DAC generated driven shield and voltage reference

Abstract

The capacitive sensor system includes a capacitive sensor including a sense electrode and a shield electrode; a regulator circuit configured to adjust a voltage of the capacitive sensor and generate an output signal based on an output of the capacitive sensor; a reference signal generator configured to generate a reference signal, supply the reference signal to the capacitive sensor via the regulator circuit, and supply the reference signal to the shield electrode as a drive shield signal; and an offset control module configured to generate an offset signal to modify an output current of the output signal.

Description

[Technical Field]

[0001] The present disclosure relates to capacitive sensors, and more particularly to reference signal generators for capacitive sensors. [Background technology]

[0002] The background discussion provided herein is intended to generally present the context for the present disclosure. The inventors' work, to the extent described in this background section, and aspects of the description that may not be prior art at the time of filing, are not admitted, explicitly or implicitly, as prior art to the present disclosure.

[0003] An electronic device may implement a capacitive sensor configured to sense contact between an object (e.g., a finger) and a surface, such as the surface of the electronic device, and generate a sense signal indicative of the sensed contact. For example, a reference signal generator (e.g., a waveform generator) is configured to generate and output a reference or control signal to the capacitive sensor. The sense signal corresponds to a change in amplitude and / or phase of the reference signal based on whether an object is touching the sensor. Thus, the presence or absence of an object touching the sensor can be determined based on the amplitude or phase of the sense signal.

[0004] The electronic device may include a drive shield circuit that receives a sense signal and outputs a drive shield signal based on the sense signal. The drive shield signal is provided to a drive shield of the capacitive sensor to prevent capacitive coupling between an external object and the capacitive sensor. In some examples, the drive shield signal is coupled to the drive shield to match the voltage of the drive shield to the voltage of the capacitive sensor. Patent Document 1 describes an example implementation of a drive shield circuit. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 5,166,679 Summary of the Invention [Problem to be solved by the invention]

[0006] Technical problems associated with conventional driven shield circuits include long settling times of the voltage of the capacitive sensor and clipping of the sense signal. The capacitive sensor system according to the present disclosure provides a solution to these technical problems by using the same reference signal supplied to the capacitive sensor as the driven shield signal and generating an offset signal according to the rising timing of the reference signal to reduce clipping of the sense signal. [Means for solving the problem]

[0007] For example, a capacitive sensor system according to the present disclosure includes a capacitive sensor including a sense electrode and a shield electrode; a regulator circuit configured to adjust a voltage of the capacitive sensor and generate an output signal based on an output of the capacitive sensor; a reference signal generator configured to generate a reference signal, provide the reference signal to the capacitive sensor via the regulator circuit, and provide the reference signal to the shield electrode as a drive shield signal; and an offset control module configured to generate an offset signal to modify an output current of the output signal.

[0008] In other features, the regulator circuit includes a current conveyor coupled to the capacitance sensor. The current conveyor is configured to adjust a voltage of the capacitance sensor based on a reference signal provided by a reference signal generator. The reference signal generator includes a digital-to-analog converter. The reference signal generator generates the reference signal as a periodic signal. The capacitance sensor generates an output as a sense signal corresponding to the reference signal, the sense signal being altered according to at least one of contact with an object and proximity of an object.

[0009] In other features, an offset control module is coupled to the output of the regulator circuit to modify an output current of the output signal. The offset control module generates the offset signal as an offset current, and the offset control module adds the offset current to the output current to reduce the magnitude of the output current. The offset control module adds the offset current to the output current to reduce the magnitude of the output current below a clipping region. The offset control module is configured to add the offset current to the output current while the output current increases from an initial value to a sensed input value.

[0010] In other features, the offset control module generates the offset signal such that a rising timing of the offset signal aligns with a rising timing of the output signal. To generate the offset signal such that a rising timing of the offset signal aligns with a rising timing of the output signal, the offset control module generates an offset current at a rising timing of the reference signal. The regulator circuit generates the output signal as one of a step input signal and a ramp input signal. The reference signal generator is configured to generate the reference signal having a predetermined slope. The regulator circuit generates the output signal having a slope corresponding to the predetermined slope of the reference signal. The regulator circuit generates the output signal having a positive slope, and the offset control module generates the offset signal having a negative slope complementary to the positive slope of the output signal.

[0011] Further areas of applicability of the present disclosure will become apparent from the detailed description, claims, and drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. [Effects of the Invention]

[0012] According to embodiments of the present disclosure, long settling times of voltages in capacitive sensors and clipping of sense signals can be reduced. [Brief explanation of the drawings]

[0013] The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: [Figure 1] 1 is an example of a capacitive sensor system including a driven shield circuit. [Figure 2A] 1 is an example of an electronic device that includes a capacitive sensor. [Figure 2B] 1 is an example of a reference signal generator for a capacitive sensor. [Figure 2C] 1 is an example of a reference signal generator for a capacitive sensor. [Figure 3] 1 is an example of a capacitive sensor system implementing a switched-capacitor circuit for a capacitive sensor according to the present disclosure. [Figure 4A] 1 illustrates a step input signal, a ramp signal, and corresponding output signals of a capacitive sensor according to the present disclosure. [Figure 4B] 1 illustrates a ramp input signal, a ramp offset signal, and corresponding output signals of a capacitive sensor according to the present disclosure.In the drawings, reference numbers may be reused to identify similar and / or identical elements. DETAILED DESCRIPTION OF THE INVENTION

[0014] Changes in the signal (corresponding to the sensed signal) supplied to the capacitive sensor in response to contact with an object are typically small relative to the supplied signal (i.e., drive signal, control signal, or reference signal), and can be difficult to detect. Therefore, different methods may be implemented to improve detection of the changes. For example, the reference signal generator that provides the reference signal to the sensor may supply a replica of the reference signal, or a second reference signal generator may be provided to supply a replica of the reference signal. The replica signal is subtracted from the supplied signal, and the result can be amplified to improve detection, corresponding to the sensed signal.

[0015] In some examples, the reference signal generator is a sine wave generator, such as a Wien bridge oscillator. In other examples, the reference signal generator may be configured to provide a digital sine wave to a digital-to-analog converter (DAC), the output of which is filtered and / or amplified. In some examples, the offset control module is configured to generate an offset signal that is a replica of the sensed signal when there is no contact between the object and the capacitive sensor.

[0016] In some examples, an electronic device including a capacitive sensor may include a regulator circuit (e.g., a voltage-controlled current-mode regulator) coupled to an output of the capacitive sensor, the regulator circuit configured to regulate an output voltage corresponding to a reference signal and supplied to the capacitive sensor to generate an output current indicative of the sensed signal.

[0017] 1 , an example capacitive sensor system 100 includes a detection circuit 104 and a drive shield circuit 108. The detection circuit 104 is configured to generate an output signal based on a sense signal received from a capacitive sensor 110. For example, the detection circuit 104 may include a timing circuit and / or other components configured to generate the output signal. The drive shield circuit 108 is configured to receive the sense signal and output a drive shield signal based on the sense signal. For example, the drive shield circuit 108 may include an operational amplifier 112 and one or more resistors R, as shown, where the drive shield signal is a buffered copy of the sense signal.

[0018] The drive shield signal is provided to the drive shield 116 of the capacitive sensor system. For example, the drive shield 116 may be a conductive plate, sheet, etc. (i.e., a shield electrode) positioned to prevent capacitive coupling between an external object and the capacitive sensor 110. In some examples, the drive shield signal is coupled to the drive shield 116 to match the voltage of the drive shield 116 to the voltage of the capacitive sensor 110. Capacitance associated with parasitic capacitance between the capacitive sensor 110 and the drive shield 116 can be significant with respect to the sense signal. Therefore, any difference between the respective voltages on the capacitive sensor 110 and the drive shield 116 results in signal buildup on the input signal path (i.e., the path of the sense signal between the capacitive sensor 110 and the detection circuit 104). The difference between these voltages can cause clipping of the sense signal (e.g., an output signal generated based on the sense signal).

[0019] Additionally, because the voltage of the capacitive sensor 110 may fluctuate and have an associated settling time, there is an associated delay for the voltage of the drive shield 116 to match the voltage of the capacitive sensor 110 (i.e., the voltage of the drive shield 116 "follows" the voltage of the capacitive sensor 110 with an associated delay). In other words, once the voltage of the capacitive sensor 110 has stabilized, the drive shield 116 reacts to each change in the voltage of the capacitive sensor 110. Each time the voltage of the drive shield 116 changes in response to a change in the voltage of the capacitive sensor 110, a sense signal may be capacitively coupled to the drive shield 116, which triggers further settling of both the capacitive sensor 110 and the drive shield 116.

[0020] A capacitive sensor system according to the principles of the present disclosure generates the driven shield signal using a reference signal generator. For example, the driven shield signal corresponds to the same reference signal provided to the regulator circuit and the capacitive sensor, as described in more detail below. In some examples, the reference signal generator is a DAC configured to generate a periodic reference signal and output the reference signal to the regulator circuit, the capacitive sensor, and the driven shield (e.g., via the regulator circuit).

[0021] 2A , an example electronic device 200 is shown that includes a sensor module 204 that corresponds to a capacitive sensor. A reference signal generator (e.g., a waveform generator) 208 provides a reference or control signal (e.g., a square wave, a sine wave, etc.) 210 to the sensor module 204. The reference signal generator 208 further provides the reference signal 210 to a driven shield of the sensor module 204 in accordance with the principles of the present disclosure. The reference signal generator 208 may provide the reference signal 210 to an offset control module 212, or an optional second reference signal generator 216 may provide a replica of the reference signal 210 to the offset control module 212.

[0022] The sensor module 204 modifies the reference signal 210 and generates a sensed signal 218 based on the reference signal 210 and the proximity or contact of the sensed object. In other words, the sensed signal 218 corresponds to the reference signal 210 modified according to the detection of the object (e.g., contact with and / or proximity of the object). The sensed signal 218 indicates whether an object (e.g., a finger) is in contact with the sensor module 204. In some examples, the sensed signal 218 indicates the proximity of the object to the sensor module 204. The sensed signal 218 may differ (e.g., in amplitude and / or phase) from the reference signal 210 regardless of whether an object is in contact with the sensor module 204.

[0023] In one example, the offset control module 212 is configured to generate an offset signal 220 that is a replica of the sense signal 218 without contact between an object and the sensor module 204. In other words, the offset control module 212 is configured to modify the reference signal 210 in the same manner as the sensor module 204 when there is no contact between the object and the sensor module 204 (and / or, in some examples, when the object is not close enough to the sensor module 204 to affect the sense signal 218). Thus, when there is no contact with an object, the sense signal 218 and the offset signal 220 are essentially the same (e.g., in magnitude, phase, and / or both magnitude and phase), and the difference between the sense signal 218 and the offset signal 220 approaches zero. In other examples, the offset signal 220 may be configured to have an opposite polarity relative to the reference signal 210 and may simply be summed with the sense signal 218.

[0024] Conversely, when there is contact between the object and the sensor module 204, the offset signal 220 and the sense signal 218 differ. The regulator circuit 224 outputs and amplifies the difference between the offset signal 220 and the sense signal 218. The regulator circuit 224 is further configured to adjust the voltage provided to the sensor module 204 (e.g., the voltage of the reference signal 210). In some examples, the regulator circuit 224 may be a voltage-controlled current-mode regulator implemented as a current conveyor. For example, the current conveyor is configured to receive an input voltage (e.g., the reference signal 210), adjust the output voltage (e.g., the voltage provided to the sensor module 204) based on the input voltage, and generate an output current (e.g., the output signal 228) indicative of the sense signal 218.

[0025] An output signal 228 (e.g., an output current) of the regulator circuit 224 indicative of the sense signal 218 may then be processed to detect contact between the sensor module 204 and an object. For example, contact may be determined based on whether the amplitude and / or phase of the output signal 228 exceed respective thresholds. In some examples, the sense signal 218 may indicate the proximity of an object to the sensor module 204, regardless of whether the object is in direct contact with the sensor module 204. In these examples, the sense signal 218 may further indicate the distance between the object and the sensor module 204. The output signal 228 is provided to an output signal path (e.g., an output signal path of a capacitive sensor system of the electronic device 200). For example, the output signal 228 is provided to an ADC via a sample and hold circuit.

[0026] The reference signal generator 208 is configured to generate a periodic signal such as a square wave, a sine wave, etc. For example, the reference signal generator 208 may include a DAC. In some examples, the reference signal generator 208 implements a Wien-bridge oscillator. In other examples, the reference signal generator 208 may generate a digital sine wave, which is then converted to an analog sine wave. For example, as shown in FIGS. 2B and 2C, the reference signal generator 208 may include a digital sine wave generator 232. In FIG. 2B, an analog DAC 236 converts the digital sine wave to an analog signal, which is then filtered and amplified (or, in some examples, attenuated) using an LPF 240 with gain control capabilities. For example, an amplitude control signal is provided to the LPF 240 to control the gain. The LPF 240 may be a first-order filter to reduce cost, or, in some examples, may be a second-order, third-order, or higher-order filter. In other examples, a band-pass filter may be used.

[0027] 2C, a multiplier 244 is provided between the digital sine wave generator 232 and the analog DAC 236. An amplitude control signal is provided to the multiplier 244 to control the gain. The output of the multiplier (corresponding to the amplified digital sine wave) is provided to the analog DAC 236. The analog signal output by the analog DAC 236 is filtered using an LPF 248 without gain control.

[0028] Referring now to FIG. 3 , an example capacitive sensor system 300 (e.g., capacitive sensor system 300 for electronic device 200) is shown that includes a sensor module 304 (e.g., a capacitive sensor) and is configured to provide a driven shield signal 308 to a driven shield 310 in accordance with the present disclosure. A reference signal generator 312 outputs a control signal or reference signal 316 (e.g., a square wave, a modulated waveform such as an analog sine wave, a digital waveform such as a digital sine wave converted to an analog sine wave, etc.). In some examples, the reference signal generator 312 is a DAC configured to generate the reference signal 316. For example, the reference signal generator 312 may be a DAC configured to receive a digital input (e.g., a 4-bit digital input) and convert the digital input to an analog signal. The DAC may be further configured to vary the analog signal such that the magnitude of the reference signal 316 ramps, steps, etc., as described in more detail below.

[0029] The reference signal 316 is provided to the sensor module 304 via a regulator circuit 318 and, in some examples, to an offset control module 320. The offset control module 320 is configured to generate an offset signal 324 based on the reference signal 316. The offset signal 324 is provided to the regulator circuit 318. The reference signal 316 is further coupled to the driven shield 310. In other words, the reference signal 316 according to the present disclosure is provided to the driven shield 310 as the driven shield signal 308.

[0030] The sensor module 304 corresponds to a capacitive sensor (e.g., a capacitive touch circuit) that includes one or more parasitic capacitances (e.g., a parasitic capacitance Crg) that modify the amplitude and phase of a reference signal 316 provided to the regulator circuit 318. In some examples, the reference signal 316 or another signal may be coupled to one or more sense electrodes 328 through a capacitance Crs. When an object (e.g., a finger 332) approaches (i.e., comes into proximity with) and / or contacts a sense electrode 328 of the sensor module 304, the capacitance 336 of the finger 332 further modifies the amplitude and phase of a sense signal 340 that is based on the reference signal 316. Thus, the sensor module 304 generates, as an output voltage, a sense signal 340 that is indicative of whether an object, such as a finger 332, is in contact with the sensor module 304 or, in some examples, the proximity of the finger 332 to the sensor module 304. More specifically, the sense signal 340 is modified according to the detected capacitance 336.

[0031] The regulator circuit 318 detects the sense signal 340 and outputs an indication thereof. In some examples, the regulator circuit 318 detects and outputs a difference between the sense signal 340 and the offset signal 324. For example, the offset control module 320 is configured so that the sense signal 340 and the offset signal 324 (i.e., the respective amplitudes and phases of the sense signal 340 and the offset signal 324) are the same when there is no contact between the sensor module 304 (e.g., the sense electrodes 328) and an object, such as a finger 332. In some examples, the offset control module 320 is configured to adjust the phase and amplitude of the offset signal 324 so that the output of the regulator circuit 318 (e.g., the output signal 344 corresponding to the output current) is substantially zero when there is no contact between the sensor module 304 (e.g., the sense electrodes 328) and an object.

[0032] In other words, the offset control module 320 is configured to adjust the phase and amplitude of the offset signal 324 so that the phase and amplitude of the offset signal 324 match the phase and amplitude, respectively, of the sense signal 340 when the sense electrodes 328 of the sensor module 304 do not sense the proximity of or contact with an object. For example, the parasitic capacitances Crs and Crg change the amplitude and phase of the reference signal 316. The offset control module 320 adjusts the amplitude and phase of the offset signal 324 to compensate for changes to the reference signal 316 caused by the capacitances Crs and Crg. The output of the regulator circuit 318 (i.e., the output signal 344) indicates whether there is contact between the sensor module 304 and the finger 332, or in some examples, the proximity of the finger 332 to the sensor module 304, based on the sense signal 340.

[0033] The regulator circuit 318 receives the reference signal 316 from the reference signal generator 312 (e.g., as an input voltage of the regulator circuit 318). The regulator circuit 318 is configured to adjust a voltage (e.g., the voltage of the reference signal 316) coupled to the sensor module 304. In some examples, the voltage coupled to the sensor module 304 corresponds to a voltage coupled to an optional sensor input / output (I / O) pad 348 that is further coupled to an output of the sensor module 304. Thus, the sense signal 340 is generated based on the reference signal 316 and corresponds to the output voltage of the regulator circuit 318 as further modified by the detected capacitance 336. The regulator circuit 318 generates an output signal 344 (e.g., an output current) indicative of the sense signal 340.

[0034] The sample and hold circuit 350 receives the output signal 344 as an input voltage or signal. The reference signal 316 (and therefore the output signal 344) is a periodic signal, such as a sine wave, a square wave, etc. Thus, the input voltage of the sample and hold circuit 350 fluctuates. The sample and hold circuit 350 is configured to sample the value of the input voltage and generate an output voltage 352 corresponding to the average of the sampled values ​​of the input voltage (i.e., the input voltage average). In this manner, the output voltage 352 is indicative of the output signal 344 and, therefore, the sensed signal 340. The ADC 356 converts the samples of the output voltage 352 into digital values ​​for further processing by the capacitive sensor system 300.

[0035] As described above, a reference signal generator 312 according to the present invention provides a reference signal 316 as a driven shield signal 308 to the driven shield 310. In other words, the voltage of the driven shield 310 does not track the voltage of the sense electrode 328. Instead, the reference signal 316 determines the voltage of the driven shield 310, and the driven shield 210 drives the setting of the voltage of the sense electrode 328.

[0036] Further, the reference signal generator 312 is configured to control the voltage of the reference signal 316 (and, correspondingly, the voltage of the driven shield signal 308). For example, the reference signal generator 312 controls the magnitude, slope, timing, etc. of the reference signal 316. Similarly, the offset control module 320 is configured to control the offset signal 324 based in part on the reference signal 316. The offset control module 320 according to the present disclosure is further configured to control the offset signal 324 to reduce clipping in the output signal 344. For example, the offset control module 320 generates the offset signal 324 such that the rising timing of the offset signal 324 aligns with the rising timing of the reference signal 316 and, correspondingly, with the rising timing of the output signal 344. In other words, the offset control module 320 provides an output current of the output signal 344 at the rising timing of the reference signal 316.

[0037] 4A, the output signal 344 (e.g., an output current corresponding to the sensed signal 340 as described above) may be generated as a step input signal 400. The step input signal 400 may increase (step up) sharply from an initial value (e.g., 0 volts) to the sensed input value. However, in some examples, input values ​​outside of a certain range (e.g., above and below 5 volts as indicated by respective clipping thresholds 404 and 408) may be clipped. In other words, input values ​​that exceed either of the clipping thresholds 404 and 408 may not be accurately detected and received. Therefore, input values ​​within respective clipping regions 412 and 416 are clipped.

[0038] Conversely, the offset signal 324 (e.g., an offset current) may be generated as a ramp offset signal 420. The ramp offset signal 420 decreases from an initial value (e.g., 0 volts) as the step input signal 400 increases. Because the ramp offset signal 420 (as the offset signal 324) is coupled to the output of the regulator circuit 318, as described above and shown in FIG. 3 , the ramp offset signal 420 modifies the output signal 344. For example, the ramp offset signal 420 generated by the offset control module 320 is added (i.e., summed) to the output signal 344 as the output signal 344 increases from the initial value to the sensed input value. Because the ramp offset signal 420 has an opposite polarity to the corresponding step input signal 400, the ramp offset signal 420 reduces the magnitude of the step input signal 400 below the clipping region 412. For example, the step input signal 400 modified by the ramp offset signal 420 is shown at 424. As shown at 428, a portion of the step input signal 400 may still be clipped.

[0039] As shown in FIG. 4B , the output signal 344 may be generated as a ramping input signal 432. The ramping input signal 432 may gradually increase (ramp up) from an initial value (e.g., 0 volts) to the sensed input value. Input values ​​within the respective clipping regions 412 and 416 are clipped as described above. The ramping offset signal 420 reduces the magnitude of the ramping input signal 432 below the clipping region 412. For example, the ramping input signal 432 modified by the ramping offset signal 420 is shown at 436. The ramping offset signal 420 generated by the offset control module 320 is added (i.e., summed) to the output signal 344 as the output signal 344 increases from the initial value to the sensed input value.

[0040] The ramp offset signal 420 may be provided at the rise time of the reference signal 316 such that the rise time of the ramp offset signal 420 approximately aligns with the rise time of the ramp input signal 432. For example, as shown, the negative slope of the ramp offset signal 420 is complementary to the positive slope of the ramp input signal 432. For example, the reference signal generator 312 may be configured to generate the reference signal 316 with a predetermined slope such that the ramp input signal 432 also has a predetermined slope. Conversely, the offset control module 320 may be configured to generate the ramp offset signal 420 with a slope that is complementary (e.g., opposite) to the predetermined slope of the ramp input signal 432. In other words, as the ramp input signal 432 increases, the ramp offset signal 420 decreases to offset the increase in the ramp input signal 432. Thus, the ramp input signal 432, as modified by the ramp offset signal 420, remains below the clipping region 412 and is not clipped.

[0041] In this manner, the reference signal generator 312 is configured to control the voltage of the reference signal 316 (and, correspondingly, the voltages of the drive shield signal 308 and the sense signal 340) such that the output signal 344 is configured to reduce or eliminate clipping. For example, the reference signal generator 312 may be configured so that the magnitude of the reference signal 316 increases (e.g., steps or ramps up) over time. In one example, if the reference signal 316 is a periodic signal such as a sine wave or square wave, the magnitude of the periodic signal may be controlled to ramp up at a rate corresponding to the slope (e.g., a predetermined gradient or slope) of the ramping input signal 432. Conversely, the offset control module 320 is configured to generate the offset signal 324 as a ramp signal to prevent the output signal 344 from reaching a clipping region. In one example, the offset control module 320 is configured so that the slope of the offset signal 324 matches (e.g., is complementary to) the slope of the output signal 344.

[0042] The above description is merely exemplary in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the present disclosure can be embodied in a variety of forms. Accordingly, while the present disclosure includes specific examples, the true scope of the disclosure should not be so limited, as other variations will become apparent upon study of the drawings, the specification, and the following claims. It should be understood that one or more steps in a method may be performed in a different order (or simultaneously) without altering the principles of the present disclosure. Furthermore, although each of the embodiments is described above as having specific features, any one or more of these features described with respect to any embodiment of the present disclosure can be implemented in and / or combined with any feature of any other embodiment, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and substitution of one or more embodiments for one another remains within the scope of the present disclosure.

[0043] Spatial and functional relationships between elements (e.g., between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including "connected," "engaged," "coupled," "adjacent," "next to," "above," "on," "below," and "disposed." Unless expressly described as "direct," when a relationship between a first element and a second element is described in the above disclosure, the relationship can be a direct relationship where no other intervening elements exist between the first and second elements, but can also be an indirect relationship where one or more intervening elements (either spatially or functionally) exist between the first and second elements. As used herein, the phrase "at least one of A, B, and C" should be interpreted to mean the logical (A OR B OR C) using a non-exclusive logical OR, and not as meaning "at least one of A, at least one of B, and at least one of C."

[0044] In the drawings, the direction of the arrows, as indicated by the arrowhead, generally indicates the flow of information (such as data or instructions) of interest to the diagram. For example, an arrow may point from element A to element B if element A and element B exchange various information, but the information sent from element A to element B is relevant to the diagram. This unidirectional arrow does not imply that other information is not sent from element B to element A. Furthermore, for information sent from element A to element B, element B may send a request for the information or an acknowledgment of receipt to element A.

[0045] For the purposes of this application, the following definitions are included, and the term "module" or "controller" may be interchanged with the term "circuitry." The term "module" may refer to, be a part of, or include an Application Specific Integrated Circuit (ASIC), a digital, analog, or mixed analog / digital discrete circuit, a digital, analog, or mixed analog / digital integrated circuit, a combinational logic circuit, a field programmable gate array (FPGA), a processor circuit (shared, dedicated, or group) that executes code, a memory circuit (shared, dedicated, or group) that stores code to be executed by the processor circuit, other suitable hardware components that provide the described functionality, or a combination of some or all of the above, such as a system-on-chip.

[0046] A module may include one or more interface circuits. In some examples, the interface circuit may include a wired or wireless interface connected to a local area network (LAN), the Internet, a wide area network (WAN), or a combination thereof. The functionality of any given module of the present disclosure may be distributed among multiple modules connected via interface circuits. For example, multiple modules may enable load balancing. In a further example, a server (also known as a remote or cloud) module may perform some functionality on behalf of a client module.

[0047] The term code, as used above, may include software, firmware, and / or microcode, and may refer to programs, routines, functions, classes, data structures, and / or objects. The term shared processor circuit encompasses a single processor circuit that executes some or all code from multiple modules. The term group processor circuit encompasses a processor circuit that executes some or all code from one or more modules in combination with additional processor circuits. References to multiple processor circuits encompass multiple processor circuits on separate dies, multiple processor circuits on a single die, multiple cores of a single processor circuit, multiple threads of a single processor circuit, or combinations of the above. The term shared memory circuit encompasses a single memory circuit that stores some or all code from multiple modules. The term group memory circuit encompasses a memory circuit that stores some or all code from one or more modules in combination with additional memory.

[0048] The term memory circuit is a subset of the term computer-readable medium. As used herein, the term computer-readable medium does not encompass transitory electrical or electromagnetic signals propagating through a medium (such as in a carrier wave), and thus the term computer-readable medium may be considered tangible and non-transitory. Non-limiting examples of non-transitory tangible computer-readable media are non-volatile memory circuits (such as flash memory circuits, erasable programmable read-only circuits, or masked read-only circuits), volatile memory circuits (such as static random access memory circuits or dynamic random access memory circuits), magnetic storage media (such as analog or digital magnetic storage tape or hard disk drives), and optical storage media (such as CDs, DVDs, or Blu-ray discs).

[0049] The apparatus and methods described in this application may be implemented partially or completely by a special-purpose computer created by configuring a general-purpose computer to perform one or more specific functions embodied in a computer program. The above-described functional blocks, flowchart elements, and other elements function as software specifications and can be converted into a computer program by the routine work of a person skilled in the art or a programmer.

[0050] A computer program includes processor-executable instructions stored on at least one non-transitory, tangible, computer-readable medium. A computer program may also include or depend on stored data. A computer program may encompass a basic input / output system (BIOS) that interacts with hardware in a special-purpose computer, device drivers that interact with specific devices in a special-purpose computer, one or more operating systems, user applications, background services, background applications, etc.

[0051] A computer program may include (i) parsed text, such as HTML (hypertext markup language), XML (extensible markup language), or JSON (JavaScript Object Notation), (ii) assembly code, (iii) object code generated from source code by a compiler, (iv) source code executed by an interpreter, or (v) source code compiled and executed by a runtime compiler. By way of example only, the source code may be written using syntax from languages ​​including C, C++, C#, Objective-C, Swift, Haskell, Go, SQL, R, Lisp, Java®, Fortran, Perl, Pascal, Curl, OCaml, Javascript®, HTML5 (Hypertext Markup Language 5th revision), Ada, ASP (Active Server Pages), PHP (PHP: Hypertext Preprocessor), Scala, Eiffel, Smalltalk, Erlang, Ruby, Flash®, Visual Basic®, Lua, MATLAB®, SIMULINK®, and Python®. [Explanation of symbols]

[0052] 100 Capacitive Sensor System 104 Detection circuit 108 Drive Shield Circuit 110 Capacitive Sensor 112 Operational Amplifier 116 Powered Shield 200 Electronic Devices 204 Sensor Module 208 Reference signal generator 210 Reference Signal 212 Offset Control Module 216 optional second reference signal generator 218 Sensing signal 220 offset signal 224 Regulator Circuit 228 Output Signal 232 Digital Sine Wave Generator 236 Analog DAC 240 LPF 244 Multiplier 248 LPF 300 Capacitive Sensor System 304 Sensor Module 308 Drive Shield Signal 310 Drive Shield 312 Reference signal generator 316 Reference Signal 318 Regulator Circuit 320 Offset Control Module 324 offset signal 328 Sensing electrode 332 fingers 336 Capacitance 340 sensing signal 344 output signal 352 Output Voltage 356 ADC 400 step input signal 404 Clipping Threshold 412 Clipping Region 420 Lamp Offset Signal 432 Lamp input signal

Claims

1. 1. A capacitive sensor system, comprising: a capacitive sensor including a sensing electrode and a shield electrode; a regulator circuit configured to regulate a voltage across the capacitive sensor and generate an output signal based on an output of the capacitive sensor; a reference signal generator configured to generate a reference signal, provide the reference signal to the capacitive sensor via the regulator circuit, and provide the reference signal to the shield electrode as a driven shield signal; an offset control module configured to generate an offset signal to modify the output signal; Including, the offset control module is coupled to an output of the regulator circuit for modifying the output signal; the offset control module generates the offset signal, the offset control module adding the offset signal to the output signal to reduce a magnitude of the output signal; The offset control module adds the offset signal to the output signal to reduce the magnitude of the output signal below a clipping region.

2. 1. A capacitive sensor system, comprising: a capacitive sensor including a sensing electrode and a shield electrode; a regulator circuit configured to regulate a voltage across the capacitive sensor and generate an output signal based on an output of the capacitive sensor; a reference signal generator configured to generate a reference signal, provide the reference signal to the capacitive sensor via the regulator circuit, and provide the reference signal to the shield electrode as a driven shield signal; an offset control module configured to generate an offset signal to modify the output signal; Including, the offset control module is coupled to an output of the regulator circuit to modify the output signal; the offset control module generates the offset signal, the offset control module adding the offset signal to the output signal to reduce a magnitude of the output signal; A capacitive sensor system, wherein the offset control module is configured to add the offset signal to the output signal as the output signal increases from an initial value to a sensed input value.

3. the regulator circuit includes a current conveyor coupled to the capacitive sensor; The capacitive sensor system of claim 1 or 2, wherein the current conveyor is configured to adjust the voltage of the capacitive sensor based on the reference signal provided by the reference signal generator.

4. The capacitive sensor system of claim 1 or 2, wherein the reference signal generator comprises a digital-to-analog converter.

5. The capacitive sensor system according to claim 1 , wherein the reference signal generator generates the reference signal as a periodic signal.

6. 3. The capacitive sensor system of claim 1, wherein the capacitive sensor generates an output as a sensed signal corresponding to the reference signal as modified according to at least one of contact with an object and proximity of an object.

7. The capacitive sensor system of claim 1 or 2, wherein the offset control module generates the offset signal such that a rising timing of the offset signal matches a rising timing of the output signal.

8. 8. The capacitive sensor system of claim 7, wherein the offset control module generates the offset signal at a rising timing of the reference signal to generate the offset signal such that the rising timing of the offset signal aligns with the rising timing of the output signal.

9. The capacitive sensor system of claim 1 or 2, wherein the regulator circuit generates the output signal as one of a step input signal and a ramp input signal.

10. The capacitive sensor system of claim 1 or 2, wherein the reference signal generator is configured to generate the reference signal having a predetermined slope.

11. The capacitive sensor system of claim 10 , wherein the regulator circuit generates the output signal having a slope corresponding to the predetermined slope of the reference signal.

12. A capacitive sensor system comprising: a capacitive sensor including a sensing electrode and a shield electrode; a regulator circuit configured to regulate a voltage across the capacitive sensor and generate an output signal based on an output of the capacitive sensor; a reference signal generator configured to generate a reference signal, provide the reference signal to the capacitive sensor via the regulator circuit, and provide the reference signal to the shield electrode as a driven shield signal; an offset control module configured to generate an offset signal to modify the output signal; Including, the offset control module is coupled to an output of the regulator circuit for modifying the output signal; the offset control module generates the offset signal, the offset control module adding the offset signal to the output signal to reduce a magnitude of the output signal; the reference signal generator is configured to generate the reference signal having a predetermined slope; The regulator circuit generates the output signal having a slope corresponding to the predetermined slope of the reference signal.

13. A capacitance sensor system as described in claim 11 or 12, wherein the regulator circuit generates the output signal having a positive slope, and the offset control module generates the offset signal having a negative slope complementary to the positive slope of the output signal.

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