WO2020024122A1 - 一种距离传感器接收模拟前端电路及距离传感器 - Google Patents

一种距离传感器接收模拟前端电路及距离传感器 Download PDF

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Publication number
WO2020024122A1
WO2020024122A1 PCT/CN2018/097880 CN2018097880W WO2020024122A1 WO 2020024122 A1 WO2020024122 A1 WO 2020024122A1 CN 2018097880 W CN2018097880 W CN 2018097880W WO 2020024122 A1 WO2020024122 A1 WO 2020024122A1
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Prior art keywords
electronic switch
terminal
module
amplifier
input terminal
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PCT/CN2018/097880
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English (en)
French (fr)
Inventor
张孟文
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深圳市汇顶科技股份有限公司
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Application filed by 深圳市汇顶科技股份有限公司 filed Critical 深圳市汇顶科技股份有限公司
Priority to PCT/CN2018/097880 priority Critical patent/WO2020024122A1/zh
Priority to CN201880001032.XA priority patent/CN109075755B/zh
Publication of WO2020024122A1 publication Critical patent/WO2020024122A1/zh

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/45—Differential amplifiers
    • H03F3/45071—Differential amplifiers with semiconductor devices only
    • H03F3/45076—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier
    • H03F3/45179—Differential amplifiers with semiconductor devices only characterised by the way of implementation of the active amplifying circuit in the differential amplifier using MOSFET transistors as the active amplifying circuit
    • H03F3/45183—Long tailed pairs
    • H03F3/45188—Non-folded cascode stages
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/68—Combinations of amplifiers, e.g. multi-channel amplifiers for stereophonics
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2203/00—Indexing scheme relating to amplifiers with only discharge tubes or only semiconductor devices as amplifying elements covered by H03F3/00
    • H03F2203/45—Indexing scheme relating to differential amplifiers
    • H03F2203/45396—Indexing scheme relating to differential amplifiers the AAC comprising one or more switches

Definitions

  • the present application relates to the technical field of distance sensors, and in particular, to a distance sensor receiving analog front-end circuit and a distance sensor.
  • Distance sensors are generally divided into two types: capacitive and optical.
  • the optical distance sensor needs to adopt a low-noise current-voltage integrator to integrate and amplify the received photoelectric current and convert it into a voltage.
  • the analog-to-digital converter at the back end converts it into a digital signal for processing.
  • a double integration integrator is usually used in the prior art, that is, the signal containing the background photocurrent signal and the useful signal is first integrated, and then the signal containing only the background photocurrent signal is integrated
  • the differential-mode signals of the two are converted by an analog-to-digital converter.
  • This processing method has the following disadvantages: first, the integrated analog signal needs to be stored twice with two large capacitors, which will make the area of the chip very large; second, because the two capacitors need to work in a "ping-pong" manner Therefore, both capacitors will sample large switching noise, especially the integrator in the form of an amplifier and two capacitors, which is more serious.
  • the purpose of some embodiments of the present application is to provide a distance sensor receiving analog front-end circuit and a distance sensor to solve the problems of large chip area and large noise in the prior art.
  • An embodiment of the present application provides an analog front-end circuit for receiving a distance sensor, including a photodiode, a current integration module, an inverting amplifier module, a reset module for resetting the current integration module, and a photodiode.
  • a canceling module for a direct current component in the background photocurrent a first end of the canceling module is connected to a power supply terminal; a second end of the canceling module is respectively connected to the photodiode, the first end of the current integration module, and the The output terminal of the reset module; the third terminal of the cancellation module is connected to the first terminal of the inverting amplifier module; the second terminal of the inverting amplifier module is connected to the second terminal of the current integration module and the A first input terminal of the reset module and a reference voltage input to the second input terminal of the reset module; wherein the voltage of the first input terminal of the reset module is equal to the voltage of the second input terminal of the reset module, and the reset
  • the module and the current integration module constitute a unity gain amplifying unit.
  • An embodiment of the present application further provides a distance sensor including a transmitting section and a receiving section; the transmitting section includes a light emitting diode and a driving circuit for driving the light emitting diode; and the receiving section includes the distance sensor receiving device as described above.
  • a distance sensor including a transmitting section and a receiving section; the transmitting section includes a light emitting diode and a driving circuit for driving the light emitting diode; and the receiving section includes the distance sensor receiving device as described above.
  • An analog front-end circuit and an analog-to-digital converter; the analog-to-digital converter is connected to the second end of the current integration module.
  • the embodiments of the present application firstly connect a reset module between the first end and the second end of the current integration module, and the reset module and the current integration module form a unit gain amplifying unit.
  • the reset module The voltage of the output terminal is equal to the voltage of its two input terminals, that is, the voltage of the first terminal and the second terminal of the current integration module are equal (both equal to the reference voltage), so as to achieve the purpose of resetting the current integration module.
  • This reset method avoids the process of connecting a switch between the first end and the second end of the current integration module in the prior art and using the switch to reset the current integration module, thereby reducing the non-compliance brought by the switch. Linearity and noise issues.
  • only one current integration module is provided, which simplifies the structure of the distance sensor and also helps to reduce the area of the front end of the distance sensor and reduce the cost.
  • the cancellation module includes a sampling capacitor and a sampling electronic switch; an input terminal of the sampling electronic switch is connected to one end of the sampling capacitor as the first terminal of the cancellation module; and the sampling electronic switch An output terminal of the cancellation module is used as the second terminal of the cancellation module; a control terminal of the sampling electronic switch is connected with the other terminal of the sampling capacitor as the third terminal of the cancellation module.
  • a specific structure of the offset module is provided.
  • An inverting amplifier module is connected to the control end of the sampling electronic switch. The inverting amplifying module can provide a wider range of voltage to the control end of the sampling electronic switch (which can start from 0). In this way, the sampling electronic switch The voltage at the control end can be changed over a wider range.
  • the embodiment of the present application can achieve the purpose by applying a smaller voltage to the control terminal of the sampling electronic switch.
  • the purpose can only be achieved by setting a larger size (larger width to length ratio) sampling electronic switch and increasing the transconductance of the sampling electronic switch. The larger the transconductance of the sampling electronic switch is, the larger the noise it brings. Therefore, compared with the prior art, the embodiment of the present application can set a smaller-sized sampling electronic switch, thereby reducing the noise it brings.
  • the current integration module includes a transconductance amplifier and an integration capacitor; an input terminal of the transconductance amplifier is connected to one end of the integration capacitor, and as the first end of the current integration module, the The output terminal of the conducting amplifier is connected with the other end of the integration capacitor, and serves as the second end of the current integration module.
  • the transconductance amplifier specifically includes: a first electronic switch and a second electronic switch; a control terminal of the first electronic switch inputs a first bias voltage, and an input terminal of the first electronic switch is connected to the power terminal An output terminal of the first electronic switch is connected with an input terminal of the second electronic switch as the output terminal of the transconductance amplifier, and the control terminal of the second electronic switch is the transconductance The input terminal of the amplifier and the output terminal of the second electronic switch are grounded.
  • a specific structure of the transconductance amplifier is provided.
  • the inverting amplifier module includes an inverting amplifier unit and a first control switch; one end of the first control switch serves as the first end of the inverting amplifier module, and the other end of the first control switch The output terminal of the inverting amplifier unit is connected, and the input terminal of the inverting amplifier unit is used as the second terminal of the inverting amplifier module.
  • a specific structure of the inverting amplification module is provided.
  • the inverting amplifier unit is an inverting amplifier or a broadband amplifier. Two implementations of the inverting amplification unit are provided.
  • the bandwidth of the wideband amplifier is at least twice the gain-bandwidth product of the sample-and-hold loop; wherein the sample-and-hold loop is the cancellation module, the inverting amplifier module, the current integration module, and A loop formed by the photodiode.
  • the broadband amplifier specifically includes: a third electronic switch and a fourth electronic switch; an input terminal of the third electronic switch is connected to the power source terminal, a control terminal, an output terminal of the third electronic switch, and the first electronic switch; The input terminals of the four electronic switches are connected together as the output terminal of the wideband amplifier, the control terminal of the fourth electronic switch is used as the input terminal of the wideband amplifier, and the output terminal of the fourth electronic switch is grounded.
  • the reset module includes an error amplifier and a second control switch; a forward signal input terminal of the error amplifier is used as the first input terminal of the reset module; and a reverse signal input terminal of the error amplifier is used as The second input terminal of the reset module; the output terminal of the error amplifier is connected to one end of the second control switch, and the other end of the second control switch is used as the output terminal of the reset module.
  • the error amplifier specifically includes a fifth electronic switch, a sixth electronic switch, a seventh electronic switch, an eighth electronic switch, and a ninth electronic switch; an input terminal of the fifth electronic switch is connected to the power terminal, and A control terminal of the fifth electronic switch inputs a second bias voltage, and an output terminal of the fifth electronic switch is respectively connected to the input terminal of the sixth electronic switch and the input terminal of the seventh electronic switch; the sixth electronic switch The control terminal of the switch is used as the forward signal input terminal of the error amplifier, and the output terminal of the sixth electronic switch is connected to the input terminal, the control terminal of the eighth electronic switch, and the control terminal of the nine electronic switch, respectively.
  • the control terminal of the seventh electronic switch is used as the reverse signal input terminal of the error amplifier, and the output terminal of the seventh electronic switch is connected with the input terminal of the ninth electronic switch as the The output terminal of the error amplifier, the control terminal of the eighth electronic switch is connected to the control terminal of the ninth electronic switch, the output terminal of the eighth electronic switch and the ninth electronic switch.
  • the outputs of the sub-switches are grounded.
  • a specific structure of the error amplifier is provided.
  • the circuit further includes a third control switch; the second terminal of the cancellation module is connected to the first terminal of the current integration module and the output terminal of the reset module through the third control switch.
  • FIG. 1 is a schematic structural diagram of a distance sensor receiving an analog front-end circuit according to a first embodiment of the present application
  • FIG. 2 is a schematic structural diagram of a current sampling phase according to a first embodiment of the present application
  • FIG. 3 is a schematic structural diagram of a reset phase according to a first embodiment of the present application.
  • FIG. 4 is a schematic structural diagram of a current integration phase according to a first embodiment of the present application.
  • FIG. 6 is a schematic structural diagram of an analog-to-digital conversion phase according to a first embodiment of the present application
  • FIG. 7 is a schematic structural diagram of a transconductance amplifier according to a second embodiment of the present application.
  • FIG. 8 is a schematic structural diagram of a wideband amplifier according to a second embodiment of the present application.
  • FIG. 9 is a schematic structural diagram of an error amplifier according to a second embodiment of the present application.
  • FIG. 10 is a schematic structural diagram of a distance sensor according to a third embodiment of the present application.
  • the first embodiment of the present application relates to a distance sensor receiving an analog front-end circuit.
  • the circuit includes a cancellation module 11, an inverting amplifier module 12, a reset module 13, a current integration module 14, and a photodiode (PD) 15.
  • the capacitor Cp is a parasitic capacitance inside the photodiode 15.
  • the first terminal of the cancellation module 11 is connected to the power supply VDD terminal; the second terminal of the cancellation module 11 is connected to the cathode of the photodiode 15, the output terminal of the reset module 13, and the first terminal of the current integration module 14, respectively, and the anode of the photodiode 15 is grounded to VSS.
  • the third end of the canceling module 11 is connected to the first end of the inverting amplification module 12; the second end of the inverting amplification module 12 is connected to the second end of the current integration module 14 and the first input of the reset module 13 respectively, and the reset module
  • the second input terminal of 13 inputs a reference voltage Vcm.
  • the current Id output by the cancellation module 11 may be used to cancel the direct component Ipd in the background photocurrent of the photodiode 15.
  • the cancellation module 11 may include a sampling capacitor Ch and a sampling electronic switch M0.
  • the input terminal of the sampling electronic switch M0 is connected to one end of the sampling capacitor Ch as the first terminal of the cancellation module 11; the output terminal of the sampling electronic switch M0 is used as the second terminal of the cancellation module 11; the sampling electronic switch M0
  • the control terminal is connected to the other terminal of the sampling capacitor Ch as the third terminal of the cancellation module 11.
  • FIG. 1 illustrates the sampling electronic switch M0 as a PMOS tube as an example, but it is not limited to this. In practical applications, NMOS tubes or other electronic tubes can also be used.
  • the main function of the inverting amplifier module 12 is to invert the input voltage (that is, the voltage at the second terminal of the inverting amplifier module 12), and provide the inverted voltage as a bias voltage to the sampling electronic switch M0, thereby triggering the sampling
  • the electronic switch M0 outputs a current Id equal to the magnitude of the DC component Ipd in the background photocurrent of the photodiode 15 to the photodiode 15 to cancel the DC component Ipd.
  • the inverting amplifier module 12 may include an inverting amplifier unit U1 and a first control switch S1; wherein one end of the first control switch S1 is used as the first end of the inverting amplifier module 12; the first control switch S1 The other terminal is connected to the output terminal of the inverting amplifier unit U1, and the input terminal of the inverting amplifier unit U1 is used as the second terminal of the inverting amplifier module 12.
  • the inverting amplifying unit U1 can be realized by using an inverting amplifier or a broadband amplifier, but considering that the broadband amplifier will not introduce new poles into the circuit, it is more conducive to maintaining the cancellation module 11, the inverting amplifier module 12, the current integration module 14, and the photosensitivity.
  • the stability of the sample-and-hold loop formed by the diode 15 is, therefore, a broadband amplifier is preferred as the inverting amplifying unit U1 in this embodiment.
  • a broadband amplifier is preferred as the inverting amplifying unit U1 in this embodiment.
  • the entire sample-and-hold loop can form a closed-loop negative feedback, which can make the bandwidth of the wideband amplifier much larger than the entire sample-and-hold loop.
  • the bandwidth of the broadband amplifier is preferably at least twice the gain-bandwidth product of the sample-and-hold loop.
  • the current integration module 14 is used to convert the input current into a voltage and integrate and amplify it.
  • the current integration module 14 may include a transconductance amplifier U3 and an integration capacitor Cf.
  • the input terminal of the transconductance amplifier U3 is connected to one end of the integration capacitor Cf as the first terminal of the current integration module 14, and the output terminal of the transconductance amplifier U3 is connected to the other end of the integration capacitor Cf as the current integration.
  • the function of the reset module 13 is to reset the integration capacitor Cf, so that the potentials of the two plates of the integration capacitor Cf are equal.
  • the reset module 13 may include an error amplifier U2 and a second control switch S2.
  • a forward signal input terminal of the error amplifier U2 may be used as a first input terminal of the reset module 13; a reverse signal input of the error amplifier U2
  • the terminal can be used as the second input terminal of the reset module 13; the output terminal of the error amplifier U2 is connected to one end of the second control switch S2, and the other end of the second control switch S2 is used as the output terminal of the reset module 13.
  • the voltage of the forward signal input terminal of the error amplifier U2 is equal to the voltage of the reverse signal input terminal, that is, the voltage of the first input terminal of the reset module 13 and the voltage of the second input terminal of the reset module 13 are equal to each other.
  • This reference voltage is Vcm.
  • the reset loop formed by the reset module 13 and the current integration module 14 forms a differential input and single-ended output unity gain amplifying unit during operation, so that the voltage at the output terminal of the error amplifier U2 and the two input terminals (that is, The voltages at the forward signal input terminal and the reverse signal input terminal are equal, that is, the potentials of the two plates of the integration capacitor Cf are equal (both equal to the reference voltage Vcm), so that the purpose of resetting the integration capacitor Cf is achieved.
  • This resetting method avoids connecting the switch between the two ends of the integrating capacitor Cf in the prior art, and using the on-off of the switch to reset the integrating capacitor Cf, thereby reducing the non-linearity brought by the switch. And noise problems, so that the linearity of the integration is improved, and the problem of charge injection is alleviated.
  • this embodiment may further include a third control switch S3, and the second end of the cancellation module 11 may be respectively connected to the first end of the current integration module 14 and the reset module 13 through the third control switch S3. Output.
  • the third control switch S3 In the current sampling phase, the reset phase, and the current integration phase, the third control switch S3 is turned on to the second terminal of the cancellation module 11, the first terminal of the current integration module 14, and the output terminal of the reset module 13, and its existence is equivalent to one wire. .
  • the third control switch S3 can be turned off, so that the current integration module 14 does not have any signal input, so as to improve ADC sampling. Accuracy.
  • the first control switch S1 When entering the current sampling phase (as shown in Figure 2), the first control switch S1 can be closed and the second control switch S2 can be opened. At this time, the cancellation module 11, the inverting amplifier module 12, and the current integration module in the circuit 14 and the photodiode 15 constitute a sample-and-hold loop. After the completion of the loop, the voltage across the transconductance amplifier U3 does not change. At this time, no current flows through the integration capacitor Cf and the parasitic capacitance Cp of the photodiode 15.
  • the inverting amplifier module 12 In order to cancel the DC component Ipd in the background photocurrent of the photodiode 15, the inverting amplifier module 12 inverts the voltage output by the transconductance amplifier U3, and uses the inverted voltage as a bias voltage to control the sampling electronic switch M0. Terminal, the sampling electronic switch M0 is triggered to output a current Id, and the current Id is equal to the DC component Ipd in the background photocurrent of the photodiode 15. At this time, the sampling capacitor Ch is equivalent to sampling the DC component Ipd in the background photocurrent and converting it into its own voltage. It is worth mentioning that, because the current Id and the DC component Ipd are equal and cancel each other out, in other phases, the current Id and the DC component Ipd are not input into the current integration module 14.
  • the inverting amplifier module 12 is connected to the control terminal of the sampling electronic switch M0, which can provide a wider range of voltage for the control terminal of the sampling electronic switch M0 (the voltage can be changed from 0) In this way, in the current sampling phase, the voltage of the control terminal of the sampling electronic switch M0 can be changed in a wider range. Since the voltage of the control terminal of the sampling electronic switch M0 can be changed from 0, if the output current Id of the sampling electronic switch M0 needs to be increased, the embodiment of the present application can apply a smaller voltage to the control terminal of the sampling electronic switch M0.
  • the purpose is achieved, but in the prior art, the purpose can only be achieved by selecting a larger size (larger width-to-length ratio) sampling electronic switch M0 and increasing the transconductance of the sampling electronic switch M0. Since the larger the transconductance of the sampling electronic switch M0 is, the larger the noise it brings. Therefore, compared with the prior art, a smaller sampling electronic switch M0 can be used in this embodiment, which is beneficial to reduce the sampling and holding loop. noise.
  • the first control switch S1 can be opened and the second control switch S2 can be closed, so that the circuit enters a reset phase (as shown in FIG. 3).
  • the reset module 13, the current integration module 14, and the photodiode 15 in the circuit constitute a reset loop.
  • the access of the parasitic capacitance Cp of the photodiode 15 may affect the stability of the loop. Therefore, when the loop stability is affected, the third control switch S3 may be turned off, thereby turning off The photodiode 15 is connected to the reset module 13 and the current integration module 14. In this way, the reset module 13 and the current integration module 14 form a reset loop.
  • the error amplifier U2 and the current integration module 14 constitute a unity gain amplifying unit, that is, the voltage at the output terminal of the error amplifier U2 is equal to the voltage at the two input terminals, which are both equal to the reference voltage Vcm.
  • the potentials of the two plates of the integration capacitor Cf are also equal (both equal to the reference voltage Vcm), so that the purpose of resetting the integration capacitor Cf is achieved.
  • the circuit can perform a current integration phase by turning off the first control switch S1 and the second control switch S2 (as shown in FIG. 4).
  • the direct current component in the background photocurrent of the photodiode 15 is cancelled by the current Id output by the sampling electronic switch M0. Therefore, in this phase, only the high-frequency component in the background photocurrent of the photodiode 15 and the photoelectric signal from the light-emitting diode (LED) in the distance sensor transmitting section enter the integrating capacitor Cf.
  • the high-frequency component of the background photocurrent when the light-emitting diode emits light, the high-frequency component of the background photocurrent and the photoelectric signal of the light-emitting diode are integrated once, and then when the light-emitting diode is off, The high-frequency component in the background photocurrent is integrated once, and then the result of the two integrations is subtracted in the digital domain to obtain the photoelectric signal of the light-emitting diode.
  • the current integration phase in this embodiment may be performed by using a timing chart shown in FIG. 5.
  • sh is a control signal applied to the first control switch S1 (when sh is a high level signal, the first control switch is closed)
  • rst is a control signal applied to the second control switch S2 (when rst is a high level signal, the second control Switch S2 is closed)
  • led_clk is a control signal applied to the light-emitting diode (when led_clk is a high-level signal, the light-emitting diode is illuminated)
  • oe is a control signal applied to the third control switch S3 (when oe is a high-level signal, the third control switch is turned off On)
  • dout is the output signal of the analog-to-digital conversion module.
  • the second end of the current integration module 14 is used to connect to an ADC.
  • the ADC can sample the value integrated by the current integration module 14 twice, and perform analog-to-digital conversion on
  • the timing diagram is mainly divided into two phases, that is, sh is a high level signal phase, and sh is a low electrical signal phase.
  • sh is a high-level signal phase
  • the circuit is in the current sampling phase, and it samples the DC component Ipd in the background photocurrent of the photodiode 15.
  • sh is a low electrical signal phase
  • the circuit enters the reset phase and the integration capacitor Cf is reset (the integration capacitor Cf is two
  • the potential of each plate is the reference voltage Vcm).
  • the circuit enters the current integration phase, the light-emitting diode emits light, and the current integration module 14 performs The first integration (that is, the position corresponding to A in the figure).
  • the light-emitting diode is turned off, and the third control switch S3 is turned off (as shown in Figure 6 (Shown), the circuit enters the analog-to-digital conversion phase, and the ADC performs the first sampling, that is, reads the value integrated by the current integration module 14 for the first time, and performs analog-to-digital conversion on the value.
  • the ADC outputs the value after the first analog-to-digital conversion (that is, D0).
  • the third control switch S3 is turned off, so that the current integration module 14 does not have any signal input, and the output state is maintained for sampling by the ADC, which is beneficial to ensure the accuracy of the sampling.
  • the circuit After that, when oe becomes a low electric signal, rst changes from a low level signal to a high level signal, the circuit enters the reset phase again, and the integration capacitor Cf is reset. After resetting, change rst from high level signal to low level signal, and keep led_clk and oe as low level signal. At this time, the circuit enters the current integration phase again, and the current integration module 14 performs the second integration (that is, the corresponding B in the figure). position). Since the light-emitting diode tube is turned off at this time, the current integration module 14 only has a high-frequency component input in the background photocurrent of the photodiode 15; therefore, the second integration is only to integrate the high-frequency component.
  • the circuit After the second integration, oe changes from low level to high level again, the circuit enters the analog-to-digital conversion phase again, the ADC performs the second sampling, that is, reads the value of the second integration of the current integration module 14, and Value for analog-to-digital conversion. When oe is pulled low, the ADC outputs the value after the second analog-to-digital conversion (that is, D1).
  • the value D0 after the first analog-to-digital conversion is subtracted from the value D1 after the second analog-to-digital conversion to obtain the photoelectric signal when the light emitting diode emits light.
  • this embodiment firstly connects a reset module between the first end and the second end of the current integration module, and the reset module and the current integration module form a unity gain amplifying unit.
  • the voltage at the output end is equal to the voltage at its two input ends, that is, the voltage at the first end and the second end of the current integration module are equal (both equal to the reference voltage), so as to reset the current integration module.
  • This reset method avoids the process of connecting a switch between the first end and the second end of the current integration module in the prior art and using the switch to reset the current integration module, thereby reducing the non-compliance brought by the switch. Linearity and noise issues.
  • only one current integration module is set, which simplifies the structure of the distance sensor, and also helps to reduce the area of the front end of the distance sensor and reduce the cost.
  • a second embodiment of the present application relates to a distance sensor receiving an analog front-end circuit.
  • the second embodiment is a further improvement based on the first embodiment.
  • the main improvement is that the second embodiment provides an implementation manner of a transconductance amplifier, a broadband amplifier, and an error amplifier.
  • the transconductance amplifier U3 may specifically include: a first electronic switch M1 and a second electronic switch M2, wherein a control terminal of the first electronic switch M1 is used to input a first bias voltage (Vbp1);
  • the input terminal of an electronic switch M1 is connected to the power supply VDD terminal;
  • the output terminal of the first electronic switch M1 is connected to the input terminal of the second electronic switch M2 as the output terminal (Vout1) of the transconductance amplifier U3;
  • the second electronic switch M2 The control terminal is used as the input terminal (Vin1) of the transconductance amplifier U3; the output terminal of the second electronic switch M2 is grounded.
  • the broadband amplifier may specifically include a third electronic switch M3 and a fourth electronic switch M4, wherein an input terminal of the third electronic switch M3 is connected to a power source VDD terminal; a control terminal and an output terminal of the third electronic switch M3 And the input terminal of the fourth electronic switch M4 is connected together as the output terminal (Vout2) of the broadband amplifier; the control terminal of the fourth electronic switch M4 is used as the input terminal (Vin2) of the broadband amplifier; the output terminal of the fourth electronic switch M4 is grounded .
  • the error amplifier U2 specifically includes a fifth electronic switch M5, a sixth electronic switch M6, a seventh electronic switch M7, an eighth electronic switch M8, and a ninth electronic switch M9.
  • the input of the fifth electronic switch M5 The terminal of the fifth electronic switch M5 is used to input the second bias voltage (Vbp2); the output of the fifth electronic switch M5 is connected to the input of the sixth electronic switch M6 and the seventh electronic switch M7, respectively.
  • the input terminal of the sixth electronic switch M6 is used as the forward signal input terminal (Vin3 + ) of the error amplifier U2.
  • the output terminal of the sixth electronic switch M6 is connected to the input terminal, the control terminal and the eighth electronic switch M8, respectively.
  • the first electronic switch M1, the third electronic switch M3, the fifth electronic switch M5, the sixth electronic switch M6, and the seventh electronic switch M7 are PMOS tubes
  • the fourth electronic switch M4, the eighth electronic switch M8 and the ninth electronic switch M9 are illustrated by using NMOS tubes as an example.
  • the first electronic switch M1, the second electronic switch M2, the third electronic switch M3, ..., and the ninth electronic switch M9 can all be composed of a field effect transistor or other electron tube.
  • the field effect transistor can be a PMOS tube or an NMOS. tube. .
  • transconductance amplifier wideband amplifier
  • error amplifier are not limited to those provided in this embodiment.
  • transconductance amplifiers, wideband amplifiers, and error amplifiers implemented in other ways may be selected according to implementation needs. There are no restrictions on this.
  • this embodiment provides an implementation manner of a transconductance amplifier, a broadband amplifier, and an error amplifier.
  • a third embodiment of the present application relates to a distance sensor.
  • the distance sensor includes a transmitting section 101 and a receiving section 102; the transmitting section 101 includes a light emitting diode 1011 and a driving circuit 1012 for driving the light emitting diode; and the receiving section 102 includes the first embodiment or the second embodiment.
  • the distance sensor according to the embodiment receives an analog front-end circuit 1021 and an analog-to-digital converter 1022.
  • the input end of the analog-to-digital converter 1022 is connected to the second end of the current integration module in the distance sensor receiving analog front-end circuit 1021.
  • this embodiment firstly connects a reset module between the first end and the second end of the current integration module, and the reset module and the current integration module constitute a unity gain amplifying unit.
  • the voltage at the output end is equal to the voltage at its two input ends, that is, the voltage at the first end and the second end of the current integration module are equal (both equal to the reference voltage), so as to reset the current integration module.
  • This reset method avoids the process of connecting a switch between the first end and the second end of the current integration module in the prior art and using the switch to reset the current integration module, thereby reducing the non-compliance brought by the switch. Linearity and noise issues.
  • only one current integration module is provided, which simplifies the structure of the distance sensor and also helps to reduce the area of the front end of the distance sensor and reduce the cost.

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Abstract

提供了一种距离传感器接收模拟前端电路及距离传感器。该前端电路包括：光敏二极管(15)、电流积分模块(14)、反相放大模块(12)、复位模块（13）及抵消模块(11)；抵消模块(11)的第一端连接电源端；抵消模块(11)的第二端分别连接光敏二极管(15)、电流积分模块(14)的第一端及复位模块（13）的输出端；抵消模块(11)的第三端连接反相放大模块(12)的第一端；反相放大模块(12)的第二端分别连接电流积分模块(14)的第二端及复位模块（13）的第一输入端，复位模块（13）的第二输入端输入参考电压；其中，复位模块（13）的第一输入端的电压与所述复位模块（13）的第二输入端的电压相等，且复位模块（13）与电流积分模块(14)构成一单位增益放大单元。上述前端电路及距离传感器能够解决解决现有技术中芯片面积大、噪声大的问题。

Description

一种距离传感器接收模拟前端电路及距离传感器 技术领域
本申请涉及距离传感器技术领域，特别涉及一种距离传感器接收模拟前端电路及距离传感器。
背景技术
距离传感器通常分为电容式和光学式两大类。其中，光学式距离传感器需要采用低噪声电流-电压积分器将接受到的光电电流进行积分放大并转换成电压，最后由后端的模数转换器转换成数字信号进行处理。为了抑制背景光电流对信号的干扰，现有技术中通常会采用双积分积分器，即先对包含背景光电流信号和有用信号的信号进行积分，再对仅包含背景光电流信号的信号进行积分，最后利用模数转换器对二者的差模信号进行转换。这种处理方法存在以下缺点：首先，需要用两个大电容分别存储两次积分的模拟信号，这会使芯片的面积变得非常大；其次，由于两个电容需要以“乒乓”的方式工作，因此两个电容都会采样较大的开关噪声，尤其是一个放大器、两个电容这种形式的积分器，该问题更严重。
发明内容
本申请部分实施例的目的在于提供一种距离传感器接收模拟前端电路及距离传感器，以解决现有技术中芯片面积大、噪声大的问题。
本申请实施例提供了一种距离传感器接收模拟前端电路，包括：光敏二 极管、电流积分模块、反相放大模块、用于对所述电流积分模块进行复位的复位模块及用于抵消所述光敏二极管背景光电流中的直流分量的抵消模块；所述抵消模块的第一端连接电源端；所述抵消模块的第二端分别连接所述光敏二极管、所述电流积分模块的第一端及所述复位模块的输出端；所述抵消模块的第三端连接所述反相放大模块的第一端；所述反相放大模块的第二端分别连接所述电流积分模块的第二端及所述复位模块的第一输入端，所述复位模块的第二输入端输入参考电压；其中，所述复位模块的第一输入端的电压与所述复位模块的第二输入端的电压相等，且所述复位模块与所述电流积分模块构成一单位增益放大单元。
本申请实施例还提供了一种距离传感器，包括发射部及接收部；所述发射部包括发光二极管及用于驱动所述发光二极管的驱动电路；所述接收部包括如上所述的距离传感器接收模拟前端电路及模数转换器；所述模数转换器连接至电流积分模块的第二端。
本申请实施例相对于现有技术而言，首先，在电流积分模块的第一端及第二端之间连接复位模块，该复位模块与电流积分模块构成一单位增益放大单元，这样，复位模块的输出端的电压就与其两个输入端的电压相等，即电流积分模块的第一端与第二端的电压相等(都等于该参考电压)，从而达到对电流积分模块进行复位的目的。这种复位方式，避免了现有技术中通过在电流积分模块的第一端及第二端之间连接开关，并利用该开关对电流积分模块进行复位的过程，从而降低了开关带来的非线性和噪声问题。其次，只设置一个电流积分模块，简化了距离传感器的结构，也利于减少距离传感器接收前端的面积并降低成本。
另外，所述抵消模块包括采样电容及采样电子开关；所述采样电子开关的输入端与所述采样电容的一端连接在一起，作为所述抵消模块的所述第一端；所述采样电子开关的输出端作为所述抵消模块的所述第二端；所述采样电子开关的控制端与所述采样电容的另一端连接在一起，作为所述抵消模块的所述第三端。提供了抵消模块的一种具体结构。在采样电子开关的控制端连接反相放大模块，该反相放大模块可为采样电子开关的控制端提供更宽范围的电压(可从0开始)，这样，在采样保持阶段，采样电子开关的控制端的电压就可在更宽范围内变化。同时，由于采样电子开关的控制端的电压可从0开始变化，因此，若需要增大采样电子开关的输出电流，本申请实施方式即可通过在采样电子开关的控制端施加更小的电压达到目的，而现有技术中只能通过设置更大尺寸(宽长比大)的采样电子开关，增大采样电子开关的跨导达到目的。而采样电子开关的跨导越大，所带来的噪声就越大，因此，相对于现有技术，本申请实施方式可设置更小尺寸的采样是电子开关，从而降低其带来的噪声。
另外，所述电流积分模块包括跨导放大器及积分电容；所述跨导放大器的输入端与所述积分电容的一端连接在一起，作为所述电流积分模块的所述第一端，所述跨导放大器的输出端与所述积分电容的另一端连接在一起，作为所述电流积分模块的所述第二端。提供电流积分模块的一种具体结构。
另外，所述跨导放大器具体包括：第一电子开关及第二电子开关；所述第一电子开关的控制端输入第一偏置电压，所述第一电子开关的输入端连接所述电源端，所述第一电子开关的输出端与所述第二电子开关的输入端连接在一起，作为所述跨导放大器的所述输出端，所述第二电子开关的控制端作为所述跨导放大器的所述输入端，所述第二电子开关的输出端接地。提供跨导放大器 的一种具体结构。
另外，所述反相放大模块包括反相放大单元及第一控制开关；所述第一控制开关的一端作为所述反相放大模块的所述第一端，所述第一控制开关的另一端连接所述反相放大单元的输出端，所述反相放大单元的输入端作为所述反相放大模块的所述第二端。提供反相放大模块的一种具体结构。
另外，所述反相放大单元为反相放大器或宽带放大器。提供反相放大单元的两种实现方式。
另外，所述宽带放大器的带度至少为采样保持环路的增益带宽积的2倍；其中，所述采样保持环路为所述抵消模块、所述反相放大模块、所述电流积分模块及所述光敏二极管组成的环路。
另外，所述宽带放大器具体包括：第三电子开关及第四电子开关；所述第三电子开关的输入端连接所述电源端，所述第三电子开关的控制端、输出端及所述第四电子开关的输入端连接在一起，作为所述宽带放大器的输出端，所述第四电子开关的控制端作为所述宽带放大器的输入端，所述第四电子开关的输出端接地。提供宽带放大器的一种具体结构。
另外，所述复位模块包括误差放大器及第二控制开关；所述误差放大器的正向信号输入端作为所述复位模块的所述第一输入端；所述误差放大器的反向信号输入端作为所述复位模块的所述第二输入端；所述误差放大器的输出端连接所述第二控制开关的一端，所述第二控制开关的另一端作为所述复位模块的所述输出端。提供复位模块的一种具体结构。
另外，所述误差放大器具体包括第五电子开关、第六电子开关、第七电子开关、第八电子开关及第九电子开关；所述第五电子开关的输入端连接所述 电源端，所述第五电子开关的控制端输入第二偏置电压，所述第五电子开关的输出端分别连接所述第六电子开关的输入端及所述第七电子开关的输入端；所述第六电子开关的控制端作为所述误差放大器的所述正向信号输入端，所述第六电子开关的输出端分别连接所述第八电子开关的输入端、控制端及所述九电子开关的控制端；所述第七电子开关的控制端作为所述误差放大器的所述反向信号输入端，所述第七电子开关的输出端与所述第九电子开关的输入端连接在一起，作为所述误差放大器的所述输出端，所述第八电子开关的控制端连接所述第九电子开关的控制端，所述第八电子开关的输出端及所述第九电子开关的输出端均接地。提供误差放大器的一种具体结构。
所述电路还包括第三控制开关；所述抵消模块的所述第二端通过所述第三控制开关连接所述电流积分模块的所述第一端及所述复位模块的所述输出端。
附图说明
一个或多个实施例通过与之对应的附图中的图片进行示例性说明，这些示例性说明并不构成对实施例的限定，附图中具有相同参考数字标号的元件表示为类似的元件，除非有特别申明，附图中的图不构成比例限制。
图1是根据本申请第一实施例的距离传感器接收模拟前端电路的结构示意图；
图2是根据本申请第一实施例的电流采样相位的结构示意图；
图3是根据本申请第一实施例的复位相位的结构示意图；
图4是根据本申请第一实施例的电流积分相位的结构示意图；
图5是根据本申请第一实施例的工作时序图；
图6是根据本申请第一实施例的模数转换相位的结构示意图；
图7是根据本申请第二实施例的跨导放大器的结构示意图；
图8是根据本申请第二实施例的宽带放大器的结构示意图；
图9是根据本申请第二实施例的误差放大器的结构示意图；
图10是根据本申请第三实施例的距离传感器的结构示意图。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本申请部分实施例进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
本申请第一实施例涉及一种距离传感器接收模拟前端电路。如图1所示，该电路包括抵消模块11、反相放大模块12、复位模块13、电流积分模块14及光敏二极管(PD)15，其中，电容Cp为光敏二极管15内部的寄生电容。抵消模块11的第一端连接电源VDD端；抵消模块11的第二端分别连接光敏二极管15的阴极、复位模块13的输出端及电流积分模块14的第一端，光敏二极管15的阳极接地VSS；抵消模块11的第三端连接反相放大模块12的第一端；反相放大模块12的第二端分别连接电流积分模块14的第二端及复位模块13的第一输入端，复位模块13的第二输入端输入参考电压Vcm。
具体而言，本实施例中，抵消模块11输出的电流Id可用于抵消光敏二极管15背景光电流中的直接分量Ipd。在一个例子中，该抵消模块11可包括采样电容Ch及采样电子开关M0。其中，采样电子开关M0的输入端与采样电容Ch的一端连接在一起，作为该抵消模块11的第一端；采样电子开关M0的 输出端作为该抵消模块11的第二端；采样电子开关M0的控制端与采样电容Ch的另一端连接在一起，作为该抵消模块11的第三端。值得一提的是，图1中是以采样电子开关M0是PMOS管为例进行示意的，但并不以此为限，在实际应用中，也可采用NMOS管或其它电子管。
反相放大模块12的主要作用是对输入的电压(即反相放大模块12的第二端的电压)取反，并将取反后的电压作为偏置电压提供给采样电子开关M0，从而触发采样电子开关M0向光敏二极管15输出与光敏二极管15背景光电流中的直流分量Ipd大小相等的电流Id，以抵消该直流分量Ipd。在实际应用中，反相放大模块12可包括反相放大单元U1及第一控制开关S1；其中，第一控制开关S1的一端作为该反相放大模块12的第一端；第一控制开关S1的另一端连接反相放大单元U1的输出端，反相放大单元U1的输入端作为反相放大模块12的第二端。该反相放大单元U1可选用反相放大器或宽带放大器实现，但考虑宽带放大器不会为电路引入新的极点，更有利于保持由抵消模块11、反相放大模块12、电流积分模块14及光敏二极管15组成的采样保持环路的稳定性，因此，本实施例优选宽带放大器作为反相放大单元U1。值得一提的是，在选用宽带放大器作为反相放大单元U1时，为保证宽带放大器的加入，能使整个采样保持环路构成闭环负反馈，可使宽带放大器的带宽远远大于整个采样保持环路的增益带宽积。本实施例优选宽带放大器的带宽至少为采样保持环路的增益带宽积的2倍。
电流积分模块14用于将输入的电流转换成电压并积分放大。在一个例子中，该电流积分模块14可包括跨导放大器U3及积分电容Cf。其中，跨导放大器U3的输入端与积分电容Cf的一端连接在一起，作为电流积分模块14的第 一端，跨导放大器U3的输出端与积分电容Cf的另一端连接在一起，作为电流积分模块14的第二端。
复位模块13的作用是复位积分电容Cf，使积分电容Cf两个极板的电位相等。本实施例中，复位模块13可包括误差放大器U2及第二控制开关S2；其中，误差放大器U2的正向信号输入端可作为复位模块13的第一输入端；误差放大器U2的反向信号输入端可作为复位模块13的第二输入端；误差放大器U2的输出端连接第二控制开关S2的一端，第二控制开关S2的另一端作为复位模块13的输出端。值得一提的是，误差放大器U2的正向信号输入端的电压与反向信号输入端的电压相等，即，复位模块13的第一输入端的电压与复位模块13的第二输入端的电压相等，都为该参考电压Vcm。
本实施例中，复位模块13与电流积分模块14构成的复位环路在工作时，构成一差分输入、单端输出的单位增益放大单元，使得误差放大器U2输出端的电压与两个输入端(即正向信号输入端、反向信号输入端)的电压相等，即积分电容Cf两个极板的电位相等(都等于参考电压Vcm)，从而达到了对积分电容Cf进行复位的目的。这种复位方式，避免了现有技术中通过在积分电容Cf的两端之间连接开关，并利用该开关的通断实现对积分电容Cf进行复位的过程，从而降低了开关带来的非线性和噪声问题，使得积分的线性度得到提高，电荷注入问题得到缓解。
另外，值得一提的是，本实施例还可包括第三控制开关S3，抵消模块11的第二端可通过该第三控制开关S3分别连接电流积分模块14的第一端及复位模块13的输出端。在电流采样相位、复位相位及电流积分相位中，第三控制开关S3导通抵消模块11的第二端与电流积分模块14的第一端及复位模块13的 输出端，其存在相当于一条导线。而在模数转换相位中，在ADC(Analog-to-Digital Converter，模数转换器)进行采样时，可断开第三控制开关S3，使得电流积分模块14没有任何信号输入，以提高ADC采样的准确率。
下面将对距离传感器接收模拟前端电路的各个相位进行介绍：
在进入电流采样相位(如图2所示)时，可闭合第一控制开关S1，并断开第二控制开关S2，此时，电路中的抵消模块11、反相放大模块12、电流积分模块14及光敏二极管15构成采样保持环路。该环路建立完成后，跨导放大器U3两端的电压不在变化，此时，没有电流流过积分电容Cf及光敏二极管15的寄生电容Cp。为了抵消光敏二极管15背景光电流中的直流分量Ipd，反相放大模块12对跨导放大器U3输出的电压取反，并将取反后的电压作为偏置电压，施加于采样电子开关M0的控制端，触发采样电子开关M0输出电流Id，且该电流Id与光敏二极管15背景光电流中的直流分量Ipd相等。此时采样电容Ch相当于采样了背景光电流中的直流分量Ipd，并将其转换为自身的电压。值得一提的是，由于电流Id与直流分量Ipd相等，相互抵消，因此，在接下来的其它相位中，电流Id与直流分量Ipd都不会输入电流积分模块14中。
值得一提的是，在采样电子开关M0的控制端连接反相放大模块12，该反相放大模块12可为采样电子开关M0的控制端提供更宽范围的电压(电压可从0开始变化)，这样，在电流采样相位，采样电子开关M0的控制端的电压就可在更宽范围内变化。由于采样电子开关M0的控制端的电压可从0开始变化，因此，若需要增大采样电子开关M0的输出电流Id，本申请实施方式就可通过在采样电子开关M0的控制端施加更小的电压达到目的，而现有技术中只能通过选用更大尺寸(宽长比大)的采样电子开关M0，增大采样电子开关M0 的跨导达到目的。由于采样电子开关M0的跨导越大，所带来的噪声就越大，因此，相对于现有技术，本实施例可选用更小尺寸的采样电子开关M0，有利于降低采样保持环路的噪声。
接着，可断开第一控制开关S1，并闭合第二控制开关S2，使电路进入复位相位(如图3所示)。此时，电路中的复位模块13、电流积分模块14及光敏二极管15构成复位环路。值得一提的是，光敏二极管15的寄生电容Cp的接入可会影响环路的稳定性，因此，在环路稳定性受到影响的情况下，也可断开第三控制开关S3，从而断开光敏二极管15与复位模块13及电流积分模块14的连接，这样，复位模块13与电流积分模块14就构成了复位环路。本相位中，误差放大器U2与电流积分模块14构成一单位增益放大单元，即误差放大器U2输出端的电压与两个输入端的电压相等，都等于参考电压Vcm。此时，积分电容Cf两个极板的电位也分别相等(都等于参考电压Vcm)，从而达到了对积分电容Cf进行复位的目的。
随后，可通过断开第一控制开关S1及第二控制开关S2，使电路进行电流积分相位(如图4所示)。如上文所述，由于光敏二极管15背景光电流中的直流成分被采样电子开关M0输出的电流Id抵消。因此，本相位中，仅有光敏二极管15背景光电流中的高频分量及距离传感器发射部中的发光二极管(LED)发出的光电信号进入到积分电容Cf中。为了进一步消除该背景光电流中的高频分量，本实施例在发光二极管发光时，可对背景光电流中的高频分量及发光二极管的光电信号进行一次积分，然后在发光二极管熄灭时，再对背景光电流中的高频分量进行一次积分，之后在数字域将两次积分的结果相减，从而得到发光二极管的光电信号。
具体而言，本实施例的电流积分相位可采用如图5所示时序图进行。其中，sh为施加至第一控制开关S1的控制信号(sh为高平信号时，第一控制开关闭合)，rst为施加至第二控制开关S2的控制信号(rst为高平信号时，第二控制开关S2闭合)、led_clk为施加至发光二极管的控制信号(led_clk为高平信号时，发光二极管发光)、oe为施加至第三控制开关S3的控制信号(oe为高平信号时，第三控制开关断开)、dout为模数转换模块的输出信号。本实施例中，电流积分模块14的第二端用于连接ADC，该ADC可采样电流积分模块14两次积分的值，并对采样的值进行模数转换。
可以看出，该时序图主要分成两个阶段，即sh为高平信号阶段，以及sh为低电信号阶段。sh为高平信号阶段时，电路处于电流采样相位，其采样的是光敏二极管15背景光电流中的直流分量Ipd。sh为低电信号阶段时，在一个周期T内：先使rst为高平信号，并保持led_clk、oe为低电平信号，此时，电路进入复位相位，积分电容Cf被复位(积分电容Cf两个极板的电位都为参考的电压Vcm)。接着，保持oe为低电平信号，并使rst由高平信号变为低平信号，led_clk由低平信号变为高平信号，此时，电路进入电流积分相位，发光二极管发光，电流积分模块14进行第一次积分(即图中A对应的位置)。然后，保持rst为低平信号，并使led_clk由高平信号变为低平信号，oe由低电平信号变为高平信号，此时，发光二极管熄灭，第三控制开关S3断开(如图6所示)，电路进入模数转换相位，ADC进行第一次采样，即读取电流积分模块14第一次积分的值，并将该值进行模数转换。当oe拉低时(下降沿)，ADC输出第一次模数转换后的值(即D0)。在ADC采样时，断开第三控制开关S3，使得电流积分模块14没有任何信号输入，保持输出状态给ADC进行采样，有利于 保证采样的准确性。
之后，oe变为低电信号时，rst由低平信号变化高平信号，电路再次进入复位相位，积分电容Cf被复位。复位过后，将rst由高平信号变为低平信号，并保持led_clk及oe为低平信号，此时，电路再次进入电流积分相位，电流积分模块14进行第二次积分(即图中B对应的位置)。由于此时发光二管管熄灭，电流积分模块14仅有光敏二极管15背景光电流中的高频分量输入，因此，第二次积分仅是对该高频分量进行积分。第二次积分后，oe再次由低电平变为高电平，电路再次进入模数转换相位，ADC进行第二次采样，即读取电流积分模块14第二次积分的值，并将该值进行模数转换。当oe拉低时，ADC输出第二次模数转换后的值(即D1)。
用第一次模数转换后的值D0减去第二次模数转换后的值D1，即可得到发光二极管的发光时的光电信号。
通过图5可以看出，在进行数次模数转换之前，本实施例只需要进行一次电流采样，在进行模数转换时，每两次转换的值相减才能得到一个所需的信号(即发光二极管的发光时的光电信号)。
本实施例相对于现有技术而言，首先，在电流积分模块的第一端及第二端之间连接复位模块，该复位模块与电流积分模块构成一单位增益放大单元，这样，复位模块的输出端的电压就与其两个输入端的电压相等，即电流积分模块的第一端与第二端的电压相等(都等于该参考电压)，从而达到对电流积分模块进行复位的目的。这种复位方式，避免了现有技术中通过在电流积分模块的第一端及第二端之间连接开关，并利用该开关对电流积分模块进行复位的过程，从而降低了开关带来的非线性和噪声问题。其次，只设置一个电流积分模 块，简化了距离传感器的结构，也利于减少距离传感器接收前端的面积并降低成本。
本申请的第二实施例涉及一种距离传感器接收模拟前端电路。第二实施例是在第一实施例的基础上做的进一步改进，主要改进之处在于，第二实施例提供了一种跨导放大器、宽带放大器及误差放大器的实现方式。
如图7所示，该跨导放大器U3可具体包括：第一电子开关M1及第二电子开关M2，其中，第一电子开关M1的控制端用于输入第一偏置电压(Vbp1)；第一电子开关M1的输入端连接电源VDD端；第一电子开关M1的输出端与第二电子开关M2的输入端连接在一起，作为跨导放大器U3的输出端(Vout1)；第二电子开关M2的控制端作为跨导放大器U3的输入端(Vin1)；第二电子开关M2的输出端接地。
如图8所示，宽带放大器可具体包括：第三电子开关M3及第四电子开关M4，其中，第三电子开关M3的输入端连接电源VDD端；第三电子开关M3的控制端、输出端及第四电子开关M4的输入端连接在一起，作为宽带放大器的输出端(Vout2)；第四电子开关M4的控制端作为宽带放大器的输入端(Vin2)；第四电子开关M4的输出端接地。
如图9所示，误差放大器U2具体包括第五电子开关M5、第六电子开关M6、第七电子开关M7、第八电子开关M8及第九电子开关M9；其中，第五电子开关M5的输入端连接电源VDD端；第五电子开关M5的控制端用于输入第二偏置电压(Vbp2)；第五电子开关M5的输出端分别连接第六电子开关M6的输入端及第七电子开关M7的输入端；第六电子开关M6的控制端，作为误 差放大器U2的正向信号输入端(Vin3 +)，第六电子开关M6的输出端分别连接第八电子开关M8的输入端、控制端及九电子开关M9的控制端；第七电子开关M7的控制端，作为误差放大器U2的反向信号输入端(Vin3 -)；第七电子开关M7的输出端与第九电子开关M9的输入端连接在一起，作为误差放大器U2的输出端(Vout3)；第八电子开关M8的控制端连接第九电子开关M9的控制端，第八电子开关M8的输出端及第九电子开关M9的输出端均接地。
需要说明的是，图7至9中是以第一电子开关M1、第三电子开关M3、第五电子开关M5、第六电子开关M6及第七电子开关M7是PMOS管，第二电子开关M2、第四电子开关M4、第八电子开关M8及第九电子开关M9是NMOS管为例进行示意的。但实际应用中，第一电子开关M1、第二电子开关M2、第三电子开关M3……第九电子开关M9，均可由场效应晶体管或其它电子管构成，该场效应晶体管可以是PMOS管或NMOS管。。
此外，跨导放大器、宽带放大器及误差放大器的实现方式不限于本实施例所提供的，在实际应用中，可根据实现需要选用其它方式实现的跨导放大器、宽带放大器及误差放大器，本实施例对此不做限制。
本实施方式相对于第一实施方式而言，提供了一种跨导放大器、宽带放大器及误差放大器的实现方式。
本申请的第三实施方式涉及一种距离传感器。如图10所示，该距离传感器包括发射部101及接收部102；该发射部101包括发光二极管1011及用于驱动该发光二极管的驱动电路1012；接收部102包括如第一实施方式或第二实施方式所述的距离传感器接收模拟前端电路1021及模数转换器1022，该模数转 换器1022的输入端连接距离传感器接收模拟前端电路1021中的电流积分模块的第二端。
本实施方式相对于现有技术而言，首先，在电流积分模块的第一端及第二端之间连接复位模块，该复位模块与电流积分模块构成一单位增益放大单元，这样，复位模块的输出端的电压就与其两个输入端的电压相等，即电流积分模块的第一端与第二端的电压相等(都等于该参考电压)，从而达到对电流积分模块进行复位的目的。这种复位方式，避免了现有技术中通过在电流积分模块的第一端及第二端之间连接开关，并利用该开关对电流积分模块进行复位的过程，从而降低了开关带来的非线性和噪声问题。其次，只设置一个电流积分模块，简化了距离传感器的结构，也利于减少距离传感器接收前端的面积并降低成本。
本领域的普通技术人员可以理解，上述各实施例是实现本申请的具体实施例，而在实际应用中，可以在形式上和细节上对其作各种改变，而不偏离本申请的精神和范围。

Claims (12)

  1. 一种距离传感器接收模拟前端电路，其特征在于，包括：光敏二极管、电流积分模块、反相放大模块、复位模块及用于抵消所述光敏二极管背景光电流中的直流分量的抵消模块；
    所述抵消模块的第一端连接电源端；所述抵消模块的第二端分别连接所述光敏二极管、所述电流积分模块的第一端及所述复位模块的输出端；所述抵消模块的第三端连接所述反相放大模块的第一端；所述反相放大模块的第二端分别连接所述电流积分模块的第二端及所述复位模块的第一输入端，所述复位模块的第二输入端输入参考电压；
    其中，所述复位模块的第一输入端的电压与所述复位模块的第二输入端的电压相等，且所述复位模块与所述电流积分模块构成一单位增益放大单元。
  2. 根据权利要求1所述的距离传感器接收模拟前端电路，其特征在于，所述抵消模块包括采样电容及采样电子开关；
    所述采样电子开关的输入端与所述采样电容的一端连接在一起，作为所述抵消模块的所述第一端；所述采样电子开关的输出端作为所述抵消模块的所述第二端；所述采样电子开关的控制端与所述采样电容的另一端连接在一起，作为所述抵消模块的所述第三端。
  3. 根据权利要求1所述的距离传感器接收模拟前端电路，其特征在于，所述电流积分模块包括跨导放大器及积分电容；
    所述跨导放大器的输入端与所述积分电容的一端连接在一起，作为所述电流积分模块的所述第一端，所述跨导放大器的输出端与所述积分电容的另一端连接在一起，作为所述电流积分模块的所述第二端。
  4. 根据权利要求3所述的距离传感器接收模拟前端电路，其特征在于，所述跨导放大器具体包括：第一电子开关及第二电子开关；
    所述第一电子开关的控制端输入第一偏置电压，所述第一电子开关的输入端连接所述电源端，所述第一电子开关的输出端与所述第二电子开关的输入端连接在一起，作为所述跨导放大器的所述输出端，所述第二电子开关的控制端作为所述跨导放大器的所述输入端，所述第二电子开关的输出端接地。
  5. 根据权利要求1所述的距离传感器接收模拟前端电路，其特征在于，所述反相放大模块包括反相放大单元及第一控制开关；
    所述第一控制开关的一端作为所述反相放大模块的所述第一端，所述第一控制开关的另一端连接所述反相放大单元的输出端，所述反相放大单元的输入端作为所述反相放大模块的所述第二端。
  6. 根据权利要求5所述的距离传感器接收模拟前端电路，其特征在于，所述反相放大单元为反相放大器或宽带放大器。
  7. 根据权利要求6所述的距离传感器接收模拟前端电路，其特征在于，所述宽带放大器的带宽至少为采样保持环路的增益带宽积的2倍；其中，所述采样保持环路为所述抵消模块、所述反相放大模块、所述电流积分模块及所述光敏二极管组成的环路。
  8. 根据权利要求6或7所述的距离传感器接收模拟前端电路，其特征在于，所述宽带放大器具体包括：第三电子开关及第四电子开关；
    所述第三电子开关的输入端连接所述电源端，所述第三电子开关的控制端、输出端及所述第四电子开关的输入端连接在一起，作为所述宽带放大器的输出 端，所述第四电子开关的控制端作为所述宽带放大器的输入端，所述第四电子开关的输出端接地。
  9. 根据权利要求1所述的距离传感器接收模拟前端电路，其特征在于，所述复位模块包括误差放大器及第二控制开关；
    所述误差放大器的正向信号输入端作为所述复位模块的所述第一输入端；所述误差放大器的反向信号输入端作为所述复位模块的所述第二输入端；所述误差放大器的输出端连接所述第二控制开关的一端，所述第二控制开关的另一端作为所述复位模块的所述输出端。
  10. 根据权利要求8所述的距离传感器接收模拟前端电路，其特征在于，所述误差放大器具体包括第五电子开关、第六电子开关、第七电子开关、第八电子开关及第九电子开关；
    所述第五电子开关的输入端连接所述电源端，所述第五电子开关的控制端输入第二偏置电压，所述第五电子开关的输出端分别连接所述第六电子开关的输入端及所述第七电子开关的输入端；所述第六电子开关的控制端作为所述误差放大器的所述正向信号输入端，所述第六电子开关的输出端分别连接所述第八电子开关的输入端、控制端及所述九电子开关的控制端；所述第七电子开关的控制端作为所述误差放大器的所述反向信号输入端，所述第七电子开关的输出端与所述第九电子开关的输入端连接在一起，作为所述误差放大器的所述输出端，所述第八电子开关的控制端连接所述第九电子开关的控制端，所述第八电子开关的输出端及所述第九电子开关的输出端均接地。
  11. 根据权利要求1所述的距离传感器接收模拟前端电路，其特征在于，所述电路还包括第三控制开关；
    所述抵消模块的所述第二端通过所述第三控制开关连接所述电流积分模块的所述第一端及所述复位模块的所述输出端。
  12. 一种距离传感器，其特征在于，包括发射部及接收部；所述发射部包括发光二极管及用于驱动所述发光二极管的驱动电路；所述接收部包括如权利要求1至11中任意一项所述的距离传感器接收模拟前端电路及模数转换器；所述模数转换器连接至电流积分模块的第二端。
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