HEART RATE DATA COLLECTION

• US 20140288435A1
• Filed: 05/29/2014
• Published: 09/25/2014
• Est. Priority Date: 06/22/2012
• Status: Active Grant

• Current Assignee: Fitbit, Inc. (Alphabet Inc.)
• Original Assignee: Fitbit, Inc. (Alphabet Inc.)
• Inventors: Richards, Peter W., Yuen, Shelten Gee Jao, Elliot, Thomas Samuel
• Granted Patent: US 9,044,149 B2
• Time in Patent Office: Days
• US Class Current: 600/479
• CPC Class Codes: A61B 2562/185 Optical shielding, e.g. baffles
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/002 Monitoring the patient using a local or closed circuit, e.g. in a room or building A61B5/0017 takes precedence
• CPC Class Codes: A61B 5/0022 Monitoring a patient using a global network, e.g. telephone networks, internet
• CPC Class Codes: A61B 5/0205 Simultaneously evaluating both cardiovascular conditions and different types of body conditions, e.g. heart and respiratory condition
• CPC Class Codes: A61B 5/021 Measuring pressure in heart or blood vessels A61B5/0205 takes precedence
• CPC Class Codes: A61B 5/02405 Determining heart rate variability
• CPC Class Codes: A61B 5/02416 using photoplethysmograph signals, e.g. generated by infrared radiation A61B5/14552 takes precedence
• CPC Class Codes: A61B 5/02427 Details of sensor
• CPC Class Codes: A61B 5/02433 for infrared radiation
• CPC Class Codes: A61B 5/02438 with portable devices, e.g. worn by the patient
• CPC Class Codes: A61B 5/0816 Measuring devices for examining respiratory frequency measuring frequency of electric signals G01R23/00
• CPC Class Codes: A61B 5/1123 Discriminating type of movement, e.g. walking or running A61B5/1116, A61B5/112 take precedence
• CPC Class Codes: A61B 5/14532 for measuring glucose, e.g. by tissue impedance measurement
• CPC Class Codes: A61B 5/14539 for measuring pH
• CPC Class Codes: A61B 5/14552 Details of sensors specially adapted therefor
• CPC Class Codes: A61B 5/4812 Detecting sleep stages or cycles
• CPC Class Codes: A61B 5/4815 Sleep quality
• CPC Class Codes: A61B 5/681 Wristwatch-type devices
• CPC Class Codes: A61B 5/7203 for noise prevention, reduction or removal
• CPC Class Codes: A61B 5/7225 : Details of analog processing, e.g. isolation amplifier, gain or sensitivity adjustment, filtering, baseline or drift compensation A61B5/30, A61B5/316 take precedence; transformers for specific applications H01F38/00; amplifiers H03F
• CPC Class Codes: H04L 67/12 : specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks
• CPC Class Codes: H04W 4/027 : using movement velocity, acceleration information
• CPC Class Codes: H04W 4/80 : Services using short range communication, e.g. near-field communication [NFC], radio-frequency identification [RFID] or low energy communication

Abstract

One innovative aspect is directed to heart rate data collection. In some implementations, a circuit includes a light detector for generating a first electrical signal based on received light. The circuit includes a switching circuit, having a first and a second configuration, configured to receive a first voltage signal based on the first electrical signal and to switch among the first and the second configurations. The circuit includes first and second sampling circuits for sampling a value of the first voltage signal when the switching circuit is in the first configuration and second configurations, respectively. The circuit includes an ambient light cancellation circuit for generating a current signal to counter a first component of the first electrical signal when the first switching circuit is in the first configuration.

Claims

1. A circuit comprising:

a light detector for receiving light and for generating a first electrical signal based on the received light;

a first switching circuit having at least a first configuration and a second configuration, the first switching circuit for;

receiving a first voltage signal based on the first electrical signal,

receiving one or more first control signals;

switching among at least the first configuration and the second configuration based on the one or more first control signals;

a first sampling circuit for sampling a value of the first voltage signal when the first switching circuit is in the first configuration;

a second sampling circuit for sampling a value of the first voltage signal when the first switching circuit is in the second configuration; and

an ambient light cancellation circuit for generating a first current signal to at least partially counter a first component of the first electrical signal when the first switching circuit is in the first configuration, the first current signal being based on one or more second control signals and the value of the first voltage signal sampled by the second sampling circuit.

2. The circuit of claim 1, further including an adjustable gain circuit for setting a second current signal to adjust a gain of the first voltage signal relative to the first electrical signal when the first switching circuit is in the first configuration, the second current signal being based on one or more third control signals and the first electrical signal.

3. The circuit of claim 2, wherein:

the first electrical signal is a current signal;

the circuit further includes an electrical current-to-voltage converter for converting the first electrical signal to a second voltage signal;

the first voltage signal is based on the second voltage signal;

the adjustable gain circuit sets the second current signal to adjust a gain of the second voltage signal relative to the first electrical signal when the first switching circuit is in the first configuration, the second current signal being based on the one or more third control signals and the second voltage signal; and

the ambient light cancellation circuit generates the first current signal such that the first current signal has an opposite polarity as the first electrical signal to at least partially counter the first component of the first electrical signal when the first switching circuit is in the first configuration.

4. The circuit of claim 3, wherein the current-to-voltage converter and the adjustable gain circuit form a transimpedance amplifier.

5. The circuit of claim 4, wherein the current-to-voltage converter includes a first operational amplifier having a first input terminal, a second input terminal and an output terminal;

the first input terminal being electrically coupled with a first terminal of the light detector and a first terminal of the adjustable gain circuit;

the second input terminal being electrically coupled with a reference voltage, the output terminal being electrically coupled with a second terminal of the adjustable gain circuit, the output terminal also for outputting the second voltage signal.

6. The circuit of claim 5, wherein the adjustable gain circuit includes an adjustable impedance stage between the first terminal of the adjustable gain circuit and the second terminal of the adjustable gain circuit for providing an adjustable impedance to adjust the second current signal based on the one or more third control signals.

7. The circuit of claim 6, wherein:

the adjustable impedance stage includes an impedance network having at least a first impedance path having a first impedance, and a second impedance path having a second impedance; and

the adjustable gain circuit further includes a second switching circuit for selecting among at least the first impedance path and the second impedance path based on the one or more third control signals.

8. The circuit of claim 3, further including a buffer for buffering the second voltage signal to generate the first voltage signal.

11. The circuit of claim 1, wherein the ambient light cancellation circuit includes an adjustable impedance stage between a first terminal of the ambient light cancellation circuit and a second terminal of the ambient light cancellation circuit for providing an adjustable impedance to adjust the first current signal based on the one or more second control signals.

12. The circuit of claim 11, wherein:

the adjustable impedance stage includes an impedance network having at least a first impedance path having a first impedance, and a second impedance path having a second impedance; and

the ambient light cancellation circuit further includes a second switching circuit for selecting among at least the first impedance path and the second impedance path based on the one or more second control signals.

13. The circuit of claim 1, wherein the first sampling circuit includes a first sample-and-hold (S/H) circuit for:

receiving the first voltage signal;

sampling a value of the first voltage signal; and

storing the sampled value for a time interval in between consecutive samples.

15. The circuit of claim 1, wherein the second sampling circuit includes a second sample-and-hold (S/H) circuit for:

receiving the first voltage signal;

sampling a value of the first voltage signal; and

storing the sampled value for a time interval in between consecutive samples.

17. The circuit of claim 1, further including an analog-to-digital converter (ADC) for generating a digital voltage signal based on the first voltage signal sampled by the first sampling circuit.

18. The circuit of claim 17, further including a buffer for buffering the first voltage signal sampled by the first sampling circuit before it is received by the ADC.

21. The circuit of claim 1, further including a buffer for buffering the first voltage signal sampled by the second sampling circuit before it is received by the ambient light cancellation circuit.

22. The circuit of claim 21, wherein the buffer is configured to output the first voltage signal sampled by the second sampling circuit to the ambient light cancellation circuit only when an enable signal is received, the enable signal being asserted at least when the first switching circuit is in the first configuration.

24. The circuit of claim 1, further including a second switching circuit, the first terminal of the light detector being electrically coupled with the second switching circuit, the second switching circuit for coupling the first terminal of the light detector to a voltage reference based on one or more third control signals.

25. The circuit of claim 1, further including a microcontroller for generating the first and the second control signals.

26. A device comprising:

the circuit of claim 1; and

a light emitter for emitting light toward a region of the skin of a user.

27. The device of claim 26, further including a driver circuit that powers the light emitter based on one or more second control signals.

28. The device of claim 27, wherein the second control signals cause the driver circuit to turn on the light emitter during an interval of time when the first switching circuit is in the first configuration.

29. The device of claim 28, wherein the second control signals cause the driver circuit to turn off the light emitter after the first sampling circuit has sampled the first voltage signal and prior to the first switching circuit switching into the second configuration.

30. The device of claim 27, wherein the driver circuit includes:

a second operational amplifier having a first input terminal, a second input terminal and an output terminal;

a digital to analog converter (DAC) electrically coupled with the first input terminal of the second operational amplifier for providing an input signal to the first input terminal of the second operational amplifier;

a power supply rail for providing power to a first terminal of the light emitter;

a transistor having a gate terminal, a drain terminal and a source terminal, the gate terminal being electrically coupled with the output terminal of the second operational amplifier, the drain terminal being electrically coupled with a second terminal of the light emitter, and the source terminal being electrically coupled with a reference voltage, the source terminal being further electrically coupled with the second input terminal of the second operational amplifier for providing a feedback signal to the second operational amplifier;

a capacitor electrically coupled between the output terminal of the second operational amplifier and the second input terminal of the second operational amplifier; and

a resistor electrically coupled between the source terminal and the reference voltage, wherein the second operational amplifier is configured to maintain a substantially constant voltage across the resistor based on the feedback signal during operation of the circuit.

31. The device of claim 26, wherein the light emitter and the circuit of claim 1 are arranged at least partially within a housing wearable by the user.

9. (canceled)

10. (canceled)

14. (canceled)

16. (canceled)

19. (canceled)

20. The circuit of claim 19, wherein the digital voltage signal is representative of a heartbeat of a user.

23. (canceled)

32. A method comprising:

turning off or disabling, by a controller, a light emitter;

causing, by the controller, a switching circuit to transition from a first configuration to a second configuration to disable a first sampling circuit and to enable a second sampling circuit to sample a first detected signal;

detecting, by a light detector, an ambient light signal;

generating, by the light detector, the first detected signal based on the ambient light signal;

sampling, by the second sampling circuit, the first detected signal;

storing, by the second sampling circuit, a charge proportional to the sampled first detected signal;

turning on or enabling, by the controller, the light emitter to emit an emitted light signal;

causing, by the controller, the switching circuit to transition from the second configuration to the first configuration to enable the first sampling circuit to sample a second detected signal;

detecting, by the light detector, an incident light signal including an emitted component from the emitted light signal and an ambient component from the ambient light signal;

generating, by the light detector, the second detected signal based on the incident light signal;

causing, by the controller, the second sampling circuit to transfer the stored charge to an ambient light cancellation circuit;

generating, by the ambient light cancellation circuit, a countering signal based on the charge received from the second sampling circuit to counter at least a portion of an ambient component of the second detected signal;

sampling, by the second sampling circuit, the second detected signal while the ambient component is countered; and

outputting an output signal based on the sampled second detected signal.

33. The method of claim 32, further including:

storing, by the second sampling circuit, the sampled second detected signal;

digitizing, by an analog-to-digital converter, the sampled second detected signal to output the output signal.

34. The method of claim 32, further including causing, by the controller, an adjustable gain circuit to:

adjust or select an impedance; and

generate the a gain adjustment signal to adjust a gain of the second detected signal.

35. The method of claim 32, further including decoupling the light detector from a reference voltage to enable the light detector to generate the second detected signal.

36. The method of claim 32, further including coupling the light detector to a reference voltage such that charge that would otherwise accumulate in the light detector due to ambient light can be drained away.