Methods and apparatuses for operating devices with solar power

• US 8,004,113 B2
• Filed: 10/06/2006
• Issued: 08/23/2011
• Est. Priority Date: 10/06/2006
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Warren, Daniel A., Sander, Wendell B., Leiba, Aaron
• Primary Examiner(s): Fureman; Jared J
• Assistant Examiner(s): CAVALLARI, DANIEL J
• Application Number:
  US11/544,103
• Publication Number:
  US 20080084117A1
• Time in Patent Office: 1,782 Days
• Field of Search: 307/43, 307/46, 307/151, 320/103, 320/101, 320/148, 323/285, 323/282, 323/284
• US Class Current: 307/46
• CPC Class Codes: H02J 7/35 with light sensitive cells
• CPC Class Codes: Y02E 10/56 Power conversion systems, e.g. maximum power point trackers

Abstract

Solar power tracking techniques are described herein. In one aspect of the invention, a solar power tracking apparatus includes, but is not limited to, a voltage converter and a controller coupled to the voltage converter. The voltage converter includes an input capable of being coupled to a solar power source and an output capable of being coupled to an electronic load, such as, for example, a portable electronic device. The voltage converter is configured to monitor or detect an amount of power drawn by the electronic load at the output of the voltage converter. In response to the monitored power drawn, the controller is configured to control the voltage converter to reduce amount of power to be drawn subsequently if the monitored amount of power exceeds a predetermined threshold. As a result, the output voltage from the solar power source is maintained within a predetermined range. Other methods and apparatuses are also described.

Claims

1. An apparatus for operating a portable electronic device, comprising:

a voltage converter having an input and an output, wherein the input is capable of being coupled to a solar power source and the output is capable of being coupled to a portable electronic device, and wherein the voltage converter is configured to convert solar power received from the solar power source to power the portable electronic device; and

a controller coupled to the voltage converter to monitor power drawn at the output of the voltage converter based on an average amount of current drawn by the portable electronic device and a voltage of the portable electronic device,

wherein the controller controls the voltage converter to adjust output power in response to the monitored power,

wherein the controller is configured with a current-voltage relationship characteristic of the solar power source, the characteristic specifying voltage operating points for the solar power source, the voltage operating points including stable operating points indicating a stable mode for the solar power source and unstable operating points indicating an unstable mode for the solar power source, the solar power source in the unstable mode collapsing with a constant current and a sharp drop of voltage,

wherein the controller causes the solar power source to operate in the stable mode to allow the solar power to reach a maximum power indicated in the characteristic without the solar power source operating in the unstable mode,

wherein the controller determines whether the solar power source generates the maximum power based on the monitored power, and

wherein the controller maintains the solar power source in the stable mode within a predetermined range indicated in the characteristic, the predetermined range including a voltage threshold to prevent the sharp drop of the voltage of the solar power source.

2. The apparatus of claim 1, further comprising a current sensing device coupled to the output of the voltage converter, wherein the controller is configured to control the voltage converter based on amount of current drawn by the portable electronic device and detected by the current sensing device.

3. The apparatus of claim 1, wherein the voltage converter comprises a power switching device and a switching regulator, the switching regulator controlling the power switching device to switch in order to provide controlled power to the portable electronic device, and wherein the controller is configured to provide a control signal to the switching regulator based on the monitored power, which in turn controls the power switching device.

4. The apparatus of claim 3, wherein the controller is a programmable controller having one or more instructions stored therein, when executed by the controller, cause the controller to generate a control signal to control the voltage converter based on the monitored power using a predetermined algorithm.

5. The apparatus of claim 4, wherein the switching regulator is a pulse width modulator (PWM), wherein the control signal provided by the controller provides a feedback to the PWM to adjust a duty cycle of the power switching device, which in turn adjust an output of the voltage converter.

6. The apparatus of claim 5, wherein the power switching device comprises a first switching device in parallel with the output of the voltage converter and a second switching device in series of the output of the voltage converter, wherein the PWM is configured to alternately turn on one of the first and second switching devices.

7. The apparatus of claim 1, further comprising a capacitor coupled to the input of the voltage converter to temporarily store energy derived from the solar power source during a switching period in order to maintain an input current of the voltage converter relatively constant.

8. The apparatus of claim 1, wherein the portable electronic device is a device selected from a group consisting of:

a media player;

a notebook or tablet computer;

a cellular phone;

a digital camera; and

a personal digital assistant (PDA) or handheld device.

9. A portable electronic device, comprising:

a processor;

a memory coupled to the processor for storing instructions, when executed from the memory, cause the processor to perform one or more functions of the portable electronic device;

a battery coupled to provide power to the processor and the memory;

a battery charger coupled to the battery for charging the battery;

one or more solar cells;

a solar power circuit coupled to the one or more solar cells and the battery charger to charge the battery using solar power derived from the one or more solar cells, the solar power circuit including

a voltage converter having an input and an output, wherein the input is capable of being coupled to a solar power source and the output is capable of being coupled to a portable electronic device, and wherein the voltage converter is configured to convert solar power received from the solar power source to power the portable electronic device; and

a controller coupled to the voltage converter to monitor power drawn at the output of the voltage converter based on an average amount of current drawn by the portable electronic device and an voltage of the portable electronic device,

wherein the controller controls the voltage converter to adjust output power in response to the monitored power,

wherein the controller is configured with a current-voltage relationship characteristic of the solar power source, the characteristic specifying voltage operating points for the solar power source, the voltage operating points including stable operating points indicating a stable mode for the solar power source and unstable operating points indicating an unstable mode for the solar power source, the solar power source in the unstable mode collapsing with a constant current and a sharp drop of voltage,

wherein the controller causes the solar power source to operate within the stable operating points to allow the solar power to reach a maximum power indicated in the characteristic without the solar power source operating in the unstable mode,

wherein the controller determines whether the solar power source generates the maximum power based on the monitored power, and

wherein the controller maintains the solar power source in the stable mode within a predetermined range indicated in the characteristic, the predetermined range including a voltage threshold to prevent the sharp drop of the voltage of the solar power source.

10. The portable electronic device of claim 9, wherein the solar power circuit further comprises a current sensing device coupled to the output of the voltage converter, wherein the controller is configured to control the voltage converter based on amount of current drawn by the portable electronic device and detected by the current sensing device.

11. The portable electronic device of claim 9, wherein the solar power circuit further comprises a power switching device and a switching regulator, the switching regulator controlling the power switching device to switch in order to provide regulated power to the portable electronic device, and wherein the controller is configured to provide a control signal to the switching regulator based on the monitored power, which in turn controls the power switching device.

12. The portable electronic device of claim 11, wherein the controller is a programmable controller having one or more instructions stored therein, when executed by the controller, cause the controller to generate a control signal to control the voltage converter based on the monitored power using a predetermined algorithm.

13. The portable electronic device of claim 12, wherein the switching regulator is a pulse width modulator (PWM), wherein the control signal provided by the controller provides a feedback to the PWM to adjust a duty cycle of the power switching device, which in turn adjust an output of the voltage converter.

14. The portable electronic device of claim 13, wherein the power switching device comprises a first switching device in parallel with the output of the voltage converter and a second switching device in series of the output of the voltage converter, wherein the PWM is configured to alternately turn on one of the first and second switching devices.

15. The portable electronic device of claim 9, wherein the solar power circuit further comprises a capacitor coupled to the input of the voltage converter to temporarily store energy derived from the solar power source during a switching period in order to maintain an input current of the voltage converter relatively constant.

16. The portable electronic device of claim 9, wherein the portable electronic device is a device selected from a group consisting of:

a media player;

a notebook or tablet computer;

a cellular phone;

a digital camera; and

a personal digital assistant (PDA) or handheld device.

17. An apparatus for operating a portable electronic device with solar power, comprising:

means for generating regulated power via a voltage converter to power a portable electronic device based on solar power derived from a solar power source;

means for monitoring power drawn at an output of the voltage converter by the portable electronic device based on an average amount of current drawn by the portable electronic device and a voltage of the portable electronic device;

in response to the monitored power, means for controlling the voltage converter to adjust regulated power to the portable electronic device;

means for configuring a current-voltage relationship characteristic of the solar power source, the characteristic specifying voltage operating points for the solar power source, the voltage operating points including stable operating points indicating a stable mode for the solar power source and unstable operating points indicating an unstable mode for the solar power source, the solar power source in the unstable mode collapsing with a constant current and a sharp drop of voltage;

means for causing the solar power source to operate within the stable mode to allow the solar power to reach a maximum power indicated in the characteristic without the solar power source operating in the unstable mode;

means for determining, based on the monitored power, whether the solar power source generates the maximum power indicated in the current-voltage relationship characteristic of the solar power source; and

means for maintaining the solar power source in the stable mode within a predetermined range indicated in the characteristic, the predetermined range including a voltage threshold to prevent the sharp drop of the voltage from the solar power source.