Heart rate data collection

Patent metadata

Field	Value
Publication number	US-9044149-B2
Application number	US-201414290884-A
Country	US
Kind code	B2
Filing date	May 29, 2014
Priority date	Jun 22, 2012
Publication date	Jun 2, 2015
Grant date	Jun 2, 2015

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.

First claim

What is claimed is:

1. A circuit comprising:
a light detector for receiving light and for generating a first electrical signal based on the received light;
a controller for generating one or more first control signals and one or more second control signals;
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 the 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 the 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 the first electrical signal and one or more third control signals generated by the controller.

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.

9. 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.

10. The circuit of claim 9 , 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.

11. 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.

12. 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.

13. 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.

14. The circuit of claim 13 , further including a buffer for buffering the first voltage signal sampled by the first sampling circuit before it is received by the ADC.

15. The circuit of claim 13 , wherein the digital voltage signal is representative of a heartbeat of a user.

16. 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.

17. The circuit of claim 16 , 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.

18. 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 generated by the controller.

19. A device comprising:
the circuit of claim 1 ; and
a light emitter for emitting light toward a region of the skin of a user.

20. The device of claim 19 , further including a driver circuit that powers the light emitter based on one or more third control signals generated by the controller.

21. The device of claim 20 , wherein the third 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.

22. The device of claim 21 , wherei

Assignees

• Fitbit Inc

Inventors

• Richards Peter W
• Elliot Thomas Samuel
• Yuen Shelten Gee Jao

Classifications

• A61B5/0002

  Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network (endoradiosondes A61B5/07) · CPC title

• A61B5/681

  Wristwatch-type devices · CPC title

• A61B5/002

  Monitoring the patient using a local or closed circuit, e.g. in a room or building (A61B5/0017 takes precedence) · CPC title

• A61B5/14552 Primary

  Details of sensors specially adapted therefor · CPC title

• A61B2562/185

  Optical shielding, e.g. baffles · CPC title