Ultra-low power energy harvesting electronic devices

Abstract

The electronic device (20; 60; 100; 150; 170; 180; 182; 190; 192; 200; 210) comprises a photovoltaic power unit (21), an energy storage unit (22), a voltage detector (23), a load switch (24), and an application load (25). The electronic device (20; 60; 100; 150; 170; 180; 182; 190; 192; 200; 210) is configured to collect and store energy from ambient lighting and optimize power delivery to the application load (25) from at least one of the collected and stored energy. The photovoltaic power unit (21), the energy storage unit (22), the voltage detector (23), and an input of the load switch (24) are connected to a common point (N1). The photovoltaic power unit (21) collects energy from ambient lighting. An output of the load switch (24) is coupled to the application load. The voltage detector (23) measures the voltage at the common point (N1) to provide an optimized power supply from at least one of the energy storage unit (22) and the photovoltaic unit (21) to the application load, and turns on the load switch (24) when the measured voltage rises to a level equal to or greater than a first voltage. The voltage detector (23) turns off the load switch (24) when the measured voltage falls to a level equal to or less than a second voltage, so that the photovoltaic unit (21) stores energy in the energy storage unit (22). The first voltage is greater than the second voltage.

Description

[Technical field]

[0001] The present disclosure relates to ultra-low power energy harvesting circuit designs. [Background technology]

[0002] Real-time location systems (RTLS), also known as real-time tracking systems, are used to automatically identify and track the location of objects and people in real time. Unlike global positioning satellite (GPS) systems, RTLS typically operate within buildings or other controlled areas. Wireless RTLS tags are attached to physical objects or worn by people. In most RTLS, fixed reference points receive radio "beacon" signals from the tag to determine its location. RTLS reference points may also transmit information to the tag. Multiple reference points are placed throughout a building (or similar area of ​​interest) to provide the desired tag detection range. The accuracy of the tag location depends on many variables. Examples of real-time location systems include tracking cars through an assembly line, locating pallets of goods in a warehouse, and locating medical equipment in a hospital.

[0003] RTLS designs published to date use a combination of at least one photovoltaic element (solar cell) and a battery to power the tag operation. When the battery becomes discharged, the tag (and, inevitably, the asset to which the tag is attached) goes missing temporarily until the battery is sufficiently charged to allow the tag to transmit a beacon signal. The battery can become discharged if the circuitry is not optimized or if the ambient light level is too low. A larger battery or a larger photovoltaic element would allow the tag to transmit a beacon signal constantly, but such a design would increase cost, require more maintenance (even rechargeable batteries eventually need to be replaced), and be larger in size. Therefore, an ideal tag design would be small, low-cost, and able to harvest energy from the surroundings to provide a periodic beacon signal regardless of the energy harvesting conditions.

[0004] Wireless RTLS tags have been disclosed that use sensors to transmit information detected by the sensors to a defined reference point. Such sensor tags transmit both the location of the tag and at least one physically detected attribute (e.g., temperature, humidity, acceleration, etc.). If the tag is attached to an immovable object, the tag may not need to transmit location information.

[0005] Patent application US20180295466A1 discloses an apparatus, system, and article of manufacture for providing a wireless beacon and beacon housing for low power and short range radio frequency. The tag disclosed in US20180295466A1 uses a battery, but does not disclose how to harvest energy from the environment to power the tag, nor does it disclose a circuit design optimized for ultra-low power operation. Patent application US20100013639A1 discloses a system for providing asset tracking of mobile assets, but does not disclose a circuit design optimized for ultra-low power operation. Patent applications US2019 / 0354824A1, US20180110012A1, US20210073153A1, US20190028089A1, US20110264293A1, US20130020880A1, US8264194B1, US8686681B2, US10211647B2, EP1751727B1, EP3787148A1, US20190265664A1, WO2011083424A1, EP3264785B1, and WO2016187019A1 disclose various tagging devices that can be used for detection purposes and localization of tags. Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention aims to realize various electronic devices that harvest energy from ambient lighting and store the harvested energy. These electronic devices are configured to optimize the power supply to the associated application load in order to optimize the amount of useful work the electronic device performs with the harvested energy. Optimizing the amount of useful work performed with the harvested energy reduces the overall power consumption of the electronic device. Each electronic device of the present invention can be a tag device or can be included in a tag device. The electronic device can transmit information to a network of multiple wireless receivers via a wireless transmitter. The electronic device can transmit information that allows it to locate itself or information related to data acquired by one or more sensors associated with it. Some aspects of the present invention disclose each electronic device that measures the ambient lighting level and automatically optimizes the power supply to the associated application load accordingly. If the electronic device includes a wireless transmitter, the optimized power supply can optimize the speed of data transmission by the wireless transmitter (i.e., optimize the circuit efficiency of the electronic device). Optimizing the power supply to the application load optimizes the circuit efficiency, which in turn allows the application load to optimize the amount of useful work performed on the energy harvested by the electronic device.

[0007] Each aspect of the present invention aims to optimize the power supply to the application load in the electronic device to reduce overall power consumption compared to the prior art, thereby miniaturizing and reducing the cost of the electronic device while maintaining acceptable circuit efficiency. In other words, the electronic device of the present invention aims to perform more useful work and have higher circuit efficiency than the prior art for the same amount of energy, thereby providing the advantages of low cost and miniaturization. Each electronic device of the present invention has an optimized power supply and a higher circuit efficiency for a wider range of ambient lighting conditions than the prior art. In other words, each electronic device of the present invention can operate in lower ambient lighting conditions than the prior art. Each electronic device of the present invention can perform acceptable operation in most ambient lighting conditions due to the optimized power supply. Each aspect of the present invention utilizes a smaller photovoltaic unit than the prior art, thereby miniaturizing and reducing the cost while maintaining acceptable circuit efficiency. Unlike the prior art, some electronic devices of the present invention do not use batteries or rechargeable batteries (i.e., they only use capacitors or supercapacitors to store energy), which further reduces size and cost while maintaining acceptable circuit efficiency. [Means for solving the problem]

[0008] One aspect of the present invention provides an electronic device comprising a photovoltaic power generation unit, an energy storage unit, a voltage detector, a load switch and an application load, the electronic device being configured to collect and store energy from ambient lighting and optimize power supply to the application load from at least one of the collected and stored energy, the photovoltaic power generation unit, the energy storage unit, the voltage detector and an input of the load switch being connected at a common point, the photovoltaic power generation unit being configured to collect energy from the ambient lighting, the output of the load switch being coupled to the application load, the voltage detector being configured to measure a voltage at the common point, the voltage detector being further configured to turn on the load switch when a voltage measured at the common point rises to a level equal to or greater than a first voltage to provide optimized power to the application load from at least one of the energy storage unit and the photovoltaic power generation unit, the voltage detector being further configured to turn off the load switch when a voltage measured at the common point falls to a level equal to or less than a second voltage, the photovoltaic power generation unit storing energy in the energy storage unit, the first voltage being greater than the second voltage.

[0009] The electronic device of the present invention may be configured such that, when the load switch is turned on, the application load executes a start-up sequence and then executes at least one activity sequence.

[0010] The electronic device of the present invention may be configured to complete an initiated sequence of activities.

[0011] The electronic device of the present invention may be configured such that the first voltage is within 20% of the voltage that the photovoltaic unit produces at its maximum power point for a given temperature.

[0012] The electronic device of the present invention may be configured so that the energy storage unit includes at least one of a battery and a rechargeable battery.

[0013] The electronic device of the present invention may be configured such that the energy storage unit includes at least one of a capacitor and a supercapacitor.

[0014] The electronic device of the present invention may include a voltage regulator connected between the load switch and the application load.

[0015] The electronic device of the present invention may include at least one sensor that participates in the application load and is configured to collect data related to at least one of orientation, acceleration, temperature, humidity, air pressure, light, illuminance, magnetic field, sound, infrared, ultraviolet, gas, proximity, images, and user input, or any combination thereof.

[0016] The electronic device of the present invention may be configured such that the data collected by the sensors is stored in a memory associated with the application load.

[0017] The electronic device of the present invention may include at least one actuator configured to participate in the application load and to collect data related to at least one of a push button, a switch, a touch sensor, and a user input, or any combination thereof.

[0018] The electronic device of the present invention may be configured such that the data collected by the actuators is stored in a memory associated with the application load.

[0019] The electronic device of the present invention may be configured such that a sensor and / or actuator initiates a sequence of actions.

[0020] The electronic device of the present invention may include an illuminance sensor associated with the application load, wherein the application load and the illuminance sensor associated therewith are configured to measure an ambient illuminance level, and the application load and the illuminance sensor associated therewith are further configured to automatically optimize circuit efficiency in response to the measured ambient illuminance level.

[0021] The electronic device of the present invention may be further configured such that the photovoltaic power generation unit is directly connected to the application load, the photovoltaic power generation unit and the application load are configured to measure an ambient illumination level, and the photovoltaic power generation unit and the application load are configured to automatically optimize circuit efficiency in response to the measured ambient illumination level.

[0022] The electronic device of the present invention may be configured so that the application load includes a wireless communication unit.

[0023] The electronic device of the present invention may be configured so that the wireless communication unit is a Bluetooth Low Energy transmitter.

[0024] The electronic device of the present invention may be configured such that when the load switch is turned on, the application load executes a start-up sequence and then an activity sequence, the activity sequence including transmitting information to a network of multiple wireless receivers.

[0025] The electronic device of the present invention may be configured such that the information transmitted includes at least one of a beacon signal, data collected from at least one sensor involved in the application load, data collected from at least one sensor and stored in a memory involved in the application load, data collected from at least one actuator involved in the application load, data collected from at least one actuator and stored in a memory involved in the application load, and a measured ambient illuminance level, or any combination thereof.

[0026] The electronic device of the present invention may be configured such that the application load comprises a control unit connected to a primary activity functional load.

[0027] The electronic device of the present invention may be configured so that the control unit and the main activity functional load exchange information.

[0028] The electronic device of the present invention may be configured so that the control unit includes at least one of a field programmable gate array (FPGA), a microcontroller, and a logic unit, or any combination thereof.

[0029] The electronic device of the present invention may be configured such that the additional voltage detector and the output of the load switch are connected at an additional common point, and the additional voltage detector measures the voltage at the additional common point.

[0030] The electronic device of the present invention may be configured such that the additional voltage detector and the application load are configured to execute an action sequence when the voltage measured at the additional common point rises to a level equal to or greater than a third voltage, and the additional voltage detector and the application load are further configured to not execute an additional action sequence when the voltage measured at the additional common point falls to a level equal to or less than a fourth voltage, the third voltage being greater than the second voltage, the fourth voltage being greater than the second voltage, and the third voltage being greater than the fourth voltage.

[0031] The electronic device of the present invention may include a timer connected to the application load.

[0032] The electronic device of the present invention may be set such that the timer and the application load are configured to initiate a countdown sequence on the timer during the start-up sequence.

[0033] The electronic device of the present invention may be set such that the timer and the application load are configured to initiate a countdown sequence on the timer during the activity sequence.

[0034] The electronic device of the present invention may be configured such that the timer and the application load are configured to execute at least one sequence of actions when all of the following conditions are met: a countdown sequence on the timer is completed; the additional voltage detector measures a voltage at the additional common point that is less than the third voltage; and the voltage detector measures a voltage at the common point that is greater than the second voltage.

[0035] The electronic device of the present invention may involve a method for optimizing power supply to an application load, the electronic device comprising a photovoltaic power generating unit, an energy storage unit, a voltage detector, a load switch, and an application load, the application load having a startup sequence and an activity sequence, the method including charging the energy storage unit from the photovoltaic power generating unit while the load switch is off, turning on the load switch when the voltage detector detects a voltage equal to or greater than a first voltage, executing the startup sequence after turning on the load switch, executing at least one activity sequence after the startup sequence, and not executing an activity sequence and turning off the load switch when the voltage detector detects a voltage equal to or less than a second voltage, the first voltage being greater than the second voltage.

[0036] The electronic device of the present invention disclosed above includes an additional voltage detector, and the method further includes: i) when the additional voltage detector detects a voltage less than a third voltage and ii) when the voltage detector detects a voltage greater than the second voltage, entering an idle mode after the start-up sequence; when the additional voltage detector detects a voltage equal to or greater than the third voltage, terminating the idle mode and executing an active sequence; and when the additional voltage detector detects a voltage greater than a fourth voltage, executing at least one additional active sequence; i) when the additional voltage detector detects a voltage equal to or less than the fourth voltage and ii) when the voltage detector detects a voltage greater than the second voltage, entering an idle mode without executing an active sequence; and when the voltage detector detects a voltage equal to or less than the second voltage, terminating the idle mode and turning off the load switch, wherein the third voltage is greater than the second voltage, the fourth voltage is greater than the second voltage, and the third voltage is greater than the fourth voltage.

[0037] The electronic device of the present invention disclosed above includes an additional voltage detector and a timer, and the method further includes starting a countdown in the timer after executing the start-up sequence, and entering an idle mode after starting the countdown in the timer when i) the additional voltage detector detects a voltage less than a third voltage, ii) the countdown in the timer has not ended, and iii) the voltage detector detects a voltage greater than the second voltage, and ending the idle mode and executing an activity sequence when either i) the additional voltage detector detects a voltage equal to or greater than the third voltage or ii) the countdown in the timer ends, and resuming the countdown with the timer during the sequence; executing at least one additional active sequence when the additional voltage detector detects a voltage greater than a fourth voltage; entering the idle mode without executing the active sequence when i) the additional voltage detector detects a voltage less than or equal to the fourth voltage and ii) the voltage detector detects a voltage greater than the second voltage; and exiting the idle mode and turning off the load switch when the voltage detector detects a voltage less than or equal to the second voltage, wherein the third voltage is greater than the second voltage, the fourth voltage is greater than the second voltage, and the third voltage is greater than the fourth voltage.

[0038] The electronic device comprises a photovoltaic power generating unit, an energy storage unit, a voltage detector, a load switch, and an application load, the application load having a startup sequence and an activity sequence, and the electronic device is configured to perform any of the methods disclosed above. [Brief description of the drawings]

[0039] Some preferred embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1] 1 is a graph illustrating three different ambient illumination ranges. [Diagram 2] FIG. 1 is a block diagram of an electronic device according to a first embodiment. [Diagram 3] FIG. 4 is an operation flow diagram of the electronic device of the first embodiment. [Figure 4] 2 is a table showing example application workloads and example activity sequences; [Diagram 5] 4 is a graph showing the operation of the electronic device of the first embodiment. [Figure 6] FIG. 11 is a block diagram of an electronic device according to a second embodiment. [Figure 7] FIG. 11 is an operation flow diagram of the electronic device of the second embodiment. [Figure 8] 10 is a graph showing the operation of the electronic device of the second embodiment. [Figure 9] 1 is a table showing various relationships between various voltages. [Figure 10] FIG. 13 is a block diagram of an electronic device according to a third embodiment. [Figure 11] FIG. 11 is an operation flow diagram of an electronic device according to a third embodiment. [Figure 12a] 13 is a graph showing the operation of the electronic device of the third embodiment. [Figure 12b] 13 is an additional graph showing the operation of the electronic device of the third embodiment. [Figure 13] 1 is a graph showing the relative efficiency of three example electronic devices. [Figure 14] 1 is a table showing the relative advantages of three example electronic devices. [Figure 15] FIG. 1 is a block diagram of a first embodiment of an electronic device having an example application workload. [Figure 16] FIG. 2 is a block diagram of a second embodiment of an electronic device having an exemplary application workload. [Figure 17] FIG. 13 is a block diagram of a third embodiment of an electronic device having an example application workload. [Figure 18a] FIG. 13 is a block diagram of an electronic device according to a fourth embodiment. [Figure 18b] FIG. 13 is a block diagram of an electronic device according to a fourth developed embodiment. [Figure 19a] FIG. 13 is a block diagram of an electronic device according to a fifth embodiment. [Figure 19b] FIG. 13 is a block diagram of an electronic device according to a fifth embodiment of the present invention. [Figure 20] It is a block diagram of an electronic device according to a sixth embodiment. [Figure 21] It is a block diagram of an electronic device according to a seventh embodiment.

Embodiments for Carrying Out the Invention

[0040] FIG. 1 is a graph showing three different ambient illuminance ranges (that is, three different ambient lighting ranges). LxR1 represents the first ambient illuminance value range, with the lower illuminance value being LxR1L and the upper illuminance value being LxR1U. LxR2 represents the second ambient illuminance value range, with the lower illuminance value being LxR2L and the upper illuminance value being LxR2U. LxR3 represents the third ambient illuminance value range, with the lower illuminance value being LxR3L and the upper illuminance value being LxR3U. The range of LxR1 and the range of LxR2 may partially overlap. The range of LxR2 and the range of LxR3 may partially overlap. The range of LxR1 and the range of LxR3 do not overlap. The conditions of LxR1L < LxR2L < LxR3L and LxR1U < LxR2U < LxR3U are also complied with. For the sake of easy understanding of the following description, LxR1 may represent a range of low ambient illuminance values less than 200 lux. LxR1 may represent the illuminance level measured in corridors, storage rooms, warehouses, stairways, elevators, etc. For the sake of easy understanding of the following description, LxR2 may represent a range of intermediate ambient illuminance values that may be in the range of 200 lux to 500 lux. LxR2 may represent the illuminance level measured in classrooms, conference rooms, offices, etc. For the sake of easy understanding of the following description, LxR3 may represent a range of high ambient illuminance values that may exceed 500 lux. LxR3 may represent the illuminance level measured in kitchens, laboratories, workplaces, supermarkets, etc. LxR3 may represent the illuminance level measured anywhere as long as it is a room designated for medical procedures such as an operating room. The low, medium, and high ambient illuminance ranges may include illumination from artificial light sources (e.g., LEDs, fluorescent lamps, etc.), illumination from natural light sources (e.g., the sun), or any combination thereof.

[0041] In this disclosure, various ultra-low power electronic devices are disclosed. A metric that can be used to compare the performance of various ultra-low power electronic devices is circuit efficiency. For the purposes of this disclosure, circuit efficiency is defined as proportional to the average repetition rate of an activity sequence for a given constant illumination level. If the activity sequence includes transmitting information to a wireless network, the average repetition rate of the activity sequence must not exceed a maximum value defined by standard protocols. For example, the maximum repetition rate of a non-connected (i.e., wireless) beacon signal is 10 Hz.

[0042] FIG. 2 is a block diagram of an electronic device 20 of a first embodiment, which includes a photovoltaic power generation unit 21, an energy storage unit 22, a voltage detector 23, a load switch 24, and an application load 25. The voltage detector 23 is connected to N1 (node ​​1) to detect the voltage at N1 (node ​​1). Node 1 is a common point. The voltage detector 23 is also connected to the load switch 24 via SIG1 (signal 1). The power line 26 supplies power to all units included in the application load 25. The power line 26 supplies power to all units involved in the application load 25. The application load 25 may use the power provided from the power line 26 to supply power to any unit (e.g., sensor, actuator, etc.) involved in the application load 25. The photovoltaic power generation unit 21 is connected to N1. The energy storage unit 22 is connected to N1. The input of the load switch 24 is connected to N1. The photovoltaic power generation unit 21, the energy storage unit 22, and the voltage detector 23 are connected to the input of the load switch 24. Generally, the output of the load switch 24 is coupled to an application load 25 via a power line 26 .

[0043] The photovoltaic power generating unit 21 may include at least one photovoltaic element. The photovoltaic power generating unit 21 may have a general structure, but if the electronic device is mainly installed indoors, it is preferable that the photovoltaic power generating unit 21 is optimized for the light spectrum generated under indoor lighting conditions. The photovoltaic power generating unit 21 may generate a maximum of 10 μW of power at 200 lux. The photovoltaic power generating unit 21 may generate a maximum of 5 μW of power at 200 lux. The photovoltaic power generating unit 21 may generate a maximum of 2 μW of power at 200 lux.

[0044] The energy storage unit 22 may include at least one battery, and / or one rechargeable battery, and / or at least one capacitor and / or at least one supercapacitor. To reduce power consumption, size and cost of electronic devices, it is often preferable to have the energy storage unit 22 consist only of capacitors. If the energy storage unit 22 consists only of capacitors, the total capacity may be less than 500 μF, preferably less than 250 μF. The photovoltaic unit 21 collects energy from ambient lighting and stores this energy in the energy storage unit 22.

[0045] The voltage detector 23 is configured to turn on the load switch 24 at a voltage greater than a first voltage. The first voltage may be V1A. The voltage detector 23 is further configured to turn off the load switch 24 at a voltage less than or equal to a second voltage, the first voltage being greater than the second voltage. The second voltage may be V1B. The voltage detector 23 may have a hysteresis of less than 600 mV. The voltage detector 23 may have a hysteresis of less than 400 mV. The voltage detector 23 may have a hysteresis of less than 200 mV. The load switch 24 may be an integrated load switch.

[0046] The application load 25 may include at least one controller. The controller may include at least one field programmable gate array (FPGA) and / or at least one microcontroller and / or at least one logic unit. The application load 25 may include a wireless communication unit (not shown), which may be a Bluetooth Low Energy (BLE) wireless communication unit. The application load 25 may be associated with at least one sensor and / or one actuator. The application load 25 may be associated with at least one sensor and / or actuator that is within the application load (i.e., internal sensors and / or actuators not shown in FIG. 2) and / or the application load 25 may be associated with at least one sensor and / or actuator that is external to the application load 25 but connected to the application load 25 (i.e., external sensors and / or actuators not shown in FIG. 2). All sensors (i.e., internal and external sensors) involved in application load 25 may collect data related to at least one of the following: orientation, acceleration, temperature, humidity, air pressure, light (illuminance, lux), magnetic field, sound, infrared, ultraviolet, gas (e.g., CO, CO2, methane, etc.), proximity, images (i.e., camera), and user input. All actuators (i.e., internal and external actuators) involved in application load 25 may collect data related to at least one of the following: push buttons, switches, touch sensors, and user input.

[0047] In general, sensors and / or actuators involved in application load 25 may be configured to receive input from a user. For example, an actuator may be a button configured to detect a press by a user. For example, an actuator may be a switch configured to detect a current switch state and a change to the switch state implemented by a user. A sensor may be a microphone configured to detect sounds from the environment and / or the user.

[0048] The application load 25 may provide power to at least one sensor and / or actuator. When the load switch 24 is turned on, the electronic device 20 of the first embodiment is configured such that the application load 25 completes a wake-up sequence and then completes at least one activity sequence. The maximum current consumed by the application load 25 during the wake-up sequence is often less than 50 mA, but preferably less than 1 mA. The maximum energy consumed by the application load 25 to complete the wake-up sequence may be less than 100 μJ, but preferably less than 10 μJ. The maximum current consumed by the application load 25 during an activity sequence may be less than 50 mA, but preferably less than 1 mA. The maximum energy consumed by the application load 25 to complete a single activity sequence may be less than 50 μJ, but preferably less than 20 μJ.

[0049] Figure 3 is a flowchart 30 showing the operation of the electronic device 20 of the first embodiment shown in Figure 2. Item 31 of the flowchart indicates that the photovoltaic section 21 generates the charge to be stored in the energy storage section 22 (that is, the energy generated by the photovoltaic section 21 is stored in the energy storage section 22). Item 32 of the flowchart indicates that the voltage detector 23 measures the voltage at node 1. The voltage at node 1 is represented by V(N1). As shown in items 32 and 33 of the flowchart, when V(N1)≥V1A, the voltage detector 23 sends an activation signal (SIG1 = ACTIVE) to the load switch 24, turning on the load switch 24. The predetermined voltage V1A is in the range of VMP±20%, preferably in the range of VMP±10%, where VMP is the voltage at the maximum power point of the photovoltaic section 21. As shown in items 32 and 37 of the flowchart, when V(N1)≥V1A is not satisfied (that is, V(N1)<V1A), the voltage detector 23 sends a deactivation signal (SIG1 = INACTIVE) to the load switch 24, turning off the load switch 24. If the load switch 24 remains in the off state (SIG1 = INACTIVE), the photovoltaic section 21 continues to generate charge and it is stored in the energy storage section 22. On the other hand, if the load switch 24 remains in the on state, as shown in items 34 and 35 of the flowchart, the applied service load 25 can receive sufficient energy from the energy storage section 22 and / or the photovoltaic section 21 to execute the startup sequence and at least one active sequence. Usually, the electronic device of each embodiment described in this specification is configured to execute until the startup sequence is completed and at least one active sequence is completed when the load switch 24 is on, so it can contribute to the optimization of the useful work executed by the collected energy. If the electronic device of the embodiment described in this specification cannot complete the startup sequence due to insufficient collected energy, it means that the amount of useful work executed by the electronic device has not been optimized. If the electronic device of the embodiment described in this specification cannot complete the started active sequence due to insufficient collected energy, it means that the amount of useful work executed by the electronic device has not been optimized.If the electronic device of the embodiment described herein completes the wake-up sequence but is unable to complete at least one activity sequence due to lack of harvested energy, the amount of useful work performed by the electronic device is not optimized. The wake-up sequence may include loading a program into a volatile memory in the control unit (not shown in FIG. 2). The wake-up sequence may include a clock stabilization process. Item 35 of the flow diagram shows the application load 25 performing a predetermined activity sequence, which may include transmitting information to at least one additional device (not shown) via the wireless communication unit. If the activity sequence includes transmitting information via the Bluetooth Low Energy unit, a timer sequence is often configured within the activity sequence to ensure that no violation of the Bluetooth protocol related to the transmission repetition rate occurs. If V(N1)>V1B, then additional activity sequences are performed as shown in items 35 and 36 of the flow diagram. To contribute to optimizing the useful work performed by the harvested energy, if V(N1)>V1B, the electronic device 20 of the first embodiment is configured to perform and complete at least one additional activity sequence. Typically, the electronics of the embodiments described herein are configured such that an activity sequence is initiated only if the electronics of the embodiment have sufficient energy to complete the activity sequence. As shown in flow chart items 36 and 37, if V(N1)>V1B is not true (i.e., V(N1) is not greater than V1B), the voltage detector 23 sends an inactive signal (SIG1=INACTIVE) to the load switch 24, which causes the load switch 24 to turn off. Whenever SIG1=INACTIVE, the photovoltaic unit 21 generates charge, which is stored in the energy storage unit 22, as shown in flow chart item 31. Flow chart item 37 may be considered as the start of flow chart 30.

[0050] FIG. 4 shows four examples (Example 4.1-Example 4.4) of application workloads with participating activity sequences. Examples 4.1-Example 4.4 may be used in combination with any electronic device disclosed herein. The application workload of Example 4.1 includes a wireless transmitter. The activity sequence of Example 4.1 includes transmitting a location beacon to a wireless receiver (not shown in this disclosure) via a wireless communication unit (not shown in this disclosure). The application workload of Example 4.2 includes at least one sensor (i.e., an internal sensor or an external sensor) participating therein. The activity sequence of Example 4.2 includes transmitting information collected by the sensor to another device (not shown in this disclosure). The application workload of Example 4.3 includes a wireless transmitter and at least one sensor participating therein. The activity sequence of Example 4.3 includes transmitting a location beacon to multiple wireless receivers (not shown in this disclosure) and transmitting information collected by the one or more participating sensors to each wireless receiver (not shown in this disclosure). The application workload of Example 4.4 includes a wireless transmitter and at least one sensor associated therewith. The activity sequence of Example 4.4 includes transmitting information collected by said one or more participating sensors to a number of wireless receivers (not shown in this disclosure). The transmitted information collected by said one or more participating sensors may also be used as a location beacon. Utilizing the transmission of information collected by said one or more participating sensors to also provide location information for the electronic device may further reduce power consumption of any electronic device disclosed herein since the amount of data transmitted may be minimized. Thus, while the functionality of Examples 4.3 and 4.4 may be the same, the activity sequence of Example 4.4 may consume less power than the activity sequence of Example 4.3.

[0051] A first advantage of the electronic device 20 of the first embodiment is its ability to operate (i.e., execute at least one sequence of activities) properly at low ambient illuminance levels (i.e., low ambient light illumination levels). In other words, the electronic device of the first embodiment has excellent circuit efficiency even at low ambient illuminance levels. Referring to FIG. 1, the electronic device 20 of the first embodiment has the ability to operate in a first illuminance range LxR1 where LxR1U is 200 lux, and preferably, the electronic device 20 of the first embodiment has the ability to operate properly when LxR1L is 20 lux. The electronic device 20 of the first embodiment also has the ability to operate properly at all ambient illuminance values ​​above LxR1L, so that the electronic device 20 of the first embodiment can operate properly within the illuminance ranges of LxR1, LxR2, and LxR3. A second advantage of the electronic device 20 of the first embodiment is that the number of components required is relatively small, so that the electronic device 20 of the first embodiment has a lower cost and weight compared to the electronic device designs of the other embodiments disclosed below.

[0052] FIG. 5 is a graph showing the operation of the first embodiment electronic device 20 at a constant ambient lighting level. This constant lighting level may be in the range of L×R2. With reference to FIG. 5, Ipv is the current generated by the photovoltaic unit 21. With reference to FIG. 5, Ibuf is the sum of the current consumed by the voltage detector 23 and the current consumed by the load switch 24. With reference to FIG. 5, Iapp is the current consumed by the application load 25. With reference to FIG. 5, Iload is the total current consumed by all loads in the first embodiment electronic device 20. The left vertical axis shows how the voltage V(N1) at node 1 changes over time (solid line). The right vertical axis shows how the quantity Ipv-Iload changes as a function of time (thick dashed line). Various values ​​(e.g., V1A, V1B, etc.) are shown as light dashed lines. When the amount of Ipv-Iload is greater than 0, the energy generated by the photovoltaic power generation unit 21 is greater than the energy consumed by all the loads in the electronic device 20 of the first embodiment (i.e., the electronic device 20 generates more energy than it consumes). When the amount of Ipv-Iload is less than 0, the energy generated by the photovoltaic power generation unit 21 is less than the energy consumed by all the loads in the electronic device 20 (i.e., the electronic device 20 generates less energy than it consumes). When V(N1)>V1B is not true (i.e., V(N1) is not greater than V1B), the load switch 24 is always off and the energy generated by the photovoltaic power generation unit 21 is stored in the energy storage unit 22. At the beginning of the time interval 51T1 (i.e., time=0), there is no energy stored in the energy storage unit 22. In the time interval 51T1, the load switch 24 is off. Since Ipv-Ibuf>0 in the time interval 51T1, V(N1) increases over time from 0 to V1A. Since the ambient lighting is constant, the value of Ipv-Iload is constant and equal to Ipv-Ibuff.At the beginning of time interval 51T2, V(N1)≧V1A, so the voltage detector 23 turns on the load switch 24 (SIG1=ACTIVE) to allow the application load 25 to consume energy from the photovoltaic power generation unit 21 and / or the energy storage unit 22. As a result, during time interval 51T2, the application load 25 first executes a startup sequence (i.e., Ipv-Iload=Ipv-Ibuf-Iapp_bootup) and then executes at least one active sequence (i.e., Ipv-Iload=Ipv-Ibuf-Iapp). As shown in time interval 51T2, the power consumption of a startup sequence is typically greater than the power consumption of an active sequence. Thus, time interval 51T2 shows that V(N1) decreases more rapidly over time during a startup sequence than for an active sequence. The linear change of V(N1) over time is only for illustrative purposes and may not reflect the complexity of power consumption. First, in time interval 51T2, the value of Ipv-Iload is equal to Ipv-Ibuf-Iapp_bootup, and then the amount of Ipv-Iload is equal to Ipv-Ibuf-Iapp. In time interval 51T2, the energy consumed by electronic device 20 is greater than the energy generated by electronic device 20, so the value of Ipv-Ibuf-Iapp_bootup and the value of Ipv-Ibuf-Iapp are negative. Meanwhile, the value of Ipv-Iload is equal to Ipv-Ibuf-Iapp, so at least one active sequence is executed. At the beginning of time interval 51T3, the voltage detector 23 turns off the load switch 24 (SIG1=INACTIVE) because V(N1)>V1B is not. In time interval 51T3, V(N1) increases with time because Ipv-Ibuf>0. Since the ambient illumination is constant, the value of Ipv-Iload is constant and equal to Ipv-Ibuff. Time interval 51T4 shows the same operations as time interval 51T2 described above.Time interval 51T5 shows the same operations as time interval 51T3 described above.

[0053] FIG. 6 is a block diagram of the electronic device 60 of the second embodiment. The electronic device 60 of the second embodiment may be the same as the electronic device 20 of the first embodiment, except that the electronic device 60 of the second embodiment includes an additional voltage detector 61. The voltage detector 61 is connected to N2 (node ​​2) to detect the voltage at N2. Node 2 is an additional common point. Node 2 may be considered as the output of the load switch 24. The voltage detector 61 is also connected to the application load 25 via SIG2 (signal 2). The additional voltage detector 61 is configured to activate (i.e., execute) at least one activity sequence at a voltage equal to or greater than the third voltage (SIG2=ACTIVE). Typically, for example, in the electronic device disclosed herein, whenever an activity sequence is "activated," the electronic device is configured to have sufficient energy to execute the activity sequence to completion. In other words, whenever an activity sequence is "activated," the electronic device is configured to execute a positive integer number of activity sequences. Completing a positive integer number of activity sequences contributes to optimizing the useful work executed by the harvested energy. The additional voltage detector 61 is configured not to activate the activity sequence at a voltage equal to or less than the fourth voltage. The third voltage is often greater than the fourth voltage. Typically, for example, in electronic devices disclosed herein, "deactivating" an activity sequence prevents additional activity sequences from being executed until a sufficient amount of energy is subsequently harvested. Typically, for example, in electronic devices disclosed herein, "deactivating" an activity sequence does not prevent completion of an activity sequence that has already been started. Configuring each electronic device in the disclosed embodiments to complete all initiated activity sequences may contribute to optimizing useful work performed by the harvested energy. In other words, completing a positive integer number of activity sequences may contribute to optimizing useful work performed by the harvested energy.

[0054] Voltage detector 61 may have a hysteresis of less than 600 mV. Voltage detector 61 may have a hysteresis of less than 400 mV. Voltage detector 61 may have a hysteresis of less than 200 mV. Voltage detector 61 may be the same as voltage detector 23.

[0055] FIG. 7 is a flowchart 70 showing the operation of the electronic device 60 of the second embodiment shown in FIG. 6. Item 71 of the flowchart indicates that the photovoltaic section 21 generates charges and they are stored in the energy storage section 22 (that is, the energy generated by the photovoltaic section 21 is stored in the energy storage section 22). Item 72 of the flowchart indicates that the voltage detector 23 measures the voltage at node 1. The voltage at node 1 is represented by V(N1). When V(N1)≧V1A, as shown in flowchart item 73, the voltage detector 23 sends a signal (SIG1 = ACTIVE) to the load switch 24 to turn on the load switch. The first predetermined voltage V1A can be within the range of VMP±20%, preferably within the range of VMP±10%, where VMP is the voltage at the maximum power point of the photovoltaic section 21. When V(N1)≧V1A is not satisfied (that is, V(N1)<V1A), as shown in flowchart items 72 and 712, the voltage detector 23 sends an inactive signal (SIG1 = INACTIVE) to the load switch 24 to turn off the load switch 24. If the load switch 24 remains off, the photovoltaic section 21 continues to generate charges and they are stored in the energy storage section 22. On the other hand, if the load switch 24 remains on, as shown in flowchart item 74, the applied service load 25 receives sufficient energy from the energy storage section 22 and / or the photovoltaic section 21 to execute a startup sequence. The startup sequence may include deploying a program in a volatile memory (not shown in FIG. 6) within the control unit. The startup sequence may include a clock stabilization process. Flowchart item 75 indicates that the applied service load 25 enters the idle mode. The purpose of the idle mode is to minimize the number of executions of the startup sequence, which can contribute to the optimization of useful work executed by the collected energy. No additional startup sequence is required to transition from the idle mode to the active sequence. Flowchart item 76 indicates that the voltage detector 61 measures the voltage at node 2. The voltage at node 2 is represented by V(N2).If V(N2)≧V2A, the voltage detector 61 sends a signal (SIG2=ACTIVE) to the application 25, causing the application to execute an activity sequence, as shown in flow diagram items 76, 77, and 78, respectively. The predetermined activity sequence shown in flow diagram item 78 may include any of the example activity sequences shown in FIG. 4. The predetermined activity sequence shown in flow diagram item 78 may include transmitting information via the wireless communication portion to at least one additional device (not shown). If the activity sequence includes transmitting information via the Bluetooth Low Energy portion, a timer sequence is often configured within the activity sequence to ensure that no violations of the Bluetooth protocol related to transmission repetition rate occur. The activity sequence may include any of the example activity sequences shown in FIG. 4. If V(N2)≧V2A (i.e., V(N2)<V2A)かつV(N1)> If V(N2)>V2B, application load 25 remains in idle mode, as shown in flow diagram 70 by the loop of flow diagram items 75, 76, and 711. After application load 25 executes the sequence of activities shown in flow diagram item 78, another sequence of activities is executed by application load 25 if V(N2)>V2B, as shown in flow diagram item 79. If V(N2)>V2B (i.e., V(N2) is not greater than V2B), voltage detector 61 sends a signal (SIG2=INACTIVE) to application load 25 to prevent application load 25 from executing additional sequences of activities, as shown in flow diagram items 79 and 710. If V(N1)>V1B, as shown in flow diagram item 711, application load 25 enters idle mode, as shown in flow diagram item 75. As shown in flow diagram item 711, if V(N1)>V1B is not true, then the voltage detector 23 sends a signal (SIG1=INACTIVE) to turn off the load switch 24, as shown in flow diagram item 712. When the load switch 24 is turned off, the photovoltaic unit 21 generates charge which is stored in the energy storage unit 22, as shown in flow diagram item 71. Flow diagram item 712 may be considered the start of flow diagram 70.

[0056] FIG. 8 is a graph showing the operation of the electronic device 60 of the second embodiment at a constant ambient lighting level. This constant lighting level may be in the range of LxR2. With reference to FIG. 8, Ipv is the current generated by the photovoltaic unit 21. Ibuf is the sum of the current consumed by the voltage detector 23 and the load switch 24. Iapp is the current consumed by the active sequence of the application load 25. Iload is the total current consumed by all the loads in the electronic device 60 of the second embodiment. Iapp_idle is the current consumed when the application load 25 is in an idle mode. Iapp_bootup is the current consumed when the application load 25 executes a boot-up sequence. The current consumed by the voltage detector 61 is always small compared to the various currents consumed by the application load 25, so it is ignored for simplicity. The left vertical axis shows how the voltage V(N1) at node 1 changes over time during the time interval 81T1 (solid line). The left vertical axis shows how the voltage V(N2) at node 2 changes over time (solid line) during time intervals 81T2, 81T3, 81T4, and 81T5. The right vertical axis shows how the amount of Ipv-Iload changes as a function of time (thick dashed line). Various values ​​(e.g., V1A, V1B, etc.) are shown with thin dashed lines. If the amount of Ipv-Iload is greater than 0, the energy generated by the photovoltaic unit 21 is greater than the energy consumed by all loads in the electronic device 60 of the second embodiment (i.e., the electronic device 60 generates more energy than it consumes). If the amount of Ipv-Iload is less than 0, the energy generated by the photovoltaic unit 21 is less than the energy consumed by all loads in the electronic device 60 (i.e., the electronic device 60 generates less energy than it consumes). When V(N1) is less than or equal to V1B, the load switch 24 is always off and the energy generated by the photovoltaic power generation unit 21 is stored in the energy storage unit 22. At the beginning of the time interval 81T1 (i.e., time = 0), there is no energy stored in the energy storage unit 22.During time interval 81T1, the load switch 24 is off. During time interval 81T1, since Ipv-Ibuf>0, V(N1) increases over time from 0 to V1A. Since the ambient illuminance is constant, the value of Ipv-Iload is constant and equal to Ipv-Ibuff. At the very beginning of time interval 81T2, since V(N1)=V1A, the voltage detector 23 turns on the load switch 24 (SIG1=ACTIVE), allowing the application load 25 to consume energy from the photovoltaic unit 21 and / or the energy storage unit 22. As a result, during time interval 81T2, the application load 25 first executes a startup sequence (the startup sequence occurs when Ipv-Iload=Ipv-Ibuf-Iapp_bootup) and then executes at least one active sequence (the active sequence occurs when Ipv-Iload=Ipv-Ibuf-Iapp). As shown in time interval 81T2, the power consumption of a boot sequence is typically greater than the power consumption of an active sequence. Thus, time interval 81T2 illustrates that during a boot sequence, V(N2) decreases more rapidly with time than during an active sequence. The linear changes of V(N1) and V(N2) with time are for illustrative purposes only and may not reflect the complexity of power consumption. During time interval 81T2, the energy consumed by electronic device 60 is greater than the energy generated by electronic device 60, so the values ​​of Ipv-Ibuf-Iapp_bootup and Ipv-Ibuf-Iapp are negative, respectively. Meanwhile, the value of Ipv-Iload is equal to Ipv-Ibuf-Iapp, so at least one active sequence is executed. At the beginning of time interval 81T3, the value of V(N2) is not greater than V2B, but is greater than V1B, so application load 25 enters an idle mode. In the idle mode, the value of Ipv-Iload is positive and equal to Ipv-Ibuf-Iapp_idle, so the energy consumed by electronic device 60 is less than the energy generated by electronic device 60, and so the value of V(N2) increases over time. At the beginning of time interval 81T4, V(N2)=V2A, so application load 25 is executing at least one activity sequence.Time interval 81T4 differs from time interval 81T2 because no wake-up sequence is required when transitioning from an idle mode to an active mode. Because no wake-up sequence is performed in 81T4, second embodiment electronic device 60 may have higher circuit efficiency in some ambient lighting conditions than first embodiment electronic device 20. Time interval 81T5 illustrates the same operation as time interval 81T3 described above.

[0057] The duty cycle (DC) of the SIG2 signal corresponds to the percentage of time that the activity sequence is executed. The electronics 60 of the second embodiment automatically adapts to the current supplied by the photovoltaic unit 21, and thus to the ambient lighting conditions, so that the repetition rate of the activity signal is optimized (i.e., the circuit efficiency is optimized). On average, it can be seen that the total current consumption of the electronics of the embodiment disclosed herein is balanced with the current generated by the photovoltaic unit 21, Ipv=Ibuf+DCxIapp+(1-DC)xIapp_idle.

[0058] FIG. 9 is a table showing three predetermined voltage configurations (Examples 9.1-9.3) with the relative relationships between the predetermined voltages V1A, V1B, V2A, and V2B, and example voltages for V1A, V1B, V2A, and V2B. In general, the exemplary configurations of FIG. 9 optimize the power delivery and therefore the useful work performed by the harvested energy at a given ambient illumination level. In general, the exemplary configurations of FIG. 9 optimize the circuit efficiency at a given ambient illumination level. For the electronic device 60 and all subsequent tags disclosed herein, it has been found that the following general design rules contribute to optimizing both the power delivery and the circuit efficiency: V1A>V1B, V2A>V1B, V2B>V1B, and V2A≧V2B. With reference to FIG. 1 and FIG. 9, multiple experiments have revealed that Example 9.1 achieves the highest circuit efficiency at high ambient illumination values ​​(i.e., the third ambient illumination value range, LxR3). 1 and 9, multiple experiments have revealed that Example 9.2 provides the best circuit efficiency at intermediate ambient illuminance values ​​(i.e., second ambient illuminance value range, LxR2). 1 and 9, multiple experiments have revealed that Example 9.3 provides the best circuit efficiency at low ambient illuminance values ​​(i.e., first ambient illuminance value range, LxR1). For low cost operation, it is preferable to predetermine the constant values ​​of VIA, V1B, V2A, and V2B.

[0059] FIG. 10 is a block diagram of the electronic device 100 of the third embodiment. The electronic device 100 of the third embodiment may be the same as the electronic device 60 of the second embodiment, except that the third embodiment 100 has a timer 101. The timer 101 and the application load 25 are connected by SIG3 (signal 3) and SIG4 (signal 4). FIG. 10 shows the timer 101 external to the application load 25. If the timer 101 is external to the application load, the application load 25 may provide power to the timer 101 via SIG3 and / or SIG4. Alternatively, the timer 101 may be an internal peripheral device, such as a real-time clock (RTC) timer, which is an integral part of the control unit and thus part of the application load 25. The application load 25 is configured to send a signal (SIG3) to the timer to start or resume a countdown sequence in the timer during a wake-up sequence. The application load 25 is also configured to send a signal (SIG3) to the timer to start or resume a countdown sequence in the timer during an activity sequence. The duration of the countdown period can be predetermined and may be 60 seconds, preferably 30 seconds. Upon completion of the countdown on the timer 101, the timer 101 is configured to send a signal (SIG4) to the application 25 to activate (i.e., execute) at least one sequence of actions.

[0060] FIG. 11 is a flowchart 110 showing the operation of the electronic device 100 of the third embodiment shown in FIG. 10. Item 111 of the flowchart indicates that the photovoltaic section 21 generates charges and they are stored in the energy storage section 22 (that is, the energy generated by the photovoltaic section 21 is stored in the energy storage section 22). Item 112 of the flowchart indicates that the voltage detector 23 measures the voltage at node 1. The voltage at node 1 is represented by V(N1). When V(N1)>V1A, as shown in item 113 of the flowchart, the voltage detector 23 sends a signal (SIG1 = ACTIVE) to the load switch 24 to turn on the load switch. The first predetermined voltage V1A is within the range of VMP±20%, preferably within the range of VMP±10%, where VMP is the voltage at the maximum power point of the photovoltaic section 21. When V(N1)>V1A is not satisfied (that is, V(N1)<V1A), as shown in items 112 and 1112 of the flowchart, the voltage detector 23 sends an inactive signal (SIG1 = INACTIVE) to the load switch 24 to turn off the load switch 24. If the load switch 24 remains off, the photovoltaic section 21 continues to generate charges and they are stored in the energy storage section 22. On the other hand, if the load switch 24 remains on, as shown in item 114 of the flowchart, the applied service load 25 receives sufficient energy from the energy storage section 22 and / or the photovoltaic section 21 to execute a startup sequence. As shown in item 114 of the flowchart, the applied service load 25 sends a signal (SIG3) to the timer 101 to start a timer countdown sequence (TCD·SIG3 + TCD start). In item 114 of the flowchart, SIG4 is set to INACTIVE. The startup sequence may include deploying a program in a volatile memory in a control unit (not shown in FIG. 10). The startup sequence may include a clock stabilization process. Item 115 of the flowchart indicates that the applied service load 25 enters the idle mode. No additional startup sequence is required to transition from the idle mode to the active sequence. Item 116 of the flowchart indicates that the voltage detector 61 measures the voltage at node 2. The voltage at node 2 is represented by V(N2).If V(N2)≧V2A, the voltage detector 61 sends a signal (SIG2=ACTIVE) to the application load 25, causing the application load 25 to execute a predetermined sequence of activities, as shown in flow diagram items 117 and 118, respectively. The predetermined sequence of activities shown in flow diagram item 118 may include any of the example sequences of activities shown in FIG. 4. The predetermined sequence of activities shown in flow diagram item 118 may include transmitting information to at least one additional device (not shown) via the wireless communication section. If the sequence of activities includes transmitting information via the Bluetooth Low Energy section, a separate timer sequence (not shown) may be included in the sequence of activities to ensure that no violation of the Bluetooth protocol related to the transmission repetition rate occurs. If V(N2)≧V2A, and the timer 101 has not completed the countdown sequence, and V(N1)>V1B, the application load 25 remains in an idle mode, as shown in flow diagram 110 by the loop consisting of flow diagram items 115, 116, 1111, and 1113. However, as shown in flow chart items 116, 1113, and 1114, if V(N2)≧V2A and the timer 101 has completed its countdown sequence (TCD completed?=YES), the timer 101 sends a signal (SIG4=ACTIVE) to the application load. As shown in flow chart item 118, each time the application load 25 finishes executing an activity sequence, the application load 25 sends a signal (SIG3) to the timer 101, which restarts the timer countdown sequence (TCD·SIG3+TCD started) and sets SIG4 to INACTIVE. After the application load 25 has executed the activity sequence shown in flow chart item 118, if V(N2)>V2B in flow chart item 119, the application load 25 executes the activity sequence again. If V(N2)>V2B, then as shown in flow diagram item 1110, voltage detector 61 sends a signal (SIG2=INACTIVE) to application load 25 to prevent the application load from executing additional activity sequences.If V(N1)>V1B at flow diagram item 1111, then the application load 25 enters an idle mode, as shown in flow diagram item 115. If V(N1)>V1B is not true at flow diagram item 1111, then the voltage detector 23 sends a signal (SIG1=INACTIVE) to turn off the load switch 24, as shown in flow diagram item 1112. With the load switch 24 turned off, the photovoltaic unit 21 generates charge which is stored in the energy storage unit 22, as shown in flow diagram item 111. Flow diagram item 1112 may be considered the start of the flow diagram 110.

[0061] FIG. 12a shows a typical current vs. voltage graph for the electronic device 60 or electronic device 100 when the ambient illumination is at an intermediate value, e.g., LxR2. In FIG. 12a, the ambient illumination is high enough that the countdown of the timer 101 associated with the electronic device 100 is not completed (i.e., the countdown always restarts at the end of the activity sequence before it is completed). FIG. 12b shows a typical current vs. voltage graph for the electronic device 60 or electronic device 100 when the ambient illumination is at a low value, e.g., LxR1. In FIG. 12b, the ambient illumination is low enough that the countdown of the timer 101 associated with the electronic device 100 is completed, allowing the timer 101 to start the activity sequence (SIG4=ACTIVE). With reference to FIGS. 12a and 12b, Isc is the current consumed at a short circuit, I_V2a is the current consumed at voltage level V2a, and Voc is the voltage resulting at an open circuit. Other terms (Iapp_idle, Ibuf, V1A, V1B, V2A, V2B) are defined above. Referring to Figure 12b, the following two conditions are demonstrated: Condition 1: When the voltage is equal to V2A, the current consumption is I_V2a. I_V2a is less than Iapp_idle. Condition 2: When the voltage is equal to V1B, the current consumption is approximately equal to Isc. Isc is greater than Iapp_idle.

[0062] With reference to the electronic device 60 of the embodiment of FIG. 7, if both condition 1 and condition 2 are satisfied, the application load 25 will remain in the idle mode forever (assuming that the ambient lighting conditions do not change). With reference to the electronic device 100 of the embodiment of FIG. 11, if both condition 1 and condition 2 are satisfied, the timer 101 can end the countdown, so that it sends a signal (SIG4=ACTIVE) to the application load 25, so that the application load 25 executes the activity sequence. Thus, the advantage of the electronic device 100 of the third embodiment over the electronic device 60 of the second embodiment is that in a certain range of low ambient lighting conditions, the electronic device 100 can execute the activity sequence, but the electronic device 60 cannot execute the activity sequence. In other words, if the timer 101 is configured as described above, the result is that the electronic device 100 will not fall into the idle mode in a certain range of ambient lighting. By implementing the timer 101 as described above, the electronic device 100 can have a higher circuit efficiency than the electronic device 60 in a certain range of low ambient lighting conditions.

[0063] FIG. 13 is a graph of relative circuit efficiency versus ambient illuminance for the electronic device 20 of the first embodiment, the electronic device 60 of the second embodiment, and the electronic device 100 of the third embodiment. The electronic device 20 of the first embodiment has the best circuit efficiency at low ambient illuminance levels (i.e., less than 200 lux and in the range of LxR1). The electronic device 60 of the second embodiment and the electronic device 100 of the third embodiment have similar best circuit efficiency at intermediate ambient illuminance levels (i.e., 200 lux to 500 lux and in the range of LxR2). The electronic device 100 of the third embodiment has better circuit efficiency than the electronic device 60 of the second embodiment at low ambient illuminance levels (i.e., less than 200 lux and in the range of LxR1).

[0064] FIG. 14 shows a table comparing the relative advantages of the electronic device 20 of the first embodiment, the electronic device 60 of the second embodiment, and the electronic device 100 of the third embodiment. The value "1" in the table represents the best option. The value "2" in the table represents the second best option. The value "3" in the table represents the third best option. The electronic device 20 of the first embodiment is the least expensive electronic device and has the best circuit efficiency at low ambient illumination levels (i.e., less than 200 lux and in the range of LxR1). However, the electronic device 20 of the first embodiment has the worst circuit efficiency at medium and high ambient illumination levels (i.e., greater than 200 lux and in the ranges of LxR2 and LxR3). The electronic device 100 of the third embodiment is the most expensive electronic device, but has better circuit efficiency than the electronic device 60 of the second embodiment at low ambient illumination levels (i.e., less than 200 lux and in the range of LxR1). The electronic device of the second embodiment 60 and the electronic device of the third embodiment have comparable circuit efficiency at medium and high ambient illumination levels (ie, above 200 lux and in the ranges of LxR2 and LxR3).

[0065] FIG. 15 is a block diagram of an electronic device 150 of an advanced first embodiment in which advanced details are added to the application load 25. The application load 25 includes a control unit 151 and a primary active functional load 152. The control unit 151 is connected to the primary active functional load 152 by SIG7. The control unit 151 may send each signal to the primary active functional load 152 via SIG7. The primary active functional load 152 may send each signal to the control unit 151 via SIG7. In reality, SIG7 comprises multiple connections between the control unit 151 and the primary active functional load 152, but FIG. 15 shows only one connection for simplicity. The control unit 151 may include at least one field programmable gate array (FPGA) and / or at least one microcontroller and / or at least one logic unit. The primary active functional load 152 may include a wireless communication unit, such as a Bluetooth Low Energy wireless communication unit. The primary activity load 152 may comprise any of the exemplary application loads (Example 4.1, Example 4.2, Example 4.3, and Example 4.4) shown in FIG. 4. The primary activity load 152 may comprise or participate in at least one sensor and / or actuator described above. All of the sensors and actuators described above may be directly or indirectly connected to the control unit 151. The primary activity load 151 may comprise a passive load, such as an LED. The primary activity load 151 may comprise a low power display. In general, data collected by the sensors and / or actuators described above may be recorded (i.e., stored in memory) by the application load 25. More specifically, data collected by the sensors and / or actuators described above may be recorded (i.e., stored in memory) by the control unit 151 or the primary activity load 152. The recorded data from the sensors and / or actuators may be transmitted to an additional device (not shown) during a next activity sequence. The recorded data from the sensors and / or actuators may be transmitted to a network of multiple wireless receivers during a next activity sequence.Recording data from the sensors / actuators and only transmitting the recorded data in the next activity sequence can help optimize power delivery, circuit efficiency, and the overall amount of useful work performed with the harvested energy in the electronic devices disclosed herein. Alternatively, data collected by the above-mentioned sensors and / or actuators can be used immediately to initiate an activity sequence. However, there is no guarantee that there will be sufficient energy to complete an activity sequence initiated using data collected by the sensors and / or actuators and involved in the electronic devices described herein.

[0066] Figure 16 is a block diagram of an advanced second embodiment electronic device 160 in which advanced details are added to application load 25. Application load 25 includes control unit 151 and primary activity functional load 152 as previously described in Figure 15. Voltage detector 61 is connected to control unit 151 via SIG2.

[0067] Figure 17 is a block diagram of an advanced third embodiment electronic device 170 in which advanced details are added to application load 25. Application load 25 includes control unit 151 and primary activity functional load 152 as previously described in Figure 15. Voltage detector 61 is connected to control unit 151 via SIG2. Timer 101 is connected to application load 25, specifically to control unit 151 via SIG3 and SIG4.

[0068] FIG. 18a is a block diagram of an electronic device 180 of the fourth embodiment, which is the same as the electronic device 160 of the second embodiment, except that an illuminance sensor 181 is connected to the application load 25, specifically to the control unit 151 via SIG5 and SIG6. The application load 25 may provide power to the illuminance sensor 181 via SIG5 and / or SIG6. When powered by the application load 25, the illuminance sensor 181 measures the ambient lighting illuminance and relays the measured illuminance information to the control unit 151 via SIG6. Thus, the illuminance sensor 181 provides information related to the illumination level of the photovoltaic unit 21 to the control unit 151. Alternatively, although not shown, an illuminance sensor may be provided within the primary activity functional load and configured to perform the same function as the illuminance sensor 181 described above. FIG. 18a generally illustrates an illuminance sensor associated with the application load 25.

[0069] Fig. 18b is a block diagram of an electronic device 182 of an advanced fourth embodiment, which is identical to the electronic device 160 of the advanced second embodiment, except that the photovoltaic power generation unit 21 is additionally directly connected to the control unit 151 via SIG8. The photovoltaic power generation unit 21 and the control unit 151 are configured to measure ambient illuminance. The photovoltaic power generation unit 21 of Fig. 18b performs an additional function similar to the function performed by the illuminance sensor 181 shown in Fig. 18a. Thus, the photovoltaic power generation unit 21 provides information to the control unit 151 related to the illumination level of the photovoltaic power generation unit 21 itself.

[0070] With reference to Figs. 18a and 18b, the control unit 151 may be configured to self-adapt operation in the application load 25 depending on the ambient illumination level. Typically, the ambient illumination level may be measured using any illumination sensor associated with the application load. The ambient illumination level may be measured by the illumination sensor 181 shown in Fig. 18a or an illumination sensor (not shown) in the primary activity functional load 152. Alternatively, the ambient illumination level may be determined by the control unit 151 measuring the current generated by the photovoltaic device 21 via SIG8 as shown in Fig. 18b. The control unit 151 operates the application load 25 at a first predetermined ambient illumination level, e.g., the illumination level in LxR1, as in the case of the electronic device 20 of the first embodiment. The control unit 151 may be configured to operate the application load 25 at a second predetermined ambient illumination level, e.g., the illumination levels in LxR2 and LxR3, as in the case of the electronic device 60 of the second embodiment. 13, the electronic device 180 of the fourth embodiment and the electronic device 182 of the advanced fourth embodiment may be configured to operate with a circuit efficiency similar to that of the electronic device 20 of the first embodiment at low ambient illuminance values, and also operate with a circuit efficiency similar to that of the electronic device 60 of the second embodiment at intermediate and high ambient illuminance values. Thus, the electronic device 180 of the fourth embodiment and the electronic device 182 of the advanced fourth embodiment may be configured to automatically switch (i.e., self-adapt) between a circuit efficiency similar to that of the electronic device 20 of the first embodiment at low ambient illuminance values ​​and a circuit efficiency similar to that of the electronic device 60 of the second embodiment at intermediate and high ambient illuminance values, so as to obtain the highest circuit efficiency at a given ambient illumination level. In other words, the electronic device 180 of the fourth embodiment and the electronic device 182 of the advanced fourth embodiment may automatically optimize the circuit efficiency at a given measured ambient illumination level. The electronic device 180 of the fourth embodiment and the electronic device 182 of the advanced fourth embodiment may have a circuit efficiency superior to that of the electronic device 60 of the second embodiment at low ambient illuminance values. Both the fourth embodiment electronic device 180 and the advanced fourth embodiment electronic device 182 may have better circuit efficiency than the first embodiment electronic device 20 at medium and high ambient illumination values.In other words, both the electronic device 180 of the fourth embodiment and the electronic device 182 of the advanced fourth embodiment may have relatively high circuit efficiency at all ambient lighting levels. The electronic device 182 of the advanced fourth embodiment may have higher circuit efficiency than the electronic device 180 of the fourth embodiment at at least some ambient lighting levels.

[0071] FIG. 19a is a block diagram of an electronic device 190 of a fifth embodiment, which is the same as the electronic device 170 of the advanced third embodiment, except that an illuminance sensor 181 is connected to the application load 25, specifically to the control unit 151 via SIG5 and SIG6. The application load 25 may provide power to the illuminance sensor 181 via SIG5 and / or SIG6. When the illuminance sensor 181 is powered by the application load 25, it measures the ambient lighting illuminance and relays the measured illuminance information to the control unit 151 via SIG6. Thus, the illuminance sensor 181 provides information related to the illumination level of the photovoltaic unit 21. Alternatively, although not shown, an illuminance sensor may be provided within the primary activity functional load and configured to perform the same function as the illuminance sensor 181 described above. FIG. 19a generally illustrates an illuminance sensor associated with the application load 25.

[0072] FIG. 19b is a block diagram of an electronic device 192 of the advanced fifth embodiment, which is identical to the electronic device 170 of the advanced third embodiment, except that the photovoltaic power generating unit 21 is also connected to the control unit 151 via SIG8. In other words, there is typically a direct connection from the photovoltaic power generating unit 21 to the application load 25, and specifically from the photovoltaic power generating unit 21 to the control unit 151. The photovoltaic power generating unit 21 and the control unit 151 may be configured to measure ambient illuminance. The photovoltaic power generating unit 21 of FIG. 19b performs an additional function similar to the function performed by the illuminance sensor 181 shown in FIG. 19a. In other words, the photovoltaic power generating unit 21 may also be considered to operate as an illuminance sensor involved in the application load. The photovoltaic power generating unit 21 thus provides information related to its own illumination level to the control unit 151.

[0073] 19a and 19b, the controller 151 may be configured to self-adapt operation in the application load 25 depending on the ambient illumination level. The ambient illumination level may be measured by the illumination sensor 181 as shown in FIG. 19a. Alternatively, the ambient illumination level may be determined by the controller 151 by measuring the current generated by the photovoltaic device 21 as shown in FIG. 19b. The controller 151 operates the application load 25 at a first predetermined ambient illumination level, e.g., illumination level within LxR1, as in the case of the electronic device 20 of the first embodiment. The controller 151 may be configured to operate the application load 25 at a second predetermined ambient illumination level, e.g., illumination levels within LxR2 and LxR3, as in the case of the electronic device 100 of the third embodiment. 13, both the electronic device 190 of the fifth embodiment and the electronic device 192 of the advanced fifth embodiment may be configured to operate with a circuit efficiency similar to that of the electronic device 20 of the first embodiment at low ambient illuminance values, and with a circuit efficiency similar to that of the electronic device 100 of the third embodiment at intermediate and high ambient illuminance values. Thus, the electronic device 190 of the fifth embodiment and the electronic device 192 of the advanced fifth embodiment may be configured to automatically switch (i.e., self-adapt) between a circuit efficiency similar to that of the electronic device 20 of the first embodiment at low ambient illuminance values ​​and a circuit efficiency similar to that of the electronic device 60 of the second embodiment at intermediate and high ambient illuminance values, so as to obtain the highest circuit efficiency at a given measured ambient illumination level. In other words, the electronic device 190 of the fifth embodiment and the electronic device 192 of the advanced fifth embodiment may automatically optimize the circuit efficiency at a given ambient illumination level. Both the electronic device 190 of the fifth embodiment and the electronic device 192 of the advanced fifth embodiment may have better circuit efficiency at low illuminance values ​​than the electronic device 100 of the third embodiment. Both the electronic device 190 of the fifth embodiment and the electronic device 192 of the advanced fifth embodiment may have better circuit efficiency at medium and high ambient illuminance values ​​than the electronic device 20 of the first embodiment. In other words, both the electronic device 180 of the fifth embodiment and the electronic device 192 of the advanced fifth embodiment may have relatively high circuit efficiency at all ambient lighting levels.The electronics 192 of the advanced fifth embodiment may have higher circuit efficiency than the electronics 190 of the fifth embodiment, at least at some ambient lighting levels.

[0074] FIG. 20 is a block diagram of an electronic device 200 of the sixth embodiment. The electronic device 200 of the sixth embodiment is the same as the electronic device 20 of the first embodiment, except that a voltage regulator 201 is connected between the load switch 24 and the application load 25. In general, all electronic devices described in this specification that have one voltage detector may have a voltage regulator 201 connected between the load switch 24 and the application load 25. The voltage regulator 201 may be a low dropout regulator (LDO) or a DC / DC converter. The voltage regulator 201 provides a stable environment for the operation of the electronic circuit. Thus, the voltage regulator 201 may prevent undesirable events such as, for example, a sensor mismeasurement, a communication protocol value misread, and a brownout reset trigger (i.e., the voltage regulator 201 may prevent the operation of the peripheral device in the control unit 151 from being interrupted). Since the voltage regulator 201 may prevent a voltage spike, the voltage regulator 201 may prevent an activity sequence from stopping mid-cycle. The advantage of including a voltage regulator 201 in an ultra-low power electronics design is that it allows for a more robust circuit design. The disadvantages of including a voltage regulator 201 in an ultra-low power electronics design include increased cost, increased circuit size (i.e., increased ground area), and increased power consumption, especially during the start-up sequence. Increased power consumption can reduce circuit efficiency.

[0075] FIG. 21 is a block diagram of the electronic device 210 of the seventh embodiment. The electronic device 210 of the seventh embodiment is the same as the electronic device 60 of the second embodiment, except that the voltage regulator 201 is connected between the node 2 (N2) and the application load 25. In general, all electronic devices described herein that have two voltage detectors may have the voltage regulator 201 connected between the load switch 24 and the application load 25. The advantages and disadvantages of the voltage regulator 201 have already been described. Surprising results of experiments performed by the inventors suggest that in warm environmental conditions (e.g., indoor use), the operation of the electronic device of all the embodiments disclosed herein may be sufficiently robust even if the voltage regulator 201 is omitted from the circuit design. In other words, it has been found that the advantages of supplying unregulated (i.e., voltage regulator-free) power to the application load outweigh the disadvantages.

[0076] Each electronic device in the embodiments described herein is configured to optimize power delivery to the application load associated with the electronic device, so that the application load performs an optimized amount of useful work for the energy harvested by the electronic device. For application loads that have a startup sequence and an activity sequence, the following actions may contribute to optimizing power delivery: 1. The wake-up sequence is executed only if there is enough energy to complete the wake-up sequence and to complete at least one active sequence. 2. An additional activity sequence is executed only if there is enough energy to complete that activity sequence.

Claims

1. An electronic device comprising a photovoltaic power generating unit, an energy storage unit, a voltage detector, a load switch and an application load, the electronic device comprising: Collect and store energy from ambient lighting, configured to optimize power delivery to the application load from at least one of the harvested energy and the stored energy; the photovoltaic power generating unit, the energy storage unit, the voltage detector, and the input of the load switch are connected to a common point; the photovoltaic unit is configured to collect energy from the ambient lighting; an output of the load switch is coupled to the application load; the voltage detector is configured to measure a voltage at the common point; the voltage detector is further configured to turn on the load switch when a voltage measured at the common point rises to a level equal to or greater than a first voltage to provide optimized power to the application load from at least one of the energy storage unit and the photovoltaic power generation unit; the voltage detector is further configured to turn off the load switch when the voltage measured at the common point drops to a level equal to or less than a second voltage, so that the photovoltaic power generating unit stores energy in the energy storage unit; The first voltage is greater than the second voltage.

1. An electronic device comprising:

2. The application load is configured to execute at least one activity sequence after executing a start-up sequence when the load switch is turned on.

2. The electronic device according to claim 1 .

3. configured to complete the initiated sequence of activities 3. The electronic device according to claim 1 or 2.

4. The first voltage is within 20% of the voltage that the photovoltaic unit produces at its maximum power point for a given temperature.

4. The electronic device according to claim 1, wherein the first and second electrodes are electrically connected to the first and second electrodes.

5. The energy storage unit comprises at least one of a battery and a rechargeable battery.

5. The electronic device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

6. The energy storage unit comprises at least one of a capacitor and a supercapacitor.

6. The electronic device according to claim 1, wherein the first and second electrodes are electrically connected to the first and second electrodes.

7. and a voltage regulator connected between the load switch and the application load.

7. The electronic device according to claim 1, wherein the first and second electrodes are electrically connected to the first and second electrodes.

8. and at least one sensor participating in the application load and configured to collect data relating to at least one of orientation, acceleration, temperature, humidity, air pressure, light, illuminance, magnetic field, sound, infrared, ultraviolet, gas, proximity, images, and user input, or any combination thereof.

8. The electronic device according to claim 1, wherein the first and second electrodes are electrically connected to the first and second electrodes.

9. The data collected by the sensors is stored in a memory associated with the application load.

9. The electronic device according to claim 8.

10. at least one actuator engaged with the application load and configured to collect data related to at least one of a push button, a switch, a touch sensor, and a user input, or any combination thereof; 10. The electronic device according to claim 1, wherein the first and second electrodes are electrically connected to the first and second electrodes.

11. The data collected by the actuators is stored in a memory associated with the application load.

11. The electronic device according to claim 10.

12. At least one of the sensors and the actuators initiates a sequence of actions.

12. The electronic device according to claim 1, wherein the first and second electrodes are electrically connected to the first and second electrodes.

13. an illuminance sensor associated with the application load; the application load and the associated illuminance sensor are configured to measure an ambient illuminance level; The application load and the associated illuminance sensor are further configured to automatically optimize circuit efficiency in response to the measured ambient illuminance level.

13. The electronic device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

14. the photovoltaic power generating unit is directly connected to the application load; the photovoltaic power generating unit and the application load are configured to measure an ambient illumination level; The photovoltaic power generating unit and the application load are further configured to automatically optimize circuit efficiency in response to the measured ambient illumination level.

14. The electronic device according to claim 1, wherein the electronic device is a liquid crystal display.

15. The application load comprises a wireless communication component.

15. The electronic device according to claim 1, wherein the electronic device is a semiconductor device.

16. The wireless communication unit is a Bluetooth Low Energy transmitter.

16. The electronic device according to claim 15.

17. When the load switch is turned on, the application load is configured to execute a start-up sequence and then execute an activity sequence, the activity sequence including transmitting information to a network of multiple wireless receivers.

17. The electronic device according to claim 1, wherein the first and second electrodes are arranged in a first direction.

18. The information transmitted includes at least one of a beacon signal, data collected from at least one sensor involved in the application load, data collected from at least one sensor and stored in a memory involved in the application load, data collected from at least one actuator involved in the application load, data collected from at least one actuator and stored in a memory involved in the application load, and measured ambient light levels, or any combination thereof.

18. The electronic device according to claim 17.

19. The application load includes a controller connected to a primary activity functional load.

19. The electronic device according to claim 1, wherein the electronic device is a semiconductor device.

20. The control unit and the primary activity functional load are configured to exchange information.

20. The electronic device according to claim 19.

21. The control unit may include at least one of a field programmable gate array (FPGA), a microcontroller, and a logic unit, or any combination thereof.

21. The electronic device according to claim 19 or 20.

22. An additional voltage detector is provided, the additional voltage detector and the output of the load switch are connected at an additional common point; The additional voltage detector is configured to measure a voltage at the additional common point.

22. The electronic device according to claim 1, wherein the electronic device is a semiconductor device.

23. the additional voltage detector and the application load are configured to execute a sequence of actions when the voltage measured at the additional common point rises to a level equal to or greater than a third voltage; the additional voltage detector and the application load are further configured to not execute an additional sequence of actions when the voltage measured at the additional common point falls to a level equal to or less than a fourth voltage; the third voltage is greater than the second voltage; the fourth voltage is greater than the second voltage; The third voltage is greater than the fourth voltage.

23. The electronic device according to claim 22.

24. and a timer coupled to the application load.

24. The electronic device according to claim 1,

25. The timer and the application load are configured to initiate a countdown sequence on the timer during the start-up sequence.

25. The electronic device according to claim 24.

26. The timer and the application load are configured to initiate a countdown sequence on the timer during the activity sequence.

25. The electronic device according to claim 24.

27. The timer and the application load are the timer has completed its countdown sequence; said additional voltage detector measuring a voltage at said additional common point that is less than said third voltage; said voltage detector measuring a voltage at said common point that is greater than said second voltage; and executing at least one sequence of actions if all of the following conditions are met:

27. Electronic device according to claim 25 or claim 26 when dependent on claim 23.

28. 1. A method implemented by an electronic device for optimizing power delivery to an application load, the electronic device comprising: a photovoltaic power generating unit, an energy storage unit, a voltage detector, a load switch, and an application load, the application load having a start-up sequence and an activity sequence; The method comprises: Charging the energy storage unit from the photovoltaic power generation unit while the load switch is turned off; turning on the load switch when the voltage detector detects a voltage equal to or greater than a first voltage; performing the start-up sequence after turning on the load switch; executing at least one action sequence after said start-up sequence; not executing the action sequence and turning off the load switch when the voltage detector detects a voltage equal to or less than a second voltage; The first voltage is greater than the second voltage. A method comprising:

29. The electronic device includes an additional voltage detector, and the method further comprises: entering an idle mode after the start-up sequence upon i) detecting a voltage less than a third voltage with the additional voltage detector and ii) detecting a voltage greater than the second voltage with the voltage detector; exiting the idle mode and executing an active sequence when the additional voltage detector detects a voltage equal to or greater than the third voltage; executing at least one additional sequence of actions upon detecting a voltage greater than a fourth voltage with the additional voltage detector; i) detecting a voltage less than or equal to a fourth voltage with said additional voltage detector and ii) detecting a voltage greater than said second voltage with said voltage detector, thereby entering an idle mode without executing an activity sequence; exiting the idle mode and turning off the load switch when the voltage detector detects a voltage equal to or less than a second voltage; the third voltage is greater than the second voltage; the fourth voltage is greater than the second voltage; The third voltage is greater than the fourth voltage.

29. The method of claim 28.

30. The electronic device includes an additional voltage detector and a timer, and the method further comprises: initiating a countdown on the timer after executing the start-up sequence; i) detecting a voltage less than a third voltage with the additional voltage detector, ii) a countdown of the timer has not ended, and iii) if the voltage detector detects a voltage greater than the second voltage, starting a countdown of the timer and then entering an idle mode; exiting said idle mode and executing an activity sequence upon either i) detecting a voltage equal to or greater than said third voltage with said additional voltage detector or ii) expiring a countdown on said timer; restarting the countdown on the timer during the activity sequence; executing at least one additional sequence of actions upon detecting a voltage greater than a fourth voltage with the additional voltage detector; i) detecting a voltage less than or equal to the fourth voltage with the additional voltage detector, and ii) detecting a voltage greater than the second voltage with the voltage detector, thereby entering the idle mode without executing an activity sequence; exiting the idle mode and turning off the load switch when the voltage detector detects a voltage less than or equal to the second voltage; the third voltage is greater than the second voltage; the fourth voltage is greater than the second voltage; The third voltage is greater than the fourth voltage.

29. The method of claim 28.

31. An electronic device comprising a photovoltaic power generating unit, an energy storage unit, a voltage detector, a load switch and an application load, the application load having a start-up sequence and an activity sequence, the electronic device being configured to perform a method according to any of claims 28 to 30.

1. An electronic device comprising:

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