WO2019075699A1 - 信号转换电路、心率传感器和电子设备 - Google Patents

信号转换电路、心率传感器和电子设备 Download PDF

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WO2019075699A1
WO2019075699A1 PCT/CN2017/106919 CN2017106919W WO2019075699A1 WO 2019075699 A1 WO2019075699 A1 WO 2019075699A1 CN 2017106919 W CN2017106919 W CN 2017106919W WO 2019075699 A1 WO2019075699 A1 WO 2019075699A1
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Prior art keywords
signal
switch
conversion circuit
mos transistor
circuit
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PCT/CN2017/106919
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English (en)
French (fr)
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张孟文
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深圳市汇顶科技股份有限公司
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Priority to EP17911398.0A priority Critical patent/EP3499712B1/en
Priority to CN201780001406.3A priority patent/CN107980208B/zh
Priority to PCT/CN2017/106919 priority patent/WO2019075699A1/zh
Priority to US16/214,069 priority patent/US11504065B2/en
Publication of WO2019075699A1 publication Critical patent/WO2019075699A1/zh

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03K—PULSE TECHNIQUE
    • H03K19/00—Logic circuits, i.e. having at least two inputs acting on one output; Inverting circuits
    • H03K19/0175—Coupling arrangements; Interface arrangements
    • H03K19/017545—Coupling arrangements; Impedance matching circuits
    • H03K19/017572—Coupling arrangements; Impedance matching circuits using opto-electronic devices
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7203—Signal processing specially adapted for physiological signals or for diagnostic purposes for noise prevention, reduction or removal
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/005—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements using switched capacitors, e.g. dynamic amplifiers; using switched capacitors as resistors in differential amplifiers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/024—Detecting, measuring or recording pulse rate or heart rate
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording pulse, heart rate, blood pressure or blood flow; Combined pulse/heart-rate/blood pressure determination; Evaluating a cardiovascular condition not otherwise provided for, e.g. using combinations of techniques provided for in this group with electrocardiography or electroauscultation; Heart catheters for measuring blood pressure
    • A61B5/024—Detecting, measuring or recording pulse rate or heart rate
    • A61B5/02416—Detecting, measuring or recording pulse rate or heart rate using photoplethysmograph signals, e.g. generated by infrared radiation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6802—Sensor mounted on worn items
    • A61B5/6803—Head-worn items, e.g. helmets, masks, headphones or goggles
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
    • A61B5/6802—Sensor mounted on worn items
    • A61B5/681—Wristwatch-type devices
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
    • A61B5/6887—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient mounted on external non-worn devices, e.g. non-medical devices
    • A61B5/6898—Portable consumer electronic devices, e.g. music players, telephones, tablet computers
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7225—Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F1/00—Details of amplifiers with only discharge tubes, only semiconductor devices or only unspecified devices as amplifying elements
    • H03F1/34—Negative-feedback-circuit arrangements with or without positive feedback
    • H03F1/342—Negative-feedback-circuit arrangements with or without positive feedback in field-effect transistor amplifiers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/04—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with semiconductor devices only
    • H03F3/08—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with semiconductor devices only controlled by light
    • H03F3/082—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements with semiconductor devices only controlled by light with FET's
    • 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
    • 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
    • H03F3/45192—Folded cascode stages
    • 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
    • H03F3/45273—Mirror types
    • 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
    • H03F2203/45156—At least one capacitor being added at the input of a dif amp
    • 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
    • H03F2203/45326—Indexing scheme relating to differential amplifiers the AAC comprising one or more extra diodes, e.g. as level shifter, as diode coupled transistors
    • 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
    • H03F2203/45551—Indexing scheme relating to differential amplifiers the IC comprising one or more switched capacitors

Definitions

  • Embodiments of the present invention relate to the field of electronic technology and, more particularly, to signal conversion circuits, heart rate sensors, and electronic devices.
  • the current-type sensor has a very high output impedance.
  • a current-voltage (I-V) conversion circuit is usually used.
  • the input impedance of the conversion circuit is very small, the environmental interference signal can easily enter the I-V conversion circuit.
  • the human body and the circuit are not an equal potential body, so the noise on the human skin is transmitted to the input end of the IV circuit through a medium such as air, and then converted into a noise voltage by the IV conversion circuit, so that the entire acquisition is performed.
  • the signal-to-noise ratio (SNR) of the system drops dramatically.
  • one method of dealing with the problem is to increase the distance between the human body and the circuit, thereby weakening the path of the coupling, but doing so causes the signal to decrease with increasing distance, so when the distance reaches a certain level, The SNR will start to fall again; another method is to add a shield to the current sensor, but this will cause the light transmittance to decrease.
  • the current-type sensor that increases the shield is prone to parasitic capacitance, which in turn leads to the IV circuit. The noise is amplified again.
  • a signal conversion circuit a heart rate sensor, and an electronic device are provided.
  • the signal conversion circuit can effectively suppress environmental interference.
  • a signal conversion circuit comprising:
  • a photoelectric conversion circuit for converting an optical signal into a current signal, the current signal including a useful optical signal, a modulated optical signal, and a background optical signal converted signal in the optical signal in a first phase, the current signal being The second phase includes the converted signal of the background optical signal.
  • a differential signal conversion circuit 200 coupled to the photoelectric conversion circuit 100 for converting the current signal into a first differential signal and a second differential signal, the first differential signal being the current signal being at the first The integrated signal at the phase, the second differential signal being an integrated signal when the current signal is in the second phase.
  • the subtraction amplifier 300 is connected to the differential signal conversion circuit 200 for subtracting the first differential signal and the second differential signal and amplifying the subtracted difference to generate a third differential signal.
  • the common mode noise introduced in the environment can be suppressed by the differential signal conversion circuit 200.
  • the current signal is a differential modulus
  • the external interference signal is a common modulus. That is, the differential signal conversion circuit 200 allows only the current signal of the photoelectric conversion circuit to pass, and the coupled interference is suppressed.
  • the differential signal conversion circuit 200 includes: a first differential signal generating circuit for integrating the current signal at the first phase; and a second differential signal generating circuit for The current signal at the second phase is integrated, wherein the first differential signal generating circuit is coupled in parallel with the second differential signal generating circuit.
  • the first differential signal generating circuit includes a first integrating circuit 210 and a second integrating circuit 220
  • the second differential signal generating circuit includes a third integrating circuit 230 and a fourth integrating circuit 240
  • Each of the integrating circuits includes a capacitor and a switch
  • the differential signal converting circuit 200 further includes: a first switch 251, a second switch 252, and a first transconductance amplifier 290, each integrating circuit including a capacitor and a switch,
  • One end of the photoelectric conversion circuit 100 is connected to the positive input terminal of the first transconductance amplifier 290 through the first switch 251, and the other end of the photoelectric conversion circuit 100 passes through the second switch 252 and the first
  • the negative input terminal of the transconductance amplifier 290 is connected, and the positive input terminal of the first transconductance amplifier 290 is connected to the negative output terminal of the first transconductance amplifier 290 through the first integration circuit 210, the first A negative input terminal of the transconductance amplifier 290 is coupled to a positive output terminal
  • the first integration circuit 210 and the second integration circuit 220 are configured to perform the current signal in the first phase when the first switch 251 and the second switch 252 are both turned on. Integrating, and the third integrating circuit 230 and the fourth integrating circuit 240 are for integrating the current signal at the second phase.
  • the photoelectric conversion circuit 100 is a photodiode
  • the first transconductance amplifier 290 is further configured to receive a first voltage, where the first voltage is used to adjust a reverse bias voltage of the photodiode .
  • the technical solution of the embodiment of the invention can further improve the signal to noise ratio.
  • the differential signal conversion circuit 200 includes: a negative feedback loop for converting the current signal into the first differential signal and the differential signal conversion circuit 200 The second differential signal cancels a signal remaining in the background optical signal.
  • the negative feedback loop includes: a third switch 253, a fourth switch 254, and a current sampling circuit 270
  • the first integrating circuit 210 is connected to the first through the third switch 253
  • the second integrator circuit 220 is coupled to the positive output of the first transconductance amplifier 290 via the fourth switch 254, the positive output of the first transconductance amplifier 290
  • the current sampling circuit 270 is coupled to the negative output of the first transconductance amplifier 290.
  • the current sampling circuit 270 is configured to detect a signal remaining in the background optical signal when the third switch 253 and the fourth switch 254 are both disconnected, the third switch 253 and the fourth When the switch 254 is turned on, the current sampling circuit 270 is used to cancel the signal remaining in the background light signal.
  • the technical solution of the embodiment of the present invention can increase the dynamic range of the effective signal input by the differential signal conversion circuit 200.
  • the current sampling circuit 270 includes: a fifth switch 261, a sixth switch 263, a seventh switch 268, an eighth switch 260, a first capacitor 264, a second capacitor 267, and a first metal oxide.
  • a positive output terminal of the first transconductance amplifier 290 is connected to the first MOS transistor through the fifth switch 261 a drain of 262, a drain of the first MOS transistor 262 is connected to a gate of the first MOS transistor 262, and a gate of the MOS transistor is connected to the second MOS transistor through the sixth switch 263 a gate of 265, a source of the first MOS transistor 262 is connected to a source of the second MOS transistor 265, and a gate of the second MOS transistor 265 is connected to the first via a first capacitor 264 a source of the second MOS transistor 265, a drain of the second MOS transistor 265 is connected to
  • the drain of the fourth MOS transistor 269 is connected to the first transconductance through the eighth switch 260 a negative output terminal of the amplifier 290; wherein the first MOS transistor 262 and the second MOS transistor 265 are "N-type” MOS transistors, and the third MOS transistor 266 and the fourth MOS transistor 269 are " P-type "MOS tube.
  • the current sampling circuit 270 when the fifth switch 261, the sixth switch 263, the seventh switch 268, and the eighth switch 260 are both turned on, the current sampling circuit 270 is configured to detect a signal remaining in the background optical signal; when the fifth switch 261, the sixth switch 263, the seventh switch 268, and the eighth switch 260 are both turned off, the current sampling circuit 270 is used to cancel a signal remaining in the background light signal.
  • the differential signal conversion circuit 200 further includes: a second transconductance amplifier 280, a positive input terminal of the second transconductance amplifier 280 and a positive input terminal of the first transconductance amplifier 290 Connected, the negative input of the second transconductance amplifier 280 receives a common mode voltage that is used to stabilize the voltage value of the positive input of the first transconductance amplifier 290.
  • the second transconductance amplifier 280 can ensure that the differential signal conversion circuit 200 is in a normal working state.
  • the subtraction amplifier 300 includes: a first branch 310, a second branch 320, a third branch 330, a fourth branch 340, and a third transconductance amplifier 370, wherein The first branch 310 and the second branch 320 are configured to receive the first differential signal, and the third branch 330 and the fourth branch 340 are configured to receive the second differential signal, The third transconductance amplifier 370 is configured to generate the third differential signal according to the first differential signal and the second differential signal.
  • a heart rate sensor comprising: any of the signal conversion circuits of the first aspect.
  • the heart rate sensor further includes:
  • an analog to digital converter coupled to the signal conversion circuit for converting an analog signal output by the signal conversion circuit into a digital signal.
  • an electronic device comprising: a heart rate sensor that is possible in any of the second aspects.
  • the electronic device can be a smart wearable device such as a headset or a wristband.
  • FIG. 1 is a schematic block diagram of a signal conversion circuit of an embodiment of the present invention.
  • FIG. 2 is a schematic diagram of a signal conversion circuit of an embodiment of the present invention.
  • FIG. 3 is a schematic diagram of a subtraction amplifier of an embodiment of the present invention.
  • FIG. 4 is a schematic diagram of a transconductance amplifier in accordance with an embodiment of the present invention.
  • Fig. 5 is a view showing the operation timing of the signal conversion circuit of the embodiment of the present invention.
  • the signal conversion circuit of the embodiment of the present invention can be applied to any device and device configured with a signal conversion circuit.
  • the technical solution of the embodiments of the present invention is applicable to a weak current signal amplification front end sensitive to environmental noise, and an application having special requirements and high SNR against interference capability.
  • a heart rate sensor For example, a heart rate sensor.
  • the present invention provides a signal conversion circuit of a new structure, so that the influence of environmental interference is suppressed.
  • FIG. 1 is a schematic block diagram of a signal conversion circuit of an embodiment of the present invention.
  • the signal conversion circuit includes:
  • the photoelectric conversion circuit 100 is configured to convert the optical signal into a current signal, where the current signal includes a useful optical signal, a modulated optical signal, and a background optical signal converted signal in the optical signal, where the current signal is in the second phase.
  • the phase includes the signal converted by the background light signal;
  • the differential signal conversion circuit 200 is coupled to the photoelectric conversion circuit 100 for converting the current signal into a first differential signal and a second differential signal, the first differential signal being the An integrated signal when the current signal is in the first phase, wherein the second differential signal is an integrated signal when the current signal is in the second phase;
  • the subtraction amplifier 300 is connected to the differential signal conversion circuit 200 for A difference between the differential signal and the second differential signal is amplified to generate a third differential signal.
  • the useful optical signal in the embodiment of the present invention may be an optical signal carrying target information (for example, heart rate data information), and the modulated optical signal may be a modulated signal used to modulate the useful optical signal, and the background optical signal may be
  • the photoelectric conversion circuit 100 receives a signal formed by ambient light.
  • the input signals of the photoelectric conversion circuit 100 in the embodiment of the present invention include a useful optical signal, a modulated optical signal, and a background optical signal. It should be understood that the above definitions of the useful optical signal, the modulated optical signal, and the background optical signal are exemplary, and are not specifically limited in the embodiment of the present invention.
  • first phase and the second phase in the embodiment of the present invention are different phases, and the present invention
  • the meaning of the first phase and the second phase is not specifically limited by the embodiment.
  • the first phase may refer to: all phases included in the converted current signal when the photoelectric conversion circuit 100 is configured to convert the useful optical signal, the modulated optical signal, and the background optical signal in the optical signal into a current signal
  • the second phase may refer to all phases included in the converted current signal when the photoelectric conversion circuit 100 is only used to convert the background optical signal in the optical signal into a current signal.
  • the output impedance of the photoelectric conversion circuit 100 is very high, in order to efficiently convert the current signal into a voltage signal, in the embodiment of the present invention, the common mode noise introduced in the environment can be suppressed by the differential signal conversion circuit 200.
  • the current signal flows in from the other end of the photoelectric conversion circuit 100, it flows out from one end of the photoelectric conversion circuit 100. Therefore, for the input of the differential signal conversion circuit 200, the current signal is a differential modulus. It is assumed that an external interference signal is simultaneously coupled to Vipi, Vini, and the interference signal is a common modulus.
  • the differential signal conversion circuit 200 allows only the current of the photoelectric conversion circuit to flow. In other words, the coupled interference is suppressed.
  • the differential signal conversion circuit 200 in the embodiment of the present invention can effectively suppress the interference signal of the environment, thereby improving the signal-to-noise ratio of the output signal.
  • the differential signal conversion circuit 200 suppresses the common mode noise introduced in the environment when receiving the current signal output from the photoelectric conversion circuit. Then, the current signals in the first phase and the second phase are separately integrated to obtain the first differential signal and the second differential signal.
  • the first differential signal is an integrated signal when the current signal is in the first phase
  • the second differential signal is an integrated signal when the current signal is in the second phase
  • the current signal includes useful light in the first phase a signal, a modulated optical signal, and a converted signal of the background optical signal, the optical signal including only the converted signal of the background optical signal in the second phase.
  • the subtraction amplifier 300 can increase the difference between the first differential signal and the second differential signal, so that the differential signal output by the subtraction amplifier 300 does not involve the background light signal, thereby further improving. Signal to noise ratio.
  • a current signal is generated by the photoelectric conversion circuit 100, and the integrated differential modulus (i.e., the first differential signal and the second differential signal) of the current signal on the two phases is acquired by the differential signal conversion circuit 200.
  • the differential signals of the two phases are subtracted by the subtraction amplifier 300 to increase the signal-to-noise ratio of the output signal.
  • the background light signal refers to a signal formed by the photoelectric conversion circuit 100 for collecting background light.
  • the background light here can be understood as a signal formed by the photoelectric conversion circuit 100 and not formed by the light emitted by the LED light source, for example, ambient light.
  • the mode noise refers to a noise signal that is not generated by the photoelectric conversion circuit 100 and is input to the differential signal conversion circuit 200, for example, noise on human skin in a heart rate acquisition system or the like.
  • the signal conversion circuit of the embodiment of the present invention can not only suppress the common mode noise introduced in the environment through the differential signal conversion circuit 200, but also improve the signal-to-noise ratio of the output signal, and it is possible that the differential signal output from the subtraction amplifier 300 is not involved.
  • the background light signal (when the background light signal is a constant amount) further improves the signal-to-noise ratio, thereby improving the accuracy of signal detection.
  • the photoelectric conversion circuit 100 may be a photodiode.
  • the photoelectric conversion circuit 100 includes a diode 120 and a parasitic capacitor 110, which is connected in parallel with the parasitic capacitor 110.
  • the diode 120 can be an ideal diode, that is, a diode with a forward voltage drop of zero and a reverse leakage current of zero.
  • the photodiode is only used as an exemplary description of the photoelectric conversion circuit 100, and is not specifically limited in the embodiment of the present invention.
  • the differential signal conversion circuit 200 can also integrate weak current signals from other devices.
  • the differential signal conversion circuit 200 of the embodiment of the present invention will be exemplarily described below.
  • the differential signal conversion circuit 200 includes: a first differential signal generating circuit for integrating the current signal in the first phase; and a second differential signal generating circuit configured to be in the second phase The current signal is integrated, wherein the first differential signal generating circuit is coupled in parallel with the second differential signal generating circuit.
  • FIG. 2 is a schematic diagram of a differential signal conversion circuit 200 in accordance with an embodiment of the present invention.
  • the first differential signal generating circuit includes a first integrating circuit 210 and a second integrating circuit 220
  • the second differential signal generating circuit includes a third integrating circuit 230 and a fourth integrating circuit 240, each integrating circuit A capacitor and a switch are included.
  • the differential signal conversion circuit 200 further includes a first switch 251, a second switch 252, and a first transconductance amplifier 290.
  • Each of the integrating circuits includes a capacitor and a switch, and the photoelectric conversion circuit 100 One end is connected to the positive input end of the first transconductance amplifier 290 through the first switch 251, and the other end of the photoelectric conversion circuit 100 is connected to the negative input end of the first transconductance amplifier 290 through the second switch 252.
  • a positive input terminal of the first transconductance amplifier 290 is coupled to the first transconductance amplifier through the first integrating circuit 210
  • the negative output terminal of the second transconductance amplifier 290 is connected to the positive output terminal of the first transconductance amplifier 290 through the second integration circuit 220.
  • the third integration circuit 230 and the first The integrating circuit 210 is connected in parallel, and the fourth integrating circuit 240 is connected in parallel with the second integrating circuit 220.
  • the first integrating circuit 210 and the second integrating circuit 220 are configured to integrate the current signal in the first phase
  • the third The integrating circuit 230 and the fourth integrating circuit 240 are for integrating the current signal at the second phase.
  • the first integration circuit 210 includes a third capacitor 211 and a ninth switch 212
  • the second integration circuit 220 includes a fourth capacitor 221 and a tenth switch 222
  • the third integration circuit 230 includes a fifth capacitor. 231 and the eleventh switch 232
  • the fourth integrating circuit 240 includes a sixth capacitor 241 and a twelfth switch 242.
  • the ninth switch 212 in the first integration circuit 210 and the tenth switch 222 in the second integration circuit 220 can be controlled to be turned on or off by the first control signal (ck1i), and controlled by the second control signal (ck2i).
  • the eleventh switch 232 in the third integrating circuit 230 and the twelfth switch 242 in the fourth integrating circuit 240 are turned on or off.
  • the first switch 251 and the second switch 252 are turned on.
  • the current signal at the first phase is integrated.
  • the current signal at the second phase is integrated.
  • the background light signal is a constant amount
  • this conversion is accomplished by subtraction amplifier 300.
  • the first switch 251 and the second switch 252 are turned off, that is, the output of the photoelectric conversion circuit 100 no longer affects the integrator.
  • the photoelectric conversion circuit 100 is a photodiode
  • the first transconductance amplifier 290 is further configured to receive a first voltage, where the first voltage is used to adjust a reverse bias voltage of the photodiode. .
  • the larger parasitic capacitance 110 causes the noise of the first transconductance amplifier 290 itself to be amplified.
  • Cpd can be divided into diffusion capacitance and barrier capacitance. Since the photodiode is reverse biased, the diffusion capacitance is basically negligible. It can be found that the barrier capacitance is inversely proportional to the voltage of the photodiode. Therefore, in order to obtain lower noise, it is necessary to increase the reverse bias voltage of the photodiode as much as possible.
  • the positive and negative input terminals Vipi and Vini of the differential signal conversion circuit 200 are respectively connected to the cathode and the anode of the photodiode, and at this time, a first input is input to the first transconductance amplifier 290.
  • a voltage Vos can bias the photodiode to a suitable reverse bias voltage, thereby reducing the size of the Cpd, thereby increasing the signal to noise ratio of the output signal of the differential signal conversion circuit 200.
  • the current signal in the embodiment of the present invention includes the converted signal of the background optical signal
  • the background optical signal when the background optical signal is not a constant amount, the dynamic range of the effective signal input by the differential signal conversion circuit 200 may be reduced.
  • the effective signal output from the differential signal conversion circuit 200 i.e., the effective signal input from the subtraction amplifier 300
  • the effective signal output from the differential signal conversion circuit 200 includes the signal remaining in the above-described background optical signal.
  • the first differential signal is a differential signal formed by the differential signal conversion circuit 200 integrating only the modulated optical signal and the useful optical signal in the first phase.
  • the two differential signals are zero.
  • the first differential signal is a signal, a modulated light signal, and a useful light that the differential signal conversion circuit 200 remains only in the first phase of the current signal to the background light signal.
  • the signal is a differential signal formed by integration
  • the second differential signal is a differential signal formed by the differential signal conversion circuit 200 integrating only the signal remaining in the background optical signal in the second phase of the current signal.
  • the residual signal in the background optical signal referred to herein may refer to: the background optical signal minus a constant obtained signal, which is a differential modulus, which is an optical signal that the differential signal conversion circuit 200 can integrate in the background optical signal. .
  • a negative feedback loop is also provided, which increases the dynamic range of the effective signal input by the differential signal conversion circuit 200 by canceling the residual signal in the background light signal.
  • the differential signal conversion circuit 200 includes: a negative feedback loop for canceling the background when the differential signal conversion circuit 200 converts the current signal into the first differential signal and the second differential signal. A signal remaining in the optical signal.
  • the negative feedback loop includes a third switch 253, a fourth switch 254, and a current sampling circuit 270.
  • the first integrating circuit 210 is connected to the first transconductance amplifier 290 through the third switch 253.
  • a negative output terminal the second integrating circuit 220 is connected to the positive output end of the first transconductance amplifier 290 through the fourth switch 254, and the positive output end of the first transconductance amplifier 290 is connected to the current sampling circuit 270 through the current sampling circuit 270 a negative output terminal of the first transconductance amplifier 290;
  • the current sampling circuit 270 is configured to detect a signal remaining in the background optical signal, and the current is when the third switch 253 and the fourth switch 254 are turned on.
  • the sampling circuit 270 is for canceling signals remaining in the background light signal.
  • the current sampling circuit 270 includes: a fifth switch 261, a sixth switch 263, a seventh switch 268, an eighth switch 260, a first capacitor 264, a second capacitor 267, and a first metal oxide.
  • the positive output terminal of the first transconductance amplifier 290 is connected to the fifth switch 261 through a drain of the first MOS transistor 262, a drain of the first MOS transistor 262 is connected to a gate of the first MOS transistor 262, and a gate of the MOS transistor is connected to the second MOS transistor through the sixth switch 263 a gate of 265, a source of the first MOS transistor 262 is connected to a source of the second MOS transistor 265, and a gate of the second MOS transistor 265 is connected to the second MOS transistor 265 through the first capacitor 264
  • MOS Metal-
  • the current sampling circuit 270 is configured to detect a signal remaining in the background optical signal; the fifth switch 261, the sixth When the switch 263, the seventh switch 268, and the eighth switch 260 are both turned off, the current sampling circuit 270 is used to cancel the signal remaining in the background light signal.
  • the third switch 253 and the fourth switch 254 can be controlled to be turned on or off by a third control signal (shn), and the fifth switch 261, the sixth switch 263, and the seventh are controlled by the fourth control signal (shp).
  • the switch 268 and the eighth switch 260 are turned on or off.
  • the sixth switch 263, the seventh switch 268, and the eighth switch 260 are turned off.
  • the first transconductance amplifier 290 forms a negative feedback loop with the first MOS transistor, the second MOS transistor 265, the third MOS transistor 266, the photoelectric conversion circuit 100, and the fourth MOS transistor 269, and continues to be interrupted according to the amplifier.
  • the principle is that the current can only flow from the power source to the reference ground through the branch of the second MOS transistor 265, the photoelectric conversion circuit 100, and the third MOS transistor 266.
  • the photoelectric conversion circuit 100 receives only the background light signal, and therefore, the current flowing through the second MOS transistor 265 and the third MOS transistor 266 is the current generated by the signal remaining in the background light signal.
  • the differential signal conversion circuit 200 can cancel the signals remaining in the background light signals in the current signals when the operating state is in operation.
  • the negative feedback loop can be added to the differential signal conversion circuit 200 to cancel the current of the background light signal in the input current, thereby increasing the dynamic of the effective signal input by the differential signal conversion circuit 200. range.
  • MOSFET Metal-Oxide-Semiconductor Field-Effect Transistor
  • NMOSFET N-type MOS transistor
  • PMOSFET P-type MOS transistor
  • NMOSFET its source The pole and the drain are connected to the N-type semiconductor, and the high voltage is connected to the drain terminal, and the low voltage is connected to the source terminal, and the actual current direction is the inflow drain.
  • the source and the drain are connected to the P-type semiconductor, the high voltage is the source terminal, the low voltage is the drain terminal, and the actual current direction is the outflow drain.
  • the first MOS transistor 262 and the second MOS transistor 265 may be “N-type” MOS transistors
  • the third MOS transistor 266 and the fourth MOS transistor 269 may be “P-type” MOS transistors.
  • embodiments of the invention are not limited thereto.
  • the negative feedback loop composed of the third switch 253, the fourth switch 254, and the current sampling circuit 270 is intended to increase the dynamic range of the effective signal input by the differential signal conversion circuit 200. That is, the current structure as shown in FIG. 2 is only an exemplary description, and the embodiment of the present invention is not specifically limited.
  • the signal conversion circuit 200 operates abnormally.
  • the differential signal conversion circuit 200 includes a second transconductance amplifier 280, and a positive input terminal of the second transconductance amplifier 280 is connected to a positive input terminal of the first transconductance amplifier 290.
  • the negative input of the second transconductance amplifier 280 receives a common mode voltage that is used to stabilize the voltage value at the positive input of the first transconductance amplifier 290.
  • a second transconductance amplifier 280 is added to the current sampling circuit 270 to form another negative feedback loop.
  • the positive input terminal of the first transconductance amplifier 290 is known.
  • the voltage at the positive input of the second transconductance amplifier 280 is the same, thereby limiting the voltage of Vipi to a certain common mode voltage Vcm. Further, by controlling the common mode voltage Vcm, it is possible to ensure that the differential signal conversion circuit 200 is in a normal operation state.
  • the differential signal conversion circuit 200 can input the differential current signal and output the differential signals of the two phases, thereby suppressing the common mode noise introduced in the environment. Further, by inputting a first voltage (for example, a positive offset voltage) to the first transconductance amplifier 290, the signal-to-noise ratio of the output signal can be further improved. Further, the dynamic range of the effective signal input by the differential signal conversion circuit 200 can be increased by the current sampling circuit 270. The second transconductance amplifier 280 can ensure that the differential signal conversion circuit 200 is in a normal operating state.
  • a first voltage for example, a positive offset voltage
  • the negative feedback loop formed by the negative feedback loop and the second transconductance amplifier 280 belongs to the auxiliary circuit of the differential signal conversion circuit 200.
  • the circuit may be laid out according to actual requirements, which is not specifically limited in the embodiment of the present invention.
  • the subtraction amplifier 300 of the embodiment of the present invention will be exemplarily described below.
  • FIG. 3 is a schematic diagram of a subtraction amplifier 300 in accordance with an embodiment of the present invention.
  • the subtraction amplifier 300 includes a first branch 310, a second branch 320, a third branch 330, a fourth branch 340, and a third transconductance amplifier 370, wherein the first branch 310 and the second branch 320 are configured to receive the first differential signal, the third branch 330 and the fourth branch 340 are configured to receive the second differential signal, and the third transconductance amplifier 370 is configured to The first differential signal and the second differential signal generate the third differential signal.
  • the first branch 310 includes a thirteenth switch 311, a seventh capacitor 312, and a fourteenth switch 313.
  • the second branch 320 includes a fifteenth switch 321 and an eighth capacitor 322.
  • a sixteenth switch 323 the third branch 330 includes a seventeenth switch 331, a ninth capacitor 332 and a seventeenth switch 333
  • the fourth branch 340 includes an eighteenth switch 341, a tenth capacitor 342 and a Nineteen switches 343.
  • one end of the ninth capacitor 332 is sequentially connected to one end of the seventh capacitor 312 through the twentieth switch 351 and the twenty-first switch 352, and the other end of the ninth capacitor 332 passes through the twenty-second.
  • the switch 353 and the twenty-third switch 354 are connected to the other end of the seventh capacitor 312.
  • One end of the eighth capacitor 322 is sequentially connected to one end of the tenth capacitor 342 through the twenty-fourth switch 355 and the twenty-fif switch 356.
  • the other end of the eight capacitor 322 is sequentially connected to the other end of the tenth capacitor 342 through the twenty-sixth switch 357 and the twenty-seventh switch 358.
  • the fifth control signal (ck1p) is used to control the on and off of the following switches:
  • the sixth control signal (ck2p) is used to control the on and off of the following switches:
  • the seventeenth switch 331, the seventeenth switch 333, the eighteenth switch 341, the nineteenth switch 343, the twenty-first switch 352, the twenty-third switch 354 are connected, the twenty-fourth switch 355, the twenty-sixth Switch 357.
  • the main function of the subtraction amplifier 300 is to subtract and amplify the first differential signal and the second differential signal outputted by the differential signal conversion circuit 200 to obtain a third difference.
  • the signal is then outputted by the third differential signal.
  • the conversion of the current signal is achieved.
  • Cfp represents the capacitance value of the eleventh capacitor 361
  • Cfn represents the capacitance value of the twelfth capacitor 362
  • Csp1, Csn1, Csp2, and Csn2 respectively represent the capacitance value of the seventh capacitor 312, the capacitance value of the eighth capacitor 322, and the The capacitance value of the nine capacitor 332 and the capacitance value of the tenth capacitor 342.
  • the first switch 251 and the second switch 252 are turned off.
  • the first differential signal is converted and stored in the eleventh capacitor 361 and the twelfth capacitor 362.
  • Cs/Cf is an amplification factor
  • Vcp1-Vcn1 is a first differential signal of an embodiment of the present invention.
  • Vcp2-Vcn2 is the second differential signal of the embodiment of the present invention.
  • Vo, pga(N) N*(Cs/Cf)*[(Vcp1-Vcn1)-(Vcp2-Vcn2)].
  • circuit structure shown in FIG. 3 is only an example of the subtraction amplifier 300 of the embodiment of the present invention, and the embodiment of the present invention is not limited thereto.
  • FIG. 4 is a schematic diagram of a first transconductance amplifier 290 in accordance with an embodiment of the present invention.
  • the fifth MOS transistor 403 and the sixth MOS transistor 404 constitute a differential input pair tube for providing a required transconductance
  • the seventh MOS transistor 401 is a tail current source of the input pair tube for Provide a certain bias current.
  • a self-source cascode MOSFET (SCM) composed of an eighth MOS transistor 407, a ninth MOS transistor 408, a tenth MOS transistor 409, and an eleventh MOS transistor 410 for receiving a differential pair output current And provide a certain output load resistance.
  • the cascode MOS transistor in the embodiment of the present invention may include two PMOSFETs, and when one of the PMOSFETs operates in a linear region, the electrical characteristics may be equivalent to one resistor.
  • a current mirror composed of the twelfth MOS transistor 405 and the thirteenth MOS transistor 406 is also provided.
  • a certain output load resistance is connected in parallel with the equivalent resistance of the cascode MOS transistor to form an output resistance of the transconductance amplifier.
  • a fourteenth MOS transistor 402 is disposed between the nodes Vvg and Vs, and flows through the fifth MOS transistor 403 and the sixth MOS transistor 404 when the first transconductance amplifier 290 operates normally.
  • the first transconductance amplifier 290 has the circuit structure shown in FIG. 4, and the circuit structure of the transconductance amplifier in the prior art can also be used. That is, the first transconductance amplifier 290 in the embodiment of the present invention may be any circuit structure capable of generating a constant first voltage.
  • the second transconductance amplifier 280 of the embodiment of the present invention functions as follows:
  • the third transconductance amplifier 370 functions as follows:
  • the circuit structure of the embodiment of the present invention is not specifically limited.
  • Vvg and Vs may be short-circuited and the fourteenth MOS transistor 402 removed, and Vbp2 and Von may be shorted, based on the first transconductance amplifier 290 as shown in FIG. Together, and Vbp2 is no longer connected to the bias voltage.
  • Vvg and Vs may be shorted and the fourteenth MOS transistor 402 may be removed on the basis of the first transconductance amplifier 290 as shown in FIG.
  • the circuit in the embodiment of the present invention may further include: a reset circuit and a negative feedback loop, such that the initial state of the capacitor involved in the embodiment of the present invention is 0, and the output common mode voltage is Vcm.
  • the common mode negative feedback loop due to the reset circuit and the differential output is not critical to the present invention. I will not repeat them here.
  • the circuit in the embodiment of the present invention may further include: an analog-to-digital converter connected to the signal conversion circuit of the embodiment of the present invention for converting the analog signal output by the signal conversion circuit into a digital signal.
  • a heart rate sensor including the above-mentioned signal conversion circuit is also provided in the embodiment of the present invention.
  • the heart rate sensor may further include: an analog to digital converter coupled to the signal conversion circuit for converting the analog signal output by the signal conversion circuit into a digital signal.
  • a data processing circuit connected to the digital-to-analog converter for receiving the digital signal and processing may be further included.
  • an electronic device including the heart rate sensor described above is also provided.
  • the electronic device may be any electronic device, for example, the electronic device may be a smart wearable device such as a headset or a wristband; for example, the electronic device is a mobile phone, a tablet computer, a notebook computer, Computer, MP3, MP4, etc.

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Abstract

提供了一种信号转换电路、心率传感器和电子设备，该信号转换电路包括：光电转换电路，用于将光信号转换成电流信号，该电流信号在第一相位包括该光信号中的有用光信号、调制光信号和背景光信号转换后的信号，该电流信号在第二相位包括背景光信号转换后的信号；差分信号转换电路，与该光电转换电路连接，用于将该电流信号转换为第一差分信号和第二差分信号，该第一差分信号为该电流信号处于该第一相位时的积分信号，该第二差分信号为该电流信号处于该第二相位时的积分信号；该减法放大器，与该差分信号转换电路连接，用于将该第一差分信号和该第二差分信号的差值放大，以生成第三差分信号。本发明实施例的信号转换电路能够有效抑制环境干扰。

Description

信号转换电路、心率传感器和电子设备 技术领域
本发明实施例涉及电子技术领域，并且更具体地，涉及信号转换电路、心率传感器和电子设备。
背景技术
电流型传感器的输出阻抗非常高，为了将电流信号有效地转换成电压信号，通常会采用电流-电压(I-V)转换电路。但是由于转换电路的输入阻抗非常小，导致环境的干扰信号很容易就进到了I-V转换电路中。例如，心率采集系统中，人体通常和电路不是一个等势体，因此人体皮肤上的噪声就会通过空气等介质传递到I-V电路的输入端，随后被I-V转换电路转换成噪声电压，使得整个采集系统的信噪比(SNR)急剧下降。
现有技术中，处理该问题的一种方法为：增加人体和电路距离，从而减弱耦合的路径，但是，这样做会导致信号随距离增大而减小，因此，当距离达到一定的时候，SNR又会开始下降；另一种方法为：给电流型传感器增加屏蔽罩，但是，这样做会导致透光率下降，此外，增加屏蔽罩的电流型传感器容易产生寄生电容，进而导致I-V电路的噪声重新被放大。
即，现有技术中并没有能够有效抑制环境干扰的信号转换电路。
发明内容
提供了一种信号转换电路、心率传感器和电子设备。该信号转换电路能够有效抑制环境干扰。
第一方面，提供了一种信号转换电路，包括：
光电转换电路，用于将光信号转换成电流信号，所述电流信号在第一相位包括所述光信号中的有用光信号、调制光信号和背景光信号转换后的信号，所述电流信号在第二相位包括所述背景光信号转换后的信号。
差分信号转换电路200，与所述光电转换电路100连接，用于将所述电流信号转换为第一差分信号和第二差分信号，所述第一差分信号为所述电流信号处于所述第一相位时的积分信号，所述第二差分信号为所述电流信号处于所述第二相位时的积分信号。
所述减法放大器300，与所述差分信号转换电路200连接，用于将所述第一差分信号和所述第二差分信号相减并将相减的差值放大，以生成第三差分信号。
本发明实施例中，通过差分信号转换电路200可以抑制环境中引入的共模噪声。具体而言，对于差分信号转换电路200来说，该电流信号是一个差模量，而外部干扰信号是一个共模量。也就是说，差分信号转换电路200只允许光电转换电路的电流信号通过，而耦合的干扰会被抑制。
在一些可能的实现方式中，所述差分信号转换电路200包括：第一差分信号产生电路，用于对处于所述第一相位的所述电流信号进行积分；第二差分信号产生电路，用于对处于所述第二相位的所述电流信号进行积分，其中，所述第一差分信号产生电路与所述第二差分信号产生电路并联。
在一些可能的实现方式中，所述第一差分信号产生电路包括第一积分电路210和第二积分电路220，所述第二差分信号产生电路包括第三积分电路230和第四积分电路240，每个积分电路包括一个电容器和一个开关，所述差分信号转换电路200还包括：第一开关251、第二开关252和第一跨导放大器290，每个积分电路包括一个电容器和一个开关，所述光电转换电路100的一端通过所述第一开关251与所述第一跨导放大器290的正输入端相连，所述光电转换电路100的另一端通过所述第二开关252与所述第一跨导放大器290的负输入端相连，所述第一跨导放大器290的正输入端通过所述第一积分电路210连接至所述第一跨导放大器290的负输出端相连，所述第一跨导放大器290的负输入端通过所述第二积分电路220连接至所述第一跨导放大器290的正输出端相连，所述第三积分电路230与所述第一积分电路210并联，所述第四积分电路240与所述第二积分电路220并联。
其中，所述第一开关251和所述第二开关252均导通时，所述第一积分电路210和所述第二积分电路220用于对处于所述第一相位的所述电流信号进行积分，并且所述第三积分电路230和所述第四积分电路240用于对处于所述第二相位的所述电流信号进行积分。
在一些可能的实现方式中，所述光电转换电路100为光敏二极管，所述第一跨导放大器290还用于接收第一电压，所述第一电压用于调整所述光敏二极管的反偏电压。
本发明实施例的技术方案，能够进一步提高信噪比。
在一些可能的实现方式中，所述差分信号转换电路200包括：负反馈回路，所述负反馈回路用于在所述差分信号转换电路200将所述电流信号转换为所述第一差分信号和所述第二差分信号时，抵消所述背景光信号中残留的信号。
在一些可能的实现方式中，所述负反馈回路包括：第三开关253、第四开关254和电流采样电路270，所述第一积分电路210通过所述第三开关253连接至所述第一跨导放大器290的负输出端，所述第二积分电路220通过所述第四开关254连接至所述第一跨导放大器290的正输出端，所述第一跨导放大器290的正输出端通过所述电流采样电路270连接至所述第一跨导放大器290的负输出端。
其中，所述第三开关253和所述第四开关254均断开时，所述电流采样电路270用于检测所述背景光信号中残留的信号，所述第三开关253和所述第四开关254导通均时，所述电流采样电路270用于抵消所述背景光信号中残留的信号。
本发明实施例的技术方案，能够增大差分信号转换电路200输入的有效信号的动态范围。
在一些可能的实现方式中，所述电流采样电路270包括：第五开关261、第六开关263、第七开关268、第八开关260、第一电容264、第二电容267、第一金属氧化物半导体MOS管、第二MOS管265、第三MOS管266和第四MOS管269；所述第一跨导放大器290的正输出端通过所述第五开关261连接至所述第一MOS管262的漏极，所述第一MOS管262的漏极和所述第一MOS管262的栅极相连，所述MOS管的栅极通过所述第六开关263连接至所述第二MOS管265的栅极，所述第一MOS管262的源极与所述第二MOS管265的源极相连，所述第二MOS管265的栅极通过所述第一电容264连接至所述第二MOS管265的源极，所述第二MOS管265的漏极通过所述光电转换电路100连接至所述第三MOS管266的漏极，所述第三MOS管266的栅极通过所述第二电容267连接至所述第三MOS管266的源极，所述第三MOS管266的栅极通过所述第七开关268连接至所述第四MOS管269，所述第三MOS管266的源极与所述第四MOS管269的源极相连，所述第四MOS管269的栅极与所述第四MOS管269的漏极相连，所述第四MOS管269的漏极通过所述第八开关260连接至所述第一跨导放 大器290的负输出端；其中，所述第一MOS管262和所述第二MOS管265为“N型”MOS管，所述第三MOS管266和所述第四MOS管269为“P型”MOS管。
在一些可能的实现方式中，所述第五开关261、所述第六开关263、所述第七开关268和所述第八开关260均导通时，所述电流采样电路270用于检测所述背景光信号中残留的信号；所述第五开关261、所述第六开关263、所述第七开关268和所述第八开关260均断开时，所述电流采样电路270用于抵消所述背景光信号中残留的信号。
在一些可能的实现方式中，所述差分信号转换电路200还包括：第二跨导放大器280，所述第二跨导放大器280的正输入端与所述第一跨导放大器290的正输入端相连，所述第二跨导放大器280的负输入端接收共模电压，所述共模电压用于稳定所述第一跨导放大器290的正输入端的电压值。
本发明实施例的技术方案，通过第二跨导放大器280，能够保证差分信号转换电路200处于正常工作状态。
在一些可能的实现方式中，所述减法放大器300包括：第一支路310、第二支路320、第三支路330、第四支路340和第三跨导放大器370，其中，所述第一支路310和所述第二支路320用于接收所述第一差分信号，所述第三支路330和所述第四支路340用于接收所述第二差分信号，所述第三跨导放大器370用于根据所述第一差分信号和所述第二差分信号生成所述第三差分信号。
第二方面，提供了一种心率传感器，包括：第一方面中的任一信号转换电路。
在一些可能的实现方式中，所述心率传感器还包括：
模数转换器，与所述信号转换电路相连，用于将所述信号转换电路输出的模拟信号转化为数字信号。
第三方面，提供了一种电子设备，包括：第二方面中任一种可能实现的心率传感器。
在一些可能的实现方式中，该电子设备可以为耳机、手环等智能可穿戴设备。
附图说明
图1是本发明实施例的信号转换电路的示意性框图。
图2是本发明实施例的信号转换电路的示意图。
图3是本发明实施例的减法放大器的示意图。
图4是本发明实施例的跨导放大器的示意图。
图5是本发明实施例的信号转换电路的工作时序的示意图。
具体实施方式
下面将结合附图，对本发明实施例中的技术方案进行描述。
应理解，本发明实施例的信号转换电路可以适用于任何配置有信号转换电路的装置以及设备。尤其是，本发明实施例的技术方案适用于对环境噪声敏感的弱电流信号放大前端，以及对抗干扰能力有特殊要求、较高SNR的应用。例如，心率传感器。
为了抑制环境干扰，本发明提供了一种新结构的信号转换电路，使得环境干扰的影响得到抑制。
图1是本发明实施例的信号转换电路的示意性框图。
如图1所示，该信号转换电路包括：
光电转换电路100，用于将光信号转换成电流信号，该电流信号在第一相位包括该光信号中的有用光信号、调制光信号和背景光信号转换后的信号，该电流信号在第二相位包括上述背景光信号转换后的信号；差分信号转换电路200，与该光电转换电路100连接，用于将该电流信号转换为第一差分信号和第二差分信号，该第一差分信号为该电流信号处于该第一相位时的积分信号，该第二差分信号为该电流信号处于该第二相位时的积分信号；该减法放大器300，与该差分信号转换电路200连接，用于将该第一差分信号和该第二差分信号的差值放大，以生成第三差分信号。
其中，本发明实施例所说的有用光信号可以为承载有目标信息(例如，心率数据信息)的光信号，调制光信号可以为用于调制该有用光信号的调制信号，背景光信号可以为该光电转换电路100接收到的环境光形成的信号。换句话说，本发明实施例中该光电转换电路100的输入信号包括有用光信号、调制光信号和背景光信号。应理解，上述对有用光信号、调制光信号和背景光信号的定义为示例性的，本发明实施例不做具体限定。
此外，本发明实施例中的第一相位和第二相位为不同的相位，本发明实 施例对该第一相位和该第二相位的含义不做具体限定。例如，该第一相位可以指：该光电转换电路100用于将该光信号中的有用光信号、调制光信号和背景光信号转换成电流信号时，转换后的电流信号所包含的所有相位；该第二相位可以指：该光电转换电路100只用于将该光信号中的背景光信号转换成电流信号时，转换后的电流信号所包含的所有相位。
由于光电转换电路100输出阻抗非常高，为了将电流信号有效地转换成电压信号，本发明实施例中，通过差分信号转换电路200可以抑制环境中引入的共模噪声。
具体而言，如图2所示，由于电流信号从光电转换电路100的另一端流入，从光电转换电路100的一端流出。因此，对于差分信号转换电路200的输入来说，该电流信号是一个差模量。假设有外部干扰信号同时耦合到Vipi、Vini，该干扰信号是一个共模量。而差分信号转换电路200只允许光电转换电路的电流流过。也就是说，耦合的干扰会被抑制。
即，本发明实施例中的差分信号转换电路200能够有效抑制环境的干扰信号，进而提高输出信号的信噪比。
进一步地，从光电转换电路100到差分信号转换电路200再到减法放大器300的整个转换过程来说，差分信号转换电路200收到光电转换电路输出的电流信号时，抑制环境中引入的共模噪声后，对处于第一相位和第二相位的电流信号分别进行积分，进而获取第一差分信号和第二差分信号。
由于该第一差分信号为该电流信号处于该第一相位时的积分信号，该第二差分信号为该电流信号处于该第二相位时的积分信号；且该电流信号在第一相位包括有用光信号、调制光信号和背景光信号转换后的信号，该光信号在第二相位只包括背景光信号转换后的信号。
因此，如果上述背景光信号为一恒量，则减法放大器300通过放大第一差分信号和该第二差分信号的差值，即可使得减法放大器300输出的差分信号中不涉及背景光信号，进一步提高信噪比。
简而言之，首先，由光电转换电路100产生电流信号，再由差分信号转换电路200获取电流信号在两个相位上的积分差模量(即第一差分信号和第二差分信号)。最后，通过减法放大器300将两个相位的差分信号进行相减，提高输出信号的信噪比。
需要注意的是，本发明实施例中的背景光信号和环境中引入的共模噪声 并不一样。
其中，背景光信号指光电转换电路100采集背景光形成的信号，这里的背景光可以理解为光电转换电路100采集的不是LED光源发出的光而形成的信号，例如，环境光。而工模噪声指不是由光电转换电路100生成的并输入到差分信号转换电路200的噪声信号，例如，心率采集系统中的人体皮肤上的噪声等。
因此，本发明实施例的信号转换电路，不仅能够通过差分信号转换电路200抑制环境中引入的共模噪声，提高输出信号的信噪比，而且有可能使得减法放大器300输出的差分信号中不涉及背景光信号(背景光信号为一恒量时)，进一步提高信噪比，进而提高信号检测的准确度。
可选地，光电转换电路100可以为光敏二极管。
具体地，如图1所示，该光电转换电路100包括一个二极管120和寄生电容110，该二极管120与该寄生电容110并联。其中，该二极管120可以是一个理想的二极管，即正向压降为0，反向漏电流为0的二极管。
应理解，光敏二极管仅作为光电转换电路100的示例性描述，本发明实施例不做具体限定。例如，差分信号转换电路200也可以对来自其它器件的弱电流信号进行积分。
下面对本发明实施例的差分信号转换电路200进行示例性说明。
可选地，该差分信号转换电路200包括：第一差分信号产生电路，用于对处于该第一相位的该电流信号进行积分；第二差分信号产生电路，用于对处于该第二相位的该电流信号进行积分，其中，该第一差分信号产生电路与该第二差分信号产生电路并联。
图2是本发明实施例的差分信号转换电路200的示意图。
如图2所示，该第一差分信号产生电路包括第一积分电路210和第二积分电路220，该第二差分信号产生电路包括第三积分电路230和第四积分电路240，每个积分电路包括一个电容器和一个开关，该差分信号转换电路200还包括：第一开关251、第二开关252和第一跨导放大器290，每个积分电路包括一个电容器和一个开关，该光电转换电路100的一端通过该第一开关251与该第一跨导放大器290的正输入端相连，该光电转换电路100的另一端通过该第二开关252与该第一跨导放大器290的负输入端相连，该第一跨导放大器290的正输入端通过该第一积分电路210连接至该第一跨导放大器 290的负输出端相连，该第一跨导放大器290的负输入端通过该第二积分电路220连接至该第一跨导放大器290的正输出端相连，该第三积分电路230与该第一积分电路210并联，该第四积分电路240与该第二积分电路220并联。
其中，该第一开关251和该第二开关252均导通时，该第一积分电路210和该第二积分电路220用于对处于该第一相位的该电流信号进行积分，并且该第三积分电路230和该第四积分电路240用于对处于该第二相位的该电流信号进行积分。
具体地，如图2所示，第一积分电路210包括第三电容211和第九开关212，第二积分电路220包括第四电容221和第十开关222，第三积分电路230包括第五电容231和第十一开关232，第四积分电路240包括第六电容241和第十二开关242。其中，可以通过第一控制信号(ck1i)控制第一积分电路210中的第九开关212和第二积分电路220中的第十开关222导通或者断开，通过第二控制信号(ck2i)控制第三积分电路230中的第十一开关232和第四积分电路240中的第十二开关242导通或者断开。
更具体地，第一控制信号ck1i＝1(处于高电平)时，第九开关212和第十开关222导通，第一控制信号ck1i＝0(处于低电平)时，第九开关212和第十开关222断开。同样地，第二控制信号ck2i＝1(处于高电平)时，第十一开关232和第十二开关242导通，第二控制信号ck2i＝0(处于低电平)时，第十一开关232和第十二开关242断开。
如图5所示，在差分信号转换电路200实际工作过程中，该第一开关251和该第二开关252导通。当ck1i＝1、ck2i＝0时，第九开关212和第十开关222导通，第十一开关232和第十二开关242断开，该第一积分电路210和该第二积分电路220用于对处于该第一相位的该电流信号进行积分。当ck1i＝0、ck2i＝1时，第九开关212和第十开关222断开，第十一开关232和第十二开关242导通，该第三积分电路230和该第四积分电路240用于对处于该第二相位的该电流信号进行积分。
换句话说，当ck1i＝1、ck2i＝0时，第九开关212和第十开关222导通，第十一开关232和第十二开关242断开，第三电容211和第四电容221对输入的调制光信号、有用光信号和背景光信号进行积分；当ck1i＝0、ck2i＝1时，第九开关212和第十开关222断开，第十一开关232和第十二开关242导通， 第五电容231和第六电容241对输入的背景光信号进行积分。
需要注意的是，假设背景光信号为一恒定不变的量，那么不难看出最后电流信号在两个相位上的积分差模量之差即为有用光信号和调制光信号的积分量，而本发明实施例中，通过减法放大器300完成了这一转换。具体地，当差分信号转换电路200积分完成后，断开第一开关251和第二开关252，即光电转换电路100的输出不再影响积分器。
可选地，该光电转换电路100为光敏二极管，该第一跨导放大器290还用于接收第一电压，该第一电压用于调整该光敏二极管的反偏电压。。
具体而言，如图2所示，较大的寄生电容110(Cpd)会导致第一跨导放大器290自身的噪声被放大。其中，Cpd可以分为扩散电容和势垒电容，由于该光敏二极管反偏，则扩散电容基本上可以忽略。可以发现，由于势垒电容与该光敏二极管的电压成反比。因此，为了获得较低的噪声需要尽可能的增加该光敏二极管的反偏电压。
本发明实施例中，如图2所示，差分信号转换电路200的正负输入端Vipi、Vini分别接到了该光敏二极管的阴极和阳极，此时，通过给第一跨导放大器290输入一个第一电压Vos，即可让该光敏二极管偏置到一个合适的反偏电压，从而减小Cpd的大小，进而提高差分信号转换电路200输出信号的信噪比。
此外，由于本发明实施例中的电流信号包括背景光信号转换后的信号，当背景光信号不是一个恒定不变的量时，可能会导致差分信号转换电路200输入的有效信号的动态范围变小。换句话说，可能使得差分信号转换电路200输出的有效信号(即，减法放大器300输入的有效信号)包括上述背景光信号中残留的信号。
例如，假设背景光信号为一恒定的量，则可以认为：该第一差分信号为差分信号转换电路200在该第一相位仅对调制光信号和有用光信号进行积分形成的差分信号，该第二差分信号为0。
但是，假设背景光信号为一浮动的变量，则可以认为：该第一差分信号为差分信号转换电路200在电流信号的第一相位仅对背景光信号中残留的信号、调制光信号和有用光信号进行积分形成的差分信号，该第二差分信号为差分信号转换电路200在电流信号的第二相位仅对背景光信号中残留的信号进行积分形成的差分信号。
其中，本文中涉及的背景光信号中残留的信号可以指：背景光信号减去一个恒量得到的信号，是一个差模量，是背景光信号中该差分信号转换电路200可以进行积分的光信号。
因此，本发明实施例中，还提供了一种负反馈回路，通过抵消背景光信号中残留的信号来增大差分信号转换电路200输入的有效信号的动态范围。
可选地，该差分信号转换电路200包括：负反馈回路，该负反馈回路用于在该差分信号转换电路200将该电流信号转换为该第一差分信号和该第二差分信号时，抵消背景光信号中残留的信号。
例如，如图2所示，该负反馈回路包括：第三开关253、第四开关254和电流采样电路270，该第一积分电路210通过该第三开关253连接至该第一跨导放大器290的负输出端，该第二积分电路220通过该第四开关254连接至该第一跨导放大器290的正输出端，该第一跨导放大器290的正输出端通过该电流采样电路270连接至该第一跨导放大器290的负输出端；
其中，该第三开关253和该第四开关254断开时，该电流采样电路270用于检测背景光信号中残留的信号，该第三开关253和该第四开关254导通时，该电流采样电路270用于抵消背景光信号中残留的信号。
例如，如图2所示，该电流采样电路270包括：第五开关261、第六开关263、第七开关268、第八开关260、第一电容264、第二电容267、第一金属氧化物半导体管(Metal-Oxide-Semiconductor,MOS)管、第二MOS管265、第三MOS管266和第四MOS管269；该第一跨导放大器290的正输出端通过该第五开关261连接至该第一MOS管262的漏极，该第一MOS管262的漏极和该第一MOS管262的栅极相连，该MOS管的栅极通过该第六开关263连接至该第二MOS管265的栅极，该第一MOS管262的源极与该第二MOS管265的源极相连，该第二MOS管265的栅极通过该第一电容264连接至该第二MOS管265的源极，该第二MOS管265的漏极通过该光电转换电路100连接至该第三MOS管266的漏极，该第三MOS管266的栅极通过该第二电容267连接至该第三MOS管266的源极，该第三MOS管266的栅极通过该第七开关268连接至该第四MOS管269，该第三MOS管266的源极与该第四MOS管269的源极相连，该第四MOS管269的栅极与该第四MOS管269的漏极相连，该第四MOS管269的漏极通过该第八开关260连接至该第一跨导放大器290的负输出端。
其中，第五开关261、第六开关263、第七开关268和第八开关260均导通时，电流采样电路270用于检测所述背景光信号中残留的信号；第五开关261、第六开关263、第七开关268和第八开关260均断开时，电流采样电路270用于抵消所述背景光信号中残留的信号。
具体地，可以通过第三控制信号(shn)控制第三开关253和该第四开关254导通或者断开，通过第四控制信号(shp)控制第五开关261、第六开关263、第七开关268和第八开关260导通或者断开。
更具体地，shn＝1(处于高电平)时，第三开关253和该第四开关254导通，shn＝0(处于低电平)时，第三开关253和该第四开关254断开。同样地，shp＝1(处于高电平)时，第五开关261、第六开关263、第七开关268和第八开关260导通，shp＝0(处于低电平)时，第五开关261、第六开关263、第七开关268和第八开关260断开。
在实际工作中，如图5所示，当shp＝1、shn＝0时，即第三开关253和第四开关254断开，第五开关261、第六开关263、第七开关268和第八开关260导通时，第一跨导放大器290与第一MOS管、第二MOS管265、第三MOS管266、光电转换电路100和第四MOS管269形成负反馈回路，根据放大器续断的原理，电流只能通过从电源通过第二MOS管265、光电转换电路100、第三MOS管266这条支路流向参考地。此时，光电转换电路100仅接收的是背景光信号，因此，流过第二MOS管265和第三MOS管266的电流即为背景光信号中残留的信号产生的电流。
也就是说，只需要shp＝0、shn＝1时使得流过第二MOS管265和第三MOS管266的电流，与shp＝1、shn＝0时流过第二MOS管265和第三MOS管266的电流相等，即可实现差分信号转换电路200在工作状态时，抵消电流信号中的背景光信号中残留的信号。
换句话说，本发明实施例中，可以通过在差分信号转换电路200中加入负反馈回路，进而抵消输入电流中的背景光信号的电流，从而增大差分信号转换电路200输入的有效信号的动态范围。
本领域技术人员可以理解，MOS管也被称为金属氧化物半导体场效应晶体管(Metal-Oxide-Semiconductor Field-Effect Transistor,MOSFET)。其中，MOSFET根据“通道”(工作载流子)的极性不同，可以分为“N型”MOS管(NMOSFET)与“P型”MOS管(PMOSFET)，对于NMOSFET，其源 极和漏极接在N型半导体上，接高压为漏端，接低压为源端，实际电流方向为流入漏极。对于PMOSFET，其源极和漏极则接在P型半导体上，接高压为源端，接低压为漏端，实际电流方向为流出漏极。本发明实施例中，第一MOS管262和第二MOS管265可以为“N型”MOS管，第三MOS管266和第四MOS管269可以为“P型”MOS管。但本发明实施例不限于此。
还应理解，本发明实施例中，由第三开关253、第四开关254和电流采样电路270组成的负反馈回路，旨在用于增大差分信号转换电路200输入的有效信号的动态范围。即，如2所示的电流结构仅为示例性描述，本发明实施例不做具体限定。
此外，由于第一跨导放大器290的输入端有固定的第一电压，若Vipi的电压过高，将会导致第一跨导放大器290中的尾电流源M0被压倒线性区，将会导致差分信号转换电路200工作异常。
因此，进一步地，为了保证差分信号转换电路200处于正常工作状态。
可选地，如图2所示，该差分信号转换电路200包括：第二跨导放大器280，该第二跨导放大器280的正输入端与该第一跨导放大器290的正输入端相连，该第二跨导放大器280的负输入端接收共模电压，该共模电压用于稳定该第一跨导放大器290的正输入端的电压值。
具体地，如图2所示，在电流采样电路270中加入了一个第二跨导放大器280形成了另一个负反馈回路，根据“虚短原理”可知，第一跨导放大器290的正输入端和第二跨导放大器280的正输入端的电压一样，从而将Vipi的电压限制在了一个确定的共模电压Vcm上。进而，通过控制共模电压Vcm能够确保差分信号转换电路200处于正常工作状态。
综上所述，本发明实施例中，差分信号转换电路200通过输入差分电流信号，并输出两个相位的差分信号，由此能够抑制环境中引入的共模噪声。进一步地，通过为第一跨导放大器290输入一个第一电压(例如，正失调电压)，能够进一步提高输出信号的信噪比。更进一步地，通过电流采样电路270能够增大差分信号转换电路200输入的有效信号的动态范围。通过第二跨导放大器280，能够保证差分信号转换电路200处于正常工作状态。
应理解，负反馈回路和第二跨导放大器280构成的负反馈回路属于差分信号转换电路200辅助电路，在实际应用过程中，可以根据实际需求布局电路，本发明实施例不做具体限定。
下面对本发明实施例的减法放大器300进行示例性介绍。
图3是本发明实施例的减法放大器300的示意图。
如图3所示，该减法放大器300包括：第一支路310、第二支路320、第三支路330、第四支路340和第三跨导放大器370，其中，该第一支路310和该第二支路320用于接收该第一差分信号，该第三支路330和该第四支路340用于接收该第二差分信号，该第三跨导放大器370用于根据该第一差分信号和该第二差分信号生成该第三差分信号。
具体地，如图3所示，该第一支路310包括第十三开关311、第七电容312和第十四开关313，该第二支路320包括第十五开关321、第八电容322和第十六开关323，该第三支路330包括第十七开关331、第九电容332和第十七开关333，该第四支路340包括第十八开关341、第十电容342和第十九开关343。其中，如图3所示，第九电容332的一端依次通过第二十开关351和第二十一开关352连接至第七电容312的一端，第九电容332的另一端依次通过第二十二开关353和第二十三开关354连接至第七电容312的另一端，第八电容322的一端依次通过第二十四开关355和第二十五开关356连接至第十电容342的一端、第八电容322的另一端依次通过第二十六开关357和第二十七开关358连接至第十电容342的另一端。
进一步地，第三跨导放大器370的正输入端通过第十一电容361连接时第三跨导放大器370的负输出端，第三跨导放大器370的负输入端通过第十二电容362连接时第三跨导放大器370的正输出端。
其中，第五控制信号(ck1p)用于控制以下开关的导通和断开：
第十三开关311、第十四开关313、第十五开关321、第十六开关323、第二十开关351、第二十二开关353、第二十五开关356和第二十七开关358。
另外，第六控制信号(ck2p)用于控制以下开关的导通和断开：
第十七开关331、第十七开关333、第十八开关341、第十九开关343、第二十一开关352、第二十三开关354相连，第二十四开关355、第二十六开关357。
本发明实施例中，结合差分信号转换电路200转换过程来说，该减法放大器300主要作用是：将差分信号转换电路200输出的第一差分信号和第二差分信号相减并放大得到第三差分信号，然后输出该第三差分信号。进而实现了对电流信号的转换。
具体地，当第五控制信号ck1p＝1(处于高电平)时，控制相应的开关导通，当第五控制信号ck1p＝0(处于低电平)时，控制相应的开关断开；同样地，当第六控制信号ck2p＝1(处于高电平)时，控制相应的开关导通，当第六控制信号ck2p＝0(处于低电平)时，控制相应的开关断开。
假设，Cfp＝Cfn＝Cf、Csp1＝Csp2＝Csn1＝Csn2＝Cs。其中，Cfp表示第十一电容361的电容值，Cfn表示第十二电容362的电容值，Csp1、Csn1、Csp2、Csn2分别表示第七电容312的电容值、第八电容322的电容值、第九电容332的电容值、第十电容342的电容值。
如图5所示，在实际工作过程中，第一开关251和第二开关252断开。当ck1i＝1、ck2i＝0、ck1p＝1、ck2p＝0时，第一差分信号被转换并储存在第十一电容361、第十二电容362中，此时，该减法放大器200的输出可以表示为：Vo,pga(1/2)＝Vopp(1/2)-Vonp(1/2)＝Cs/Cf(Vcp1-Vcn1)。其中，Cs/Cf为放大系数，Vcp1-Vcn1为本发明实施例的第一差分信号。当ck1i＝0、ck2i＝1、ck1p＝0、ck2p＝1时，减法放大器200的输出可以表示为：Vo,pga(1)＝Cs/Cf[(Vcp1-Vcn1)-(Vcp2-Vcn2)]，其中，Vcp2-Vcn2为本发明实施例的第二差分信号。
以此类推，时钟周期N后，该减法放大器300的输出可以表示为：Vo,pga(N)＝N*(Cs/Cf)*[(Vcp1-Vcn1)-(Vcp2-Vcn2)]。由此，通过减法放大器300对将该第一差分信号和该第二差分信号的差值进行放大，进而实现对有用光信号和调制光信号的解调。
应理解，图3所示的电路结构仅为本发明实施例的减法放大器300的示例，本发明实施例不限于此。
图4是本发明实施例的第一跨导放大器290的示意图。
如图4所示，第五MOS管403和第六MOS管404构成了差分输入对管，用于提供所需的跨导量，第七MOS管401为输入对管的尾电流源，用于提供一定的偏置电流。第八MOS管407、第九MOS管408、第十MOS管409和第十一MOS管410构成的自共源共栅MOS管(Self-Cascode MOSFET，SCM)，用于接收差分对输出的电流并且提供一定的输出负载电阻。例如，本发明实施例中的自共源共栅MOS管可以包括两个PMOSFET，当其中一个PMOSFET工作在线性区时，电气特性上可以等效成一个电阻。
此外，第十二MOS管405和第十三MOS管406构成的电流镜也提供 了一定的输出负载电阻，该电阻与该自共源共栅MOS管的等效电阻并联，共同形成跨导放大器的输出电阻。
其中，如图4所示，在节点Vvg与Vs之间设置有第十四MOS管402，当第一跨导放大器290正常工作的时候，流过第五MOS管403和第六MOS管404的电流基本上是相等的，为了保证两路电流相等，必须满足Vip-Vvg＝Vin-Vs，即满足Vip-Vin＝Vvg-Vs。由此使得第一跨导放大器290产生一个恒定的第一电压。
应理解，第一跨导放大器290如图4所示的电路结构，也可以采用现有技术中的跨导放大器的电路结构。即，本发明实施例中的第一跨导放大器290可以是任意一种能够产生一个恒定的第一电压的电路结构。
还应理解，本发明实施例的第二跨导放大器280作用是：第三跨导放大器370的作用是：本发明实施例对其电路结构不做具体限定。
例如，对于第二跨导放大器280，可以在如图4所示的第一跨导放大器290的基础上，将Vvg与Vs短路并移除第十四MOS管402，并将Vbp2与Von短接在一起，并且Vbp2不再与偏置电压相连。
又例如，对于第三跨导放大器370，可以在如图4所示的第一跨导放大器290的基础上，将Vvg与Vs短路并移除第十四MOS管402。
最后，需要注意的是，本发明实施例中的电路还可以包括：复位电路、负反馈回路，使得本发明实施例中涉及的电容的初始态为0，输出共模电压为Vcm。由于复位电路、差分输出的共模负反馈回路并不是本发明的关键。此处不再赘述。还应理解，本发明实施例中的电路还可以包括：模数转换器，与本发明实施例的信号转换电路相连，用于将该信号转换电路输出的模拟信号转化为数字信号。
此外，本发明实施例中还提供了一种包括上述提及的信号转换电路的心率传感器。可选地，该心率传感器还可以包括：模数转换器，与该信号转换电路相连，用于将该信号转换电路输出的模拟信号转化为数字信号。进一步地，还可以包括与该数模转换器相连的数据处理电路，该数据处理电路用于接收该数字信号并进行处理。
本发明实施例中，还提供了一种包括上述心率传感器的电子设备。应理解，该电子设备可以是任一电子设备，例如：该电子设备可以为耳机、手环等智能可穿戴设备；又例如：该电子设备为手机、平板电脑、笔记本电脑、 电脑、MP3以及MP4等。
最后需要说明的是，在本发明实施例和所附权利要求书中使用的术语是仅仅出于描述特定实施例的目的，而非旨在限制本发明实施例。
例如，在本发明实施例和所附权利要求书中所使用的单数形式的“一种”、“所述”和“该”也旨在包括多数形式，除非上下文清楚地表示其他含义。
本领域普通技术人员可以意识到，结合本文中所公开的实施例描述的各示例的部件，能够以电子硬件、或者计算机软件和电子硬件的结合来实现。这些功能究竟以硬件还是软件方式来执行，取决于技术方案的特定应用和设计约束条件。专业技术人员可以对每个特定的应用来使用不同方法来实现所描述的功能，但是这种实现不应认为超出本发明实施例的范围。
所属领域的技术人员可以清楚地了解到，为描述的方便和简洁，上述描述的装置和部件，可以是或者也可以不是物理上分开的。可以根据实际的需要选择其中的部分或者全部部件来实现本发明实施例的目的。
以上内容，仅为本发明实施例的具体实施方式，但本发明实施例的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本发明实施例揭露的技术范围内，可轻易想到变化或替换，都应涵盖在本发明实施例的保护范围之内。因此，本发明实施例的保护范围应以权利要求的保护范围为准。

Claims (13)

  1. 一种信号转换电路，其特征在于，包括：
    光电转换电路(100)，用于将光信号转换成电流信号，所述电流信号在第一相位包括所述光信号中的有用光信号、调制光信号和背景光信号转换后的信号，所述电流信号在第二相位包括所述背景光信号转换后的信号；
    差分信号转换电路(200)，与所述光电转换电路(100)连接，用于将所述电流信号转换为第一差分信号和第二差分信号，所述第一差分信号为所述电流信号处于所述第一相位时的积分信号，所述第二差分信号为所述电流信号处于所述第二相位时的积分信号；
    减法放大器(300)，与所述差分信号转换电路(200)连接，用于将所述第一差分信号和所述第二差分信号相减并将相减的差值放大，以生成第三差分信号。
  2. 根据权利要求1所述的信号转换电路，其特征在于，
    所述差分信号转换电路(200)包括：第一差分信号产生电路，用于对处于所述第一相位的所述电流信号进行积分；第二差分信号产生电路，用于对处于所述第二相位的所述电流信号进行积分，其中，所述第一差分信号产生电路与所述第二差分信号产生电路并联。
  3. 根据权利要求2所述的信号转换电路，其特征在于，
    所述第一差分信号产生电路包括第一积分电路(210)和第二积分电路(220)，所述第二差分信号产生电路包括第三积分电路(230)和第四积分电路(240)，每个积分电路包括一个电容器和一个开关，所述差分信号转换电路(200)还包括：第一开关(251)、第二开关(252)和第一跨导放大器(290)，所述光电转换电路(100)的一端通过所述第一开关(251)与所述第一跨导放大器(290)的正输入端相连，所述光电转换电路(100)的另一端通过所述第二开关(252)与所述第一跨导放大器(290)的负输入端相连，所述第一跨导放大器(290)的正输入端通过所述第一积分电路(210)连接至所述第一跨导放大器(290)的负输出端，所述第一跨导放大器(290)的负输入端通过所述第二积分电路(220)连接至所述第一跨导放大器(290)的正输出端，所述第三积分电路(230)与所述第一积分电路(210)并联，所述第四积分电路(240)与所述第二积分电路(220)并联。
  4. 根据权利要求3所述的信号转换电路，其特征在于，
    所述第一开关(251)和所述第二开关(252)均导通时，所述第一积分电路(210)和所述第二积分电路(220)对处于所述第一相位的所述电流信号进行积分，并且所述第三积分电路(230)和所述第四积分电路(240)对处于所述第二相位的所述电流信号进行积分。
  5. 根据权利要求3或4所述的信号转换电路，其特征在于，
    所述光电转换电路(100)为光敏二极管，所述第一跨导放大器(290)连接第一电压，所述第一电压用于调整所述光敏二极管的反偏电压。
  6. 根据权利要求1至5中任一项所述的信号转换电路，其特征在于，
    所述差分信号转换电路(200)包括：负反馈回路，所述负反馈回路用于在所述差分信号转换电路(200)将所述电流信号转换为所述第一差分信号和所述第二差分信号时，抵消所述背景光信号中残留的信号。
  7. 根据权利要求6所述的信号转换电路，其特征在于，
    所述负反馈回路包括：第三开关(253)、第四开关(254)和电流采样电路(270)，所述第一积分电路(210)通过所述第三开关(253)连接至所述第一跨导放大器(290)的负输出端，所述第二积分电路(220)通过所述第四开关(254)连接至所述第一跨导放大器(290)的正输出端，所述第一跨导放大器(290)的正输出端通过所述电流采样电路(270)连接至所述第一跨导放大器(290)的负输出端；
    其中，所述第三开关(253)和所述第四开关(254)均断开时，所述电流采样电路(270)用于检测所述背景光信号中残留的信号；所述第三开关(253)和所述第四开关(254)均导通时，所述电流采样电路(270)用于抵消所述背景光信号中残留的信号。
  8. 根据权利要求7所述的信号转换电路，其特征在于，
    所述电流采样电路(270)包括：第五开关(261)、第六开关(263)、第七开关(268)、第八开关(260)、第一电容(264)、第二电容(267)、第一金属氧化物半导体MOS管(262)、第二MOS管(265)、第三MOS管(266)和第四MOS管(269)；所述第一跨导放大器(290)的正输出端通过所述第五开关(261)连接至所述第一MOS管(262)的漏极，所述第一MOS管(262)的漏极和所述第一MOS管(262)的栅极相连，所述MOS管的栅极通过所述第六开关(263)连接至所述第二MOS管(265)的栅极，所述 第一MOS管(262)的源极与所述第二MOS管(265)的源极相连，所述第二MOS管(265)的栅极通过所述第一电容(264)连接至所述第二MOS管(265)的源极，所述第二MOS管(265)的漏极通过所述光电转换电路(100)连接至所述第三MOS管(266)的漏极，所述第三MOS管(266)的栅极通过所述第二电容(267)连接至所述第三MOS管(266)的源极，所述第三MOS管(266)的栅极通过所述第七开关(268)连接至所述第四MOS管(269)的栅极，所述第三MOS管(266)的源极与所述第四MOS管(269)的源极相连，所述第四MOS管(269)的栅极与所述第四MOS管(269)的漏极相连，所述第四MOS管(269)的漏极通过所述第八开关(260)连接至所述第一跨导放大器(290)的负输出端。
  9. 根据权利要求8所述的信号转换电路，其特征在于，
    所述第五开关(261)、所述第六开关(263)、所述第七开关(268)和所述第八开关(260)均导通时，所述电流采样电路(270)用于检测所述背景光信号中残留的信号；所述第五开关(261)、所述第六开关(263)、所述第七开关(268)和所述第八开关(260)均断开时，所述电流采样电路(270)用于抵消所述背景光信号中残留的信号。
  10. 根据权利要求3至9中任一项所述的信号转换电路，其特征在于，
    所述差分信号转换电路(200)还包括：第二跨导放大器(280)，所述第二跨导放大器(280)的正输入端与所述第一跨导放大器(290)的正输入端相连，所述第二跨导放大器(280)的负输入端接收共模电压，所述共模电压用于稳定所述第一跨导放大器(290)的正输入端的电压值。
  11. 根据权利要求1至10中任一项所述的信号转换电路，其特征在于，
    所述减法放大器(300)包括：第一支路(310)、第二支路(320)、第三支路(330)、第四支路(340)和第三跨导放大器(370)，其中，所述第一支路(310)和所述第二支路(320)用于接收所述第一差分信号，所述第三支路(330)和所述第四支路(340)用于接收所述第二差分信号，所述第三跨导放大器(370)用于根据所述第一差分信号和所述第二差分信号生成所述第三差分信号。
  12. 一种心率传感器，其特征在于，包括：
    权利要求1至11中任一项所述的信号转换电路。
  13. 一种电子设备，其特征在于，包括：权利要求12所述的心率传感器。
PCT/CN2017/106919 2017-10-19 2017-10-19 信号转换电路、心率传感器和电子设备 WO2019075699A1 (zh)

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