CMOS blood oxygen sensing system and working time sequence control method

Abstract

The invention discloses a CMOS (complementary metal oxide semiconductor) blood oxygen sensing system and a working time sequence control method, and belongs to the technical field of biomedical sensing and semiconductor photoelectric integration. According to the system, a photoelectric detector array, a column-level analog-to-digital converter array, a multiplexer and a low-voltage differential signal transmission unit are integrated through a CMOS (Complementary Metal Oxide Semiconductor) process, and efficient separation and synchronous processing of multi-wavelength optical signals are realized in combination with a color filter array covering red light and infrared light. In the working process, the mixed light source emits visible light and near-infrared light, the visible light and the near-infrared light are separated through the optical filter and then converted into current signals through the photoelectric detector, the current signals are amplified into voltage signals through the capacitance negative feedback transconductance amplifier, the voltage signals are synchronously digitalized through the column-level ADC, and the voltage signals are transmitted to an external processor through the LVDS at the rate not lower than 1 Gbps to calculate the blood oxygen saturation degree. According to the invention, a full-digital signal link is adopted, the power consumption is obviously reduced, the anti-interference capability and the detection precision are improved, reflection-type and transmission-type dual-mode detection is supported, and wearable equipment and clinical scenes are adapted.

Description

Technical Field

[0001] The present invention belongs to the technical field of biomedical sensing and semiconductor optoelectronic integration, and in particular relates to a digital CMOS blood oxygen sensor chip circuit. Background Art

[0002] As a core physiological parameter of the respiratory and circulatory system, blood oxygen saturation directly reflects the oxygen-carrying capacity of the blood and has important application value in clinical monitoring, sports medicine, and health management. Its measurement principle is based on the difference in the absorption characteristics of hemoglobin and oxyhemoglobin to light of different wavelengths. Traditional technologies mostly use dual-wavelength (red light 660nm and infrared light 940nm) photoelectric detection methods to capture the alternating light signal caused by arterial blood pulsation and the stable light signal of non-pulsating tissue by transmission or reflection, calculate the ratio and map it to the empirical model to derive the blood oxygen saturation value. Although this method has been widely used commercially, its technical architecture has significant bottlenecks: 1. System complexity and power consumption. Traditional sensors require alternating red and infrared light sources and rely on timing control circuits for time-sharing detection. This results in redundant hardware design and high power consumption, making it difficult to meet the rigid requirements of wearable devices for miniaturization and low power consumption.

[0003] 2. Sensitivity to ambient light interference. Analog signal detection is easily affected by ambient light fluctuations and electromagnetic noise. Especially in dynamic scenarios (such as outdoor sports), optical crosstalk can cause baseline drift, reducing measurement accuracy and stability.

[0004] 3. Integration limitations. Analog signals require multiple stages of amplification, filtering, and analog-to-digital conversion. The circuit topology is complex and noise immunity is weak, which restricts the high integration and batch manufacturing consistency of sensor chips.

[0005] In recent years, the integration of CMOS processes and optical sensing technology has provided a new path for digital blood oxygen monitoring. By integrating photodetectors, signal chains, and analog-to-digital conversion modules on-chip, digital sensors can significantly improve signal-to-noise ratios and interference immunity, and support algorithm optimization (such as dynamic baseline correction and motion artifact suppression). However, existing digital solutions are still limited by complex multi-light source driving logic, low multi-wavelength separation efficiency, and reliance on specialized optical filters, which leads to high costs.

[0006] Furthermore, traditional dual-wavelength light source solutions, due to their fixed spectral bandwidth, struggle to adapt to the nonlinear characteristics of the Hb / HbO2 absorption coefficient curve, and are prone to measurement deviations under conditions of low perfusion or abnormal hemoglobin levels. While emerging multi-wavelength detection technologies can enhance model robustness, they face challenges such as bulky light source arrays and surging power consumption.

[0007] To address the above pain points, a new blood oxygen sensing architecture is urgently needed that can simplify the light source module, enhance ambient light suppression, and integrate a fully digital signal chain while ensuring high-precision measurement. Summary of the Invention

[0008] To solve the above technical problems in the prior art, the present invention provides a CMOS blood oxygen sensor system, which includes a light source module, a photodetector, a processor, and a display. The system includes: A color filter array, including a red light filter and an infrared light filter, covers the front end of the photodetector array; CMOS blood oxygen sensor chip circuit, the CMOS blood oxygen sensor chip circuit includes a timing control module, a photodetector array, and a data conversion module; The photodetector array is composed of photodiodes made in CMOS technology, which receives the light signal separated by the color filter and converts it into a current signal; The data conversion module includes a column-level analog-to-digital converter array, a multiplexer, and a low-voltage differential signaling unit; The timing control module is configured to generate row select signals and clock signals, coordinate the synchronous operation of the photodetector array and the data conversion module. The timing control module is configured to generate row select signals and clock signals, control the scanning of the photodetector array by activating the row select signals row by row, and coordinate its synchronous operation with the data conversion module.

[0009] The data conversion module also includes a capacitive negative feedback transconductance amplifier. Each photodiode in the photodetector array is connected to the capacitive negative feedback transconductance amplifier to convert the current signal into a voltage signal, and the voltage is converted by the formula:

[0010] For signal amplification, C is the integral capacitor, I is the photocurrent, T int is the integration time.

[0011] The data conversion module includes an ADC array and a multiplexer, and each ADC unit in the ADC array corresponds to a column of photodetectors.

[0012] The timing control module controls the scanning of the photodetector array by activating the row selection signal row by row, and provides a sampling clock signal for the ADC array.

[0013] The data converted by the data conversion module is output to an external device via a low voltage differential signal unit. The low voltage differential signal unit outputs digital signals in the form of a serial data stream with a transmission rate of not less than 1 Gbps.

[0014] The luminous intensity of the light source module is adjusted by an external circuit.

[0015] The processor is selected from a microprocessor, FPGA, single chip microcomputer or digital signal processor.

[0016] The power consumption of the CMOS blood oxygen sensor chip circuit is less than 5 mA and the sampling frequency is 1 kHz.

[0017] The system is applicable to reflective or transmissive blood oxygen detection architectures.

[0018] In another aspect, the present invention provides a method for controlling the operating timing of a CMOS blood oxygen sensor system, comprising the following steps: (1) Initialization phase: After the CMOS blood oxygen sensor system is powered on, the timing control module generates an initial clock signal and a reset signal, and the photodetector array and the column-level analog-to-digital converter enter a standby state; (2) Signal acquisition stage: The timing control module selects the target row of the photodetector array by activating the row selection signal row by row. The photodiode receives the light signal transmitted through the color filter and converts it into a current signal. The capacitive negative feedback transconductance amplifier converts the current signal into a voltage signal and transmits it to the ADC unit under the control of the row selection signal. (3) Signal digitization stage: the ADC unit performs synchronous sampling and analog-to-digital conversion on the voltage signal to generate a digital signal, and transmits the digital signal to the multiplexer unit; (4) Signal output stage: The multiplexer loads multiple columns of parallel digital signals into the shift register in parallel, and integrates the multiple columns of parallel digital signals into a serial signal through time-sharing shifting. The serial data stream is output to the external processor at a transmission rate of not less than 1 Gbps through the low-voltage differential signal unit; (5) Circular scanning stage: Repeat steps (2) to (4) to complete the scanning of the photodetector array row by row until all row signals are collected, converted and output.

[0019] The present invention has the following beneficial effects compared to the prior art: This application overcomes the technical difficulties of traditional blood oxygen sensing in terms of light source control complexity and high power consumption, analog signal susceptibility to interference and low integration, environmental noise affecting measurement accuracy, the contradiction between dynamic power consumption and real-time performance, and insufficient adaptability to multiple scenarios through the collaborative design of color filter arrays and CMOS processes. Combining column-level high-precision analog-to-digital conversion and LVDS differential transmission technology, it effectively suppresses interference from ambient light and electromagnetic noise, achieves high-resolution sampling, supports continuous sampling of thousands of frames per second, and realizes millisecond-level delay capture of dynamic physiological signals; the modular design can adapt to 128×128 to 512×512 pixel array expansion, taking into account flexibility and efficiency; through optimized timing control modules and full-link low-power design, the operating current is less than 5mA at a sampling rate of 1kHz, solving the battery life bottleneck of wearable devices, while supporting reflective and transmissive dual-mode detection, expanding applicability to multiple scenarios, and providing a reliable solution for high-precision portable blood oxygen monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the principle of transmission-type photoelectric detection of blood oxygen saturation in the prior art; Figure 2 This is a schematic diagram of the reflective photoelectric detection principle of blood oxygen saturation in the prior art; Figure 3 Reflective architecture diagram of the CMOS blood oxygen sensor system of the present invention; Figure 4 Diagram of the transmission architecture of the CMOS blood oxygen sensor system of the present invention; Figure 5 Circuit diagram of the CMOS blood oxygen sensor chip of the present invention; Figure 6 A physical picture of the CMOS blood oxygen sensor of the present invention; Figure 7 A calibration curve diagram of an embodiment of a CMOS blood oxygen sensor of the present invention; Figure 8 Timing diagram of the CMOS blood oxygen sensing system of the present invention. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the present invention more clearly apparent, the present invention is described below using specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely illustrative and are not intended to limit the scope of the present invention. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessary confusion of the concepts of the present invention.

[0022] The present invention provides a CMOS blood oxygen sensor system, which includes a light source module, a photodetector, a processor, and a display. The system includes: a color filter array, including a red light filter and an infrared light filter, covering the front end of the photodetector array; a CMOS blood oxygen sensor chip circuit, which includes a timing control module, a photodetector array, and a data conversion module. The photodetector array is composed of photodiodes using a CMOS process, receives light signals separated by color filters and converts them into current signals; the data conversion module includes a column-level analog-to-digital converter array, a multiplexer, and a low-voltage differential signal unit; the timing control module is configured to generate row select signals and clock signals, coordinate the synchronous operation of the photodetector array and the data conversion module. The timing control module is configured to generate row select signals and clock signals, control the scanning of the photodetector array by activating the row select signals row by row, and coordinate its synchronous operation with the data conversion module.

[0023] like Figure 5 The CMOS blood oxygen sensor chip circuit is composed of a timing control circuit, a photodetector array, a data conversion module (including a column-level ADC array and a multiplexer) and an LVDS output module. Each module is closely connected with the data stream through timing synchronization. As the core controller of the system, the timing control circuit first sends a control signal to the photodetector array to control the timing of its integration and data readout, and at the same time provides a synchronous sampling clock, a shift clock and a reset signal to the digital-to-analog conversion module to ensure strict synchronization of each link. After the photodetector array converts the received light signal into an analog voltage signal, it is selected by the row selection signal and transmitted to the column-level ADC array, which completes the high-precision conversion of the analog signal to a 16-bit parallel digital signal under timing control. A row of parallel data output by the ADC then enters the multiplexer for parallel-to-serial processing, and the final serial data stream is passed to the LVDS output module and transmitted outside the chip.

[0024] The CMOS blood oxygen sensor of the present invention is as follows Figure 6 As shown, a homemade blood oxygen sensor based on a color filter array is used to read out red light (660nm) and infrared light (940nm) signals, and the R value is calculated according to the following formula.

[0025]

[0026] Among them, AC red and DC red Respectively represent the alternating part and DC part of the red light output, AC ir and DC ir They represent the alternating and direct current parts of the infrared light output respectively.

[0027] Convert the R value to blood oxygen saturation SPO2 value through the calibration curve:

[0028] Wherein A and B are equipment calibration constants. The calibration curve of this embodiment is as follows Figure 7 As shown in the figure, the calibration curve shows that A=111.71, B=31.03, and the linear correlation coefficient is 0.923.

[0029] The data conversion module also includes a capacitive negative feedback transconductance amplifier (CTIA). The photodetector array consists of photodiodes based on a CMOS process, each of which is connected to a capacitive negative feedback transconductance amplifier (CTIA). When a light signal passes through the color filter and strikes the photodiode, it converts the light signal into a weak current signal. The CTIA then converts this current signal into a voltage signal and amplifies the signal using the following formula:

[0030] For signal amplification, C is the integral capacitor, I is the photocurrent, T int is the integration time. The integration time Tint is related to the sampling frequency f, and Tint≤1 / f.

[0031] The data conversion module includes an ADC array and a multiplexer. Each ADC unit in the ADC array corresponds to a column of photodetectors. The timing control module controls the scanning of the photodetector array by activating row select signals row by row, providing a sampling clock signal for the ADC array. The data converted by the data conversion module is output to an external device via a low-voltage differential signaling unit. The low-voltage differential signaling unit outputs the digital signal as a serial data stream with a transmission rate of no less than 1 Gbps.

[0032] The luminous intensity of the light source module is regulated by an external circuit. The processor is selected from a microprocessor, FPGA, single-chip microcomputer, or digital signal processor. The CMOS blood oxygen sensor chip circuit consumes less than 5 mA and has a sampling frequency of 1 kHz. The system is suitable for reflective or transmissive blood oxygen detection architectures.

[0033] On the other hand, the present invention provides a method for controlling the working timing of a CMOS blood oxygen sensor system, comprising the following steps: (1) an initialization phase: after the CMOS blood oxygen sensor system is powered on, a timing control module generates an initial clock signal and a reset signal, and the photodetector array and the column-level analog-to-digital converter enter a standby state; (2) a signal acquisition phase: the timing control module selects a target row of the photodetector array by activating a row selection signal row by row, the photodiode receives a light signal transmitted through a color filter and converts it into a current signal, and a capacitor negative feedback transconductance amplifier converts the current signal into a voltage signal and transmits it to an ADC unit under the control of the row selection signal; (3) Signal digitization stage: The ADC unit performs synchronous sampling and analog-to-digital conversion on the voltage signal to generate a digital signal, and transmits the digital signal to the multiplexer unit; (4) Signal output stage: The multiplexer loads multiple columns of parallel digital signals into the shift register in parallel, and integrates the multiple columns of parallel digital signals into a serial signal by time-sharing shifting. The serial data stream is output to the external processor at a transmission rate of no less than 1Gbps through the low-voltage differential signal unit; (5) Cyclic scanning stage: Repeat steps (2) to (4) to complete the scanning of the photodetector array row by row until all row signals are collected, converted and output. The present invention overcomes the problems of high power consumption, signal interference, low integration and poor adaptability to multiple scenarios of traditional blood oxygen sensors through the coordinated design of color filter array and CMOS process. It adopts CTIA low-noise amplification, column-level high-precision ADC and LVDS differential transmission technology to suppress ambient light and electromagnetic noise, achieve microvolt-level resolution sampling, and support high-speed continuous capture of dynamic physiological signals at 1,000 frames per second; the modular architecture adapts to 128×128 to 512×512 pixel expansion, combines timing optimization with full-link low-power design, and operates at a current of less than 5mA at a 1kHz sampling rate, breaking through the battery life bottleneck of wearable devices; it also supports reflective and transmissive dual-mode detection, adapting to the needs of multiple scenarios, and providing high-precision, low-power blood oxygen monitoring solutions for portable medical devices.

[0034] The present invention provides a digital CMOS blood oxygen sensor chip circuit, comprising: a light source module comprising infrared and near-infrared LEDs with an emission wavelength range of 400nm to 1000nm. The infrared and near-infrared LEDs are precisely controlled by an external circuit in the prior art, and their luminous intensity can be adjusted to meet the needs of blood oxygen detection in different environments; a color filter array comprising a red light filter and an infrared light filter, covering the front end of the photodetector array. These filters can effectively separate light signals of different wavelengths, ensuring that each photodiode receives only light of a specific wavelength, thereby significantly improving the accuracy of blood oxygen detection; a processor for receiving digital signals and calculating blood oxygen saturation values; and a display for displaying the blood oxygen saturation values.

[0035] In one embodiment, the column-level analog-to-digital converter (ADC) array in the data conversion module of the present invention utilizes 16-bit Σ-Δ ADCs. Each ADC unit corresponds to a column of photodetectors, enabling simultaneous sampling and conversion of multiple columns of signals, improving signal processing efficiency and effectively reducing signal crosstalk.

[0036] In this invention, a multiplexer (MUX) is used to combine the parallel digital signals output by multiple ADC columns into a single signal. Using a parallel-to-serial circuit, the multiplexer converts the parallel data into a serial data stream, simplifying the data transmission process and improving transmission efficiency. A processor (microprocessor, FPGA, single-chip microcomputer, or digital signal processor) receives the digital signals and calculates the blood oxygen saturation value. After calculation, the processor transmits the blood oxygen saturation value to a display (such as an LCD screen or computer monitor) for display, allowing the user to understand their blood oxygen status in real time.

[0037] The timing control module controls the scanning of the photodetector array by activating row-by-row row-select signals and provides a sampling clock signal for the ADC. The timing control module in this invention serves as the system's scheduling center, coordinating the operating timing of the photodetector array and the data conversion module. By generating row-select and clock signals, this module activates the photodetector array row by row and provides a precise sampling clock signal for the ADC, ensuring synchronization of signal acquisition and processing and preventing signal loss or aliasing.

[0038] This invention uses a low-voltage differential signaling (LVDS) unit to output a serial data stream to an external processor at a transmission rate of no less than 1 Gbps. LVDS technology utilizes differential signaling, offering strong anti-interference capabilities and high transmission rates, ensuring the integrity and stability of digital signals over long distances. The light intensity of the light source module is regulated by an external circuit. The blood oxygen sensor chip consumes less than 5 mA and has a sampling frequency of 1 kHz. The system is suitable for both reflective and transmissive blood oxygen sensing architectures.

[0039] The architecture and working principle of the CMOS blood oxygen sensor system of the present invention are as follows: (1) Photodetector array The photodetector array is the system's front-end signal acquisition unit, comprised of CMOS-based photodiodes. Color filters cover the photodiodes, separating light signals of different wavelengths (such as red and infrared). When light signals pass through human tissue and are reflected or transmitted, the photodiodes receive these signals and convert them into weak current signals. To convert these current signals into a processable voltage, the system employs a capacitive transconductance amplifier (CTIA) circuit to amplify and convert the current signals. The CTIA's high gain and low noise characteristics effectively improve the signal-to-noise ratio.

[0040] (2) Data conversion module The data conversion module is the system's core processing unit, responsible for converting the analog voltage signals output by the photodetector array into digital signals. This module utilizes a column-level ADC array design, with each ADC unit corresponding to a column of photodetectors. This allows for simultaneous sampling and conversion of signals from multiple columns. This design not only improves signal processing efficiency but also reduces signal crosstalk. The converted digital signals are integrated by a multiplexer (MUX) unit and converted into a serial data stream via a parallel-to-serial circuit. Finally, the serial data is output to external devices via a low-voltage differential signaling (LVDS) unit. LVDS technology offers strong interference immunity and high transmission rates, making it suitable for high-speed data transmission.

[0041] (3) Timing control module The timing control module is the system's scheduling center, responsible for coordinating the operating timing of the photodetector array and the data conversion module. It generates row-select signals (such as RD1, RD2, and RDN) to control the row-by-row scanning of the photodetector array and provides precise sampling clock signals for the column-level ADC units. The timing control module's design ensures synchronization of signal acquisition and processing, preventing signal loss or confusion.

[0042] The timing circuit inside the digital CMOS blood oxygen sensor chip circuit of the present invention is as follows Figure 8 As shown, the system's working sequence is precisely scheduled by the timing control module. The specific steps are as follows: Row select signal activation and signal acquisition The timing control module sequentially generates high-level row select signals (RD1, RD2, ..., RDN) and reset signals (RST1, RST2, ..., RSTN), selecting each row in the photodetector array. For example, when RD1 is high, the photodetectors in the first row are activated, and their output voltage signals are transmitted to the column-level ADC unit. The high-level duration of the row select signals is determined by the system design and is typically a fixed clock cycle.

[0043] (2) Signal digitization and column-level ADC processing When the row select signal is activated, the column-level ADC units synchronously sample and perform analog-to-digital conversion on the selected row signal. Each column-level ADC unit operates independently, converting the analog voltage signal into a digital signal. The ADC's sampling accuracy and resolution directly impact the system's detection precision, so high-precision ADC designs are typically used.

[0044] (3) Signal multiplexing and parallel-to-serial processing The digitized signal is then transmitted to a multiplexer (MUX) unit. This unit sequentially integrates multiple columns of parallel digital signals and converts the parallel data into a serial data stream using a parallel-to-serial circuit. This process reduces data transmission complexity and improves efficiency.

[0045] (4) LVDS output and data transmission The serial data stream is output via a low-voltage differential signaling (LVDS) unit. LVDS technology utilizes differential signaling, offering strong interference immunity and high transmission rates, ensuring the integrity and stability of digital signals over long distances. The output data is then transmitted to an external device (such as a microprocessor or computer) for further processing and analysis.

[0046] In one embodiment, the present invention proposes a digital CMOS blood oxygen sensor chip circuit suitable for wearable devices (such as smartwatches) and portable medical devices (such as oximeters). This circuit achieves high-precision acquisition and digital processing of blood oxygen signals through the coordinated operation of a photodetector array, a data conversion module, and a timing control module. This circuit utilizes CMOS technology to achieve high integration and low power consumption. Furthermore, a color filter separates red and infrared light signals to ensure accurate measurement of blood oxygen saturation.

[0047] (1) Photodetector array Photodiode array: A 1×2 photodiode array integrated using a 3.5μm CMOS process. Each pixel unit is covered with red (660nm) and infrared (940nm) color filters to separate red (660nm) and infrared (940nm) light signals. The size of a single pixel is 1000μm × 1000μm. The photodiode uses an N-well photodiode using a silicon (Si) process, with a light response range of 400nm-1000nm. Capacitive transconductance amplifier (CTIA): Each photodiode is connected to a TIA circuit to convert the photocurrent signal I into a voltage signal V. The CTIA is designed with low noise and high gain to improve the signal-to-noise ratio. The conversion formula is:

[0048] In the formula, the photocurrent is about 1uA, the power supply voltage is 3.3V, the sampling frequency is 1KHz, the integration time is 1ms, and the size of the integration capacitor C is designed to be 0.5nF.

[0049] (2) Data conversion module Column-level ADC array: Utilizes 16-bit precision column-level Σ-Δ ADCs, with each ADC unit corresponding to a column of photodetectors, supporting synchronous sampling and conversion.

[0050] Multiplexer (MUX): Combines the parallel digital signals output by multiple ADC columns into one signal. It converts parallel data into a serial data stream, reducing the complexity of data transmission.

[0051] LVDS output unit: uses low voltage differential signaling (LVDS) technology to transmit serial data streams to external processors at high speed.

[0052] (3) Timing control module Row Select Signal Generator: Generates row select signals (RD1, RD2, ..., RDN) to select the photodetector array row by row. Clock Signal Generator: Provides precise sampling clock signals to the ADC and MUX to ensure synchronization of signal acquisition and processing.

[0053] The 16-bit ADC in this invention supports high-precision signal conversion. The sampling rate is 1000 samples per second, meeting real-time monitoring requirements. The operating current is less than 5mA, making it suitable for battery-powered devices.

[0054] Through the above-mentioned implementation, the color filter-based digital CMOS blood oxygen sensor chip circuit of the present invention realizes high-precision, low-power and highly integrated blood oxygen saturation measurement, and has broad application prospects.

[0055] By integrating a white-light to near-infrared light source (wavelength 400nm-100nm), a red (660nm) and infrared (940nm) color filter array, a 16-bit Σ-Δ analog-to-digital converter (ADC), and a capacitive transconductance amplifier (CTIA), this device significantly improves blood oxygen saturation detection accuracy (error <±1%), reduces the impact of stray light, and reduces device size. Combining CMOS technology enables monolithic integration of photoelectric detection, signal processing, and data transmission modules, resulting in a system operating current of less than 5mA, a 40% reduction in power consumption, and a 50% reduction in size. LVDS differential transmission (1Gbps) and synchronous sampling technology effectively suppress ambient light and electromagnetic interference, support 1kHz high-frequency real-time monitoring, and be compatible with both reflective and transmissive dual-mode detection. Suitable for wearable devices and clinical medical scenarios, this device meets the requirements of high precision, low power consumption, and interference resistance in a portable form factor.

[0056] This invention overcomes the high power consumption and complex control problems caused by the alternating driving of dual light sources in traditional blood oxygen sensors. It directly separates the mixed light signal through a filter array, simplifying the light source design. It solves the problems that analog signals are susceptible to noise interference and the peripheral circuits are bulky and difficult to integrate. It adopts a fully digital signal link (CTIA→Σ-ΔADC→LVDS) to achieve anti-interference and high integration. Through the optimization of the timing control module (line-by-line scanning and synchronous sampling), it balances the contradiction between high-frequency sampling (1kHz) and low power consumption (<5mA). The selective transmission of the filter is combined with the dynamic calibration algorithm to suppress stray light and tissue scattering interference, improve the signal-to-noise ratio (SNR≥70dB), and support multi-scenario adaptation, breaking through the limitations of the singleness of traditional architecture.

[0057] The present invention discloses a CMOS blood oxygen sensing system, which has the characteristics of high precision, low power consumption and high integration, and is particularly suitable for wearable devices and portable medical devices.

[0058] It should be noted that the numerous details included in the above description are merely illustrative of the present invention and are not intended to limit the present invention. In other embodiments of the present invention, the method may have more, fewer, or different steps, and the order, inclusion, function, etc. of the steps may differ from those described and illustrated.

Claims

1. A CMOS blood oxygen sensor system, comprising a light source module, a photodetector, a processor, and a display, characterized in that: The sensing system comprises: A color filter array, including a red light filter and an infrared light filter, covers the front end of the photodetector array; CMOS blood oxygen sensor chip circuit, the CMOS blood oxygen sensor chip circuit includes a timing control module, a photodetector array, and a data conversion module; The photodetector array is composed of photodiodes made in CMOS technology, which receives the light signal separated by the color filter and converts it into a current signal; The data conversion module includes a column-level analog-to-digital converter array, a multiplexer, and a low-voltage differential signaling unit; The timing control module is configured to generate row select signals and clock signals, coordinate the synchronous operation of the photodetector array and the data conversion module. The timing control module is configured to generate row select signals and clock signals, control the scanning of the photodetector array by activating the row select signals row by row, and coordinate its synchronous operation with the data conversion module.

2. The CMOS blood oxygen sensing system according to claim 1, characterized in that: The data conversion module also includes a capacitive negative feedback transconductance amplifier. Each photodiode in the photodetector array is connected to the capacitive negative feedback transconductance amplifier to convert the current signal into a voltage signal, and the voltage is converted by the formula: ； For signal amplification, C is the integral capacitor, I is the photocurrent, T int is the integration time.

3. The CMOS blood oxygen sensing system according to claim 1, wherein: The data conversion module includes an ADC array and a multiplexer, and each ADC unit in the ADC array corresponds to a column of photodetectors.

4. The CMOS blood oxygen sensing system according to claim 1, characterized in that: The timing control module controls the scanning of the photodetector array by activating the row selection signal row by row, and provides a sampling clock signal for the ADC array.

5. The CMOS blood oxygen sensing system according to claim 1, wherein: The data converted by the data conversion module is output to an external device via a low voltage differential signal unit. The low voltage differential signal unit outputs digital signals in the form of a serial data stream with a transmission rate of not less than 1 Gbps.

6. The CMOS blood oxygen sensing system according to claim 1, characterized in that: The luminous intensity of the light source module is adjusted by an external circuit.

7. The CMOS blood oxygen sensing system according to claim 1, characterized in that: The processor is selected from a microprocessor, FPGA, single chip microcomputer or digital signal processor.

8. The CMOS blood oxygen sensing system according to claim 1, wherein: The power consumption of the CMOS blood oxygen sensor chip circuit is less than 5mA and the sampling frequency is 1kHz.

9. The CMOS blood oxygen sensing system according to claim 1, wherein: The system is applicable to reflective or transmissive blood oxygen detection architectures.

10. A method for controlling the working timing of a CMOS blood oxygen sensor system according to any one of claims 1 to 9, characterized in that: The following steps are involved: (1) Initialization phase: After the CMOS blood oxygen sensor system is powered on, the timing control module generates an initial clock signal and a reset signal, and the photodetector array and the column-level analog-to-digital converter enter a standby state; (2) Signal acquisition stage: The timing control module selects the target row of the photodetector array by activating the row selection signal row by row. The photodiode receives the light signal transmitted through the color filter and converts it into a current signal. The capacitive negative feedback transconductance amplifier converts the current signal into a voltage signal and transmits it to the ADC unit under the control of the row selection signal. (3) Signal digitization stage: the ADC unit performs synchronous sampling and analog-to-digital conversion on the voltage signal to generate a digital signal, and transmits the digital signal to the multiplexer unit; (4) Signal output stage: The multiplexer loads multiple columns of parallel digital signals into the shift register in parallel, and integrates the multiple columns of parallel digital signals into a serial signal through time-sharing shifting. The serial data stream is output to the external processor at a transmission rate of not less than 1 Gbps through the low-voltage differential signal unit; (5) Circular scanning stage: Repeat steps (2) to (4) to complete the scanning of the photodetector array row by row until all row signals are collected, converted and output.

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