TWI448871B - Direct current (dc) correction circuit for a time of flight (tof) photodiode front end - Google Patents

Description

DC correction circuit for flight time photodiode front stage

The present invention relates to a time-of-flight photodiode preamplifier, and more particularly to a DC correction circuit for use in a flight time photodiode preamplifier.

Cross-reference to related applications

The present application claims priority to U.S. Provisional Patent Application Serial No. 61/298,895, filed on Jan. 27, 2010, which is entitled ARCHITECTURE FOR A REFLECTION BASED LONG RANGE PROXIMITY AND MOTION DETECTOR HAVING AN INTEGRATED AMBIENT LIGHT SENSOR), which is incorporated herein by reference in its entirety. Further, the present application is also related to the following U.S. Patent Application: copending U.S. Patent Application Serial No. 12/979,726, filed on Dec. 28, 2010. ), the case titled "DISTANCE SENSING BY IQ DOMAIN DIFFERENTIATION OF TIME OF FLIGHT (TOF) MEASUREMENTS"; the co-pending of the application on January 25, 2011 U.S. Patent Application Serial No. 13/013,199 (legal file number SE-2785-AN/INTEP105USC), entitled "PHOTODIODE FRONT END WITH IMPROVED with Improved Power Supply Rejection Ratio" POWER SUPPLY REJECTION RATIO (PSRR)); the copending United States that was submitted on January 25, 2011 Patent Application No. 13/013,173 (legal file number SE-2876-AN/INTEP105USD), titled "AUTOMATIC ZERO CALIBRATION TECHNIQUE FOR TIME OF FLIGHT (TOF) (TRANSCEIVERS)); copending U.S. Patent Application Serial No. 13/013,640 (legal file number SE-2877-AN/INTEP105USE), filed on January 25, 2011, entitled "Used for Gestures SERIAL-CHAINING PROXIMITY SENSORS FOR GESTURE RECOGNITION; and copending U.S. Patent Application Serial No. 13/013,676, filed on Jan. 25, 2011. -2878-AN/INTEP105USF), the case titled "GESTURE RECOGNITION WITH PRINCIPAL COMPONENT ANALYSIS". Each of the prior applications is hereby incorporated by reference in its entirety.

Prior art includes "Distance Sensors with PIN Light Diodes and Bridge Circuits" by Nemeecek et al., IEEE Sensors Journal, Vol. 6, No. 2, April 2006. The prior art does not disclose a sensor and a direct current (DC) correction circuit coupled to the sensor; wherein the DC correction circuit reduces a portion of the DC generated by an environmental signal incident on the sensor. Error; and the DC correction loop produces a small amount of noise relative to the noise spectrum generated by one or more of the signal processing components included in the previous stage Spectrum density.

There is an emerging integrated device that allows electronics to sense their environment. These devices include a wide variety of devices, such as accelerometers, monolithic gyroscopes, light sensors, and imagers. In particular, light sensors are the simplest and cheapest ones, which allows them to be incorporated into many consumer products, for example, nightlights, cameras, cellular phones, laptops. ,...Wait. In general, light sensors can be used in a wide variety of applications related to proximity sensing, for example, but not limited to: detecting the presence of a user and/or detecting the user to The distance of the product for the purpose of controlling power, display, or other interface options.

Infrared (IR) proximity detectors use IR light to detect objects in the sensing area of the IR sensor. Furthermore, the IR light is emitted by an IR Light Emitting Diode (LED) emitter that deflects off at objects in the surrounding area and is reflected by a detector. Furthermore, the detector may also be a diode (for example, a PIN diode), and/or any other type of device that converts IR light into an electrical signal. The sensed signal is analyzed to determine if an object is present in the sensing area. Some conventional systems emit an IR light pulse and detect if the pulse returns to the PIN diode. However, these conventional systems are easily confused by the existing IR light in the real world, for example, ambient light, sunlight, ... and the like. Moreover, such conventional systems are also incapable of distinguishing between non-stimulated reflections from static objects (for example, chairs, tables, soda cans, etc.) and from objects (for example, humans, animals, etc.). .. etc.) reflection. Thus, to compensate for the existing IR light, the prior art system measures the data twice: once when the IR emitter is on and emits an IR pulse; and once when the IR emitter is off. Furthermore, the IR responses in both cases are measured and subtracted. However, implementing such calculations is a cumbersome and time consuming process. In addition, these conventional detectors range from only about 10 to 30 centimeters (cm). Further, to overcome the effects of ambient light over a wide range (for example, in the range of 20 to 30 cm), the IR LED must also emit a significant amount of power.

The systems and methods disclosed herein provide a novel signal processing technique for active long range distance sensors that prevents direct current (DC) saturation of the front stage without causing significant noise (for example Said, noise spectrum density). For example, the distance sensor disclosed herein may range from 1 to 2 meters. In one of the views, light emitted by an IR LED is modulated at high frequencies, for example, 1 MHz to 50 MHz. Then, the received IR response, for example, is demodulated by using a quadrature amplitude demodulation transformer (I/Q demodulation) and processed to confirm an object and the sensor. The distance between them. It will be understood that although the specification of the present invention is described herein with reference to IR light; however, the systems and methods disclosed herein are capable of utilizing most of any wavelength. For example, the system and/or method steps of the present invention can be used in sonic proximity detection applications and/or ultrasonic range finding applications. Further, although the present specification explains and describes a light/optical sensor (for example, a photodiode); however, it can be understood that it also covers most of the conversion of a physical input into a signal. Any circuit requirements.

The main content of the present invention will be described with reference to the drawings, in which the same element symbols are used to denote the same elements. For the purposes of explanation, many specific details are set forth in the following description in order to provide a thorough understanding of the invention. However, it will be understood that the main aspects of the invention may be practiced without these specific details. The structures and devices well known will be shown in block diagram form in other examples to assist in illustrating the invention. Of course, those skilled in the art will appreciate that many modifications can be made to this configuration without departing from the scope or spirit of the subject matter of the invention as claimed herein.

Furthermore, the term "exemplary" as used herein is intended to serve as an example, instance, or example. Any ideas or designs described herein as "exemplary" are not necessarily to be considered as a preferred point of view or design or preferred. Rather, the use of the term “exemplary” is intended to present concepts in a concrete form. The word "or" as used in this application is intended to mean an inclusive "or" rather than an exclusive "or". That is, unless explicitly mentioned, or the meaning of the text is very clear; otherwise, "X uses A or B" hopes to mean any essential inclusive arrangement. That is, if X uses A; X uses B; or X uses A and B; then, in any of the foregoing cases, it conforms to "X uses A or B." In addition, the articles "a", as used in this application and the scope of the appended claims, are to be construed as meaning "." Furthermore, the term "coupled" as used herein means either direct or indirect electrical or mechanical coupling. Further, unless there is a special distinction between the terms "sense area", "vision field", "optical field" and the similar terms in the text; otherwise, These terms and similar terms can be used interchangeably in this application. Further, the term "environment" as used herein may refer to light having most of any reasonable spectrum, for example, but not limited to: white hot light, fluorescent light, sunlight, any black body temperature, and / Or a combination of them. Furthermore, the term "ambient light" as used herein may encompass most of any light from a constant source.

Referring to Figure 1, there is shown an aspect of the present disclosure for an exemplary system 100 for reducing DC saturation in a front stage of a long range proximity detector. In general, system 100 can be utilized in most of any light sensing application and/or optical proximity application. For example, a laptop or personal computer may be powered on by detecting the user entering the room by using the system 100 (for example, booting from a state of hibernation, standby, etc.); or When the operator is too close to a machine, the machine will use the system 100 to alert the operator to the danger. In another example, a cellular phone or a Personal Digital Assistant (PDA) may turn off the display by using the system 100 when detecting that the phone/PDA is being held at the user's ear. (to save battery life).

In general, system 100 utilizes TIME OF FLIGHT (TOF) measurements, which rely on the limited speed of light. This finite velocity causes a delay between the emission of an electromagnetic wave and its reflection from an object that is proportional to the distance of the object. In system 100, the distance may be measured with a phase delay of a modulated (for example, at 5 MHz) IR LED signal. Furthermore, for proximity sensing based on IR signal detection, system 100 utilizes an IR LED 102 and an IR sensor 104. For example, the system 100 may utilize a high frequency (eg, 5 MHz) modulated LED 102 and a tuned PIN detector 104 to optimize the detection range. In general, an LED driver 106 may be used to provide an input signal (for example, a frequency modulated signal) to the LED 102. In general, a local oscillator (not shown) synchronized to the LED driver may be utilized in synchronous detection (e.g., by the sensor pre-stage circuitry 118). For example, the IR LED 102 will have a typical spike wavelength that matches the proximity sensor spectrum; a narrow viewing angle with higher radiation intensity that can help gather energy that is well suited for proximity sensing. It can be understood that most of the IR LEDs (or arrays) can be applied based on the following coefficients, for example, but not limited to: viewing angle, mechanical height, coverage, radiation intensity, current consumption. Quantity, ..., etc. Further, the IR LED 102 can transmit the modulated IR signal 108 to the sensing object 110; and the IR sensor 104 can receive a portion 112 of the transmitted signal from the surface of the sensing object 110. Reflected back. The object 110 may be the majority of any of the entities of interest, such as, but not limited to, human bodies, automation components, devices, articles, animals, ... and the like.

In general, the size of the reflection 112 will depend on the size of the object 110, the color of the object 110, and the distance separating the object 110 from the IR sensor 104. For example, a white shirt may produce a higher reflection than a black shirt. In addition to the reflections 112 from the object 110, the sensor 104 may also receive various other signals 114, such as, but not limited to, electrical crosstalk, optical crosstalk, and/or environmental backscattering (environmental). Backscatter). Each of these signals represents interference caused by the detection of the object of interest. Electrical crosstalk and optical crosstalk among the interferences may be approximately constant during the life of the device and can be corrected at the manufacturing or development stage of the application. Environmental backscatter 114 may then be received from various sources in the range of light of the sensor 104 and may include most of any signals that the object 110 is not interested in detecting. For example, objects such as table surfaces, couches, television displays, soda cans, etc. are not practical targets, but are detected as signals received at the sensor 104. Important composition. In one embodiment, the constant light sources (eg, fluorescent, electric light, sunlight, etc.) will collectively become ambient light incident on the sensor 104.

If a large amount of ambient light is received, the DC value of the current generated by the sensor 104 will increase and may cause the front stage circuitry 118 to saturate. In one example, the "pre-stage" disclosed herein may include (multiple) amplifiers, filter(s), demodulators, most of any analog and/or digital signal processing circuits, and/or Or any circuit that meets the specifications of the sensor that can be used by the sensor for the latter stage. For example, the pre-stage may include one or more amplifiers, one or more Analog-to-Digital Converters (ADCs), and/or a signal processor. In one aspect, the system 100 utilizes a DC correction loop 116 that adaptively adjusts the thermal noise of different ambient light conditions and eliminates the DC saturation current introduced by the ambient light, which is not in the system 100. Provide obvious noise (for example, hot noise, ). In one example, the DC correction loop 116 may mimic an inductor that corrects the error signal produced by ambient light, as explained in more detail below with reference to Figures 2, 3, and 4.

It will be appreciated that the mechanical design of system 100 may include different component selections, different component placement methods, different dimensions, different glass cover features, different LED options, and between sensor 104 and LED 102. Different isolation technologies, ..., etc., to achieve the best proximity sensing effect. Furthermore, LED 102 may be the majority of any light source, for example, but not limited to: LED, organic LED (OLED), bulk emitting LED, surface emitting LED, vertical cavity surface emitting laser (Vertical Cavity Surface Emitting Laser (VCSEL), Super luminescent Light Emitting Diode (SLED), laser diode, pixel diode, or the like. It will be appreciated that the source can produce IR light or light having most of any other wavelength. In addition, it will be appreciated that the sensor may also include a majority of any light detecting requirements that can be used to generate a current or voltage indicative of the magnitude of the detected light, for example, but It is not limited to: a photoresistor, a photovoltaic cell, a photodiode, a photoelectric crystal, a Charge-Coupled Device (CCD), or the like.

Further, it will also be appreciated that the LED driver 106 and the pre-stage circuitry 118 may contain most of any of the electrical circuit(s), which may include components and circuitry requirements having any convenient values for implementation. Embodiments of the invention. Moreover, LED driver 106, DC correction loop 116, and pre-stage circuitry 118 may also be implemented on one or more integrated circuit (IC) wafers and may be incorporated in the same or different (multiple) inside the package. In general, various IR bands (for example, a near-IR band, a medium-wave IR band, and a long-wave IR band) can be utilized in an imaging system. There may be unique LEDs and sensors in each band. Typically, some visible light detector systems will operate in the near IR band and may include detectors integrated into the system IC. In addition, it is also understood that the system 100 is not limited to the use of IR light, and the LED/sensor/detector can also utilize signals having most of any wavelength.

Referring now to Figure 2, there is shown an exemplary system in accordance with one aspect of the present specification including an IC 202 that corrects an error signal generated by a sensor due to ambient light during distance sensing. Furthermore, the IC 202 can also be used as a primary distance monitoring system and/or as a component for correcting legacy systems. In particular, IC 202 includes a DC correction loop 116, an amplifier 204, and a distance decision circuit 206 that confirms the separation of an object from the PIN diode. As can be appreciated, the DC correction loop 116 may include, for example, functionality that has been fully described herein for the system 100. Further, although a single IC (202) is illustrated in FIG. 2; however, it will be appreciated that a plurality of ICs or devices may be utilized to implement the system.

The active IR proximity detector disclosed herein uses an IR LED emitter to emit IR light that is reflected away from objects in the sensing region, and reflections from such objects are detected by a detector ( For example, a PIN diode) is sensed. Generally, ambient light is also incident on the detector along with the reflected light. In particular, the ambient light and/or other error signals (for example, leakage current from the photodiode) provide a DC value in the current generated by the detector. For example, ambient light may contain most of any low frequency light, including: sunlight, artificial light (for example, intended to illuminate a room or an area), and/or from a movement that may not be of interest. The shadow/light of the object. In another example, ambient light may also include higher frequency light from an artificial light source, such as 100 Hz or 120 Hz light with various higher resonances emitted by light directly driven by the power line. Ambient light may also include higher frequency light emitted by fluorescent illumination driven by a small transformer circuit in the 100 KHz frequency range and resonant frequency. Traditionally, a gain switching system (where the system gain can be adaptively changed to respond to ambient light) may be used to correct for DC errors caused by ambient light. Alternatively, a DC correction may be performed using a switched capacitor cancellation technique or a TransImpedance Amplifier (TIA) with a DC feedback loop. However, such complex systems may introduce significant noise (for example, noise spectral density) at the front stage of the detector. Conversely, the DC correction loop 116 utilizes a simple, rugged, and low-noise circuit that maintains a constant gain in the front of the detector, thus simplifying the design.

In one of the views, the DC correction loop 116 can be adapted to the full range of DC currents at the modulation frequency (for example, 5 MHz) (for example, due to ambient light and/or most of any error signals) The result of the unfavorable result is only a small amount of noise. Furthermore, the DC correction circuit 116 also provides a circuit for transmitting high frequency optical signals (for example, reflected from an object) to an amplifier 204 or a filter (not shown), while eliminating/decreasing the incidence by The lower frequency signal generated by the ambient light on the detector. In one example, the DC correction loop 116 mimics an inductor that removes the DC component of the diode current and prevents saturation of the front stage of the proximity detection circuit. In particular, the DC correction loop 116 utilizes a architecture that achieves DC correction but does not add thermal noise at the modulation frequency (for example, low noise spectral density). An example circuit for the DC correction loop will be described in detail in Figures 3 and 4. The DC correction loop 116 may typically include two amplifiers, for example, transconductance amplifiers (gm ₁ and gm ₂ ). In addition, a resistor to a capacitor (C _F, R _F) may be used to attenuate the first transconductance amplifier (gm ₁₎ of the noise transfer function, and the second bias voltage across the amplifier (gm ₂₎ is It is automatically and dynamically adjusted to reduce noise.

The high frequency signal from the DC correction loop is then transmitted to one or more preamplifiers 204. The amplified signal is provided to a distance decision circuit 206 for proximity/motion detection. In one example, the distance decision circuit 206 may include: a demodulation transformer, for example, a demodulation circuit for demodulating the amplified signal; and a method for confirming the demodulation The phase of the signal phase is the circuit for the purpose of TOF measurement.

Figure 3 is a perspective view of the present invention for compensating by an optical An example circuit diagram 300 of the DC current generated by the sensor. In one example, circuit 300 allows a TOF pre-stage to operate in the presence of ambient light (e.g., up to 100 klux) without saturation. In addition, the circuit 300 does not add significant noise (for example, noise power spectral density) to the previous stage at the modulation frequency. Furthermore, the value of the spectral power density of the noise signal referred to in the "Significant Noise" and/or "Substantial Noise" used herein is above a predefined threshold at which it will be in close proximity / Errors are introduced in motion detection.

The photodiode 302 generates a current I _{ambient+signal} in response to light incident thereon and provides it to the capacitor C _D 310. Light incident on the photodiode 302 includes light that reflects from an object (which causes I _signal ) and _{undesired ambient} light (which causes I _ambient ). A portion of the current generated by the photodiode 302 due to ambient light introduces a DC component in the diode current. In general, the DC composition may cause an error that would put the detector's front stage at risk. In one of the views, a DC correction loop 308 (which will be provided parallel to the photodiode 302) mimics an inductor and thus suppresses the DC composition of the diode current due to ambient light. Furthermore, the DC correction loop 308 also corrects the DC composition without adding significant noise at the modulation frequency (for example, 5 MHz).

The DC correction loop 308 includes amplifiers gm1 (304) and gm2 (306) and a pair of capacitor resistors (C _F , R _F ) connected at the opposite terminals of gm1 (304). Specifically, C _F R _F attenuates the noise transfer function of gm1 (304). The reference voltage V _REF (for example, ground) connected across the resistor R _F establishes a bias point of the photodiode 302, which is an important factor in the operation of a PIN photodiode. In addition, gm2 is adaptively changed by adjusting its bias voltage to adjust/control/reduce the spectral density of the noise. Furthermore, gm2 (306) is adapted to the change in ambient current so that the noise contribution of the DC correction circuit 308 is properly maintained below the noise contribution of the ambient light itself. Specifically, when the value of the ambient current changes, the value of gm2 is changed based on the bias applied by the output of gm1 to ensure that the noise level of circuit 300 is not too noticeable.

In one aspect, the DC correction loop 308 would ideally turn the DC transfer function to zero at the photodiode node (N), and no DC component would pass through the remaining circuitry, for example, Voltage amplifier, filter(s), etc. Moreover, because the DC correction loop 308 mimics/behaves as an inductor, a short circuit to ground is provided for the DC component. Accordingly, the DC correction loop 308 generates a zero at the DC and inhibits the DC constituent signal from entering the front stage of the sensor (eg, the voltage amplifier(s)). Signals output from the circuit 300 are provided to the (equal) voltage amplifier and further analog and/or digital signal processing to aid proximity/motion detection. Furthermore, the output signal does not contain a DC component caused by ambient light and therefore protects the front stage from saturation.

Additionally, the loop gain of the DC correction loop 308 can be calculated as follows:

Wherein, C _F based capacitor C _F 314 is; R _F. Department of the resistor R _F 312 of the resistor; gm2 of amplifier gain based gm2; C _D 310 302-based photo-capacitance diode; and a constant S series.

According to one embodiment, R _F 312 can be implemented as a Metal-Oxide Semiconductor (MOS) transistor capable of tracking gm2 (306) with temperature. The MOS transistor will achieve more accurate frequency response control in the loop near the LED modulation frequency. The R _F tracking technique is described in detail in the U.S. Patent Application Serial No. 4,458,212, to Brehmer et al., entitled "COMPENSATED AMPLIFIER HAVING POLE ZERO TRACKING", for the amplifier compensation. This is incorporated herein by reference. Further, gm2 (302) of the R _F may also track with temperature and process the loop frequency response for better control.

Referring to Figure 4, there is shown another example circuit 400 of a low noise DC correction circuit for use in TOF measurement, in accordance with one aspect of the specification disclosed herein. Moreover, for example, the DC correction loop 402 can control the Signal-to-Noise Ratio (SNR) at a particular frequency (for example, the modulation frequency (5 MHz)) and is responsive to ambient light. The DC composition in the diode current generated by the photodiode 302 is reduced/removed.

Similar to the DC correction circuit 308, the DC correction circuit 402 is provided in parallel with the photodiode 302 to compensate for the diode current generated by ambient light incident on the photodiode 302. Moreover, the DC correction loop 402 also mimics/behaves as an inductor and thus provides a path to ground for the DC component. In particular, the DC correction loop 402 generates a zero at the DC and inhibits the DC constituent signal from entering the front of the sensor (for example, a voltage amplifier(s)). For example, a non-inverting input of a first amplifier gm1 (304) may be connected to a reference voltage (V _ref ), for example, grounded; and an inverted input may be passed through the resistor R _F 312 Connect to node N. Furthermore, V _ref connected above the non-inverting input of amplifier gm1 (304) establishes the bias point of photodiode 302. Further, a capacitor C _F 314 is incorporated into a feedback loop of gm1 (304) such that C _F R _F attenuates the noise transfer function of gm1 (304). In addition to this, the output of gm1 (304) is also provided to the non-inverting input of gm2 (306) and used to control the bias of gm2 (306). Accordingly, when the value of the ambient current changes, the value of gm2 (306) changes, so that the noise introduced by the DC correction circuit 402 is less than the noise introduced by the ambient current.

In one aspect, R _F 312 can be implemented as a MOS transistor that provides better control of the loop frequency response with temperature and process. In particular, the MOS transistor is capable of tracking gm2 (306) with temperature and achieving more accurate frequency response control in the loop near the LED modulation frequency. The _FR tracking technique is described in detail in the U.S. Patent Application Serial No. 4,458,212, to Brehmer et al., which is incorporated herein by reference.

Figure 5 shows an exemplary frequency domain plot 500 of effective photodiode impedance in accordance with an aspect of the present invention. In circuit 300 and/or 400, photodiode 302 is capable of converting incident light into a current. The effective impedance of the photodiode, |Z _diode |, is plotted in Figure 5 with respect to frequency. Furthermore, the effective impedance, |Z _diode |, can also be calculated as follows:

Where, Vin-based input voltage; Iin system of the input current; C _F. Department capacitor C _F 314 a; R _F. Department of the resistor R the resistance _F 312 is; gm2 based amplifier gm2 gain; Department C _D 310 photo-capacitor 302 diode ; and S is a constant.

As seen in diagram 500, at ultra low frequencies, the effective impedance of the photodiode, |Z _diode |, is zero. In other words, at low frequencies, no voltage is generated at node N. Further, the effect of ambient light can be seen from the characteristic curve of the frequency response of the DC correction loop (308 and/or 402). Again, the impedance represents the gain, which is considered to be zero in DC processing (this means that the DC will be completely removed by the DC correction loop 308 and/or 402). Initially, the gain increases with increasing frequency, and at the desired frequency, the gain is significantly higher than DC. Further, at a particular frequency (f ₁ to f ₂ ), the frequency response will first stagnate and then decay again (at f ₂ ). In general, if the necessary signal is provided within the stagnation frequency range (for example, in response to a signal generated by light reflected from the object), it will pass normally. In other words, the attenuation coefficient between the necessary signal and DC is very significant between f ₁ and f ₂ .

Referring now to Figure 6, there is shown an exemplary circuit 600 for a PMOS (p-channel metal oxide semiconductor) device implemented in a DC correction loop for DC attenuation in accordance with one aspect of the present invention. According to an embodiment, gm2 (306) can be implemented as most of any PMOS device, for example, but not limited to PMOS transistor 306. The bias voltage of PMOS transistor 306 is controlled by the output of gm1, as shown in Figures 3 and 4. The noise caused by the DC correction loop is dominated by the value of gm2 (the gain of PMOS transistor 306). Accordingly, if the value of gm2 is increased, the power spectral density noise generated by the DC correction loop will increase. By adapting the system to change the value of gm2, the DC correction circuit will ensure that the noise caused by the relationship of the PMOS transistor 306 is substantially less than the noise caused by the ambient current.

Moreover, the bias voltage of the PMOS transistor 306 is also adaptively changed based on the ambient light signal to adaptively change the value of gm2 so that the noise caused by the PMOS transistor 306 is substantially It will be less than the noise caused by the environmental signal. Further, when the current source I _bleed 602 drops, low noise is introduced at the low ambient signal; conversely, when the ambient signal increases, the shot noise is dominant. However, the noise caused by the DC correction loop is always less than the noise caused by the ambient current. In one aspect, the PMOS transistor 306 may include a more complex circuit component (for example, a complex amplifier) than a single Field Effect Transistor (FET), which causes conduction of the complex element. Sex can be controlled and able to change size.

The output current is controlled by the PMOS transistor 306, which is then controlled by the amplifier gm1. Furthermore, amplifier gm1 will first compare the reference voltage (for example, ground) with the feedback voltage from the output and then amplify the difference. If the feedback voltage is lower than the reference voltage, the gate of the PMOS device is pulled low, allowing more current to pass and increasing the output voltage. If the feedback voltage is higher than the reference voltage, the gate of the PMOS device is pulled high, allowing less current to pass and lowering the output voltage.

7 is a method step and/or flow diagram in accordance with the main aspects disclosed herein. To simplify the explanation, the method steps are described and illustrated in a series of actions. It should be understood and appreciated that the invention is not limited to the order of the acts and/or actions shown in the figures. For example, a plurality of acts can be performed in various sequences and/or simultaneously, and possibly also Other actions not described and illustrated herein are presented. Also, it is not necessary to use all of the illustrated acts to implement the method steps in accordance with the subject matter disclosed herein. Moreover, those skilled in the art will understand and appreciate that the method steps can also be represented by a series of interrelated states or by a plurality of events. In addition, it should be further understood that the method steps disclosed below and throughout the specification can be stored in a manufactured article to facilitate the transport and transfer of such method steps to a computer. The term "manufactured goods" as used herein is intended to encompass computer programs that are available from any computer readable device or computer readable storage/communication media.

Figure 7 shows an exemplary method step 700 of being able to resolve the distance of an object or the distance at which the motion occurs while ignoring the effects of ambient light incident on a sensor. In general, method step 700 can be utilized in a variety of applications, such as, but not limited to, consumer electronic devices (eg, cellular phones, laptops, media players, gaming systems, nights) Depending on the system, etc.), mechanical systems (for example, door/window mechanisms), industrial automation systems, robots, etc.

At 702, for example, a signal input to a transmitter (for example, an IR LED) may be modulated at a high frequency in the range of millions of Hertz (for example, 1 MHz to 50 MHz). For example, most of any modulation technique can be used for modulation. At 704, the frequency modulated signal may be used by the IR LED to illuminate. In general, the range of the IR LEDs can be selected depending on the application (for example, 1 to 2 meters). The emitted IR signal is reflected back from the object(s) (moving and/or stationary) in the light range, and the reflected signals are combined with ambient light (for example, sunlight, Fluorescent, electric light, light bulbs, etc.) are received at an optical sensor (for example, an IR sensor). At 706, the signal is received from the sensor; and at 708, the DC component of the received signal (eg, due to ambient light incident on the sensor) is Attenuation while controlling the noise caused by the attenuation circuit. Further, at 710, the signal is processed, for example, amplified, filtered, demodulated, etc., to confirm the position of the object and/or motion. position. Typically, the signal is amplified by the use of one or more amplifiers and demodulated by the use of a quadrature amplitude demodulator. Furthermore, the phase data is also found based on the demodulation, and then the phase data can be used to confirm the proximity or motion of an object.

To provide additional background information for the various aspects of the specification, FIG. 8 shows an exemplary functional block diagram of an architecture 800 of the present invention. In one of these aspects, the systems disclosed herein (for example, as shown in Figures 1 through 4 and 6) can be used with or without integrated ambient light sensors (Ambient Light Sensor, ALS). Among the reflection-based proximity and motion detectors. The architecture 800 includes an LED and associated driver circuitry (not shown, not shown), a photodiode sensor 302, an analog preamplifier and signal processing 802, and a data conversion circuitry (example) For example, analog to digital converter 804), digital control and signal processing 806 (for example, complex Computer Programmable Logic Device (CPLD)), interface circuit system (not simplified, in the figure Not shown), and/or result display (not shown, not shown). The architecture 800 adaptively optimizes sensitivity and power for a given environment. Furthermore, the architecture 800 will also yield significant performance improvements and reduce the risk of pre-saturation.

According to one aspect of the invention, the architecture 800 includes a front end (FE) including a Trans-Inductance Amplifier (TIA). For example, the DC correction circuits 300, 400, and 600 disclosed above can all be implemented within the DC correction loop 116 of section 808. Moreover, the DC correction circuit 116 attenuates the DC component (for example, an error signal) of the electrical signal generated by the detector. Further, the DC correction loop 116 may cause less noise than one or more of the signal processing components in the front stage of the reflection-based proximity detector (for example, the amplifier 810, the analog FE 802, The noise caused by the ADC 804, ..., etc.).

In general, the output of the front stage 808 may be subject to multiple levels of voltage gain to maximize the SNR of the output signal. For example, the voltage gain is adaptively set based on the magnitude of the signal received from the previous stage 808, which includes the desired signal to be measured. These disturbances are dynamically corrected in the measurement to improve sensitivity (for example, by the DC correction loop 116). The architecture 800 may also include: a demodulator with a low pass filter (LPF) (not shown, not shown) for performing frequency demodulation; a converter (ADC) 804; a Universal Serial Bus (USB) processor for controlling the interface; and a Computer Programmable Logic Device (CPLD) comprising a plurality of modules. Furthermore, a digital signal processor (DSP) 806 also processes the digital signal to confirm the proximity of an object, the motion of an object, and/or the sensing of an object present in the sensor 302. Inside the range.

The architecture 800 of the present invention can be used in a variety of applications including: computers, automated vehicles, industrial, television displays, and other applications. For example, the architecture 800 can be used to detect that a user has entered the room and automatically wakes up the laptop in sleep mode and enters the active mode, enabling the user to use it. According to one aspect of the invention, the architecture 800 is capable of performing motion sensing and proximity sensing at a range of up to 1 to 2 meters. In accordance with another aspect of the present invention, the architecture 800 of the present invention is capable of performing its operation using less than twenty milliwatts (mW) of power.

In one embodiment of the invention, the entire architecture 800, along with the LED driver circuitry, is implemented in a single integrated circuit chip (IC) along with the LEDs. In another embodiment of the invention, all components of the architecture 800 can be implemented in the IC in addition to the LED driver circuitry and the LEDs (which may be implemented outside of the IC). In yet another embodiment of the invention, various components of the architecture 800 can be disposed inside or outside of the IC.

The various examples of the invention have been described above. Of course, it is not possible to clarify various combinations of elements or method steps that can be considered for the purpose of illustrating the main content claimed herein; however, those skilled in the art will appreciate that the present invention may have many further The combination and arrangement. Accordingly, the subject matter of the present disclosure is intended to cover all such changes, modifications, and variations in the spirit and scope of the appended claims.

In particular, and in connection with the functions of the elements, devices, circuits, systems, and the like described above, unless specifically stated otherwise, the structural aspects are not equivalent to the embodiments disclosed herein. The structure of the exemplary aspects of the main content claimed herein, however, the various terms used to describe such elements (including references to "components") are intended to correspond to the specified functions of the elements described. Any component (for example, functionally equivalent). In this regard, it is to be understood that the present invention includes a system and a computer readable medium having actions and/or events for implementing various methods of the subject matter claimed herein. Computer executable instructions.

The previously mentioned systems/circuits/modules have been described herein for the interaction between several components. It will be understood that such systems/circuits/modules and elements may include such elements or specified sub-elements, a part of such specified or sub-components, and/or additional elements, and Arrange and combine. Sub-elements may also be implemented as components that are communicatively coupled to other components, rather than being incorporated into the parent component (hierarchical). In addition, it should also be noted that one or more elements can be combined into a single element to provide a collective function; or can be divided into several separate sub-components, and any one or more intermediate layers (eg, A management layer may be provided for communicatively coupling to such sub-elements to provide integration functionality. Any of the elements described herein may also interact with one or more other elements that are not commonly described herein but are generally known to those of ordinary skill in the art. Furthermore, the components and circuitry described above have any suitable values for implementing embodiments of the present invention. For example, the resistor may have any suitable resistance, the capacitor may have any suitable capacitance, the amplifier may provide any suitable gain, etc.

Moreover, although only one of several embodiments may be disclosed herein to disclose a particular feature of the invention; however, if desired, in any given or particular application, this feature may be combined with other embodiments. One or more other features, and are quite advantageous. In addition, to a certain extent, the words "including", "having", "containing", their variations, and other similar terms, and open transitions are used in the detailed description or patent application scope of this article. The words "including" are similar, and the words are intended to be inclusive, and do not exclude any additional or other elements.

100. . . Sample system

102. . . IR LED

104. . . IR sensor or PIN detector

106. . . LED driver

108. . . Modulated IR signal

110. . . Sensing object

112. . . reflection

114. . . Other signal or environmental backscatter

116. . . DC correction loop

118. . . Pre-stage circuit system

202. . . IC

204. . . Amplifier

206. . . Distance decision circuit

300. . . Example circuit

302. . . Light diode/sensor

304. . . Amplifier

306. . . Amplifier

308. . . DC correction loop

310. . . capacitance

312. . . Resistor

314. . . Capacitor

400. . . Example circuit

402. . . DC correction loop

500. . . Example frequency domain graph

600. . . Example circuit

602. . . Battery

700. . . Sample method

702-710. . . step

800. . . Architecture

802. . . Analog preamp

804. . . Analog to digital converter

806. . . Digital signal processing

808. . . Pre-stage

810. . . Amplifier

Figure 1 shows an exemplary system for reducing direct current (DC) saturation in the front stage of a long range proximity detector that does not introduce significant noise.

2 is an exemplary system including an integrated circuit (IC) wafer that corrects an error signal generated by an optical sensor due to ambient light during distance sensing.

Figure 3 is an exemplary circuit diagram for compensating for direct current (DC) current generated by an optical sensor.

4 is an exemplary circuit of a low noise DC correction circuit that is utilized in time-of-flight (TOF) measurements, in accordance with one aspect of the specification disclosed herein.

Figure 5 is an exemplary frequency domain plot of effective photodiode impedance in accordance with an aspect of the present invention.

Figure 6 shows an exemplary circuit for implementing a P-channel Metal-Oxide-Semiconductor (PMOS) device in a DC correction loop for DC attenuation.

Figure 7 is an exemplary method step of being able to resolve the distance of an object or the distance at which the motion occurs while ignoring the effects of ambient light incident on a sensor.

An exemplary functional block diagram of the architecture of the present invention is shown in FIG.

116‧‧‧DC correction circuit

202‧‧‧IC

204‧‧‧Amplifier

206‧‧‧Distance decision circuit

Claims (23)

A system for reducing DC saturation in a prior circuit of a proximity detector includes: a driver configured to generate a high frequency (HF) drive signal, the HF drive signal being usable to drive a light emitting component, Therefore, an HF optical signal is emitted, and a photo sensor is configured to generate a sensor signal, the sensor signal indicating light incident on the photo sensor, wherein the sensor signal includes a low frequency (LF) component and an HF component, wherein the LF component including a direct current (DC) component indicates ambient light that is not of interest, and wherein the HF component indicates reflected light of interest; a front stage circuitry, Including one or more amplifiers and/or one or more filters; and a DC correction loop circuitry configured to remove the LF component from the sensor signal while passing the HF component of the sensor signal Up to the pre-stage circuitry to thereby prevent DC saturation of the pre-stage circuitry; wherein the DC correction loop circuitry includes a first transconductance amplifier (gm1) and a second transconductance amplifier (gm2), the first One of the transconductance amplifiers (gm1) And into the second (GM2) one of the outputs of the transconductance amplifier system with a coupled to the same node, the system node at one terminal coupled to the photo sensor circuit of the front stage system. Such as the system of claim 1 of the patent scope, wherein the DC correction circuit The circuit system includes: the first transconductance amplifier (gm1) including a non-inverting (+) input, a reverse (-) input, and an output; the second transconductance amplifier (gm2) including an input An output coupled to one of the first transconductance amplifiers (gm1), and an output coupled to one of the non-inverting (+) inputs of the first transconductance amplifier (gm1); a capacitor coupled to the The output of the first transconductance amplifier (gm1) and the reverse (-) input of the first transconductance amplifier (gm1); and a resistor coupled to the first transconductance amplifier (gm1) Between the reverse (-) input and a reference voltage (Vref); wherein the non-inverting (+) input of the first transconductance amplifier (gm1) and the output of the second transconductance amplifier (gm2) The node is coupled to the node, and the node is coupled to the terminal of the photo sensor to the front stage circuit system. The system of claim 2, wherein: the second transconductance amplifier (gm2) comprises a PMOS transistor comprising a gate, a source and a drain; the second transconductance amplifier (gm2) The input includes the gate of the PMOS transistor; and the output of the second transconductance amplifier (gm2) includes the drain of the PMOS transistor. The system of claim 1, wherein the DC correction loop circuit system comprises: the first transconductance amplifier (gm1) comprising a non-inverting (+) input, a a reverse (-) input and an output; the second transconductance amplifier (gm2) includes an input coupled to one of the first transconductance amplifier (gm1) outputs, and an output; a resistor, Coupling the output of the second transconductance amplifier (gm2) to the reverse (-) input of the first transconductance amplifier (gm1); wherein the non-inverting (+) of the first transconductance amplifier (gm1) The input system is coupled to a reference voltage (Vref); wherein the reverse (-) input of the first transconductance amplifier (gm1) is coupled to the node by the resistor, the node is coupled to the light The terminal of the sensor is connected to the front-end circuit system; wherein the output of the second transconductance amplifier (gm2) is coupled to the node, the node is coupled to the terminal of the photo sensor to the Pre-stage circuitry. The system of claim 4, wherein: the second transconductance amplifier (gm2) comprises a PMOS transistor comprising a gate, a source and a drain; the second transconductance amplifier (gm2) The input includes the gate of the PMOS transistor; and the output of the second transconductance amplifier (gm2) includes the drain of the PMOS transistor. The system of claim 1, wherein one of the frequency of the transmitted HF optical signal and the frequency of the HF component of the sensor signal is in a range from 1 MHz to 50 MHz. Such as the system of claim 1 of the patent scope, wherein the DC correction circuit The circuitry is in parallel with the photosensor. A system as claimed in claim 1, wherein the DC correction loop circuitry is configured to mimic an inductor without the use of an inductor. The system of claim 1, wherein the DC correction loop circuitry does not include a switched capacitor circuit. The system of claim 1, wherein the DC correction loop circuit system introduces less thermal noise in the frequency component of the HF component of the sensor signal than the introduction of the preamp circuit system . The system of claim 1, further comprising: a detection circuitry configured to detect a distance, occurrence, and/or motion of an object relative to the optical sensor based on an output of the one of the pre-stage circuitry . A DC correction loop circuit comprising: a first transconductance amplifier (gm1) comprising a non-inverting (+) input, a reverse (-) input and an output; and a second transconductance amplifier (gm2) Included, an input coupled to one of the first transconductance amplifiers (gm1), and an output coupled to the non-inverting (+) input of the first transconductance amplifier (gm1); a capacitor Is coupled between the output of the first transconductance amplifier (gm1) and the reverse (-) input of the first transconductance amplifier (gm1); and a resistor coupled to the first Between the reverse (-) input of the transconductance amplifier (gm1) and a reference voltage (Vref). For example, the DC correction loop circuit of claim 12, wherein The non-inverting (+) input of the first transconductance amplifier (gm1) and the output of the second transconductance amplifier (gm2) are coupled to a node coupled to a terminal of a photosensor To the front stage circuit system. The DC correction loop circuit of claim 12, wherein the non-inverting (+) input of the first transconductance amplifier (gm1) and the output of the second transconductance amplifier (gm2) are coupled to one The node is coupled to a terminal of one of the photosensors to the front stage circuitry, and the DC correction circuit prevents DC saturation of the pre-stage circuitry. The DC correction loop circuit of claim 12, wherein the non-inverting (+) input of the first transconductance amplifier (gm1) and the output of the second transconductance amplifier (gm2) are coupled to one a node coupled to a terminal of a photo sensor to a front stage circuit system, the DC correction circuit removing an LF component by using one of the sensor signals generated by the photo sensor, and passing the One of the PON components of the sensor signal is applied to the pre-stage circuitry to thereby prevent DC saturation of the pre-stage circuitry. The DC correction loop circuit of claim 12, wherein the DC correction loop circuit mimics an inductor without including an inductor. The DC correction loop circuit of claim 12, wherein the second transconductance amplifier (gm2) comprises a PMOS transistor comprising a gate, a source and a drain; the second transconductance amplifier The input of (gm2) includes the gate of the PMOS transistor; and the output of the second transconductance amplifier (gm2) includes the drain of the PMOS transistor. A DC correction loop circuit comprising: a first transconductance amplifier (gm1) comprising a non-inverting (+) input, a reverse (-) input and an output; and a second transconductance amplifier (gm2) An input coupled to one of the output of the first transconductance amplifier (gm1) and an output; a resistor coupled to the output of the second transconductance amplifier (gm2) to the first cross The reverse (-) input of the amplifier (gm1); and wherein the non-inverting (+) input of the first transconductance amplifier (gm1) is coupled to a reference voltage (Vref). The DC correction loop circuit of claim 18, wherein: the reverse (-) input of the first transconductance amplifier (gm1) is coupled to a node by the resistor, the node is coupled One end of a photo sensor is connected to the front stage circuit system; and the output of the second transconductance amplifier (gm2) is coupled to the node, the node is coupled to the terminal of the photo sensor to The pre-stage circuit system. The DC correction loop circuit of claim 18, wherein the reverse (-) input of the first transconductance amplifier (gm1) is coupled to a node by the resistor and the node is coupled to the node One end of the photo sensor is connected to the front stage circuit system, and when the output of the second transconductance amplifier (gm2) is coupled to the node, the node is coupled to the terminal of the photo sensor to the The DC correction circuit prevents DC saturation of the pre-stage circuitry during the pre-stage circuitry. The DC correction loop circuit of claim 18, wherein the reverse (-) input of the first transconductance amplifier (gm1) is by the resistor The node is coupled to a node coupled to a terminal of the optical sensor to the front stage circuit system, and when the output of the second transconductance amplifier (gm2) is coupled to the node, the node is coupled When the terminal of the photo sensor is connected to the pre-stage circuit system, the DC correction circuit removes an LF component from one of the sensor signals generated by the photo sensor, and passes through the sensor. One of the signals HF components to the pre-stage circuitry to thereby prevent DC saturation of the pre-stage circuitry. A DC correction loop circuit as claimed in claim 18, wherein the DC correction loop circuit mimics an inductor without including an inductor. The DC correction loop circuit of claim 18, wherein the second transconductance amplifier (gm2) comprises a PMOS transistor comprising a gate, a source and a drain; the second transconductance amplifier The input of (gm2) includes the gate of the PMOS transistor; and the output of the second transconductance amplifier (gm2) includes the drain of the PMOS transistor.