Method and apparatus for energy harvesting using a cold-start voltage converter

Abstract

The present invention relates to a method for energy harvesting, which uses an auxiliary energy storage device as a voltage source for a controller of a main voltage converter system. The auxiliary energy storage device is first charged by a cold-start voltage converter, after which the main voltage converter system charges a first rechargeable energy storage device until an upper charge threshold level is reached. The voltage of the auxiliary energy storage device is monitored and kept equal to a target value suitable for operating the controller, or alternatively, kept within a predetermined voltage range corresponding to a supply voltage range for operating the controller of the main voltage converter system. The present invention also relates to a power management integrated circuit for energy harvesting including a cold-start and main voltage converter system, in which an internal voltage node is kept equal to the target value or within a voltage range suitable as a supply voltage for the controller of the main voltage converter system.

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for energy harvesting, and more particularly to a method and apparatus for initiating charging of a rechargeable storage device using a power management integrated circuit (PMIC) that includes a cold-start voltage converter and a mains voltage converter system. [Background technology]

[0002] The use of voltage converters to extract energy from an energy harvester and charge a rechargeable energy storage device is well known in the art. The energy stored in the rechargeable storage device can then be used as a power source for, for example, an application load. The application load powered by the harvested energy can be any kind of application, for example, a portable device, a sensor, an external circuit, a wireless transmitter, etc.

[0003] Various energy harvesters can be used as the energy source, such as photovoltaic cells (PV), thermoelectric generators (TEG), piezoelectric energy generators, and electromagnetic energy sources. The rechargeable storage device is a rechargeable battery, such as a lithium-ion battery, a supercapacitor, or a conventional capacitor.

[0004] Typically, an integrated circuit for energy harvesting includes a main voltage converter system, including one or more voltage converters, such as a step-up, step-down or step-up step-down DC-DC voltage converter. The operation of the main voltage converter system is controlled by a controller. The controller requires a constant supply voltage, for example a supply voltage of 2.5V, 3.3V or 5V.

[0005] However, PMICs for energy harvesting do not have an internal power supply to power the controller. In prior art PMICs, the controller receives power from a rechargeable energy storage device that is connected to the output terminals of the PMIC. In some known embodiments, the PMIC includes a step-down converter, for example to convert the voltage of the rechargeable energy storage device to the supply voltage required by the controller. In other embodiments, the controller is connected to the same voltage as the storage device through a switch.

[0006] Since the rechargeable energy storage device is initially uncharged, the PMIC includes, in addition to the main voltage converter system, a cold-start voltage converter to start harvesting energy from the energy harvester without using the main voltage converter system. However, the cold-start voltage converter, which includes, for example, a charge pump, has a low efficiency compared to the efficiency of the main voltage converter system regulated by the controller. Generally, the cold-start voltage converter is used until the rechargeable energy storage device is sufficiently charged to provide the supply voltage required to start the operation of the main voltage converter system. These cold-start voltage converters are self-starting voltage converters configured to start operation when the input voltage at the input of the cold-start voltage converter is higher than a minimum threshold. A PMIC provided by e-peas SA of Belgium, known under the reference AEM10940, includes a cold-start voltage converter that starts operation, for example, at an input voltage Vin as low as 380 mV and at an input power of at least 11 microwatts.

[0007] One problem with energy harvesting systems is that when first starting with an empty rechargeable storage device, it takes a long time to charge the rechargeable storage device with a cold start voltage converter. As a result, it also takes a long time before the application load can receive power from the rechargeable storage device and start operating. Especially if the rechargeable storage device is a supercapacitor, the charging time of the supercapacitor can be very long since it is at zero volts when fully discharged. But it can also take a significant amount of time to charge a rechargeable battery to the required charge level in order to be ready to power the application load for a long enough period of time.

[0008] A further problem with the PMIC is that after charging the rechargeable energy storage device, the application load can only receive power from the rechargeable energy storage device as long as its voltage remains above a threshold voltage corresponding to the supply voltage required by the controller. For example, the rechargeable storage device can first be charged up to 4.5V, but if this voltage subsequently decreases below a supply voltage of, for example, 2.5V, the PMIC will stop working. This occurs even if the external load only requires a supply voltage of, for example, 1.2V. When using a capacitor or supercapacitor as a storage device, not all of the energy stored in the storage device can be used to supply the load, and an oversized storage device is required to achieve the target energy self-sufficiency of the application, and no energy harvesting occurs during the target energy self-sufficiency period.

[0009] Therefore, there is room for improvement in integrated circuits for energy harvesting. Summary of the Invention

[0010] It is an object of the present invention to provide a method and apparatus for harvesting energy and initiating charging of a rechargeable energy storage device in an efficient manner so that, for example, an application load coupled to the rechargeable energy storage device can begin operation more quickly even if the rechargeable storage device is initially completely empty.

[0011] The invention is defined in the accompanying independent claims. The dependent claims define advantageous embodiments.

[0012] According to a first aspect of the present invention, there is provided a method for harvesting energy using a power management integrated circuit PMIC, comprising a cold-start voltage converter, a main voltage converter system and a controller for controlling the main voltage converter system. The controller receives a supply voltage V at a supply input of the controller. sup However, the minimum supply voltage V cs A main voltage converter system is to be interpreted as a system comprising at least one main voltage converter, for example a step-down / step-up voltage converter.

[0013] The method according to the first aspect of the invention comprises the steps of: coupling an energy harvester to an input of a main voltage converter system; coupling a first rechargeable energy storage device to an output of a main voltage converter system; coupling an energy harvester or another energy source to an input of a cold-start voltage converter; coupling an auxiliary rechargeable energy storage device, preferably a capacitor, to the output of the cold-start voltage converter; coupling an auxiliary rechargeable energy storage device to a supply input of the controller so that when charged, the auxiliary rechargeable energy storage device is used as a dedicated voltage source for the controller; Auxiliary voltage V of the auxiliary rechargeable energy storage device c and monitoring a first storage parameter V indicative of a charge level of the first rechargeable energy storage device. Batt1 monitoring the Auxiliary voltage V c is the default switching voltage V swcharging the auxiliary rechargeable energy storage device by operating the cold-start voltage converter until V sw ≧V cs and Auxiliary voltage V c is the default switching voltage V sw if so, enabling operation of the main voltage converter system and disabling operation of the cold-start voltage converter; A first storage parameter V of the first rechargeable energy storage device Batt1 is the default upper limit storage value V Batt1-up operating a main voltage converter system to charge a first rechargeable energy storage device with energy from an energy harvester as long as the voltage converter system is lower than the voltage converter system voltage, and maintaining the auxiliary rechargeable energy storage device (C1) electrically isolated from the first rechargeable energy storage device (BATT1) during the charging of the first rechargeable energy storage device (BATT1); Auxiliary voltage V of the auxiliary rechargeable energy storage device c of a) equal to the target value, or alternatively b) Lower threshold voltage (V sup-min ) and the lower threshold voltage (V sup-min ) higher than the upper threshold voltage (V sup-max ) within a voltage range between The target value and the lower limit threshold voltage (V sup-min ) is the predetermined switching voltage (V sw ) or less than the minimum required supply voltage (V cs ) and maintaining the auxiliary voltage equal to the target value or within a certain voltage range includes operating a main voltage converter system or, alternatively, operating a cold-start voltage converter to recharge the auxiliary energy storage device (C1) with energy from the energy harvester (70).

[0014] In an embodiment, the auxiliary voltage V of the auxiliary rechargeable energy storage device C1 cThe step of maintaining the auxiliary voltage V equal to the target value c The method includes continuing to supplement the reduction in charge of the auxiliary energy storage device with energy from the energy harvester so as to maintain I_t equal to the target value.

[0015] In an embodiment, the target value is the minimum required supply voltage V cs Higher, default switching voltage V sw The following is the result.

[0016] In a further embodiment, the auxiliary voltage V of the auxiliary rechargeable energy storage device C1 c The lower threshold voltage V sup-min and the upper threshold voltage, the step of maintaining the auxiliary voltage V c is the lower threshold voltage V sup-min If the auxiliary voltage V drops below c is the lower threshold voltage V sup-min Higher upper threshold voltage V sup-max In an embodiment, the step of recharging the auxiliary rechargeable energy storage device with energy from the energy harvester until a lower threshold voltage V sup-min is the minimum required supply voltage V cs Higher, default switching voltage V sw The following is the result.

[0017] Advantageously, by using the auxiliary energy storage device as a dedicated voltage source for the controller, and by maintaining the auxiliary rechargeable energy storage device electrically isolated from the first rechargeable energy storage device, the voltage of the first rechargeable energy storage device, which is charged by the main voltage converter system, remains independent of the supply voltage for the controller. Thus, for example, after charging, the voltage of the first rechargeable energy storage device may be reduced to the required minimum supply voltage V cs Even if it drops lower, the main voltage converter system can continue to operate thanks to a dedicated auxiliary energy storage device.

[0018] Advantageously, by using the auxiliary energy storage device as a dedicated supply voltage for the controller, the charge capacity of the auxiliary energy storage device can be much smaller than the charge capacity of the first rechargeable energy storage device charged by the main voltage converter system. In this way, the time required to charge the auxiliary energy storage device with the cold start voltage converter and reach the supply voltage required to operate the controller is greatly reduced.

[0019] Advantageously, the first rechargeable energy storage device, i.e. the main storage device, is first charged by the main converter system and not by the cold-start voltage converter, which leads to a first start-up thanks to the higher energy efficiency of the main voltage converter system.

[0020] In some embodiments, the auxiliary rechargeable energy storage device is part of the PMIC, such as an integrated on-chip capacitor. In other embodiments, the auxiliary rechargeable energy storage device is external to the PMIC, such as an external capacitor or another rechargeable energy storage device.

[0021] Generally speaking, the switching threshold V sw V cs <V sw ≦V sup-max , more preferably V sup-min ≦V sw ≦V sup-max It is defined to be:

[0022] In the embodiment, the upper limit storage value V Batt1-up corresponds to a first rechargeable energy storage device that is charged when reached.

[0023] In the embodiment, the upper limit storage value V Batt1-up When the upper storage limit V is reached, the rechargeable energy storage device can be used to provide power to the application load. Batt1-upcorresponds to the first rechargeable energy storage device being charged to a percentage of a fully charged state of the first rechargeable energy storage device, the percentage being a value in the range of 70% to 100%.

[0024] According to a second aspect of the present invention, there is provided a power management integrated circuit (PMIC) for energy harvesting, comprising one or more power input terminals for receiving input power from an energy harvester or another power source, a first power output terminal connectable to a first rechargeable energy storage device, an auxiliary terminal connectable to an auxiliary rechargeable energy storage device or an integrated on-chip capacitor, a main voltage converter system for receiving the input power through the first power input terminal of the one or more power input terminals, and a controller configured to control the main voltage converter system, the controller controlling a supply voltage V at a supply input of the controller. sup is the minimum required supply voltage V cs and a cold-start voltage converter operable when the voltage is greater than or equal to the threshold voltage.

[0025] The cold-start voltage converter i) transmits input power to the auxiliary terminal or to an integrated on-chip capacitor, ii) receives input power through a first power input of one or more power input terminals or through a second power input terminal, and iii) determines if a minimum input voltage is available at an input of the cold-start voltage converter and if a supply voltage V sup is the minimum required supply voltage V cs If it is lower, it is configured to initiate operation.

[0026] Generally, a PMIC according to the present invention includes a first power transmission path for transmitting power from a main voltage converter system to a first storage device terminal, and / or a second power transmission path for transmitting power from the main voltage converter system to an auxiliary terminal or to an integrated on-chip capacitor.

[0027] The PMIC according to the present invention provides an auxiliary voltage Vaux corresponds to the voltage at the auxiliary terminal, or the integrated on-chip capacitor C int The auxiliary terminal 9 or the integrated on-chip capacitor C int At the internal node electrically connected to the internal node N aux is the supply voltage at the input of the controller relative to the auxiliary voltage V aux The internal node N aux is the auxiliary voltage V aux is electrically isolated from the first reservoir terminal such that is independent of the voltage at the first reservoir terminal.

[0028] The PMIC is coupled to the controller and supplies the auxiliary voltage V aux and monitoring a first storage parameter V at the first storage device terminal. Batt1 and preferably a monitoring unit configured to monitor the first storage parameter V Batt1 corresponds to a voltage sensed at the first storage device terminal. In an embodiment, the monitoring unit includes a signal comparator for comparing the auxiliary voltage with a predefined supply threshold voltage and for comparing the first storage parameter with a predefined retention threshold voltage.

[0029] The controller of the PMIC according to the present invention is configured to operate the main voltage converter system to transmit power to the first storage device terminal via the first power transmission path as long as the first storage parameter is lower than a predetermined upper storage limit value.

[0030] In an embodiment, the controller transmits power via a second power transmission path to an auxiliary terminal or to an integrated on-chip capacitor, thereby generating an auxiliary voltage V aux equal to the target value, or alternatively the auxiliary voltage V aux The lower threshold voltage V sup-min and the upper threshold voltage V sup-max and further configured to operate the main voltage converter system to maintain the voltage within a voltage range defined between a lower threshold voltage V sup-minis the minimum required supply voltage V cs In another embodiment, the controller is configured to set the auxiliary voltage V aux and configured to enable operation of a cold-start voltage converter to transfer power to an auxiliary terminal or to the integrated on-chip capacitor so as to maintain a voltage equal to or within a target value.

[0031] In an embodiment, the controller of the PMIC according to the present invention controls the auxiliary voltage V aux However, the minimum supply voltage V cs Lower to the default switching voltage V sw However, if V sw ≧V cs and is further configured to disable operation of the cold-start voltage converter system and enable operation of the main voltage converter system.

[0032] In an embodiment, the auxiliary voltage is a lower threshold voltage V sup-min If the auxiliary voltage drops below the upper threshold voltage V sup-max Alternatively, the controller operates the main voltage converter system to transfer power to the auxiliary terminal or to the integrated on-chip capacitor until the auxiliary voltage V aux The lower threshold voltage V sup-min 3. Activate the main voltage converter system to continue to maintain Vout equal to Vout.

[0033] In an embodiment, the main voltage converter system of the PMIC includes an input selection circuit controlled by the controller. The input selection is configured to select an input path from the multiple input paths such that the main voltage converter system receives input power via the selected input path. The multiple input paths for the main controller include at least a first input path configured to electrically connect a first input terminal with an input of the main voltage converter system.

[0034] In an embodiment, the multiple input paths for the main voltage converter system include at least a first input path for receiving input power through a first input terminal and a second input path configured to receive input power through a further input terminal of the PMIC, hi a further embodiment, the second input path is an internal path of the PMIC for transmitting power from the first output terminal to an input of the main voltage converter system.

[0035] In those embodiments including a first and second input path, the controller performs the following further steps: i) if the auxiliary voltage drops from a value higher than the lower threshold voltage to a predefined critical threshold voltage, provided that V cs <V T-B <V sup-min and V cs , V T-B and V sup-min are respectively a required minimum supply voltage, a critical threshold voltage and a lower threshold voltage, or alternatively, ii) if the auxiliary voltage drops below the lower threshold voltage and the monitoring unit detects that there is no input power available at the first input terminal, the monitoring unit is further configured to control the main voltage converter system and the input selection circuit to perform the steps of selecting the second input path, selecting the second power transmission path and operating the main voltage converter system until the auxiliary voltage increases to the upper threshold voltage.

[0036] In an embodiment, the main voltage converter system includes a first voltage converter and a second voltage converter. The first voltage converter has an output coupled to the first storage device terminal through a first power transmission path and an input connected to the first power input terminal. The second voltage converter has an output coupled to the integrated on-chip capacitor or to the auxiliary terminal through a second power transmission path and an input connected to any one of the first power input terminal, the first storage device terminal, or the additional power input terminal. Advantageously, the two voltage converters can operate independently. In an embodiment, the two voltage converters of the voltage converter system can operate simultaneously.

[0037] In an embodiment, the power management integrated circuit includes a second storage device terminal connectable with a second rechargeable energy storage device, and a third power transfer path for transferring power from the main voltage converter system to the second storage device terminal, and the controller controls a first storage parameter V Batt1 is the default upper limit storage value V Batt1-up is reached, to operate the main voltage converter system to transfer power from the first power input terminals to the second storage device terminals.

[0038] In an embodiment, the controller of the power management integrated circuit according to the present invention controls the auxiliary voltage V aux is the minimum required supply voltage V cs Lower to minimum required supply voltage V cs Above the default switching voltage V sw , disable operation of the cold-start voltage converter and enable operation of the main voltage converter system. [Brief description of the drawings]

[0039] These and further aspects of the invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which:

[0040] [Figure 1] FIG. 1 illustrates a schematic representation of an energy harvesting system according to the present disclosure. [Diagram 2] FIG. 2 illustrates a start-up process for charging a rechargeable energy storage device using the method according to the invention. [Figure 3a] FIG. 3a shows a schematic representation of an embodiment of a power management integrated circuit according to the invention having an auxiliary terminal for connecting an auxiliary rechargeable energy storage device. [Figure 3b] FIG. 3b shows a schematic representation of an embodiment of a power management integrated circuit according to the invention having an integrated on-chip capacitor. [Figure 3c]FIG. 3c shows a schematic of an embodiment of a power management integrated circuit in which a cold-start voltage converter and a main voltage converter system are used to transfer power to the auxiliary terminals and the storage device terminals, respectively. [Figure 4] FIG. 4 shows a schematic representation of an embodiment of a power management integrated circuit according to the invention having a first power input terminal and a second power input terminal. [Diagram 5] FIG. 5 illustrates a schematic diagram of an example of an energy harvesting system including a power management integrated circuit according to the present invention. [Figure 6] FIG. 6 illustrates a schematic of a first example of an energy harvesting system, where the main voltage converter system of a PMIC includes a step-down / step-up voltage converter. [Figure 7] FIG. 7 illustrates a schematic of a second example of an energy harvesting system, where the main voltage converter system of the PMIC includes a step-down / step-up voltage converter. [Figure 8] FIG. 8 illustrates a schematic of an example energy harvesting system in which a main voltage converter system of a PMIC includes an input selection circuit, the PMIC including an additional input terminal and a second input path connecting the additional input terminal with the input selection circuit. [Figure 9] FIG. 9 illustrates a schematic of an example energy harvesting system in which a main voltage converter system of a PMIC includes an input selection circuit, and the PMIC includes a second input path connecting a first storage device terminal with the input selection circuit. [Figure 10] FIG. 10 illustrates a schematic of an example power management integrated circuit including first and second storage device terminals. [Figure 11] FIG. 11 illustrates a schematic of an example of an energy harvesting system that includes first and second rechargeable energy storage devices. [Figure 12] FIG. 12 shows a schematic diagram of a first embodiment of a power management system, in which a main voltage converter system includes a first voltage converter and a second voltage converter. [Figure 13] FIG. 13 shows a second embodiment of the power management integrated circuit, in which the voltage converter system includes two voltage converters. [Figure 14]FIG. 14 illustrates a third embodiment of a power management integrated circuit, in which a voltage converter system includes two voltage converters, and the first voltage converter includes an input selection circuit. [Figure 15] FIG. 15 illustrates a fourth embodiment of the power management integrated circuit, in which a voltage converter system includes two voltage converters, and a first output terminal of the PMIC is connected to an input of the first voltage converter.

[0041] The drawing figures are not drawn to scale and are not in proportion. Generally identical elements are designated by the same reference numbers in the drawings. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] The present disclosure is described with respect to specific embodiments that are illustrative of the present disclosure and should not be construed as limiting. It will be appreciated by those skilled in the art that the present disclosure is not limited by what has been specifically shown and / or described, and alternative or modified embodiments may be developed in light of the entire teachings of the present disclosure. The depicted figures are schematic and non-limiting.

[0043] The use of the verb "to comprise" and its respective conjugations does not exclude the presence of elements other than those stated. The use of the articles "a", "an" or "the" preceding an element does not exclude the presence of a plurality of such elements.

[0044] Moreover, the terms first, second, and the like in the description and claims are used to distinguish between similar elements and are not necessarily used to describe an order in time, space, ranking, or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the disclosure described herein can operate in orders other than those described or illustrated herein.

[0045] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in one or more embodiments of the present disclosure. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification do not necessarily all refer to the same embodiment, although they may. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

[0046] In a method according to the present disclosure, energy is harvested from an energy harvester and used to charge a first rechargeable energy storage device. The method uses a system for energy harvesting.

[0047] In Fig. 1, an example of a system 100 for energy harvesting is shown in schematic form. The system 100 comprises a power management integrated circuit (PMIC) 1, which includes a main voltage converter system 20 and a controller 40 for controlling the main voltage converter system. An energy harvester 70 supplies an input voltage V in The PMIC1 is coupled to a first power input terminal 11 to supply power at the PMIC1. The PMIC1 comprises at least a power output terminal 12 coupled to the first rechargeable energy storage unit BATT1 so as to be able to output power and to charge the first rechargeable energy storage unit BATT1 with energy from the energy harvester. In this example, the application load 90 is coupled to the first rechargeable energy storage unit BATT1. The PMIC shown in Fig. 1 further comprises a cold start voltage converter 30, which is used when the main voltage converter system cannot operate, i.e. when there is no supply power available to power the controller. In practice, the controller is driven by a supply voltage V at the supply input of the controller. sup is the minimum required supply voltage V csIf it is equal to or greater than this, it is operable.

[0048] The main voltage converter system 20 should be interpreted as a system for converting input power received from an energy source, such as an energy harvester, to output power for charging a storage device. Typically, the main voltage converter system includes one or more voltage converters, and detailed embodiments of various voltage converter systems are described further below. Examples of voltage converters known in the art are DC-DC boost converters, DC-DC buck converters or DC-DC buck / boost converters.

[0049] The first rechargeable energy storage device BATT1 is for example a rechargeable battery, a capacitor or a supercapacitor.

[0050] A method for energy harvesting according to the present invention includes the steps of coupling an energy harvester 70 to an input of a main voltage converter system, coupling a first rechargeable energy storage unit BATT1 to an output of the main voltage converter system, coupling the energy harvester 70 or another energy source to an input of a cold-start voltage converter, coupling an auxiliary rechargeable energy storage unit C1 to an output of the cold-start voltage converter, and coupling the auxiliary rechargeable energy storage unit C1 to a supply input of the controller so that when the auxiliary rechargeable energy storage unit C1 is charged, it is used as a voltage source for the controller. Coupling the auxiliary rechargeable energy storage unit C1 to the supply input of the controller generates a supply voltage V sup is the auxiliary voltage V of the auxiliary rechargeable energy storage device c Corresponds to.

[0051] The method according to the invention comprises the steps of: c and monitoring a first storage parameter V indicative of the charge level of the first rechargeable energy storage device BATT1. Batt1 and monitoring the auxiliary voltage V c is the default switching voltage V swCharging the auxiliary rechargeable energy storage device C1 by operating the cold-start voltage converter until V sw ≧V cs and the auxiliary voltage V c is the default switching voltage V sw and enabling operation of the main voltage converter system and disabling operation of the cold-start voltage converter when the parameter V Batt1 is the default upper limit storage value V Batt1-up and charging the first rechargeable energy storage device BATT1 by operating the main voltage converter system as long as the voltage Vcc is lower.

[0052] This upper limit storage value V Batt1-up should be interpreted as a threshold indicating that the first rechargeable energy storage device BATT1 is charged.

[0053] In an embodiment, the first storage parameter V Batt1 corresponds to the voltage of the first rechargeable energy storage device BATT1. In another embodiment, the first storage parameter V Batt1 corresponds to the accumulated charge acquired during the process of charging the first rechargeable energy storage device BATT1, for example by a charge counter that measures the accumulated charge.

[0054] In the embodiment, the auxiliary voltage V of the auxiliary energy storage device C1 c is maintained equal to a target value. The target value is, for example, a predefined voltage value corresponding to a suitable voltage value for operating the controller. In an embodiment, the target value is a suitable or optimal supply voltage value for operating the controller. The auxiliary voltage V c To maintain V equal to the target value, the main voltage converter system or the cold-start voltage converter is used to recharge the auxiliary rechargeable energy storage device C1 with energy from the energy harvester 70.

[0055] Auxiliary voltage V cThis maintenance can be achieved, for example, by setting the upper storage limit V Batt1-up A period of charging the first rechargeable energy storage device BATT1 until is achieved, and any period thereafter, is also executed.

[0056] In an embodiment, the reduction in the charge of the auxiliary energy storage device C1 is c is subsequently supplemented to remain equal to the target value.

[0057] In another embodiment, the main voltage converter system, or alternatively the cold-start voltage converter, may be configured to convert the auxiliary voltage V c The lower threshold voltage V sup-min and the upper threshold voltage V sup-max and V cs <V sup-min <V sup-max Generally speaking, V cs <V sw ≦V sup-max and more preferably V sup-min ≦V sw ≦V sup-max In other words, the lower limit threshold voltage V sup-min is the default switching voltage V sw and the minimum required supply voltage V cs Higher.

[0058] In the embodiment, the lower threshold voltage V sup-min and the upper threshold voltage V sup-max The voltage range defined by corresponds to the range of voltages that are optimal as supply voltages for operating the controller.

[0059] In these embodiments, the auxiliary voltage V c is maintained within a predetermined voltage range, and the auxiliary voltage V c is the lower threshold voltage V sup-min If the voltage drops below the auxiliary voltage V c is the lower threshold voltage V sup-min Higher upper threshold voltage V sup-maxrecharging the auxiliary rechargeable energy storage device C1 with energy from the energy harvester until

[0060] In FIG. 2, an example of a process for charging a first rechargeable energy storage device according to the method of the present disclosure is illustrated in schematic form. Batt1 In this example, the voltage V Batt1 , and auxiliary V c is shown as a function of time, and the auxiliary voltage of the auxiliary energy storage device C1 is lowered to a lower threshold voltage V sup-min and the upper threshold voltage V sup-max 1 illustrates charging the first rechargeable energy storage device BATT1 while maintaining the auxiliary voltage V c is the lower threshold voltage V sup-min During its startup period, which is lower than the switching voltage V sw , which in this example is V sup-min ≦V sw ≦V sup-max After that, the main voltage converter system starts to operate, and this period is indicated as "M-VC" in FIG. 2. In an embodiment, the auxiliary voltage V c is the lower threshold voltage V sup-min If the voltage drops to the upper threshold voltage V, the main voltage converter system repeatedly stops charging the first rechargeable energy storage device and instead sup-max In another embodiment not shown in FIG. 2, the auxiliary energy storage device is recharged until the auxiliary voltage V c Instead of keeping V within a certain voltage range, the auxiliary voltage V c can also be maintained equal to a target value.

[0061] As further illustrated in FIG. 2, the main voltage converter system is configured to regulate an upper reserve value V Batt1-up In this example, V Batt1is the voltage, and the upper limit storage value V Batt1-up is the upper threshold voltage V of the auxiliary energy storage device C1 sup-max In fact, the auxiliary energy storage device is maintained electrically isolated from the first rechargeable energy storage device, so that the voltage V sup and V Batt1 are independent of each other and can therefore always have different values.

[0062] In the embodiment, the upper threshold voltage V sup-max can be, for example, a value between 2V and 3V, for example 2.5V, and the first energy storage device BATT1 has an upper limit storage value V Batt1-up In another embodiment, V Batt1-up V sup-max For example, in an embodiment, V sup-max can be 5V, and V Batt1-up can be a value less than 5V.

[0063] In an embodiment, the first rechargeable energy storage device BATT1 has an upper storage value V Batt1-up Battery ready threshold below V Batt1-ready When charged to , the energy stored in the first rechargeable energy storage device BATT1 can be used to power an application load.

[0064] In an embodiment, the first rechargeable energy storage device BATT1 has an energy storage capacity that is more than a hundred times, preferably more than a few thousand times, the energy storage capacity of the auxiliary rechargeable energy storage device C1. In some embodiments, the energy storage capacity of BATT1 can even be more than a million times the storage capacity of C1. In this way, the time to charge the auxiliary energy storage device is very short compared to the charging time of the first rechargeable energy storage device. For example, the auxiliary rechargeable energy storage device C1 can be a capacitor with a storage capacity in the range of 0.1 nanofarads to 100 microfarads, and the first rechargeable energy storage device can be a supercapacitor with a storage capacity in the range of 1 microfarad to 100 farads.

[0065] As described above, the auxiliary voltage V of the auxiliary rechargeable storage device C1 c The lower threshold voltage V sup-min to the upper threshold voltage V sup-max The maintaining within the auxiliary voltage V during the charging process of the first rechargeable energy storage unit BATT1, for example, c By monitoring the auxiliary voltage V c is the lower threshold voltage V sup-min When it drops lower, this is accomplished by recharging the auxiliary energy storage device C1.

[0066] In a preferred embodiment, recharging the auxiliary energy storage device C1 is performed by operating the main voltage converter. In another embodiment, recharging the auxiliary energy storage device C1 is performed by operating the cold start voltage converter.

[0067] In some embodiments, as discussed below, instead of using energy from the energy harvester, energy from the first rechargeable energy storage device BATT1 can also be used to recharge the auxiliary energy storage device. Therefore, there are at least two options for recharging the auxiliary energy storage device using the main voltage converter system: energy from the energy harvester or energy from the first rechargeable energy storage device. The second option is to recharge the auxiliary energy storage device when the first energy storage device BATT1 is fully charged and has a low storage value, e.g., V Batt1-min This is only possible if a higher voltage is reached.

[0068] In an embodiment, the first option is the auxiliary voltage V c is the lower threshold voltage V sup-min It is triggered if the aircraft descends lower.

[0069] In an embodiment, the second option is the auxiliary voltage V c is the given critical threshold voltage V T-B If the voltage drops below V cs <V T-B <V sup-min In fact, if the energy harvester does not provide any power, then the auxiliary voltage V c is the lower threshold voltage V sup-min If the auxiliary voltage V drops below c continues to drop, eventually reaching a critical threshold voltage V T-B Descend lower.

[0070] In another embodiment, the second option is the auxiliary voltage V c is the lower threshold voltage V sup-min It is triggered if it drops lower and if it is monitored that the energy harvester is not producing energy or not producing enough energy at that moment. The availability of energy from the energy harvester can be monitored with the monitoring unit, for example by monitoring the input voltage at the first input terminal or any other parameter indicative of the input power.

[0071] Auxiliary voltage V c is the lower threshold voltage V sup-min A first option for recharging the auxiliary rechargeable storage device C1 with energy from the energy harvester when the auxiliary voltage V drops lower comprises the steps of disconnecting the output of the main voltage converter system from the first rechargeable energy storage device BATT1, coupling the output of the main voltage converter system to the auxiliary rechargeable storage device C1, and coupling the auxiliary voltage V c is the upper threshold voltage V sup-max and operating the main voltage converter system to recharge the auxiliary rechargeable energy storage device C1 until an output of the main voltage converter system is connected to the auxiliary rechargeable energy storage device C1 and coupled to the first rechargeable energy storage device BATT1.

[0072] Auxiliary voltage V c is the given critical threshold voltage V T-B If it drops lower than V cs <V T-B <V sup-min A second option for recharging the auxiliary rechargeable energy storage unit C1 with energy from the first rechargeable energy storage unit BATT1 when monitoring that the energy harvester is not generating energy or that the energy harvester is not generating energy, includes the steps of: disconnecting the energy harvester from the input of the main voltage converter system; disconnecting the first rechargeable energy storage unit BATT1 from the output of the main voltage converter system; coupling the first rechargeable energy storage unit BATT1 to the input of the main voltage converter system; coupling the output of the main voltage converter system to the auxiliary rechargeable energy storage unit C1; and coupling the auxiliary voltage V c is the upper threshold voltage V sup-max and operating the main voltage converter system to recharge the auxiliary rechargeable energy storage unit C1 until C1 reaches C1. The energy harvester is then recoupled to the input of the main voltage converter system and the first rechargeable storage unit BATT1 is recoupled to the output of the main voltage converter system.

[0073] In an embodiment, the main voltage converter system 20 includes a buck / boost converter, which is V in >(V out +Δ), V in <(V out -Δ), it operates in boost mode and V in =V out ±Δ, where V in and V out are the input and output voltages of the main voltage converter system, respectively, and Δ is the operating parameter of the step-down / step-up voltage converter.

[0074] If the energy harvester is for example no longer operable, the first storage parameter V Batt1 For example, the default lower storage value V Batt1-min If lower, the auxiliary voltage V c is the lower threshold voltage V sup-min When the auxiliary voltage V drops lower, a situation may arise where there is no power available to recharge the auxiliary energy storage device, and therefore the auxiliary voltage V c is the minimum supply voltage V required to operate the controller. cs As mentioned above, this minimum required supply voltage V cs is the lower threshold voltage V sup-min A lower threshold voltage.

[0075] In an embodiment, the main voltage converter system is c equal to the target value, or the auxiliary voltage V c within a certain voltage range, and the auxiliary voltage V c is the minimum required supply voltage V cs If a lower voltage condition occurs, the cold start voltage converter will start at the default switching voltage V swThe auxiliary rechargeable energy storage device C1 is then operable to recharge the auxiliary rechargeable energy storage device C1 until the required minimum supply voltage V is reached. Thereafter, operation of the cold-start voltage converter is disabled and operation of the main voltage converter system is enabled. cs is illustrated diagrammatically in FIG.

[0076] In the embodiments, the main voltage converter system 20 includes a first voltage converter 20a and a second voltage converter 20b. In these embodiments, the step of charging the first rechargeable energy storage device BATT1 with energy from the energy harvester 70 is performed by operating the first voltage converter 20a, and the step of recharging the auxiliary rechargeable energy storage device C1 with energy from the energy harvester 70 or from the first rechargeable energy storage device BATT1 is performed by operating the second voltage converter 20b. The step of recharging the auxiliary rechargeable energy storage device C1 is performed independently of the step of charging the first rechargeable energy storage device BATT1, i.e. the step of controlling the charging of the first auxiliary device is not affected by the step of controlling the charging of the auxiliary rechargeable energy storage device and vice versa.

[0077] In an embodiment, the voltage converter used to recharge the auxiliary rechargeable energy storage unit C1 is different from the voltage converter used to charge the first rechargeable energy storage unit BATT1, and charging of the first rechargeable energy storage unit BATT1 can be performed simultaneously with charging of the auxiliary rechargeable energy storage unit C1. According to a second aspect of the present invention, there is provided a power management integrated circuit for energy harvesting capable of performing the method for energy harvesting discussed above.

[0078] An integrated circuit for energy harvesting according to the present invention should be construed as a microchip including an integrated circuit and a number of input and output pins (also called terminals). The microchip may have, for example, 16-32 terminals. Typically, the microchip has a small package and a square or rectangular footprint with sides measuring 1-5 mm. Various examples of PMIC 1 according to the present invention are shown in Figures 3a, 3b, 3c, 4, 10, and 12-15, respectively, and examples of energy harvesting systems 100 including PMIC 1 are illustrated in Figures 5-9 and 11. These examples are discussed further below.

[0079] In an embodiment, a PMIC 1 for energy harvesting includes one or more power input terminals for receiving input power from an energy harvester or another power source, a first storage device terminal 12 connectable to a first rechargeable energy storage device BATT1, and an auxiliary terminal 9 connectable to an auxiliary rechargeable energy storage device C1. The auxiliary terminal is an input / output terminal capable of both transferring charge from the PMIC to the auxiliary rechargeable energy storage device and vice versa. In another embodiment, instead of an auxiliary terminal connectable to an external auxiliary rechargeable energy storage device, as shown in FIG. 3b, the PMIC includes an integrated on-chip capacitor C int Includes.

[0080] In some embodiments, the first storage device terminal 12 is a power output terminal for outputting power to the first rechargeable energy storage device, and in other embodiments, the first storage device terminal 12 is an input / output terminal suitable for both outputting power to the first rechargeable energy storage device and inputting power from the first rechargeable energy storage device to the PMIC.

[0081] The PMIC 1 further includes a main voltage converter system 20 for receiving input power through a first power input terminal 11 of the one or more power input terminals, a controller 40 configured to control the main voltage converter system 20, and a cold-start voltage converter 30. The cold-start voltage converter 30 is connected to i) an auxiliary terminal 9 or to an integrated on-chip capacitor C int ii) receiving input power through a first power input terminal 11 or through a second power input terminal 8 of the one or more power input terminals; iii) if a minimum input voltage is available at the input of the cold-start voltage converter, and if a supply voltage V sup However, the minimum supply voltage V cs It is configured to initiate operation when the voltage Vcc is lower than the threshold voltage Vcc.

[0082] In the embodiment shown in Figures 3a and 3b, the main voltage converter system and the cold-start voltage converter both receive input power through the same input terminal 11. In other embodiments, for example as shown in Figure 4, the main voltage converter system and the cold-start voltage converter receive input power through different input terminals, indicated with reference numerals 11 and 8.

[0083] As discussed above, the controller 40 controls the supply voltage V sup However, the minimum supply voltage V cs If it is equal to or greater than this, it is operable.

[0084] In an embodiment, as illustrated diagrammatically in Figures 3a and 4, the main voltage converter system is configured to output power through multiple power transmission paths, including at least a first power transmission path P-O1 and a second power transmission path P-O2 configured to electrically connect the main voltage converter system with the first storage device terminal 12 and the auxiliary terminal 9, respectively.

[0085] In some embodiments, the main voltage converter system includes only a single voltage converter, for example as illustrated in Figures 6-9, and the main voltage converter system 20 includes an output selection circuit 21 controlled by the controller and configured to select one power transmission path from the multiple power transmission paths so as to output power via the selected power transmission path. In other words, the main voltage converter system 20 can selectively output power to either the first storage device terminals or to the auxiliary terminals.

[0086] In an embodiment, as shown in FIG. 3b, power is transferred from the main voltage converter system through a second power transmission path P-O2 to an integrated on-chip capacitor C int can be transmitted to.

[0087] In an embodiment, the main voltage converter system 20 includes an output selection circuit 21, and one or more switches S1, S2 are provided to select a power output path, as illustrated diagrammatically in Figures 3a, 3b and 4. When switch S1 is open and switch S2 is closed, power can be transferred from the main voltage converter system to the first storage device terminal 12, and when switch S1 is closed and switch S2 is open, power can be transferred from the main voltage converter system to the auxiliary terminal 9.

[0088] This implies a definition that when a particular power transmission path is selected through the output selection circuit 21, the other remaining power transmission paths are deselected such that only one power transmission path can be selected at a time. In an embodiment, for example as illustrated diagrammatically in FIG. 3c, the main voltage converter system 20 is used to transmit power via the first power transmission path P-O1 to the first storage device terminal 12, while the cold-start voltage converter 30 is used to transmit the auxiliary voltage V aux The lower threshold voltage V sup-min To maintain the above, the auxiliary terminal (9) or the integrated on-chip capacitor C int In these embodiments, therefore, the cold-start voltage converter is used to transfer power to the auxiliary voltage Vaux is the minimum required supply voltage V cs Lower to the default switching voltage V sw First, the internal node N aux Not only can it be used to charge the V aux The lower threshold voltage V sup-min To maintain the above, the internal node N aux It is also used to recharge the battery.

[0089] In other embodiments according to the invention, as illustrated in Figures 13-15, the main voltage converter system includes two voltage converters, a first voltage converter 20a having an output coupled to a first power transmission path P-O1, and a second voltage converter 20b having an output coupled to a second power transmission path P-O2. Therefore, in these embodiments with two output paths and two associated voltage converters, the output path selection circuit is not required. However, in an embodiment of the PMIC having a third power transmission path P-O3, for example as illustrated in Figure 12, the output path selection circuit can select the first voltage converter 20a to output power either via the first output path P-O1 or via the third output path P-O3.

[0090] The PMIC is connected to an internal node N aux Contains the internal node N aux is the auxiliary voltage of the internal node V aux corresponds to the voltage at the auxiliary terminal 9, or the integrated on-chip capacitor C int The auxiliary terminal 9 and the integrated on-chip capacitor C int Electrically connected to the internal node N aux is the supply voltage at the input of the controller relative to the auxiliary voltage V aux 3a to 15, the internal node N aux is the auxiliary voltage V auxis a voltage node that is electrically isolated from the first storage device terminal 12 such that is independent of the voltage at the first storage device terminal 12.

[0091] As described above and illustrated in Figures 3a and 3b, the second power transmission path P-O2 connects the output of the main voltage converter system with the auxiliary terminal. For the embodiment shown in Figure 3b, the internal node N aux The auxiliary voltage is provided by the integrated on-chip capacitor C int corresponds to a voltage of

[0092] A monitoring unit 45 coupled to the controller 40 monitors the voltage V aux , and a first storage parameter V at the first storage device terminal 12 is monitored. Batt1 In some embodiments, the first storage parameter V Batt1 is the voltage sensed at the first storage device terminal 12, while in other embodiments, the first storage parameter V Batt1 may be the accumulated charge.

[0093] The controller stores a first stored parameter V Batt1 is the default upper limit storage value V Batt1-up As long as the auxiliary voltage V aux equal to the target value, or alternatively the auxiliary voltage V aux The lower threshold voltage V sup-min and the upper threshold voltage V sup-max To keep the voltage between int The target value or alternatively a lower threshold voltage V sup-min is the minimum required supply voltage V cs The target value is, for example, a suitable voltage to operate the controller.

[0094] In embodiments, the controller is further configured to enable operation of a cold-start voltage converter to recharge the auxiliary rechargeable energy storage device C1. In these embodiments, the auxiliary voltage V c is the lower threshold voltage V sup-min to the minimum required supply voltage V cs If the voltage is reduced to a value less than the default switching voltage V sw , the operation of the cold-start voltage converter is enabled to recharge the auxiliary rechargeable energy storage device C1 until Vcc reaches Vcc V. Thereafter, the operation of the cold-start voltage converter is disabled and the operation of the main voltage converter system is enabled.

[0095] In an embodiment, the controller aux equal to the target value and maintain the predetermined switching voltage V sw is equal to or greater than the target value.

[0096] In an embodiment, the controller aux The lower threshold voltage V sup-min and the upper threshold voltage V sup-max The voltage range between the preset switching voltage V sw is the lower threshold voltage V sup-min That's all.

[0097] For embodiments, the main voltage converter system includes two dedicated voltage converters, for example as illustrated in Figures 13-15, and the transfer of power to the first storage device terminal can be performed in parallel and independently of the transfer of power to the auxiliary terminal. In other embodiments, for example as illustrated in Figure 6, the outputs of the voltage converters are switched using an output selection circuit 21, and the transfer of charge to the first storage device terminal and the auxiliary terminal cannot be performed simultaneously.

[0098] The controller 40 controls the auxiliary voltage V aux is the minimum required supply voltage V cs Voltage V from a lower value cs The above-specified switching voltage V sw, disabling operation of the cold-start voltage converter 30 and enabling operation of the main voltage converter system. This is illustrated diagrammatically in Figure 2, as discussed above, which illustrates switching from an operation period CS-VC of the cold-start voltage converter to a period M-VC of the main voltage converter system.

[0099] The controller 40 is aux and V Batt1 and comparing the actual value with a predefined threshold value. More specifically, the main voltage converter system 20 is further configured to: a)V sup-min ≦V aux If, and V Batt1 <V Batt1-up If, however, V Batt1-up is V Batt1 is the default upper storage limit for V sup-min is V aux , and in the steps of selecting the first path P-O1 and operating the main voltage converter system to transmit power from the first power input terminal 11 to the first storage device terminal 12, the step of transmitting power to the first storage device terminal 12 is performed by selecting a first path P-O1 from the first power input terminal 11 and operating the main voltage converter system to transmit power to the first storage device terminal 12 at a predetermined lower threshold voltage V Batt1 is the default upper limit storage value V Batt1-up the steps of selecting and activating being stopped when b) V aux is the lower threshold voltage V sup-min Higher to lower threshold voltage V sup-min If the auxiliary voltage V drops to a lower value, selecting the second power transmission path P-O2 and aux is the upper threshold voltage V sup-max and operating the main voltage converter system until the voltage V is increased to V sup-max >V sup-min In an alternative embodiment, as discussed above, the controller may control the auxiliary voltage V cThe control circuit is configured to operate the main voltage converter so as to continue to maintain the target voltage Vout equal to the target value.

[0100] As discussed above, the voltage V aux and controlling the main voltage converter system to regulate the supply voltage V sup is the value V sup-min or the threshold voltage V sup-min and V sup-max The voltage at the first output terminal is also maintained within the supply voltage V sup For example, V Batt1 If is a constant voltage, the upper limit storage value V Batt1-up can be equal to 4.5V, and the upper threshold voltage V sup-max can be equal to, for example, 2.5V or any other suitable value.

[0101] Use of the term "controller" should be interpreted in the broadest sense as generally being an electronic digital circuit that includes combinator logic. A controller that controls a main voltage converter system is configured, for example, to control the power switches of the main voltage converter system.

[0102] In a specific embodiment, instead of using an external auxiliary capacitor that can be coupled to the auxiliary output terminal 12, the PMIC includes an integrated on-chip capacitor. In this specific embodiment, the second power transfer path P-O2 is configured to electrically connect the output of the main voltage converter system with the integrated on-chip capacitor. In this embodiment, the internal node N aux Also electrically connected to at least i) the integrated on-chip capacitor, ii) the supply input of the controller, and iii) the output of the cold-start voltage converter.

[0103] In an embodiment, the monitoring unit 45 monitors the parameter V Batt1 and V auxThe signal comparator may be either an analog signal comparator or a digital signal comparator known in the art. For embodiments in which a digital signal comparator is used, generally the analog signal V Batt1 and V aux is first digitized using an ADC (Analog to Digital Converter). The predefined threshold can be a value stored locally by the controller, or the predefined threshold can be generated by a reference voltage generator, or a voltage configuration external to the PMIC can be used and the threshold can be sent through a configuration terminal or the controller.

[0104] The cold-start voltage converter 30 operates when a minimum input voltage is available at the input of the cold-start voltage converter, and when V sup <V cs , i.e. when the main voltage converter system is unable to operate, i.e. in the so-called reset mode.

[0105] In an embodiment, the cold-start voltage converter includes a charge pump and an oscillator that provides a clock signal to the charge pump. The output of the charge pump is then supplied with a voltage V aux , which provides the supply voltage V for the main voltage converter system as described above. sup The oscillator is switched on by an enable signal that is generated when the input voltage of the cold-start voltage converter is higher than a minimum input voltage. This minimum voltage is, for example, a reference voltage generated by a reference voltage generator. The oscillator is switched off and therefore the cold-start voltage converter operates at the supply voltage V sup is the switching voltage V sw is reached, the main voltage converter system is then switched on.

[0106] An example of an energy harvesting system including a PMIC1, an energy harvester 70 coupled to a first power input terminal 11, a first rechargeable energy storage device BATT1 coupled to a first storage device terminal 12, and an auxiliary rechargeable storage device C1 coupled to an auxiliary terminal 9 is shown generally in Figure 5. In this example, an application load 90 is connected to the first rechargeable energy storage device BATT1.

[0107] As further illustrated in FIG. 5, the main voltage converter system 20 may use an inductor 25 that is generally located outside the PMIC 1 and may be coupled to the PMIC, for example, by two dedicated terminals 14, 15, or by any other suitable coupling means.

[0108] In a preferred embodiment, the main voltage converter system 20, as illustrated in Fig. 6 and Fig. 7, includes a DC-DC buck / boost voltage converter, which can operate in either boost mode, buck mode or buck-boost mode depending on the input and output voltage of the main voltage converter system. When the input voltage of the main voltage converter system is lower than the output voltage of the voltage converter, the buck / boost voltage converter operates in boost mode. On the other hand, the buck / boost voltage converter operates in buck mode when the input voltage is higher than the output voltage. When the input and output voltage are approximately the same, the converter operates in buck / boost mode. The output voltage of the main voltage converter system considered to determine the operation mode of the buck / boost voltage converter depends on the selected power transmission path. For example, when the first power transmission path P-O1 or the second power transmission path P-O2 is selected, the considered output voltage corresponds to the voltage at the first output terminal 12 and the voltage at the auxiliary terminal 9, respectively. Similarly, for embodiments in which the main voltage converter system has multiple input paths, each connected to a corresponding power input terminal, the input voltage considered for defining the operating mode of the buck / boost converter corresponds to the voltage at the input terminal of the selected input path.

[0109] The main voltage converter system 20 includes a number of power switches, for example the embodiment illustrated in FIG. 6 includes an output selection circuit 21 with switches S1 and S2, and the step-down / boost voltage converter 20a includes switches S3A, S3B, S4A and S4B. The embodiment of the main voltage converter system illustrated in FIG. 7 is an embodiment including fewer switches than the embodiment illustrated in FIG. 6. In fact, in the embodiment of FIG. 7, some switches of the step-down / boost voltage converter 20a also function as selection switches of the output selection circuit. The function of switch S3B used during nominal operation of the step-down / boost voltage converter of FIG. 6 is performed by switch S2 in FIG. 7 at the same time as performing the function of selecting the first power transmission path P-O1 when switch S1 remains open. Similarly, when switch S2 remains open when selecting the second power transmission path P-O2, switch S1 is used during nominal operation of the step-down / boost voltage converter instead of switch S3B illustrated in FIG. 6. In other words, the switches for the output selection circuit can be shared with the switches for the nominal operation of the step-down / boost voltage converter. The embodiment of the voltage converter system 20 shown in FIG. 9 includes an output selection circuit 21 with switches S1 and S2, an input selection circuit 22 with switches S5 and S6, and a step-down / boost voltage converter with switches S3A, S3B, S4A, and S4B. In the embodiment of FIG. 8, the number of switches is reduced compared to the embodiment of FIG. 9, since both the output selection circuit and the input selection circuit are shared with the step-down / boost voltage converter. The switches should be interpreted as electronic switches configured to open or close a conductive path or conductor. These switches are, for example, analog electronic switches known in the art. These switches use, for example, MOS transistors.

[0110] To operate the embodiment of the buck / boost voltage converter shown in FIG. 7 in boost mode to charge the first storage device with energy from the energy harvester, switch S1 remains open, switch S4B remains closed, and switch S4A remains open during charging of the first energy storage device BATT1. The boost mode starts with a magnetic energy charging phase of inductor 25, switch S3A closes and switch S2 opens, followed by a magnetic energy discharging phase, switch S3A opens and switch S2 closes. By repeatedly controlling switches S3A and S2 as known in the art, power is transferred from the energy harvester to the first rechargeable energy storage device BATT1 in boost mode.

[0111] To operate the buck / boost voltage converter shown in Fig. 7 in buck mode to charge the first energy storage device, switch S2 remains closed and switch S3A and switch S1 remain open while the first energy storage device BATT1 is being charged. The buck mode starts with a magnetic energy charging phase of inductor 25, switch S4A opens and switch S4B closes, followed by a magnetic energy discharging phase, switch S4A closes and switch S4B opens. By repeatedly controlling switches S4A and S4B as known in the art, power is transferred from the energy harvester to the first rechargeable energy storage device BATT1 in buck mode.

[0112] As described above and illustrated with the example shown in FIG. 7, the switch S2 is not only used as a standard switch required to operate the DC / DC step-down / step-up voltage converter, but also forms part of the output selection circuit 21. By actually opening the switch S2 and closing the switch S1, the second power transmission path P-O2 is selected. In this way, the number of electronic switches to perform both the nominal operation function of the voltage converter and the power transmission path selection function is limited. However, using dedicated switches in the input and / or output selection circuit, as shown for example in FIG. 9 and FIG. 6, also has advantages, namely the fact that the parasitic capacitance of the node switched from the inductor 25 is small and therefore the power loss is small.

[0113] In a preferred embodiment, as illustrated in Fig. 10, the power management integrated circuit includes a second storage device terminal 13 connectable with a second rechargeable energy storage device BATT2, and the multiple power transmission paths include a third power transmission path P-O3 configured to electrically connect an output of the main voltage converter system 20 with the second storage device terminal 13. The third power transmission path can be selected by a switch S7 shown in Fig. 10.

[0114] Generally, the second rechargeable energy storage device BATT2 is connected to a second storage parameter V, as shown diagrammatically in FIG. 11, which is indicative of the charge level of the second rechargeable energy storage device BATT2. Batt2 has.

[0115] Preferably, the controller 40 controls the first storage parameter V Batt1 is the default upper limit storage value V Batt1-up , is reached, selects the third path P-O3 and activates the main voltage converter system 20 to transfer power from the first power input terminal 11 to the second storage device terminal 13. Advantageously, the first rechargeable energy storage device is configured to operate the main voltage converter system 20 to transfer power from the first power input terminal 11 to the second storage device terminal 13 when the upper storage value V Batt1-upWhen the charge level defined by is reached, additional energy can be stored for later use, e.g. when the energy harvester is not providing any power, by charging a second rechargeable energy storage device BATT2 connected to the second storage device terminal 13. The second energy storage device can, for example, have a large energy storage capacity and can therefore be used as a large energy reservoir.

[0116] In an embodiment, for example as shown in Figures 8, 9 and 11, the main voltage converter system 20 includes an input selection circuit 22 controlled by a controller 40 and configured to select one input path from a plurality of input paths to receive input power via the selected input path. In this manner, the main voltage converter system can receive input power from a variety of energy sources.

[0117] In an embodiment of the energy harvesting system, as shown in Fig. 8 and Fig. 11, the multiple input paths for supplying power to the main voltage converter system include at least a first input path P-I1 and a second input path P-I2 configured to electrically connect the first power input terminal 11 and the further power input terminal 18, respectively, with the input of the main voltage converter system 20. The first rechargeable energy storage device BATT1 or the second rechargeable energy storage device BATT2 can be electrically connected to the further power input terminal 18, for example, by an external connection to a PMIC, and the second input path P-I2 can be selected by the input selection circuit 22 by closing switch S6 and opening switch S5. This allows energy to be transferred from the second rechargeable energy storage device BATT2 to the first rechargeable energy storage device BATT1 when the energy harvester 70 no longer supplies any power. In this way, the application load 90 can still continue to operate even under the condition that the energy harvester no longer supplies any power.

[0118] 8, the PMIC includes an additional power input terminal 18 and a second input terminal P-I2 electrically connecting the additional input terminal 18 with the input of the main voltage converter system 20. In this way, the auxiliary voltage V aux is the lower threshold voltage V sup-min When the voltage drops lower and the energy harvester does not provide energy or does not provide enough energy, by selecting the second input path P-I2, the main voltage converter system 20 can transfer charge from the further power input terminal 18 to the auxiliary output terminal 9. In an embodiment, an additional energy harvester or power source can be connected to the further power terminal 18. In another embodiment, the first output terminal 12 can be electrically connected to the further input terminal 18, for example to be able to transfer charge from the first output terminal to which the first rechargeable energy storage device BATT1 is connected, to the further input terminal 18.

[0119] 9, the second input path P-I2 is an internal path of the PMIC 1 that connects the first output terminal 12 with the input of the main voltage converter system 20. As mentioned above, the auxiliary voltage V aux is the lower threshold voltage V sup-min By dropping lower and selecting the second input path P-I2, the main voltage converter system 20 can transfer charge from the first output terminal 12 to the auxiliary output terminal 9 when the energy harvester is not supplying energy or is not supplying enough energy.

[0120] In the embodiment including the additional power input terminal 18 described above, the controller 40 selects the second input path P-I2, selects the second power transmission path P-O2, and supplies the auxiliary voltage V aux is the upper threshold voltage V sup-max In an embodiment, this selection of the second input path and the second output path is further configured to operate the main voltage converter system 20 until the second input path and the second output path are increased to V aux is the lower threshold voltage V sup-min Higher than the given critical threshold voltage V T-B However, if the V cs <VT-B <V sup-min The given critical threshold voltage V T-B is illustrated diagrammatically in FIG. 2. In an alternative embodiment, the selection of the second input path and the second output path is determined by the auxiliary voltage V c is the lower threshold voltage V sup-min This occurs when the monitor unit detects that the input voltage drops lower and at the same time there is no input power available at the first input terminal.

[0121] 11, the energy harvesting system also includes a primary battery 80 connected to the additional input terminal 16 of the PMIC 1. A switch SW can select between the energy harvester 70 and the primary battery 80. The primary battery 80 is a backup energy source that can be used when the energy harvester 70 is not operational and the storage device is full.

[0122] As generally illustrated in Figure 11, the input of the main voltage converter system 20 is also connected to another input terminal 17 coupled to an external capacitor C2, which is capable of stabilizing the input voltage of the main voltage converter system.

[0123] As discussed above, the cold-start voltage converter 30 receives input power from an energy harvester 70, or from another energy source, such as a primary battery, another storage device, or an auxiliary supply such as a USB connection. This is illustrated in Figure 11, where an auxiliary energy source 75 is coupled to a dedicated input terminal 8 of the PMIC for providing input power to the cold-start voltage converter. Advantageously, such an auxiliary supply also allows testing of the PMIC without having to wait for energy harvesting to occur.

[0124] For example, in the embodiment shown in FIG. 6 and FIG. 7, the main voltage converter system 20 includes a single voltage converter 20a, both of which are used to transmit power to either the first output terminal 12 or the auxiliary output terminal 9. However, the main voltage converter system 20 of the PMIC according to the present invention is not limited to one voltage converter or to a specific number of voltage converters. For example, as discussed above, FIG. 12-FIG. 15 show an embodiment of the main voltage converter system 20 including a first voltage converter 20a and a second voltage converter 20b. In these examples, the first voltage converter is configured to transmit power to the first output terminal 12 or to the second output terminal 13, and the second voltage converter is configured to transmit power to the auxiliary output terminal 9. The first and second voltage converters can use the same common inductor 25, or the first and second voltage converters can use first and second inductors, respectively. Advantageously, when using the first and second voltage converters, the two voltage converters can be used simultaneously.

[0125] In an embodiment of the energy harvesting system in which capacitors and / or supercapacitors are used, the first rechargeable energy storage device BATT1 has an energy storage capacity between 1 microfarad and 100 farads, and the auxiliary rechargeable energy storage device C1 has an energy storage capacity between 0.1 nanofarads and 100 microfarads.

Claims

1. A method for energy harvesting using a power management integrated circuit, comprising a cold start voltage converter, a main voltage converter system (20), and a controller (40) for controlling the main voltage converter system, the controller controlling a supply voltage (V ｓｕｐ ) is the minimum required supply voltage (V ｃｓ ) or more, - coupling an energy harvester (70) to an input of the main voltage converter system; - coupling a first rechargeable energy storage device (BATT1) to an output of the main voltage converter system; - coupling the energy harvester (70) or another energy source to an input of the cold-start voltage converter; - coupling an auxiliary rechargeable energy storage device (C1), preferably a capacitor, to the output of said cold-start voltage converter; - coupling the auxiliary rechargeable energy storage device (C1) to the supply input of the controller in order to use the auxiliary rechargeable energy storage device (C1) as a voltage source for the controller when charging; The auxiliary voltage (V ｃ ), and monitoring a first storage parameter (V) indicative of the charge level of the first rechargeable energy storage device (BATT1). Ｂａｔｔ１ ) monitoring the The auxiliary voltage (V ｃ ) is the minimum required supply voltage (V ｃｓ ) or higher than the specified switching voltage (V ｓｗ Charging the auxiliary rechargeable energy storage device (C1) by operating the cold-start voltage converter until a cold-start voltage converter (C1) is reached; The auxiliary voltage (V ｃ ) is the predetermined switching voltage (V ｓｗ ), enabling operation of the main voltage converter system and disabling operation of the cold-start voltage converter; the first storage parameter (V Ｂａｔｔ１ ) is the default upper limit storage value (V Ｂａｔｔ１－ｕｐ operating the main voltage converter system (20) to charge the first rechargeable energy storage device (BATT1) with energy from the energy harvester (70) as long as the voltage of the first rechargeable energy storage device (BATT1) is lower than and maintaining the auxiliary rechargeable energy storage device (C1) electrically isolated from the first rechargeable energy storage device (BATT1) during the charging of the first rechargeable energy storage device (BATT1); The auxiliary voltage (V ｃ )of a) equal to the target value, or alternatively b) Lower threshold voltage (V ｓｕｐ－ｍｉｎ ) and the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ) higher than the upper threshold voltage (V ｓｕｐ－ｍａｘ ) within a voltage range between The target value and the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ) is the predetermined switching voltage (V ｓｗ ) or less, and the minimum required supply voltage (V ｃｓ ), and said maintaining the auxiliary voltage equal to the target value or within the voltage range comprises operating the main voltage converter system or, alternatively, operating the cold-start voltage converter to recharge the auxiliary energy storage device (C1) with energy from the energy harvester (70).

2. 10. The method of claim 1 , The auxiliary voltage (V ｃ ) equal to a target value, The auxiliary voltage (V ｃ Continuing to supplement the reduction in the charge of the auxiliary energy storage device (C1) so as to maintain the target value of the auxiliary energy storage device (C2) equal to the target value; The auxiliary voltage (V ｃ ) to the lower threshold voltage (V ｓｕｐ－ｍｉｎ ) to the upper threshold (V ｓｕｐ－ｍａｘ The step of maintaining in The auxiliary voltage (V ｃ ) is the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ), the auxiliary voltage (V ｃ ) is the upper limit threshold voltage (V ｓｕｐ－ｍａｘ recharging the auxiliary rechargeable energy storage device (C1) until it reaches a maximum rechargeable energy storage capacity (T1).

3. 10. The method of claim 1 , The main voltage converter system supplies the auxiliary voltage (V ｃ ) is the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ) below 0.5 V, the auxiliary rechargeable energy storage device (C1) is operated to recharge energy from the energy harvester (70), the recharging step comprising: i) disconnecting the output of the main voltage converter system from the first rechargeable energy storage device (BATT1); ii) coupling the output of the main voltage converter system to the auxiliary rechargeable energy storage device (C1), and ｃ ) is the upper limit threshold voltage (V ｓｕｐ－ｍａｘ operating the main voltage converter system to recharge the auxiliary rechargeable energy storage device (C1) until iii) the auxiliary voltage (V ｃ ) is the upper limit threshold voltage (V ｓｕｐ－ｍａｘ ), disconnecting the output of the main voltage converter system from the auxiliary rechargeable energy storage device (C1) and coupling the output of the main voltage converter system to the first rechargeable energy storage device (BATT1).

4. The method according to claim 1 or 3, The auxiliary rechargeable energy storage device (C1) a) the first storage parameter (V Ｂａｔｔ１ ) is the default lower storage value (V Ｂａｔｔ１－ｍｉｎ ) higher, b) the auxiliary voltage (V ｃ ) is the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ) and the energy harvester does not provide energy, or ｃ ) is the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ) to a value higher than the predefined critical threshold voltage (V Ｔ－Ｂ ) if it descends lower than V ｃｓ <V Ｔ－Ｂ <V ｓｕｐ－ｍｉｎ And V ｃｓ , V Ｔ－Ｂ and V ｓｕｐ－ｍｉｎ are the minimum required supply voltage, the critical threshold voltage, and the lower threshold voltage, respectively, and are recharged with energy from the first rechargeable energy storage device (BATT1); The recharging step includes: i) disconnecting the energy harvester (70) from the input of the main voltage converter system; ii) disconnecting the first rechargeable energy storage device (BATT1) from the output of the main voltage converter system; iii) coupling the first rechargeable energy storage device (BATT1) to the input of the main voltage converter system; iv) coupling the output of the main voltage converter system to the auxiliary rechargeable energy storage device (C1) and coupling the auxiliary voltage V ｃ is the upper limit threshold voltage (V ｓｕｐ－ｍａｘ operating the main voltage converter system to recharge the auxiliary rechargeable energy storage device (C1) until v) the auxiliary voltage (V ｃ ) is the upper limit threshold voltage (V ｓｕｐ－ｍａｘ ), recoupling the energy harvester to the input of the main voltage converter system, and recoupling the first rechargeable energy storage device (BATT1) to the output of the main voltage converter system.

5. The method according to any one of claims 1 to 4, The auxiliary voltage (V ｃ ) is the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ) to the minimum required supply voltage (V ｃｓ ) to a value lower than the predetermined switching voltage V ｓｗ enabling operation of the cold-start voltage converter to recharge the auxiliary rechargeable energy storage device (C1) until a maximum current limit is reached, after which operation of the cold-start voltage converter is disabled and operation of the main voltage converter system is enabled.

6. The method according to any one of claims 1 to 5, The method, characterized in that the main voltage converter system (20) includes a first voltage converter (20a) and a second voltage converter (20b), the step of charging the first rechargeable energy storage device (BATT1) with energy from the energy harvester (70) is performed by operating the first voltage converter (20a), the step of recharging the auxiliary rechargeable energy storage device (C1) with energy from the energy harvester (70) or from the first rechargeable energy storage device (BATT1) is performed by operating the second voltage converter (20b), and the step of recharging the auxiliary rechargeable energy storage device (C1) is performed independently of the step of charging the first rechargeable energy storage device (BATT1).

7. The method according to any one of claims 1 to 5, The main voltage converter system (20) is V ｉｎ >(V ｏｕｔ +Δ), V ｉｎ <(V ｏｕｔ -Δ), V ｉｎ = V ｏｕｔ ±Δ, where V ｉｎ and V ｏｕｔ are the input and output voltages, respectively, of the main voltage converter system, and Δ is an operating parameter of the step-down / step-up voltage converter.

8. The method according to any one of claims 1 to 7, 10. The method of claim 1, wherein the first rechargeable energy storage device (BATT1) has an energy storage capacity that is more than a hundred times, and preferably more than a few thousand times, the energy storage capacity of the auxiliary rechargeable energy storage device (C1).

9. The method according to any one of claims 1 to 8, After charging the first rechargeable energy storage device (BATT1), the first storage parameter (V Ｂａｔｔ１ ) is the upper limit storage value (V Ｂａｔｔ１－ｕｐ ), operating the main voltage converter system (20) to recharge the first rechargeable energy storage device (BATT1) with energy from the energy harvester (70) so as to keep the first rechargeable energy storage device (BATT1) charged, and maintaining the auxiliary rechargeable energy storage device (C1) electrically isolated from the first rechargeable energy storage device (BATT1) during the recharging of the first rechargeable energy storage device (BATT1).

10. A power management integrated circuit for energy harvesting (1), - one or more power input terminals for receiving input power from an energy harvester or another power source; a first storage device terminal (12) connectable with a first rechargeable energy storage device; Integrated on-chip capacitor (C ｉｎｔ ) or an auxiliary rechargeable energy storage device; and a mains voltage converter system (20) configured to receive input power through a first power input terminal (11) of said one or more power input terminals; A controller (40) configured to control the main voltage converter system (20), the controller controlling a supply voltage (V ｓｕｐ ) is the minimum required supply voltage (V ｃｓ ) or greater; and In the cold start voltage converter (30), i) input power is supplied to the auxiliary terminal (9) or to the integrated on-chip capacitor (C ｉｎｔ ii) receiving the input power through the first power input terminal (11) or through the second power input terminal (8) of the one or more power input terminals; iii) when a minimum input voltage is available at the input of the cold-start voltage converter, and when the supply voltage (V ｓｕｐ ) is the minimum required supply voltage (V ｃｓ and a cold start voltage converter (30) configured to commence operation when the cold start voltage converter (30) is lower than the cold start voltage converter (30); The power management integrated circuit comprises: Auxiliary voltage of internal node (V ａｕｘ ) corresponds to the voltage at the auxiliary terminal (9), or the integrated on-chip capacitor (C ｉｎｔ ) to correspond to the voltage of the auxiliary terminal (9) or the integrated on-chip capacitor (C ｉｎｔ ) electrically connected to the internal node (N ａｕｘ ), the internal node (N ａｕｘ ) is the supply voltage at the input of the controller when the auxiliary voltage (V ａｕｘ ) and further electrically connected to the supply input of the controller so as to correspond to the internal node (N ａｕｘ ) is the auxiliary voltage (V ａｕｘ an internal node (N) electrically isolated from the first storage terminal (12) such that the internal node (N) is independent of the voltage at the first storage terminal (12); ａｕｘ )and, coupled to the controller (40) to control the auxiliary voltage (V ａｕｘ ) at the first storage device terminal (12) and Ｂａｔｔ１ a monitoring unit (45) configured to monitor the The controller (40) i) the first storage parameter (V Ｂａｔｔ１ ) is the default upper limit storage value (V Ｂａｔｔ１－ｕｐ activating the main voltage converter system (20) to transmit power to the first storage device terminal (12) via a first power transmission path (P-O1) as long as the voltage Vcc is lower than ii) via a second power transmission path (P-O2) to the auxiliary terminal (9) or to the integrated on-chip capacitor (C ｉｎｔ ) or alternatively to the auxiliary terminals (9) or to the integrated on-chip capacitor (C ｉｎｔ ) to enable operation of the cold-start voltage converter (30) to transfer power to the auxiliary voltage (V ａｕｘ ) a) equal to the target value, or b) the lower threshold voltage (V ｓｕｐ－ｍｉｎ ) and the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ) higher than the upper threshold voltage (V ｓｕｐ－ｍａｘ ) in a voltage range between the target value and the lower threshold voltage (V ｓｕｐ－ｍｉｎ ) is the minimum required supply voltage (V ｃｓ ) higher, power management integrated circuit (1).

11. 11. The power management integrated circuit of claim 10, The main voltage converter system (20) comprises: a first voltage converter (20a) having an output coupled to the first storage device terminal (12) via the first power transmission path (P-O1) and an input connected to the first power input terminal (11); The integrated on-chip capacitor (C ｉｎｔ and a second voltage converter (20b) having an output coupled to the first power input terminal (11), the first storage device terminal (12) or the auxiliary terminal (9), and an input connected to one of the first power input terminal (11), the first storage device terminal (12) or an additional power input terminal.

12. 12. The power management integrated circuit according to claim 10, The main voltage converter system (20) is V ｉｎ >(V ｏｕｔ +Δ), V ｉｎ <(V ｏｕｔ -Δ), V ｉｎ = (V ｏｕｔ ±Δ), wherein V ｉｎ and V ｏｕｔ are the input and output voltages, respectively, of the main voltage converter system (20), and Δ is an operating parameter of the buck / boost converter.

13. A power management integrated circuit (1) according to any one of claims 10 to 12, 1. A power management integrated circuit comprising: a main voltage converter system including an input selection circuit configured to select an input path from a plurality of input paths, the input selection circuit being controlled by the controller and configured to select an input path from a plurality of input paths, such that the main voltage converter system receives input power via a selected input path, the plurality of input paths for the main voltage converter system including at least i) a first input path (P-I1), electrically connecting the first power input terminal (11) to an input of the main voltage converter system (20); and ii) a second input path (P-I2), electrically connecting a further power input terminal (18) to the input of the main voltage converter system (20) or alternatively connecting the first storage device terminal (12) to the input of the main voltage converter system.

14. 14. The power management integrated circuit of claim 13, The controller (40) selects the second input path (P-I2) and supplies a power to the auxiliary terminal (9) or to the integrated on-chip capacitor (C ｉｎｔ ), and the step of selecting the second input path (P-I2) is performed when either of the following two conditions occurs: a) the auxiliary voltage (V ａｕｘ ) is the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ) to a value higher than the predefined critical threshold voltage (V Ｔ－Ｂ ), but V ｃｓ <V Ｔ－Ｂ <V ｓｕｐ－ｍｉｎ And V ｃｓ , V Ｔ－Ｂ and V ｓｕｐ－ｍｉｎ are the minimum required supply voltage, the critical threshold voltage, and the lower threshold voltage, respectively; or b) the auxiliary voltage (V ｃ ) is the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ) and the monitoring unit detects that there is no input power available at the first power input terminal (11).

15. 15. The power management integrated circuit according to claim 10, The controller: iii) the auxiliary voltage (V ｃ ) is the lower limit threshold voltage (V ｓｕｐ－ｍｉｎ ) to the minimum required supply voltage (V ｃｓ ) to a value lower than the default switching voltage V ｓｗ and enabling operation of the cold-start voltage converter to recharge the auxiliary rechargeable energy storage device (C1) until the predetermined switching voltage (V ｓｗ ) is equal to or greater than the target value, or alternatively, the lower threshold voltage (V ｓｕｐ－ｍｉｎ ) or more.

16. A system (100) for energy harvesting, comprising: - an integrated circuit (1) according to any one of claims 10 to 15, an energy harvester (70) coupled to the first power input terminal (11); a first rechargeable energy storage device (BATT1) coupled to the first storage device terminal (12), preferably the first rechargeable energy storage device (BATT1) is a rechargeable battery, a capacitor or a supercapacitor, preferably the first rechargeable energy storage device (BATT1) is a supercapacitor having an energy storage capacity of 1 microfarad to 100 farads; - an auxiliary rechargeable energy storage device (C1) coupled to the auxiliary terminal (9), preferably the auxiliary rechargeable energy storage device being a capacitor having an energy storage capacity of 0.1 nanofarads to 100 microfarads.

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