KR102098700B1 - Photo sensing device with having improved dynamic range and noise resistant property - Google Patents

Abstract

Disclosed is a photo sensing device having an improved dynamic range and noise characteristics. According to the present invention, in the photo sensing device, when the energy of the received light is reflected and confirmed as a frequency of an oscillating signal, an amount of currents acts as a significant electrical component. According to the photo sensing device of the present invention, even when a level of a supplied power voltage is low, it is possible to effectively sense the intensity of the received light received. According to the present invention, the photo sensing device has a wide dynamic range. In addition, in the photo sensing device of the present invention, a net current excluding a noise current from a diode current is reflected as the frequency of the oscillating signal. As a result, according to the photo sensing device of the present invention, noise characteristics are greatly improved.

Description

Photo sensing device with improved dynamic range and noise characteristics {PHOTO SENSING DEVICE WITH HAVING IMPROVED DYNAMIC RANGE AND NOISE RESISTANT PROPERTY}

The present invention relates to a photo-sensing device that detects received light, and more particularly, to a photo-sensing device having improved dynamic range and noise characteristics.

The photo sensing device is an electronic circuit device that senses the energy of the received light and generates it as sensing data. Currently, a voltage-level photo-sensing device that converts and uses energy of received light into a signal of a voltage level is widely used.

1 is a view showing a conventional photo sensing device, a voltage level type photo sensing device. The photo sensing device of FIG. 1 includes an optical sensing unit 10, a gain amplifying unit 20, and a data conversion unit 30. The photodiode 11 of the light sensing unit 10 converts the received light LGT into a diode current Ipd. In addition, the diode current Ipd is generated as a sensing signal XSEN by the power storage capacitor 13 and the operational amplifier 15.

At this time, the sensing signal XSEN provided from the operational amplifier 15 has a voltage level reflecting the amount of the diode current Ipd, that is, the received light LGT. The voltage level of the sensing signal XSEN is converted into sensing data DSEN of digital components by the gain amplifying unit 20 and the data converting unit 30. For reference, reference numeral 'VREF' in FIG. 1 represents a reference voltage, and reference numeral 'VNN' represents an externally provided 'diode power voltage'.

However, in the conventional photo-sensing device as shown in FIG. 1, when the power supply voltage VDD provided to the operational amplifier 15 is lowered, the range of voltage levels that the sensing signal XSEN can have is also limited.

As a result, in the photo-sensing device of FIG. 1, a problem that the range of the usable power supply voltage VDD, that is, the dynamic range is narrow occurs.

In addition, the diode current Ipd generated in the photodiode includes a noise current such as a dark current, a current according to ambient light, and a current according to noise. However, in the conventional photo sensing device as shown in FIG. 1, the sensing signal XSEN reflects the diode current Ipd including the noise current.

Therefore, the photo-sensing device of FIG. 1 has the disadvantage of being weak in noise characteristics.

An object of the present invention is to solve the problems of the existing technology, and to provide a photo sensor device having improved dynamic range and noise characteristics.

One aspect of the present invention for achieving the above object relates to a photo sensing device. The photo-sensing device of the present invention outputs output light, but a light source in which a turn-on state in which the output light is output and a turn-off state in which the output of the output light is blocked are controlled are controlled; The anode terminal is a photodiode that is electrically connected to a stable node to generate a diode current, wherein at least a portion of the diode current is the photodiode dependent on the output light output from the light source; A noise removing unit driven to remove the noise current with respect to the diode current, wherein the noise current is a current generated by the photodiode, and is a current generated in a turn-off state of the light source; A sourcing unit sourcing a net current at a spare node, the spare node receiving the net current of the stable node, the net current being the sourcing unit based on the current obtained by removing the noise current from the diode current; And a mirror oscillation driven to generate a mirroring current group by mirroring the net current sourced from the sourcing unit in the turn-on state of the light source, and to generate an oscillating signal having a frequency according to the current amount of the mirroring current group. It has a rating unit.

In the photo-sensing device of the present invention having the above-described configuration, when the energy of the received light is reflected and confirmed as the frequency of the oscillating signal, the amount of current acts as a significant electrical component. According to the photo-sensing device of the present invention, even when the level of the supplied power voltage is low, it is possible to effectively sense the intensity of the received light received. That is, the photo sensing device of the present invention has a wide dynamic range.

In addition, in the photo sensing device of the present invention, the net current excluding the noise current from the diode current is reflected as the frequency of the oscillating signal. As a result, according to the photo-sensing device of the present invention, noise characteristics are greatly improved.

A brief description of each figure used in the present invention is provided.
1 is a view for explaining a conventional photo sensing device.
2 is a view showing a photo sensing device according to an embodiment of the present invention.
3A is a view showing an example of a mirror oscillating unit of FIG. 2.
3B is a view showing another example of the mirror oscillating part of FIG. 2.
4 is a view for explaining a turn-on state and a turn-off state of the light source and switches of FIG. 2.

In describing the contents of the present invention throughout the specification, the meanings of the terms 'electrically connected', 'connected', and 'connected' between individual components are not only a direct connection, but also a property of a certain degree or more. This includes all connections made through an intermediate medium while being maintained. Terms such as 'transmitted' and 'lead' of each signal include not only the direct meaning but also the indirect meaning through an intermediate medium while maintaining the signal properties to some extent. In addition, terms such as 'applied,' 'applied', and 'input' to which a voltage or signal is applied are also used throughout this specification in the same sense.

Also, a plurality of expressions for each component may be omitted. This is also because, for example, signal lines do not need to be divided into singular and plural in the case of multiple signal lines having the same properties, such as data signals. In this respect, this description is valid. Therefore, similar expressions should be interpreted in the same way throughout the specification.

Meanwhile, in the present specification, the term 'voltage level type photo sensing device' means 'a photo sensing device that converts an amount of current according to received light into voltage and generates sensing data according to the level of the converted voltage.' . And, 'current-type photo sensing device' means 'a photo-sensing device that generates sensing data according to the amount of current according to received light received but does not convert the amount of current into voltage'.

In order to fully understand the present invention and the operational advantages of the present invention and the objects achieved by the practice of the present invention, reference should be made to the accompanying drawings and the contents described in the accompanying drawings, which illustrate preferred embodiments of the present invention. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. Rather, the embodiments introduced herein are provided to ensure that the disclosed contents are thorough and complete and that the spirit of the present invention is sufficiently conveyed to those skilled in the art.

In addition, in understanding each drawing, it should be noted that the same members are shown with the same reference numerals as possible.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a view showing a photo sensing device according to an embodiment of the present invention. 2, the photo sensing device of the present invention is a 'current type photo sensing device', a light source (LSC), a photodiode 100, a noise removing unit 200, a sourcing unit 300, a mirror oscillating unit 500, and preferably, a stabilization unit 400 and a data conversion unit 600 are further provided.

The light source LSC outputs the output light LUT. In addition, the light source LSC controls the turn-on state and the turn-off state in response to the driving signal XDR. Here, in the turn-on state of the light source LSC, the driving signal XDR is activated (see t1 in FIG. 4), and the output light LUT is output. In addition, in the turn-off state of the light source LSC, the driving signal XDR is deactivated (see t2 in FIG. 4), and the output of the output light LUT is cut off.

For reference, the driving signal XDR in the photo sensing device of the present invention is a pulse width modulation signal.

In addition, the output light LUT is transmitted to the subject OBJ, such as transmission, reflection, and the like, and is generated as received light LGT. The photo-sensing device of the present invention can be used to detect the energy of the received light LGT and recognize the pattern of the object OBJ.

The photodiode 100 is formed between a diode power voltage VNN and a stable node NSTV. At this time, the anode terminal of the photodiode 100 is electrically connected to the stable node NSTV. In addition, a cathode terminal of the photodiode 100 is electrically connected to the diode power voltage VNN. The photodiode 100 detects the energy (depending on the light intensity, output time, etc.) of the received light LGT and converts it into at least a part of the diode current Ipd. That is, at least a part of the diode current Ipd is dependent on the output light LUT output from the light source LSC.

On the other hand, in the present specification, the diode current (Ipd) can be understood to be largely composed of a noise current (Ins) and a net current (Inet).

In this case, the noise current Ins refers to a current generated in the photodiode 100 even when the light source LSC is turned off. The noise current Ins may include current due to ambient light, dark current, and current generated by noise, not output light LUT output from the light source LSC. In addition, the net current (Inet) means the current obtained by subtracting the noise current (Ins) from the diode current (Ipd).

Therefore, the current through which the energy of the received received light LGT is converted by the photodiode 100 may be understood as the net current Inet.

In the photo-sensing device of the present invention, the effect of the noise current (Ins) is eliminated as much as possible, and the oscillating signal (XOSC) / sensing data (of the frequency / data value reflecting only the effect of the net current (Inet)) DESN) can be obtained.

As a result, according to the photo sensing device of the present invention, the sensing function is greatly improved.

2, the noise removing unit 200 is driven to remove the noise current Ins with respect to the diode current Ipd.

In addition, the sourcing unit 300 sources the net current Inet at the spare node NPRE. At this time, the spare node NPRE is driven to receive the net current Inet of the stable node NSTV.

Preferably, the sourcing unit 310 includes a source transistor 310. In this case, the source transistor 310 is an NMOS transistor in which a gate terminal and a drain terminal are electrically connected to the spare node, and a source terminal is electrically connected to a ground voltage (VSS).

Specifically, the noise removing unit 200 includes a removal transistor 210, a removal capacitor 220, and a removal switch SWE.

The elimination transistor 210 is an NMOS transistor in which one side junction is electrically connected to the stable node NSTV and the other side junction is electrically connected to a ground voltage VSS.

In the removal capacitor 220, one terminal is electrically connected to the gate terminal of the removal transistor 210, and the other terminal is electrically connected to the ground voltage VSS.

In addition, in the turn-off state of the light source LSC, the removal switch SWE is driven to electrically connect the preliminary node NPRE and the gate terminal of the removal transistor 210.

Accordingly, the removal capacitor 220 accumulates electric charge in the turn-off state of the light source LSC. At this time, the removal capacitor 220 stores an amount of electric charge corresponding to the noise current Ins. As a result, the noise current Ins generated in the turn-off state of the light source LSC flows through the removal transistor 210.

In addition, the removal switch SWE is turned on in the turned-on state of the light source LSC. Even in this case, the noise current Ins still flows through the elimination transistor 210 to the ground voltage VSS.

Accordingly, a net current (Inet) obtained by subtracting the noise current (Ins) from the diode current (Ipd) flows through the source transistor (310) of the sourcing unit (300) connected to the spare node (NPRE).

In other words, the source transistor 310 receives the net current Inet generated in the photodiode 100 through its gate terminal and drain terminal. The current path of the net current Inet generated in the photodiode 100 is formed by the source transistor 310.

On the other hand, the stabilizing unit 400 transmits the net current (Inet) of the stable node (NSTV) to the spare node (NPRE), the stable node (NSTV), that is, the anode terminal of the photodiode 100 It is driven to maintain the voltage at a constant level.

The stabilization unit 400 specifically includes a stabilization transistor 410 and an operational amplifier 420.

The stabilization transistor 410 is one side junction is electrically connected to the anode terminal of the photodiode 100, that is, the stable node (NSTV), the other side junction is the gate terminal of the source transistor 310 and the It is a PMOS transistor electrically connected to a drain terminal.

In addition, the operational amplifier 420 generates an output signal having a level according to a difference in voltage of the anode terminal of the photodiode 100 with respect to a reference voltage VREF, that is, the voltage of the stable node NSTV. In addition, the output signal of the operational amplifier 420 is applied to the gate terminal of the stabilization transistor 410.

By the stabilizing unit 400 having such a configuration, the voltage of the stable node NSTV, that is, the anode terminal of the photodiode 100 is the same as the reference voltage VREF.

Accordingly, the voltage difference between the cathode terminal and the anode terminal of the photodiode 100 is kept constant during the sensing operation. As a result, the magnitude of the diode current Ipd depends on the energy of the received light LGT. That is, the magnitude of the net current Inet more accurately reflects the energy of the received light LGT.

2, the mirror oscillating unit 500 mirrors the net current Inet that is sourced by the sourcing unit 300 in the turn-on state of the light source LSC, thereby mirroring the current group GImr ), And generates an oscillating signal XOSC having a frequency according to the current amount of the mirroring current group GImr.

Preferably, the mirror oscillating unit 500 includes a mirroring unit 510 and an oscillating unit 530, and more preferably, a mirroring switch SWM is further provided.

3A is a view showing an example of the mirror oscillating unit 500. The mirroring unit 510 of FIG. 3A includes a common mirroring transistor TRmt. The common mirroring transistor TRmt includes the gate terminal and the ground voltage VSS connected to the preliminary node NPRE, that is, the gate terminal and the drain terminal of the source transistor 310 in the turned-on state of the light source LSC. ) Is an NMOS transistor having a source terminal electrically connected to the.

At this time, in the turn-on state of the light source LSC, the switch SWM is driven to connect the spare node NPRE to the gate terminal of the common mirroring transistor TRmt.

As a result, the common mirroring current Imtr flowing in the common mirroring transistor TRmt mirrors the net current Inet flowing in the source transistor 310. Here, the common mirroring current Imrt is included in the mirroring current group GImr (see FIG. 2). In addition, the size of the common mirroring current Imtr to the size of the net current Inet depends on the ratio of the width / length of the common mirroring transistor TRmt to the source transistor 310.

The oscillating unit 530 includes first to fifth inverters INV1 to INV5. In addition, each of the first to fifth inverters INV1 to INV5 has its own pull-up transistor TU and pull-down transistor TD. Further, the first to fifth inverters INV1 to INV5 are driven to form an oscillating chain to generate an oscillating signal XOSC.

At this time, one side junction of the pull-down transistor TD of each of the first to fifth inverters INV1 to INV5 commonly receives the common mirroring current Imtr.

According to the mirror oscillating unit 500 having the same configuration as in FIG. 3A, the oscillating signal XOSC is a frequency according to the current amount of the common mirroring current Imtr, that is, the current amount of the mirroring current group GImr. And oscillates.

In other words, the oscillating signal XOSC oscillates with a frequency according to the amount of current of the net current Inet.

Meanwhile, the configuration of the mirror oscillating unit 500 may be modified in various forms.

3B is a view showing another example of the mirror oscillating unit 500. The mirroring unit 510 of FIG. 3B includes first to fifth mirroring transistors TRm1 to TRm5. Each of the first to fifth mirroring transistors TRm1 to TRm5 is in a turn-on state of the light source LSC, a gate connected to the preliminary node NPRE, that is, a gate terminal and a drain terminal of the source transistor 310 An NMOS transistor having a terminal and a source terminal electrically connected to the ground voltage (VSS).

At this time, in the turned-on state of the light source LSC, the switch SWM is driven to connect the spare node NPRE to the gate terminals of the first to fifth mirroring transistors TRm1 to TRm5.

As a result, the first to fifth mirroring currents Imr1 to Imr5 flowing through each of the first to fifth mirroring transistors TRm1 to TRm5 are net currents flowing through the source transistor 310 of the sourcing unit 300 ( Inet). Here, the first to fifth mirroring currents Imr1 to Imr5 are included in the mirroring current group GImr (see FIG. 2). The magnitude of the first to fifth mirroring currents Imr1 to Imr5 relative to the magnitude of the net current Inet is equal to that of the first to fifth mirroring transistors TRm1 to TRm5 relative to the source transistor 310. It depends on the width / length ratio.

The oscillating unit 530 includes first to fifth inverters INV1 to INV5. In addition, each of the first to fifth inverters INV1 to INV5 has its own pull-up transistor TU and pull-down transistor TD. Further, the first to fifth inverters INV1 to INV5 are driven to form an oscillating chain to generate an oscillating signal XOSC.

At this time, one side junction of the pull-down transistor TD of the first to fifth inverters INV1 to INV5 receives the corresponding first to fifth mirroring currents Imr1 to Imr5.

According to the mirror oscillating unit 500 having the same configuration as in FIG. 3B, the oscillating signal XOSC is the amount of current of the first to fifth mirroring currents Imr1 to Imr5, that is, the mirroring current group GImr ) And has a frequency according to the amount of current.

In other words, the oscillating signal XOSC oscillates with a frequency according to the amount of current of the net current Inet.

Referring to FIG. 2 again, the data converter 600 detects the frequency of the oscillating signal XOSC and converts it into sensing data DSEN.

In summary, in the photo-sensing device of the present invention, when the energy of the received light LGT is reflected and confirmed as the frequency of the oscillating signal XOSC, the current amount, not the voltage level, is significantly used as an electrical component. . That is, the photo sensing device of the present invention is a current type photo sensing device.

According to the photo-sensing device of the present invention, even when the level of the power supply voltage VDD provided to the inverters INV1 to INV5 of the operational amplifier 420 and / or the oscillating unit 530 is lowered, it is received. It is possible to effectively detect the energy of the received light LGT. That is, the photo sensing device of the present invention has a wide dynamic range.

In addition, in the photo-sensing device of the present invention, the net current (Inet) minus the noise current (Ins) removed from the noise removing unit 200 with respect to the diode current (Ipd) is reflected and the frequency of the oscillation signal (XOSC) and / Or the data value of the sensing data DSEN is determined.

Therefore, according to the photo-sensing device of the present invention, in particular, low-frequency noise characteristics are improved, and the accuracy of sensing is greatly improved.

The present invention has been described with reference to one embodiment shown in the drawings, but this is merely exemplary, and those skilled in the art will understand that various modifications and other equivalent embodiments are possible therefrom.

For example, in the present specification, an embodiment in which the oscillating unit 530 is composed of five inverters INV1 to INV5 is shown and described. However, it is apparent that the technical idea of the present invention can be implemented by various embodiments in which the oscillating unit 530 is composed of (2m + 1) (where m is a natural number) inverters.

Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the appended claims.

Claims (10)

In the photo sensing device,
A light source for outputting output light, wherein a turn-on state in which the output light is output and a turn-off state in which the output of the output light is blocked are controlled;
The anode terminal is a photodiode that is electrically connected to a stable node to generate a diode current, wherein at least a portion of the diode current is the photodiode dependent on the output light output from the light source;
A noise removing unit driven to remove the noise current with respect to the diode current, wherein the noise current is a current generated by the photodiode, and is a current generated in a turn-off state of the light source;
A sourcing unit sourcing a net current at a spare node, the spare node receiving the net current of the stable node, the net current being the sourcing unit based on the current obtained by removing the noise current from the diode current; And
In the turned-on state of the light source, the net current sourced from the sourcing unit is mirrored to generate a mirroring current group, and the mirror oscillating is driven to generate an oscillating signal having a frequency according to the current amount of the mirroring current group. Having wealth,
The sourcing unit
And a gate terminal and a drain terminal being electrically connected to the spare node, and a source transistor having a source terminal electrically connected to a ground voltage.
The method of claim 1, wherein the noise removing unit
A cancellation transistor having one junction electrically connected to the stable node and the other junction electrically connected to a ground voltage;
A removal capacitor having one terminal electrically connected to a gate terminal of the removal transistor; And
And a removal switch driven to electrically connect the preliminary node and the gate terminal of the elimination transistor in the turn-off state of the light source.
delete The method of claim 1, wherein the photo sensing device
The photo-sensing device further comprises a stabilizing unit that transmits the net current from the stable node to the spare node, but is driven to maintain the voltage of the stable node.
According to claim 4, The stabilization unit
A stabilization transistor having one side junction electrically connected to the stable node, and the other side junction electrically connected to the sourcing unit; And
An operational amplifier for generating an output signal having a level according to the difference of the stable node with respect to a reference voltage, wherein the output signal includes the operational amplifier applied to the gate terminal of the stabilization transistor.
According to claim 1, The mirror oscillating unit
A mirroring unit including a common mirroring transistor generating a common mirroring current by mirroring the net current sourced by the sourcing unit, wherein the mirroring current group comprises: the mirroring unit including the common mirroring current; And
An oscillating unit including first to nth (where n is an odd number of 3 or more) inverters, each having a pull-up transistor and a pull-down transistor, wherein the first to nth inverters form an oscillating chain, and thus the oscillation The oscillating unit for generating a transition signal is provided,
The junction of the pull-down transistors of each of the first to n-th inverters is
A photo-sensing device characterized by receiving the common mirroring current in common.
The method of claim 6, wherein the mirror oscillating unit
And a mirroring switch driven to electrically connect the spare node to the gate terminal of the common mirroring transistor in the turned-on state of the light source.
According to claim 1, The mirror oscillating unit
A mirroring unit including first to nth mirroring transistors that mirror the net current sourced by the sourcing unit to generate first to nth (where n is an odd number equal to or greater than 3) mirroring current, wherein the mirroring current is The group may include the mirroring units including the first to nth mirroring currents; And
An oscillating unit comprising first to n-th inverters, each of which has a pull-up transistor and a pull-down transistor, wherein the first to nth inverters form an oscillating chain to generate the oscillation signal. Equipped with,
The junction of each of the pull-down transistors of the first to n-th inverters is
And the corresponding first to n-th mirroring currents.
The method of claim 8, wherein the mirror oscillating unit
And a mirroring switch driven to electrically connect the spare node to a gate terminal of the first to nth mirroring transistors when the light source is turned on.
The method of claim 1, wherein the photo sensing device
And a data conversion unit that senses the frequency of the oscillating signal and converts it into sensing data.

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