitivity of the photodiode section and the amplification degree of the amplifier may be different.
In this embodiment, two amplifiers having different amplification factors suitable for low illuminance with high amplification and low illuminance and high illuminance are provided independently and switched between them, so that low illuminance of several lux is reduced to several tens of thousands. Digital output capable of accurate detection can be obtained for illuminance up to high lux.

Next, Example 2 will be described with reference to FIGS.
The reference examples 1 and 2 are characterized in that two photodiode parts having different illuminance characteristics are used and switched appropriately. In this embodiment, two or more amplification factors, etc. It is characterized in that amplifiers having different characteristics are used by switching appropriately.
10 and 11 are circuit block diagrams of the illuminance sensor for explaining this embodiment. As shown in FIG. 10, the output of the photodiode unit 1 is input to the first amplifier 3. The first amplifier 3 converts the output (signal current) from the photodiode unit 1 into a voltage and amplifies it, and outputs the output to the second amplifier 4. The illuminance sensor further includes a reference voltage generation circuit 6 such as a band gap constant voltage circuit that is a basis of a comparison reference voltage of the comparator, and a comparison voltage generation circuit 7 that generates a comparison reference voltage based on the output of the reference voltage generation circuit 6. have.

  The second amplifier 4 includes a plurality of amplifiers (amplifier 1, amplifier 2,..., Amplifier n) having different amplification degrees. The output of the second amplifier 4 is input to the comparator 5, where it is compared with the output voltage of the comparison voltage generation circuit 7 to output a logic signal. The comparator 5 is composed of a number of comparators (comparator 1, comparator 2,..., Comparator n) corresponding to a plurality of amplifiers constituting the second amplifier 4 respectively, and the first comparator (comparator 1) has a low level. The output of the amplifier for illuminance (amplifier 1) is input, and the output of the amplifier for illuminance (amplifier n) is input to the nth comparator (comparator n). The output of the comparator 5 is input to the logic circuit 9 and a digital output is output to the output unit 10. The illuminance sensor of this embodiment is formed on one semiconductor chip.

In the first embodiment , the case where the detected illuminance is binary has been described. However, as in this embodiment, even if there are three or more values (n value), the required number of comparison potentials and comparators are provided, or the comparison potential is For example, detection is possible by providing a necessary number of detection amplifiers and comparators. Further, by providing the logic circuit 9, it is possible to reduce the number of output lines. For example, in the case of a 7-value detection number, output is possible with a combination of “0” and “1” of 3 bits (3 lines).
For the reference voltage circuit, a band gap circuit with little temperature change is used, and the voltage is divided by resistance and a voltage conversion circuit using an operational amplifier, etc., and a comparison potential that matches the illuminance to be detected is generated and supplied to the comparator To do.
In this configuration, the reference potential for comparison is adjusted with respect to the illuminance to be detected. However, the amplification factor of the amplifier may be matched with the reference potential as one potential. Of course, both the comparison potential and the amplification degree may be used.

In this embodiment, a plurality of amplifiers (second amplifiers) having different amplification levels are provided independently, and these are switched, so that accurate detection can be performed at low illuminance of several lux to high illuminance of tens of thousands of lux. Can be obtained.
Next, another illuminance sensor of this embodiment will be described with reference to FIG.
This example has the same basic structure as the illuminance sensor shown in FIG. Here, a structure in which the output of the storage device 12 such as a ROM is input to the comparison voltage generation circuit 7 is added. By making it changeable by a storage device (ROM or the like) incorporating a comparison potential generation circuit, it is possible to easily change the detected illuminance according to the application. Furthermore, by using a rewritable storage device such as an EPROM, it becomes possible to match the variation factors such as sensitivity variations due to mounting by electrically rewriting the EPROM after mounting. High accuracy can be achieved.

In this embodiment, not only two modes for high illuminance and low illuminance but also three or more modes such as for medium illuminance can be provided.
In this embodiment, two amplifiers having different amplification levels are provided independently, and these are switched to provide a digital output capable of accurate detection at illuminance ranging from low illuminance of several lux to high illuminance of tens of thousands of lux. can get.
Furthermore, by making the storage device a rewritable storage device, such as an EPROM, it is possible to uniformly adjust the variation factors such as sensitivity variations due to mounting by electrically rewriting the EPROM after mounting. High accuracy can be achieved.

Next, Example 3 will be described with reference to FIG.
FIG. 12 is a schematic plan view of the mobile phone. A mobile phone is composed of an operation surface (key part) that is separated from the liquid crystal screen. The brightness of the liquid crystal screen and the key part is controlled so that any part can cope with the external environment. Therefore, the illuminance sensor described in these embodiments, which are one embodiment of the present invention, is incorporated in such a mobile phone. By incorporating this illuminance sensor, both the on / off of the light emitting diode of the key part controlled by low illuminance and the brightness control of the liquid crystal screen controlled by high illuminance are both formed on one chip. It can be effectively performed by a device (illuminance sensor).
As described above, according to the present invention, a plurality of detection parts having different illuminance characteristics, such as those for low illuminance and those for high illuminance, are provided independently, and several lux are obtained by switching them. Can provide a digital output illuminance sensor (semiconductor optical sensor device) capable of accurate detection at low illuminance to high illuminance of tens of thousands of lux. For example, in a mobile phone, an external ADC or CPU built-in can be provided. It is possible to provide a digital output semiconductor optical sensor device capable of both turning on and off the light emitting diode of the key unit controlled with low illuminance and controlling the brightness of the liquid crystal screen controlled with high illuminance without requiring an ADC or the like.

Thus, an illuminance sensor is mounted on an information device having a portion that detects and controls incident light with low illuminance and a portion that detects and controls incident light with high illuminance. Each control target in the portable device can be controlled based on the incident light detected by the illuminance sensor that is formed on one chip and can detect the illuminance in a wide illuminance range. Can be reduced. In the above-described embodiments, there are a case where a plurality of photodiode portions having different illuminance characteristics are provided independently for switching, and a case where two amplifiers having different amplification degrees are provided independently for switching them. Is larger than the photodiode, the former case is more advantageous in terms of miniaturization of the semiconductor device.
It is also possible to directly turn on / off the light emitting diode (LED) driver for illumination without going through the CPU.

The circuit block diagram of the reference example 1. FIG. The characteristic view explaining operation | movement of the illumination intensity sensor of FIG. FIG. 2 is a circuit diagram showing an example of a logic circuit constituting the illuminance sensor of FIG. 1. The characteristic view which shows the relationship between the illumination intensity of the light input into the illumination intensity sensor of FIG. 1, and an output. The top view explaining the structure of the photodiode part for low illuminance of Reference Example 1 , and how to make it. The circuit block diagram of the reference example 2. FIG. The circuit block diagram of the reference example 2. FIG. The circuit block diagram of Example 1 which is one Example of this invention. The characteristic view explaining operation | movement of the illumination intensity sensor of FIG. The circuit block diagram of Example 2 which is one Example of this invention. The circuit block diagram of Example 2 which is one Example of this invention. The schematic plan view of the mobile telephone of Example 3 which is one Example of this invention.

DESCRIPTION OF SYMBOLS 1 ... Photodiode part 2 ... Switch 3, 4 ... Amplifier 5 ... Comparator 6 ... Reference voltage generation circuit 7 ... Comparison voltage generation circuit 8 ... Mode detection circuit 9 .... Logic circuit 10 ... Output unit ... 11, 12 ... Memory circuit 13 ... Low illuminance amplifier 14 ... High illuminance amplifier

Claims (3)

  1. A photodiode section;
    A plurality of amplifiers having different gain characteristics connected to the output of the photodiode unit;
    A comparison voltage generation circuit for generating a plurality of different reference voltages corresponding to each of the plurality of amplifiers;
    A plurality of comparators provided corresponding to each of the plurality of amplifiers, comparing the output of the corresponding amplifier and the reference voltage, and outputting a logic signal based on the comparison result;
    An illuminance detection is performed based on a plurality of bits of logic signals from the plurality of comparators.
  2. The logic circuit according to claim 1 , further comprising a logic circuit that performs a logic operation based on a plurality of bit logic signals from the plurality of comparators, and outputs a logic operation result from the logic circuit as an illuminance detection result. The semiconductor optical sensor device described.
  3. An information device, wherein the semiconductor photosensor device according to claim 1 is incorporated.
JP2004271393A 2004-09-17 2004-09-17 Semiconductor optical sensor device and information equipment incorporating the same Active JP4387905B2 (en)

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JP2004271393A JP4387905B2 (en) 2004-09-17 2004-09-17 Semiconductor optical sensor device and information equipment incorporating the same
US11/215,229 US7214922B2 (en) 2004-09-17 2005-08-31 Semiconductor photosensor device and information apparatus with sensitivity region for wide dynamic range
US11/695,645 US7696467B2 (en) 2004-09-17 2007-04-03 Semiconductor photosensor device with sensitivity region for wide dynamic range and information apparatus

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US8514165B2 (en) 2006-12-28 2013-08-20 Semiconductor Energy Laboratory Co., Ltd. Semiconductor device
JP2009258219A (en) * 2008-04-14 2009-11-05 Denso Corp Display
JP5445076B2 (en) * 2009-11-27 2014-03-19 株式会社ニコン Imaging device
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