KR100906958B1 - Method for converting signal by ADCanalogue-digital converter, and Method for measuring light intensity using it or the method, and ambient light sensor - Google Patents

Abstract

Disclosed are a signal conversion method of an ADC, an illuminance measuring method and an illuminance sensor using the same. A signal conversion method for converting a sensed current into a digital signal, comprising: (a) generating a current corresponding to the sensed current using a current mirror circuit; (b) charging the capacitor using the generated current; (c) discharging the capacitor when the voltage of the capacitor becomes a reference voltage (V _R ); And (d) repeating steps (a) to (c) for a reference time (P _R ) to count the number of discharges of the capacitor. Presented. According to an embodiment of the present invention, by presenting a simple structure of the ADC can reduce the chip area and increase the response speed.

ADC, Current Mirror Circuit, Ambient Light Sensor

Description

Method for converting signal by analogue-digital converter (ADC), and Method for measuring light intensity using it or the method, and ambient light sensor}

1 is a block diagram of an illumination sensor according to a first embodiment of the present invention;

2 is a block diagram of an illumination sensor according to a second embodiment of the present invention;

3 is a schematic flowchart illustrating a method of measuring illuminance according to a first embodiment of the present invention;

4 is a circuit diagram of an illuminance sensor according to a first embodiment of the present invention.

5 is a digital circuit diagram of an illuminance sensor according to a first embodiment of the present invention.

6 is a circuit diagram of an illuminance sensor according to a second embodiment of the present invention.

7 is a circuit diagram of an illuminance sensor according to a third embodiment of the present invention.

8 is a graph showing the relationship between the number of resets of the capacitors and the intensity of illuminance of the first current mirror circuit according to the second embodiment of the present invention;

9 is a graph showing the relationship between the number of resets of the capacitors and the intensity of illuminance of the second current mirror circuit according to the second embodiment of the present invention.

<Description of Main Numbers and Symbols in Drawings>

100: optical detector unit 110: analog circuit unit

130: digital circuit portion 112: first current mirror circuit

114: first capacitor 122: second current mirror circuit

124: second capacitor 400: photodiode

V _R : reference voltage T _R : reference transistor

I _R : current flowing through the photodiode T ₁ : first transistor

T ₂ : second transistor P _R : reference time

C ₁ : first capacitor C ₂ : second capacitor

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of measuring illuminance and an illuminance sensor, and more particularly, to an illuminance measuring method and illuminance sensor in which the structure of an analog-digital converter (ADC, hereinafter abbreviated as 'ADC') is changed. will be.

The sensor refers to a device that acts as a sensory organ of a human, and an optical sensor corresponds to time. It is also called a visual sensor. The optical sensor can be divided into various types according to the use purpose or the kind of wavelength of light. In particular, a sensor for detecting visible light among light sensors is called an illuminance sensor.

In detail, the illuminance sensor is a device that detects the intensity of the ambient light and outputs the degree thereof as an electrical signal. In particular, it operates only in the visible light area, which is visible to humans, and is widely used for automatic adjustment of lighting equipment according to ambient brightness, automatic brightness adjustment of display products, and day and night switching of surveillance cameras.

The illuminance sensor can be divided into three parts: an optical detector, an analog circuit, and a digital circuit.

The light detector is a part that senses light, and a photodiode type is generally used. The photodiode is a kind of device that converts light energy into electrical energy. The photodiode converts light energy into electrical energy to perform a light detection function.

In the photodiode, the optical signal is converted into a current signal, and the converted current signal is converted into a digital value in the ADC circuit. The digital circuit portion transmits the converted digital value as the interface portion.

ADCs are devices that convert analog signals to digital values.These types include ADCs, successive approximation ADCs, parallel ADCs, and integrated ADCs. have.

The coefficient comparison ADC compares the voltage generated by the internal D / A converter until it is larger than the analog input. The circuit is relatively simple, but the conversion time is long and it depends on the size of the input signal. If the input signal is full scale, the conversion time is the longest and requires a clock period.

A successive approximation ADC (ADC) is a method that can be modified from the most significant bit to the least significant bit using a successive approximation register (SAR). Its relatively fast conversion time and simple circuit make it the most widely used low cost, high resolution, general purpose ADC.

Parallel comparable ADCs (flash ADCs) compare analog input signals with multiple resistors and compare them with each comparator, so the comparison is completed in one step, resulting in very fast conversion times. However, the high resolution has the disadvantage that the number of resistor circuits and comparators is so large that the circuit is complicated and expensive. This method is used for applications that are expensive but require very fast throughput.

Integrating ADC (Integrating ADC) is a method of measuring the time by integrating the analog input signal for a certain time, reset the counter, and then integrate the reference voltage until the output of the integrator becomes zero. This method integrates the analog input signal for a certain period of time, and thus has a stable conversion characteristic against noise of the input signal, but has a disadvantage in that the conversion time is slow due to two integration times. Therefore, this method is often used in low speed systems.

Conventionally, the ADC type used for the illuminance sensor was an integrated ADC type among the above-mentioned ADCs. Integral ADC type compares in comparator until it reaches the reference voltage and counts the number of clocks and converts them into digital value.

However, in the conventional integrated ADC, in order to maintain the value for 100 ms, which is a common minimum period of the illumination sensor, as the conversion time increases, the resistance value and the capacitor value increase, and the chip area increases. Therefore, in order to reduce the chip area, a high sheet resistance layer is required, and even if a high sheet resistance layer is used, the process error is large.

In addition, the integrated ADC has a slow conversion time due to two integration times. For example, the conversion time of 100ms (integrating time 100ms + deintegrating time 100ms + auto zero time 200ms) = 400ms takes a disadvantage that the operating speed is slow.

The present invention proposes a signal conversion method of the ADC, the illumination measurement method and the illumination sensor using the same to change the structure of the ADC to solve the above problems.

In addition, the present invention has a disadvantage in that the area of the chip is increased because the capacitor value is too large in the case of using the existing integrated ADC, the ADC of the ADC that can reduce the chip area by presenting a simple structure of the ADC instead of the integrated ADC We present a signal conversion method, an illuminance measurement method, and an illuminance sensor using the same.

In addition, the present invention provides a signal conversion method of the ADC to increase the response speed by presenting a simple structure of the ADC instead of the integral ADC in order to overcome the disadvantage that the response speed is slow when using the conventional integrated ADC; An illuminance measuring method and an illuminance sensor using the same are presented.

Technical problems presented by the present invention will be easily understood through the following description.

According to one aspect of the invention, there is provided a signal conversion method of the ADC.

According to a preferred embodiment of the present invention, in a signal conversion method for converting a sensed current into a digital signal, (a) generating a current corresponding to the sensed current using a current mirror circuit; ; (b) charging the capacitor using the generated current; (c) discharging the capacitor when the voltage of the capacitor becomes a reference voltage (V _R ); And (d) repeating steps (a) to (c) for a reference time (P _R ) to count the number of discharges of the capacitor.

In addition, a signal conversion method is provided in which the reference time P _R of step (d) is 100 ms.

In addition, a signal conversion method is provided in which the current value is a current value sensed by the optical element.

In addition, the optical device is a signal conversion method of any one of a photoelectric tube, a photoelectric cell, a photovoltaic cell, a photodiode and a photo transistor. Is provided.

In addition, the current mirror circuit is provided with a plurality of signal conversion method.

In addition, the plurality of current mirror circuits are provided with a signal conversion method having transistors having different areas.

In addition, the number of the current mirror circuits is two, and the first current mirror circuit has a 1: 1 current in which the transistor T ₁ W (width) / L (length) is equal to the W / L of the reference transistor T _R. A mirror circuit, and the second current mirror circuit is provided with a signal conversion method wherein the transistor T ₂ W / L is an N: 1 current mirror circuit in which 1 / N times the W / L of the reference transistor T _R.

In addition, the second current mirror circuit is provided with a signal conversion method in which the transistor T ₂ W / L is a 32: 1 current mirror circuit in which 1/3 W times L / W of the reference transistor T _R.

In addition, the step (c) is provided with a signal conversion method characterized in that it is determined whether the voltage of the capacitor is a reference voltage (V _R ) in the comparator connected to the capacitor.

According to another aspect of the present invention, a method of measuring illuminance of an illuminance sensor is provided.

According to a preferred embodiment of the present invention, there is provided a method of measuring illuminance, comprising: (a) generating a current by converting a sensed light into electrical energy; (b) generating a current corresponding to the generated current using a current mirror circuit; (c) charging the capacitor using the generated current; (d) discharging the capacitor when the voltage of the capacitor becomes a reference voltage (V _R ); And (e) repeating steps (b) to (d) for a reference time (P _R ) to count the number of discharges of the capacitor; And (f) measuring the illuminance of the sensed light using the number of discharges of the counted capacitor.

In addition, the illumination time measurement method using the signal conversion method of the reference time (P _R ) of the step (d) is 100ms is provided.

In addition, there is provided a method of measuring illuminance using a signal conversion method wherein the current value is a current value sensed by an optical element.

In addition, the optical device is a signal conversion method of any one of a photoelectric tube, a photoelectric cell, a photovoltaic cell, a photodiode and a photo transistor. The illuminance measuring method used is provided.

In addition, the current mirror circuit is provided with a method of measuring illuminance using a plurality of signal conversion methods.

In addition, the plurality of current mirror circuits are provided with an illuminance measuring method using a signal conversion method having transistors having different areas.

The number of the current mirror circuits is two, and the first current mirror circuit is a 1: 1 current mirror circuit in which the transistor T ₁ W / L is the same as the W / L of the reference transistor T _R , and the second current mirror circuit is the second current mirror circuit. The current mirror circuit is provided with an illuminance measuring method using a signal conversion method in which the transistor T ₂ W / L is an N: 1 current mirror circuit having 1 / N times the W / L of the reference transistor T _R.

In addition, the second current mirror circuit is an illuminance measuring method using a signal conversion method, which is a 32: 1 current mirror circuit in which the transistor T ₂ W / L is 1/32 times the W / L of the reference transistor T _R. do.

Also, in the step (c), it is determined whether the voltage of the capacitor is a reference voltage V _R in the comparator connected to the capacitor, and the illuminance measuring method using the signal conversion method is provided.

According to another aspect of the present invention, an ADC for converting an analog signal into a digital signal is provided.

According to a preferred embodiment of the present invention, in an analog-digital converter (ADC) for converting a sensed current into a digital signal, a current corresponding to the sensed current is generated using a current mirror phenomenon. A current mirror circuit; Coupled to the current mirror circuit, a reference voltage (V _R) filled and discharged of the charge while the charge is being charged until, is discharged when the reference voltage (V _R), the reference time (P _R) A capacitor to repeat; And a digital circuit unit for counting the number of times the charging and discharging of the capacitor is repeated.

In addition, an ADC is provided that is connected to the capacitor and further comprises a comparator for determining whether the voltage of the capacitor is a reference voltage (V _R ).

In addition, the current mirror circuit is provided with a plurality of ADC.

In addition, the plurality of current mirror circuits are provided with an ADC having transistors having different areas.

The number of the current mirror circuits is two, and the first current mirror circuit is a 1: 1 current mirror circuit in which the transistor T ₁ W / L is the same as the W / L of the reference transistor T _R , and the second current mirror circuit is the second current mirror circuit. The current mirror circuit is provided with an ADC which is an N: 1 current mirror circuit in which the transistor T ₂ W / L is 1 / N times the W / L of the reference transistor T _R.

In addition, the second current mirror circuit is provided with an ADC which is a 32: 1 current mirror circuit in which the transistor T ₂ W / L is 1/32 times the W / L of the reference transistor T _R.

According to another aspect of the invention, an illuminance sensor is provided.

According to a preferred embodiment of the present invention, an optical device for converting light energy into electrical energy; A current mirror circuit in which a current corresponding to a current flowing in the optical device is generated using a current mirror phenomenon; Coupled to the current mirror circuit, and the electrical charge until the reference voltage (V _R) is charged, and discharge when the reference voltage (V _R), based on repetition of charge and discharge of the electric charges during the time (P _R) A capacitor to perform; And a digital circuit unit that counts the number of times the charging and discharging of the capacitor is repeated.

In addition, the optical device is provided with an illumination sensor, which is any one of a photoelectric tube, a photoelectric cell, a photovoltaic cell, a photodiode, and a phototransistor.

In addition, there is provided an illuminance sensor connected to the capacitor, further comprising a comparator for determining whether the voltage of the capacitor is a reference voltage (V _R ).

In addition, the current mirror circuit is provided with a plurality of illuminance sensors.

In addition, the plurality of current mirror circuits are provided with an illuminance sensor having transistors having different W / L.

The number of the current mirror circuits is two, and the first current mirror circuit is a 1: 1 current mirror circuit in which the transistor T ₁ W / L is the same as the W / L of the reference transistor T _R , and the second current mirror circuit is the second current mirror circuit. The current mirror circuit is provided with an illuminance sensor in which the transistor T ₂ W / L is an N: 1 current mirror circuit with 1 / N times the W / L of the reference transistor T _R.

In addition, the second current mirror circuit is provided with an illuminance sensor which is a 32: 1 current mirror circuit in which the transistor T ₂ W / L is 1/32 times the W / L of the reference transistor T _R.

According to another aspect of the present invention, there is provided a recording medium having recorded thereon a program for measuring roughness.

According to a preferred embodiment of the present invention, there is provided an apparatus comprising: instructions of instructions executable by a digital processing apparatus to implement a method of illuminance measurement; A recording medium on which a program is tangibly embodied, the program being readable by the digital processing apparatus, comprising: (a) generating a current by converting the sensed light into electrical energy; (b) generating a current corresponding to the generated current using a current mirror circuit; (c) charging the capacitor using the generated current; (d) discharging the capacitor when the voltage of the capacitor becomes a reference voltage (V _R ); (e) repeating steps (b) to (d) for a reference time (P _R ) to count the number of discharges of the capacitor; And (f) measuring the illuminance of the sensed light by using the number of discharges of the counted capacitor. The recording medium is provided with a program for implementing the illuminance measuring method.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Terms including ordinal numbers such as first and second may be used to describe various components, but the components are not limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as the second component, and similarly, the second component may also be referred to as the first component. The term and / or includes a combination of a plurality of related items or any item of a plurality of related items.

When a component is referred to as being "connected" or "connected" to another component, it may be directly connected to or connected to that other component, but it may be understood that other components may be present in between. Should be. On the other hand, when a component is said to be "directly connected" or "directly connected" to another component, it should be understood that there is no other component in between.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

In addition, in the description with reference to the accompanying drawings, the same components regardless of reference numerals will be given the same reference numerals and duplicate description thereof will be omitted. In the following description of the present invention, if it is determined that the detailed description of the related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

1 is a block diagram of an illumination sensor according to a first embodiment of the present invention.

Referring to FIG. 1, an illuminance sensor includes an analog circuit unit including an optical detector unit 100, a current mirror circuit 112, a capacitor 114, and a comparator 116. 110, the digital circuit unit 130.

The light detector unit 100 is a part that senses light and generally uses a photodiode. The photodiode is a semiconductor PN junction element whose operating region is limited to the reverse bias region. The reverse saturation current of the photodiode is usually limited to a few amperes because it is caused by a thermally generated minority carrier, but when light is applied to the junction, the minority carrier increases due to the light energy, increasing the current.

Photodiode has the disadvantage of low light sensitivity compared to phototransistor, but has good linearity of incident light quantity and output current, fast response speed, low output dispersion and low output fluctuation due to changes in ambient temperature. There is such an advantage.

In the present invention, the above-described photodiode is used as an optical detector for convenience of description, but any optical device having a function of sensing current by detecting light may be used.

For example, it may be a photoelectric tube, a photoelectric cell, a photovoltaic cell, a photo diode, a photo transistor, or the like.

The construction and function of each optical element is apparent to those skilled in the art, and the optical element used in the present invention is not limited to those listed above.

The analog circuit unit 110 includes a current mirror circuit 112, a capacitor 114, and a comparator 116.

In the present invention, the current mirror circuit 112 is defined as a circuit using the current mirror phenomenon, the current mirror circuit 112 is configured using a photodiode and a MOS transistor.

Current mirror phenomenon means that when the source / drain voltage of the driving transistor and the source / drain voltage of the driving transistor are close to each other, the value of the current flowing through both transistors is equal to the width / length of the two transistors. It means a phenomenon having a proportionality with L). This will be described in detail with reference to the circuit diagrams of FIGS. 4 to 7.

The capacitor 114 is a structure in which two conductor plates face each other with an insulating material in the middle. In the present invention, the current by the grape diode flows equally through the current mirror circuit 112, and charge is charged in the capacitor 114 connected to the current mirror circuit 112.

Comparator 116 is an operational amplifier in which one of two states appears at the output when the relationship between the two input voltages is large or small. The comparator 116 functions to determine whether the voltage of the capacitor 114 is a preset voltage (hereinafter referred to as a reference voltage V _R ).

The digital circuit unit 130 serves as an interface part to transmit a value obtained by converting an analog signal into a digital signal value.

The schematic flow of the present invention is as follows.

The current flows in the current mirror circuit 112 corresponding to the current sensed by the optical detector unit 100, and the current flowing in the current mirror circuit 112 charges the capacitor 114 coupled with the current mirror circuit 112.

The current flowing through the current mirror circuit 112 charges the capacitor 114 until the voltage of the capacitor 114 becomes the reference voltage V _R. The comparator 116 determines whether the voltage of the capacitor 114 has become the reference voltage V _R. When the voltage of the capacitor 114 reaches the reference voltage V _R , the capacitor 114 is discharged momentarily. The charging and discharging of the capacitor 114 are repeated for a predetermined time (hereinafter referred to as 'reference time P _R ').

The digital circuit unit 130 counts the number of times the capacitor 114 repeats charging and discharging, that is, the number of resets of the capacitor, and transmits the value in which the analog signal is converted into a digital signal value.

Here, the number of resets of the capacitor is the same as the number of times the capacitor is discharged due to the reset signal is applied to the circuit, so "reset number" and "discharge number" are used in the same sense.

The present invention provides an illuminance measuring method and an illuminance sensor using a method of converting a current flowing in the optical detector unit 100 into a digital signal by the above-described method.

2 is a block diagram of an illumination sensor according to a second embodiment of the present invention.

Referring to FIG. 2, the block diagram of FIG. 1 is slightly modified to include two current mirror circuits.

That is, the optical detector unit 100, the first current mirror circuit 112, the first capacitor 114, the first comparator 116, the second current mirror circuit 122, the second capacitor 124, the second An analog circuit unit 120 and a digital circuit unit 130 including a comparator 126 are included.

FIG. 2 is a block diagram of a case in which two current mirror circuits 112 and 122 are included. Here, the same current as that flowing through the photodiode flows in the first current mirror circuit 112, but the second current mirror circuit ( 122), a current different from the current flowing in the photodiode flows. It will be apparent to those skilled in the art that the ratio of the current flowing through the current mirror circuits 112 and 122 can be adjusted by the area ratio of the transistor.

A schematic flow of a second embodiment of the present invention including two current mirrors is as follows.

The current flows through the current mirror circuits 112 and 122 corresponding to the current sensed by the optical detector unit 100, and the current flowing through the current mirror circuits 112 and 122 corresponds to the current mirror circuit 112, respectively. Each capacitor 114, 124 associated with 122 is charged.

The current flowing through each of the current mirror circuits 112 and 122 is equal to the ratio of W / L of the transistors included in the current mirror circuits 112 and 122, and different currents flow in correspondence to the W / L ratio of the transistors. do.

In the present invention, the W / L of the transistor included in the second current mirror circuit 122 is configured to be 1 / N times, and 1 / N is applied to the second current mirror circuit 122 in correspondence with the current flowing through the optical detector unit 100. N times the current was configured to flow.

The current flowing through the current mirror circuits 112 and 122 charges the respective capacitors 114 and 124 until the voltage of the capacitors 114 and 124 becomes the reference voltage V _R. Each comparator 116 determines whether the voltage of the capacitors 114 and 124 has become the reference voltage V _R. When the voltage of each capacitor 114, 124 reaches the reference voltage V _R , each capacitor 114, 124 is instantaneously discharged. The charging and discharging of the capacitors 114 and 124 are repeated during the reference time P _R.

The number of resets of each current mirror circuit 112 and 122 is stored in a register at the same time. Through the predetermined logic, the illuminance value of the first current mirror circuit 112 is output at low illumination, and at high illumination. The illuminance value of the second current mirror circuit 122 is output.

The reason for including two current mirror circuits 112 and 122 unlike in FIG. 1 is that when the strong light is irradiated, the number of reset increases, so that an error may occur. to be.

For example, if the clock cycle of the reset signal is 30ns, the switch must be closed for 30ns to discharge all the charge in the capacitor. If you want to measure 65536Lux, you have to reset 65536 times. In this case, 30ns * 65536 = 1966080ns (about 2ms) and reset loss occurs. Repeated charging and discharging 65536 times will also increase power consumption.

Therefore, by using the plurality of current mirror circuits 112 and 122, the illuminance value of the first current mirror circuit 112 is output at low illuminance, and the illuminance value of the second current mirror circuit 122 is output at high illuminance. The error of illuminance measurement can be reduced.

For this reason, it is apparent to those skilled in the art that a plurality of current mirror circuits 112 and 122 may be used. This will be described in detail with reference to FIGS. 8 and 9.

3 is a schematic flowchart illustrating a method of measuring illuminance according to a first embodiment of the present invention.

Referring to Figure 3, the present invention is disclosed from the PN junction of the photodiode is exposed to light to generate a reverse current (S300).

Current generated in the photodiode is equally flowed to the current mirror circuit 112 by using the current mirror phenomenon. Current flowing in the current mirror circuit 112 charges the capacitor 114 coupled with the current mirror circuit 112. As the capacitor 114 is charged, the voltage of the capacitor 114 is increased, and the charge is charged to the capacitor 114 until the voltage of the capacitor 114 becomes the reference voltage V _R (S302).

The comparator 116 determines whether the voltage of the capacitor 114 has become the reference voltage V _R. That is, the comparator 116 compares the voltage of the capacitor 114 with the reference voltage V _R and outputs a lower voltage, so that the capacitor 114 is output when the reference voltage V _R is output from the comparator 116. It can be determined that the voltage of) has reached the reference voltage V _R. When the voltage of the capacitor 114 does not reach the reference voltage V _R , the charge is charged in the capacitor 114, and when the reference voltage V _R is reached, a reset signal is applied to the circuit (S304). .

When the voltage of the capacitor 114 reaches the reference voltage V _R and a reset signal is applied to the circuit, the capacitor 114 is discharged momentarily (S306).

The charging and discharging of the capacitor 114 are repeated for the reference time P _R. Here, the reference time P _R may be determined according to the frequency of light.

For example, assume that the frequency of the fluorescent lamp is 50 Hz or 60 Hz. i) If the frequency is 50Hz, it means that it oscillates 50 times for 1 second (1000ms / 50 = 20ms), which means that it oscillates at a 20ms period. ii) If the frequency is 60Hz, it means that it vibrates 60 times for 1 second (1000ms / 60 = 16.6ms), which means that it vibrates every 16.6ms. Therefore, if you find the minimum integer period of two cycles, it is 100ms.

Thus, the capacitor 114 repeats charging and discharging until the predetermined reference time P _R is reached (S308).

When the reference time P _R is reached, the analog signal is converted into a digital value through the number of times the capacitor 114 repeats charging and discharging, that is, the number of discharges of the capacitor 114 (S310).

4 is a circuit diagram of an illuminance sensor according to a first embodiment of the present invention. Typically, all transistors used in the circuit of the present invention are composed of MOS transistors, and diodes will be described using photodiodes.

4 illustrates a first current mirror circuit 112 connected to the photodiode 400 and the photodiode 400, a first capacitor C ₁ connected to the first current mirror circuit 112, and a comparator 116. Include.

The first current mirror circuit 112 includes a reference transistor T _R and a first transistor T ₁ , but for convenience of description, the first current mirror circuit 112 includes a reference transistor T. A stage including the first transistor T ₁ excluding _R ) is referred to. Here, the W / Ls of the reference transistor T _R and the first transistor T ₁ are the same.

When light is irradiated to the circuit of FIG. 4, the photodiode 400 senses light and flows a current I _{R in} the reverse direction. The current generated in the photodiode 400 causes the same current I _R to flow in the first current mirror circuit 112 including the first transistor T ₁ having the same W / L as the reference transistor T _R. .

The capacitor connected to the first current mirror circuit (112) (C _1), the reference voltage (V _R) and to charge the electric charges until the first capacitor (C ₁₎ the reference voltage (V _R) voltage via the comparator It can be determined whether or not reached.

When the reference voltage V _R is reached, a reset signal is applied to the circuit, and the first capacitor C ₁ repeatedly performs charging and discharging. The present invention converts the analog current value flowing through the photodiode 400 into a digital value by counting the number of discharges of the first capacitor C ₁ .

5 is a block diagram illustrating a digital circuit of the illuminance sensor according to the first embodiment of the present invention. An external circuit having a reference voltage (V _R ) is provided separately. The circuit maintains a voltage of 1.2 V and is composed of a circuit less affected by temperature or driving voltage.

When the capacitor starts to charge and reaches the reference voltage V _R , the comparator 116 emits a signal while comparing the voltage of the capacitor with the reference voltage V _R. The control logic 500 analyzes the signal received by the comparator 116 and sends a signal to reset the capacitor. At the same time, the counter 510 counts the number of resets.

6 is a circuit diagram of an illuminance sensor according to a second embodiment of the present invention.

Referring to FIG. 6, the circuit diagram of FIG. 4 further includes a second current mirror circuit 122, wherein the first current mirror circuit 112 and the second current mirror circuit 122 connected to the photodiode 400 and the photodiode are connected. ), A first capacitor C ₁ connected to the first current mirror circuit 112, a second capacitor C ₂ connected to the second current mirror circuit 122, and a comparator 116 connected to each capacitor. .

The second current mirror circuit 122 includes a reference transistor T _R and a second transistor T ₂ , but for convenience of description, the second current mirror circuit 122 includes a reference transistor T. A stage including the second transistor T ₂ excluding _R ) is referred to. Here, unlike the first current mirror circuit 112, the areas of the reference transistor T _R and the second transistor T ₂ are different.

In FIG. 6, it is assumed that the area of the first transistor T ₁ is equal to A when the area of the reference transistor T _R is A, and the area of the second transistor T ₂ is A / 32. The circuit diagram of FIG. 6 will be described.

The flow of the circuit occurring in the first current mirror circuit 112 is as described above with reference to FIG. 4, and only the differences caused by the second current mirror circuit 122 are included in FIG. 5. The operation principle of the second current mirror circuit 122 is the same as that of the first current mirror circuit 112, but since the area of the second transistor T ₂ included in the second current mirror circuit 122 is A / 32, In the second current mirror circuit 122, a current of 1/32 times the current I _R flowing through the photodiode flows.

Therefore, when the same number of resets as in the first current mirror circuit 112 is assumed, the value output from the first current mirror circuit 122 is converted into a value 32 times higher. This will be described in detail with reference to FIGS. 8 and 9.

7 is a circuit diagram of an illuminance sensor according to a third embodiment of the present invention. Referring to FIG. 7, a plurality of current mirror circuits are included in the circuit diagram of FIG. 4 and include a first current mirror circuit 112 and a second current mirror circuit 122 connected to the photodiode 400 and the photodiode. Nth current mirror circuit 600, a first capacitor C ₁ connected to the first current mirror circuit 112, and a second capacitor C ₂ and an N current mirror circuit connected to the second current mirror circuit 122. N th capacitor C _N connected to 700, and a comparator 116 connected to each capacitor.

 Here, the W / L of the transistors included in each current mirror circuit may be the same or different, and the operation principle of each current mirror circuit is the same as that of FIGS. 4 to 6. Application of the above-described operating principle to a circuit including a plurality of current mirror circuits is obvious to those skilled in the art, and thus can be easily implemented.

8 is a graph showing a relationship between the number of times of reset of a capacitor and an intensity of illuminance of a first current mirror circuit according to a second embodiment of the present invention.

Referring to FIG. 8, the brightness 810 when the number of resets of the first capacitor C ₁ occurring in the first current mirror circuit 112 is 1, the brightness 820 when the number of resets is 2, and the number of resets are The luminance 830 in the case of 3 and the luminance 840 in the case of 2048 are shown.

That is, when the number of resets is 1, a luminance value indicating the intensity of 1Lux is output, and when the number of resets is 2, the first capacitor C ₁ repeats two charges and discharges, thereby indicating the intensity of 2Lux. Is output. This is because the degree of charge of the first capacitor C ₁ varies according to the light intensity, and the ratio is proportional to the slope of each graph of FIG. 8.

9 is a graph showing a relationship between the number of times of reset of a capacitor and an intensity of illuminance of a second current mirror circuit according to a second embodiment of the present invention.

9, the luminance 910 when the number of resets of the second capacitor C ₂ occurring in the second current mirror circuit 122 is 1, the luminance 920 when the number of resets is 2, and the number of resets are The luminance 930 in the case of 3 and the luminance 940 in the case where the reset frequency is 2049 can be seen.

Since the second current mirror circuit 122 uses a transistor T ₂ having a W / L 1/32 times larger than that of the first current mirror circuit 112, the second current mirror circuit 122 uses 1/32 of the current value flowing through the photodiode 400. Current will flow. Therefore, because it charges the capacitor with a current of I _R / 32, the first to charge the capacitor with a current I _R from the current mirror circuit 112, if the brightness value when the 1Lux reset is once caused, I _R / of 32 weak When the reset occurs by charging the capacitor with a current value, the conversion value is 32 Lux.

The reason for using a plurality of current mirror circuits is a method for reducing the number of resets when measuring high illuminance because the number of resets increases when there is strong light. Therefore, the illuminance value of the first current mirror circuit 112 is output at low illuminance, and the illuminance value of the second current mirror circuit 122 is output at high illuminance, thereby reducing errors and power consumption of illuminance measurement.

In this case, a plurality of reset times are simultaneously stored in the plurality of current mirror circuits, and through the predetermined logic, the illuminance value of the first current mirror circuit 112 is output at low illuminance, and the second current mirror circuit at high illuminance. The illuminance value of 122 is outputted.

The present invention is not limited to the above embodiments, and many variations are possible by those skilled in the art within the spirit of the present invention.

As described above, the ADC signal conversion method, the illumination measurement method and the illumination sensor using the same according to the present invention can reduce the chip area by presenting an ADC having a simple structure instead of the conventional integrated ADC.

In addition, the signal conversion method of the ADC according to the present invention, the illuminance measuring method and the illuminance sensor using the same can increase the response speed by presenting a simple structure ADC instead of the conventional integrated ADC.

Although the above has been described with reference to embodiments of the present invention, those skilled in the art may vary the present invention without departing from the spirit and scope of the present invention and equivalents thereof described in the following claims. It will be understood that modifications and changes can be made.

Claims (19)

In the signal conversion method for converting the sensed current to a digital signal, (a) generating a current corresponding to the sensed current using a plurality of current mirror circuits each having transistors of different areas; (b) charging each capacitor connected to the current mirror circuit using each generated current; (c) discharging the capacitor when the voltage of the capacitor becomes a reference voltage (V _R ); And (d) repeating steps (a) to (c) for a reference time P _R to count the number of discharges of the capacitor. The method of claim 1, The reference time (P _R ) in the step (d) is 100ms signal conversion method. The method of claim 1, And the sensed current in step (a) is a current sensed by the optical device. The method of claim 3, wherein The optical device is one of a photoelectric tube, a photoelectric cell, a photovoltaic cell, a photodiode and a phototransistor. delete delete The method of claim 1, The number of the current mirror circuits is two, the first current mirror circuit is a 1: 1 current mirror circuit in which the area of the transistor T1 is equal to the area of the reference transistor TR, and the second current mirror circuit is a transistor T2. The area is an N: 1 current mirror circuit having an area 1 / N times the area of the reference transistor TR, And N is a real number greater than one. The method of claim 7, wherein And said second current mirror circuit is a 32: 1 current mirror circuit having a transistor (T ₂ ) area 1/32 times the area of a reference transistor (T _R ). The method of claim 1, In the step (c), it is determined whether the voltage of the capacitor is a reference voltage (V _R ) in a comparator connected to the capacitor. In the method of measuring illuminance, (a) converting the sensed light into electrical energy to generate a current; (b) generating a current corresponding to the generated current using a plurality of current mirror circuits, each having a transistor having a different area; (c) charging each capacitor connected with the current mirror circuit using each generated current; (d) discharging the capacitor when the voltage of the capacitor becomes a reference voltage (V _R ); And (e) repeating steps (b) to (d) for a reference time (P _R ) to count the number of discharges of the capacitor; And (f) measuring illuminance of the sensed light using the number of discharges of the counted capacitor. In an analog-digital converter (ADC) that converts a sensed current into a digital signal, A plurality of current mirror circuits each using a current mirror phenomenon to generate a current corresponding to the sensed current and each having a transistor having a different area; Coupled to the current mirror circuit, and the electrical charge until the reference voltage (V _R) is charged, and discharge when the reference voltage (V _R), based on repetition of charge and discharge of the electric charges during the time (P _R) A capacitor to perform; And And a digital circuit unit for counting the number of times the charging and discharging of the capacitor is repeated. The method of claim 11, And a comparator coupled to the capacitor and determining whether the voltage of the capacitor is a reference voltage (V _R ). delete delete The method of claim 11, The number of the current mirror circuits is two, the first current mirror circuit is a 1: 1 current mirror circuit in which the area of the transistor T1 is equal to the area of the reference transistor TR, and the second current mirror circuit is a transistor T2. The area is an N: 1 current mirror circuit having an area 1 / N times the area of the reference transistor TR, N is a real number greater than one. The method of claim 15, And said second current mirror circuit is a 32: 1 current mirror circuit having a transistor (T ₂ ) area 1/32 times the area of a reference transistor (T _R ). An optical element for converting light energy into electrical energy; A plurality of current mirror circuits each having a transistor having a different area and generating a current corresponding to a current flowing in the optical device by using a current mirror phenomenon; Coupled to the current mirror circuit, and the electrical charge until the reference voltage (V _R) is charged, and discharge when the reference voltage (V _R), based on repetition of charge and discharge of the electric charges during the time (P _R) A capacitor to perform; And And a digital circuit unit for counting the number of times the charging and discharging of the capacitor is repeated. The method of claim 17, The optical device is an illumination sensor of any one of a photoelectric tube, a photoelectric cell, a photovoltaic cell, a photodiode, and a phototransistor. Of instructions that may be executed by the digital processing device such that the illuminance measuring method is implemented; In a recording medium in which a program is tangibly embodied, and in which a program which can be read by the digital processing apparatus is recorded, (a) converting the sensed light into electrical energy to generate a current; (b) generating a current corresponding to the generated current using a plurality of current mirror circuits, each having a transistor having a different area; (c) charging each capacitor connected with the current mirror circuit using each generated current; (d) discharging the capacitor when the voltage of the capacitor becomes a reference voltage (V _R ); (e) repeating steps (b) to (d) for a reference time (P _R ) to count the number of discharges of the capacitor; And and recording a program for implementing the illuminance measuring method, the method comprising measuring the illuminance of the sensed light using the number of discharges of the counted capacitor.

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