Power profile sequencing for fast transition to operational state

Abstract

Disclosed herein are electronic systems, devices, and methods for rapidly transitioning to a functional state from a low power state. Aspects of the disclosure are directed to using a photovoltaic (PV) cell to deliver power to an energy storage system after the energy storage system has been depleted to the extent that electrical components are no longer operational. Techniques are disclosed for transitioning an electronic system or device through a sequence of power stages to incrementally recover from a low power state. The power stages can be configured such that increasing levels of functionality are enabled with each subsequent stage. The techniques disclosed herein can be applied to create an integrated power recovery solution for battery-free devices or devices that do not require an external charger.

Description

POWER PROFILE SEQUENCING FOR FAST TRANSITION TO OPERATIONAL STATEINCORPORATION BY REFERENCE

[0001] A PCT Request Form is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed PCT Request Form is incorporated by reference herein in their entireties and for all purposes.TECHNICAL FIELD

[0002] The present disclosure relates generally to electronic systems that use rechargeable energy storage elements for supplying power to system components. In particular, aspects of the disclosure are directed to electronic devices that are powered using energy transferred to a storage element from a photovoltaic cell.BACKGROUND

[0003] Electronic devices can consume a significant amount of power. Many electronic devices, especially those that are portable, rely on battery power. Traditional batteries are disposable devices that contain harmful chemicals. Rechargeable batteries are an environmentally friendlier alternative, and some electronic devices include an integrated rechargeable battery' that is not user replaceable. Uninterrupted use of an electronic device is difficult to achieve when relying on battery power. In the case of a disposable battery, the user needs to have a replacement battery readily available. Rechargeable batteries, whether disposable or integrated, tend to require long charging times (e.g., several hours) before the battery' has enough energy to operate the electronic device. In this respect, rechargeable batteries are worse than disposable batteries because the user may need to locate a separate charger and keep the charger connected to the electronic device for an extended period. During this time, the user is often unaware of when the electronic device will become ready to use. Consequently, the user may disconnect the charger too early or keep the charger connected for longer than needed. In either situation, the electronic device cannot be operated until the battery is sufficiently charged.BRIEF DESCRIPTION OF THE DRAWINGS

[0004] The above and other aspects and features of the disclosure will become more apparent in view of the following detailed description when taken in conjunction with the accompanying drawings, wherein like reference numerals identify like elements.

[0005] FIG. 1 is a simplified block diagram of an electronic system, according to certain embodiments.

[0006] FIG. 2 is a more detailed block diagram of the system in FIG. 1.

[0007] FIG. 3 shows an example of a specific implementation of the system in FIG. 1.

[0008] FIG. 4 is a flow diagram showing an example process for performing power sequencing, according to certain embodiments.

[0009] FIG. 5 is a flow diagram showing an example process for recovering from a low power state, according to certain embodiments.DETAILED DESCRIPTION

[0010] Disclosed herein are examples of electronic systems, devices, and corresponding methods for rapidly transitioning to a functional state from a low pow er state. In particular, aspects of the disclosure are directed to using a photovoltaic (PV) cell to deliver power to an energy storage system after the energy storage system has been depleted to the extent that electrical components are no longer operational. This can occur, for example, when one or more storage elements in energy storage system are discharged below7a required operating voltage. Additionally, techniques are disclosed for transitioning an electronic system or device through a sequence of power stages to incrementally recover from a low power state. The power stages can be configured such that increasing levels of functionality are enabled with each subsequent stage. The PV cell can be used as the main power source or, in some instances, the only power source in the electronic system or device. Accordingly, the techniques disclosed herein can be applied to create an integrated power recovery solution for battery-free devices or devices that do not require an external charger.

[0011] FIG. 1 is a simplified block diagram of an electronic system 100, according to certain embodiments. The system 100 can be implemented as a single electronic device or as separate components that are electrically coupled to each other. Thus, the components depicted in FIG. 1 may be disposed in a shared housing, e.g., on the same circuit board inside a device enclosure. However, the components can be combined or separated such that the features described withrespect to these components are distributed differently than shown in FIG. 1. The system 100 includes a PV cell 110, an energy harvesting system 120, an energy storage system 130, a power supply system 140, a load system 150, and a power management controller (PMC) 160.

[0012] PV cell 110 operates as an energy harvesting element of the system 100. Although only one PV cell is shown, the system 100 can include multiple PV cells, e.g.. two or more cells arranged in a one-dimensional or two-dimensional array. The PV cell 110 can be implemented using any of a variety of photovoltaic cell technologies. In some embodiments, the PV cell 110 is a thin-film solar cell. Thin-film solar cells are typically formed through depositing one or more layers (thin films) of photovoltaic material onto a substrate, using semiconductor device manufacturing methods. Thin-film solar cells include dye-sensitized solar cells (DSSCs). also referred to as dye-sensitized photovoltaic cells. DSSCs are a lower-cost alternative to traditional PV cells, which are non-dye sensitized and usually formed on a rigid, glass or metal substrate. In comparison, DSSCs can be manufactured with less expense (e.g., with a lesser quantity of platinum or other noble metals) and on a greater variety of substrates such as plastic or other flexible materials.

[0013] The components of the electronic system 100 can include hardware and / or software that run on electrical power supplied by one or more power sources. In the example of FIG. 1, the PV cell 110 operates as the power source so that the system 100 relies exclusively on energy generated by the PV cell 110 from natural or artificial light. Of course, not all electronic systems can be operated only using solar power. For example, a personal computer may need to be plugged into an electrical outlet, either continuously or periodically to recharge an internal battery'. However, systems that are less power demanding can be run on solar power. A remote control is one example. In more power intensive applications, the PV cell 110 may be used as a supplemental power source while still providing the benefits described herein. Specifically, the energy generated by the PV cell 110 can be applied to bring the system 100 back to at least partial functionality7in the event of power loss, e.g., when the energy storage system 130 is fully depleted or depleted to the point where the system 100 can no longer be operated. As discussed below, recovery from a low power state can be performed under the control of the PMC 160 and may involve harvesting energy from the PV cell 1 10, routing the harvested energy to one or more storage elements in the energy storage system 130, and delivering the stored energy to the load system 150 in stages.

[0014] Energy harvesting system 120 is configured to transfer energy produced by the PV cell 110 to the energy’ storage system 130. The energy harvesting system 120 can be controlled tomaintain the PV cell 110 at or near its peak energy efficiency. For example, the PMC 160 may be configured to perform maximum power point tracking (MPPT) to direct the energy harvesting system 120 to collect energy at select times. A PV cell can only produce a finite amount of power at any given time. The power output by a PV cell is characterized by the instantaneous voltage and current produced by the PV cell in response to ambient light (e.g.. sunlight or an artificial light source). Each PV cell has a maximum power point (MPP) representing the bias potential or voltage at which the PV cell outputs its highest attainable power. In most PV cells, the MPP voltage varies based on the amount of light received at any given time. In a DS SC, the MPP voltage may be substantially fixed, e.g., at approximately 0.75 volts. Accordingly, the PMC 160 may perform MPPT to maintain the PV cell 110 at or near its MPP voltage by selectively coupling and decoupling the PV cell from a component receiving energy from the PV cell, e.g., the energy storge system 130.

[0015] Energy storage system 130 is configured to store the energy transferred from the PV cell 110 by the energy harvesting system 120. The energy storage system 130 can include one or more storage elements. As discussed above, rechargeable batteries have certain disadvantages. Therefore, the energy storage system 130 preferably includes at least one storage element that is not a rechargeable battery7. For instance, in some embodiments, the energy storage system 130 is formed using a capacitive storage element such as an electrolytic capacitor and / or a supercapacitor. Supercapacitors have a storage capacity between that of electrolytic capacitors and rechargeable batteries. Although supercapacitors have lower storage capacity than rechargeable batteries, they can be charged faster than rechargeable batteries. There are various types of supercapacitors which differ with respect to their storage mechanism. Some supercapacitors are charged electrostatically (e.g., electric double-layer capacitors), others electrochemically (e.g.. pseudocapacitors), and still others both electrostatically and electrochemically (e g., hybrid capacitors). Although the energy storage system 130 may include non-battery elements, this does not preclude the use of batteries with the system 100. For example, the energy7storage system 130 may include a capacitor and a rechargeable (e.g., lithium-ion) battery7. Thus, the energy storage system 130 may include a mix of different types of energy7storage elements and / or multiple instances of the same type of storage element.

[0016] Power supply system 140 is configured to deliver energy7from the energy7storage system 130 to the load system 150. The power supply system 140 can generate one or more pow er supply rails (e.g.. at least one supply voltage) that provide power to the load system 150. As part of generating the power supply rails, the power supply system 140 may perform one or more power conditioning operations such as converting a voltage output of the energy^ storage system 130 intoan operating voltage of the load system 150. For example, the power supply system 140 can include a voltage regulator circuit that regulates a variable voltage output of one or more storage elements to form a substantially constant direct-current (DC) voltage signal for input to one or more load system components. The power supply system 140 can also route power to different load system components at different times in accordance with power stages selected by the PMC 160. Although shown as a separate component, the power supply system 140 can be combined with the PMC 160. For example, the PMC 160 can be an integrated circuit chip containing voltage regulating circuitry.

[0017] Load system 150 includes components that are operable to provide the functionality of the system 100. The load system components can have different power requirements, e.g., different operating voltages and / or operating currents. Such components would typically include one or more processing units (e.g., a processor or microcontroller). A processing unit may be configured to execute program instructions, which can be in the form of software or firmware. In some instances, a processing unit may be directly configured to perform an operation or processing task. For example, the load system 150 may include a field-programmable gate array (FPGA) or other logic devices that are reprogrammable. In other instances, such as with an applicationspecific integrated circuit (ASIC), a processing unit may be hardwired to perform a fixed set of tasks.

[0018] The load system 150 may further include any number of components used to deliver functionality. For instance, the load system 150 can include one or more wireless communications devices. As another example, the load system 150 can include an input / output (I / O) device such as a keyboard, an audio speaker, a light-emitting diode (LED), a liquid-cry stal display (LCD), and / or other devices that interact with a user of the system 100. These additional components mayserve as peripheral devices that are controlled by a processing unit of the load system 150 to perform various operations. Thus, the system 100 can be configured with functionality provided through multiple components working independently or in cooperation with each other.

[0019] Power management controller 160 is configured to manage power delivery and consumption for the system 100. Like the load system 150, the PMC 160 can be powered by the energy storage system 130. Alternatively, the PMC 160 may be powered directly by the PV cell 110. In some embodiments, the PMC 160 is a low-power component in the form of a power management integrated circuit (PMIC). The PMC 160 may be configured to perform operations such as voltage regulation (e g., DC-to-DC conversion), control over charging of the energystorage system 130, delivery of power from the power supply system 140 to the load system 150,and / or control over operation of the PV cell 110 (e.g., through MPPT). When implemented as a PMIC, these functions can be performed by on-chip modules within a single chip or multiple integrated circuit chips that form a single unit.

[0020] Additionally, the PMC 160 is configured to perform power sequencing to manage power-up and power-down of system components, in particular the load system 150. Power sequencing can be performed at any energy state of the energy storage system 130. For example, the PMC 160 can transition the system 100 through a sequence of power stages to recover from a low power state when the energy' storage system 130 does not have enough energy to power the load system 150. The power sequence used for recovery from the low power state can be different from a power sequence used when the energy storage system 130 has sufficient energy. Thus, the PMC 160 may be configured with different routines for bringing the system 100 into an operational state, e.g., when the system 100 is manually turned on or to resume operation after the system is shut down due to lack of power. The PMC 160 can monitor the status of the energy storage system 130 and other system components in connection with power sequencing and other operations described herein.

[0021] FIG. 2 is a more detailed block diagram of the system 100 that shows some of the interactions that can occur between system components. As shown in FIG. 2, the PMC 160 is communicatively coupled to other components through communication links 201-205. The links 201-205 can include direct wire connections. However, in some instances, the PMC 160 may be configured to communication with components through a shared bus or other communication fabric. The links 201-205 cany' signals to and from the PMC 160. Each of these links is associated with one or more operations of the PMC 160. For instance, the communication link 201 is associated with cell monitoring and, as such, carries one or more signals from which the PMC 160 is able to determine a status of the PV cell 110. As one example, the PMC 160 may use the communication link 201 to monitor the power output of the PV cell 1 10 by measuring the voltage at the output of the PV cell. Based on the voltage level, the PMC 160 may perform MPPT to control the energy harvesting system 120 such that the PV cell 110 is operated at maximum power efficiency.

[0022] The energy harvesting system 120 includes an energy harvesting circuit 210 that collects and transfers energy from the PV cell 110 to storage elements 232 and 234 in the energy storage system 130. Each storage element can receive power through a separate connection to the energy harvesting circuit 210. In this example, only two storage elements are shown. Storage element 232 is charged via a first connection 212, and storage element 234 is charged via a secondconnection 214. However, as discussed above, the energy storage system 130 can include any number of storage elements. In some embodiments, the energy harvesting circuit may include one or more boost circuits that step up the output voltage of the PV cell 110 so that the storage element 232 and / or the storage element 234 is charged to a voltage higher than the voltage at the output of the PV cell 1 10. Boost circuitry can be used, for example, when the operating voltage of a load system component is higher than the maximum output voltage of the PV cell 110. Further, in some embodiments, the boost circuitry may be part of the PMC 160.

[0023] The energy harvesting system 120 can be coupled to the PMC 160 through the communication link 202. The communication link 202 is associated with storage control and can carry one or more control signals generated by the PMC 160. For example, the PMC 160 can output a pulse-width modulation (PWM) control signal that governs the timing of when the energy harvesting circuit 210 draws power from the PV cell 110. The PMC 160 can also direct the energy7harvesting circuit 210 to transfer power to specific storage elements, e.g., using a separate control signal per storage element so that one or both of the storage elements 232, 234 are charged at any particular time.

[0024] Communication link 203 is associated with storage monitoring. The PMC 160 can monitor the status of the storage elements 232, 234 to determine when to charge each storage element. For example, like the PV cell 110, the storage elements 232, 234 can output voltages that are measured by the PMC 160. As discussed below, during low power recovery, the PMC 160 can transition between power stages based on the voltages of individual storage elements. Thus, the PMC 160 can control the energy7harvesting circuit 210 based on the statuses of the PV cell 110 and the energy7storage system 130. The voltage of a storage element is an indicator of the charge state of the storage element. Charging time is influenced by storage capacity. For example, a lower capacity storage element generally takes less time to be charged to the same output voltage compared to a higher capacity storage element. The PMC 160 can leverage this relationship between storage capacity7and charging time to provide for rapid recovery7by causing power to be drawn from storage elements of different capacity at different times. For example, the storage element 232 can be a capacitor with a capacitance less than 1 millifarad (e.g., a multilayer ceramic capacitor) or a stack of such capacitors, and the storage element 234 can be supercapacitor yvith a capacitance of at least 1 farad. Thus, the storage element 232 may correspond to a loyv capacity storage element, and the storage element 234 may correspond to a high capacity storage element having a higher storage capacity compared to the storage element 232. This would enable the storage element 232 to be used for poyver during an initial stage ofrecovery (when power consumption is not as high) before switching to the storage element 234 at a later stage.

[0025] Communication link 204 is associated with power delivery'. Each storage element is coupled to the power supply system 140. In some instances, the storage elements are coupled to the same power delivery elements. For example, the storage element 232 may be configured to output a voltage signal 236 to a voltage regulator 242 and a voltage regulator 244. Likewise, the storage element 234 may be configured to output a voltage signal 238 to the voltage regulator 242 and the voltage regulator 244. The PMC 160 can generate one or more control signals that cause power to be delivered from a particular storage element to one or more components of the load system 150. Examples of power delivery in conjunction with low power recovery are described below.

[0026] Each voltage regulator can generate one or more power supply signals for use by the load system 150. For instance, the voltage regulator 242 may output a power supply signal 246 that operates as a supply rail for one or more load system components. Similarly, the voltage regulator 244 may output a separate power supply signal 248 that operates as a supply rail for another set of one or more load system components. The power supply signals can differ with respect to their voltage, current, waveform, and / or other electrical characteristics. For instance, the power supply signal 246 and the power supply signal 248 could be DC signals with different voltage levels. If each storage element is coupled to both voltage regulators, then the power supply signals can be generated from the output of either storage element. For example, the PMC 160 could direct the voltage regulator 242 to generate the power supply signal 246 using the storage element 232 at certain times and using the storage element 234 at other times. Similarly, the PMC 160 could direct the voltage regulator 244 to generate the power supply signal 248 using the storage element 232 or the storage element 234. However, the storage elements need not be shared between every component of the power supply system 140. In some instances, a storage element may be provided with its own voltage regulator or other power delivery' element.

[0027] Communication link 205 is associated with status signaling. As shown in FIG. 2, the load system 150 can include a processor 154 and one or more auxiliary components 152. The PMC 160 can use the communication link 205 to transmit one or more status signals to the processor 154. The status signal(s) can be transmitted over separate electrical connections or over a shared connection. For example, different messages can be digitally encoded for transmission over one or more shared wires, and the processor 154 may decode the messages to extract the status information contained therein. In some implementations, a status signal may simply be asignal that is asserted for a certain duration and then de-asserted (e.g., a signal associated with a particular output port / pin of the PMC 160).

[0028] The status signal(s) can indicate which power stage has currently been selected by the PMC 160 and may also carry control information for selectively enabling certain functions. In some embodiments, the PMC 160 may indicate the currently selected power stage by signaling a status of the energy storage system 130. For example, the PMC can send a status signal informing the processor 154 that the storage element 232 has been charged to a threshold voltage associated with a first power stage and send another status signal when the storage element 234 has been charged to a threshold voltage associated with a second power stage. Through receiving such signals, the processor 154 can recognize when the storage elements 232, 234 have accumulated enough energy to power the processor 154 and / or the auxiliary component(s) 152. Thus, the processor 154 may be configured to determine, based on the status signal(s), which operations the processor 154 is permitted to perform and / or which auxiliary components 152 the processor is permitted use at any given time. In this way, the PMC 160 can direct the power sequencing to ensure that the appropriate functions are enabled at each power stage and to temporarily disable non-permitted functions, even if the components that provide such non-permitted functions are receiving power.

[0029] During normal operation of the system 100, e.g., when the energy storage system 130 has enough energy to power the entire load system 150. the PMC 160 may control the energy harvesting circuit 210 to keep the storage element 232 and / or the storage element 234 at a certain level of electric charge. For example, the PMC 160 can be configured to keep one or both storage elements between a minimum charge level and a maximum charge level. At times, the energy level of the storage elements may be insufficient, e.g., due to operating in a low or no light environment. When the energy level is insufficient to enable any of the power supply signals to be generated, the PMC 160 may initiate a shutdown of the entire system 100. Subsequently, when the PV cell 110 is exposed to light, the PMC 160 may power itself up, e.g., directly from the PV cell, to begin low power recovery by charging at least some of the storage elements 232, 234. Because the energy level of the storage elements is still low at this time, the PMC 160 may prioritize power delivery to consumers that are more critical to the operation of the system 100, e.g., the processor 154. Consequently, the functionality that the load system 150 is capable of providing can be made available in an incremental manner through successive pow er stages until the system 100 is fully operational.

[0030] FIG. 3 shows an example of a specific implementation of the system 100. In this example, the system 100 is implemented as a remote control 300, e.g., for a television set and / or a cable box connected to a television set. However, the system 100 can be implemented in other low power devices, e.g., a computer keyboard or mouse, a temperature sensor, a smoke detector, an electronic-ink based photo album, an alarm clock, etc. FIG. 3 is provided to illustrate examples of components that can form the load system 150. As such, system components that are not part of the load system are omitted in this figure. In FIG. 3, the processor 154 is configured with a set of power profiles 302 and boot configuration settings 304. The power profiles 302 can include profiles associated with various power stages selected by the PMC 160 during low power recovery. As such, the processor 154 may use the power profiles 302 to determine what functions to enable, e.g., which auxiliary components the processor is permitted to access or operate. The power profiles 302 may be programmed or hardwired into the processor 154, e.g., programmed into on- chip memory or a local memory register, or through setting fuses or antifuses.

[0031] The boot configuration settings can be programmed in a similar manner to the power profiles and are used to define a boot procedure that the processor performs when powered up. The boot procedure may include operations such as discovering or checking the connectivity of auxiliary components, running self-diagnostics, initializing into a default execution state, and / or the like. Completing the boot procedure may place the remote control 300 into an operation-ready state in which the remote control 300 can respond to user inputs. However, depending on the energy level of the energy storage system 130, the remote control 300 may only be able to provide a limited set of functions.

[0032] The processor 154 can include a low power transceiver 306. For instance, the processor 154 can be a system-on-chip (SOC) or microcontroller with an embedded Bluetooth Low Energy (BLE) transceiver, which can be powered using the processor’s own power supply (e.g., the output of the voltage regulator 244 in FIG. 2). BLE is a wireless communication technology that operates over the same radio frequencies as classic Bluetooth (the 2.4 gigahertz ISM radio band), with significantly less power consumption at the expense of communications range and data rate. Whereas the energy consumption for transmission over classic Bluetooth is typically around 1 watt, transmission over BLE can consume as little as 10 milliwatts (mW), a hundred times less. Thus, BLE is suitable for remote controls and other wireless devices that don’t require long range communication (e.g., within 100 meters).

[0033] The remote control 300 may include other wireless communication devices (transmitters and / or receivers) besides the low power transceiver 306. For example, the remotecontrol 300 can include a Wi-Fi transceiver 310 and / or an infrared LED 320. An infrared LED may have a forward voltage of 1.2V and a forward current of around 20 milliamps (mA), which are a typical operating voltage and current for an LED. However, some LEDs have higher power requirements. For instance, a white LED may operate at 3.2V and 40mA. Therefore, the instantaneous power consumption of the infrared LED 320 can be much higher than that of the low power transceiver. The power consumption of the Wi-Fi transceiver 310 could be even higher. The infrared LED 320 may only consume power intermittently (e.g., when activated in response to a button press). In contrast, Wi-Fi communication consumes power as long as a Wi-Fi connection has been established, even when not actively transmitting or receiving data. Further, Wi-Fi tends to consume more power than even classic Bluetooth (typically about ten times greater). Although Wi-Fi consumes more power and may not be needed for transmitting basic commands from the remote control 300 to a receiver device, there may be times when the remote control 300 uses the Wi-Fi transceiver 310 to communicate, e.g., to a device lacking Bluetooth capabilities.

[0034] The remote control 300 may further include a memory system 330, a keypad 340, a backlight 350, and / or a microphone 360. The memory system 330 can include one or more memory devices that provide volatile and / or non-voltage storage for data used by the processor 154. For instance, the memory’ system 330 can store program instructions 332 or custom settings 334. Program instructions 332 may include software and / or firmware code to be executed by the processor 154. However, in some instances, the processor 154 may be preprogrammed to provide certain functionality’ without having to obtain instructions from memory’. In such instances, the memory system 330 may store values of program parameters or settings that are accessed by the processor 154 during operation of the remote control. Program instructions, parameters, or settings can relate to the operation of one or more components in communication with the processor 154. For example, the memory’ system 330 can store a driver program or device settings for the Wi-Fi transceiver 310, the infrared LED 320, the keypad 340, the backlight 350, and / or the microphone 360. each of which may be a peripheral component operated under control of the processor 154. Custom settings 334 can include any number of user-configured settings such as functionality assigned by a user to specific keypad elements (e.g., a button for a particular television command), backlight settings (e.g., backlight duration, always on / off), or settings for specific user devices (e.g., a television, a DVD player, a loudspeaker system).

[0035] Keypad 340 can be an electronic keypad with push buttons or other actuation mechanisms that are used to capture user input for processing. For example, the keypad 340 may include push buttons to adjust audio volume, change television channels, turn a television on oroff, etc. Other mechanical input devices may also be present, such as a scroll wheel, a rotating dial, a slide switch, and / or the like. Further, the remote control 300 may be configured to capture touch input, e.g., using a separate touchpad.

[0036] Backlight 350 includes one or more light-emitting elements that provide background lighting, e.g.. a backlight for the keypad 340. In some implementations, the light-emitting element is an LED, e.g., a separate LED for each button / key on the keypad 340. The LEDs of the backlight 350 can be of the same or different color and may be programmable to change the color and / or intensity7of the emitted light. As such, the backlight 350 can consume significantly more power than the processor 154, the infrared LED 320, and other components of the remote control.

[0037] Microphone 360 may include an audio transducer and signal processing circuitry to receive and process an audio signal generated by the audio transducer. The microphone 360 can be used to generate a voice recording for wireless transmission (e.g., using the low power transceiver 306) to a television or other Internet-connected device. The voice recording may ultimately be forwarded to a cloud server that processes the voice recording to recognize a voice command and return a response.

[0038] Based on the above description of the various components that can form the remote control 300, it will be understood that some components can be prioritized for receiving power over other components if a situation warrants that power should not be simultaneously made available to every7component. For example, during recovery from a low power state, power from the energy storage system 130 can be delivered to higher priority components first, so that functionality associated with the higher priority components becomes available before functionality7associated with lower priority components. In addition to prioritizing power delivery' at the component level, prioritization can be applied to the functionality of individual components. For example, during low power recovery, the processor 154 could be supplied power to enable the processor to perform a limited set of operations (e.g., using the low power transceiver 306 and / or internal circuits), but other operations supported by the processor 154 may remain unavailable for some time (e.g., operations that are more computation intensive or use higher-power components). Accordingly, the functionality that the remote control (or system 100) is capable of providing can be made available in stages through power sequencing, where power sequencing can involve controlling delivery of power to specific components and / or controlling how components make use of the delivered power. As discussed below in connection w ith FIG. 4, pow er stages can be associated with power profiles that are selected based on the state of the energy storage system 130.

[0039] FIG. 4 is a flow diagram showing an example process 400 for performing power sequencing, according to certain embodiments. The functionality shown in FIG. 4 can be performed using a power management controller (e.g., PMC 160) of an electronic system including an energy storage system and a PV cell. At 402, the PMC performs a cold start to initialize itself, e.g.. by powering up internal circuitry of the PMC and / or performing selfdiagnostics to confirm that the internal circuitry is functional. The cold start may correspond to the beginning of a recovery from a low power or no power state. For instance, the PMC 160 may be configured to perform the cold start once the PV cell 110 starts producing enough voltage to turn on the PMC. e.g., when the PV cell 110 is exposed to light after the system 100 was previously shutdown due to depletion of the energy storage system 130. The PMC 160 may be aware of the earlier shutdown because the shutdown was recorded, e.g., through setting a flag in a memory register shortly before shutdown. At the time of the cold start, the energy storage system 130 may be electrically disconnected from the load system 150 such that the only component drawing power is the PMC 160. For instance, the PMC 160 can obtain the power needed to perform the cold start from the energy storage system 130 or directly from the PV cell 110.

[0040] At 404, the PMC transitions the electronic system to a first power stage (Stage 1) in which the electronic system is non-operational. Here, non-operational means that the functionality the electronic system is capable of providing is unavailable due to lack of power to and / or disabling of the components configured with such functionality (e.g., load system 150). During Stage 1, the load system can remain unpowered while the energy storage system begins charging. The PMC can select which energy7storage elements are being charged at any given time. In Stage 1, the PMC may cause power to be routed to a low capacity storage element, e.g., by controlling the energy harvesting circuit 210 to direct the power generated by the PV cell 110 to the storage element 232 but not the storage element 234.

[0041] At 406, the PMC transitions the electronic system to a second pow er stage (Stage 2) in response to detecting that the low capacity storage element has reached a first voltage. The first voltage can be a predefined threshold voltage sufficient for providing power to a limited set of components. For instance, the first voltage can be a minimum voltage required for the voltage regulator 242 to start producing a regulated supply voltage for an application processor (e.g., the processor 154). At this time, the PMC can cause powder to be delivered from the energy storage system to the application processor but not to other components such as the auxiliary component(s) 152. Thus, Stage 2 may correspond to a minimum functionality profile that the application processor has been configured with. To ensure a steady supply of power to the applicationprocessor, the PMC can activate a regulated voltage supply, e.g., through a voltage regulator of the power supply system 140.

[0042] Once the application processor receives power, it may receive a status signal indicating that the low capacity storage element has reached the first voltage. In response to this status signal, the application processor can initiate a boot sequence to boot into the minimum functionality profile. Like the initialization of the PMC during the cold start in 402, the boot sequence may involve initialization of the application processor. Additionally, the boot sequence may involve checking the status of system components used by the application processor. For example, the application processor may perform a discovery procedure to enumerate hardware resources as such the auxiliary component(s) 152. The boot sequence can be configured through hardware and / or software settings. In some instances, the boot sequence may involve execution of program instructions. Such instructions would typically correspond to the start of a main program executed by the application processor, since low power devices generally do not require a separate operating system program.

[0043] At 408. the PMC transitions the electronic system to a third power stage (Stage 3) in response to detecting that the low capacity storage element has reached a second voltage. The second voltage can be any voltage higher than the threshold voltage for transitioning to Stage 2 (the first voltage). For instance, the second voltage can be a predefined threshold voltage sufficient for providing power to some, but not all, of the auxiliary components 152. Additionally or alternatively, the second voltage can be a voltage sufficient for activating additional capabilities of the application processor. For example, the first voltage may enable the application processor to perform certain tasks (e.g., a voltage permitting the application processor to at least boot up safely), but other tasks may not be available until the application processor is supplied with the second voltage, either directly or in the form of a regulated supply voltage. Thus, Stage 3 may correspond to a medium functionality' profile in which the electronic system is able to provide more functions compared to the minimum functionality profile of Stage 2. The application processor may enter the medium functionality profile in response to a status signal indicating that the low capacity storage element has reached the second voltage.

[0044] In Stage 3, the PMC may cause power to be routed to a high capacity storage element, e.g., by controlling the energy harvesting circuit 210 to direct the power generated by the PV cell 110 to the storage element 234 instead of, or in addition to, the storage element 232. The high capacity storage element can be any rechargeable storage element with sufficient storage capacity to meet power demand when the electronic system is fully operational. While the high capacitystorage element is charging, the low capacity storage element can continue to supply power for the application processor. Additionally, the low capacity storage element may optionally be used to supply pow er to some auxiliary components, e.g., through a separate voltage regulator than the one used to supply the application processor.

[0045] At 410, the PMC transitions the electronic system to a fourth power stage (Stage 4) in response to detecting that the high capacity storage element (e.g., storage element 234) has reached a third voltage. Stage 4 may correspond to a full functionality profile in which the electronic system is fully operational. The application processor may enter the full functionality profile in response to a status signal indicating that the high capacity storage element has reached the third voltage. When the electronic system is fully operational, the energy storage system has enough power to sustain any of the functions it is capable of providing. However, this does not necessarily mean that every' component in the electronic system is active simultaneously. Instead, the electronic system can utilize its load system components as needed to perform any function the load system has been configured for. For example, when the system 100 is fully operational, the processor 154 may activate the auxiliary component(s) 152 in response to user input, but the auxiliary components or the processor itself may enter a power conserving state (e.g., sleep or standby) until called upon. Accordingly, the PMC may have enabled the power supplies for the entire load system, but not every load system component may be actively consuming power (e.g., drawing more than quiescent current).

[0046] In Stage 4, the high capacity storage element is usable to deliver power to the entire load system. Thus, the transition from Stage 3 to Stage 4 may involve switching from the low capacity storage element to the high capacity storage element. For example, the PMC can disable a voltage regulator associated with the low capacity storage element to instead enable a voltage regulator associated with the high capacity storage element so that the regulated voltage supply for the application processor is derived solely from the output of the high capacity storage element. The third voltage can be a predefined threshold voltage sufficient for providing power to the entire load system. However, the third voltage is not necessarily higher than the second voltage. For example, the second voltage and the third voltage could be the same voltage, representing both the maximum required output voltage of the low capacity storage element and the minimum required output voltage of the high capacity storage element. Because the high capacity storage element has a higher storage capacity, it generally takes longer for the high capacity storage element to reach any particular voltage compared to the low capacity storage element, especially when both storage elements are fully depleted at the start of charging. For example, the low capacity storage element may reach the second voltage within seconds or minutes, but the high capacity storageelement may not reach the third voltage (or a voltage corresponding to full charge) until several hours later.

[0047] The high capacity storage element may be sized based on an expected maximum power consumption of the load system (e.g., peak instantaneous wattage and current) to ensure that all the power supply signals required by the load system can be generated from the output of the high capacity storage element even when the load system is consuming maximum power. The high capacity storage element may also be designed to have sufficient capacity to sustain the third voltage for a certain duration (e.g., a minimum required run time) assuming the electronic system is operated continuously without further exposure to light. Accordingly, the low capacity storage element may enable the electronic system to reach a partially functioning state quickly, and the high capacity storage element may enable not only full functionality, but also prolonged operation.

[0048] FIG. 4 is merely an example of the different power stages that can occur in a power-up sequence. In other embodiments, the number of power stages and / or the operations performed in a particular stage may differ from that shown in FIG. 4. For instance, some embodiments may combine aspects of Stage 2 and Stage 3 into one stage so that the system is configured without a medium functionality' profile. Alternatively, Stage 3 may be further divided into sub-stages. Thus, the threshold voltages for various storage elements and / or other conditions evaluated by the PMC to trigger transitions between power stages may also differ. Other power-up sequences involving energy storage elements of different capacity are possible.

[0049] FIG. 5 is a flow diagram showing an example process 500 for recovering from a low power state, according to certain embodiments. The process 500 can be performed in conjunction with the power sequencing in FIG. 4, using the same PMC (e.g., PMC 160). At 502, an energy' storage system is monitored to begin recovering from the low power state. The monitoring in 502 can begin during the cold start in 402 of FIG. 4, or shortly after completion of the cold start, so that the PMC is aware of the initial state of the energy storage system at the time of transitioning to Stage 1. The monitoring in 502 can include measuring the output voltage and / or current of each storage element in the energy storage system. However, a PMC can be configured to monitor other components with respect to power generation, consumption, and / or delivery. For example, the PMC 160 can also measure the output voltage and / or cunent of the PV cell 110 to determine the status of the PV cell 110 together with the energy storage system 130, as part of the monitoring in 502. Further, based on the discussion of FIG. 4 above, it will be apparent the PMC can continue to monitor (e.g., at periodic intervals) components over the course of different power stages.

[0050] At 504, the electronic system transitions through a sequence of power stages (e.g.. Stages 1 to 4 in FIG. 4) in connection with the recovery. The PMC can determine when to transition from one power stage to the next based on continued monitoring of the energy storage system. The functionality available through the load system can be successively enabled across different power stages so that full functionality is achieved once the electronic system has transitioned to the last stage (e.g., Stage 4), thereby completing the recovery.

[0051] To illustrate an example application of the techniques described above, the following is a description of the processes 400 and 500 as applied to the remote control 300 in FIG. 3. The remote control 300 may enter a low power state due to absence of power from an external power source. For instance, the energy storage system 130 could become depleted during operation of the remote control in dark lighting conditions, e.g., viewing television at night with the lights off. The energy' storage system 130 could also become depleted through disuse, e.g., gradual discharge of the storage elements after the remote control is lost or misplaced in a location where the remote control cannot receive light.

[0052] Upon exposure to light, the PV cell 110 of the remote control begins to convert light energy to electrical energy, causing the PMC 160 to turn on and perform a cold start (402). This could occur within seconds of exposure to light, e.g., once the PV cell 110 reaches around 600 millivolts or some other threshold voltage required for a cold start. The PMC 160 begins monitoring (502) the energy storage system of the remote control and causes the remote control to transition to Stage 1 (404). At this time, the low capacity’ storage element 232 starts to charge, but the load system remains unpowered. The load system of the remote control may include the processor 154, the Wi-Fi transceiver 310, the infrared LED 320, the memory' system 330, the keypad 340, the backlight 450. and the microphone 360.

[0053] When the storage element 232 reaches the first voltage, the PMC 160 causes the remote control to transition to Stage 2 (406), at which time the power supply for the processor 154 is enabled so that the processor 154 executes a boot sequence. For example, the processor 154 may be configured to apply the boot configuration settings 304 in response to a status signal indicating that the PMC 160 has selected Stage 2. Upon completing the boot sequence, the processor 154 may perform one or more operations in support of the low power recovery . For example, the processor 154 may use the low power transceiver 306 to send a beacon or distress signal to a television set to cause the television to display a message that indicates the remote control needs to be charged and prompts the user to place the remote control near a light source. Typically , the remote control would be able to continue transitioning through the remaining power stages underthe same lighting conditions that caused the PMC to turn on (e.g., indoor lighting with an illuminance of 100 lux or higher). However, the user could move the remote control to a location with stronger light (e.g., next to a desk lamp or an area with sunlight) to expedite charging.

[0054] When the storage element 232 reaches the second voltage, the PMC 160 causes the remote control to transition to Stage 3 (408), at which time the high capacity storage element (234) begins charging while the storage element 232 continues to be used to power the processor 154. Additionally, the PMC 160 may signal over the communication link 205 that other components powered by the processor 154 are now allowed to be used. For example, the keypad 340 may receive power from the processor 154 to register button presses, and the processor 154 mayexecute program instructions 332 in the memory system 330 to respond to certain buttons.

[0055] When the storage element 234 reaches the third voltage, the PMC 160 causes the remote control to transition to Stage 4 (410), so that the storage element 234 is used to power the entire load system. For example, in Stage 4, the processor 154 may respond to any inputs received through the keypad 340 or the microphone 360 (e.g., a voice command). Further, the backlight 350 can be turned on to illuminate the keypad 340. and the Wi-Fi transceiver 310 and / or the infrared LED 320 can be used to communicate with the television set or other wirelessly controlled devices.

[0056] The embodiments disclosed herein are illustrative examples and may be embodied in various forms, with variations being made according to specific operational or performance requirements. For instance, aspects of different embodiments may be combined, and various embodiments may omit, substitute, or add various procedures or components as appropriate. In alternative configurations, the methods described may be performed in an order different from that described, and / or various stages may be added, omitted, and / or combined. Specific structural and functional details disclosed herein are provided for illustration purposes and, unless expressly recited in the claims, are not to be interpreted as limiting.

[0057] Terms, “and” and “or” as used herein, may include a variety- of meanings that are also expected to depend at least in part upon the context in which such terms are used. Typically, “or” if used to associate a list, such as A, B, or C, is intended to mean A, B, and C, here used in the inclusive sense, as well as A. B, or C, here used in the exclusive sense. In addition, the term “one or more” as used herein may be used to describe any feature, structure, or characteristic in the singular or may be used to describe some combination of features, structures, or characteristics. However, it should be noted that this is merely an illustrative example and claimed subject matter is not limited to this example. Furthermore, the term “at least one of’ if used to associate a list,such as A, B, or C, can be interpreted to mean any combination of A, B, and / or C, such as A, AB, AC, BC, AA, ABC, AAB, AABBCCC, etc.

[0058] The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense. It will, however, be evident that additions, subtractions, deletions, and other modifications and changes may be made thereunto. Thus, although specific embodiments have been described, these are not intended to be limiting. Various modifications and equivalents are within the scope of the following claims.

Claims

CLAIMSWHAT IS CLAIMED IS:

1. An electronic device comprising: a photovoltaic (PV) cell; an energy storage system including a first storage element and a second storage element, wherein the second storage element has a higher storage capacity than the first storage element; an energy' harvesting system configured to charge the first storage element and the second storage element using the PV cell; a load system powered by the energy storage system, the load system including a processor and one or more auxiliary components; and a power management controller configured to: monitor the energy storage system; and transition the electronic device through a sequence of power stages in connection with recovery from a low power state in which the energy storage system has insufficient energy to power the load system, wherein the sequence of power stages comprises, in order of occurrence: a first power stage in which the PV cell is used to charge the first storage element without charging the second storage element, and the load system is unpowered; a second power stage in which the first storage element powers the processor but not the one or more auxiliary components, and the PV cell is used to charge the second storage element; and a third power stage in which the second storage element powers the processor and the one or more auxiliary components.

2. The electronic device of claim 1. wherein the one or more auxiliary components have a higher operating voltage, a higher operating cunent. or both, relative to the processor.

3. The electronic device of claim 1, wherein to monitor the energy storage system, the power management controller is configured to: determine that the first storage element has accumulated enough energy to power the processor based on detecting that the first storage element has reached a first threshold voltage during the first power stage; anddetermine that the second storage element has accumulated enough energy to power the processor and the one or more auxiliary components based on detecting that the second storage element has reached a second threshold voltage during the second power stage, wherein the second threshold voltage is equal to or higher than the first threshold voltage.

4. The electronic device of claim 1, wherein: the power management controller is further configured to trigger the second power stage through outputting a signal indicating that the first storage element has accumulated enough energy to power the processor; and the processor is configured to execute a boot procedure in response to the signal output by the power management controller.

5. The electronic device of claim 1. wherein: the power management controller is further configured to trigger the third power stage through outputting a signal indicating that the second storage element has accumulated enough energy to power the processor and the one or more auxiliary components; and the processor is configured to access the one or more auxiliary components based on the signal output by the power management controller.

6. The electronic device of claim 1, wherein: during the second power stage, the processor is operable to provide a subset of functions the electronic device is capable of, using circuitry associated with the processor; and during the third power stage, the processor and the one or more auxiliary components are collectively operable to provide full functionality7of the electronic device.

7. The electronic device of claim 6, wherein the circuitry associated with the processor comprises a wireless transceiver powered by the processor.

8. The electronic device of claim 1. wherein the one or more auxiliary components comprise a light-emitting element, a wireless transmitter, a wireless receiver, or any combination thereof.

9. The electronic device of claim 1. wherein the first storage element is a capacitor with a capacitance less than 1 millifarad.

10. The electronic device of claim 9, wherein the second storage element is a rechargeable battery, or a supercapacitor with a capacitance of at least 1 farad.

11. The electronic device of claim 1, wherein the electronic device further comprises voltage regulating circuitry configured to, under control of the power management controller, convert one or more voltages produced by the energy storage system into: a first supply voltage used by the processor during the second power stage; and a second supply voltage used by the processor and the one or more auxiliary components during the third power stage, the second supply voltage being equal to or higher than the first supply voltage.

12. A method of recovery from a low power state, the method comprising: monitoring, by a power management controller of an electronic device, an energy' storage system in the electronic device, wherein: the energy storage system includes a first storage element and a second storage element having a higher storage capacity than the first storage element, the first storage element and the second storage element are chargeable using a photovoltaic (PV) cell of the electronic device, and the low power state is a state in which the energy' storage system has insufficient energy to power a load system of the electronic device, the load system including a processor and one or more auxiliary components; and transitioning, by the power management controller, the electronic device through a sequence of power stages in connection with recovery' from the low power state, wherein the sequence of power stages comprises, in order of occurrence: a first power stage in which the PV cell is used to charge the first storage element without charging the second storage element, and the load system is unpowered; a second power stage in which the first storage element powers the processor but not the one or more auxiliary components, and the PV cell is used to charge the second storage element; and a third power stage in which the second storage element powers the processor and the one or more auxiliary components.

13. The method of claim 12, wherein the one or more auxiliary components have a higher operating voltage, a higher operating current, or both, relative to the processor.

14. The method of claim 12, wherein monitoring the energy storage system comprises: determining, by the power management controller, that the first storage element has accumulated enough energy to power the processor based on detecting that the first storage element has reached a first threshold voltage during the first power stage; anddetermining, by the power management controller, that the second storage element has accumulated enough energy to power the processor and the one or more auxiliary components based on detecting that the second storage element has reached a second threshold voltage during the second power stage, wherein the second threshold voltage is equal to or higher than the first threshold voltage.

15. The method of claim 12, wherein transitioning the electronic device through the sequence of power stages comprises: triggering the second power stage through outputting, by the power management controller, a signal indicating that the first storage element has accumulated enough energy to power the processor; and executing, by the processor, a boot procedure in response to the signal output by the power management controller.

16. The method of claim 12, wherein transitioning the electronic device through the sequence of power stages comprises: triggering the third power stage through outputting, by the power management controller, a signal indicating that the second storage element has accumulated enough energy to power the processor and the one or more auxiliary components; and accessing, by the processor, the one or more auxiliary components based on the signal output by the power management controller.

17. The method of claim 12, wherein: during the second power stage, the processor is operable to provide a subset of functions the electronic device is capable of, using circuitry associated with the processor; and during the third power stage, the processor and the one or more auxiliary components are collectively operable to provide full functionality of the electronic device.

18. The method of claim 12, wherein the first storage element is a capacitor with a capacitance less than 1 millifarad.

19. The method of claim 18, wherein the second storage element is a rechargeable battery', or a supercapacitor with a capacitance of at least 1 farad.

20. The method of claim 12, further comprising converting, under control of the power management controller, one or more voltages produced by the energy storage system into: a first supply voltage used by the processor during the second power stage; anda second supply voltage used by the processor and the one or more auxiliary components during the third power stage, the second supply voltage being equal to or higher than the first supply voltage.

Images