Mismatches in voltage compensation

Abstract

A sensor offset voltage compensation circuit includes a programmable gain amplifier (PGA) having an input loop configured to receive a signal output by a sensor (e.g., a voltage generated by a sensor resistance bridge of a pressure sensor) and an output loop configured to provide an output signal having a voltage greater than the input voltage. An offset compensation voltage is applied to at least one of the input loop or the output loop of the PGA to at least substantially eliminate the zero quantity offset voltage of the sensor from the output voltage.

Description

Background Technology

[0001] A common type of pressure sensor employs a bonded or molded strain gauge formed in a substrate to detect strain generated in the substrate material due to applied pressure. In this type of sensor, the strain gauge utilizes the piezoresistive effect, where the resistance of the strain gauge increases as the pressure deforms the material of the strain gauge. Typically, the strain gauges of these pressure sensors are arranged in a Wheatstone bridge configuration (e.g., a Wheatstone bridge configuration) to maximize the sensor's output and reduce its sensitivity to errors. Attached Figure Description

[0002] Specific embodiments are described with reference to the accompanying drawings. The same reference numerals are used in different contexts in the specification and drawings to indicate similar or identical items. Various embodiments or examples (“Examples”) of this disclosure are disclosed in the following detailed description and the accompanying drawings. The drawings are not necessarily drawn to scale. Generally, unless otherwise provided in the claims, the disclosed processes can be performed in any order.

[0003] Figure 1 This is a circuit diagram illustrating a sensor offset voltage compensation circuit implemented using a programmable gain amplifier (PGA) according to an example embodiment of this disclosure.

[0004] Figure 2A This is a circuit diagram showing a sensor offset voltage compensation circuit implemented using a PGA according to this disclosure, wherein an offset compensation voltage is applied to the input loop of the PGA.

[0005] Figure 2B This illustrates example embodiments based on this disclosure. Figure 2A The circuit diagram of the V / I circuit block of the PGA is shown.

[0006] Figure 2C This illustrates example embodiments based on this disclosure. Figure 2B The circuit diagram of the current fine-tuning circuit of the V / I circuit block is shown.

[0007] Figure 3A This is a circuit diagram showing a sensor offset voltage compensation circuit implemented using a PGA according to this disclosure, wherein an offset compensation voltage is applied to the output circuit of the PGA.

[0008] Figure 3B This is a circuit diagram illustrating a programmable current source according to an example embodiment of this disclosure, the programmable current source being used to generate offset current to provide Figure 3A The offset compensation voltage of the PGA is shown.

[0009] Figure 3CThis is a circuit diagram illustrating a sensor offset voltage compensation circuit implemented using a PGA according to this disclosure, wherein an offset compensation voltage is applied to the output loop of the PGA, and wherein a second PGA is used to adjust the impedance of the circuit.

[0010] Figure 4 This is a circuit diagram illustrating a pressure sensor including a sensor resistor bridge according to an example embodiment of this disclosure. Detailed Implementation

[0011] Overview Sensors used to measure quantities such as pressure, strain, displacement, deformation, and temperature often have zero-quantity (or zero-component) offsets in their outputs due to structural imperfections (which can cause the sensor to have an output even when no quantity is sensed (e.g., the sensed quantity is equal to zero (0))). For example, a pressure sensor that uses a sensor resistive bridge to measure pressure may have a zero-pressure offset voltage in its output due to factors such as mismatch in the resistive elements (e.g., resistors, strain gauges, etc.) that make up the bridge. Such a sensor can, for example, provide a full-scale output voltage in the range of 1 to 5 mV / V with a built-in zero-pressure offset voltage of up to 100 mV / V. Therefore, pressure signals cannot be measured accurately because the offset voltage dominates the sensor's output signal. Therefore, some type of signal conditioning can be used to compensate for this offset voltage. Previous sensor assemblies have addressed offset voltage compensation by inserting voltage compensation in the analog front end of the pressure sensor's signal processor, which requires calculation based on the bridge voltage and analog path gain. Compensation is then activated by selecting the corresponding EEPROM bit loaded when the device is powered on. This disclosure provides zero-pressure offset voltage compensation that does not require calculation.

[0012] Therefore, an offset voltage compensation circuit is disclosed for eliminating zero offset voltage from a signal generated by a device such as a sensor (e.g., a sensor resistor bridge of a pressure sensor). According to this disclosure, the signal generated by the sensor includes a voltage (hereinafter referred to as the “input voltage”) comprising a first component voltage proportional to a physical quantity (e.g., pressure) sensed by the sensor and a second component voltage equal to the zero offset voltage, which corresponds to the voltage generated by the sensor when the sensor does not sense a physical quantity (e.g., when the pressure sensed by the pressure resistor bridge is zero (0)).

[0013] The offset voltage compensation circuit includes a programmable gain amplifier (PGA) having an input loop configured to receive a signal output by a sensor (e.g., a voltage generated by a sensor resistor bridge of a pressure sensor) and an output loop configured to provide an output signal with a voltage greater than the input voltage. An offset compensation voltage is applied to at least one loop of the PGA's input or output loop to at least substantially eliminate the zero-quantity offset voltage from the output voltage supplied to the ADC. The offset compensation voltage is proportional to the bias voltage applied to the sensor to sense the physical quantity. For example, in embodiments where the sensor includes a pressure resistor bridge, the offset compensation voltage is proportional to the bridge voltage applied to the sensor resistor bridge.

[0014] In one embodiment, the PGA includes a first amplifier having a first input, a first inverting input, and a first output, and a second amplifier having a second input, a second inverting input, and a second output. The first and second inputs form an input loop and are configured to receive an input voltage from a sensor, wherein the input voltage includes a sensor output voltage proportional to a physical quantity sensed by the sensor and a zero-quantity offset voltage corresponding to the voltage output by the sensor when the sensor does not sense the physical quantity. The first and second outputs form an output loop and are configured to provide an output voltage to an analog-to-digital converter (ADC), which converts the output voltage into a digital signal, which is then provided to a digital signal processor or the like for processing. An offset compensation voltage is applied to the first and second inverting inputs using a resistor to at least substantially eliminate the zero-quantity offset voltage from the output voltage. In one embodiment, the offset compensation voltage is proportional to a bias voltage applied to the sensor to sense the physical quantity and includes an offset current generated from the bias voltage applied across the resistor.

[0015] Example Implementation refer to Figure 1 This document describes an offset voltage compensation circuit 100 according to an example embodiment of the present disclosure. As shown, the offset voltage compensation circuit 100 includes a programmable gain amplifier (PGA) 102, which includes an input loop 104 and an output loop 106. As shown, the input loop 104 is configured to receive signals output by devices such as a sensor resistor bridge 128 of a sensor 130.

[0016] In an embodiment, PGA 102 includes one or more amplifiers. For example, as shown, PGA 102 may include at least a first operational amplifier (OA1) 108 and a second operational amplifier (OA2) 110. The first operational amplifier 108 includes a first non-inverting input 112, a first inverting input 114, and a first output 116. Similarly, the second operational amplifier 110 includes a second non-inverting input 120, a second inverting input 118, and a second output 122. The first non-inverting input 112 and the second non-inverting input 120 are coupled to the outputs 124 and 126 of the sensor resistor bridge 128, respectively, such that the input voltage V applied to the first non-inverting input 112 and the second non-inverting input 120... 输入 Equal to the output signal voltage V generated by the sensor resistor bridge 128 SIG .

[0017] Output circuit 106 is formed by a first output terminal 116 and a second output terminal 122, and the output voltage V of the first output terminal and the second output terminal is... 输出 Input voltage V 输入 A certain proportion is larger, and this proportion is equal to the gain G of the PGA. As shown in the figure, operational amplifiers 108 and 110 include those with voltage dividers R respectively. F1 / R G 136 and R F2 / R G The negative feedback loop of 138 consists of non-inverting amplifiers 132 and 134, which are voltage dividers with resistors R respectively. F1 R F2 and R G Resistors 140, 142, and 144 are used to form the PGA. Therefore, the gain G of the PGA is 1 + 2R. F / R G , where R F = R F1 = R F2 This makes V 输出 = V 输入 ● (1 + 2 ● R F / R G The ADC (not shown) outputs voltage V. 输出 It is converted into a digital signal, which is then provided to a digital signal processor for processing.

[0018] Input voltage V 输入 Equal to the signal voltage V output by the sensor resistor bridge 128 SIG The signal voltage consists of a first component (output) voltage proportional to the physical quantity (e.g., pressure) sensed by sensor 130 and a zero-displacement voltage V. SIG(0)The second component of the voltage. Zero-quantity offset voltage V SIG(0) This corresponds to the voltage generated by the sensor when sensor 130 does not sense a physical quantity (e.g., when the quantity sensed by sensor resistor bridge 128 (e.g., pressure) is zero (0)). For example, in a typical embodiment, where sensor 130 includes a pressure sensor and sensor resistor bridge 128 includes a pressure sensor resistor bridge, the output voltage generated by the sensor resistor bridge can range from 1 mV / V to 5 mV / V, while the zero pressure offset voltage V SIG(0) It could be as high as 100 mV / V.

[0019] According to this disclosure, the offset voltage compensation circuit 100 will generate an offset compensation voltage V. OS At least one circuit in the input or output circuit of the PGA 102 is applied. For example, in various embodiments, such as Figure 1 As shown, the offset voltage compensation circuit 100 can compensate for the offset voltage V. OS The voltage is applied to the first inverting input 114 and / or the second inverting input 118, the first non-inverting input 112 and / or the second non-inverting input 120, or the first output 116 and / or the second output 122. In this way, the output voltage V of the PGA 102 can be obtained. 输出 At least essentially eliminate zero offset voltage V SIG(0) .

[0020] In the embodiment, the offset compensation voltage V OS Equal to or substantially equal to zero offset voltage V SIG(0) And it is proportional to the bias voltage applied to the sensor to sense the physical quantity. For example, in an embodiment, where sensor 130 includes a pressure sensor and the sensor resistor bridge includes a pressure resistor bridge, the offset compensation voltage V OS Equal to or substantially equal to zero pressure offset voltage V SIG(0) And the bridge voltage V applied to the pressure resistance bridge. 电桥 Proportional.

[0021] Figure 2A , Figure 2B and Figure 2C Example embodiments based on this disclosure are shown. Figure 1 An implementation of the offset voltage compensation circuit 100. For example... Figure 2A As shown, Figure 1The offset voltage compensation circuit 100 is configured as a sensor zero-quantity offset voltage compensation circuit 200, which includes a first programmable gain amplifier (PGA) 202 having an input loop 204 and an output loop 206. The PGA 202 includes a first operational amplifier (OA1) 208 and a second operational amplifier (OA2) 210. The first operational amplifier 208 includes a first non-inverting input 212, a first inverting input 214, and a first output 216. Similarly, the second operational amplifier 210 includes a second non-inverting input 218, a second inverting input 220, and a second output 222.

[0022] Input circuit 204 is configured to receive the signal output from sensor resistor bridge 228 of sensor 230. Specifically, as shown, the first non-inverting input terminal 212 and the second non-inverting input terminal 218 are coupled to the output terminals 224 and 226 of sensor resistor bridge 228, respectively, such that the input voltage V applied to the first non-inverting input terminal 212 and the second non-inverting input terminal 218 is... 输入 Equal to the output signal voltage V generated by the sensor resistor bridge 228 SIG .

[0023] Output circuit 206 is formed by a first output terminal 216 and a second output terminal 222, and the output voltage V1 of the first output terminal and the second output terminal is the input voltage V. 输入 A certain proportion is larger, and this proportion is equal to the gain G of the PGA. As shown in the figure, operational amplifiers 208 and 210 include those with voltage dividers R respectively. F1 / R G 236 and R F2 / R G The negative feedback loops of 238 and 232 are non-inverting amplifiers. These voltage dividers are composed of resistors R. F1 R F2 and R G Resistors 240, 242, and 244 are formed. Therefore, the voltage gain G1 of the first PGA 202 is 1 + 2R. F / R G , where R F = R F1 = R F2 .

[0024] Input voltage V 输入 Equal to the signal voltage V output by the sensor resistor bridge 228 SIG The signal voltage consists of a first component (output) voltage proportional to the physical quantity (e.g., pressure) sensed by sensor 230 and a zero offset voltage V. SIG(0) The second component of the voltage. Zero-quantity offset voltage V SIG(0)This corresponds to the voltage generated by the sensor when the sensor 230 does not sense a physical quantity (e.g., when the quantity sensed by the sensor resistor bridge 228 (e.g., pressure) is zero (0)). For example, in an embodiment, where the sensor 230 includes a pressure sensor and the sensor resistor bridge 228 includes a pressure sensor resistor bridge, the output voltage generated by the sensor resistor bridge can range from 1 mV / V to 5 mV / V, while the zero pressure offset voltage V SIG(0) It could be as high as 100 mV / V.

[0025] According to this disclosure, the sensor offset voltage compensation circuit 200 will generate an offset compensation voltage V. OS The input circuit of PGA 202 is applied. In this embodiment, the offset compensation voltage V... OS Equal to or substantially equal to zero offset voltage V SIG(0) And it is proportional to the bias voltage applied to sensor 230 to sense the physical quantity. For example, in an embodiment, where sensor 230 includes a pressure sensor and the sensor resistor bridge includes a pressure resistor bridge, the offset compensation voltage V OS Equal to or substantially equal to zero pressure offset voltage V SIG(0) And the bridge voltage V applied to the pressure resistance bridge. 电桥 Proportional.

[0026] Specifically, such as Figure 2A As shown, the sensor offset voltage compensation circuit 200 can compensate for voltage drop across a resistor R. O The offset resistor 246 generates an offset voltage V equal to zero pressure across its terminals. SIG(0) The voltage is used to compensate for the offset voltage V. OS The bias voltage (e.g., bridge voltage V) applied to the inverting inputs 214 and 220 of the first operational amplifier 208 and the second operational amplifier 210 is also applied. In the illustrated embodiment, the bias voltage applied to the sensor 230 is also... 电桥 The voltage-to-current converter (V / I) 248, 250 converts the current into current to generate the offset current I. P and I N In embodiments, these offset currents are equal or substantially equal and are adjusted such that the offset compensation voltage V OS Equal to the generated offset current I P and I N Multiply by the resistance R of the offset resistor 246 O Therefore, V OS = I ●R O , where, I = I P = I N .

[0027] Figure 2B and Figure 2C This demonstrates how a sensor offset voltage compensation circuit 200 can be used to generate an offset current I. P and I N Example voltage-to-current converters (V / I) 248, 250. In embodiments, the offset compensation voltage V... OS The offset voltage V is generated to be equal to or at least substantially equal to zero. SIG(0) The offset compensation voltage and the bias (bridge) voltage V 电桥 Proportional. Therefore, V OS = V SIG(0) = ℇ VOS ● V 电桥 .like Figure 2B As shown, voltage-to-current converters (V / I) 248 and 250 draw voltages from a bias (bridge) voltage V. 电桥 Generate offset current I P and I N These offset shift currents I P and I N (They are equal in the embodiments) can be expressed as I = I P =I N = K I ● V 电桥 / R 微调 , where R 微调 It is a variable trimmer resistor, selected by digital signal processor 252 and trimmer circuits 254 and 256. Figure 2C (This is) generated. However, it is conceivable that in many embodiments, the offset current I... P with I N There will be a mismatch between them. Therefore, the offset current I P It can be done through I P = I ● (1 + I P / I P The offset current I is determined. N It can be done through I N = I● (1 + I N / I N ) Determined, among which, I P and I N These mismatches are described.

[0028] Figure 2CExample trimmer circuits 254 and 256 for voltage-to-current converters (V / I) 248 and 250 are shown. As illustrated, trimmer circuits 254 and 256 employ a digital-to-analog converter (DAC) 258 to select the trimmer resistor R in response to a digital signal from a digital signal processor 252. 微调 In this embodiment, the DAC 258 is used to generate the resistor R. 微调 The number of fine-tuning bits is based on the minimum span and maximum zero-scale offset voltage V of the first component (output) voltage of the signal output by sensor 230. SIG(0) It is determined. For example, for a minimum span of 1 mV / V and a maximum zero offset voltage V. SIG(0) For a 50 mV / V sensor 230, the DAC258 will require at least nine (9) bits to extend the pressure range to 20 dB below the minimum span, so a twelve (12) bit DAC 258 will be used.

[0029] In the illustrated embodiment, the digital signal processor 252 selects the gain G of the PGA 202 and controls the offset compensation voltage V. OS The generation and application to PGA 202 cause the offset compensation voltage V to... OS The magnitude and polarity of the zero-equal offset voltage V cancels out the zero-equal offset voltage. SIG(0) .like Figure 2A As shown, the digital signal processor 252 controls switches K1260, K2262, K3264, K4266, K5268, and K6270. Switch K1260 connects the output terminals 224 and 226 of the sensor 230 to the input circuit 204 of the first PGA 202. Switch K2262 is used for calibration of the sensor offset voltage compensation circuit 200. Switches K3 and K4 are used to select the offset compensation voltage V. OS The polarity. The positions of switches K3264 and K4266 are determined by the zero-quantity offset voltage V. SIG(0) The polarity is determined and correspondingly closed / opened (flipped) by digital signal processor 252. Switches K5268 and K6270 connect / disconnect their respective voltage-to-current converters (V / I) 248 and 250.

[0030] When the input voltage equals the offset compensation voltage (V) 输入 = V OS When ), the output voltage (V1) of the first PGA 202 is V1 = (V OS + V OS1 - I P ● R O ) ● (1 + 2 ● R F / R G ) + R F ● (I N - IP ), where V OS1 = V OS1b - V OS1a Since the gain (G1) of the first PGA 202 is G1 = 1 + 2 ● R F / R G Therefore, the output voltage V1 of the first PGA 202 is determined according to V1=[ℇ VOS -K I ● (R O / R 微调 )] ● V 电桥 ● G1+ V OS1 ● G1+ K I ● V 电桥 ● (R F / R 微调 ) ● ( I N / I N - I P / I P This is determined by the fine-tuning resistor R. 微调 = K I ● R O / ℇ VOS When this occurs, zero-scale offset voltage cancellation will happen. Therefore, the sensor offset voltage compensation circuit 200 provides a zero-scale offset voltage V. SIG(0) The elimination of this makes resistor R G The voltage across the terminals is only, or at least primarily, the first component (output) voltage of sensor 330, with little or no zero-volume offset voltage V. SIG(0) Therefore, zero-equal-weight offset compensation is independent of the bias (bridge) voltage (V) of sensor 230. 电桥 ) and the gain (G1) of PGA 202.

[0031] like Figure 2A As shown, the sensor offset voltage compensation circuit 200 further includes a second programmable gain amplifier (PGA) 272. The second PGA 272 converts the output voltage V1 of the first PGA 202 into a second output voltage V2 with lower impedance. An analog-to-digital converter (ADC) 274 converts the output voltage V2 into a digital signal, which is provided to a digital signal processor 252 for processing.

[0032] Figure 3A , Figure 3B and Figure 3C Example embodiments based on this disclosure are shown. Figure 1 An additional embodiment of the offset voltage compensation circuit 100. For example... Figure 3A and Figure 3CAs shown, Figure 1 The offset voltage compensation circuit is configured as a sensor zero offset voltage compensation circuit 300, which includes a programmable gain amplifier (PGA) 302 having an input loop 304 and an output loop 306. The PGA 302 includes a first operational amplifier (OA1) 308 and a second operational amplifier (OA2) 310. The first operational amplifier 308 includes a first non-inverting input 312, a first inverting input 314, and a first output 316. Similarly, the second operational amplifier 310 includes a second non-inverting input 318, a second inverting input 320, and a second output 322.

[0033] Input circuit 304 is configured to receive the signal output from sensor resistor bridge 328 of sensor 330. Specifically, as shown, the first non-inverting input terminal 312 and the second non-inverting input terminal 318 are coupled to the output terminals 324 and 326 of sensor resistor bridge 328, respectively, such that the input voltage V applied to the first non-inverting input terminal 312 and the second non-inverting input terminal 318... 输入 Equal to the output signal voltage V generated by the sensor resistor bridge 328 SIG .

[0034] Output circuit 306 is formed by first output terminal 316 and second output terminal 322, and the output voltage V of this output circuit is... 输出 Input voltage V 输入 A certain proportion is larger, and this proportion is equal to the gain G of PGA 302. As shown in the figure, operational amplifiers 308 and 310 include those with voltage dividers R respectively. F1 / R G 336 and R F2 / R G The negative feedback loop of 338 consists of non-inverting amplifiers 332 and 334, which are voltage dividers with resistors R respectively. F1 R F2 and R G Resistors 340, 342, and 344 are used to form the PGA 302. Therefore, the gain G of the PGA 302 is 1 + 2 ● R. F / R G , where R F = R F1 = R F2 .

[0035] Input voltage V 输入 Equal to the signal voltage V output by the sensor resistor bridge 328 SIG The signal voltage consists of a first component (output) voltage proportional to the physical quantity (e.g., pressure) sensed by sensor 330 and a zero offset voltage V. SIG(0) The second component of the voltage. Zero-quantity offset voltage VSIG(0) This corresponds to the voltage generated by the sensor when the sensor 330 does not sense a physical quantity (e.g., when the quantity sensed by the sensor resistor bridge 328 (e.g., pressure) is zero (0)). For example, in an embodiment, where the sensor 330 includes a pressure sensor and the sensor resistor bridge 328 includes a pressure sensor resistor bridge, the output voltage generated by the sensor resistor bridge can range from 1 mV / V to 5 mV / V, while the zero pressure offset voltage V SIG(0) It could be as high as 100 mV / V.

[0036] In the illustrated embodiment, the sensor offset voltage compensation circuit 300 generates an offset compensation voltage V. OS The offset compensation voltage applied to the output circuit 306 of the PGA 302 is equal to or substantially equal to the zero offset voltage V. SIG(0) And it is proportional to the bias voltage applied to sensor 330 to sense the physical quantity. For example, in an embodiment, where sensor 330 includes a pressure sensor and the sensor resistor bridge includes a pressure resistor bridge, the offset compensation voltage V OS Equal to or substantially equal to zero pressure offset voltage V SIG(0) And the bridge voltage V applied to the pressure resistance bridge. 电桥 Proportional.

[0037] Specifically, the sensor offset voltage compensation circuit 300 includes generating an offset compensation current I. OS The programmable current source 346 generates a current I. CAL The output OUT1 or OUT2 of PGA 302 is provided via switch 348, depending on the zero-offset voltage V. SIG(0) The polarity of the current I. OS The offset compensation provided is implemented in the output loop 306 of the PGA 302, rather than in the input loop 304.

[0038] Figure 3B It can be shown Figure 3A The offset voltage compensation circuit 300 uses an offset current I to generate an offset voltage I. OS Example programmable current source 346. In an embodiment, offset compensation voltage V... OS Equal to or at least substantially equal to zero offset voltage V SIG(0) The offset compensation voltage and the bias (bridge) voltage V 电桥 Proportional. Therefore, V OS = V SIG(0) = ℇ ● V 电桥 .like Figure 3B As shown, the voltage programmable current source 346 draws current from the bias (bridge) voltage V. 电桥Generate offset current I OS .

[0039] As mentioned above, the gain G of the PGA 302 is equal to 1 + 2 ● (R F / R G Therefore, the output voltage V 输出 -R F2 ●I OS + V 输入 ● [1 + (R F1 + R F2 ) / R G ] = -R F2 ● I OS + V 输入 ● G. Therefore, when V 输入 = V OS When, then V 输出 = -R F ● I OS + V OS ● [1 + 2 ● (R F / R G )] = -R F ● I OS + V OS ● G. Therefore, in order to achieve input offset voltage calibration: V 输出 = 0, which makes I OS = G ● (V OS / R F However, from Figure 3B Let's see, I OS = V 电桥 / [(K + 1) ● R 微调 ], where the offset compensation voltage and the bias (bridge) voltage V OS = ℇ ● V 电桥 Proportional, and in which R 微调 It is a variable trimmer resistor selected by a digital signal processor. Therefore, 1 = ℇ ● (K + 1) ● G ● (R 微调 / R F Therefore, zero-quantity offset compensation is based on resistor ratios and is achieved through fine-tuning resistor R. 微调 = R F This occurs when / [ℇ ● (K + 1) ● G].

[0040] like Figure 3B As shown, the programmable current source 346 includes a trimmer resistor R for selecting the trimmer resistor. 微调The fine-tuning circuit 368. In an embodiment, the fine-tuning circuit 368 may employ a digital-to-analog converter (DAC) to select the fine-tuning resistor R in response to a digital signal from a digital signal processor. 微调 (See Figure 2C ).

[0041] exist Figure 3C In the sensor offset voltage compensation circuit 300, a second programmable gain amplifier (PGA) 350 is further included, which is used to regulate the output voltage V of the first PGA 302. O1 The impedance is shown in the figure. The second PGA 350 includes a third operational amplifier (OA3) 352 having a third non-inverting input 354, a third inverting input 356, and a third output 358, and a fourth operational amplifier (OA4) 360 having a fourth non-inverting input 364, a fourth inverting input 362, and a fourth output 366. The third non-inverting input 354 and the fourth non-inverting input 364 are respectively connected to resistors 370 and 372 (each having a resistance R). O It is coupled to the first output terminal 316 of the first operational amplifier 308 and the second output terminal 322 of the second operational amplifier 310, and has a voltage V. O1 .

[0042] The output voltage V of the third output terminal 358 and the fourth output terminal 366 O2 The output voltage of the first PGA 302 (at Figure 3C The middle is represented as V O1 The gain of the second PGA 350 is a certain percentage larger than that of the third operational amplifier 352, which is equal to the gain G2 of the fourth operational amplifier 360. As shown in the figure, the third operational amplifier 352 and the fourth operational amplifier 360 include components that have passed through voltage dividers R. F3 / R G 378 and R F4 / R G The negative feedback loops of the 380 and the non-inverting amplifiers of the 374 and 376 are voltage dividers, each with a resistor R. F3 R F4 and R G2 Resistors 382, ​​384, and 386 are formed, wherein R F = R F1 = R F2 = R F3 = R F4 And R G = R G1 = R G2 Therefore, the gain G2 of the second PGA 350 is 1 + 2● R F / R G .

[0043] In the illustrated embodiment, the sensor offset voltage compensation circuit 300 includes generating a second offset compensation current I. OS2 The second programmable current source 388. (In Figure 3C In the above, the current generated by the first programmable current source 346 is represented as I. OS1 The generated current I OS2 The switch 390 provides the non-inverting input 354 of the third operational amplifier 352 or the non-inverting input 364 of the fourth operational amplifier 360 to the second PGA 350, depending on the zero-scale offset voltage V. SIG(0) The polarity of the current I. OS2 The offset compensation provided is manifested in the input loop 392 of the second PGA 350.

[0044] for Figure 3C The offset voltage compensation circuit shown adds a resistor R. O The offset resistors 370 and 372 enable the offset compensation voltage V OS The calibration is independent of the feedback resistor R of PGA 302 and 350. F The first PGA 302 output voltage V O1 equal to -R O ● I OS2 -R F2 ● I OS1 + V 输入 ● [1 + (R F1 + R F2 ) / R G Assume the input voltage equals the offset compensation voltage (V). 输入 = V OS When no offset resistor (R) is provided O When (= 0), the output voltage V of the first PGA 302 is... O1 -R F ● I0+ V OS ●[1 + 2 ● (R F / R G To calibrate the circuit's zero-offset voltage V. SIG(0) When the offset current I O Equal to (V) OS / RF ) ●[1 + 2 ● (R F / R G When )], the output voltage of the first PGA 302 is zero (V O1 = 0). Therefore, when the resistance R O When it is zero, the offset compensation voltage V is finely adjusted based on the offset current I0. OS The calibration is the feedback resistor RF The function. However, if an offset resistance R equal to half the gain resistance RG is added... O (R) O = R G / 2), then the output voltage V O1 Equal to (V) OS - R O ● I O ) ● [1 + 2● (R F / R G Assume V 输入 = V OS To calibrate the circuit's zero-scale offset voltage V SIG(0) When the offset current I O equals V OS / R O At that time, the output voltage of the first PGA 302 is zero (V). O1 = 0). Therefore, when as Figure 3C The figure shows a resistor R that is equal to half the gain resistor. O At that time, the offset compensation voltage V is finely adjusted based on the offset current I0. OS The calibration is independent of the feedback resistor R F .

[0045] like Figure 1 , Figure 2A , Figure 3A and Figure 3C As shown, sensor offset voltage compensation circuits 100, 200, and 300, together with their respective sensors 130, 230, and 330, form sensor systems 146. Figure 1 ), 276 ( Figure 2A ), 394 Figure 3A and Figure 3C The sensor system may include other components. In embodiments, the sensor offset voltage compensation circuits 100, 200, 300, sensors 130, 230, 330, and / or sensor systems 146, 276, 394 may be fabricated as one or more integrated circuit chips, such as application-specific integrated circuit (ASIC) chips.

[0046] Sensors 130, 230, and 330 may include any type of sensor capable of generating a zero-offset voltage as described herein. For example, in an embodiment, sensors 130, 230, and 330 may include a pressure bridge sensor. In such an embodiment, sensors 130, 230, and 330 may employ any of a variety of manufacturing techniques, such as silicon (single crystal), polycrystalline silicon thin film, bonded metal foil, thick film, silicon-on-sapphire, sputtered thin film, etc.

[0047] Figure 4An example sensor 400 according to an example embodiment of this disclosure is shown. The sensor 400 (which may include a pressure sensor in embodiments) includes a sensor resistance bridge 402 employing bonded or molded strain gauges (shown as 404, 406, 408, 410) formed in a substrate to detect strain generated in the material due to applied pressure. The strain gauges 404, 406, 408, 410 utilize the piezoresistive effect, such that the resistance of the strain gauges 404, 406, 408, 410 increases as the pressure deforms the material of the substrate. As shown, the strain gauges 404, 406, 408, 410 are arranged in a bridge circuit configuration (e.g., a Wheatstone bridge configuration). In the illustrated embodiment, the strain gauges 404, 406, 408, 410 of the sensor resistance bridge 402 are arranged in a closed bridge configuration. However, it is contemplated that the sensor resistance bridge 402 may be arranged in a half-open configuration, a fully open configuration, etc. Sensor 400 can utilize a variety of technologies, such as silicon (single crystal), polycrystalline silicon thin film, bonded metal foil, thick film, silicon on sapphire, sputtered thin film, etc.

[0048] As shown in the figure, when a bias (bridge) voltage V is applied to the sensor resistor bridge 402... 电桥 At this time, a voltage V is generated across the output terminals 412 and 414. SIG As mentioned above, this voltage V SIG This includes an output voltage V that is proportional to the physical quantity (e.g., pressure) sensed by sensor 400. SIG The first component equals the zero offset voltage V SIG(0) The second component voltage. Zero-quantity offset voltage V SIG(0) This corresponds to the voltage generated by the sensor when the sensor 400 does not sense a physical quantity (e.g., when the quantity sensed by the sensor resistance bridge 402 (e.g., pressure) is zero (0)). This zero-quantity offset voltage V SIG(0) This is caused by structural imperfections in the sensor resistor bridge 402, such as resistor mismatches in strain gauges 404, 406, 408, and 410. These structural imperfections cause sensor 400 to have an output voltage even when no quantity (e.g., pressure) is sensed (e.g., the sensed quantity is zero (0)). For example, in a typical embodiment, where sensor 130 includes a pressure sensor and sensor resistor bridge 128 includes a pressure sensor resistor bridge, the output voltage generated by the sensor resistor bridge can range from 1 mV / V to 5 mV / V, while the zero pressure offset voltage V... SIG(0) It could be as high as 100 mV / V.

[0049] When describing elements or examples of any aspect of this disclosure, the articles “a,” “an,” “the,” and “said” are intended to indicate the presence of one or more of these elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements besides those listed.

[0050] Having described in detail various aspects of this disclosure, it will be apparent that modifications and variations may be made without departing from the scope of these aspects as defined by the appended claims. Because various changes can be made to the above-described structures, products, and methods without departing from the scope of these disclosures, it is intended that all subject matter contained in the foregoing specification and illustrated in the accompanying drawings be construed as illustrative rather than restrictive.

Claims

1. An offset voltage compensation circuit, comprising: The first amplifier has a first input terminal, a first inverting input terminal, and a first output terminal; as well as The second amplifier has a second input terminal, a second inverting input terminal, and a second output terminal; The first input terminal and the second input terminal form an input loop, which is configured to receive an input voltage from a sensor. The input voltage includes a sensor output voltage proportional to the physical quantity sensed by the sensor and a zero-offset voltage corresponding to the voltage output by the sensor when the sensor does not sense the physical quantity. The first output terminal and the second output terminal form an output circuit for providing an output voltage to the analog-to-digital converter, and Specifically, an offset compensation voltage is applied to the first inverting input terminal and the second inverting input terminal using a resistor. The offset compensation voltage is applied to at least substantially eliminate the zero-quantity offset voltage from the output voltage. The offset compensation voltage is proportional to the bias voltage applied to the sensor to sense the physical quantity, and the offset compensation voltage includes the offset current generated from the bias voltage applied across the resistor.

2. The offset voltage compensation circuit as described in claim 1, wherein, The first amplifier and the second amplifier include operational amplifiers.

3. The offset voltage compensation circuit as described in claim 1, wherein, The output circuit is configured to be coupled to an analog-to-digital converter for converting the output voltage into a digital signal, which is provided to a digital signal processor, which is configured to generate the offset current in response to this.

4. The offset voltage compensation circuit of claim 3, further comprising a voltage-to-current converter configured to generate the offset current from the bias voltage using a variable trimming resistor selected by the digital signal processor via a trimming circuit.

5. The offset voltage compensation circuit as described in claim 4, wherein, The trimming circuit includes a digital-to-analog converter coupled to the digital signal processor, the digital-to-analog converter being configured to select a trimming resistor in response to a digital signal from the digital signal processor.

6. The offset voltage compensation circuit as described in claim 5, wherein, The digital signal processor controls the offset compensation voltage so that the magnitude and polarity of the offset compensation voltage cancel out the zero offset voltage.

7. The offset voltage compensation circuit as described in claim 1, wherein, The sensor includes a pressure sensor, and the physical quantity includes pressure.

8. An offset voltage compensation circuit, comprising: A programmable gain amplifier, configured to be coupled to a sensor capable of operating for sensing a physical quantity, includes: A first amplifier has a first input terminal, a first inverting input terminal, and a first output terminal; and The second amplifier has a second input terminal, a second inverting input terminal, and a second output terminal; The first input terminal and the second input terminal form an input loop, which is configured to receive an input voltage from a sensor. The input voltage includes a sensor output voltage proportional to the physical quantity sensed by the sensor and a zero-offset voltage corresponding to the voltage output by the sensor when the sensor does not sense the physical quantity. The first output terminal and the second output terminal form an output circuit for providing an output voltage to the analog-to-digital converter, and Specifically, an offset compensation voltage is applied to the first inverting input terminal and the second inverting input terminal using a resistor. This offset compensation voltage is applied to at least substantially eliminate the zero-quantity offset voltage from the output voltage. The offset compensation voltage is proportional to the bias voltage applied to the sensor to sense the physical quantity, and the offset compensation voltage includes an offset current generated from the bias voltage applied across the resistor. An analog-to-digital converter is used to convert the output voltage into a digital signal for processing.

9. The offset voltage compensation circuit of claim 8, further comprising a digital signal processor configured to receive the digital signal from the analog-to-digital converter and generate the current in response thereto.

10. The offset voltage compensation circuit of claim 9, further comprising a voltage-to-current converter configured to generate the offset current from the bias voltage using a variable trimming resistor selected by the digital signal processor via a trimming circuit.

11. The offset voltage compensation circuit as described in claim 10, wherein, The trimming circuit includes a digital-to-analog converter coupled to the digital signal processor, the digital-to-analog converter being configured to select a trimming resistor in response to a digital signal from the digital signal processor.

12. The offset voltage compensation circuit as described in claim 11, wherein, The digital signal processor controls the offset compensation voltage so that the magnitude and polarity of the offset compensation voltage cancel out the zero offset voltage.

13. The offset voltage compensation circuit as described in claim 8, wherein, The sensor includes a pressure sensor, and the physical quantity includes pressure.

14. A sensor assembly, comprising: A sensor capable of sensing a physical quantity is configured to generate a first voltage when a bias voltage is applied to the sensor, the first voltage including a sensor output voltage proportional to the physical quantity sensed by the sensor and a zero-offset voltage corresponding to the sensor output voltage generated by the sensor when the sensor does not sense the physical quantity. as well as The signal processing component includes: A programmable gain amplifier interconnected with the sensor includes: a first amplifier having a first input terminal, a first inverting input terminal, and a first output terminal; and a second amplifier having a second input terminal, a second inverting input terminal, and a second output terminal. The first input terminal and the second input terminal form an input loop, which is configured to receive an input voltage from a sensor. The input voltage includes a sensor output voltage proportional to the physical quantity sensed by the sensor and a zero-offset voltage corresponding to the voltage output by the sensor when the sensor does not sense the physical quantity. The first output terminal and the second output terminal form an output circuit for providing an output voltage to the analog-to-digital converter, and The offset compensation voltage is applied to the first inverting input terminal and the second inverting input terminal using a resistor. The offset compensation voltage is applied to at least substantially eliminate the zero offset voltage from the output voltage. The offset compensation voltage is proportional to the bias voltage applied to the sensor to sense the physical quantity, and the offset compensation voltage includes the offset current generated from the bias voltage applied across the resistor. An analog-to-digital converter is used to convert the output voltage into a digital signal; and A digital signal processor is configured to receive the digital signal from the analog-to-digital converter and, in response, provide the offset compensation voltage to the programmable gain amplifier.

15. The sensor assembly of claim 14, wherein, The first amplifier and the second amplifier include operational amplifiers.

16. The sensor assembly of claim 14, further comprising a voltage-to-current converter configured to generate the offset current from the bias voltage using a variable trimming resistor selected by the digital signal processor via trimming circuitry.

17. The sensor assembly of claim 16, wherein, The trimming circuit includes a digital-to-analog converter coupled to the digital signal processor, the digital-to-analog converter being configured to select a trimming resistor in response to a digital signal from the digital signal processor.

18. The sensor assembly of claim 17, wherein, The digital signal processor controls the offset compensation voltage so that the magnitude and polarity of the offset compensation voltage cancel out the zero offset voltage.

19. The sensor assembly of claim 14, wherein, The sensor includes a sensor resistance bridge that employs multiple strain gauges.

20. The sensor assembly of claim 14, wherein, The sensor includes a pressure sensor, and the physical quantity includes pressure.

Images