Electronic device and method for managing power

Abstract

Electronic device and method for managing power The invention relates to an electronic device comprising a power management integrated circuit (PMIC) for managing power from an energy harvester, comprising: a storage unit, an internal DC-DC converter embedded within the PMIC, optimized for a first, lower power range; and an external DC-DC converter controlled by the PMIC, optimized for a second, higher power range. Both DC-DC converters have an input and an output. According to the invention, both the outputs of the internal and external DC-DC converters are connected in parallel to the storage unit and the power paths of the external DC-DC converter are located outside of the PMIC. Further according to the invention, the PMIC is configured to automatically switch between the internal and external DC-DC converters as active converter to extract energy from the energy harvester or to allow them to run simultaneously to extract energy from the energy harvester based on the power level provided by the energy harvester.

Description

Electronic device and method for

[0001] Description

[0002] The present patent application relates to the technical field of energy harvesting. In particular, the invention relates to an electronic device and to a method for managing power.

[0003] Prior art

[0004] Energy harvesting devices, such as those utilizing solar cells, are designed to convert ambient energy into usable power for small electronic systems. However, the amount of power generated from these harvesters can fluctuate dramatically. For example, a solar cell exposed to outdoor sunlight can produce power levels more than three orders of magnitude higher than when exposed to indoor lighting. To manage this variability efficiently, power management integrated circuits (PMICs) are employed to regulate the flow and distribution of the harvested energy. PMICs play a crucial role in ensuring that the system operates effectively across a wide range of input power levels, optimizing performance and energy usage in different lighting conditions.

[0005] There are mainly two types of PMIC. In a first configuration, power transistors are directly integrated within the PMIC, meaning all components needed for power conversion and regulation are encapsulated within a single integrated circuit. This approach reduces the overall size and simplifies the design but has limitations in terms of power losses, particularly as the average current flowing through the power paths increases. Integrating the power transistors within the PMIC increases current density and can create losses due to the internal resistance of the metal tracks and the integrated MOSFETs, thus reducing overall efficiency and usable power. In addition, there are risks related to electromigration and, due to poor management of thermal dissipation, of potential meltdown of metal tracks, which necessitate limits on current density, further restricting the amount of power that can be extracted. In a second setup, the PMIC acts as a controller that drives external power transistors via gate driver circuits. This approach allows for the use of larger or specialized power transistors, which can be selected to optimize thermal dissipation and minimize resistive losses. The external transistors handle the main power, freeing the PMIC from certain thermal constraints and increasing design flexibility. Although this solution occupies more space and is generally more complex, it allows for higher efficiency levels, particularly in applications where the amount of power being transferred is higher than one Watt. In other words, the configuration with integrated transistors is compact and simple but limited in efficiency for higher power levels, whereas the one with external transistors offers better energy efficiency and thermal dissipation at the cost of increased complexity and space.

[0006] To address these challenges, specialized manufacturing technologies like the Bipolar- CMOS-DMOS (BCD) process are sometimes used. While BCD technology can alleviate some of these issues, it comes with trade-offs, such as a reduction in the number of available voltagethresholds (VTs) for other analog functions. Another approach involves increasing the width of metal tracks, using thicker wirebonds, and employing larger MOSFETs to reduce losses. However, these solutions significantly increase production costs due to the larger silicon area required. Additionally, both methods tend to shift the PMIC's optimal performance toward higher power levels, such as outdoor lighting, at the expense of efficiency in lower power environments, like indoor lighting conditions.

[0007] Documents WO-A1-2023 / 238499 and US-A1-2021 / 021193 discloses electronic devices comprising several DC-DC converters but they are not connected in parallel between the energy source and a unique storage unit as single output.

[0008] It would be advantageous to develop an electronic device featuring a power management integrated circuit (PMIC) that could overcome these issues. The aim of the present invention is to address the trade-off between power efficiency at low and high power levels.

[0009] Summary of the invention

[0010] Unlike designs that integrate all components on a single silicon chip, where MOSFETs are placed alongside the gate drivers, the present invention does not aim to reduce area or complexity. Instead, a complete PMIC is proposed that integrates both internal power switches and drivers for external power switches. By dynamically managing the transition between low- power-optimized internal MOSFETs and high-power-optimized external MOSFETs, the present solution extends the overall power range while maintaining efficiency across different power levels.

[0011] This aim is reached with an electronic device comprising a power management integrated circuit (PMIC) for managing power from an energy harvester, comprising: a storage uit, an internal DC-DC converter embedded within the PMIC, optimized for a first, lower power range. The electronic device of the invention further comprises an external DC-DC converter controlled by the PMIC, optimized for a second, higher power range. Both DC-DC converters have an input and an output. According to the invention, both the outputs of the internal and external DC-DC converters are connected in parallel to the storage unit and the power paths of the external DC-DC converter are located outside of the PMIC. Further according to the invention, the PMIC is configured to automatically switch between the internal and external DC-DC converters as active converter to extract energy from the energy harvester or to allow them to run simultaneously to extract energy from the energy harvester based on the power level provided by the energy harvester.

[0012] The PMIC is here an integrated circuit that incorporates at least one DC-DC converter to extract energy from a harvester and that preferably includes other subcircuits. Those subcircuits could include a cold-start module, useful to generate the bias signals required to start the regular operation of the rest of the PMIC when initially connected to the harvesterand when power starts to be available from the harvester. Another subcircuit is a maximum power point tracker or MPPT that determines the optimum bias voltage to be applied to the harvester so as to maximize the amount of power being produced by the harvester under given environmental conditions. Yet another subcircuit is a battery monitoring system protecting the storage device generally connected to the output of the PMIC against detrimental operating conditions such as, for instance, undervoltage, overvoltage or operation at too high or too low temperatures. Yet another subcircuit is one or several auxiliary converter(s) delivering energy to an application load such as a sensor, a microcontroller or a wireless communication means. This auxiliary converter(s) can use as its input energy source the output of the at least one DC- DC converter to extract energy from the harvester, or a storage device connected directly or indirectly to this output. Alternatively, it can use the energy harvester as input. This auxiliary converter(s) can be an inductive switching regulator, a capacitive switching regulator or a linear regulator. The auxiliary converter(s) may or may not use a reactive component to perform the power conversion, such a reactive component, when used, being internal or external to the PMIC.

[0013] The internal DC-DC converter can be any kind of DC-DC converter such as a switching converter using an inductor as reactive component and that steps up (boost) or down (buck) or up or down indifferently (buck-boost) the input voltage. Alternatively, it can be a switching converter using one or several capacitors as reactive component(s) such as for instance a switched capacitor converter or a charge pump. It can also be made of one or several power switches that enable or disable the current path between the input and the output of the DC- DC converter, those power switches optionally being controlled so as to limit the current flow from the input to the output of the internal DC-DC converter to configured values set by the internal DC-DC converter controller. The DC-DC converter controller is usually integrated into the PMIC. However, in some embodiments, it is also possible to have the DC-DC controller outside of the PMIC, for instance as part as a microcontroller or a dedicated FGPA (Field- Programmable Gate Array) or ASIC (Application-Specific Integrated Circuit) interacting with the PMIC.

[0014] The external DC-DC converter is typically a switching converter using an inductor, a transformer or one or several capacitor(s) as reactive component(s) and that steps up (boost) or down (buck) or up or down indifferently (buck-boost) the input voltage.

[0015] The harvester can for instance be a solar cell made of one or multiple cells connected in parallel, in series, or in a combination of series and parallel connections. It can also be a thermoelectric generator, a piezoelectric generator or a combination of an antenna and a rectifier harvesting energy sent by radio-frequency waves.

[0016] In another embodiment, the internal DC-DC converter uses passive component(s) as the reactive component(s) to perform the power extraction from the harvester. Such reactivecomponent(s) can be integrated into the PMIC or be implemented by passive component(s) placed outside of the PMIC.

[0017] While using integrated components allows for reducing the area required on the application for the use of the PMIC, and to reduce the associated bill-of-materials, external components typically results in a higher power conversion efficiency of the DC-DC converter.

[0018] Preferably, the controller of the external DC-DC converter is located inside of the PMIC. This allows reducing the implementing costs and facilitating the control of the combination of the two DC-DC converters.

[0019] Advantageously, the external DC-DC converter includes gate drivers, wherein the gate drivers of the external DC-DC converter are included into the PMIC. This also allows reducing the implementing costs.

[0020] In another embodiment, the DC-DC converters contains a sensor configured for monitoring predetermined parameters of said DC-DC converter or from both internal and external DC-DC converters and wherein the PMIC is configured for switching from one DC-DC converter to the other to extract energy from the energy harvester based on monitoring of the predetermined DC-DC converter parameters or wherein the PMIC is configured for switching from one DC-DC converter to both DC-DC converters or from both DC-DC converters to one DC- DC converter to extract energy from the energy harvester based on monitoring of the predetermined DC-DC converter parameters.

[0021] In one embodiment, the sensor comprises a comparator configured to measure the deviation between the voltage across the harvester and a reference voltage. Activation of the high-power converter is triggered when the harvester voltage exceeds the reference voltage by a predefined threshold, for example 50 mV or 100 mV. In another embodiment, the control may rely on the power monitoring system described in the Luxembourg patent application n° 509734 or in the International application claiming the priority thereof, which is configured to select the internal and / or external converters based on the power transfer value measured by said power monitoring device.

[0022] This allows the electronic device to autonomously decide when to switch from one DC- DC to another or from one DC-DC converter to both DC-DC converters or from both internal and external DC-DC converters depending on the parameters being monitored. The parameters can typically be the input voltage (in particular the deviation of the input voltage from the setpoint) or the average current transferred by the active DC-DC converter(s), or the average power transferred by the active DC-DC converter(s), or the energy transferred by the active DC- DC converter(s) during a given time interval.

[0023] In this case, preferably, the internal DC-DC converter contains a sensor for monitoring predetermined parameters of the internal DC-DC converter or from both internal and external DC-DC converters and the PMIC is configured for switching from one DC-DC converter to theother to extract energy from the energy harvester based on monitoring of the DC-DC predetermined parameters or for switching from one DC-DC converter to both DC-DC converters or from both DC-DC converters to one DC-DC converter to extract energy from the energy harvester based on monitoring of the DC-DC predetermined parameters.

[0024] Thereby, the fully integrated DC-DC converter parameters are easier to monitor as this does not require additional terminals to the outside of the electronic device. The sensor can be made of a current sensor. In this case, the observability of the current can be achieved with a replica of the power transistors of the internal and or external DC-DC converters and by measuring the voltage drop across those replicas or by comparing this voltage drop to voltage references corresponding to current thresholds being reached. A current sensor allows for measuring the average current transferred by the DC-DC converter. It also allows for measuring the average power transferred or the energy transferred during a given time interval by the DC- DC converter when combined with the knowledge or a measure of the voltage at the input or at the output of the active DC-DC converter(s). Alternatively, the sensor can be a voltage sensor made for example of an analog to digital converter or ADC. An ADC can be used to monitor the input or the output voltage of the active DC-DC converter(s). Such a sensor can be used to estimate the input voltage and its deviation from its setpoint, the average power transferred, or the energy transferred during a given time interval by the active DC-DC converter(s) when combined with the knowledge or the measure of the average current transferred by the active DC-DC converter(s). Yet an alternative sensor can be a voltage comparator using as inputs both the input voltage of the DC-DC converters, and a voltage reference corresponding to the setpoint of the DC-DC converter and that is eventually offset. Such a sensor can monitor the deviation of the input voltage from its setpoint.

[0025] In a different embodiment, one or two a register(s) of the PMIC is (are) configured for switching from one DC-DC converter to the other to extract energy from the energy harvester or for switching from one DC-DC converter to both DC-DC converters or from both DC-DC converters to one DC-DC converter to extract energy from the energy harvester.

[0026] Thanks to these registers, the decision to switch from one converter to the other or to / from the two converters operating simultaneously can be delegated to an external circuit depending on the parameters observed by this external circuit. Such an external circuit could be a microcontroller. This microcontroller could base its control mechanism of the register(s) upon observation of the DC-DC converter activity, upon monitoring of parameters being an image of the activity of the DC-DC converter such as the input voltage (in particular the deviation of the input voltage from the setpoint) or the average current transferred by the active DC-DC converter(s), or the average power transferred by the active DC-DC converter(s), or the energy transferred by the active DC-DC converter(s) during a given time interval. It could also base its control mechanism of these register(s) upon the monitoring of parameters thatare an image of the amount of power being delivered by the harvester such as the illumination when the harvester is a PV cell or the temperature when the harvester is a thermoelectric generator, or the measure of acceleration when the harvester is a piezoelectric or a vibration harvester. The microcontroller could also base its control mechanism of these register(s) upon the predictable knowledge of the evolution of the harvester environment, for instance, because the harvester is supplied by a controlled source or by a predictive source and that because the microcontroller triggers an energy transfer from the controlled source to the harvester or knows that such a transfer will be triggered. Examples of controlled sources are RF emitters delivering a beamformed wave or a light emitter delivering a beamformed signal. An example of a predictive source is a vibration occurring repetitively every given period of time in a machine. Knowledge of the transfer by the microcontroller can be achieved because the microcontroller receives a signal providing information that such an energy transfer will occur or because of the repetitive aspect of such a transfer.

[0027] The use of a register can be combined with the monitoring of a parameter of the active DC-DC converter. For instance, when the monitoring of such a parameter triggers the activation of the external DC-DC converter, this external DC-DC converter can be deactivated through the modification of the register controlling its activation. In this case this deactivation can be performed by an external microcontroller or after a determined time interval. In another example, the monitoring of such a parameter triggers the activation of the internal DC-DC converter which is deactivated through the modification of the register controlling its activation. Again, in this case this deactivation can be performed by an external microcontroller or after a determined time interval.

[0028] Preferably, the register(s) of the PMIC is / are configured via a communication interface.

[0029] Indeed, the use of a communication interface avoids the need to use a GPIO / terminal specifically dedicated to this function. Examples of communication interfaces are I2C, UART, USART or SPI.

[0030] Alternatively, the register(s) of the PMIC is / are configured via a reading of a terminal of the PMIC.

[0031] The use of a terminal or a GPIO is simple and does not require the need to have a communication interface and the implementation of a communication protocol between the two communicating parties.

[0032] In another variant of the invention, the PMIC is configured to switch from one DC-DC converter to the other to extract energy from the energy harvester or from one DC-DC converter to both DC-DC converters or from both DC-DC converters to one DC-DC converter to extract energy from the energy harvester based on monitoring of other parameters such as system illumination or time lapse.

[0033] This embodiment provides more ways to control which DC-DC converter should be activated. For example, the luminosity information could already be available elsewhere on the system (e.g. if there is a camera). Generally, the data is provided by the system, typically through a communication interface such as l2C or SPI. This information originates from a luxmeter, which supplies the data either directly to the PMIC or to a microcontroller that subsequently transfers it to the PMIC. Since the energy available on a photovoltaic cell depends on the luminosity, the control strategy could be established based on this information. In the same way, the monitoring of the time between two energy transfers by the active DC-DC converter(s), optionally taking into account the size of the energy buffer that could be connected to the harvester output and / or a maximum allowed deviation of the input voltage below its setpoint is also an image of the power that is available on the harvester. Here the maximum allowed deviation has to be construed as a known voltage deviation configured by the controller of the PMIC.

[0034] The monitoring of the time required by the active DC-DC converter to lower the input voltage from its setpoint down to the maximum allowed deviation below its setpoint is yet another way to get an image of the power provided by the harvester, preferably when combined with the knowledge of the amount of power that is being transferred by each of the DC-DC converters when they are active. In that case, the controller includes a timer configured to measure either the duration during which the converter transfers energy continuously, or the inactivity period between two consecutive energy transfer phases.

[0035] In an embodiment of the invention, the integrated circuit is configured to be connected to only one energy harvester wherein said energy harvester is connected to an input of each DC-DC converter.

[0036] By connecting both DC / DC to the same harvester, it is possible to select the DC-DC converter that will extract the energy with the best efficiency depending on the power available at the input.

[0037] In an embodiment of the invention, the electronic device is configured to be connected to two different energy harvesters and each the input of each DC-DC converter is connected to a different energy harvester.

[0038] If the application benefits from having two different energy sources and delivering a different level of power, two functions are grouped together within the same electronic device, which saves silicon surface and therefore reduces the cost of implementation.

[0039] In a preferred variant of this embodiment, the internal DC-DC converter is configured to be connected to a photovoltaic cell optimized for indoor light harvesting and wherein the external DC-DC converter is configured to be connected to photovoltaic cell optimized for outdoor light harvesting.

[0040] Indoor cells deliver less energy while outdoor cells deliver more energy. This solution allows both cells to be managed efficiently.

[0041] In another variant of the same embodiment, the internal DC-DC converter is configured to be connected to a radio frequency harvester dedicated to omnidirectional harvesting and the external DC-DC converter is configured to be connected to a radio frequency harvester dedicated to beamformed radio frequency harvesting.

[0042] Omnidirectional transmitters provide energy that is dispersed in all directions. The receiver can therefore only capture a small amount of energy. Beamformed emitters have much less losses in space and the amount of energy harvested is therefore much greater. This solution typically allows to start an application with the energy of an omnidirectional transmitter and then start a protocol with a beamformed transmitter that is more efficient. The present invention allows such an implementation with a single PMIC that is power efficient both while harvesting from omnidirectional and beamformed transmitters.

[0043] In another embodiment of the invention, the system includes the electronic device connected to a storage unit configured to store the harvested energy, and to a switch configured for isolating the storage unit from the external DC-DC converter when the external DC-DC converter is not active.

[0044] The advantage of using a switch for isolating the storage unit is that it is possible to minimize the leakage path between the storage element and the ground through the power paths of the external DC-DC when the external DC-DC is idle. The switch used for the isolation of the storage unit can be integrated into the PMIC or preferably be placed outside of the PMIC in order to minimize its conductance. When placed outside of the PMIC, the PMIC has a terminal to control the switch.

[0045] Another aspect of the invention concerns a method for managing power from one or more energy harvester(s) in an electronic device as above described.

[0046] This method comprising the steps of(la ) connecting an energy harvester to the input of an internal DC-DC converter embedded within the PMIC, optimized for a first, lower power range(lb) connecting the same energy harvester to the input of an external DC-DC converter controlled by the PMIC, optimized for a second, higher power range,(2a) monitoring of a parameter PHARV representative of the amount of power being provided by the energy harvester,(2b) enabling the internal DC-DC converter to extract energy from the energy harvester, when PHARV increases above a first predefined threshold, then performing the following substeps:(2b.1) enabling the external DC-DC converter(2b.2) optionally disabling the internal DC-DC converter or alter the control of the internal DC-DC converter(3) then when PHARV decreases below a second predefined threshold equal or smaller than the first predefined threshold or optionally if, instead of PHARV, another parameter PHARV? representative of the amount of power being provided by the energy harvester decreases below a third predefined threshold, then performing the following substeps:(3.1) disabling the external DC-DC converter(3.2) optionally enabling the internal DC-DC converter if it was disabled during substep (2b.2) or altering the control of the internal DC-DC converter to its initial state if it was altered during substep (2b.2)(4) resuming operation from step (2a).

[0047] In the context of the present invention, the first lower power range is to be understood as comprised between 10 nW and 1W, preferably from lpW up to 500mW. In the second higher-power range, the upper limit is determined by the combination of the passive components used and the responsiveness of the AEM modules. Therefore, the high-power range may be defined as starting from 10 mW, preferably from 50 mW, and extending up to the reliability limit imposed by the user-selected external components. The higher limit can be for example of 100 W but will generally remain under 5W.

[0048] An alternative method comprises the steps of (la ) connecting an energy harvester to the input of an internal DC-DC converter embedded within the PMIC, optimized for a first, lower power range(lb) connecting the same energy harvester to the input of an external DC-DC converter controlled by the PMIC, optimized for a second, higher power range,(2) reading periodically one or two register(s) embedded to the PMIC, then performing the following substeps:(2b.1) if the register(s) stored value corresponds to a first predefined value, then enabling the internal DC-DC converter and disabling the external DC-DC converter.(2b.2a) if the register(s) stored value corresponds to a second predefined value, then enabling the external DC-DC converter;(2b.2a) optionally, if the register(s) stored value corresponds to the second predefined value, then disabling the internal DC-DC converter; or altering the control of the internal DC-DC converter as long as the register(s) stored value corresponds to the second predefined value.

[0049] Brief description of the figures

[0050] Embodiments of the invention will now be presented with reference to the appended figures. Said embodiments and figures have no other purpose than illustrating embodiments of the invention and have no limiting function.

[0051] Fig. 1 to Fig. 6 depict different electronic devices according to the invention.

[0052] Detailed description of the invention

[0053] Fig. 1 shows an electronic device that comprises a power management integrated circuit (PMIC) (1) for managing power from an energy harvester (2), comprising: a storage unit (15), an internal DC-DC converter (3) embedded within the PMIC (1), optimized for a first, lower power range. The electronic device further includes an external DC-DC converter (4) controlled by the PMIC (1), optimized for a second, higher power range. In this figure, the controller (7) and the gate drivers (8) of the external DC-DC converter (4) are located inside the PMIC (1). Both the internal DC-DC converter (3) and external DC-DC converter (4) have an input and an output, wherein the outputs are connected in parallel to a storage unit (15) in order to store the energy extracted from the energy harvester (2). The PMIC (1) is configured to automatically switch between the internal (3) and external DC-DC converters (4) as active converter to extract energy from the energy harvester (2) or to allow them to run simultaneously to extract energy from the energy harvester (2) based on the power level provided by the energy harvester (2). Information about the power level provided by the energy harvester (2) is deduced from the output of a sensor (9) which in this figure is connected to the internal DCDC converter (3), preferably to its controller, and to the controller of the external DC-DC converter (7) in order to provide meaningful information for the choice of the active converter to extract energy from the energy harvester (2).

[0054] Fig. 2 shows another electronic device similar to the electronic device of fig. 1 and where the internal DC-DC converter (3) is constructed as a boost converter increasing the voltage provided by the energy harvester (2) to a higher voltage. The internal DC-DC converter is an inductive converter with its reactive component (6) located outside of the PMIC (1). The controller (7b) and the gate drivers (8b) of the internal DC-DC converter (3) are also shown. The external DC-DC converter (4) is also constructed as a boost converter increasing the voltage provided by the energy harvester (2) to a higher voltage. The power paths (5) of the external DC-DC converter are shown outside of the PMIC (1). The gate drivers (8) and the controller of the external converter (4) are located inside the PMIC (1). The electronic device further includes a switch (16) to isolate the external DC-DC converter (4) from a storage unit (15) and to reduce leakage on the storage unit (15) when the external DC-DC converter (4) is disabled. Therefore, in fig. 2, the switch is controlled by the controller of the external DC-DC converter (7). Always in Fig. 2, besides a sensor (9) providing meaningful information about the power provided by the energy harvester (2), the PMIC (1) also uses registers (10) to control the configuration of the internal DC-DC converter (3) and of the external DC-DC converter (4) as active converter to extract energy from the energy harvester (2). Those registers are programmed by a microcontroller (13) external to the PMIC. This programming is performed by the means of a communication interface (11).

[0055] Fig. 3 shows a similar electronic device with the difference that the registers (10) are configured through the reading of a terminal (12) of the PMIC (1). Although fig. 3 shows a direct connection between the terminal (12) and the registers (10) for the sake of clarity, the terminal is actually read by a circuitry not shown which uses this information to configure the register.

[0056] Fig. 4 shows yet another electronic device similar to fig. 2 with the difference that a first energy harvester (14a) is connected to the internal DC-DC converter (3) and that a second energy harvester (14b) being able to deliver a higher amount of power is connected to the external DC-DC converter (4). In fig. 4, the PMIC (1) includes an auxiliary DC-DC converter (17) that is connected to the power rail formed by the output of the internal DC-DC converter (3), the output of the isolating switch (16) and the storage unit (15). This auxiliary converter supplies the application load (18) consisting in Fig. 4 of the microcontroller (13) controlling the registers (10) through the communication interface (11). In Fig. 4 the configuration of the internal DC-DC converter (3) and of the external DC-DC converter (4) as the active converter(s) to extract energy from the energy harvesters (14a) and (14b) is solely made by the microcontroller (13) through the registers (10) because the microcontroller has the knowledge of the power being provided by the harvesters (14a) and (14b). For instance, the first energy harvester (14a) could be a solar cell, and the second energy harvester could be an antenna gathering energy from a beamformed emitter upon the request of the microcontroller (13). In this example, the microcontroller knows when the external DC-DC converter (4) will receive power from the second energy harvester (14b) and enable the external DC-DC converter (4) as well as the isolation switch (16) accordingly. It allows saving energy by avoiding the leakage from the storage unit through the power path of the external DC-DC converter (5) and by avoiding the power consumption of the controller of the external DC-DC converter (7). Always in this example, the internal DC-DC converter (3) remains active all the time.

[0057] Fig. 5 shows another electronic device where the internal DC-DC converter (3) is constructed as a boost converter, increasing the voltage provided by the energy harvester (2) to a higher voltage. The internal DC-DC converter is an inductive converter with its reactive component (6) located outside of the PMIC (1). The controller (7b) and the gate drivers (8b) of the internal DC-DC converter (3) are also shown. The external DC-DC converter (4) is also constructed as a boost converter increasing the voltage provided by the energy harvester (2) to a higher voltage. The power paths of the external DC-DC converter (5) are shown outside of the PMIC (1). The gate drivers (8) and the controller of the external converter (4) are located inside the PMIC (1). The storage unit (15) is connected to the output of the internal DC-DC converter (3) and to the output of the external DC-DC converter (4). In Fig. 5, the PMIC (1) includes a maximum power point tracker (19), here also connected to the harvester (2). The purpose of the maximum power point tracker (19) is to evaluate the setpoint at which the voltage of theharvester must be regulated by the internal DC-DC converter (3) and / or by the external DC-DC converter (4) in order to maximize the amount of power being provided by the energy harvester (2) for a given environmental condition. This setpoint is provided to the controllers (7) and (7b) of the internal DC-DC converter (3) and of the external DC-DC converter (4). The information of the power provided by the energy harvester (2) is obtained through a sensor (9) consisting of a voltage comparator whose inputs are the voltage provided by the energy harvester (2) and the setpoint evaluated by the maximum power point tracker (19) offset by a voltage. This information is used by the PMIC (1) to choose between the internal DC-DC converter (3), the external DC-DC converter (4) or both as the active converter(s) to extract energy from the energy harvester (2).

[0058] List of drawing references1 PMIC2 energy harvester3 internal DC-DC converter4 external DC-DC converter5 power path of the external DC-DC converter6 reactive component of the internal DC-DC converter7 controller of the external DC-DC converter7b controller of the internal DCDC converter8 gate drivers of the external DC-DC converter8b gate drivers of the internal DCDC converter9 sensor10 registers11 communication interface12 terminal of the PMIC13 microcontroller14(a) first energy harvester 14(b) second energy harvester15 storage unit16 switch for isolation of the storage unit from the external converter17 auxiliary converter18 application load19 maximum power point tracker

Claims

Claims1. An electronic device comprising- a storage unit;- a power management integrated circuit (PMIC) for managing power from an energy harvester and storing it into the storage unit, said PMIC comprising:- an internal DC-DC converter embedded within the PMIC, optimized for a first, lower, power range; and- an external DC-DC converter controlled by the PMIC, optimized for a second, higher, power range, the electronic device further comprising- a controller for the internal DC-DC converter, having an input and an output, and- a controller for the external DC-DC converter, having an input and an output, characterized in that the power paths of the external DC-DC converter are located outside of the PMIC; in that both the outputs of the internal and external DC-DC converters are connected in parallel to the storage unit, and in that the PMIC is configured to automatically switch between the internal and external DC-DC converters as active converter to extract energy from the energy harvester or to allow them to run simultaneously to extract energy from the energy harvester based on the power level provided by the energy harvester.

2. An electronic device according to claim 1, wherein the internal DC-DC converter uses one or several reactive component(s) to manage power from the energy harvester, and wherein the one or several reactive component(s) are located outside of the PMIC or are embedded within the PMIC.

3. An electronic device according to claim 1 or 2, wherein the controller of the external DC- DC converter is located inside of the PMIC.

4. An electronic device according to any one of the claims 1 to 3, wherein the external DC- DC converter includes gate drivers, wherein the gate drivers of the external DC-DC converter are included into the PMIC.

5. An electronic device according to any one of the claims 1 to 4, wherein one of the DC-DC converters contains a sensor configured for monitoring predetermined parameters of said DC-DC converter or from both internal and external DC-DC converters and wherein the PMIC is configured for switching from one DC-DC converter to the other to extract energy from the energy harvester based on monitoring of the predetermined DC-DC parameters or wherein the PMIC is configured for switching from one DC-DC converterto both DC-DC converters or from both DC-DC converters to one DC-DC converter to extract energy from the energy harvester based on monitoring of the predetermined DC- DC parameters.

6. An electronic device according to claim 5, wherein the internal DC-DC converter contains a sensor for monitoring predetermined parameters of the internal DC-DC converter or from both internal and external DC-DC converters and wherein the PMIC is configured for switching from one DC-DC converter to the other to extract energy from the energy harvester based on monitoring of the DC-DC predetermined parameters or for switching from one DC-DC converter to both DC-DC converters or from both DC-DC converters to one DC-DC converter to extract energy from the energy harvester based on monitoring of the DC-DC predetermined parameters.

7. An electronic device according to any one of the preceding claims, wherein one or two register(s) of the PM IC are configured for switching from one DC-DC converter to the other to extract energy from the energy harvester or for switching from one DC-DC converter to both DC-DC converters or from both DC-DC converters to one DC-DC converter to extract energy from the energy harvester.

8. An electronic device according to claim 7 , wherein the register(s) of the PMIC are configured via a communication protocol.

9. An electronic device according to claim 7 , wherein the register(s) of the PMIC are configured via a reading of a terminal of the PMIC.

10. An electronic device according to any one of the preceding claims, wherein the PMIC is configured to switch from one DC-DC converter to the other to extract energy from the energy harvester or from one DC-DC converter to both DC-DC converters or from both DC-DC converters to one DC-DC converter to extract energy from the energy harvester based on monitoring of other parameters such as system illumination or time lapse.

11. An electronic device according to any one of the claims 1 to 10, wherein the integrated circuit is configured to be connected to only one energy harvester wherein said energy harvester is connected to an input of each of the DC-DC converter.

12. An electronic device according to any one of the claims 1 to 10, wherein the integrated circuit is configured to be connected to two different energy harvesters and wherein each input of each DC-DC converter is connected to a different energy harvester.1513. An electronic device according to claim 12, wherein the internal DC-DC converter is configured to be connected to a photovoltaic cell optimized for indoor light harvesting and wherein the external DC-DC converter is configured to be connected to photovoltaic cell optimized for outdoor light harvesting.

14. An electronic device according to claim 12, wherein the internal DC-DC converter is configured to be connected to a radio frequency harvester dedicated to omnidirectional harvesting and wherein the external DC-DC converter is configured to be connected to a radio frequency harvester dedicated to beamformed radio frequency harvesting.

15. An electronic device according to any one of the claims 1 to 14, further comprising- a storage unit configured to store the harvested energy and- a switch configured for isolating the storage unit from the external DC-DC converter when the external DC-DC converter is not active.

16. A method for managing power from one or more energy harvester in an electronic device according to any one of the claims 1 to 15, comprising the steps of(la ) connecting an energy harvester to the input of an internal DC-DC converter embedded within the PMIC, optimized for a first, lower power range(lb) connecting the same energy harvester to the input of an external DC-DC converter controlled by the PMIC, optimized for a second, higher power range,(2a) monitoring of a parameter PHARV representative of the amount of power being provided by the energy harvester,(2b) enabling the internal DC-DC converter to extract energy from the energy harvester, when PHARV increases above a first predefined threshold, then performing the following substeps:(2b.1) enabling the external DC-DC converter(2b.2) optionally disabling the internal DC-DC converter or alter the control of the internal DC-DC converter(3) then, when PHARV decreases below a second predefined threshold equal or smaller than the first predefined threshold or optionally if, instead of PHARV, another parameter PHARVZ representative of the amount of power being provided by the energy harvester decreases below a third predefined threshold, then performing the following substeps:(3.1) disabling the external DC-DC converter(3.2) optionally enabling the internal DC-DC converter if it was disabled during substep (2b.2), or altering the control of the internal DC-DC converter to its initial state if it was altered during substep (2b.2)(4) resuming operation from step (2a).

17. A method for managing power from one or more energy harvester in an electronic device according to any one of the claims 1 to 15, comprising the steps of (la) connecting an energy harvester to the input of an internal DC-DC converter embedded within the PMIC, optimized for a first, lower power range; (lb) connecting the same energy harvester to the input of an external DC-DC converter controlled by the PMIC, optimized for a second, higher power range,;(2) reading periodically one or two register(s) embedded to the PMIC, then performing the following substeps:(2b.1) if the register(s) stored value corresponds to a first predefined value, then enabling the internal DC-DC converter and disabling the external DC-DC converter;(2b.2) if the register(s) stored value corresponds to a second predefined value, then enabling the external DC-DC converter;(2b.2a) optionally, if the register(s) stored value corresponds to the second predefined value, then disabling the internal DC-DC converter or alter the control of the internal DC-DC converter as long as the register(s) stored value corresponds to the second predefined value.

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