Electronic device with ambient flicker detection

Abstract

The invention relates to an electronic device with ambient flicker detection. More specifically, an electronic device may have a sensor to measure environmental flicker. The sensor may be a sigma-delta converter. The flicker may be calculated based on a voltage output of the sigma-delta converter and a number of times the sigma-delta converter is triggered during a predetermined period of time, thereby reducing the voltage output. In particular, the flicker may be determined using a fast Fourier transform (FFT) on the values. Filtering and / or non-uniform sampling may be combined if desired to avoid aliasing. In addition or alternatively, Lomb-Scargle spectroscopic analysis may be used to prevent attenuation of the measured flicker signal. As an alternative to using a sigma-delta converter to determine ambient flicker, a folded capacitive transimpedance amplifier (C-TIA) circuit or a circuit having an analog-to-digital converter and a digital filter may be used to measure the ambient flicker.

Description

[0001] This application claims priority to U.S. Patent Application No. 18 / 613,515 filed on March 22, 2024, which claims the benefit of U.S. Provisional Patent Application No. 63 / 578,632 filed on August 24, 2023, which applications are hereby incorporated by reference in their entirety. Technical Field

[0002] This document relates generally to electronic devices and, more particularly, to electronic devices having sensors. Background Art

[0003] Electronic devices such as laptop computers, cellular phones, and other equipment are sometimes provided with sensors. For example, sensors may be incorporated into the device to provide information about current environmental conditions or device conditions to the device. Summary of the invention

[0004] An electronic device may have one or more sensors to measure ambient flicker. The sensor may include a sigma-delta converter. The sigma-delta converter may include a photodiode that generates charge in response to ambient light and a capacitor that reduces the output voltage when the output voltage exceeds a threshold. The flicker may be calculated based on the voltage output of the sigma-delta converter and the number of times the sigma-delta converter is triggered (e.g., the output voltage has decreased) during a predetermined period of time. Specifically, a fast Fourier transform (FFT) may be applied to these values ​​to determine the flicker.

[0005] If desired, filtering and / or non-uniform sampling may be incorporated to avoid aliasing. Additionally or alternatively, Lomb-Scargle spectral analysis may be used to prevent attenuation of the measured scintillation signal.

[0006] As an alternative to using a sigma-delta converter to determine ambient flicker, a folded capacitive transimpedance amplifier (C-TIA) circuit can be used to measure the ambient flicker. The folded capacitive transimpedance amplifier (C-TIA) circuit can measure flicker using the same steps as the sigma-delta converter, but can use a folding circuit triggered by timing and logic circuits to cause the voltage reduction to occur.

[0007] In other embodiments, a circuit combining a digital filter and a current source set by the digital filter can be used to measure ambient flicker. Specifically, the digital filter can set the current source to match the current generated by the photodiode, and the flicker portion can be determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a schematic diagram of an illustrative electronic device with a display and sensor components according to some embodiments.

[0009] Figure 2is a perspective view of an electronic device with a sensor according to some embodiments.

[0010] Figure 3 is a diagram of an exemplary sigma-delta converter, according to some implementations.

[0011] Figure 4 is a diagram of exemplary waveforms generated by a sigma-delta converter, according to some embodiments.

[0012] Figure 5 is a flow chart of illustrative steps that may be used to determine ambient light flicker according to some implementations.

[0013] FIG. 6A to FIG. 6C According to some embodiments, Figure 5 An exemplary graph for determining ambient light flicker is generated by the steps of FIG.

[0014] Figure 7 is an exemplary spectrum including a peak band indicating ambient flicker and an aliasing band according to some embodiments.

[0015] Fig. 8A and Figure 8B An illustrative example of using non-uniform sampling to mitigate aliasing is shown in accordance with some embodiments.

[0016] Fig. 9 is a diagram of an exemplary folded capacitor transimpedance amplifier (C-TIA) circuit, according to some implementations.

[0017] Fig.10 is an illustration of an exemplary timing diagram that may be used for a C-TIA circuit, according to some embodiments.

[0018] Fig.11 is a flow chart of illustrative steps that may be used to reconstruct a signal from a C-TIA circuit, according to some embodiments.

[0019] Fig.12 is a diagram of an illustrative ambient flicker detection circuit including a digital filter and a constant current source according to some embodiments. DETAILED DESCRIPTION

[0020] An electronic device may include one or more environmental sensors, such as an ambient light sensor and a camera. It may be desirable to determine the flicker of an ambient light source. For example, flicker may be measured and used to avoid potential problems with images and / or videos captured by a camera in the device.

[0021] To determine ambient flicker, a sigma-delta converter may be used to measure ambient light. The sigma-delta converter may include a photodiode that generates a charge in response to ambient light and a capacitor that reduces an output voltage when the voltage of the generated charge exceeds a threshold. Flicker may be determined based on the voltage output of the sigma-delta converter and the number of times the sigma-delta converter is triggered (e.g., the voltage is reduced) during a predetermined period of time. Specifically, a fast Fourier transform (FFT) may be applied to these values ​​to determine the flicker. If desired, filtering and / or non-uniform sampling may be combined to avoid aliasing. Additionally or alternatively, Lomb-Scargle spectral analysis may be used to prevent attenuation of the measured flicker signal.

[0022] As an alternative to using a sigma-delta converter to determine ambient flicker, a folded capacitive transimpedance amplifier (C-TIA) circuit can be used to measure the ambient flicker. The folded capacitive transimpedance amplifier (C-TIA) circuit can measure flicker using the same steps as the sigma-delta converter, but can use a folding circuit triggered by timing and logic circuits to cause the voltage reduction to occur.

[0023] In other embodiments, a circuit combining a digital filter and a current source set by the digital filter can be used to measure ambient flicker. Specifically, the digital filter can set the current source to match the current generated by the photodiode, and the flicker portion can be determined. In this way, ambient flicker can be measured in the environment surrounding the electronic device.

[0024] An exemplary electronic device of the type in which one or more sensors may be provided is Figure 1 The electronic device 10 may be a computing device such as a laptop computer, a computer monitor including an embedded computer, a tablet computer, a cellular phone, a media player, or other handheld or portable electronic device, a smaller device (e.g., a wristwatch device or other device worn on a user's wrist), a hanging device, a headset or earpiece device, a device embedded in glasses or other equipment worn on a user's head, or other wearable or miniature device, a television, a computer display that does not include an embedded computer, a gaming device, a navigation device, an embedded system (e.g., a system in which electronic equipment with a display is installed in a kiosk or a car), equipment that implements the functionality of two or more of these devices, or other electronic equipment.

[0025] like Figure 1As shown, the electronic device 10 may have a control circuit 16. The control circuit 16 may include storage and processing circuits for supporting the operation of the device 10. The storage and processing circuits may include storage devices, such as hard disk drive storage devices, non-volatile memory (e.g., flash memory or other electrically programmable read-only memory configured to form a solid-state drive), volatile memory (e.g., static or dynamic random access memory), etc. The processing circuit in the control circuit 16 can be used to control the operation of the device 10. The processing circuit may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application-specific integrated circuits, etc. The control circuit 16 may include communication circuits for supporting wired and / or wireless communications between the device 10 and external equipment. For example, the control circuit 16 may include wireless communication circuits, such as cellular phone communication circuits and wireless local area network communication circuits. Some of the wireless communication circuits in the control circuit 16 may transmit radio frequency (RF) signals. For example, a transceiver in the wireless communication circuit may transmit an RF signal.

[0026] Input-output circuitry in device 10, such as input-output devices 12, may be used to allow data to be provided to device 10, and to allow data to be provided from device 10 to external devices. Input-output devices 12 may include buttons, joysticks, scroll wheels, trackpads, keypads, keyboards, microphones, speakers, audio generators, vibrators, cameras, light-emitting diodes and other status indicators, displays, data ports, etc. A user may control the operation of device 10 by supplying commands through input-output devices 12, and may receive status information and other output from device 10 using the output resources of input-output devices 12.

[0027] Input-output devices 12 may include one or more displays, such as display 14. Display 14 may be a touch screen display including a touch sensor for acquiring touch input from a user, or display 14 may be insensitive to touch. The touch sensor of display 14 may be based on an array of capacitive touch sensor electrodes, an acoustic touch sensor structure, a resistive touch component, a force-based touch sensor structure, a light-based touch sensor, or other suitable touch sensor arrangements. Display 14 may include any desired display technology and may be an organic light emitting diode (OLED) display, a liquid crystal display (LCD), a micro-LED display, or any other desired type of display.

[0028] Input-output device 12 may also include sensor 18. Sensor 18 may include capacitive sensors, light-based proximity sensors, magnetic sensors, accelerometers, force sensors, touch sensors, temperature sensors, pressure sensors, compasses, microphones, radio frequency sensors, three-dimensional image sensors, cameras, light-based position sensors (e.g., lidar sensors), and other sensors. Sensor 18 may also include one or more light detectors configured to detect ambient light. Sensor 18 may, for example, include one or more monochrome ambient light sensors and one or more color ambient light sensors that are configured to measure ambient light from the environment in which device 10 operates. A monochrome ambient light sensor may be used to measure ambient light intensity. A color ambient light sensor may be used to measure the color of ambient light (e.g., color spectrum, color temperature, color coordinates, etc.), and may be used to measure ambient light intensity.

[0029] In some exemplary embodiments, sensor 18 may include one or more sensors that measure ambient flicker. For example, sensor 18 may include a sigma-delta converter that measures ambient light and / or ambient flicker. Alternatively or in addition, sensor 18 may include a folded capacitive transimpedance amplifier (C-TIA) circuit that may be used to measure ambient flicker.

[0030] A perspective view of an illustrative electronic device of the type that may include one or more sensors for measuring ambient flicker is shown in FIG. Figure 2 In Figure 2 In the example of , device 10 includes a display, such as display 14 mounted in housing 22. Display 14 may be a liquid crystal display, an electrophoretic display, an organic light emitting diode display, or other display having an array of light emitting diodes (e.g., a display including pixels having diodes formed from a crystalline semiconductor wafer), may be a plasma display, may be an electrowetting display, may be a display based on microelectromechanical systems (MEMs) pixels, or may be any other suitable display. Display 14 may have an array of pixels 26 that extends across some or all of the front face F and / or other external device surfaces of device 10. The pixel array may be rectangular or may have other suitable shapes. Display 14 may be protected using a display cover layer (e.g., a transparent front housing layer) such as a layer of transparent glass or light transmissive plastic, sapphire, or other light transmissive layer. The display cover layer may overlap the array of pixels 26.

[0031] Housing 22, which may sometimes be referred to as an enclosure or housing, is formed of plastic, glass, ceramic, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or combinations of any two or more of these materials. Housing 22 and display 14 may separate an interior area of ​​device 10 from an exterior area surrounding device 10. Housing 22 may be formed using a unitary configuration in which a portion or all of housing 22 is machined or molded as a single structure, or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form an exterior housing surface, etc.). If desired, a wristband or other strap may be coupled to the main portion of housing 22 (e.g., in a configuration in which device 10 is a watch).

[0032] Pixels 26 may cover substantially the entire front face of device 10, or display 14 may have an inactive area (e.g., a notch, recessed area, rectangular area, or other area) that does not contain pixels 26. The inactive area may be used to accommodate openings for speakers and windows for optical components, such as one or more image sensors, analog sensors (such as ambient light sensors), optical proximity sensors, 3D image sensors (such as structured light 3D image sensors), and / or camera flashes. In an exemplary configuration, pixels 26 may extend across the entire front face F of device 10 and may overlap with sensors in area 30 (such as ambient light sensors or other sensors that measure ambient flicker). In this type of arrangement, ambient light may pass through the array of pixels 26 in display 14 to the ambient light sensors in area 30.

[0033] However, area 30 that may overlap with an ambient flicker sensor in device 10 may be formed anywhere on device 10. For example, the sensor may be on the rear surface (opposite to front surface F), on one of the side walls between the rear surface and front surface F, on front surface F but not overlapping display 14, or at any other location in device 10. Furthermore, area 30 may overlap with any desired type of sensor, such as an ambient light sensor, a pressure sensor, an accelerometer, or a sound sensor. In some embodiments, area 30 may be an opening in housing 22, or area 30 may be a portion of housing 22 that covers a sensor.

[0034] Exemplary sensors that may be incorporated into region 30 are Figure 3 As shown in Figure 3 As shown, the sigma-delta converter 32 may include a photodiode 34 , an integrating capacitor Cint 36 , an operational transconductance amplifier (OTA) 38 , a comparator 40 , and a reference capacitor Cref 42 .

[0035] Specifically, the photodiode 34 may be coupled to Cint 36 and coupled to the input of the OTA 38 together with Cref 42. Cref 42 may be coupled to a reference voltage Vref at a capacitive switch 41. An integrating capacitor Cint 36 may bridge the OTA 38. The output of Cint 36 may be coupled to the input of a comparator 40 having a threshold voltage Vth.

[0036] In operation, when light 35 falls on the photodiode 34, a photocurrent is generated. The generated photocurrent flows through the integrating capacitor Cint 36, because the input to the OTA 38 presents approximately infinite impedance. Because one end of Cint 36 is a virtual ground, the other end Vout ramps up linearly with time according to Equation 1,

[0037]

[0038] Where I_pd is the current of the photodiode 34 and t is time.

[0039] When Vout increases and exceeds the threshold Vth of comparator 40, comparator 40 is triggered, causing Vpulse to register one pulse (1 count). Therefore, the charge on Cref 42 is dumped on Cint 36 via capacitive switch 41, which causes Vout to drop by the voltage given by Equation 2,

[0040]

[0041] And the cycle repeats as the photodiode 34 generates more current in response to ambient light. An exemplary waveform of Vout generated by a sigma-delta converter such as sigma-delta converter 32 is shown in Figure 4 Shown in.

[0042] like Figure 4 As shown, the exemplary graph 44 may give Vout (eg, Figure 3 The relationship between the output voltage of Cint 36 in (a) and time. Figure 4 The illustrative example of shows Vout versus time when Cint=Cref and Vth=Vref=150 mV. However, in general, the threshold voltage Vth and the reference voltage Vref may have any suitable values.

[0043] As shown by curve 46, when the light intensity (e.g., Figure 3 As the intensity of ambient light on the photodiode 34 increases, the voltage Vout ramps over time. In other words, as the light intensity increases, Vout can ramp faster, thereby increasing counts at a higher rate ( Figure 3Because Vout decreases when the comparator 40 is triggered, the total count (Vpulse) generated by the comparator 40 during the integration period will give an indication of the light intensity.

[0044] In addition to or in lieu of measuring light intensity, a sigma-delta converter, such as sigma-delta converter 32, may be used to determine ambient light flicker. An exemplary method that may be used to detect flicker using a sigma-delta converter is described in Figure 5 Shown in.

[0045] like Figure 5 As shown, flowchart 31 may begin at step 33, where Vout is sampled. Specifically, an analog-to-digital converter (ADC) (such as one coupled to Figure 3 An ADC of a sigma-delta converter 32 may be used to sample Vout. The ADC may sample Vout at any suitable frequency, such as 8 kHz, 16 kHz, between 4 kHz and 16 kHz, or other suitable frequency. In an exemplary embodiment, the ADC may sample Vout at a frequency of 8 kHz to detect a maximum ambient light flicker frequency of 4 kHz.

[0046] ADCs can usually be used after charge removal (e.g. Figure 4 Vout is sampled before and after a drop in Vout). An exemplary graph showing samples generated by an ADC sampling Vout is shown in FIG. Fig. 6A Shown in.

[0047] like Fig. 6A As shown, curve 46 of graph 50 can be generated to give the relationship between Vout and time. For example, curve 46 of graph 50 can be compared with graph 44 ( Figure 4 ) corresponds to curve 46. ADC samples (e.g., at Figure 5 The sample of Vout taken at step 33 of FIG. 3 is shown as Fig. 6A s(1), s(2), s(3), ..., s(n). In general, the ADC may take any suitable number of samples. For example, the ADC may take at least 8 samples, at least 4 samples, at least 10 samples, or another suitable number (n) of samples during an integration period 47. In general, the number (n) of samples taken during an integration period 47 may vary based on the length of the integration period 47 and the frequency at which the samples are taken.

[0048] Back to Figure 5 After the ADC samples s(1), s(2), s(3), ..., s(n), the voltage change can be determined at step 37. Specifically, at step 37, the voltage change V Δ It can be determined by formula 3,

[0049] V Δ (n) = s(n+1) - s(n) + V ref *crossing_number∝slope(V out )-I pd (3) where crossing_number is a comparator (e.g., Figure 3 The number of times the comparator 40) is triggered during the time when s(n+1) and s(n) are sampled.

[0050] Shown V Δ An exemplary graph of Figure 6B As shown in Figure 6B As shown, curve 53 of graph 52 can give V Δ The relationship between and the number of samples (n). Curve 53 can give a sinusoidal relationship, such as Figure 6B However, this relationship is only illustrative.

[0051] Back to Figure 5 , the generated voltage changes V Δ Then, the transformation can be applied to V at step 39 Δ Specifically, a suitable transform such as a Fast Fourier Transform (FFT) may be applied to V Δ .

[0052] After FFT (or other suitable transformation), V Δ An exemplary graph of the spectrum of Figure 6C Specifically, the spectrum 55 of the curve 54 can give V Δ An exemplary frequency response of a signal. As shown in the figure, V Δ The FFT of gives the frequency response of the signal as spectrum 55, and the light source flicker frequency is shown as signal peaks 56A and 56B. Therefore, peaks 56A and 56B may also be referred to herein as ambient flicker signals. Figure 6C , peaks 56A and 56B may be at 120 Hz and 2 kHz, respectively, which may correspond to ambient light flicker. However, this is merely illustrative. Peaks such as peaks 56A and 56B will generally exist at frequencies corresponding to the frequency of ambient light flicker in a given environment. There may be a single peak 56, at least two peaks 56, at least three peaks 56, or any other number of peaks 56 corresponding to the frequency of ambient light flicker.

[0053] Compared to not using FIG. 6A to FIG. 6C ADC sampling and / or conversion of ambient flicker detection, using Figure 5 The method allows high gain to be obtained. Specifically, the equivalent transimpedance gain is given by Equation 4,

[0054]

[0055] Where Fs is the sampling rate / frequency of the ADC used to sample the output voltage Vout. For Fs=8kHz and Cint=87fF (as an illustrative example), the transimpedance gain is equivalent to 1.5GOhm. Because Cint is below the ambient flicker detection that does not reduce Cint when Cint exceeds the threshold voltage (e.g., Figure 4 and Fig. 6A As shown), the transimpedance gain can be Figure 5 Higher gain allows the use of an ADC with relatively low resolution, as well as allowing the ALS function (average intensity by statistical counting) and the scintillation function to operate concurrently.

[0056] However, in some cases, if the input signal (e.g., ambient light flicker) has interference at a frequency higher than half the sampling rate (Fs / 2) (e.g., 4kHz in the illustrative example of a sampling rate of 8kHz), aliased signals may appear in the signal band. Figure 7 Shown in.

[0057] like Figure 7 As shown, the graph 58 may have an exemplary spectrum 59. As described above in conjunction with Figure 7 As discussed, spectrum 59 may have peaks 56A and 56B (e.g., 120 Hz and 2 kHz) corresponding to ambient light flicker. However, spectrum 59 may also have an aliasing band 60. Aliasing band 60 may be, for example, at 1 kHz. Typically, aliasing band 60 may be avoided by performing a low pass filter on Vout prior to sampling, but this will cause a sawtooth waveform (e.g., Fig. 6A The curve 46) is distorted, so that the reconstructed V Δ Alternatively, a resistor-capacitor (RC) filter can be added to filter the photodiode current (e.g., from Figure 3 The current of the photodiode 34 can be filtered, but this would require very large R and C values ​​to obtain a 4kHz cutoff frequency.

[0058] Therefore, non-uniform sampling can be used for Vout (e.g., Figure 5 Vout is sampled in step 33 of ). For example, Vout may be sampled at a random frequency in the range between 7kHz-9kHz (e.g., instead of at 8kHz). This has the effect of converting the aliased signal into broadband noise. An illustrative example is shown in FIG. Fig. 8A and Figure 8B Shown in.

[0059] like Fig. 8AAs shown, in the graph 62, non-uniform sampling Fs 71 of Vout may be performed. Specifically, instead of sampling Vout at frequency 64 (e.g., 8kHz), it may be sampled at frequency 63A, frequency 63B, and / or one or more other frequencies between and including 63A and 63B. For example, Vout may be sampled at both frequencies 63A and 63B (and / or additional frequencies), at one of frequency 63A or frequency 63B, at one of frequency 63A or frequency 63B and at different phases between each sampling point in the sampling points, or at a random frequency between frequency 63A and frequency 63B. As an example, if frequency 64 is 8kHz, frequency 63A may be 9kHz, and frequency 63B may be 7kHz. However, these frequencies are merely illustrative. In general, one or more frequencies may be used to sample Vout non-uniformly.

[0060] By performing non-uniform sampling Fs 71, the aliased signal can be converted into broadband noise. Specifically, instead of having an aliased signal 67 (which can be equivalent to Figure 7 The non-uniform sampling Fs71 may result in a plurality of smaller signals 69A and 69B which may be equivalent to the noise in the Vout signal. Figure 8B Shown in.

[0061] like Figure 8B As shown, the exemplary spectrum 68 of the graph 66 may have peaks 56A and 56B without aliasing bands (e.g., aliasing band 60 of FIG. 6 ). In other words, the aliasing band 60 of FIG. 6 may be converted into noise (e.g., noise within the spectrum 68) by non-uniform sampling of Vout. In this way, by using non-uniform sampling, the aliasing bands may be reduced or eliminated, and ambient flicker may be determined.

[0062] although Figure 8B The aliasing band is eliminated, but the real ambient flicker signal 56B at 2kHz is also attenuated by 10dB. This is because (at Figure 5 The FFT applied at step 37 of assuming that the samples are uniformly sampled at 8kHz. Therefore, when non-uniform sampling is used, Lomb-Scargle spectral analysis can be used (e.g., instead of FFT). Lomb-Scargle spectral analysis can result in Figure 8B The same spectrum 68 of signal 56B is obtained without the attenuation of signal 56B.

[0063] (For example, if combined with Fig. 8A and Figure 8BAdditional hardware may be used to perform non-uniform FFT or Lomb-Scargle spectral analysis as described above. Thus, in some embodiments, it may be desirable to include a combination of hardware and software to perform non-uniform FFT or Lomb-Scargle spectral analysis. For example, instead of randomizing the sampling frequency of Vout, two (or more) different sampling frequencies (e.g., Fig. 8A The FFTs of the two different sampling rates can be compared to distinguish whether a given FFT signal is an in-band signal or an aliased signal. As an illustrative example, if there are two sampling frequencies 8 kHz and 9 kHz, all in-band signals below 4 kHz will appear at the same frequency in both FFTs (e.g., at Figure 8B In the spectrum of the 8kHz and 9kHz FFTs, the out-of-band aliased signals at >4.5kHz will be offset by 1kHz between the two FFTs. The out-of-band aliased signals can then be ignored as aliased signals. In this way, the ambient flicker signal can be distinguished from the aliased band by using two (or more) sampling frequencies. Doing so can reduce the need for additional hardware.

[0064] although Figure 3 8 describe the use of a sigma-delta converter for ambient flicker detection (and ambient light intensity detection, if desired), but a folded capacitive transimpedance amplifier (C-TIA) may alternatively or additionally be used to determine ambient flicker. Fig. 9 Shown in.

[0065] like Fig. 9 As shown, the folded C-TIA circuit 78 may include a photodiode 80, an integrating capacitor Cint 84, an amplifier 82 (which may be an operational transconductance amplifier (OTA) or other suitable amplifier), a comparator 86, a reference capacitor Cref 96, a low pass filter (LPF) 90, an analog-to-digital converter (ADC) 92, a timing and logic circuit 88, and a switch 98. Cref 96 and the switch 98 may form a folding circuit 94.

[0066] Photodiode 80 may be coupled to integrating capacitor Cint 84 and coupled to the input of amplifier 82 along with ground 83. The output of integrating capacitor Cint 84 may be coupled to LPF 90 and the input of comparator 86. Voltage Vth may also be coupled to the input of comparator 86. Cint 84 may bridge the input and output of amplifier 82.

[0067] The output of comparator 86 may be coupled to a timing and logic unit 88, which may have an output MSB (most significant bit) and an output BW_control to LPF 90 and a sample rate output to ADC 92. ADC 92 may receive Vout from LPF 90 and a sample rate from timing and logic unit 88, and may convert Vout to an output Dout. Dout may correspond to a Vout signal sampled by ADC 92 (e.g., sampled as Fig. 6A Vout values ​​of s(1), s(2), s(3), …, s(n)).

[0068] The output of the timing and logic unit 88 may also be coupled to a folding circuit 94. The folding circuit 94 may include switches 98A and 98B coupled in series on one side of a capacitor Cref 96 and switches 98C and 98D coupled in series on the opposite side of the capacitor Cref 96. The switch 98D may be coupled to a reference voltage Vref. A switch 99 may be coupled between the folding circuit 94 and the photodiode 80.

[0069] Switch 98C may be coupled to switch 98A and ground 97 , switch 99 may be coupled to ground 101 , and photodiode 80 may be coupled to ground 81 .

[0070] In operation, a charge dump (e.g., Figure 4 and Fig. 6A The charge dump shown in the decrease of Vout in ) is synchronized with the clock of ADC 92 to limit signal noise. Specifically, the front end of the folded C-TIA circuit 78 (e.g., photodiode 80, Cint 84, and amplifier 82) can integrate the current generated by the photodiode 80 (as described above in conjunction with Figure 3 The sigma-delta converter 32 of FIG. 8 is discussed above) and the comparator 86 monitors its output Vint. When Vint>Vth (the threshold voltage of the comparator 86), the comparator 86 trips and generates a pulse as an input signal to the timing control logic 88.

[0071] The timing and logic unit (TLU) 88 manages the clocks of the following circuit blocks: 1) folding circuit 94; 2) LPF 90; and 3) ADC 92. For the folding circuit 94, the TLU 88 runs the folding clock. When the TLU 88 detects a trigger from the comparator 86 (e.g., from the input signal), the TLU 88 may initiate the folding clock for the folding circuit 94. Specifically, at the rising edge of the folding clock, the non-overlapping clock required by the folding circuit 94 (e.g., for switches 98A-98D) will become available. Therefore, the folding circuit 94 can be enabled, and the integrator (Cint 84) is folded to reduce the output voltage Vout by a given voltage (Vref) while the integration process is still in progress without any interruption. In this way, the folding circuit 94 (with capacitor 96) of the folded C-TIA circuit 78 can be used to remove charge from the integration capacitor Cint 84, and the MSB generated by the TLU 88 can be used to determine the ambient light intensity and flicker (as described above). Figure 5 discussed in ).

[0072] An exemplary timing diagram that may be used with a folded C-TIA circuit, such as folded C-TIA circuit 78, is shown in FIG. Fig.10 As shown in Fig.10 As shown in timing diagram 100 of , folding clock 102 (eg, a clock for folding circuit 94) may have a frequency that is a multiple of ADC sampling clock 104. Fig.10 In the illustrative example of , a multiple of four is used. However, this is merely illustrative. In general, any suitable multiple may be used.

[0073] To allow the low pass filter 90 ( Fig. 9 ) has sufficient time to settle to the desired accuracy before the ADC (92) samples its output, folding is disabled when Folding_Enable 106 is low, regardless of the state of comparator 86. In other words, during the period of t_lpf, folding circuit 94 ( Fig. 9 ) will take no action. Therefore, depending on the input photodiode current (e.g., Fig. 9 The integrator output (Vint) will keep rising after exceeding the comparator threshold voltage Vth, based on the current generated by the photodiode 80. Therefore, the time t_lpf sets the dynamic range of the integration capacitor 84 and the integration capacitance. After the ADC samples (e.g., when the ADC sampling clock 104 goes low), if Vint>Vth as detected by the comparator 86, the circuit will complete the folding.

[0074] To help shorten t_lpf or allow the low pass filter 90 ( Fig. 9 ) is stabilized to a higher precision, and a dynamic bandwidth switching solution can be implemented. Fig.10 As shown, when BW_Control 108 is high, the low pass filter 90 is in a high bandwidth mode (e.g., in the MHz range) by using a switch to short the resistor in the low pass filter (90). During the BW_Control low period, the low pass filter (90) switches to a lower bandwidth mode (e.g., in the kHz range, such as 8kHz).

[0075] The folding clock 102 can be synchronized with light sources in other applications (e.g., proximity sensors). For example, the light source may follow an "on, off, on, off" pattern, and the folding clock 102 may follow the same pattern or the opposite pattern. Specifically, the TLU 88 ( Fig. 9 ) may generate a light source clock to pulse the light source and synchronize it with the folding clock 102. In this way, the integrator front end may not need to be reset.

[0076] The voltage Vout can be obtained by ADC 92 ( Fig. 9 ) for sampling. After sampling, post-processing may be performed to reconstruct the signal from ADC 92 in the digital domain. As an example, post-processing may be performed on the ADC (e.g., Fig. 9 ADC 92) samples Vout at 8kHz (assuming a maximum light flicker frequency of 4kHz) to give s(1), s(2), s(3), etc. (see, for example, Figure 5 ) is executed after that, and TLU 88( Fig. 9 ) outputs the folding number MSB(1), MSB(2), MSB(3), etc. for each sample. However, in general, the ADC may sample Vout at any suitable frequency. An illustrative example of steps for reconstructing the signal from the ADC in the digital domain is provided in Fig.11 Shown in.

[0077] like Fig.11 As shown in the flowchart 110, at step 112, the integrated signal (e.g., Fig. 9 The signal generated by the photodiode 80) can be reconstructed in the digital domain. The integrated signal in the digital domain (D_vout(n)) can be determined using Formula 5,

[0078] D_Vout(n)=s(n)+Vref*MSB(n) (5) where MSB(n) is the time before s(n) is sampled (e.g., Fig. 9 The number of folds determined by TLU 88.

[0079] At step 114, a DC value may be extracted from the integrated signal in the digital domain. Specifically, the DC value of light may be determined using Equation 6,

[0080] DC=D_Vout(N) / N (6)

[0081] Where N is the total number of samples in the integrated signal.

[0082] At step 116, the AC waveform may be determined using Equation 7,

[0083] AC(n)=D_Vout(n+1)-D_Vout(n)-DC (7)

[0084] Finally, at step 118, a transformation may be performed on the AC waveform. Specifically, FFT and / or Lomb-Scargle spectral analysis may be performed on AC(n) to obtain a frequency response of the signal, wherein the light source flicker frequency is shown as a peak (e.g., as Figure 8B shown).

[0085] In this way, the signal in the digital domain can be reconstructed. The signal can give a spectrum with peaks corresponding to the frequencies of ambient light flicker (e.g., as shown in Figures 6 to 8). In this way, the signal can be reconstructed in the digital domain. Fig. 9 The folded C-TIA circuit 78 is used to determine ambient light flicker.

[0086] In some embodiments, the Fig. 9 An alternative circuit to the folded C-TIA circuit 78 is used to detect ambient light flicker. Specifically, a circuit with a constant current source can be used to determine the amount of ambient flicker. Fig.12 Shown in.

[0087] like Fig.12 As shown, circuit 120 (also referred to herein as ambient flicker detection circuit and digital filter circuit) may include a photodiode 80 with an input coupled to ground and an output coupled to an amplifier 82. Capacitor Cpd 131 may bridge photodiode 80. Voltage source Vn 124 may have a grounded negative terminal and a positive terminal coupled to amplifier 82. Integrating capacitor 84 and switch 126 may bridge amplifier 82.

[0088] The output of integrating capacitor 84 may be coupled to filter resistor 128, which in turn may be coupled in series to switches 130 and 132. Switch 130 may be coupled to capacitor 134 and switch 142, and switch 132 may be coupled to capacitor 138 and switch 144. Switches 142 and 144 may be coupled to ADC 92, which has an output AC_OUT and an additional output coupled to digital filter 146. Digital filter 146 may have an output DC_OUT and an additional output coupled to a digital-to-analog converter (DAC 148). DAC 148 may be coupled to constant current source 150, which in turn may be coupled to the input of amplifier 82 along with the output of photodiode 80, thereby completing the loop.

[0089] In operation, the photodiode 80 may generate charge in response to incident light, and the charge may be stored at Cpd 131. The generated charge may be transferred to the filter resistor 128 through the integrating capacitor 84. If the generated charge is higher than the resistance of the filter resistor 128, the generated charge may be transferred to the capacitor 134 or the capacitor 136, depending on which of the switches 130 or 132 is open. For example, the switches 130 and 132 may be alternately opened and closed in a continuous integration of the generated charge.

[0090] Switch 140 or switch 144 may be closed, thereby passing the generated charge to ADC 92. ADC 92 may convert the charge into a digital signal AC_OUT. The digital signal may also be passed to digital filter 146, which may generate an output DC_OUT. The output may also be passed to DAC 148, which may drive current source 150.

[0091] Between integrations, amplifier 82 may be reset using switch 126 (eg, by closing switch 126 ).

[0092] AC_OUT may be a digital value representing ambient light flicker, while DC_OUT may be a digital value representing ambient light without flicker. Specifically, since the feedback loop with current source 150 is driven by the current from photodiode 80 (after passing through ADC 92 and digital filter 146) and the fixed nature of ambient light that is not affected by flicker (which will be reflected in DC_OUT), once current source 150 is set to the current generated by photodiode 80, ADC 92 will only receive ambient light flicker. In this way, ambient light flicker can be determined by a circuit using a digital filter and a constant current source.

[0093] Generally speaking, Figure 5 and / or Fig.11 The method of detecting environmental flicker can be used with Figure 4 ∑-Δ converter, Fig. 9The C-TIA circuit and / or Fig.12 In this way, a sigma-delta converter, a C-TIA circuit, or a digital filter circuit can be used to detect ambient flicker.

[0094] Regardless of the method and circuitry used to detect ambient flicker measurements, ambient flicker measurements may be used in any suitable manner. For example, a control circuit in a device (such as Figure 1 The control circuit 16 in the device 10 of the embodiment of the present invention can use the ambient flicker measurement to adjust one or more sensors in the device, such as a camera or other optical sensor. Alternatively or in addition, the ambient flicker measurement can be intermittently taken with the activation of the light source in the proximity sensor, and the ambient flicker measurement can be subtracted from the measurement from the proximity sensor. In this way, the ambient flicker measurement can be used to adjust one or more components in the electronic device and / or correct one or more optical measurements.

[0095] As described above, one aspect of the present technology is to collect and use information such as sensor information. The present disclosure contemplates that, in some cases, data including personal information data may be collected that uniquely identifies or can be used to contact or locate a specific person. Such personal information data may include demographic data, location-based data, phone numbers, email addresses, Twitter IDs, home addresses, data or records related to the user's health or fitness level (e.g., vital sign measurements, medication information, exercise information), date of birth, user name, password, biometric information, or any other identification or personal information.

[0096] The present disclosure recognizes that the use of such personal information in the present technology can be used to benefit the user. For example, the personal information data can be used to deliver targeted content that the user is more interested in. Therefore, the use of such personal information data enables the user to have control over the content delivered. In addition, the present disclosure also anticipates other uses of personal information data that benefit the user. For example, health and fitness data can be used to provide insights into the user's overall health status, or can be used as positive feedback to individuals who use technology to pursue health goals.

[0097] The disclosure anticipates that entities responsible for the collection, analysis, disclosure, transmission, storage or other purposes of such personal information data will comply with sound privacy policies and / or privacy measures. Specifically, such entities should implement and adhere to the use of privacy policies and practices that are recognized as meeting or exceeding industry or government requirements for maintaining the privacy and security of personal information data. Such policies should be easy for users to access and should be updated as changes in the collection and / or use of data occur. Personal information from users should be collected for legal and reasonable entity purposes and should not be shared or sold outside these legal purposes. In addition, such collection / sharing should be carried out after receiving the user's informed consent. In addition, such entities should consider taking any necessary steps to protect and safeguard access to such personal information data and ensure that other entities with access to personal information data comply with their privacy policies and procedures. In addition, such entities can subject themselves to third-party assessments to prove that they comply with widely accepted privacy policies and practices. In addition, policies and practices should be adapted to specific types of personal information data collected and / or accessed, and to applicable laws and standards including considerations of special jurisdictions. For example, in the United States, the collection or access of certain health data may be governed by federal and / or state laws such as the Insurance Portability and Accountability Act (HIPAA), while health data in other countries may be subject to other regulations and policies and should be handled accordingly. Therefore, different privacy measures should be advocated for different types of personal data in each country.

[0098] Regardless of the foregoing, the present disclosure also contemplates implementation schemes in which users selectively block the use or access of personal information data. That is, the present disclosure contemplates hardware elements and / or software elements to prevent or block access to such personal information data. For example, the technology of the present invention may be configured to allow users to choose to "opt in" or "opt out" to participate in the collection of personal information data at any time during or after registration for a service. For another example, a user may choose not to provide certain types of user data. For another example, a user may choose to limit the length of time that user-specific data is retained. In addition to providing "opt-in" and "opt-out" options, the present disclosure also contemplates providing notifications related to access or use of personal information. For example, a user may be notified that their personal information data will be accessed when downloading an application ("app"), and then the user may be reminded again before the personal information data is accessed by the app.

[0099] In addition, it is the intention of the present disclosure that personal information data should be managed and processed in a manner that minimizes the risk of unintentional or unauthorized access or use. Once the data is no longer needed, the risk can be minimized by limiting the collection of data and deleting the data. In addition and when applicable, including in certain health-related applications, data de-identification can be used to protect the privacy of users. When appropriate, de-identification can be facilitated by removing specific identifiers (e.g., date of birth, etc.), controlling the amount or characteristics of stored data (e.g., collecting location data at the city level rather than the address level), controlling the storage method of data (e.g., aggregating data between users), and / or other methods.

[0100] Thus, while the present disclosure broadly encompasses the use of information that may include personal information data to implement one or more of the various disclosed embodiments, the present disclosure also contemplates that various embodiments may be implemented without requiring access to personal information data. That is, various embodiments of the present technology will not fail to function properly due to the lack of all or a portion of such personal information data.

[0101] According to one embodiment, a folded capacitor transimpedance amplifier circuit is provided, comprising: a photodiode configured to generate charge in response to ambient light; an integrating capacitor receiving the generated charge; a low-pass filter configured to receive the generated charge and filter the generated charge; and a folding circuit coupled to the integrating capacitor, the folding circuit being configured to complete folding into the integrating capacitor to reduce the generated charge on the integrating capacitor when the generated charge exceeds a threshold voltage.

[0102] According to another embodiment, the folded capacitor transimpedance amplifier circuit includes: an analog-to-digital converter, which is configured to convert the filtered generated charge and produce an output voltage; and a timing and logic unit, which is coupled to the low-pass filter, the analog-to-digital converter and the folding circuit.

[0103] According to another embodiment, the folded capacitor transimpedance amplifier circuit includes: a comparator that receives the generated charge from the integrating capacitor and compares the generated charge with the threshold voltage, and the timing and logic unit is configured to receive a signal from the comparator.

[0104] According to another embodiment, the timing and logic unit is configured to clock the low-pass filter, the analog-to-digital converter and the folding circuit based on the signal from the comparator.

[0105] According to another embodiment, the folding circuit is configured to be enabled by the timing and logic unit when the signal from the comparator indicates that the generated charge exceeds the threshold voltage, and the folding circuit is configured to complete the folding into the integrating capacitor when the folding circuit is enabled.

[0106] According to another embodiment, the folding into the integrating capacitor is configured to reduce the generated charge on the integrating capacitor to reduce the output voltage by a given voltage.

[0107] According to another embodiment, the timing and logic unit is configured to clock the folding circuit with a first clock and to clock the analog-to-digital converter with a second clock that is a multiple of the first clock.

[0108] According to another embodiment, the folding circuit includes a plurality of switches and capacitors.

[0109] According to another embodiment, the capacitor of the folding circuit is configured to reduce the generated charge on the integrating capacitor to reduce the output voltage in response to a signal from the timing and logic unit.

[0110] According to one embodiment, a method for determining ambient flicker using a sigma-delta converter that generates an output voltage is provided, the method comprising: using an analog-to-digital converter to sample the output voltage at a given time; determining a voltage change between each sample of the output voltage sampled by the analog-to-digital converter; and transforming the voltage change to determine the ambient flicker.

[0111] According to another embodiment, using the analog-to-digital converter to sample the output voltage at a given time includes sampling the output voltage at a random frequency within a frequency range.

[0112] According to another embodiment, sampling the output voltage at the random frequency within the frequency range includes sampling the output voltage at the random frequency between 7 kHz and 9 kHz.

[0113] According to another embodiment, using the analog-to-digital converter to sample the output voltage at a given time includes sampling the output voltage at two or more frequencies.

[0114] According to another embodiment, using the analog-to-digital converter to sample the output voltage at a given time includes sampling the output voltage with different phases between samples.

[0115] According to another embodiment, transforming the voltage variation to determine the ambient flicker includes transforming the voltage variation using a Fast Fourier Transform.

[0116] According to another embodiment, transforming the voltage variation to determine the ambient flicker includes performing a Lomb-Scargle spectral analysis on the voltage variation.

[0117] According to one embodiment, an ambient flicker detection circuit is provided, comprising: a photodiode configured to generate an electric charge in response to ambient light; an integrating capacitor receiving the generated electric charge; an analog-to-digital converter coupled to the integrating capacitor and configured to output an ambient flicker signal; a digital filter coupled to the analog-to-digital converter and configured to receive the ambient flicker signal; and a current source coupled to the digital filter, wherein the current source is configured to output a current equivalent to the generated electric charge to the integrating capacitor.

[0118] According to another embodiment, the digital filter is further configured to output a flicker-free ambient light measurement.

[0119] According to another embodiment, the ambient flicker detection circuit includes: a digital-to-analog converter interposed between the digital filter and the current source.

[0120] According to another embodiment, the ambient flicker detection circuit includes: a resistive filter, which is coupled to the output end of the integrating capacitor; a first switch and a second switch, which are coupled in parallel to the resistive filter and the analog-to-digital converter; and a first capacitor and a second capacitor, which are coupled to the first switch and the second switch, respectively.

[0121] According to another embodiment, the ambient flicker detection circuit includes an amplifier and a reset switch coupled to the integrating capacitor.

[0122] The foregoing is merely illustrative and various modifications may be made to the embodiments described. The foregoing embodiments may be implemented independently or in any combination.

Claims

1. A folded capacitor transimpedance amplifier circuit, the folded capacitor transimpedance amplifier circuit comprising: a photodiode configured to generate charge in response to ambient light; an integrating capacitor receiving the generated charge; a low pass filter configured to receive the generated charges and filter the generated charges; and A folding circuit is coupled to the integrating capacitor, wherein the folding circuit is configured to complete folding into the integrating capacitor to reduce the generated charge on the integrating capacitor when the generated charge exceeds a threshold voltage.

2. The folded capacitor transimpedance amplifier circuit of claim 1 , further comprising: an analog-to-digital converter configured to convert the filtered generated charge and produce an output voltage; and A timing and logic unit is coupled to the low pass filter, the analog to digital converter and the folding circuit.

3. The folded capacitor transimpedance amplifier circuit of claim 2 , further comprising: A comparator receives the generated charge from the integrating capacitor and compares the generated charge to the threshold voltage, wherein the timing and logic unit is configured to receive a signal from the comparator.

4. The folded capacitor transimpedance amplifier circuit of claim 3, wherein the timing and logic unit is configured to clock the low pass filter, the analog to digital converter, and the folding circuit based on the signal from the comparator.

5. The folded capacitor transimpedance amplifier circuit of claim 4 , wherein the folding circuit is configured to be enabled by the timing and logic unit when the signal from the comparator indicates that the generated charge exceeds the threshold voltage, and the folding circuit is configured to complete the folding into the integrating capacitor when the folding circuit is enabled. 6 . The folded capacitor transimpedance amplifier circuit of claim 5 , wherein the folding into the integrating capacitor is configured to reduce the generated charge on the integrating capacitor to reduce the output voltage by a given voltage.

7. The folded capacitor transimpedance amplifier circuit of claim 4, wherein the timing and logic unit is configured to clock the folding circuit with a first clock and to clock the analog-to-digital converter with a second clock that is a multiple of the first clock.

8. The folded capacitor transimpedance amplifier circuit of claim 2, wherein the folding circuit comprises a plurality of switches and capacitors.

9. The folded capacitor transimpedance amplifier circuit of claim 8, wherein the capacitor of the folding circuit is configured to reduce the generated charge on the integrating capacitor to reduce the output voltage in response to a signal from the timing and logic unit.

10. A method of determining ambient flicker using a sigma-delta converter that generates an output voltage, the method comprising: using an analog-to-digital converter to sample the output voltage at a given time; determining a voltage change between each sample of the output voltage sampled by the analog-to-digital converter; as well as The voltage variation is transformed to determine the ambient flicker.

11. The method of claim 10, wherein using the analog-to-digital converter to sample the output voltage at a given time comprises: The output voltage is sampled at a random frequency within a frequency range.

12. The method of claim 11 , wherein sampling the output voltage at the random frequency within the frequency range comprises: The output voltage is sampled at the random frequency between 7 kHz and 9 kHz.

13. The method of claim 10, wherein using the analog-to-digital converter to sample the output voltage at a given time comprises: The output voltage is sampled at two or more frequencies.

14. The method of claim 10, wherein using the analog-to-digital converter to sample the output voltage at a given time comprises: The output voltage is sampled with different phases between samples.

15. The method of claim 10, wherein transforming the voltage variation to determine the ambient flicker comprises: The voltage variation is transformed using a Fast Fourier Transform.

16. The method of claim 10, wherein transforming the voltage variation to determine the ambient flicker comprises: Lomb-Scargle spectroscopy analysis was performed on the voltage changes.

17. An environmental flicker detection circuit, the environmental flicker detection circuit comprising: a photodiode configured to generate charge in response to ambient light; an integrating capacitor receiving the generated charge; an analog-to-digital converter coupled to the integrating capacitor and configured to output an ambient flicker signal; a digital filter coupled to the analog-to-digital converter and configured to receive the ambient flicker signal; and A current source is coupled to the digital filter, wherein the current source is configured to output a current equivalent to the generated charge to the integrating capacitor.

18. The ambient flicker detection circuit of claim 17, wherein the digital filter is further configured to output a flicker-free ambient light measurement.

19. The ambient flicker detection circuit according to claim 18, further comprising: A digital-to-analog converter is interposed between the digital filter and the current source.

20. The ambient flicker detection circuit of claim 19, further comprising: a resistive filter coupled to an output terminal of the integrating capacitor; a first switch and a second switch, the first switch and the second switch being coupled in parallel to the resistive filter and the analog-to-digital converter; a first capacitor and a second capacitor, the first capacitor and the second capacitor being coupled to the first switch and the second switch, respectively; and An amplifier and a reset switch are coupled to the integrating capacitor.

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