High sensitivity optoelectronic integrated sensor with adjustable dynamic range

Abstract

The application discloses a kind of high sensitivity photoelectric integrated sensor technology with adjustable dynamic range, it is related to photoelectric sensor and signal processing circuit.The technical scheme is proposed to the contradiction that wide dynamic range and high sensitivity are difficult to consider in existing photoelectric sensing technology.By adjusting the gate input voltage of PD-MOS tube to adjust sensitivity, and the sensing signal reading can be read out in a continuous way, so that the timing circuit for controlling the integration process is not needed, making the structure more simple.In addition, by changing the gate input voltage to adjust the bulk effect transconductance of PD-MOS tube, the high sensitivity range is adjusted to widen the dynamic range, and automatically adapt to different light intensity environment.

Description

Technical Field

[0001] This invention relates to photoelectric sensors, and more particularly to a high-sensitivity photoelectric integrated sensor with adjustable dynamic range. Background Technology

[0002] CN213583789U discloses a photodiode biased field-effect transistor, namely PD-MOS.

[0003] In existing technologies, there is a trade-off between wide dynamic range and high sensitivity in CMOS photoelectric sensors. For photoelectric sensors, wide dynamic range and high sensitivity under low light conditions are important performance indicators, but high sensitivity means reaching saturation more quickly; that is, there is a trade-off between dynamic range and sensitivity. Therefore, to achieve both high sensitivity and wide dynamic range simultaneously, additional control circuitry is needed to adjust the integration time to extend the dynamic range.

[0004] like Figure 1 As shown, the photoelectric conversion method is achieved by measuring the voltage drop across the capacitor by integrating the PD photocurrent over a certain time period. M. Ikebe and K. Saito, "A Wide-Dynamic-Range Compression Image Sensor With Negative-Feedback Resetting," in IEEE Sensors Journal, vol.7, no.5, pp.897-904, May 2007, doi:10.1109 / JSEN.2007.894897, demonstrate a method to change the sensitivity by adjusting the integration time. Under low light conditions, the current generated by the PD integrates within time T', causing the capacitor voltage to decrease. If the read voltage is greater than the threshold Vmid, integration continues within the remaining time T-T', and the integrated voltage is read out at time T. Under strong light conditions, the voltage drop formed by the integration of the current generated by the PD within time T' is sufficient to reach saturation. If the read voltage is less than the threshold Vmid when reading out at time T', a reset restores the read node voltage to Vmid, and integration resumes within the shorter remaining time T-T', preventing saturation distortion caused by excessive integration time. This design requires additional voltage comparison and storage circuitry.

[0005] like Figure 2As shown, in AMS's integrated ambient light sensor TSL2572 optical-to-digital signal converter, the photodiode (PD) at CH0 acts as a photoelectric sensor, and the PD at CH1 acts as a noise collector. Both channels simultaneously undergo integration and digitization via an integrating analog-to-digital converter (ADC). At the end of the conversion cycle, the result is sent to a data shift register for differential processing in subsequent steps. The resolution and sensitivity of this architecture are achieved by adjusting the integration time and gain control; that is, a longer integration time and higher gain are selected in low light to enhance signal strength, while a shorter integration time and gain are selected in strong light to extend the dynamic range. In this architecture, on the one hand, the differential operation between signal and noise is performed in the digital domain, requiring additional computation modules; on the other hand, sensitivity control requires additional gain control structures and complex timing control circuits, making the system complex. Summary of the Invention

[0006] The purpose of this invention is to provide a high-sensitivity photoelectric integrated sensor with adjustable dynamic range to solve the problems existing in the prior art.

[0007] The high-sensitivity optoelectronic integrated sensor with adjustable dynamic range described in this invention adjusts its sensitivity and dynamic range by regulating the gate input voltage of the PD-MOS transistor.

[0008] Includes the following structure:

[0009] The PD cathode of the photosensitive PD-MOS transistor and the PD cathode of the light-shielding PD-MOS transistor are connected at the same point to the PD input voltage;

[0010] The gate of the photosensitive PD-MOS transistor and the gate of the light-shielding PD-MOS transistor are connected at the same point to the gate input voltage;

[0011] The source of the photosensitive PD-MOS transistor and the source of the light-shielding PD-MOS transistor are connected to the drain of the third MOS transistor at the same point. The source of the third MOS transistor is grounded, and the gate of the third MOS transistor is connected to the bias voltage.

[0012] The drain of the photosensitive PD-MOS transistor is connected to the drain of the first MOS transistor, and the drain voltage of the photosensitive PD-MOS transistor is used as the output voltage.

[0013] The drain of the light-shielding PD-MOS transistor is connected to the drain of the second MOS transistor; the gate of the first MOS transistor and the gate of the second MOS transistor are connected to the drain of the second MOS transistor after they reach the same point.

[0014] The source of the first MOSFET and the source of the second MOSFET are respectively connected to the operating voltage.

[0015] Alternatively, a feedback unit can be configured to dynamically adjust the gate input voltage based on the output voltage.

[0016] The gate input voltage is set to multiple levels, and each level corresponds to a sensor output voltage range;

[0017] When the sensor output voltage is higher than the upper limit of the current range, the feedback unit increases the current gate input voltage;

[0018] When the sensor output voltage is lower than the lower limit of the current range, the feedback unit reduces the current gate input voltage.

[0019] The high-sensitivity optoelectronic integrated sensor with adjustable dynamic range described in this invention has the advantage of continuous readout of sensing signals, eliminating the need for timing circuits controlling the integration process and simplifying the structure. By adjusting the bulk transconductance of the PD-MOS transistor through changing the gate input voltage, the high-sensitivity range is adjusted to broaden the dynamic range and automatically adapt to different light intensity environments. Attached Figure Description

[0020] Figure 1 It is an integral time adjustment timing diagram in the prior art.

[0021] Figure 2 This is a schematic diagram of a sensor structure in existing technology.

[0022] Figure 3 This is a schematic diagram of the structure of the high-sensitivity optoelectronic integrated sensor with adjustable dynamic range described in this invention.

[0023] Figure 4 This is a curve showing the adjustable gain characteristics of the PD-MOS described in this invention.

[0024] Figure 5 This is a simulation result diagram of the high-sensitivity optoelectronic integrated sensor described in this invention.

[0025] Figure label:

[0026] First MOSFET M1, second MOSFET M2, third MOSFET M3;

[0027] Photosensitive PD-MOS transistor U1, light-shielding PD-MOS transistor U1;

[0028] The photocurrent I of the PD-MOS transistor Photo . Detailed Implementation

[0029] like Figure 3 As shown, the high-sensitivity optoelectronic integrated sensor with adjustable dynamic range described in this invention adjusts its sensitivity by regulating the gate input voltage of the PD-MOS transistor.

[0030] Includes the following structure:

[0031] The PD cathode of the photosensitive PD-MOS transistor U1 and the PD cathode of the light-shielding PD-MOS transistor U2 are connected at the same point to the PD input voltage.

[0032] The gate of the photosensitive PD-MOS transistor U1 and the gate of the light-shielding PD-MOS transistor U2 are connected at the same point to the gate input voltage.

[0033] The source of the photosensitive PD-MOS transistor U1 and the source of the light-shielding PD-MOS transistor U2 are connected to the drain of the third MOS transistor M3 at the same point. The source of the third MOS transistor M3 is grounded, and the gate of the third MOS transistor M3 is connected to the bias voltage.

[0034] The drain of the photosensitive PD-MOS transistor U1 is connected to the drain of the first MOS transistor M1, and the drain voltage of the photosensitive PD-MOS transistor U1 is used as the sensing output voltage.

[0035] The drain of the light-shielding PD-MOS transistor U2 is connected to the drain of the second MOS transistor M2. The gate of the first MOS transistor M1 and the gate of the second MOS transistor M2 are connected to the drain of the second MOS transistor M2 after they reach the same point.

[0036] The source of the first MOSFET M1 and the source of the second MOSFET M2 are respectively connected to the operating voltage.

[0037] A feedback unit is also provided to dynamically adjust the gate input voltage based on the sensor output voltage.

[0038] The gate input voltage is set to multiple levels, and each level corresponds to a sensor output voltage range.

[0039] When the sensor output voltage is higher than the upper limit of the current range, the feedback unit increases the current gate input voltage.

[0040] When the sensor output voltage is lower than the lower limit of the current range, the feedback unit reduces the current gate input voltage.

[0041] The working principle of the high-sensitivity photoelectric integrated sensor with adjustable dynamic range described in this invention is as follows:

[0042] The gain of a PD-MOS transistor increases with increasing gate input voltage, as shown in the gain characteristic curve. Figure 4 As shown, the adjustable gain of the PD-MOS transistor allows for adjustment of the light intensity range corresponding to high sensor sensitivity, thereby achieving high-sensitivity and wide dynamic range optical sensing.

[0043] To reduce the impact of dark current noise, photosensitive PD-MOS transistor U1 and light-shielding PD-MOS transistor U2 are used as an input differential pair to generate differential current, completing the subtraction of photocurrent and dark current at the circuit level. Compared to the traditional optoelectronic integrated sensor reset-integration-readout method, which requires corresponding timing control circuitry for readout, this invention uses an active current mirror as a load to convert the differential current into a single-ended output voltage, directly and continuously outputting without integration. Therefore, the system structure can be simplified. The third MOS transistor M3 acts as a tail current source, serving as a current clamp. For a given tail current, the gate input voltage V... G The quiescent operating point of the PD-MOS source can be adjusted, thereby modulating the bulk transconductance of the PD-MOS and altering the photocurrent range corresponding to maximum sensitivity. Therefore, by adjusting the gate input voltage, high-sensitivity measurement of photocurrents across different ranges can be achieved, simultaneously balancing high sensitivity and wide dynamic range. The host computer can obtain the sensor output voltage and the current gate input voltage through the feedback unit, and then acquire illumination information using conventional algorithms.

[0044] The specific adjustment process is as follows: The gate input voltage is set to multiple levels, each level corresponding to a sensor output voltage range, or the gate input voltage is continuously adjustable, and each designed input voltage corresponds to a current sensor output voltage range. For simplicity, this embodiment uses a level-based scheme.

[0045] like Figure 5 As shown, in this embodiment, the gate input voltage is divided into 5 levels, each corresponding to a different range. (Horizontal axis I) Photo It is photocurrent, which is the sensed quantity; the vertical axis is V. OUT This is the converted output voltage, the output quantity. When the sensor output voltage is higher than the upper limit of the current range, the feedback unit increases the current gate input voltage. When the sensor output voltage is lower than the lower limit of the current range, the feedback unit decreases the current gate input voltage.

[0046] For those skilled in the art, various other corresponding changes and modifications can be made based on the technical solutions and concepts described above, and all such changes and modifications should fall within the protection scope of the claims of this invention.

Claims

1. A high-sensitivity photoelectric integrated sensor with adjustable dynamic range, characterized in that, Sensitivity and dynamic range can be adjusted by regulating the gate input voltage of the PD-MOS transistor; Includes the following structure: The PD cathode of the photosensitive PD-MOS transistor (U1) and the PD cathode of the light-shielding PD-MOS transistor (U2) are connected at the same point to the PD input voltage; The gate of the photosensitive PD-MOS transistor (U1) and the gate of the light-shielding PD-MOS transistor (U2) are connected at the same point to the gate input voltage; The source of the photosensitive PD-MOS transistor (U1) and the source of the light-shielding PD-MOS transistor (U2) are connected at the same point to the drain of the third MOS transistor (M3). The source of the third MOS transistor (M3) is grounded, and the gate of the third MOS transistor (M3) is connected to the bias voltage. The drain of the photosensitive PD-MOS transistor (U1) is connected to the drain of the first MOS transistor (M1), and the drain voltage of the photosensitive PD-MOS transistor (U1) is used as the sensing output voltage. The drain of the light-shielding PD-MOS transistor (U2) is connected to the drain of the second MOS transistor (M2); the gate of the first MOS transistor (M1) and the gate of the second MOS transistor (M2) are connected to the drain of the second MOS transistor (M2) after they reach the same point; The source of the first MOSFET (M1) and the source of the second MOSFET (M2) are respectively connected to the operating voltage.

2. The high-sensitivity photoelectric integrated sensor with adjustable dynamic range according to claim 1, characterized in that, A feedback unit is also provided to dynamically adjust the gate input voltage based on the sensor output voltage.

3. The high-sensitivity photoelectric integrated sensor with adjustable dynamic range according to claim 2, characterized in that, The gate input voltage is set to multiple levels, and each level corresponds to a sensor output voltage range; When the sensor output voltage is higher than the upper limit of the current range, the feedback unit increases the current gate input voltage; When the sensor output voltage is lower than the lower limit of the current range, the feedback unit reduces the current gate input voltage.

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