Multi-mode LED illumination system

• US 9,544,485 B2
• Filed: 05/27/2015
• Issued: 01/10/2017
• Est. Priority Date: 05/27/2015
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Nelson, Anders, Dorai, Arvind, Conner, Brian Jonathan
• Primary Examiner(s): Pasiewicz, Daniel M
• Application Number:
  US14/723,276
• Publication Number:
  US 20160353531A1
• Time in Patent Office: 594 Days
• Field of Search: 348370-371
• US Class Current: 1/1
• CPC Class Codes: G03B 15/05 Combinations of cameras with electronic flash apparatus; Electronic flash units
• CPC Class Codes: H04N 23/56 provided with illuminating means
• CPC Class Codes: H04N 23/667 Camera operation mode switching, e.g. between still and video, sport and normal or high- and low-resolution modes
• CPC Class Codes: H04N 23/74 by influencing the scene brightness using illuminating means
• CPC Class Codes: H04N 5/33 Transforming infrared radiation cameras or camera modules for generating image signals from infrared radiation H04N23/20; circuitry of SSIS for transforming infrared radiation into image signals H04N25/20
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/385 using flyback topology
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices

Abstract

This application discloses a lighting emitting diode (LED) illumination system that operates at least in a boost mode and a bypass mode. The LED illumination system includes a plurality of LEDs and bypass elements. Each bypass element is coupled in parallel with one or more LEDs, and configured to bypass them selectively in the bypass mode. A boost converter is configured to drive the LEDs. The boost converter includes a boost controller that is configured to enable the boost mode in response to a boost enable signal. In the boost mode, the boost controller is electrically coupled to control the boost converter to drive the LEDs by a boosted drive voltage, and in the bypass mode, the boost controller is deactivated to allow the boost converter to drive a subset of the LEDs by a regular drive voltage that is substantially lower than the boosted drive voltage.

Claims

1. A lighting emitting diode (LED) illumination system that operates in a boost mode and a bypass mode, comprising:

a plurality of LEDs that are coupled in series to form a LED string;

a plurality of bypass elements, each coupled in parallel with a respective group of one or more of the LEDs and configured to bypass selectively the respective group of LEDs in the bypass mode;

a boost converter, coupled to the plurality of LEDs, that is configured to generate a drive voltage to drive the plurality of LEDs, wherein the boost converter includes a boost controller that is configured to enable the boost mode in response to a boost enable signal; and

a first current sink and a second current sink, coupled to the plurality of LEDs, that are configured to provide two drive currents to drive the LEDs in the boost mode and the bypass mode, respectively;

wherein in the boost mode the boost controller is electrically coupled to control the boost converter to drive the LED string by a boosted drive voltage, and in the bypass mode the boost controller is deactivated to allow the boost converter to drive a subset of the plurality of LEDs by a regular drive voltage that is substantially lower than the boosted drive voltage.

2. The LED illumination system of claim 1, further comprising:

a microcontroller unit configured to generate the boost enable signal and a plurality of LED bypass controls, wherein the boost enable signal is applied to control the boost controller and select one of the first and second current sinks, and each of the plurality of LED bypass controls is applied to control one of the plurality of bypass elements for bypassing the corresponding group of LEDs in the bypass mode.

3. The LED illumination system of claim 1, wherein each of the plurality of LEDs is coupled in parallel with a respective bypass element configurable to bypass the respective LED in the bypass mode.

4. The LED illumination system of claim 1, wherein the plurality of LEDs includes eight LEDs, and wherein in the bypass mode, six of the eight LEDs are bypassed, and two remaining LEDs are coupled in series between the boost converter and the second current sink.

5. The LED illumination system of claim 1, wherein the plurality of LEDs is disposed in a camera module to surround a camera lens, and each LED is tilted with an angle with respect to the optical axis of the camera lens.

6. The LED illumination system of claim 5, wherein each LED is tilted away from the optical axis of the camera with the angle in the range of 20-40 degrees.

7. The LED illumination system of claim 1, wherein the plurality of LEDs includes infrared LEDs.

8. The LED illumination system of claim 1, wherein the plurality of LEDs is grouped into four subsets of LEDs that are configured to illuminate four quadrants of a field of view, respectively, and depth information of the field of view is recovered at night time according to the variation of the field of view illuminated by these four subsets of LEDs.

9. The LED illumination system of claim 1, wherein when the LED illumination system switches from the boost mode to the bypass mode, both the boost controller and the first current sink are deactivated, and the second current sink is electrically coupled to the whole LED string for at least a predetermined discharge period, before the subset of the plurality of LEDs are electrically coupled and biased by the regular drive voltage.

10. The LED illumination system of claim 9, wherein the predetermined discharge period is substantially equal to or longer than 40 msec.

11. The LED illumination system of claim 9, wherein the subset of the plurality of LEDs includes a first subset of LEDs, and a second subset of the plurality of LEDs is electrically coupled to the boost converter during the predetermined discharge period, the second subset of LEDs including more LEDs than the first subset of LEDs.

12. The LED illumination system of claim 1, wherein in the boost mode, the first current sink is electrically coupled to the whole LED string and enables a first drive current, and in the bypass mode, the second current sink is electrically coupled to the subset of the plurality of LEDs and enables a second drive current.

13. The LED illumination system of claim 12, wherein the first and second drive currents are distinct.

14. The LED illumination system of claim 1, wherein the first current sink is part of the boost controller.

15. The LED illumination system of claim 1, wherein the boost converter, the boost controller, and the first and second current sinks are integrated on an integrated circuit substrate.

16. The LED illumination system of claim 1, wherein the voltage level of the regular drive voltage is substantially equal to that of a power supply of the LED illumination system.

17. A camera device that operates in two or more modes, comprising:

a camera portion; and

a LED illumination system that operates in a boost mode and a bypass mode associated respectively with a first mode and a second mode of the two or more modes of the camera device, including;

a plurality of LEDs that are coupled in series to form a LED string;

a plurality of bypass elements, each coupled in parallel with a respective group of one or more of the LEDs and configured to bypass selectively the respective group of LEDs in the bypass mode;

a boost converter, coupled to the plurality of LEDs, that is configured to generate a drive voltage to drive the plurality of LEDs, wherein the boost converter includes a boost controller that is configured to enable the boost mode in response to a boost enable signal; and

a first current sink and a second current sink, coupled to the plurality of LEDs, that are configured to provide two drive currents to drive the LEDs in the boost mode and the bypass mode, respectively;

wherein in the boost mode the boost controller is electrically coupled to control the boost converter to drive the LED string by a boosted drive voltage, and in the bypass mode the boost controller is deactivated to allow the boost converter to drive a subset of the plurality of LEDs by a regular drive voltage that is substantially lower than the boosted drive voltage.

18. A method of manufacturing a LED illumination system that operates in a boost mode and a bypass mode, comprising:

providing a plurality of LEDs that are coupled in series to form a LED string;

providing a plurality of bypass elements, including coupling each of the plurality of bypass elements in parallel with a respective group of one or more of the LEDs to bypass selectively the respective group of LEDs in the bypass mode;

coupling a boost converter to the plurality of LEDs, the boost converter being configured to generate a drive voltage to drive the plurality of LEDs, wherein the boost converter includes a boost controller that is configured to enable the boost mode in response to a boost enable signal; and

wherein in the boost mode the boost controller is electrically coupled to control the boost converter to drive the LED string by a boosted drive voltage, and in the bypass mode the boost controller is deactivated to allow the boost converter to drive a subset of the plurality of LEDs by a regular drive voltage that is substantially lower than the boosted drive voltage.

19. The method of claim 18, further comprising:

providing a first current sink and a second current sink, coupled to the plurality of LEDs, that are configured to provide two drive currents to drive the LEDs in the boost mode and the bypass mode, respectively.

20. The method of claim 18, further comprising:

providing a microcontroller unit that is configured to generate the boost enable signal and a plurality of LED bypass controls, wherein the boost enable signal is applied to control the boost controller and select one of the first and second current sinks, and each of the plurality of LED bypass controls is applied to control one of the plurality of bypass elements for bypassing the corresponding group of LEDs in the bypass mode.