A calibration method and calibration system for dynamic range expansion

Abstract

The application discloses a dynamic range expansion calibration method and a calibration system, wherein the calibration method comprises the following steps: in response to a dynamic range expansion trigger signal, configuring the output current polarity of a second digital-to-analog converter to be opposite; adjusting the input code value of the second digital-to-analog converter according to a bisection method, keeping the adjusted input code value of the second digital-to-analog converter unchanged, and obtaining a first output value of an analog-to-digital converter; adjusting the input code value of a first digital-to-analog converter from a first code value to a second code value, obtaining a second output value of the analog-to-digital converter, determining a code value change amount caused by the change of the input code value of the first digital-to-analog converter according to the difference between the first output value and the second output value, and superimposing the code value change amount on the original direct current component code value. The application can complete the dynamic range expansion calibration without lighting the light-emitting diode, the calibration process is not affected by the change of the current transmission ratio, and the detection accuracy of the sensor is significantly improved.

Description

Technical Field

[0001] This application belongs to the field of PPG sensor technology, specifically relating to a calibration method and calibration system for dynamic range extension. Background Technology

[0002] PPG (Photo Plethysmo Graphy) is an optical measurement technique that measures blood oxygen saturation and heart rate by detecting changes in light absorption. It is widely used in wearable health monitoring devices. PPG sensors typically include a light-emitting diode (LED) and a photodetector. A transimpedance amplifier in the analog front end converts the photocurrent into a voltage signal, which is then sampled and quantized by an analog-to-digital converter.

[0003] Since the photocurrent output by a photodetector consists mostly of ambient light and DC components, existing technologies typically employ digital-to-analog converters (DACs) to cancel these components and extend the dynamic range; this technique is called dynamic range extension (DRE). In practical applications, when factors such as human movement cause changes in the current transfer ratio (CTR), it is necessary to dynamically adjust the current of the DAC used to cancel the DC component to avoid saturation of the TIA (trans-impedance amplifier).

[0004] To obtain the precise change in ADC code value corresponding to the adjustment of DC-canceling DAC code value, the traditional solution requires lighting up the LED and performing two measurements when triggering DRE. The change in code value corresponding to the change in DC-canceling DAC code value is calculated by the difference between the two measurement results.

[0005] However, this scheme has the following problems: On the one hand, the power consumption of the PPG sensor mainly comes from the light-emitting diode. Each DRE trigger requires lighting the light-emitting diode for measurement. When the input signal changes frequently, resulting in a high DRE trigger frequency, the system power consumption increases significantly. On the other hand, the CTR may change dynamically between two measurements, causing the measured difference to be mixed with the error introduced by the CTR change, rather than the pure DC-canceled DAC code value change, which to some extent affects the linearity of the ADC output result. Summary of the Invention

[0006] This application provides a calibration method and system for dynamic range extension, which can complete dynamic range extension calibration without lighting up the light-emitting diode, and the calibration process is not affected by changes in the current transfer ratio, thus significantly improving the detection accuracy of the sensor.

[0007] To address the aforementioned technical problems, this application provides a calibration method for dynamic range extension, applied to a sensor. The sensor includes a light-emitting diode, a photodetector, and an analog front-end coupled to the photodetector. The analog front-end includes a first digital-to-analog converter for outputting a first current, a second digital-to-analog converter for outputting a second current, a transimpedance amplifier, and an analog-to-digital converter coupled to the transimpedance amplifier. The calibration method includes the following steps: In response to the dynamic range extension trigger signal, the connection between the photodetector and the analog front end is disconnected, and the light-emitting diode is turned off; The polarity of the output current of the second digital-to-analog converter is configured to be opposite to that of the output current of the first digital-to-analog converter; The input code value of the second digital-to-analog converter is adjusted according to the binary division method until the second current matches the first current; Keeping the adjusted input code value of the second digital-to-analog converter unchanged, the first output value of the analog-to-digital converter is obtained; wherein, the first output value is the output voltage of the transimpedance amplifier of the first digital-to-analog converter at the first code value, and the first code value is the input code value of the first digital-to-analog converter when the dynamic range expansion is triggered; The input code value of the first digital-to-analog converter is adjusted from the first code value to the second code value, while the input code value of the second digital-to-analog converter remains unchanged; Obtain the second output value of the analog-to-digital converter, wherein the second output value is the output voltage of the transimpedance amplifier when the first digital-to-analog converter is at the second code value; Based on the difference between the first output value and the second output value, the amount of code value change caused by the change in the input code value of the first digital-to-analog converter is determined, and the amount of code value change is superimposed on the original DC component code value.

[0008] As a further improvement to this application, the step of adjusting the input code value of the second digital-to-analog converter according to the binary search method until the second current matches the first current includes: The input code value adjustment range of the second digital-to-analog converter is set, and the adjustment range has an upper limit code value and a lower limit code value; Set the current input code value of the second digital-to-analog converter to the middle code value between the upper limit code value and the lower limit code value; The current input code value of the second digital-to-analog converter is adjusted based on the polarity of the output voltage of the transimpedance amplifier until the output voltage of the transimpedance amplifier is within a preset voltage threshold range, so that the second current matches the first current.

[0009] As a further improvement to this application, the adjustment of the current input code value of the second digital-to-analog converter based on the output voltage polarity of the transimpedance amplifier includes: If the output voltage of the transimpedance amplifier is positive, then the upper limit code value of the adjustment range is updated to the current input code value, and the middle code value between the upper limit code value and the lower limit code value is re-determined as the new current input code value. If the output voltage of the transimpedance amplifier is negative, the lower limit code value of the adjustment range is updated to the current input code value, and the intermediate code value between the upper limit code value and the lower limit code value is redefined as the new current input code value.

[0010] As a further improvement of this application, the second code value is the sum of the change in the first code value and the preset code value, and the change in the current of the first digital-to-analog converter corresponding to the preset code value change is less than the full-scale input current of the transimpedance amplifier.

[0011] As a further improvement of this application, the current change of the first digital-to-analog converter corresponding to the preset code value change is less than half of the full-scale input current of the transimpedance amplifier.

[0012] As a further improvement of this application, the first current is used to cancel the DC component in the output photocurrent of the photodetector, and the second current is used to cancel the ambient light component in the output photocurrent of the photodetector. The original DC component code value is the digital code value corresponding to the DC component canceled by the first current before the dynamic range extension is triggered.

[0013] As a further improvement to this application, after superimposing the code value change onto the original DC component code value, the method further includes: Reconnect the photodetector to the analog front end and turn the light-emitting diode back on; The first digital-to-analog converter is controlled to output a first current to cancel the DC component in the output photocurrent of the photodetector, and the second digital-to-analog converter is controlled to output a second current to cancel the ambient light component in the output photocurrent of the photodetector. Obtain the digital code value output by the analog-to-digital converter, wherein the digital code value is the sum of the AC component and the residual DC component in the output photocurrent; The digital code value is compensated based on the updated DC component code value to obtain the AC component code value corresponding to the AC component in the output photocurrent.

[0014] As a further improvement of this application, under normal operating conditions, the first digital-to-analog converter, the second digital-to-analog converter, and the transimpedance amplifier are all coupled to the photodetector; When the connection between the photodetector and the analog front end is disconnected and the light-emitting diode is turned off, the first digital-to-analog converter, the second digital-to-analog converter, the transimpedance amplifier, and the analog-to-digital converter all remain operational to perform the dynamic range extension calibration method.

[0015] As a further improvement of this application, the sensor is a photovolume change tracing sensor, which is used to measure blood oxygen saturation and / or heart rate.

[0016] As a further improvement to this application, this application also provides a calibration system for dynamic range extension, used to perform the above-described calibration method for dynamic range extension, the calibration system comprising: An execution unit is configured to respond to a dynamic range extension trigger signal, disconnect the photodetector from the analog front end, and turn off the light-emitting diode; A configuration unit is configured to configure the output current polarity of the second digital-to-analog converter to be opposite to the output current polarity of the first digital-to-analog converter; The first adjustment unit is used to adjust the input code value of the second digital-to-analog converter according to the binary division method until the second current matches the first current. The first acquisition unit is used to keep the adjusted input code value of the second digital-to-analog converter unchanged and acquire the first output value of the analog-to-digital converter; wherein, the first output value is the output voltage of the transimpedance amplifier of the first digital-to-analog converter at the first code value, and the first code value is the input code value of the first digital-to-analog converter when the dynamic range expansion is triggered; The second adjustment unit is used to adjust the input code value of the first digital-to-analog converter from the first code value to the second code value, while keeping the input code value of the second digital-to-analog converter unchanged; The second acquisition unit is used to acquire the second output value of the analog-to-digital converter, wherein the second output value is the output voltage of the transimpedance amplifier when the first digital-to-analog converter is at the second code value; The compensation unit is used to determine the amount of code value change caused by the change in the input code value of the first digital-to-analog converter based on the difference between the first output value and the second output value, and to add the amount of code value change to the original DC component code value.

[0017] This application provides a calibration method and system for dynamic range extension. Upon responding to a dynamic range extension trigger signal, the connection between the photodetector and the analog front-end is disconnected, and the light-emitting diode (LED) is turned off, ensuring no external photocurrent flows into the analog front-end during subsequent measurements, and the LED no longer consumes power. Based on this, the polarity of the output current of the second digital-to-analog converter (DAC) is reversed, and its input code value is adjusted using a binary division method to match the second current with the first current. Keeping the adjusted input code value of the second DAC unchanged, the first output value and the second output value of the first DAC under the first and second code values ​​are acquired sequentially. The change in code value caused by the change in the input code value of the first DAC is determined based on the difference between the first and second output values. This difference does not include the error introduced by the change in current transfer ratio. Finally, this change in code value is superimposed on the original DC component code value, thus completing the dynamic range extension calibration.

[0018] Throughout the calibration process, the LED remains off, avoiding the extra power consumption caused by lighting the LED every time the dynamic range expansion is triggered, as is the case in traditional solutions. At the same time, since the photodetector remains disconnected, the measurement results are not affected by changes in the current transfer ratio, ensuring the accuracy of the determined code value change and effectively improving the sensor's detection accuracy. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only a part of the embodiments of this application, and not all of the embodiments. For those skilled in the art, other drawings obtained from these drawings without creative effort are all within the scope of protection of this application.

[0020] Figure 1 A flowchart of a calibration method for dynamic range extension provided in an embodiment of this application.

[0021] Figure 2 This is a flowchart illustrating the process of setting intermediate code values ​​in the calibration method for dynamic range extension provided in this application embodiment.

[0022] Figure 3 This is a flowchart illustrating the adjustment of the current input code value of the second digital-to-analog converter in the calibration method for dynamic range extension provided in this application embodiment.

[0023] Figure 4 A flowchart illustrating the process of obtaining AC component code values ​​in the calibration method for dynamic range extension provided in this application embodiment.

[0024] Figure 5Figure 1 shows a first specific embodiment of the calibration method for dynamic range extension provided in this application.

[0025] Figure 6 Figure 1 shows a second specific embodiment of the calibration method for dynamic range extension provided in this application.

[0026] Figure 7 Figure 3 shows a third specific embodiment of the calibration method for dynamic range extension provided in this application.

[0027] Figure 8 A functional block diagram of the calibration system for dynamic range extension provided in the embodiments of this application. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0029] To make the description of this disclosure more detailed and complete, illustrative descriptions of the implementation methods and specific embodiments of this application are provided below; however, this is not the only form of implementing or utilizing the specific embodiments of this application. The implementation methods cover the features of multiple specific embodiments and the method steps and their order for constructing and operating these specific embodiments. However, other specific embodiments can also be used to achieve the same or equivalent functions and step sequences. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0030] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in sequences other than those illustrated or described herein.

[0031] In the description of the embodiments of this application, unless otherwise stated, " / " means "or". For example, A / B can mean A or B. The word "and / or" in the text is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, in the description of the embodiments of this application, "multiple" means two or more. Other quantifiers should be understood similarly. The preferred embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application. Furthermore, the embodiments of this application and the features in the embodiments can be combined with each other without conflict.

[0032] Photoplethysmography (PPG) is an optical measurement technique that measures blood oxygen saturation and heart rate by detecting changes in light absorption. A PPG sensor typically consists of an emitter and a receiver. The emitter comprises a light-emitting diode (LED) and its driving circuitry, used to emit light of a specific wavelength into human tissue. The receiver comprises a photodetector (PD) and signal processing circuitry, used to receive the light signal reflected or transmitted through human tissue and convert it into an electrical signal.

[0033] The analog front end (AFE) of a PPG sensor typically employs a trans-impedance amplifier (TIA) architecture to convert the photocurrent output from the photodetector into a voltage signal, which is then sampled and quantized by an analog-to-digital converter (ADC). To achieve a high signal-to-noise ratio, the TIA gain is usually configured to be high; however, due to limitations in the power supply voltage, the maximum allowable input current of the TIA is correspondingly reduced.

[0034] The photocurrent output by a photodetector consists mostly of ambient light and DC components, with only a small portion being AC components carrying physiological information. Therefore, current-mode digital-to-analog converters (DACs) are typically used in existing technologies to cancel out the ambient light and DC components in the photocurrent, thereby extending the dynamic range of the receiver. This technique is called Dynamic Range Extension (DRE).

[0035] In practical applications, the current transfer ratio (CTR) can dynamically change due to factors such as human movement, leading to significant fluctuations in the received photocurrent and making the photoanalyzer (TIA) prone to saturation. To avoid saturation, existing solutions dynamically adjust the current of the DAC (DC-DAC) used to cancel the DC component before the TIA saturates. However, the DC component canceled by the DC-DAC ultimately needs to be converted and superimposed back onto the ADC's output code value, and the linearity of the DC-DAC directly affects the accuracy of the ADC output.

[0036] Traditional dynamic range extension schemes typically use a method of lighting an LED and performing two measurements to obtain the change in the ADC code value corresponding to the change in the DC-DAC code value, and then update the DC component code value. However, this scheme has the following drawbacks: First, since the power consumption of the PPG sensor mainly comes from the LED (usually tens of milliamps), and the traditional solution requires the LED to be lit for measurement every time the DRE is adjusted, when the input signal changes frequently and the DRE trigger frequency is high, the system power consumption will increase significantly, affecting the device's battery life.

[0037] Second, the CTR may change dynamically between two measurements, causing the error introduced by the CTR change to be mixed into the difference of the measured ADC code value, rather than the pure DC-DAC code value change, thus affecting the linearity of the ADC output and reducing data quality.

[0038] In view of this, please refer to Figures 1-8 This application proposes a calibration method and system for dynamic range extension, which can complete dynamic range extension calibration without lighting up the light-emitting diode. At the same time, the calibration process is not affected by changes in the current transfer ratio, which significantly improves the detection accuracy of the sensor.

[0039] In an optional embodiment, the dynamic range extension calibration method provided in this application can be applied to a sensor, which includes a light-emitting diode, a photodetector, and an analog front-end coupled to the photodetector. The analog front-end includes a first digital-to-analog converter for outputting a first current, a second digital-to-analog converter for outputting a second current, a transimpedance amplifier, and an analog-to-digital converter coupled to the transimpedance amplifier.

[0040] Specifically, light-emitting diodes (LEDs) are used to emit light of specific wavelengths into human tissue, while photodetectors are used to receive the light signals reflected or transmitted through human tissue and convert them into photocurrent output. Since the photocurrent output by the photodetector contains ambient light components, DC components, and AC components carrying physiological information, directly amplifying the photocurrent containing these components can easily lead to saturation of the transimpedance amplifier, thus failing to effectively extract weak AC signals.

[0041] Therefore, this application provides a first digital-to-analog converter and a second digital-to-analog converter in the analog front end, wherein the first current output by the first digital-to-analog converter is used to cancel the DC component in the photocurrent output by the photodetector, and the second current output by the second digital-to-analog converter is used to cancel the ambient light component in the photocurrent output by the photodetector.

[0042] It should be noted that after the first and second currents are canceled out, the remaining photocurrent is mainly composed of an AC component and a small amount of residual DC component. This residual photocurrent is input to a transimpedance amplifier and converted into a voltage signal. Then, an analog-to-digital converter samples and quantizes this voltage signal to output the corresponding digital code value. This digital code value contains both the AC component code value and the residual DC component code value.

[0043] Based on this, please refer to Figure 1 Here is a flowchart of a calibration method for dynamic range extension provided in an embodiment of this application. The calibration method includes the following steps: Step S1: In response to the dynamic range extension trigger signal, disconnect the photodetector from the analog front end and turn off the light-emitting diode; In this embodiment, the dynamic range extension trigger signal is typically generated when the output voltage of the transimpedance amplifier approaches its saturation threshold. When the output voltage of the transimpedance amplifier approaches the saturation threshold, it indicates that the DC component in the photocurrent output by the photodetector is too large. At this time, it is necessary to adjust the input code value of the first digital-to-analog converter to increase the amount of cancellation of the first current, thereby preventing the transimpedance amplifier from entering saturation and ensuring the accuracy of subsequent signal acquisition.

[0044] Furthermore, after receiving the dynamic range extension trigger signal, the connection between the photodetector and the analog front end needs to be disconnected first. If the connection between the photodetector and the analog front end is maintained, the photocurrent output by the photodetector will continue to flow into the transimpedance amplifier. The DC component and ambient light component contained in this photocurrent will act together with the first current and the second current on the input of the transimpedance amplifier, causing the subsequent measurement results to be mixed with interference caused by the change in current transfer ratio.

[0045] Understandably, because the current transfer ratio changes dynamically under conditions such as human movement, this interference can cause the measured difference to fail to accurately reflect the change in code value corresponding to the change in the first current. Therefore, disconnecting the photodetector from the analog front end can isolate the externally input photocurrent from the measurement circuit inside the analog front end, ensuring that subsequent measurements are not affected by changes in the external photocurrent, and that the measurement results only reflect the changes in the current of the first digital-to-analog converter and the second digital-to-analog converter themselves.

[0046] Simultaneously with disconnection, the LEDs also need to be turned off. Since the PPG sensor's power consumption primarily comes from the LEDs, accounting for the majority of the system's total power consumption, keeping the LEDs lit for every dynamic range extension trigger would significantly increase power consumption when frequent input signal changes lead to a high dynamic range extension trigger frequency. Therefore, this application preferably turns off the LEDs during the adjustment process to avoid generating additional power consumption and thus reduce overall power consumption.

[0047] Step S2: Configure the output current polarity of the second digital-to-analog converter to be opposite to that of the output current polarity of the first digital-to-analog converter; In this embodiment, after disconnecting the photodetector from the analog front end and turning off the light-emitting diode, only the first digital-to-analog converter, the second digital-to-analog converter, the transimpedance amplifier, and the analog-to-digital converter remain in operation inside the analog front end.

[0048] At this time, the first digital-to-analog converter still outputs a first current, the magnitude of which corresponds to the first code value when dynamic range extension is triggered. Here, the first code value refers to the input code value of the first digital-to-analog converter when dynamic range extension is triggered.

[0049] Since the photodetector has been disconnected and there is no external photocurrent input, the first current flowing into the transimpedance amplifier alone will cause its output voltage to exceed the normal range, or even cause the transimpedance amplifier to enter saturation, thus making it impossible to perform subsequent measurement operations.

[0050] In an optional embodiment, this application introduces a second current output by a second digital-to-analog converter to cancel out the first current. The polarity of the output current of the second digital-to-analog converter is configured to be opposite to that of the output current of the first digital-to-analog converter. This ensures that after configuration, the second current and the first current form currents in opposite directions at the input of the transimpedance amplifier, and the two cancel each other out, thus preventing the transimpedance amplifier from entering a saturated state.

[0051] Step S3: Adjust the input code value of the second digital-to-analog converter according to the binary division method until the second current matches the first current; It is understandable that when the polarity of the output current of the second digital-to-analog converter is configured to be opposite in step S2, the second current and the first current form currents in opposite directions at the input of the transimpedance amplifier. However, the magnitude of the second current is still unknown at this time, and there may be a large difference between it and the first current.

[0052] In an optional embodiment, this application uses a binary search method to adjust the input code value of the second digital-to-analog converter, thereby quickly finding the input code value that matches the second current with the first current within a limited number of iterations.

[0053] As an optional implementation method, please refer to Figure 2 This is a flowchart illustrating the process of setting an intermediate code value in the dynamic range extension calibration method provided in this application embodiment. The above-mentioned adjustment of the input code value of the second digital-to-analog converter according to the binary search method until the second current matches the first current includes: Step S30: Set the input code value adjustment range of the second digital-to-analog converter, wherein the adjustment range has an upper limit code value and a lower limit code value; Step S31: Set the current input code value of the second digital-to-analog converter to the intermediate code value between the upper limit code value and the lower limit code value; Step S32: Adjust the current input code value of the second digital-to-analog converter based on the output voltage polarity of the transimpedance amplifier until the output voltage of the transimpedance amplifier is within a preset voltage threshold range, so that the second current matches the first current.

[0054] Before performing the binary search, it is necessary to set the input code value adjustment range of the second digital-to-analog converter. The input code value of the second digital-to-analog converter usually has an upper limit code value and a lower limit code value. The upper limit code value corresponds to the maximum current that the second digital-to-analog converter can output, and the lower limit code value corresponds to the minimum current that it can output.

[0055] Furthermore, after determining the upper and lower limit code values ​​of the adjustment range, the current input code value needs to be set to the middle code value between the upper and lower limit code values. This middle code value can be obtained by averaging the upper and lower limit code values. After setting the current input code value of the second digital-to-analog converter to this middle code value, the second digital-to-analog converter will output a second current corresponding to this middle code value.

[0056] It is understandable that the core of the binary search method is to use the intermediate code value as the current input code value, ensuring that the adjustment range is divided in half in each iteration. Compared with the search method of increasing or decreasing successively, the binary search method can significantly reduce the number of iterations and improve the adjustment efficiency. This application will not elaborate on the binary search method here.

[0057] In this embodiment of the application, after setting the current input code value to the intermediate code value, it is necessary to detect the polarity of the output voltage of the transimpedance amplifier, which reflects the magnitude relationship between the second current and the first current.

[0058] Specifically, since the second current has the opposite polarity to the first current, if the second current is greater than the first current, the output voltage of the transimpedance amplifier will be positive; if the second current is less than the first current, the output voltage of the transimpedance amplifier will be negative.

[0059] This application can determine whether the current second current is too large or too small based on the detected polarity of the output voltage of the transimpedance amplifier, so as to adjust the current input code value of the second digital-to-analog converter. When the output voltage of the transimpedance amplifier enters the preset voltage threshold range, it indicates that the difference between the second current and the first current is small enough, and it can be considered that the two have reached a matching state.

[0060] It should be noted that the above-mentioned preset voltage threshold range can be set according to actual accuracy requirements. For example, it can be set to the range where the output voltage of the transimpedance amplifier is close to zero volts. After matching is completed, the input code value of the second digital-to-analog converter is fixed, and the second current corresponding to the code value can basically cancel the first current.

[0061] As an optional implementation method, please refer to Figure 3 This is a flowchart illustrating the adjustment of the current input code value of the second digital-to-analog converter in the dynamic range extension calibration method provided in this application embodiment. The adjustment of the current input code value of the second digital-to-analog converter based on the output voltage polarity of the transimpedance amplifier includes: Step S320: If the output voltage of the transimpedance amplifier is positive, then update the upper limit code value of the adjustment range to the current input code value, and redetermine the middle code value between the upper limit code value and the lower limit code value as the new current input code value; Step S321: If the output voltage of the transimpedance amplifier is negative, then update the lower limit code value of the adjustment range to the current input code value, and re-determine the middle code value between the upper limit code value and the lower limit code value as the new current input code value.

[0062] In one specific embodiment, when the output voltage of the transimpedance amplifier is detected to be positive, it indicates that the second current corresponding to the current input code value is greater than the first current. Since the second current has the opposite polarity to the first current, a larger second current will cause the net current direction at the input of the transimpedance amplifier to be dominated by the second current, resulting in a positive output voltage. In this case, the second current needs to be reduced.

[0063] Furthermore, the upper limit code value of the adjustment range is updated to the current input code value. After updating the upper limit code value, the intermediate code value between the current upper limit code value and the original lower limit code value is recalculated and written as the new current input code value into the second digital-to-analog converter. Then, the polarity of the output voltage is detected again, and the above steps are repeated until the output voltage of the transimpedance amplifier is within the preset voltage threshold range. At this time, the second current corresponding to the code value can basically cancel the first current.

[0064] When the output voltage of the transimpedance amplifier is detected to be negative, it indicates that the second current corresponding to the current input code value is less than the first current. Since the second current has the opposite polarity to the first current, a smaller second current will cause the net current direction at the input of the transimpedance amplifier to be dominated by the first current, resulting in a negative output voltage. In this case, the second current needs to be increased.

[0065] Therefore, the lower limit code value of the adjustment range needs to be updated to the current input code value. After updating the lower limit code value, the intermediate code value between the current upper limit code value and the new lower limit code value is recalculated and written as the new current input code value into the second digital-to-analog converter. Then, the polarity of the output voltage is detected again, and the above steps are repeated until the output voltage of the transimpedance amplifier is within the preset voltage threshold range. At this time, the second current corresponding to the code value can basically cancel the first current.

[0066] Step S4: Keep the adjusted input code value of the second digital-to-analog converter unchanged, and obtain the first output value of the analog-to-digital converter; wherein, the first output value is the output voltage of the transimpedance amplifier of the first digital-to-analog converter at the first code value, and the first code value is the input code value of the first digital-to-analog converter when the dynamic range expansion is triggered; In this embodiment of the application, when the input code value of the second digital-to-analog converter is adjusted by the binary division method so that the second current and the first current are matched, the input code value of the second digital-to-analog converter will be determined and fixed.

[0067] At the same time, the first digital-to-analog converter still maintains the first code value when triggering dynamic range expansion, that is, the magnitude of the first current is the same as the moment of response to the dynamic range expansion trigger signal. Since the second current is basically equal to the first current and has opposite polarity, the two cancel each other out at the input of the transimpedance amplifier. The net current flowing into the transimpedance amplifier should theoretically be close to zero, and the output voltage of the transimpedance amplifier should also be close to zero.

[0068] However, due to limitations in circuit noise and the accuracy of the binary search, the second current cannot be absolutely equal to the first current; there will always be a small residual current. This residual current flows into the transimpedance amplifier and is converted into a small voltage output by the transimpedance gain. This voltage is the actual output voltage of the transimpedance amplifier in its current state.

[0069] In an optional embodiment, the present application samples and quantizes the minute voltage using an analog-to-digital converter to obtain a first output value, which essentially reflects the magnitude of the residual voltage caused by the incomplete equality of the second current and the first current when the second current matches the first current.

[0070] It is understandable that when the first output value is obtained, the photodetector remains disconnected and the light-emitting diode remains off. Therefore, the measurement result is completely unaffected by changes in external photocurrent and depends only on the state of the first digital-to-analog converter, the second digital-to-analog converter, and the transimpedance amplifier within the analog front end.

[0071] Step S5: Adjust the input code value of the first digital-to-analog converter from the first code value to the second code value, while keeping the input code value of the second digital-to-analog converter unchanged; In this embodiment of the application, in order to measure the amount of code value change caused by the change of the input code value of the first digital-to-analog converter, it is necessary to adjust the input code value of the first digital-to-analog converter from the first code value to the second code value.

[0072] During the adjustment process, the input code value of the second digital-to-analog converter remains unchanged as determined in step S3, that is, the magnitude of the second current remains unchanged, and the change in the output voltage of the transimpedance amplifier is observed only by changing the first current.

[0073] As an optional implementation, the second code value is the sum of the first code value and the preset code value change, and the current change of the first digital-to-analog converter corresponding to the preset code value change is less than the full-scale input current of the transimpedance amplifier.

[0074] In practical applications, the specific value of the second code value can be set as needed. For example, the second code value can be set as the sum of the changes in the first code value and the preset code value.

[0075] It should be noted that the full-scale input current of the transimpedance amplifier refers to the maximum current value that its input terminal can accept without causing the transimpedance amplifier to saturate. Therefore, the current change of the first digital-to-analog converter corresponding to the preset code value change must be less than the full-scale input current of the transimpedance amplifier. If the change of the first current exceeds the full-scale input current of the transimpedance amplifier, it will cause the transimpedance amplifier to saturate, and a valid second output value cannot be obtained.

[0076] As an optional implementation, the current change of the first digital-to-analog converter corresponding to the aforementioned preset code value change is less than half of the full-scale input current of the transimpedance amplifier.

[0077] As a more preferred implementation, the current change corresponding to the preset code value change can be further limited to less than half of the full-scale input current of the transimpedance amplifier, thereby providing sufficient safety margin for measurement.

[0078] Furthermore, in some specific application examples, the trigger threshold for dynamic range extension can also be set to half of the full-scale input current of the transimpedance amplifier. When the output voltage of the transimpedance amplifier reaches this trigger threshold, it indicates that the net current flowing into the transimpedance amplifier is close to half of the full-scale input current. At this point, dynamic range extension is initiated, and the input code value of the first digital-to-analog converter is adjusted. Of course, this is only one optional implementation method and is not a limitation on the scope of protection of this application.

[0079] Step S6: Obtain the second output value of the analog-to-digital converter, wherein the second output value is the output voltage of the transimpedance amplifier when the first digital-to-analog converter is at the second code value; In this embodiment of the application, when the input code value of the first digital-to-analog converter is adjusted from the first code value to the second code value, the first current output by the first digital-to-analog converter changes accordingly, while the second current remains unchanged. Since the polarity of the second current is opposite to that of the first current, the net current flowing into the transimpedance amplifier is the difference between the second current and the adjusted first current. This net current is converted into a voltage output by the transimpedance amplifier.

[0080] Furthermore, the output voltage needs to be sampled and quantized by an analog-to-digital converter to obtain a second output value. This second output value corresponds to the output voltage of the transimpedance amplifier when the first digital-to-analog converter is in the second code value state, and is a specific digital code value.

[0081] Similar to the first output value obtained in step S4, the second output value is also measured with the photodetector disconnected and the light-emitting diode turned off. Therefore, it is completely unaffected by changes in external photocurrent and depends only on the state of the first digital-to-analog converter, the second digital-to-analog converter, and the transimpedance amplifier inside the analog front end.

[0082] Based on this, since the adjusted first current is different from the original first current, while the second current remains unchanged, the magnitude of the second output value depends on the difference between the second current and the adjusted first current.

[0083] Step S7: Based on the difference between the first output value and the second output value, determine the amount of code value change caused by the change in the input code value of the first digital-to-analog converter, and add the amount of code value change to the original DC component code value.

[0084] In steps S4 and S6, the first output value and the second output value are obtained respectively. The first output value is measured when the first digital-to-analog converter is in the state of the first code value and the second digital-to-analog converter is in the state of the adjusted code value, and the output voltage of the transimpedance amplifier is the difference between the second current and the first current. The second output value is measured when the first digital-to-analog converter is adjusted to the second code value and the second digital-to-analog converter is kept in the same code value state, and the output voltage of the transimpedance amplifier is the difference between the second current and the adjusted first current.

[0085] Since the photodetector remains disconnected and the LED is kept off throughout the measurement process, the measurement results are completely unaffected by changes in external photocurrent. Therefore, the change in code value is purely caused by the change in the input code value of the first digital-to-analog converter and does not include any interference from changes in the current transfer ratio. Simultaneously, since the input code value of the second digital-to-analog converter remains constant during the measurement process, and the second current serves as a fixed reference current, its nonlinearity will not affect the measurement results.

[0086] Based on this, the difference between the first output value and the second output value can accurately reflect the change in code value corresponding to the change in current caused by the change in the input code value of the first digital-to-analog converter from the first code value to the second code value.

[0087] Furthermore, after obtaining the change in the code value, it needs to be superimposed on the original DC component code value. Here, the original DC component code value is a digital code value used to characterize the magnitude of the DC component canceled by the first current before the dynamic range extension is triggered.

[0088] When the dynamic range extension is triggered, the input code value of the first digital-to-analog converter needs to be adjusted from the first code value to the second code value. The magnitude of the DC component canceled by the first current also changes accordingly. Therefore, the original DC component code value is no longer applicable. The measured code value change is superimposed on the original DC component code value to obtain the updated DC component code value.

[0089] It should be noted that the preset code value change is customized in actual use. It determines the change range of the input code value of the first digital-to-analog converter. The difference between the first output value and the second output value reflects the actual voltage change caused by the change of the first current at the output of the analog-to-digital converter within the interval from the first code value to the second code value. No matter how large or small the preset code value change is, as long as it is within the linear range of the transimpedance amplifier, it can reflect the true mapping of the change of the first current within the code value interval.

[0090] As an optional implementation, the first current is used to cancel the DC component in the output photocurrent of the photodetector, and the second current is used to cancel the ambient light component in the output photocurrent of the photodetector. The original DC component code value is the digital code value corresponding to the DC component canceled by the first current before the dynamic range extension is triggered.

[0091] It is understandable that in practical applications, the photocurrent output by a photodetector is usually composed of three parts: ambient light component, DC component, and AC component. The ambient light component comes from external ambient light, the DC component comes from static reflection or transmission light after the light-emitting diode irradiates human tissue, and the AC component comes from changes in blood volume caused by heartbeat.

[0092] In order to extract the pure AC component from the photocurrent, the ambient light component and the DC component need to be canceled in the analog front end. The first current output by the first digital-to-analog converter can cancel the DC component, and similarly, the second current output by the second digital-to-analog converter can cancel the ambient light component. Through the cancellation effect of the first current and the second current, the net current flowing into the transimpedance amplifier is mainly left with the AC component and a small amount of residual DC component that has not been completely canceled.

[0093] The original DC component code value is a digital code value stored in the system before the dynamic range extension is triggered. This code value is used to characterize the magnitude of the DC component canceled by the first current before triggering. This code value can be obtained through initial calibration or stored after the last dynamic range extension update. After the dynamic range extension is triggered, the original DC component code value needs to be updated because the input code value of the first digital-to-analog converter needs to be adjusted, so that the AC component can be accurately extracted from the analog-to-digital converter output value in subsequent signal processing.

[0094] As an optional implementation method, please refer to Figure 4 The flowchart illustrates the process of obtaining the AC component code value in the dynamic range extension calibration method provided in this application embodiment. After superimposing the code value change onto the original DC component code value, the method further includes: Step S80: Reconnect the photodetector to the analog front end and turn the light-emitting diode back on; Step S81: Control the first digital-to-analog converter to output a first current to cancel the DC component in the output photocurrent of the photodetector, and control the second digital-to-analog converter to output a second current to cancel the ambient light component in the output photocurrent of the photodetector. Step S82: Obtain the digital code value output by the analog-to-digital converter, wherein the digital code value is the sum of the AC component and the residual DC component in the output photocurrent; Step S83: Compensate the digital code value based on the updated DC component code value to obtain the AC component code value corresponding to the AC component in the output photocurrent.

[0095] After completing the dynamic range extension calibration and updating the DC component code value, the sensor needs to be restored to normal operating status to continue acquiring and processing PPG signals.

[0096] In this embodiment, during calibration, the connection between the photodetector and the analog front end is disconnected, and the light-emitting diode is turned off to isolate the influence of external photocurrent. After calibration, these connections and operations need to be restored so that the sensor can continue to acquire signals.

[0097] Furthermore, after restoring the connection between the photodetector and the analog front end, the photocurrent output by the photodetector can flow normally into the analog front end; after the light-emitting diode is turned on again, the light-emitting diode emits light signals to irradiate human tissue again, thereby generating a photocurrent containing physiological information.

[0098] After resuming normal operation, the first digital-to-analog converter outputs a corresponding first current based on the updated DC component code value to cancel the DC component in the photocurrent output by the photodetector; the second digital-to-analog converter outputs a second current to cancel the ambient light component in the photocurrent output by the photodetector. After the cancellation effect of these two currents, the net current flowing into the transimpedance amplifier is mainly the AC component and a small amount of residual DC component that was not completely canceled.

[0099] Based on this, the transimpedance amplifier converts the net current into a voltage, and the analog-to-digital converter samples and quantizes the voltage to output the corresponding digital code value, so that physiological parameters such as heart rate and blood oxygen saturation can be calculated based on the digital code value.

[0100] As an optional implementation, the digital code value output by the analog-to-digital converter contains a residual DC component. If this digital code value is directly used for physiological parameter calculations, the residual DC component will act as an error term, affecting the accuracy of the calculation results. Therefore, it is necessary to remove the portion corresponding to the residual DC component from the digital code value to obtain a pure AC component code value.

[0101] Since the updated DC component code value accurately reflects the corresponding value of the DC component canceled by the current first current in the digital domain, and the residual DC component is the part of the DC component that was not completely canceled, there is a definite correspondence between the updated DC component code value and the residual DC component code value.

[0102] In an optional embodiment, the digital code value output by the analog-to-digital converter can be compensated based on the updated DC component code value. For example, the updated DC component code value can be subtracted from the digital code value output by the analog-to-digital converter, or the updated DC component code value can be accurately corrected according to the correspondence between the updated DC component code value and the residual DC component. This can eliminate the influence of the residual DC component and obtain the code value corresponding to the pure AC component.

[0103] The final obtained AC component code value represents the PPG signal that changes with the heartbeat. It can be used for subsequent calculation and analysis of physiological parameters such as heart rate and blood oxygen saturation, ensuring the accuracy and stability of physiological parameter detection results and meeting the actual application needs of wearable health monitoring devices.

[0104] As an optional implementation, under normal operating conditions, the first digital-to-analog converter, the second digital-to-analog converter, and the transimpedance amplifier are all coupled to the photodetector; When the connection between the photodetector and the analog front end is disconnected and the light-emitting diode is turned off, the first digital-to-analog converter, the second digital-to-analog converter, the transimpedance amplifier, and the analog-to-digital converter all remain operational to perform the dynamic range extension calibration method.

[0105] Under normal operating conditions, the photocurrent output by the photodetector needs to flow into the analog front end for processing. Therefore, the first digital-to-analog converter, the second digital-to-analog converter, and the transimpedance amplifier are all coupled to the photodetector. At this time, the first current is used to cancel the DC component in the photocurrent, and the second current is used to cancel the ambient light component in the photocurrent. The net current after cancellation is converted into voltage by the transimpedance amplifier, and then sampled and quantized by the analog-to-digital converter. Finally, a digital code value containing AC component and residual DC component is output. This is the working mode of the sensor performing normal physiological signal acquisition.

[0106] When dynamic range extension is triggered, to isolate the influence of external photocurrent changes on the calibration process, it is necessary to disconnect the photodetector from the analog front end and turn off the LED. However, it is important to note that after disconnecting the connection and turning off the LED, other circuit modules inside the analog front end, including the first digital-to-analog converter, the second digital-to-analog converter, the transimpedance amplifier, and the analog-to-digital converter, continue to operate to perform the steps of the dynamic range extension calibration method described above.

[0107] Meanwhile, turning off the LEDs can avoid generating additional power consumption during the calibration process, and disconnecting the photodetector can ensure that the measurement results are not affected by changes in external photocurrent.

[0108] As an optional implementation, the sensor is a photovolume chromatogram sensor, which is used to measure blood oxygen saturation and / or heart rate.

[0109] Photovolume plethysmography (PVP) is an optical measurement technique that measures physiological parameters by detecting changes in light absorption. Its basic principle is as follows: a light-emitting diode (LED) emits light of a specific wavelength to illuminate human tissue, and a photodetector receives the light signal reflected or transmitted through the tissue. Due to the periodic changes in blood volume caused by heartbeats, the amount of light absorbed also changes periodically, resulting in an AC component synchronized with the heartbeat in the photocurrent output by the photodetector. By analyzing this AC component, physiological parameters such as heart rate and blood oxygen saturation can be calculated.

[0110] The calibration method provided in this application embodiment is designed for this application scenario. When the current transmission ratio changes due to human movement or other reasons, and the original DC component offset current is no longer suitable for the current situation, the sensor needs to adjust the input code value of the first digital-to-analog converter to match the new DC component level.

[0111] This application can complete calibration without lighting up the LED, significantly reducing system power consumption; at the same time, the calibration process is not affected by changes in the current transfer ratio, ensuring the accuracy of subsequent heart rate and blood oxygen saturation calculations, thereby effectively improving the battery life and data quality of wearable health monitoring devices.

[0112] Finally, please see Figures 5 to 7 The figures shown are a first embodiment, a second embodiment, and a third embodiment of the calibration method for dynamic range extension provided in this application.

[0113] In one specific embodiment provided in this application, please continue to refer to... Figure 5 The sensor includes a light-emitting diode, a photodetector, and an analog front-end coupled to the photodetector. The analog front-end includes a first digital-to-analog converter (DC-DAC in the figure) for outputting a first current, a second digital-to-analog converter (AMB-DAC in the figure) for outputting a second current, a transimpedance amplifier (TIA), and an analog-to-digital converter (ADC) coupled to the transimpedance amplifier.

[0114] Please continue reading Figure 6 When the output voltage of the transimpedance amplifier reaches the dynamic range extension trigger threshold dre_th, it indicates that the DC component in the current photocurrent is too large. It is necessary to increase the amount of the first current cancellation by adjusting the input code value of the first digital-to-analog converter, thereby avoiding transimpedance amplifier saturation. At this time, the dynamic range extension calibration process is initiated.

[0115] First, in response to the dynamic range extension trigger signal, the connection between the photodetector and the analog front end is disconnected, and the light-emitting diode is turned off. At this time, the first digital-to-analog converter, the second digital-to-analog converter, the transimpedance amplifier, and the analog-to-digital converter are in operation. The input code value of the first digital-to-analog converter maintains the first code value dc_dac_din0 when the dynamic range extension is triggered, and the first current Idc0 is output.

[0116] Since there is no photocurrent input from the photodetector at this time, the Idc0 flowing into the transimpedance amplifier alone will cause its output voltage to exceed the normal range, or even cause the transimpedance amplifier to enter saturation. Therefore, it is necessary to introduce a second current output from the second digital-to-analog converter to cancel out the first current.

[0117] Next, the polarity of the output current of the second digital-to-analog converter is configured to be opposite to that of the output current of the first digital-to-analog converter. With this configuration, the second current and the first current form opposite currents at the input of the transimpedance amplifier, thus canceling each other out.

[0118] Furthermore, the input code value of the second digital-to-analog converter is adjusted according to the binary division method to obtain an input code value that makes the output current Iamb of the second digital-to-analog converter close to the first current Idc0. When the output voltage of the transimpedance amplifier approaches zero, it indicates that Iamb and Idc0 are basically equal. At this time, the second current and the first current reach a matching state.

[0119] After matching is completed, the input code value of the second digital-to-analog converter remains unchanged after adjustment, and the first output value of the analog-to-digital converter is obtained. At this time, the input code value of the first digital-to-analog converter is still the first code value dc_dac_din0 when the dynamic range extension is triggered, and the first current Idc0 is output. The second digital-to-analog converter continues to output Iamb obtained in the first step, and the transimpedance amplifier output voltage is vo_tia0=Gain×(Iamb-Idc0). The analog-to-digital converter samples and quantizes this voltage to obtain the first output value adc_data_tia0.

[0120] Next, please continue to see Figure 7 The input code value of the first digital-to-analog converter is adjusted from the first code value to the second code value, while keeping the input code value of the second digital-to-analog converter unchanged. For example, the input code value of the first digital-to-analog converter is adjusted to dc_dac_din1=dc_dac_din0+Δdc_dac_din, and the first current Idc1 is output; the second digital-to-analog converter continues to output Iamb obtained in the first step.

[0121] Wherein, Δdc_dac_din represents the preset code value change amount, which can be freely adjusted as needed, but its corresponding first current change amount ΔIdc must be less than the full-scale input current of the transimpedance amplifier.

[0122] In a preferred implementation, the trigger threshold dre_th and Δdc_dac_din are both set to half of the full-scale input current of the transimpedance amplifier. At this time, the output voltage of the transimpedance amplifier is vo_tia1=Gain×(Iamb-Idc1). The analog-to-digital converter samples and quantizes this voltage to obtain the second output value adc_data_tia1.

[0123] Finally, based on the difference between the first and second output values, the amount of code value change caused by the change in the input code value of the first digital-to-analog converter is determined, and this amount of code value change is added to the original DC component code value. Since the photodetector is in an off state throughout the entire process and the light-emitting diode is also kept off, the measurement results are completely unaffected by changes in external photocurrent and current transfer ratio.

[0124] The difference between the first output value and the second output value (adc_data_tia1-adc_data_tia0) can accurately reflect the change in the analog-to-digital converter code value corresponding to the change in the first digital-to-analog converter code value (Δdc_dac_din), and this change in code value corresponds precisely to the change in the first current ΔIdc.

[0125] Furthermore, the change in this code value is superimposed on the original adc_data_dc0 to obtain the updated DC component code value adc_data_dc1=adc_data_dc0+(adc_data_tia1-adc_data_tia0). This updated DC component code value accurately reflects the corresponding value of the canceled DC component in the digital domain when the first digital-to-analog converter is in the second code value dc_dac_din1.

[0126] After calibration, the connection between the photodetector and the analog front end is restored, and the LEDs are turned back on to return the sensor to normal operating condition. In normal operating condition, the first digital-to-analog converter (DAC) outputs a first current to cancel the DC component in the photodetector's output photocurrent, and the second DAC outputs a second current to cancel the ambient light component in the photodetector's output photocurrent. The digital code value output by the DAC corresponds to the sum of the AC component and the residual DC component in the output photocurrent. Based on the updated DC component code value, this digital code value is compensated; for example, subtracting the updated DC component code value from the digital code value yields the code value corresponding to the pure AC component, which is used for subsequent calculations of physiological parameters such as heart rate and blood oxygen saturation.

[0127] Based on the calibration method described above for dynamic range extension, please refer to [link / reference]. Figure 8The diagram shows the functional blocks of the dynamic range extended calibration system provided in this application. This application also provides a dynamic range extended calibration system, which includes: An execution unit is configured to respond to a dynamic range extension trigger signal, disconnect the photodetector from the analog front end, and turn off the light-emitting diode; A configuration unit is configured to configure the output current polarity of the second digital-to-analog converter to be opposite to the output current polarity of the first digital-to-analog converter; The first adjustment unit is used to adjust the input code value of the second digital-to-analog converter according to the binary division method until the second current matches the first current. The first acquisition unit is used to keep the adjusted input code value of the second digital-to-analog converter unchanged and acquire the first output value of the analog-to-digital converter; wherein, the first output value is the output voltage of the transimpedance amplifier of the first digital-to-analog converter at the first code value, and the first code value is the input code value of the first digital-to-analog converter when the dynamic range expansion is triggered; The second adjustment unit is used to adjust the input code value of the first digital-to-analog converter from the first code value to the second code value, while keeping the input code value of the second digital-to-analog converter unchanged; The second acquisition unit is used to acquire the second output value of the analog-to-digital converter, wherein the second output value is the output voltage of the transimpedance amplifier when the first digital-to-analog converter is at the second code value; The compensation unit is used to determine the amount of code value change caused by the change in the input code value of the first digital-to-analog converter based on the difference between the first output value and the second output value, and to add the amount of code value change to the original DC component code value.

[0128] For further details regarding the implementation of the above-mentioned dynamic range extended calibration system, please refer to the description of the dynamic range extended calibration method provided in the above-mentioned application embodiments, which will not be repeated here.

[0129] This application provides a calibration method and system for dynamic range extension. Upon responding to a dynamic range extension trigger signal, the connection between the photodetector and the analog front-end is disconnected, and the light-emitting diode (LED) is turned off, ensuring no external photocurrent flows into the analog front-end during subsequent measurements, and the LED no longer consumes power. Based on this, the polarity of the output current of the second digital-to-analog converter (DAC) is reversed, and its input code value is adjusted using a binary division method to match the second current with the first current. Keeping the adjusted input code value of the second DAC unchanged, the first output value and the second output value of the first DAC under the first and second code values ​​are acquired sequentially. The change in code value caused by the change in the input code value of the first DAC is determined based on the difference between the first and second output values. This difference does not include the error introduced by the change in current transfer ratio. Finally, this change in code value is superimposed on the original DC component code value, thus completing the dynamic range extension calibration.

[0130] Throughout the calibration process, the LED remains off, avoiding the extra power consumption caused by lighting the LED every time the dynamic range expansion is triggered, as is the case in traditional solutions. At the same time, since the photodetector remains disconnected, the measurement results are not affected by changes in the current transfer ratio, ensuring the accuracy of the determined code value change and effectively improving the sensor's detection accuracy.

[0131] It should be noted that, in the several embodiments provided in this application, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed between each other can be through some interfaces, or indirect coupling or communication connection between devices or units, and can be electrical, mechanical, or other forms.

[0132] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0133] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A calibration method for dynamic range extension, applied to a sensor, the sensor comprising a light-emitting diode, a photodetector, and an analog front-end coupled to the photodetector, the analog front-end comprising a first digital-to-analog converter for outputting a first current, a second digital-to-analog converter for outputting a second current, a transimpedance amplifier, and an analog-to-digital converter coupled to the transimpedance amplifier, characterized in that, The calibration method includes the following steps: In response to the dynamic range extension trigger signal, the connection between the photodetector and the analog front end is disconnected, and the light-emitting diode is turned off; The polarity of the output current of the second digital-to-analog converter is configured to be opposite to that of the output current of the first digital-to-analog converter; The input code value of the second digital-to-analog converter is adjusted according to the binary division method until the second current matches the first current; Keeping the adjusted input code value of the second digital-to-analog converter unchanged, the first output value of the analog-to-digital converter is obtained; wherein, the first output value is the output voltage of the transimpedance amplifier of the first digital-to-analog converter at the first code value, and the first code value is the input code value of the first digital-to-analog converter when the dynamic range expansion is triggered; The input code value of the first digital-to-analog converter is adjusted from the first code value to the second code value, while the input code value of the second digital-to-analog converter remains unchanged; Obtain the second output value of the analog-to-digital converter, wherein the second output value is the output voltage of the transimpedance amplifier when the first digital-to-analog converter is at the second code value; Based on the difference between the first output value and the second output value, the amount of code value change caused by the change in the input code value of the first digital-to-analog converter is determined, and the amount of code value change is superimposed on the original DC component code value.

2. The calibration method for dynamic range extension as described in claim 1, characterized in that, The step of adjusting the input code value of the second digital-to-analog converter according to the binary search method until the second current matches the first current includes: The input code value adjustment range of the second digital-to-analog converter is set, and the adjustment range has an upper limit code value and a lower limit code value; Set the current input code value of the second digital-to-analog converter to the middle code value between the upper limit code value and the lower limit code value; The current input code value of the second digital-to-analog converter is adjusted based on the polarity of the output voltage of the transimpedance amplifier until the output voltage of the transimpedance amplifier is within a preset voltage threshold range, so that the second current matches the first current.

3. The calibration method for dynamic range extension as described in claim 2, characterized in that, The adjustment of the current input code value of the second digital-to-analog converter based on the output voltage polarity of the transimpedance amplifier includes: If the output voltage of the transimpedance amplifier is positive, then the upper limit code value of the adjustment range is updated to the current input code value, and the middle code value between the upper limit code value and the lower limit code value is re-determined as the new current input code value. If the output voltage of the transimpedance amplifier is negative, the lower limit code value of the adjustment range is updated to the current input code value, and the intermediate code value between the upper limit code value and the lower limit code value is redefined as the new current input code value.

4. The calibration method for dynamic range extension as described in claim 1, characterized in that, The second code value is the sum of the change in the first code value and the preset code value, and the change in current of the first digital-to-analog converter corresponding to the preset code value change is less than the full-scale input current of the transimpedance amplifier.

5. The calibration method for dynamic range extension as described in claim 4, characterized in that, The change in current of the first digital-to-analog converter corresponding to the preset code value change is less than half of the full-scale input current of the transimpedance amplifier.

6. The calibration method for dynamic range extension as described in claim 1, characterized in that, The first current is used to cancel the DC component in the output photocurrent of the photodetector, and the second current is used to cancel the ambient light component in the output photocurrent of the photodetector. The original DC component code value is the digital code value corresponding to the DC component canceled by the first current before the dynamic range extension is triggered.

7. The calibration method for dynamic range extension as described in claim 6, characterized in that, After adding the code value change to the original DC component code value, the method further includes: Reconnect the photodetector to the analog front end and turn the light-emitting diode back on; The first digital-to-analog converter is controlled to output a first current to cancel the DC component in the output photocurrent of the photodetector, and the second digital-to-analog converter is controlled to output a second current to cancel the ambient light component in the output photocurrent of the photodetector. Obtain the digital code value output by the analog-to-digital converter, wherein the digital code value is the sum of the AC component and the residual DC component in the output photocurrent; The digital code value is compensated based on the updated DC component code value to obtain the AC component code value corresponding to the AC component in the output photocurrent.

8. The calibration method for dynamic range extension as described in claim 1, characterized in that, Under normal operating conditions, the first digital-to-analog converter, the second digital-to-analog converter, and the transimpedance amplifier are all coupled to the photodetector; When the connection between the photodetector and the analog front end is disconnected and the light-emitting diode is turned off, the first digital-to-analog converter, the second digital-to-analog converter, the transimpedance amplifier, and the analog-to-digital converter all remain operational to perform the dynamic range extension calibration method.

9. The calibration method for dynamic range extension as described in claim 1, characterized in that, The sensor is a photovolume change tracing sensor, which is used to measure blood oxygen saturation and / or heart rate.

10. A calibration system with extended dynamic range, characterized in that, For performing the calibration method for dynamic range extension as described in any one of claims 1-9, the calibration system comprises: An execution unit is configured to respond to a dynamic range extension trigger signal, disconnect the photodetector from the analog front end, and turn off the light-emitting diode; A configuration unit is configured to configure the output current polarity of the second digital-to-analog converter to be opposite to the output current polarity of the first digital-to-analog converter; The first adjustment unit is used to adjust the input code value of the second digital-to-analog converter according to the binary division method until the second current matches the first current. The first acquisition unit is used to keep the adjusted input code value of the second digital-to-analog converter unchanged and acquire the first output value of the analog-to-digital converter; wherein, the first output value is the output voltage of the transimpedance amplifier of the first digital-to-analog converter at the first code value, and the first code value is the input code value of the first digital-to-analog converter when the dynamic range expansion is triggered; The second adjustment unit is used to adjust the input code value of the first digital-to-analog converter from the first code value to the second code value, while keeping the input code value of the second digital-to-analog converter unchanged; The second acquisition unit is used to acquire the second output value of the analog-to-digital converter, wherein the second output value is the output voltage of the transimpedance amplifier when the first digital-to-analog converter is at the second code value; The compensation unit is used to determine the amount of code value change caused by the change in the input code value of the first digital-to-analog converter based on the difference between the first output value and the second output value, and to add the amount of code value change to the original DC component code value.

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