Force sensing circuit

Abstract

This disclosure relates to circuitry for biasing a sensor, including a bias generator module configured to receive a supply voltage and generate a bias voltage for biasing the sensor. The circuitry also includes a control module configured to compare a voltage indicating the supply voltage with a threshold voltage and output a control signal to the bias generator module based on the comparison. The bias generator module is configured to control the bias voltage based on the control signal.

Description

Technical Field

[0001] This disclosure relates to the field of force sensing circuits and systems. Background Technology

[0002] Traditional portable devices (such as mobile phones, tablets, remote controllers, video game controllers, etc.) typically include mechanical buttons for users to control the device. These mechanical buttons are prone to wear and tear, and are easily damaged and malfunction due to the intrusion of water, dust, and / or debris. Therefore, manufacturers are increasingly seeking alternative solutions to facilitate user interaction with portable devices.

[0003] One way to facilitate this type of interaction is to provide so-called “virtual buttons” in the form of force sensors. Force sensors can be provided as part of a portable device in place of mechanical buttons. Force sensors can be configured to detect user interaction with the sensor (e.g., the sensor being touched or pressed) and cause the portable device to activate some function in response to the detected interaction. Since there are no moving parts like mechanical buttons, such virtual buttons offer advantages over mechanical buttons. This can reduce wear and tear and increase the lifespan of the portable device. The use of force sensors can also help improve the water resistance of the portable device, as mechanical buttons can provide a significant entry point for fluids. Furthermore, mechanical buttons are relatively large components in portable devices, so smaller alternatives (such as force sensors) can free up space for additional components. For example, in mobile phones, this additional space might be occupied by an increased number of 5G antennas.

[0004] Manufacturers are further seeking to provide increased interactivity between users and portable devices, and the use of force sensors can facilitate additional or alternative methods of user interaction with portable devices. For example, one or more force sensors can be used to provide a "virtual slider" type of functionality along one or more surfaces of the portable device, providing an interface area for the portable device in addition to, for example, a touchscreen. To ensure that the user experience is not significantly altered by the introduction of force sensors, the "virtual interface" provided by the force sensors should appear and feel to the user as if a mechanical button or other mechanical interface were present, rather than a virtual button or virtual button interface.

[0005] Force sensors therefore detect forces on the device to determine user interaction with the device, such as touching, pressing, or squeezing it. The forces applied by the user are typically small, and therefore it is beneficial to configure the force sensor to have the maximum possible sensitivity to detect user interaction.

[0006] Another important consideration is that portable devices should respond to user interactions in a consistent manner; that is, the device's response to a particular user interaction (such as touching a virtual button) should always be the same. If such consistent responses are not maintained or if the force sensor fails to detect a user interaction, the user experience may be degraded.

[0007] Furthermore, portable devices typically draw power from onboard batteries, so the power supply for such devices is usually limited. Therefore, the power consumption of force sensors used in portable devices should be low.

[0008] Therefore, industrial applications require circuits and systems that balance the need for low power consumption with the need to maintain consistent and reliable sensitivity performance.

[0009] Therefore, embodiments of this disclosure relate to devices and systems for sensing that at least mitigate some of the aforementioned problems.

[0010] According to a first aspect, the present invention provides a circuit for a bias sensor, comprising:

[0011] A bias generator module configured to receive a supply voltage and generate a bias voltage for biasing the sensor; and

[0012] A control module is configured to compare a voltage indicating the supply voltage with a threshold voltage and to output a control signal to a bias generator module based on the comparison.

[0013] The bias generator is configured to control the bias voltage based on a control signal.

[0014] The bias generator module is operable to adjust the bias voltage from a first defined bias voltage value to a second defined bias voltage value based on a control signal.

[0015] The second defined bias voltage value can be less than the first defined bias voltage value, and the control module can be configured to output a control signal in response to the comparison indicating that the supply voltage has decreased to below the threshold voltage.

[0016] The second defined bias voltage value can be greater than the first defined bias voltage value, and the control module can be configured to output a control signal in response to the comparison indicating that the supply voltage has increased above the threshold voltage.

[0017] The control module can be configured to apply a time delay before the output control signal.

[0018] The time delay can be predetermined based on the expected rate of increase in the supply voltage value.

[0019] The control module can be configured to monitor the supply voltage to determine whether the supply voltage is increasing or decreasing.

[0020] The control module can be configured to pause the output of the control signal in response to the control module determining that the supply voltage value is decreasing during the time delay.

[0021] The control module can be configured to not output a control signal in response to the control module determining that the supply voltage has decreased below the voltage threshold during the time delay period.

[0022] The control module can be configured to select the threshold voltage value based on whether the supply voltage is increasing or decreasing.

[0023] In response to the control module determining that the supply voltage is decreasing, the control module may be operable to select a first threshold voltage value.

[0024] In response to the control module determining that the supply voltage is increasing, the control module can be operated to select a second threshold voltage value that is greater than the first threshold voltage value.

[0025] Alternatively, in response to the control module determining that the supply voltage is increasing, the control module may be operable to select a first threshold voltage value.

[0026] The control module can be configured to select the value of the threshold voltage based on the magnitude of the supply voltage.

[0027] The bias generator module can be configured to generate bias voltages with multiple defined bias voltage values.

[0028] The circuit may include a memory for storing a plurality of threshold voltage values ​​corresponding to a plurality of defined bias voltage magnitudes, and the control module may be configured to select one of the plurality of threshold voltage values ​​to compare with the supply voltage based on the magnitude of the supply voltage and whether the magnitude of the supply voltage is increasing or decreasing.

[0029] Multiple threshold voltage values ​​can be predetermined based on the voltage drop across the bias generator module.

[0030] The control module can be configured to receive a signal indicating the bias voltage.

[0031] The control module can be configured to select a normalization function based on the bias voltage.

[0032] The circuit may include a processing module configured to receive an output signal from a sensor and also configured to receive a normalization function from a control module; and the processing module may be configured to apply the normalization function to the output signal to generate a normalized output signal.

[0033] The circuit may include a memory that includes a plurality of normalization functions corresponding to a plurality of defined bias voltage values, and the control module may be configured to select one of the plurality of normalization functions based on the bias voltage values.

[0034] The threshold voltage may include the minimum of a plurality of threshold voltage values, and in response to the comparison indicating that the supply voltage has decayed below the minimum of the plurality of threshold voltage values, the control module may be configured to control the processing module not to process the output signal.

[0035] The control module may include a hysteresis comparator configured to compare a supply voltage with a threshold voltage and output a control signal based on the comparison.

[0036] Control signals may include latch signals.

[0037] For example, the sensor could be a force sensor.

[0038] The circuit can be implemented as an integrated circuit.

[0039] According to a second aspect, the present invention provides a power supply unit comprising: a circuit according to the first aspect; and a battery configured to output a supply voltage.

[0040] According to a third aspect, the present invention provides an electronic device comprising: a circuit according to the first aspect; a battery configured to output a supply voltage; and a sensor configured to receive a bias voltage.

[0041] The electronic device can be portable or battery-powered.

[0042] The electronic device can be one of the following: a tablet computer, a laptop computer, a smartphone, or a smartwatch.

[0043] According to a fourth aspect, the present invention provides a circuit for normalizing the output signal of a force sensor, comprising:

[0044] A bias generator module is configured to receive a supply voltage and generate a bias voltage for the bias force sensor.

[0045] The control module is configured to receive a voltage indicating a bias voltage and select a normalization function based on the bias voltage; and

[0046] The processing module is configured to receive the output signal and the normalization function;

[0047] The processing module is further configured to apply the normalization function to the output signal to normalize the output signal.

[0048] According to a fifth aspect, the present invention provides a sensor module comprising:

[0049] sensor;

[0050] A bias generator configured to receive a supply voltage and generate a bias voltage for biasing a sensor; and

[0051] A controller is configured to compare a signal voltage indicating the supply voltage with a threshold voltage, and to output a control signal to a bias generator based on the comparison;

[0052] The bias generator is configured to control the bias voltage based on a control signal.

[0053] To better understand the examples of this disclosure, and to more clearly illustrate how the examples can be implemented, reference will now be made only by way of example to the following figures, in which:

[0054] Figure 1 An example of a circuit for a bias force sensor is shown;

[0055] Figure 2 Another example of a circuit for a bias force sensor is shown;

[0056] Figure 3 An example of a hysteresis comparator is shown for comparing a supply voltage with a reference voltage;

[0057] Figures 4a to 4c It is shown Figure 2 Timing diagram of the circuit operation;

[0058] Figure 5 It is shown Figure 2 Another timing diagram of the circuit operation; and

[0059] Figure 6 An example of an electronic device according to an implementation scheme is shown.

[0060] The following description sets forth exemplary embodiments according to this disclosure. Other exemplary embodiments and implementations will be apparent to those skilled in the art. Furthermore, those skilled in the art will recognize that various equivalent techniques may be applied in place of or in combination with the embodiments discussed below, and all such equivalents will be considered to be covered by this disclosure.

[0061] As mentioned above, force sensors provide an alternative means of enabling interaction between a user and devices such as portable devices. Many different types of force sensors have recently been developed. For example, resistive force sensors, inductive force sensors, capacitive force sensors, resistive-inductive-capacitive force sensors, and piezoelectric force sensors have been explored as alternatives for enabling user interaction. For any of these force sensors to become a viable option for providing user interaction, the force sensor should be configured to have appropriate sensitivity to detect user interaction during use.

[0062] Figure 1 An example of circuitry 100 for a bias force sensor 130 is shown. Circuitry 100 includes a power supply (PS) 110 and a bias generator module (BGM) 120. Power supply 110 may include any suitable device for storing and supplying power, such as a battery B. 110 Circuit 100 can form part of a portable electronic device, and therefore components of the electronic device (such as a touchscreen, speaker, microphone, etc.) can draw current from power source 110. Figure 1 (represented by I1 in the text). Power supply 110 will include some parasitic resistance, in Figure 1 The middle is composed of resistor R 110 This is indicated. However, it should be understood that R shown in power supply 110... 110 This is for illustrative purposes, and constitutes the "lumped resistance" R. 110 Parasitic resistance can exist throughout circuit 100 and / or in electronic devices containing circuit 100.

[0063] The bias generator module 120 may include any suitable regulator to receive the input supply voltage V. S And generate a bias voltage V at a defined nominal value. BIAS In one embodiment, the bias generator module 120 may include a linear voltage regulator. In another embodiment, the bias generator module 120 may include a low dropout regulator (LDO). The bias generator module 120 generates a bias voltage V. BIAS We supply force sensor 130.

[0064] The bias voltage V applied to the force sensor 130 BIAS A reference level for the operation of force sensor 130 is established so that a force applied to force sensor 130 (e.g., touch or press) can generate a detectable output signal V. OUT Therefore, the output signal V from the force sensor 130 OUT It can instruct user interaction. Then, V can be used. OUT Provided to downstream processing circuits / modules, which can be configured to respond to V OUTProvide feedback to users and / or launch certain features.

[0065] The bias generator 120 typically includes a regulator with a relatively high power supply rejection ratio (PSRR), such that the voltage V supplied from the power supply 110... S Any noise present in the bias generator module 120 is limited as much as possible. In one embodiment, the bias generator module 120 may include an LDO. The LDO may be configured to have a relatively high PSRR, such that the supply voltage V S Ripple or noise present in the circuit can be suppressed to a relatively high degree by an LDO. Therefore, the PSRR of an LDO can limit the supply voltage V. S The present, transferred to the bias voltage V BIAS The noise level. Those skilled in the art will certainly understand that the LDO is only one possible example of a suitable bias generator module 120, and any voltage regulator that presents a suitable PSRR can also be used.

[0066] Therefore, the bias generator module 120, including the LDO, can exhibit useful characteristics related to noise suppression. However, the performance of the LDO is limited by its voltage drop. As those skilled in the art will understand, the voltage drop must be maintained at the input voltage (e.g., V) supplied to the LDO in order to reliably regulate the output voltage. S ) and output voltage (e.g., V) BIAS The minimum margin between the output voltage and the input voltage. As those skilled in the art will also understand, any linear voltage regulator will be subject to a similar limitation, namely, that an appropriate amount of voltage margin should be maintained between the regulator's output voltage and its input voltage in order to regulate the output voltage to the expected nominal level.

[0067] In applications where the input voltage is supplied by a consistent and fixed power source, the input voltage can be maintained at a constant level. Therefore, by utilizing such an input voltage, a margin can be maintained between the LDO's input and output voltages, ensuring that the LDO never enters "dropout" operation.

[0068] However, in applications where the input voltage is supplied by a power source with a finite and decaying voltage (such as a battery), the difference between the LDO's input and output voltages decreases over time as the power source naturally discharges and is used. As a result of this discharge of the power source, the difference between the input and output voltages may approach the LDO's voltage drop.

[0069] Furthermore, other components of the host device including circuit 100, such as a display, screen, and speaker, can draw current I1 from the battery, which can increase the supply voltage V to the bias generator module 120. S Due to parasitic resistance R 110The effect is reduced. Therefore, the supply voltage V S With bias voltage V BIAS The difference between them can be reduced and approach the pressure drop.

[0070] If the margin drops below the voltage drop level, the LDO will enter "dropout" operation, in which the LDO may be unable to regulate the output voltage to the desired nominal level.

[0071] In circuit 100, if the bias generator module 120 enters the "voltage drop" operation, the bias voltage V BIAS The force sensor 130 will not be supplied at the expected level. This may cause the sensitivity of the force sensor 130 to become unpredictable, and may result in false alarms or the force sensor 130 failing to detect user interaction.

[0072] One option to accommodate the input voltage from the attenuation source to the bias generator 120 could be to use V BIAS Set to an appropriately low value. Input supply voltage V S With bias voltage V BIAS The difference between them can be configured to provide the difference between the two voltages (i.e., V). S -V BIAS Sufficient margin not falling below the voltage drop. However, the sensitivity of force sensor 130 is V. BIAS The function, therefore V BIAS Maintaining a low value may result in low sensitivity of the force sensor 130, which in turn leads to a poor user experience because user interactions with the force sensor 130 (such as touch) may not be detected.

[0073] Figure 2 Another example of circuitry 200 for a bias force sensor 130 is shown. Circuitry 200 includes a bias generator module 120, which is configured to interact with a reference... Figure 1 The circuit 100 shown operates in essentially the same manner as described to generate the bias voltage V of the bias force sensor 130. BIAS .

[0074] The bias generator module 120 can receive a supply voltage V from a suitable power source. S And generate a bias voltage V BIAS Circuit 200 shows the supply voltage V supplied by the power supply rail. S It should be understood that the power supply rail can be powered by any suitable power source (such as...). Figure 1 The circuit 100 shown is powered by a power supply 110. In one embodiment, the supply voltage V S It can be obtained from the battery.

[0075] As discussed above, force sensor 130 may include any sensor capable of detecting force applied by a user (e.g., touch or pressure from the sensor). In some embodiments, force sensor 130 may include any of a resistive force sensor, an inductive force sensor, a capacitive force sensor, a resistive-inductive-capacitive force sensor, and a piezoelectric force sensor. In one embodiment, force sensor 130 may include a resistive force sensor (such as a Wheatstone bridge-based resistive force sensor) configured to detect force from user interaction and generate V. OUT Further processing will be carried out.

[0076] In one embodiment, force sensor 130 may include a force sensor unit comprising a plurality of force sensors. Each of the plurality of force sensors may be configured to receive a bias voltage V. BIAS To bias each force sensor.

[0077] As discussed regarding circuit 100, minimizing the bias voltage V BIAS The noise in the sensor can improve the performance and sensitivity of the force sensor 130. Therefore, the bias generator 120 can be configured to have a relatively high PSRR, so that the supply voltage V S Noise and / or ripple on the synthesized bias voltage V BIAS The bias is suppressed as much as possible. Therefore, in some embodiments, the bias generator 120 may include a linear voltage regulator, such as an LDO. However, as discussed above, the performance of an LDO may be limited by its voltage drop. Since the sensitivity of the force sensor depends on the bias voltage V... BIAS Therefore, the LDO entering the "voltage drop" will cause the bias voltage V to... BIAS This reduces the sensitivity of the force sensor 130, which in turn leads to a decrease in sensitivity.

[0078] Circuit 200 includes a control module (CON) 140. Control module 140 is configured to receive a supply voltage V. S And the supply voltage V S Or indicate the supply voltage V S Voltage and threshold voltage V TH In one embodiment, the threshold voltage can be selected by the control module 140 from the memory 150 for comparison. It should be noted that the supply voltage V indicated herein... S The voltage means that it also includes the supply voltage V. S The control module 140 is also configured to output a control signal CTL to the bias generator module 120 based on the comparison. The bias generator module 120 is also configured to control the bias voltage V based on the control signal CTL. BIAS .

[0079] As discussed above, with a supply voltage V S In the case of attenuation from sources such as batteries, V S It will decrease, and eventually V S With V BIAS The difference may be less than the voltage drop of the bias generator module 120. Therefore, circuit 200 is configured with a control module 140, which supplies voltage V. S Alternatively, the voltage derived from the supply voltage can be compared with a first suitable threshold voltage. In some embodiments, the threshold voltage is set to a predefined value higher than the voltage drop across the bias generator module 120. Therefore, the supply voltage V S The voltage drops below the first threshold voltage, indicating the supply voltage V. S The value has decayed to the supply voltage V. S With bias voltage V BIAS The difference between them is close to the level of the voltage drop of the bias generator module 120. Therefore, in response to the supply voltage V S When the voltage drops below the first threshold voltage, the control module 140 can output an appropriate control signal to control the bias generator module 120 to output a bias voltage V at a lower value. BIAS In order to increase the bias voltage V BIAS With supply voltage V S The difference between them prevents the bias generator 120 from entering "voltage drop" operation.

[0080] In one embodiment, the bias generator module 120 may be operable to output a bias voltage V at a first defined value or a second defined value different from the first defined value. BIAS The bias generator module 120 can also be operated to generate a bias voltage V based on the control signal CTL. BIAS Adjust from the first limit value to the second limit value.

[0081] bias voltage V BIAS The second limiting value can be less than the first limiting value, and in response to determining the supply voltage V S Once the voltage has dropped below its associated threshold voltage, the control module 140 can output a control signal CTL to the bias generator module 120 to control the bias generator module 120 to adjust the bias voltage V. BIAS The value changes from a first defined value to a second defined value. In response to receiving the control signal CTL, the bias generator module 120 can output V from the first defined value. BIAS Switch to output V with the second limited value BIAS .

[0082] By outputting V at the second (lower) limiting value BIAS Supply voltage VS With bias voltage V BIAS The difference between them can be increased, making the difference between the two voltages greater than the voltage drop. Therefore, when the bias voltage V... BIAS When at the second lower value, a further reduction in the supply voltage can be accommodated (e.g., as a result of further battery discharge) before the bias generator module 120 enters the "voltage drop" operation.

[0083] Similarly, the bias generator module 120 can be configured to generate a bias voltage V based on the control signal CTL. BIAS The voltage is adjusted from a second defined voltage value to a first defined voltage value. In one embodiment, in response to determining the supply voltage V... S The voltage has been increased to a second threshold voltage (which may be the same as or different from the first threshold voltage), and the control module 140 can output a control signal CTL to control the bias generator module 120 to increase the bias voltage V. BIAS The value changes from the second limiting value to the first limiting value. In response to receiving this control signal CTL, the bias generator module 120 can output V at the second limiting value. BIAS Switch to output V with the first limited value BIAS .

[0084] In some implementations, the bias generator module 120 can be adjusted based on the supply voltage V. S The level outputs V with multiple different constrained values. BIAS This will be explained in more detail below.

[0085] refer to Figure 2 Circuit 200 may include a memory (MEM) 150, which may be configured to store a plurality of threshold voltage values ​​for use by control module 140. In one embodiment, control module 140 may be configured to select one of the plurality of threshold voltage values ​​to match the supply voltage V. S The control module 140 can also be configured to store one or more threshold voltage values ​​in memory 150 for comparison with the supply voltage VS.

[0086] As will be described in more detail below, in one embodiment, the control module 140 can supply voltage V based on a specific point in time. S The value of the quantity (e.g., supply voltage V) S The threshold voltage value is selected based on the current or present value of the supply voltage. In one embodiment, multiple threshold voltage values ​​can be stored in a lookup table (LUT), and the control module 140 can be configured to select a threshold voltage value based on the supply voltage V. S The current value is selected from the lookup table to determine the voltage threshold.

[0087] Therefore, multiple voltage thresholds can be pre-programmed and stored in memory 150. This can be determined based on the voltage drop V. DO The bias voltage value V generated by the bias generator module 120 BIAS To calculate the threshold voltage value. Threshold voltage value V TH-N The following formula can be used for calculation:

[0088] V TH-N --V x +V Do +V BIAS-N (1)

[0089] Where V X It is a defined voltage value, V DO It is the voltage drop across the bias generator module 120, while V BIAS-N It is the bias voltage value output by the bias generator module 120.

[0090] Therefore, V X It can be configured to be higher than the voltage drop V DO An appropriate value. For example, V X It can be approximately 100mV. This is in response to the supply voltage V. S Decay to exemplary V TH-N Values ​​below V X The 100mV margin ensures that the control module 140 has sufficient time to output a control signal CTL to the bias generator module 120 before the supply voltage decays to the extent that the bias generator module 120 enters "dropout" operation, in order to set the bias voltage V. BIAS From, for example, a first value decreasing to a second, smaller value.

[0091] As the bias voltage decreases, the threshold voltage also decreases by a corresponding amount according to equation (1). Therefore, it can be compared with multiple bias voltage values ​​(V) generated by the bias generator 120. BIAS-1 V BIAS-2 ...V BIAS-N Correspondingly, multiple voltage thresholds (V) are calculated. TH-1 V TH-2 ...V TH-N In other implementations, for different bias voltage values, V X The values ​​can be different. Depending on the given application of circuit 200, an appropriate V can be determined for each bias voltage value. X value.

[0092] Figure 3 Hysteresis comparator 300 is shown, and in some embodiments, the hysteresis comparator may be included in the control module 140 of circuit 200. Hysteresis comparator 300 can be configured to receive a supply voltage V. SOr indicate the supply voltage V S The voltage, and will supply voltage V S Or indicate the supply voltage V S The voltage and the reference voltage V REF Compare. Reference voltage V REF Corresponding to the threshold voltage value V TH-N An appropriate threshold voltage value is selected. Therefore, the control module 140 can select a voltage threshold from the memory 150 and use this value as a reference voltage V. REF Input to hysteresis comparator 300.

[0093] Alternatively, the reference voltage V REF It can be a fixed voltage value, and indicates the supply voltage V. S The voltage can vary. For example, memory 150 may include an indicator of the supply voltage V. S Multiple predetermined voltage values. The control module 140 can be configured to base the supply voltage V on... S Select the supply voltage V S One of several predetermined voltage values ​​is used to compare with a fixed voltage reference voltage V. REF Compare. With the supply voltage V S The control module 140 can adjust the value of the input voltage V by adjusting the input voltage V. S Choose different predetermined voltage values ​​from a plurality of predetermined voltage values.

[0094] Based on the supply voltage V S (or the voltage indicating it) and the reference voltage V REF In comparison, the hysteresis comparator 300 can output a control signal CTL to the bias generator module 120. Figure 3 The control signal CTL is shown to be a two-level (i.e., binary signal) that can take a high or low value. However, according to this disclosure, the control signal CTL can include any suitable signal for controlling the bias generator module 120.

[0095] In the operation of the hysteresis comparator 300, the supply voltage V S The value may drop to the reference voltage V. REF The following indicates the supply voltage V S The bias generator module 120 is approaching the level at which it will enter a voltage drop phase. In response, the hysteresis comparator 300 outputs a control signal CTL to cause the bias generator module 120 to bias the voltage V. BIASThe transition occurs from, for example, a first defined value to a second defined value. The control signal CTL can be directly output to the bias generator module 120, or alternatively, the control signal CTL can be output to intermediate processing circuitry before being supplied to the bias generator module 120. The second defined value can include a smaller value than the first defined value. Therefore, this transition may increase the supply voltage V. S With bias voltage V BIAS This provides a margin between the bias and bias generator modules and prevents them from entering a "dropout" operation.

[0096] When the supply voltage V S The value rises to the reference voltage V REF The above is the hysteresis voltage H that is higher than that of the hysteresis comparator 300. V When the quantity is equal to the specified value, the hysteresis comparator 300 outputs a control signal CTL to the bias generator module 120, so that the bias generator module 120 biases the voltage V. BIAS The second bias voltage limit value is changed to the first bias voltage limit value.

[0097] Since comparator 300 is a hysteresis comparator, it is suitable for applications with a supply voltage V. S When it drops, it is related to the supply voltage V S The reference voltage V for comparison REF The response appears to be different (less than) to the supply voltage V. S Rise with supply voltage V S The reference voltage V for comparison REF The value of the response.

[0098] As will be described in more detail below, the hysteresis comparator 300 can therefore apply a voltage hysteresis H. V To prevent the bias voltage V output by the bias generator module 120 BIAS Undesirable frequent transitions. Alternatively or additionally, the hysteresis comparator 300 may apply a time hysteresis H. T The control signal CTL is output to the bias generator module 120 to change the bias voltage V. BIAS A time delay ΔT can be applied before the value of the quantity.

[0099] Figure 4a This shows the circuit 200 responding to the decaying supply voltage V. S The timing diagram of the operation. For example... Figure 4a As shown, the supply voltage V S The value of decreases over time. As discussed above, control module 140 will supply voltage V S Alternatively, the voltage derived therefrom can be compared with a threshold voltage. Control module 140 may include a hysteresis comparator 300 to perform the comparison.

[0100] As shown in extension 202, in addition to including the DC voltage component, the supply voltage V S It may also include some AC noise components. (See reference...) Figure 1 As discussed, when drawing current I1 from the power supply, noise may be introduced into the DC supply voltage V due to parasitic elements in the power supply and / or caused by other electrical components and wiring. S In some implementations, the power supply and circuitry 200 may be part of the portable device, and the AC component may be generated by the “bumblebee effect” (also known as “TDM noise”) observed in some mobile communication devices.

[0101] refer to Figure 4a The control module 140 can be configured to supply voltage V S With the first buck voltage threshold V TH-1-SD A comparison is made. Therefore, the control module 140 can be configured to select a first buck voltage threshold V from the memory 150. TH-1-SD .

[0102] Control module 140 can be based on supply voltage V S The threshold voltage value is selected accordingly. Therefore, in one embodiment, the control module 140 can monitor the supply voltage V. S And determine the supply voltage V S Is the value decreasing or increasing in response to the supply voltage V? S Upon determining that the value of the bias voltage V is decreasing, control module 140 determines the bias voltage V. BIAS A buck transition may be required to prevent the bias generator module 120 from entering "dropout" operation. Therefore, the control module 140 can select a corresponding buck threshold to use as the reference voltage V. REF The hysteresis comparator 300 will (in the case of a reduced supply voltage V) S Compare with the reference voltage.

[0103] Similarly, in response to the determination that the magnitude of the supply voltage is increasing, the control module 140 determines the bias voltage V. BIAS A boost transition may be required. As will be described in more detail below, increasing the bias voltage can improve the sensitivity of the force sensor 130. Therefore, the control module 140 can select a corresponding boost threshold voltage value to use as the reference voltage V. REF The hysteresis comparator 300 will (increase) the supply voltage V S Compare with the reference voltage.

[0104] The control module 140 can also be based on the supply voltage V S The value of the quantity, such as the supply voltage V SThe threshold voltage value is selected based on the current or current magnitude. As discussed above, memory 150 can store multiple threshold voltage values. In one example, control module 140 can determine the bias voltage V. BIAS Possibly due to the supply voltage V S The voltage decreases and requires a step-down transition after a period of time. Therefore, the control module 140 can determine the supply voltage V. S The current value is determined, and an appropriate buck threshold voltage value is selected. Then, the control module 140 can compare this buck threshold voltage value with the supply voltage V. S Compare them.

[0105] Similarly, control module 140 can determine the bias voltage V. BIAS Possibly due to the supply voltage V S The voltage increases and requires a boost transition after a certain period of time. Therefore, the control module 140 can determine the supply voltage V. S The current value, and select the one closest to the supply voltage V. S The boost threshold voltage value is then determined. The control module 140 can then compare this boost threshold voltage value with the supply voltage V. S Compare them.

[0106] refer to Figure 4a At time T0, the supply voltage V S This is represented as attenuation. Therefore, the control module 140 can base its control on the attenuation of the supply voltage V. S The magnitude of the supply voltage at T0 is used to select the first buck threshold voltage value V. TH-1-SD From the supply voltage V S Compare them.

[0107] At time T1, control module 140 will supply voltage V. S With the first buck threshold voltage V TH-1-SD The comparison result can indicate the supply voltage V S The voltage has reached or has dropped to the first buck threshold voltage V. TH-1-SD Therefore, this can indicate the supply voltage V. S With bias voltage V BIAS The difference between them is approaching the voltage drop V of the bias generator module 120. DO Therefore, the control module 140 can output a control signal CTL to the bias generator module 120 to control the bias generator module 120 to generate a bias signal from a first predetermined value V. BIAS-1 Output V BIAS Transformed to the second limited value V BIAS-2 Output V BIAS The second limiting value V BIAS-2 Less than the first limit value VBIAS-1 And therefore the bias voltage V BIAS It can undergo a blood pressure reduction transition.

[0108] The control module 140 can be configured to apply a time delay ΔT before the output control signal CTL. Therefore, in some embodiments, when the supply voltage V... S It decays to the first buck threshold V at time T1. TH-1-SD In the following cases, the control module 140 may not supply voltage V. S Drop to the first drop threshold V TH-1-SD Instead of immediately outputting the control signal CTL, the control signal CTL can be output after a time delay ΔT. This time delay helps prevent V from being affected by factors such as noise. s Transient changes caused by V BIAS-1 To V BIAS-2 Frequent changes.

[0109] Therefore, the supply voltage V S With bias voltage V BIAS Between the second limiting value V BIAS-2 The difference at the point may be greater than the voltage drop V of the bias generator module 120. DO Therefore, as shown in the figure, if the supply voltage V S If the decay continues after time T1, the bias generator module 120 will not enter the "voltage drop" operation.

[0110] like Figure 4a As shown, the bias generator module 120 generates the bias voltage V BIAS Switch to the second smaller value V BIAS-2 This effectively shifts the voltage drop to a smaller value, corresponding to V. BIAS-1 With V BIAS-2 The difference in magnitude between them. With the pressure drop V DO The reduction in future supply voltage V S With threshold voltage V TH In the comparison, a lower threshold must be selected to reflect V. DO The decrease.

[0111] Therefore, at time T1, the control module 140 can select the second buck threshold voltage V. TH-2-SD In order to supply voltage V in the future S Compare. In response to the supply voltage V S The value drops to the first buck threshold voltage V TH-1-SD Therefore, the control module 140 can select the next minimum buck threshold voltage, i.e., the second buck threshold voltage V. TH-2-SD .

[0112] Figure 4a The bias generator is shown to generate a first bias voltage value V. BIAS-1 Switching to the second smaller bias voltage value V BIAS-2 However, as discussed above, the bias generator module 120 can be configured to output multiple different bias voltage values. It should be understood that reference... Figure 2 a and Figure 2 The transition method described in b can be applied to any reduction transition of the bias generator module 120 to transition from a first defined bias voltage value to a second defined bias voltage value that is less than the first defined bias voltage value. For example, the bias generator module 120 can output a bias voltage V BIAS From the second bias voltage value V BIAS-2 Switching to the third bias voltage value V BIAS-3 V BIAS-3 Less than V in magnitude BIAS-2 .

[0113] Therefore, the above regarding Figure 4a The discussion applies to bias generator 120, which is configured to output N bias voltage values ​​and is configured to output from a first voltage value V. BIAS-N-1 Transformation to a further smaller value V BIAS-N In some implementations, the magnitude differences between the N bias voltages can be equal. In other implementations, the magnitude differences between the N bias voltages can be unequal.

[0114] In an embodiment where the bias generator 120 is configured to output N bias voltage values, the control module 140 can therefore be configured to supply voltage V S The bias voltage is compared with N voltage threshold values. Therefore, each of the N bias voltages can be associated with a corresponding voltage threshold among the N voltage thresholds, such that when the bias generator module 120 outputs V... BIAS-N When the bias voltage is applied, the control module is configured to supply voltage V. S With corresponding to V BIAS-N Threshold voltage V TH-N Compare them.

[0115] It should be understood that when the supply voltage V S When the source originates from a decaying source, a limited amount of energy may be stored in the source. Therefore, after a certain decay time, there may be virtually no energy remaining in the source, and V S =0V. It should also be understood that the bias generator 120 therefore cannot switch to a lower bias voltage value indefinitely, and there will be a finite number of N bias voltage values ​​that the bias generator can output.

[0116] Figure 4b This shows that circuit 200 responds to the supply voltage V S Timing diagram of the operations performed during the increase. Supply voltage V S It can be obtained from sources that typically degrade (such as batteries). However, the supply voltage V is provided. S The power source can be connected to a charging source. Therefore, the supply voltage V S The value may increase.

[0117] At time T2, the bias generator module 120 can apply a second defined bias voltage value V. BIAS-2 Output bias voltage. Based on the supply voltage V. S The magnitude and the supply voltage V at time T2 S As the value increases, the control module can select the second boost threshold voltage V. TH-2-SU From the supply voltage V S Compare them.

[0118] As shown in the figure, the second boost threshold voltage value V TH-2-SU The magnitude can be greater than the second buck threshold voltage value V. TH-2-SD Two defined bias voltages V BIAS The difference in threshold voltage values ​​between the boost and buck transitions helps to mitigate the frequent switching of the bias generator module 120.

[0119] As mentioned above Figure 2 The discussion in a suggests that there may be a supply voltage V S The carried AC noise component. If the threshold voltage value is the same, the control module 140 can determine that the supply voltage has decayed to the voltage threshold V. TH-1 Below. In response to this comparison, the bias generator module can change the bias voltage from V... BIAS-1 Transition to V BIAS-2 However, due to the random nature of AC noise components, this component may cause the supply voltage V to... S The value repeatedly rises to the threshold voltage V TH-1 The voltage then drops back to the threshold voltage V after a short period of time. TH-1 The following. This behavior allows control module 140 to control bias generator module 120 to undergo V. BIAS-1 With V BIAS-2 The frequent switching between these values ​​is undesirable because it increases the strain on the bias generator module 120. Frequent switching may also introduce some noise into the bias voltage V. BIAS This may reduce the performance of the force sensor 130.

[0120] In another example, at the supply voltage V S Increase to above the threshold voltage (e.g., V)TH-1 Shortly after, the supply of V S The power supply can be disconnected from the charging source. In this type of example, when the supply voltage V... S Increase to threshold V TH-1 When the above occurs, the control module 140 can output a control signal CTL to control the bias generator module 120 to change the bias voltage from V... BIAS-2 Transition to V BIAS-1 .

[0121] However, if the power supply is at the supply voltage V S Increase to threshold V TH-1 If the power supply is disconnected shortly after the above time, the supply voltage V S It can begin to decay immediately, and it can also decay as it increases to the threshold V. TH-1 Shortly after, it drops to the threshold V. TH-1 The following. In this case, control module 140 can output control signal CTL shortly after undergoing the reverse transition to cause bias generator module 120 to switch from V... BIAS-1 Transition to V BIAS-2 This frequent shift may again be undesirable.

[0122] Furthermore, if the charging source is disconnected at or substantially at the threshold voltage, the control module 140 may not have sufficient time to respond to the decaying supply voltage V. S The output control signal CTL is then used. Therefore, before the control module 140 has time to output the appropriate control signal CTL, V... S With V BIAS The difference can be reduced to the point where the voltage generator module 120 enters the "voltage drop" operation.

[0123] Therefore, in some implementations, a voltage hysteresis H is applied. V To prevent such frequent switching behavior, memory 150 can store a threshold voltage larger than the corresponding decreasing transition between two bias voltages for an increasing transition. Therefore, control module 140 can adjust the supply voltage V. S With the second buck voltage threshold V TH-2-SD Compare, in V BIAS-1 With V BIAS-2 The transition between them is reduced, and the supply voltage V is reduced. S With voltages above the second buck threshold V TH-2-SD The second boost voltage threshold V TH-2-SU Compare, in V BIAS-1 With V BIAS-2 The transitions between them are increased.

[0124] Although separate buck and boost threshold voltage values ​​have been described above, in another embodiment, separate boost and buck voltage thresholds may not be provided. Instead, the hysteresis comparator can be designed so that the boost transition provides a larger voltage threshold than the corresponding buck transition.

[0125] Refer again Figure 4b At time T3, the supply voltage V S It can be increased to the second buck threshold voltage value V TH-2-SD That's all. However, as discussed above, this will not cause the bias voltage V to... BIAS The process involves increasing the switching voltage to avoid frequent bias voltage V. BIAS change.

[0126] At time T4, the supply voltage V S It can be increased to the second boost voltage threshold V TH-2-SU The above. In response to this comparison, control module 140 may output a control signal CTL to bias generator module 120 to adjust the bias voltage from the second defined bias voltage value V. BIAS-2 Switching to the first bias voltage value V BIAS-1 As shown in the figure.

[0127] The first defined bias voltage value V BIAS-1 It can be the maximum magnitude bias voltage V that can be output by the bias generator module 120. BIAS Therefore, besides V BIAS-1 Besides, there may be no bias generator module that can switch to a boost transition. Therefore, with the bias voltage V BIAS The output is at the maximum possible value, and as the value of the supply voltage increases, the control module 140 can avoid matching the supply voltage with any threshold voltage V. TH Compare them.

[0128] Figure 4c This shows that circuit 200 responds to the supply voltage V S Another timing diagram of the operation performed during the increase. At time T2, the bias generator module 120 can apply a second defined bias voltage value V. BIAS-2 Output bias voltage V BIAS For example, regarding Figure 4b As described, due to the supply of voltage V at time T0 S As the magnitude and value increase, the control module 140 can therefore select the second boost threshold voltage value V. TH-2-SU From the supply voltage V S Compare them.

[0129] At time T3, the supply voltage V SIt can be increased to the second boost threshold voltage value V TH-2-SU That's all. However, as shown in the figure, the bias voltage V BIAS The comparison result at time T3 does not immediately undergo a magnitude increase. Instead, it occurs at... Figure 4c In the middle, when the time delay ΔT expires at time T4, the bias voltage V BIAS From the second defined bias voltage value V BIAS-2 Switching to the first defined bias voltage value V BIAS-1 .

[0130] Therefore, the control module 140 can be configured to respond to determining the supply voltage V S The voltage has been increased above the threshold voltage, and a time delay ΔT is applied. When the time delay ΔT expires, the control module 140 can output a control signal CTL to the bias generator module 120 to control the bias generator module 120 to apply a bias voltage of the second defined magnitude V. BIAS-2 Output bias voltage V BIAS Transition to a bias voltage value greater than the second limit V BIAS-2 The first defined bias voltage value V BIAS-1 .

[0131] Applying a time delay ΔT before the output control signal CTL by control module 140 helps prevent bias generator module 120 from undergoing frequent transitions. The time delay ΔT can be selected to allow sufficient time for the bias voltage V to be applied. BIAS Before making changes, stabilize or eliminate transient effects (such as voltage spikes) caused by noise.

[0132] As described, the supply voltage V S It may include an AC noise component, which can cause the supply voltage V to... S Increase to above the threshold voltage, for example, V TH-2-SU However, the control module 140 has already determined the supply voltage V. S Shortly after increasing above the threshold voltage, the AC component can cause the supply voltage V to... S It drops below the threshold voltage. Without applying a time delay ΔT, whenever the supply voltage V... S The bias voltage may change above and below the threshold voltage. When the supply voltage V... S When AC noise components are included, this will cause the bias voltage V to decrease due to transient noise effects. BIAS Frequent changes, as discussed above, are undesirable.

[0133] Therefore, the application of a time delay ΔT allows sufficient time for transient effects to dissipate before the bias voltage undergoes a boost transition.

[0134] The time delay ΔT can be appropriately selected for a given system. The time delay can be predetermined and stored in memory 150. The time delay ΔT can be based on, for example, the supply voltage V of the given system. S The expected growth rate is determined in advance.

[0135] In one implementation, the control module 140 can monitor the supply voltage during a time delay ΔT. During the time delay ΔT, the control module 140 can determine the supply voltage V. S The overall trend has begun to decline and is no longer increasing in magnitude. For example, the power supply providing the supply voltage may be disconnected from the charging source, and therefore the supply voltage will begin to decline. Therefore, the control module 140 can pause or stop the time delay ΔT without outputting the control signal CTL. If the supply voltage V S It then decays below the threshold voltage, for example, V. TH-2-SU Then the control module 140 can determine the bias voltage V. BIAS The voltage should be maintained at a low value (e.g., V). BIAS-2 This also eliminates the need to output the control signal CTL. This operation further mitigates the effects of frequent switching transitions experienced by the bias generator 120.

[0136] As described above, during the time delay ΔT, the supply voltage V S The state can be switched to indicate the supply voltage V S The value of is decreasing. However, the supply voltage V S The state can be switched again during the time delay ΔT to indicate the supply voltage V. S Drop to threshold voltage (e.g., V) TH-2-SU Before that, the supply voltage V S The value is increasing. For example, the supply voltage V is being provided. S The power source can be temporarily disconnected from the charging source before being reconnected after a relatively short period of time.

[0137] Therefore, the control module 140 can respond to the supply voltage V S The second change in state is followed by a reapplication of the time delay ΔT. In response to the expiration of the reapplication of the time delay ΔT, the control module 140 can also output a control signal CTL. The reapplication of the time delay ΔT allows sufficient time again to output the control signal CTL to control the bias voltage V. BIAS Before undergoing an increased transition, the transient effects subside or stabilize.

[0138] In one embodiment, memory 150 may store a second time delay ΔT2 (not shown) in response to the supply voltage V. SThe change in direction (increase / decrease) is applied by switching. In one implementation, the second time delay ΔT2 can be shorter than the time delay ΔT.

[0139] Those skilled in the art will understand that, regarding Figure 4b and Figure 4c The disclosures can be combined. For the same two bias voltage values, the boost transition between the two defined bias voltage values ​​can be based on a boost threshold voltage value that is greater than the buck threshold voltage value. The control module 140 can also be configured to output a control signal CTL in response to the supply voltage value remaining greater than the larger boost threshold voltage value when the time delay expires.

[0140] Figure 5 This illustrates the bias generator module 120 and the control module 140 in response to the supply voltage V. S A graph showing the operations performed in response to changes. Figure 5 The supply voltage V is shown. S Changes over time. For example, regarding... Figures 4a to 4c The voltage V described S It can be obtained from a source such as a battery and can be used to supply voltage V to the bias generator module 120. S Supply voltage V S It can also be used to power other components of the host electronic device. Therefore, in some embodiments, at T0, the supply voltage V is [value missing] because current is drawn from the power source to power the bias generator module 120 and other components. S It may begin to decay over time.

[0141] The bias generator 120 can be configured to output multiple different bias voltage values. Figure 5 In the illustrated embodiment, the bias generator module 120 can be configured to output three defined bias voltage values ​​V. BIAS-1 V BIAS-2 and V BIAS-3 As shown in the figure, the bias voltage value ranges from V BIAS-1 Reduce to V BIAS-3 However, those skilled in the art will understand that applications regarding Figure 5 The disclosure allows the bias generator module 120 to output any number of defined bias voltage values.

[0142] At T0, the bias generator 120 can be configured to output a first value V. BIAS-1 The bias voltage. V BIAS-1 This can correspond to the maximum bias voltage value output by the bias generator module 120.

[0143] Between T0 and T1, the control module 140 can supply voltage VS A comparison is made with the buck threshold voltage to prevent the bias generator module from entering "dropout" operation. Therefore, during the time period T0-T1, the bias voltage V... BIAS Configured as the first value V BIAS-1 In this case, the control module 140 can supply voltage V S With the first buck threshold voltage V TH-1-SD Compare them.

[0144] At point T1, control module 140 can determine the supply voltage V. S The value has dropped to the first buck threshold voltage V. TH-1-SD The following is for reference. Figure 4a Therefore, the control module 140 can output a control signal CTL to control the bias generator module 120 to apply the bias voltage V. BIAS From the first value V BIAS-1 Transform into the second smaller value V BIAS-2 Therefore, as described above, the supply voltage V S It can continue to decay, while the bias generator module 120 does not enter the "voltage drop" operation.

[0145] At point T1, with the supply voltage V S At the first buck threshold voltage value V TH-1-SD If the voltage value is below the threshold and continues to decrease, the control module 140 can select a second buck voltage threshold V. TH-2-SD As the voltage threshold V TH .

[0146] like Figure 5 As shown, during the time period T1 to T2, the supply voltage V S The decay continues. At time T2, control module 140 determines the supply voltage V. S The second step-down voltage threshold V has been reached. TH-2-SD At time T2, control module 140 can therefore again output control signal CTL to bias generator module 120 to control bias generator module 120 to bias voltage V. BIAS From the second bias voltage value V BIAS-2 Switching to the third bias voltage value V BIAS-3 As shown in the figure, the third bias voltage value V BIAS-3 Having a value V greater than the second bias voltage BIAS-2 A smaller value. The bias generator module 120 can be made to operate from V as described above. BIAS-1 Transition to V BIAS-2 This operation of the bias generator module 120 is performed in a manner that allows it to function.

[0147] As shown in the figure, the bias voltage V is between time periods T2 and T3. BIAS In V BIAS-3 Output, supply voltage V S The bias continues to decay, and the bias generator does not enter the "voltage drop" operation. During this period, the control module 140 can also be configured to supply voltage V S With the third buck voltage threshold V TH-3-SD (Not shown) Comparison. Third buck voltage threshold V TH-3-SD It can be set to be higher than the second buck voltage threshold V TH-2-SD Small values. If the supply voltage V S Drop to the third buck voltage threshold V TH-3-SD Next, the control module will output a control signal CTL to the bias generator module 120 to change the bias voltage from the third bias voltage value V. BIAS-3 Switching to the fourth bias voltage value V BIAS-4 (Not shown). V BIAS-4 It can have a value V greater than the third bias voltage. BIAS-3 Smaller values.

[0148] At time T3, the supply voltage V S The decay stops and the magnitude begins to increase. For example, this change could correspond to a battery connected to an external power source and being charged. In another example, the current drawn from the host device's battery may decrease because other components of the host device (e.g., the host device's display or screen) are powered off, causing the parasitic resistance R to decrease. 110 The impact is reduced.

[0149] As described above, the control module 140 can be configured to adjust based on the changing supply voltage value V. S To select the threshold voltage value V TH At time T3, the control module can determine that the magnitude of the supply voltage has changed from decreasing to increasing. Therefore, at time T3, the control module 140 can select the second boost threshold voltage value V. TH-2-SU Once the supply voltage increases to the second boost threshold voltage value V... TH-2-SU As stated above, at time T4, the bias voltage undergoes a change from V BIAS-3 To V BIAS-2 The transformation.

[0150] At time T5, the control module 140 can also base its response on the supply voltage V. S Increase to the second boost voltage threshold V TH-2-SU The above and the supply voltage V S The value continues to increase to select the first boost voltage threshold V. TH-1-SU In order to supply voltage V in the future SCompare them.

[0151] Refer again Figure 5 Between time periods T3 and T6, the supply voltage V S The value is increasing. At time T5, the supply voltage V... S The value may stop increasing and begin to decay. For example, the supply voltage V S The battery can be disconnected from the charging source at time T5. Therefore, at time T5, the control module 140 can adjust the voltage threshold V based on the decreasing supply voltage. TH .

[0152] Based on the supply voltage V at time T5 S In reducing and supplying voltage V S The control module 140 can select a second buck threshold V based on the magnitude of the voltage. TH-2-SD From the supply voltage V S Compare them.

[0153] Between time T5 and T6, the supply voltage V S Attenuation, and the control module 140 will supply voltage V S With the second drop threshold V TH-2-SD A comparison is made. At time T6, control module 140 can determine the supply voltage V. S The second blood pressure reduction threshold V has been reached. TH-2-SD Therefore, the control module 140 outputs a control signal CTL to cause the bias generator module 120 to change the bias voltage from V... BIAS-2 Transition to V BIAS-3 This operation can be roughly equated to the operation described at time T2 discussed above.

[0154] Between time T6 and T7, control module 140 will supply voltage V. S With the third buck voltage threshold V TH-3-SD (Not shown) For comparison, the magnitude of the third buck voltage threshold can be less than the second buck voltage threshold V. TH-2-SD The magnitude is similar to the description above between time T2 and T3.

[0155] At time T7, the supply voltage V S The magnitude of the voltage stops decreasing and instead begins to increase. Therefore, the control module 140 adjusts the voltage based on the supply voltage V. S The value is increased to adjust the voltage threshold.

[0156] For reference Figure 4c As described, the control module 140 can be configured to apply a time delay ΔT before the output control signal CTL to adjust the bias voltage V. BIASThe transformation becomes an experience of increased transformation (i.e., applying a time lag H to the transformation). T In such implementations, the control module 140 can select the same threshold voltage value for both the increase and decrease transitions between two bias voltage thresholds, or alternatively, it can do so by supplying the increase and decrease voltage V. S Different threshold voltage values ​​are selected to continue applying voltage hysteresis H. V .

[0157] For example, control module 140 can be configured to supply voltage V S With the second buck voltage threshold V TH-2-SD Compare to change the bias voltage from V BIAS-2 Transition to V BIAS-3 And vice versa. However, for example, from V BIAS-3 To V BIAS-2 The control module 140 can be configured to determine the change in the supply voltage V based on the magnitude of the change. S A time delay ΔT is applied between when the voltage has risen above the threshold voltage and the output control signal CTL. As described above, this operation reduces the frequent switching of the bias generator module 120. Storing only one threshold for decreasing and increasing the bias voltage reduces the amount of memory required to store the threshold voltage value in memory 150.

[0158] Therefore, in the following description, the second buck threshold voltage value V TH-2-SD The controlled module 140 is used for bias voltage V BIAS The single threshold voltage for both increasing and decreasing the transition.

[0159] Therefore, at time T7, the control module can select the second buck voltage threshold V. TH-2-SD From the supply voltage V S A comparison is made. At time T8, control module 140 can determine the supply voltage V. S The voltage has reached or risen to the second buck threshold V. TH-2-SD That's all. However, as shown in the figure, at time T8, the bias voltage V... BIAS Maintain the third bias voltage value V BIAS-3 As discussed above, the control module 140 can apply a time delay ΔT before outputting the control signal CTL to the bias generator module 120.

[0160] At time T9, the time delay ΔT expires, and therefore the control module 140 can output a control signal CTL to the bias generator module 120 to adjust the bias voltage V. BIAS From the third bias voltage value V BIAS-3 Switch to the second bias voltage value VBIAS-2 .

[0161] exist Figure 5 In the illustrated implementation, the time delay ΔT can be configured such that when the time delay ΔT expires, the supply voltage V... S At time T9, it has a voltage that is substantially equal to the second boost threshold voltage V. TH-2-SU The magnitude of the value. However, in other implementations, the time delay ΔT can be configured such that the bias voltage V BIAS Before undergoing the increase transition, the supply voltage V S It can include any appropriate value above the threshold voltage.

[0162] therefore, Figure 5 The control module 140 and bias generator module 120 are shown in response to the supply voltage V. S The operation changes. As described, the control module 140 can respond to changes in the supply voltage V. S The operation of the bias generator module 120 is controlled by the change in bias voltage to output the bias voltage value V. BIAS-1 V BIAS-2 and V BIAS-3 As discussed above, the sensitivity of the force sensor 130 may be affected by the amount of bias voltage.

[0163] The bias generator module 120 uses a first defined bias voltage value V BIAS-1 Output bias voltage, which corresponds to the maximum configurable value of the bias generator module 120. At the first bias voltage value V... BIAS-1 Therefore, the sensitivity of the force sensor 130 can be at its maximum operating condition.

[0164] As described above, the sensitivity of the force sensor is related to the bias voltage V. BIAS Related (e.g., proportional). Therefore, with the bias voltage set to the maximum available value, the sensitivity of the force sensor 130 may not decrease, and the output signal V from the force sensor 130... OUT It can be provided to downstream processing circuits / modules.

[0165] Refer again Figure 2 In some implementations, the output signal V OUT Therefore, it can be provided to the processing circuit / module (PM)160.

[0166] As discussed above, the supply voltage V S The voltage may be attenuated due to current drawn from the power source. Supply voltage V S It may decay to the first buck voltage threshold V. TH-1-SD When the control module 140 detects that the supply voltage Vs has dropped to the first buck voltage threshold V...TH-1-SD At that time, the control module 140 outputs a control signal CTL to the bias generator module 120 to adjust the bias voltage V. BIAS From the first bias voltage value V BIAS-1 Switching to the second bias voltage value V BIAS-2 .

[0167] Due to the second bias voltage value V BIAS-2 Below the first bias voltage V BIAS-1 The magnitude of the bias voltage, therefore, a reduced bias voltage value may affect the sensitivity of the force sensor 130. For example, a reduced bias voltage V BIAS This could mean that users would have to apply increased force to the force sensor 130 to detect user interaction. Without additional processing steps to mitigate this effect, this could lead to a degraded user experience.

[0168] Therefore, in one embodiment, the control module 140 can be configured to receive the bias voltage V. BIAS and / or indicating bias voltage V BIAS The voltage. The control module 140 can also be configured to apply a normalization function NORM to the output signal V of the force sensor 130. OUT The normalized output signal V OUT The normalization function NORM can be based on the bias voltage V. BIAS The value of.

[0169] The normalization function NORM can be configured to be used in V BIAS With V BIAS-1 The following quantities (e.g., V) BIAS-2 When outputting, the output signal is normalized. The normalization function can therefore normalize the output signal V. OUT This makes the bias voltage V BIAS V at a lower value OUT The characteristics basically correspond to V BIAS Set to the maximum value (i.e., V) BIAS-1 The output signal V OUT Characteristics. Therefore, the application of the normalization function can offset the effect caused by the bias voltage V. BIAS The decrease in the magnitude of the force sensor 130 leads to a decrease in sensitivity.

[0170] Refer again Figure 2 The normalization function NORM can be applied to the output signal V by the processing circuit / module 160. OUT The processing circuit / module 160 can receive the normalization function NORM from the control module 140 and the output signal V from the force sensor 130. OUTThe processing circuit / module 160 can then apply the normalization function NORM to the output signal V. OUT To output a normalized output signal V OUT-NORM Normalized output signal V OUT-NORM The output can be from processing circuit / module 160 to other processing circuits / modules (not shown), which can be based on the normalized output signal V. OUT-NORM Detected user interactions enable certain features.

[0171] In some implementations, memory 150 may include multiple normalization functions corresponding to multiple defined bias voltage values. Therefore, control module 140 may be configured to receive bias voltage V. BIAS and / or indicating bias voltage V BIAS The voltage is determined, and a corresponding normalization function is selected from a plurality of normalization functions based on the bias voltage value. Control module 140 can be configured to supply the corresponding normalization function NORM to processing circuit / module 160, which can be configured to apply the normalization function NORM to the output signal V. OUT .

[0172] As discussed, the sensitivity of the force sensor 130 may not decrease when the bias voltage is configured to the maximum configurable limit value of the bias generator module 120. Therefore, in one embodiment, the normalization function corresponding to the maximum bias voltage value may correspond to essentially no normalization.

[0173] Therefore, for a given application of circuit 200, multiple normalization functions can be pre-programmed. These normalization functions can be calculated in software to compensate for the bias voltage V. BIAS The decrease in the magnitude of the force sensor 130 leads to a decrease in sensitivity.

[0174] In some implementations, if the normalization function NORM can be applied to the reduced bias voltage value V BIAS Appropriately normalize the corresponding output signal V OUT Then the bias voltage V BIAS The magnitude of the decrease in VBIAS may be limited. As VBIAS decreases, the magnitude of the output VOUT of the force sensor 130 also decreases, and therefore the signal-to-noise ratio (SNR) of VOUT will also decrease. The SNR may decrease to a level where normalization cannot compensate for the decrease in SNR. This may lead to adverse effects, such as erroneous detection in user interactions.

[0175] Therefore, in some implementations, in response to the supply voltage V S Reduce to the minimum voltage threshold V TH-NThe processing circuit / module 160 can be configured to ignore or disregard the output signal V. OUT When the supply voltage V S When the value of the bias voltage V decays to below the nth voltage threshold of the N values, the bias voltage V BIAS It can be configured as the nth bias voltage value V among N bias voltage values. BIAS-N V BIAS-N The bias force sensor 130 can provide an output signal V OUT Even after the normalization operation, the resulting normalized output signal V OUT-NORM It may also include significant noise components.

[0176] Therefore, if such a "noisy" normalized output signal V is provided to downstream processing circuits / modules... OUT-NORM This could lead to a degraded user experience, such as false positives in user activity detection. Therefore, when the control module 140 determines the supply voltage V... S The value has decreased to the nth voltage threshold V. TH-N In the following cases, the control module 140 can control the processing module 160 to ignore or disregard the output signal V. OUT Therefore, when the supply voltage V S It has decayed to the nth voltage threshold V TH-N In the following cases, the processing module 160 may not output signal V. OUT Apply the normalization function.

[0177] When the supply voltage V S It has decayed to the nth voltage threshold V TH-N It should be understood that various other circuits / modules powered by the supplied voltage may also not operate. In one embodiment, circuit 200 may be integrated into the electronic device and supplied with voltage V. S It can also power other components of electronic devices, such as touchscreens, speakers, microphones, etc. As the supply voltage decays to the nth voltage threshold V... TH-N The following is the supply voltage V S It may not supply enough power to reliably power any component of an electronic device. Therefore, a power source that provides the supply voltage can be considered "flat" and may not be able to power any component of an electronic device.

[0178] The foregoing description has presented the disclosed aspects in the context of force sensors. However, for example, the above disclosure is also applicable to any other type of sensor biased by a bias voltage obtained from a finite voltage source, such as a battery, a MEMS transducer, or a strain gauge. However, those skilled in the art will understand that this disclosure can be applied to any other suitable sensor.

[0179] Embodiments of the present invention can be implemented in electronic devices, particularly in portable and / or battery-powered devices. Figure 6 An electronic device 600 is shown, comprising a power supply 610, a bias generator module 620, one or more force sensors 630, and a control module 640. The control module 640 and the bias generator module 620 can operate as described above to bias the one or more force sensors 630. The one or more force sensors 630 can provide a user interface. The electronic device 600 can be a portable or battery-powered device, such as a tablet or laptop computer, or a smartphone or smartwatch, or a communication interface device, such as a smart speaker or other smart listening device. Therefore, the power supply 610 may include a battery. The device may be a household appliance. The device may include an application processor (AP) 650, and in some embodiments, the AP 650 may be operable to configure functions from the electronic device 600 in response to user interactions detected from the one or more force sensors 630. The device 600 may have at least one other user interface 660, for example for displaying output to a user, and in some applications, the application processor 650 may be operable to display output via UI 660 in response to detected user interaction from one or more force sensors 630.

[0180] Those skilled in the art will recognize that some aspects of the above-described devices and methods (e.g., discovery and configuration methods) can be implemented as processor control code, for example, on non-volatile media (such as disks, CDs, or DVD-ROMs), programmable memories (such as read-only memories (hardware)), and data carriers (such as optical or electrical signal carriers). For many applications, implementations will be on DSPs (Digital Signal Processors), ASICs (Application-Specific Integrated Circuits), or FPGAs (Field-Programmable Gate Arrays). Therefore, the code can include conventional program code or microcode, or, for example, code for setting up or controlling an ASIC or FPGA. The code can also include code for dynamically configuring reconfigurable devices (such as reprogrammable gate arrays). Similarly, the code can include code for hardware description languages ​​(such as Verilog). TM Alternatively, the code may be in VHDL (Very High Speed ​​Integrated Circuit Hardware Description Language). As those skilled in the art will understand, the code can be distributed among multiple coupled components that communicate with each other. Where appropriate, the aforementioned implementation scheme may also be implemented using code that runs on a field-programmable (reprogrammable) analog array or similar device to configure the analog hardware.

[0181] It should be noted that the above embodiments are illustrative and not limiting of the invention, and those skilled in the art will be able to devise many alternative embodiments without departing from the scope of the appended claims. The word "comprising" does not exclude the presence of elements or steps other than those listed in the claims, and "a" or "an" does not exclude a plurality, and a single feature or other unit may satisfy the characteristics of several units listed in the claims. No reference numerals or labels in the claims should be construed as limiting their scope. Terms such as amplification or gain include the possibility of applying a scaling factor less than 1 to the signal.

Claims

1. A circuit for biasing a sensor, comprising: A bias generator module is configured to receive a supply voltage and generate an regulated bias voltage for biasing the sensor. as well as A control module is configured to compare a voltage indicating the supply voltage with a threshold voltage and to output a control signal to the bias generator module based on the comparison. The bias generator module is configured to control the bias voltage based on the control signal.

2. The circuit of claim 1, wherein the bias generator module is operable to adjust the bias voltage from a first defined bias voltage value to a second defined bias voltage value based on the control signal.

3. The circuit of claim 2, wherein the second defined bias voltage value is less than the first defined bias voltage value, and the control module is configured to output the control signal in response to the comparison indicating that the value of the supply voltage has decreased below the threshold voltage.

4. The circuit of claim 2, wherein the second defined bias voltage value is greater than the first defined bias voltage value, and the control module is configured to output the control signal in response to the comparison indicating that the value of the supply voltage has increased above the threshold voltage.

5. The circuit of claim 4, wherein the control module is configured to apply a time delay before outputting the control signal.

6. The circuit of claim 5, wherein the time delay is predetermined based on the expected growth rate of the supply voltage value.

7. The circuit of claim 1, wherein the control module is configured to monitor the supply voltage to determine whether the supply voltage value is increasing or decreasing.

8. The circuit of claim 7, wherein the control module is configured to pause the output of the control signal in response to the control module determining that the supply voltage value is decreasing during a time delay.

9. The circuit of claim 8, wherein the control module is configured to not output the control signal in response to the control module determining that the supply voltage has decreased below the threshold voltage during the time delay.

10. The circuit of claim 7, wherein the control module is configured to select the value of the threshold voltage based on the determination that the supply voltage value is increasing or decreasing.

11. The circuit of claim 10, wherein in response to the control module determining that the supply voltage is decreasing, the control module is operable to select a first threshold voltage value.

12. The circuit of claim 11, wherein in response to the control module determining that the supply voltage value is increasing, the control module is operable to select a second threshold voltage value, wherein the second threshold voltage value is greater than the first threshold voltage value.

13. The circuit of claim 11, wherein in response to the control module determining that the supply voltage value is increasing, the control module is operable to select the first threshold voltage value.

14. The circuit of claim 1, wherein the control module is configured to select the value of the threshold voltage based on the magnitude of the supply voltage.

15. The circuit of claim 1, wherein the bias generator module is configured to generate the bias voltage with a plurality of defined bias voltage magnitude values.

16. The circuit of claim 15, further comprising a memory for storing a plurality of threshold voltage values ​​corresponding to the plurality of defined bias voltage magnitudes, and the control module being configured to select one of the plurality of threshold voltage values ​​to compare with the supply voltage based on the magnitude of the supply voltage and a determination that the magnitude of the supply voltage is increasing or decreasing.

17. The circuit of claim 16, wherein the plurality of threshold voltage values ​​are predetermined based on the voltage drop of the bias generator module.

18. The circuit of claim 17, wherein the control module is configured to receive a signal indicating the bias voltage.

19. The circuit of claim 18, wherein the control module is configured to select a normalization function based on the bias voltage. The circuit further includes a processing module configured to receive an output signal from the sensor and also configured to receive the normalization function from the control module; and The processing module is configured to apply the normalization function to the output signal to generate a normalized output signal.

20. The circuit of claim 19, wherein the circuit includes a memory, the memory including a plurality of normalization functions corresponding to the plurality of defined bias voltage values; and wherein the control module is configured to select one of the plurality of normalization functions based on the bias voltage values.

21. The circuit of claim 19, wherein the threshold voltage includes the minimum of the plurality of threshold voltage values; and wherein, in response to the comparison indicating that the supply voltage has decayed below the minimum of the plurality of threshold voltage values, the control module is configured to control the processing module to not process the output signal.

22. The circuit of claim 1, wherein the control module includes a hysteresis comparator configured to compare the supply voltage with the threshold voltage and output the control signal based on the comparison.

23. The circuit of claim 22, wherein the control signal includes a latch signal.

24. The circuit according to claim 1, wherein the sensor is a force sensor.

25. The circuit according to claim 1, which is implemented as an integrated circuit.

26. A power supply unit comprising: The circuit according to claim 1; as well as A battery configured to output the supply voltage.

27. An electronic device comprising: The circuit according to claim 1; A battery configured to output the supply voltage; as well as A sensor configured to receive the bias voltage.

28. The electronic device of claim 27, wherein the electronic device includes a portable or battery-powered device.

29. The electronic device of claim 27, wherein the electronic device is one of the following: a tablet computer, a laptop computer, a smartphone, or a smartwatch.

30. A circuit for normalizing the output signal of a force sensor, comprising: A bias generator module is configured to receive a supply voltage and generate a bias voltage for biasing the force sensor. A control module is configured to receive a voltage indicating the bias voltage and select a normalization function based on the bias voltage; as well as A processing module is configured to receive the output signal and the normalization function; The processing module is further configured to apply the normalization function to the output signal to normalize the output signal.

31. A sensor module comprising: sensor; A bias generator is configured to receive a supply voltage and generate an regulated bias voltage for biasing the sensor. as well as A controller is configured to compare a signal voltage indicating the supply voltage with a threshold voltage, and to output a control signal to the bias generator based on the comparison; The bias generator is configured to control the bias voltage based on the control signal.

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