Method and apparatus for energy harvesting using a cold crank voltage converter

Abstract

The present invention relates to a method for energy harvesting. The method 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 initially charged with a cold start voltage converter, and thereafter 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 maintained equal to a target value suitable for operating the controller, or alternatively maintained within a predefined voltage range corresponding to a power 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, the power management integrated circuit comprising a cold start and a main voltage converter system, and wherein an internal voltage node is maintained at a target value or within a voltage range suitable as a power supply voltage for the controller of the main voltage converter system.

Description

Field of the Invention

[0001] The present invention relates to a method and apparatus for energy harvesting. More particularly, the present invention relates to a method and apparatus for initiating charging of a rechargeable storage device using a power management integrated circuit (PMIC) including a cold start voltage converter and a main voltage converter system.

[0002] Description of the existing technology

[0003] The use of voltage converters to extract energy from energy harvesters and charge rechargeable energy storage devices is well known in the art. The energy stored in the rechargeable energy storage device can then be used, for example, as a power source for an application load. The application load to be powered by the harvested energy can be any type of application, such as a portable device, sensor, external circuit, or wireless transmitter.

[0004] A variety of energy harvesters can be used as energy sources, such as photovoltaic cells (PV), thermoelectric generators (TEG), piezoelectric energy generators and electromagnetic energy sources. Rechargeable storage devices are for example rechargeable batteries such as lithium-ion batteries, supercapacitors or traditional capacitors.

[0005] Typically, integrated circuits for energy harvesting include a main voltage converter system, which includes one or more voltage converters, such as a boost converter, a buck converter, or a buck-boost DC-DC converter. The main voltage converter system is controlled by a controller. The controller requires a power supply voltage, such as 2.5V, 3.3V, or 5V.

[0006] However, PMICs for energy harvesting lack an internal power supply for powering the controller. In conventional PMICs, the controller receives power from a rechargeable energy storage device connected to the PMIC's output terminals. In some known embodiments, the PMIC includes, for example, a buck converter that converts 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 via a switch.

[0007] 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 for starting to harvest energy from the energy harvester without using the main voltage converter system. However, the efficiency of a cold start voltage converter, for example including a charge pump, is low when compared to the efficiency of the main voltage converter system regulated by the controller. Typically, a cold start voltage converter is used until the rechargeable energy storage device is sufficiently charged to provide the supply voltage required to start operating the main voltage converter system. These cold start voltage converters are self-starting voltage converters that are configured to start operating when the input voltage at the input of the cold start voltage converter is above a minimum threshold. A PMIC known with reference number AEM10940 and provided by e-peas SABelgium includes, for example, a cold start voltage converter that starts operating at an input voltage Vin as low as 380 mV and an input power of at least 11 microwatts.

[0008] One of the issues with energy harvesting systems is that when initially starting with a depleted rechargeable storage device, it takes a long time to charge the rechargeable storage device with a cold start voltage converter. Consequently, it also takes a long time for the application load to receive power from the rechargeable storage device and begin operating.

[0009] Especially if the rechargeable storage device is a supercapacitor, which has a voltage of zero volts when fully discharged, the supercapacitor charging time can be very long. Moreover, charging the rechargeable battery to the required charge level to be ready to power the application load for a sufficient period of time can also require a considerable charging time.

[0010] Another issue with PMICs 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 the voltage of the rechargeable energy storage device remains above a threshold voltage corresponding to the supply voltage required by the controller. For example, the rechargeable storage device can initially be charged to 4.5V, but when this voltage subsequently drops below the supply voltage of, for example, 2.5V, the PMIC ceases to operate. This can occur even if the external load only requires, for example, a 1.2V supply voltage. When using capacitors or supercapacitors as storage devices, all of the energy stored in the storage device cannot be used to supply power to the load, and the storage device needs to be oversized to achieve the application's target energy autonomy, which is the period of time during which no energy harvesting occurs.

[0011] Therefore, there is room for improvement in integrated circuits for energy harvesting. SUMMARY OF THE INVENTION

[0013] The object of the present invention is to provide a method and a device for energy harvesting and starting 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 start operating more quickly even in the event that the rechargeable energy storage device is initially completely depleted.

[0014] The invention is defined in the appended independent claim. The dependent claims define advantageous embodiments.

[0015] According to a first aspect of the present invention, a method for energy harvesting using a power management integrated circuit (PMIC) is provided, wherein the power management integrated circuit includes a cold start voltage converter, a main voltage converter system, and a controller for controlling the main voltage converter system. If the power supply voltage V sup equal to or higher than the minimum required supply voltage V CS , then the controller is operational. A main voltage converter system is to be interpreted as a system comprising at least one main voltage converter, such as for example a buck / boost voltage converter.

[0016] The method according to the first aspect of the present invention comprises the following steps:

[0017] Coupling the energy harvester to the input of the main voltage converter system,

[0018] coupling a first rechargeable energy storage device to the output of the main voltage converter system,

[0019] Coupling an energy harvester or another energy source to the input of the cold crank voltage converter,

[0020] coupling an auxiliary rechargeable energy storage device, preferably a capacitor, to the output of the cold-cranking voltage converter,

[0021] coupling an auxiliary rechargeable energy storage device to a power input of the controller to use the auxiliary rechargeable energy storage device as a dedicated voltage source for the controller when charging,

[0022] Monitor the 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 ,

[0023] Charging the auxiliary rechargeable energy storage device by operating the cold start voltage converter until the auxiliary voltage V C has reached the predefined switching voltage V SW , where V SW ≥V CS ,

[0024] If the auxiliary voltage V C has reached the predefined switching voltage V SW , then the operation of the main voltage converter system is enabled and the operation of the cold start voltage converter is disabled,

[0025] As long as the first storage parameter V of the first rechargeable energy storage device Batt1 Lower than the predefined upper limit storage value V Batt1-up , operating the main voltage converter system to charge the first rechargeable energy storage device with energy from the energy harvester, and maintaining the auxiliary rechargeable energy storage device (C1) electrically separated from the first rechargeable energy storage device (BATT1) during charging of the first rechargeable energy storage device (BATT1),

[0026] Maintaining auxiliary voltage V for auxiliary rechargeable energy storage devices C :

[0027] a) equal to the target value, or alternatively,

[0028] b) At the lower threshold voltage (V sup-min ) and is higher than the lower threshold voltage (V sup-min ) upper threshold voltage (V sup-max ),

[0029] And wherein, the target value and the lower threshold voltage (V sup-min ) is equal to or lower than the predefined switching voltage (V SW ) and is higher than the minimum required supply voltage (V CS ), and wherein maintaining the auxiliary voltage equal to a 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 an energy harvester (70).

[0030] In an embodiment, the auxiliary voltage V of the auxiliary rechargeable energy storage device C1 is maintained C The step of equalizing the target value includes: continuously compensating the charge reduction of the auxiliary energy storage device with energy from the energy harvester, so that the auxiliary voltage V C Keep it equal to the target value.

[0031] In an embodiment, the target value is higher than the minimum required supply voltage V CS , and is equal to or lower than the predefined switching voltage V SW .

[0032] In another embodiment, the auxiliary voltage V of the auxiliary rechargeable energy storage device C1 is maintainedC At the lower threshold voltage V sup-min The steps include: if the auxiliary voltage V C has dropped below the lower threshold voltage V sup-min , the auxiliary rechargeable energy storage device is recharged with energy from the energy harvester until the auxiliary voltage V C has reached a voltage higher than the lower threshold voltage V sup-min The upper threshold voltage V sup-max In an embodiment, the lower threshold voltage V sup-min Above the minimum required supply voltage V CS , and is equal to or lower than the predefined switching voltage V SW .

[0033] Advantageously, by using the auxiliary energy storage device as a dedicated voltage source for the controller and maintaining the auxiliary rechargeable energy storage device electrically separate from the first rechargeable energy storage device, the voltage of the first rechargeable energy storage device charged by the main voltage converter system remains independent of the controller's supply voltage. Thus, even if, for example, the voltage of the first rechargeable energy storage device decreases and falls below the minimum required supply voltage V after it has been charged, the controller can still charge the auxiliary energy storage device. CS , the main voltage converter system can also continue to operate thanks to a dedicated auxiliary energy storage device.

[0034] Advantageously, by using the auxiliary energy storage device as the dedicated supply voltage for the controller, the charge capacity of the auxiliary energy storage device can be significantly less 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-cranking voltage converter and reach the supply voltage required for operating the controller is significantly reduced.

[0035] Advantageously, the first rechargeable energy storage device (ie, the primary storage device) is initially charged by the main converter system rather than by the cold start voltage converter. Due to the higher energy efficiency of the main voltage converter system, the first start is accelerated.

[0036] In an embodiment, 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 a device external to the PMIC, such as an external capacitor or another rechargeable energy storage device.

[0037] Typically, the switching threshold V SW is defined so that V CS <V SW ≤V sup-max , and more preferably, V sup-min ≤VSW ≤V sup-max .

[0038] In the embodiment, when the upper limit storage value V is reached Batt1-up , corresponding to the first rechargeable energy storage device being charged.

[0039] In the embodiment, when the upper limit storage value V is reached Batt1-up In other embodiments, the upper storage value V Batt1-up A percentage value corresponding to the first rechargeable energy storage device being charged to a full state of charge of the first rechargeable energy storage device, and wherein the percentage value is a value within a range of 70% to 100%.

[0040] According to a second aspect of the present invention, a power management integrated circuit (PMIC) for energy harvesting is provided. The PMIC for energy harvesting includes: 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 or an integrated on-chip capacitor connectable to an auxiliary rechargeable energy storage device; a main voltage converter system for receiving input power through a first power input terminal of the one or more power input terminals; a controller configured to control the main voltage converter system, and wherein if a power supply voltage V at a power input terminal of the controller is sup equal to or higher than the minimum required supply voltage V CS , the controller is operational; and a cold start voltage converter.

[0041] The cold start voltage converter is configured to i) deliver input power to the auxiliary terminal or the integrated on-chip capacitor, ii) receive input power through the first power input terminal or through a second power input terminal of the one or more power input terminals, and iii) obtain a minimum input voltage at the input of the cold start voltage converter and a power supply voltage V sup Below the minimum required supply voltage V CS Start the operation.

[0042] Typically, a PMIC according to the present invention includes a first power delivery path for delivering power from the main voltage converter system to the first storage device terminal and / or a second power delivery path for delivering power from the main voltage converter system to an auxiliary terminal or an integrated on-chip capacitor.

[0043] The PMIC according to the present invention is characterized in that it includes an auxiliary terminal 9 or an integrated on-chip capacitor C intelectrically connected internal nodes so that the auxiliary voltage V aux corresponds to the voltage at the auxiliary terminal or to the integrated on-chip capacitor C int The voltage of the internal node N aux It is further electrically connected to the power input terminal of the controller so that the power voltage at the input terminal of the controller is equal to the auxiliary voltage V aux Correspondingly, internal node N aux is electrically isolated from the first storage device terminal so that the auxiliary voltage V aux independent of the voltage at the terminals of the first storage device.

[0044] The PMIC further includes a monitoring unit coupled to the controller and configured to monitor an auxiliary voltage V aux and for monitoring a first storage parameter V at a terminal of the first storage device Batt1 , preferably, the first storage parameter V Batt1 corresponding to a voltage sensed at the first storage device terminal.In an embodiment, the monitoring unit comprises a signal comparator for comparing the auxiliary voltage to a predefined supply threshold voltage and comparing the first storage parameter to a predefined storage threshold.

[0045] The controller of the PMIC according to the present invention is configured to operate the main voltage converter system to deliver power to the first storage device terminal via the first power delivery path as long as the first storage parameter is below a predefined upper storage value.

[0046] In an embodiment, the controller is further configured to operate the main voltage converter system to deliver power to the auxiliary terminal or the integrated on-chip capacitor via the second power delivery path to maintain the auxiliary voltage V aux equal to the target value, or alternatively, maintain the auxiliary voltage V aux At the lower threshold voltage V sup-min and the upper threshold voltage V sup-max The voltage range is defined between the lower threshold voltage V sup-min Above the minimum required supply voltage V CS In other embodiments, the controller is configured to enable operation of the cold crank voltage converter to deliver power to the auxiliary terminal or the integrated on-chip capacitor in order to maintain the auxiliary voltage V aux Equal to the target value or within a certain voltage range.

[0047] In an embodiment, the controller of the PMIC according to the present invention is further configured to aux has fallen below the minimum required supply voltage V CS The value increases to the predefined switching voltage VSW Disables the cold start voltage converter operation and enables the main voltage converter system operation, where V SW ≥V CS .

[0048] In an embodiment, if the auxiliary voltage has dropped below the lower threshold voltage V sup-min , the controller operates the main voltage converter system to deliver power to the auxiliary terminal or the integrated on-chip capacitor until the auxiliary voltage has increased to the upper threshold voltage V sup-max Alternatively, the controller operates the main voltage converter to maintain the auxiliary voltage V aux Continues to be equal to the lower threshold voltage V sup-min .

[0049] In one embodiment, a main voltage converter system of a PMIC includes an input selection circuit controlled by a controller. The input selection circuit is configured to select an input path from a plurality of input paths, so that the main voltage converter system receives input power via the selected input path. The plurality of input paths of the main controller include at least a first input path configured to electrically connect a first input terminal to an input of the main voltage converter system.

[0050] In one embodiment, the plurality of input paths of the main voltage converter system includes 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 another input terminal of a PMIC. In another embodiment, the second input path is an internal path of the PMIC for delivering power from the first output terminal to the input of the main voltage converter system.

[0051] In those embodiments including a first input path and a second input path, the controller is further configured to control the main voltage converter system and the input selection circuit to perform the following additional steps: if i) the auxiliary voltage has dropped from a value above a lower threshold voltage to a predefined critical threshold voltage, wherein V CS <V T-B <V sup-min , where 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, alternatively, if ii) the auxiliary voltage has dropped below the lower threshold voltage and the monitoring unit detects that no input power is available at the first input terminal, selecting the second input path, selecting the second power delivery path, and operating the main voltage converter system until the auxiliary voltage has increased to the upper threshold voltage.

[0052] In an embodiment, a main voltage converter system includes a first voltage converter and a second voltage converter. The first voltage converter has an output coupled to a first storage device terminal via a first power delivery path and an input connected to a first power input terminal. The second voltage converter has an output coupled to an integrated on-chip capacitor or an auxiliary terminal via a second power delivery path and an input connected to any of the following: 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.

[0053] In an embodiment, the power management integrated circuit includes a second storage device terminal connectable to a second rechargeable energy storage device, a third power delivery path for delivering power from the main voltage converter system to the second storage device terminal, and wherein the controller is configured to BATT1 The predefined upper storage value V has been reached BATT1-up The main voltage converter system is operated to deliver power from the first power input terminal to the second storage device terminal.

[0054] In an embodiment, the controller of the power management integrated circuit according to the present invention is configured to aux has fallen below the minimum required supply voltage V CS to a value equal to or greater than the minimum required supply voltage V CS The predefined switching voltage V SW Disables the operation of the cold start voltage converter and enables the operation of the main voltage converter system. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] These and further aspects of the invention will be explained in more detail, by way of example, and with reference to the accompanying drawings, in which:

[0056] Figure 1 schematically illustrates an energy harvesting system according to the present disclosure,

[0057] Figure 2 The start-up process of charging a rechargeable energy storage device using the method according to the invention is shown,

[0058] Figure 3a schematically shows an embodiment of a power management integrated circuit according to the invention having auxiliary terminals for connecting an auxiliary rechargeable energy storage device,

[0059] Figure 3b Schematically illustrates an embodiment of a power management integrated circuit according to the present invention, the power management integrated circuit having integrated on-chip capacitors,

[0060] Figure 3c Schematically illustrates an embodiment of a power management integrated circuit in which a cold start voltage converter and a main voltage converter system are used to deliver power to an auxiliary terminal and a storage device terminal, respectively.

[0061] Figure 4 Schematically shows an embodiment of a power management integrated circuit according to the present invention, the power management integrated circuit having a first power input terminal and a second power input terminal,

[0062] Figure 5 An example of an energy harvesting system including a power management integrated circuit according to the present invention is schematically shown.

[0063] Figure 6 A first example of an energy harvesting system is schematically shown, wherein the main voltage converter system of the PMIC comprises a buck / boost voltage converter,

[0064] Figure 7 A second example of an energy harvesting system is schematically shown, wherein the main voltage converter system of the PMIC comprises a buck / boost voltage converter,

[0065] Figure 8 An example of an energy harvesting system is schematically shown, wherein a main voltage converter system of a PMIC includes an input selection circuit, and the PMIC includes an additional input terminal and a second input path connecting the additional input terminal with the input selection circuit,

[0066] Figure 9 An example of an energy harvesting system is schematically shown, wherein 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,

[0067] Figure 10 schematically illustrates an example of a power management integrated circuit comprising a first storage device terminal and a second storage device terminal,

[0068] Figure 11 schematically illustrates an example of an energy harvesting system comprising a first rechargeable energy storage device and a second rechargeable energy storage device,

[0069] Figure 12 A first embodiment of a power management system is schematically illustrated, wherein a main voltage converter system comprises a first voltage converter and a second voltage converter,

[0070] Figure 13A second embodiment of a power management integrated circuit is presented, wherein the voltage converter system includes two voltage converters,

[0071] Figure 14 A third embodiment of a power management integrated circuit is presented, wherein the voltage converter system comprises two voltage converters, and wherein the first voltage converter comprises an input selection circuit,

[0072] Figure 15 A fourth embodiment of a power management integrated circuit is presented, wherein the voltage converter system comprises two voltage converters, and wherein the first output terminal of the PMIC is connected to the input of the first voltage converter.

[0073] The accompanying drawings are neither drawn to scale nor to proportion. Generally, in the accompanying drawings, like parts are represented by like reference numerals. DETAILED DESCRIPTION

[0074] The present disclosure will be described with reference to specific embodiments, which are illustrative of the present disclosure and should not be construed as limiting. Those skilled in the art will appreciate that the present disclosure is not limited to what has been specifically shown and / or described, and that alternative or modified embodiments may be developed based on the overall teachings of the present disclosure. The accompanying drawings described are merely illustrative and non-limiting.

[0075] Use of the verb "comprise" and its conjugations does not exclude the presence of elements other than those stated. Use of the article "a", "an" or "the" preceding an element does not exclude the presence of a plurality of such elements.

[0076] Furthermore, the terms first, second, etc. in the description and in the claims are used to distinguish similar elements and not necessarily to describe a sequence 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 are capable of operation in other sequences than described or illustrated herein.

[0077] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the present disclosure. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" throughout this specification are not necessarily all referring to the same embodiment, but may do so. Furthermore, in one or more embodiments, 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.

[0078] Using 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 utilizes a system for energy harvesting.

[0079] exist Figure 1 , an example of a system 100 for energy harvesting is schematically shown. The system 100 has 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 is coupled to a first power input terminal 11 so as to generate a power supply with an input voltage V in Power is supplied to the PMIC from the energy harvester. The PMIC 1 includes at least a power output terminal 12 coupled to a first rechargeable energy storage device BATT1, enabling power to be output and charged with energy from the energy harvester. In this example, an application load 90 is coupled to the first rechargeable energy storage device BATT1. Figure 1 The PMIC shown further comprises a cold start voltage converter 30 which is used when the main voltage converter system is inoperable (ie when no power is available to power the controller). In fact, if the supply voltage V sup equal to or higher than the minimum required supply voltage V CS , the controller is operational.

[0080] The main voltage converter system 20 should be understood as a system for converting input power received from an energy source, such as an energy harvester, into output power for charging a storage device. Typically, the main voltage converter system includes one or more voltage converters, and specific embodiments of various voltage converter systems are further described below. Examples of voltage converters known in the art are a DC-DC boost converter, a DC-DC buck converter, or a DC-DC buck / boost converter.

[0081] The first rechargeable energy storage device BATT1 is, for example, a rechargeable battery, a capacitor or a supercapacitor.

[0082] The method for energy harvesting according to the present invention comprises the following steps: coupling an energy harvester 70 to the input of a main voltage converter system; coupling a first rechargeable energy storage device BATT1 to the output of the main voltage converter system; coupling the energy harvester 70 or another energy source to the input of a cold start voltage converter; coupling an auxiliary rechargeable energy storage device C1 to the output of the cold start voltage converter; coupling the auxiliary rechargeable energy storage device C1 to the power input of a controller, so that the auxiliary rechargeable energy storage device C1 is used as a voltage source for the controller when charging. By coupling the auxiliary rechargeable energy storage device C1 to the power input of the controller, the power supply voltage V sup Auxiliary voltage V C Corresponding.

[0083] The method according to the invention further comprises the step of monitoring the auxiliary voltage V of the auxiliary rechargeable energy storage device C1. C ; Monitoring the first storage parameter V indicating the charge level of the first rechargeable energy storage device BATT1 Batt1 ; By operating the cold start voltage converter to charge the auxiliary rechargeable energy storage device C1 until the auxiliary voltage V C has reached the predefined switching voltage V SW , where V SW ≥V CS ; If the auxiliary voltage V C has reached the predefined switching voltage V SW , then the operation of the main voltage converter system is enabled and the operation of the cold start voltage converter is disabled; and as long as the parameter V Batt1 Lower than the predefined upper limit storage value V Batt1-up , the first rechargeable energy storage device BATT1 is charged by operating the main voltage converter system.

[0084] The upper limit storage value V Batt1-up has to be interpreted as a threshold value indicating that the first rechargeable energy storage device BATT1 is charged.

[0085] In one embodiment, the first stored parameter V Batt1 Corresponds to the voltage of the first rechargeable energy storage device BATT1. In other embodiments, the first storage parameter V Batt1 Corresponds to the accumulated charge acquired by, for example, a charge counter that counts the accumulated charge during the charging process of the first rechargeable energy storage device BATT1 .

[0086] In an embodiment, the auxiliary voltage V of the auxiliary energy storage device C1 is maintained C= equal to the target value. The target value is, for example, a predefined voltage value corresponding to an appropriate voltage value for operating the controller. In an embodiment, the target value is an appropriate or optimal power supply voltage value for operating the controller. In order to maintain the auxiliary voltage V C Equal to the target value, the main voltage converter system or cold start voltage converter is used to recharge the auxiliary rechargeable energy storage device C1 with energy from the energy harvester 70 .

[0087] Auxiliary voltage V C This maintenance is performed, for example, during charging of the first rechargeable energy storage device BATT1 until the upper storage value V is reached. Batt1-up , and also during any subsequent period.

[0088] In an embodiment, the charge reduction of the auxiliary energy storage device C1 is continuously compensated so that the auxiliary voltage V C Keep it equal to the target value.

[0089] In other embodiments, the main voltage converter system or alternatively a cold start voltage converter is operated to maintain the auxiliary voltage V C is limited to the lower threshold voltage V sup-min and the upper threshold voltage V sup-max voltage range between, and where V CS <V sup-min <V sup-max . Usually, V CS <V SW ≤V sup-max , and more preferably, V sup-min ≤V SW ≤V sup-max In other words, the lower threshold voltage V sup-min Equal to or lower than the predefined switching voltage V SW , and is higher than the minimum required supply voltage V CS .

[0090] In an embodiment, the lower threshold voltage V sup-min and the upper threshold voltage V sup-max The defined voltage range corresponds to an optimum voltage range as a power supply voltage for operating the controller.

[0091] In order to maintain the auxiliary voltage V C In these embodiments within the predefined voltage range, if the auxiliary voltage V C has dropped below the lower threshold voltage V sup-min , the method provides the following steps: recharging the auxiliary rechargeable energy storage device C1 with energy from the energy harvester until the auxiliary voltage V Chas reached a voltage higher than the lower threshold voltage V sup-min The upper threshold voltage V sup-max .

[0092] exist Figure 2 , an example of a process for charging a first rechargeable energy storage device according to the method of the present disclosure is schematically illustrated. The first storage parameter V Batt1 (In this example, the voltage V Batt1 ) and auxiliary voltage V C The variation of is shown as a function of time, showing that the auxiliary voltage of the auxiliary energy storage device C1 is kept at the lower threshold voltage V sup-min and the upper threshold voltage V sup-max Initially, the auxiliary voltage V C Below the lower threshold voltage V sup-min , and in Figure 2 During the start-up period, denoted by “CS-VC” in FIG, the cold start voltage converter operates to charge the auxiliary energy storage device C1 until the switch voltage V SW , where in this example, V sup-min ≤V SW ≤V sup-max After this, the main voltage converter system starts to operate and this phase is Figure 2 In the embodiment, as shown in FIG. Figure 2 As shown, if the auxiliary voltage V C Drops to the lower threshold voltage V sup-min , the main voltage converter system repeatedly stops charging the first rechargeable energy storage device and recharges the auxiliary energy storage device until the upper threshold voltage V sup-max As mentioned above, in Figure 2 In other embodiments not shown, instead of maintaining the auxiliary voltage V C Within a certain voltage range, the auxiliary voltage V C Equal to the target value.

[0093] like Figure 2 As further shown, the main voltage converter system charges the first rechargeable energy storage device BATT1 until an upper storage value V Batt1-up In this example, V Batt1 is the voltage, the upper limit storage value V Batt1-up is greater than the upper threshold voltage V of the auxiliary energy storage device C1 sup-max In fact, since the auxiliary energy storage device is electrically separated from the first rechargeable energy storage device, the voltage V sup and VBatt1 are independent of each other and can therefore have different values ​​at any time.

[0094] In an embodiment, the upper threshold voltage V sup-max may be equal to, for example, a value between 2V and 3V, for example, 2.5V, and the first energy storage device BATT1 may be charged to an upper storage value V equal to, for example, 4.5V. Batt1-up In other embodiments, V Batt1-up Can be lower than V sup-max For example, in an embodiment, V sup-max Can be equal to 5V, V Batt1-up Can be equal to a value lower than 5V.

[0095] In an embodiment, when the first rechargeable energy storage device BATT1 is charged to a value equal to or lower than the upper limit storage value V Batt1-up The battery ready threshold V Batt1-ready When , the energy stored in the first rechargeable energy storage device BATT1 can be used to power the application load.

[0096] In an embodiment, the energy storage capacity of the first rechargeable energy storage device BATT1 is more than a hundred times, and preferably more than a few thousand times, greater than the energy storage capacity of the auxiliary rechargeable energy storage device C1. In some embodiments, the energy storage capacity of BATT1 can even be a million times greater than the storage capacity of C1. In this way, the charging time of 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 ranging from 0.1 nanofarad to 100 microfarad, and the first rechargeable energy storage device can be a supercapacitor with a storage capacity ranging from 1 microfarad to 100 farad.

[0097] As mentioned above, the auxiliary voltage V of the auxiliary rechargeable storage device C1 is maintained C At the lower threshold voltage V sup-min and the upper threshold voltage V sup-max The auxiliary voltage V is monitored during the charging process of the first rechargeable energy storage device BATT1, for example. C And the auxiliary voltage V C Drops to the lower threshold voltage V sup-min The following is performed by recharging the auxiliary energy storage device C1.

[0098] In a preferred embodiment, recharging of the auxiliary energy storage device C1 is performed by operating a main voltage converter.In other embodiments, recharging of the auxiliary energy storage device C1 is performed by operating a cold starting voltage converter.

[0099] In some embodiments, as will be discussed below, instead of using energy from the energy harvester, the auxiliary energy storage device can also be recharged using energy from the first rechargeable energy storage device BATT1. Therefore, there are at least two options for recharging the auxiliary energy storage device using the main voltage converter system: using energy from the energy harvester, or using energy from the first rechargeable energy storage device. The second option is only available when the first energy storage device BATT1 is fully charged and, for example, has reached a value greater than the lower storage limit V Batt1-min This is only possible when the voltage is .

[0100] In an embodiment, if the auxiliary voltage V C falls below the lower threshold voltage V sup-min , then trigger the first option.

[0101] In an embodiment, if the auxiliary voltage V C falls below a predefined critical threshold voltage V T-B , where V CS <V T-B <V sup-min , then the second option is triggered. In fact, if the energy harvester does not provide any power, then if the auxiliary voltage V C falls below the lower threshold voltage V sup-min , then the auxiliary voltage V C will continue to decrease and eventually drop below the critical threshold voltage V T-B , so that the second option is triggered.

[0102] In other embodiments, if the auxiliary voltage V C falls below the lower threshold voltage V sup-min , and if it is detected at that time that the energy harvester does not generate energy or generates insufficient energy, the second option is triggered. The monitoring unit can be used to monitor the availability of energy from the energy harvester by monitoring, for example, the input voltage at the first input terminal or any other parameter indicative of the input power.

[0103] If the auxiliary voltage V C falls below the lower threshold voltage V sup-min , then the first option of recharging the auxiliary rechargeable storage device C1 with energy from the energy harvester is performed by 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 operating the main voltage converter system to recharge the auxiliary rechargeable storage device C1 until the auxiliary voltage V C The upper threshold voltage Vsup-max Thereafter, the output of the main voltage converter system is decoupled from the auxiliary rechargeable energy storage device C1 and coupled to the first rechargeable energy storage device BATT1 .

[0104] If the auxiliary voltage V C falls below a predefined critical threshold voltage V T-B , where V CS <V T-B <V sup-min , or if it is monitored that the energy harvester is not generating energy, the second option of recharging the auxiliary rechargeable energy storage device C1 with energy from the first rechargeable energy storage device BATT1 is performed by the following steps: disconnecting the energy harvester from the input of the main voltage converter system, disconnecting the first rechargeable energy storage device BATT1 from the output of the main voltage converter system, coupling the first rechargeable energy storage device 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 device C1, and operating the main voltage converter system to recharge the auxiliary rechargeable energy storage device C1 until the auxiliary voltage V C The upper threshold voltage V sup-max Thereafter, the energy harvester is recoupled to the input of the main voltage converter system, and the first rechargeable energy storage device BATT1 is recoupled to the output of the main voltage converter system.

[0105] In embodiments where the main voltage converter system 20 includes a buck / boost voltage converter, the buck / boost voltage converter is configured to provide a voltage between V in >(V out +Δ) in buck mode, at V in <(V out -Δ) in boost mode, and V in =V out ±Δ when operating in buck-boost mode, where V in and V out are the input voltage and output voltage of the main voltage converter system, respectively, and Δ is an operating parameter of the buck / boost voltage converter.

[0106] If the energy harvester is no longer operational, for example, and the first stored parameter V Batt1 For example, if it is lower than the predefined lower storage value V Batt1-min , then there may be a situation where, when the auxiliary voltage V C has dropped to the lower threshold voltage V sup-min , no power is available to recharge the auxiliary energy storage device, and therefore the auxiliary voltage VC may further decrease below the minimum required supply voltage V for operating the controller CS As mentioned above, the minimum required supply voltage V CS is lower than the lower threshold voltage V sup-min threshold voltage.

[0107] The main voltage converter system is operated to maintain the auxiliary voltage V C Equal to the target value or used to maintain the auxiliary voltage V C In an embodiment within a certain voltage range, and if the auxiliary voltage V C has dropped below the minimum required supply voltage V CS In the case of the cold start voltage converter becoming operational to recharge the auxiliary rechargeable energy storage device C1 until the predefined switching voltage V SW Thereafter, the operation of the cold start voltage converter is disabled and the operation of the main voltage converter system is enabled. Figure 2 Schematic showing the minimum required supply voltage V CS .

[0108] In some embodiments, main voltage converter system 20 includes a first voltage converter 20a and a second voltage converter 20b. In these embodiments, charging the first rechargeable energy storage device BATT1 with energy from energy harvester 70 is performed by operating first voltage converter 20a, and recharging the auxiliary rechargeable energy storage device C1 is performed by operating second voltage converter 20b with energy from energy harvester 70 or with energy from the first rechargeable energy storage device BATT1. Recharging of auxiliary rechargeable energy storage device C1 is performed independently of charging of the first rechargeable energy storage device BATT1, i.e., control of charging of the first auxiliary device is not affected by control of charging of the auxiliary rechargeable storage device, and vice versa.

[0109] In embodiments where the voltage converter used to recharge the auxiliary rechargeable energy storage device C1 is different from the voltage converter used to charge the first rechargeable energy storage device, charging of the first rechargeable energy storage device BATT1 can occur simultaneously with charging of the auxiliary rechargeable energy storage device C1. According to a second aspect of the present invention, there is provided a power management integrated circuit for energy harvesting that allows execution of the method for energy harvesting discussed above.

[0110] An integrated circuit for energy harvesting according to the invention must be interpreted as a microchip comprising an integrated circuit and a plurality of input pins and output pins (also called terminals). The microchip may have, for example, 16 to 32 terminals. Typically, the microchip has a compact package resulting in a square or rectangular footprint with a side length between 1 mm and 5 mm. Various examples of the PMIC 1 according to the invention are respectively Figure 3a 、 Figure 3b 、 Figure 3c 、 Figure 4 、 Figure 10 as well as Figures 12 to 15 An example of an energy harvester system 100 including a PMIC 1 is shown in FIG. Figures 5 to 9 and Figure 11 These examples are discussed further below.

[0111] 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 that allows charge to be transferred from the PMIC to the auxiliary rechargeable energy storage device and vice versa. In other embodiments, such as Figure 3b As shown, instead of an auxiliary terminal that can be connected to an external auxiliary rechargeable energy storage device, the PMIC includes an integrated on-chip capacitor C int .

[0112] 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 outputting power to the first rechargeable energy storage device and inputting power from the first rechargeable energy storage device to the PMIC.

[0113] 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 configured to i) deliver the input power to the auxiliary terminal 9 or the integrated on-chip capacitor C int, ii) receiving 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, and iii) obtaining a minimum input voltage at the input of the cold start voltage converter and the power supply voltage V sup Below the minimum required supply voltage V CS Start the operation.

[0114] exist Figure 3a and Figure 3b In the embodiment shown, both the main voltage converter system and the cold start voltage converter receive input power through the same input terminal 11. In other embodiments, such as Figure 4 As shown, the main voltage converter system and the cold start voltage converter receive input power through different input terminals indicated by reference numerals 11 and 8 .

[0115] As discussed above, if the power supply voltage V sup equal to or higher than the minimum required supply voltage V CS , the controller 40 is operational.

[0116] In an embodiment, Figure 3a and Figure 4 As schematically shown in FIG, the main voltage converter system is configured to output power through a plurality of power transmission paths, and wherein the plurality of power transmission paths include at least a first power transmission path P-O1 and a second power transmission path P-O2, which are configured to electrically connect the output end of the main voltage converter system to the first storage device terminal 12 and the auxiliary terminal 9, respectively.

[0117] In some embodiments where the main voltage converter system comprises only a single voltage converter, such as e.g. Figures 6 to 9 As shown, the main voltage converter system 20 includes an output selection circuit 21, which is controlled by a controller and configured to select a power transmission path from a plurality of 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 the first storage device terminal or the auxiliary terminal.

[0118] In such Figure 3b In the embodiment shown, power can be delivered from the main voltage converter system to the integrated on-chip capacitor C via the second power delivery path P-O2. int .

[0119] In an embodiment where the main voltage converter system 20 includes an output selection circuit 21, a circuit is provided as follows: Figure 3a 、 Figure 3b and Figure 4One or more switches S1, S2 are schematically shown for selecting a power output path. If switch S1 is open and switch S2 is closed, power can be delivered from the main voltage converter system to the first storage device terminal 12, and if switch S1 is closed and switch S2 is open, power can be delivered from the main voltage converter system to the auxiliary terminal 9.

[0120] If a specific power delivery path is selected by the output selection circuit 21 , this means, by definition, that the other remaining power delivery paths are deselected, since only one power delivery path can be selected at a time.

[0121] In an embodiment, such as Figure 3c As schematically shown, the main voltage converter system 20 is used to deliver power to the first storage device terminal 12 via the first power delivery path P-O1, while the cold start voltage converter 30 is used to deliver power to the auxiliary terminal (9) or the integrated on-chip capacitor C int , in order to maintain the auxiliary voltage V aux Equal to or higher than the lower threshold voltage V sup-min Therefore, in these embodiments, the cold start voltage converter is not only used to initially supply voltage to the internal node N aux Charging is performed until the auxiliary voltage V aux From below the minimum required supply voltage V CS The value increases to the predefined switching voltage V SW , as discussed above, but also for internal nodes N aux Recharge to maintain V aux Equal to or higher than the lower threshold voltage V sup-min .

[0122] In other embodiments according to the present invention, Figures 13 to 15 As shown, the main voltage converter system includes two voltage converters: a first voltage converter 20a having an output coupled to a first power delivery path P-O1, and a second voltage converter 20b having an output coupled to a second power delivery path P-O2. Therefore, in these embodiments having two output paths and two associated voltage converters, an output path selection circuit is not mandatory. However, in PMIC embodiments having, for example, a third power delivery path P-O3, as shown Figure 12 As illustrated, the output path selection circuit may select the first voltage converter 20a to output power via the first output path P-O1 or via the third output path P-O3.

[0123] like Figures 3a to 4 As further schematically shown, the PMIC includes an internal node N aux Internal node Naux with auxiliary terminal 9 or integrated on-chip capacitor C int electrically connected so that 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 voltage of the internal node N aux It is further electrically connected to the power input terminal of the controller so that the power voltage at the input terminal of the controller is equal to the auxiliary voltage V aux Corresponding. Figures 3a to 15 As shown, the internal node N aux is a voltage node electrically isolated from the first storage device terminal 12, so that the auxiliary voltage V aux Independent of the voltage at the first storage device terminal 12 .

[0124] As mentioned above and as Figure 3a and Figure 3b As shown, the second power transfer path P-O2 connects the output of the main voltage converter system to the auxiliary terminal. Figure 3b In the embodiment shown, the internal node N aux The auxiliary voltage is connected to the integrated on-chip capacitor C int The voltage corresponds to .

[0125] The monitoring unit 45 coupled to the controller 40 is configured to monitor the voltage V aux and for monitoring a first storage parameter V at the first storage device terminal 12 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 It can be an accumulated charge.

[0126] The controller is configured so that as long as the first stored parameter V Batt1 Lower than the predefined upper limit storage value V BATT1-up , it delivers power to the first storage device terminal 12 and to the auxiliary terminal 9 or the integrated on-chip capacitor C int Delivers power to maintain the auxiliary voltage V aux equal to the target value, or alternatively, maintain the auxiliary voltage V aux At the lower threshold voltage V sup-min and the upper threshold voltage V sup-max The target value, or alternatively the lower threshold voltage V sup-min , is defined as being above the minimum required supply voltage V CS The target value is, for example, a voltage suitable for operating the controller.

[0127] In embodiments, the controller is further configured to enable operation of the cold start voltage converter to recharge the auxiliary rechargeable energy storage device C1. In these embodiments, if the auxiliary voltage V C has been reduced from the lower threshold voltage V sup-min drops below the minimum required supply voltage V CS The controller enables the operation of the cold start voltage converter to recharge the auxiliary rechargeable energy storage device C1 until the predefined switching voltage V SW Thereafter, the operation of the cold start voltage converter is disabled and the operation of the main voltage converter system is enabled.

[0128] The controller maintains V aux In the embodiment where the switching voltage V is equal to the target value, the predefined switching voltage V SW equal to or above the target value.

[0129] The controller maintains V aux At the lower threshold voltage V sup-min and the upper threshold voltage V sup-max In embodiments where the voltage range is between SW Equal to or higher than the lower threshold voltage V sup-min .

[0130] For embodiments where the main voltage converter system comprises two dedicated voltage converters, such as e.g. Figures 13 to 15 As shown, power delivery to the first storage device terminal can be performed in parallel and independently of power delivery to the auxiliary terminal. Figure 6 As shown, where the output of the voltage converter is switched using the output selection circuit 21 , charge transfer to the first storage device terminal and the auxiliary terminal cannot be performed simultaneously.

[0131] The controller 40 is further configured to aux has fallen below the minimum required supply voltage V CS The value increases to equal to or higher than the voltage V CS The predefined switching voltage V SW , disables the operation of the cold start voltage converter 30 and enables the operation of the main voltage converter system. Figure 2 Schematically illustrated in FIG, wherein a switch from a cold start voltage converter operation period CS-VC to a main voltage converter system period M-VC is illustrated.

[0132] The controller 40 is further configured to aux and V BATT1The monitoring of the actual value and the comparison of the predefined threshold value control the power transmission via the first power output path P-O1 and the second power output path P-O2. More specifically, the main voltage converter system 20 is configured to perform the following steps:

[0133] a) If V sup-min ≤V aux And if V BATT1 <V BATT1-up , where V BATT1-up It is V BATT1 The predefined upper limit storage value and V sup-min It is V aux , the first path P-O1 is selected and the main voltage converter system is operated to deliver power from the first power input terminal 11 to the first storage device terminal 12, and wherein, if V BATT1 The predefined upper storage value V has been reached BATT1-up , then stop supplying power to the first storage device terminal 12, and

[0134] b) If V aux has risen above the lower threshold V sup-min The value drops below the lower threshold voltage V sup-min The value of the auxiliary voltage V aux has increased to the upper threshold voltage V sup-max , where V sup-max >V sup-min In an alternative embodiment, as discussed above, the controller is configured to operate the main voltage converter so as to continuously maintain the auxiliary voltage V C Equal to the target value.

[0135] As discussed above, by monitoring the voltage V aux and controls the main voltage converter system, the power supply voltage V of the controller 40 sup Maintain at value V sup-min , or maintain at the threshold voltage V sup-min and V sup-max The voltage of the first output terminal also keeps the same as the power supply voltage V sup For example, if V Batt1 is voltage, the upper limit storage value V BATT1-up can be equal to 4.5V, and the upper threshold voltage V sup-max It may be equal to, for example, 2.5 V or any other suitable value.

[0136] The use of the term "controller" has to be interpreted in the broadest sense as electronic digital circuits typically comprising combinational logic.A controller controlling the main voltage converter system is configured for controlling, for example, power switches of the main voltage converter system.

[0137] In a particular 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 particular embodiment, the second power delivery path P-O2 is configured to electrically connect the output of the main voltage converter system to the integrated on-chip capacitor. In this embodiment, the internal node N aux The device is also electrically connected to at least i) an integrated on-chip capacitor, ii) a power input terminal of a controller, and iii) an output terminal of a cold crank voltage converter.

[0138] In an embodiment, the monitoring unit 45 comprises a device for Batt1 and V aux A signal comparator is used to compare the signal with a predefined threshold. The signal comparator can be an analog signal comparator or a digital signal comparator known in the art. For an embodiment using a digital signal comparator, an ADC (analog-to-digital converter) is first used to convert the general analog signal V Batt1 and V aux The predefined threshold value may be a value stored locally in the controller, or the predefined threshold value may be generated by a reference voltage generator, or a voltage configurator external to the PMIC may be used and the threshold value may be delivered through a configuration terminal or connector.

[0139] The cold-start voltage converter 30 is configured to obtain a minimum input voltage at the input terminal of the cold-start voltage converter and V sup <V CS The operation starts when the main voltage converter system is inoperable, ie when it is in the so-called reset mode.

[0140] 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 then provides a supply voltage V sup The voltage V aux The oscillator is started by an enable signal generated when the input voltage of the cold start voltage converter is higher than the minimum input voltage. The minimum voltage is, for example, a reference voltage generated by a reference voltage generator. sup has reached the switching voltage V SW , the oscillator is switched off and thus the cold start voltage converter is switched off, and subsequently the main voltage converter system is switched on.

[0141] exist Figure 5, an example of an energy harvesting system is schematically shown, which includes a PMIC 1, 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. In this example, an application load 90 is connected to the first rechargeable energy storage device BATT1.

[0142] like Figure 5 As further illustrated, the main voltage converter system 20 may use an inductor 25 that is typically external to the PMIC 1 and that may be coupled to the PMIC via, for example, two dedicated terminals 14 , 15 or via any other suitable coupling means.

[0143] In a preferred embodiment, the main voltage converter system 20 includes a DC-DC buck / boost voltage converter, such as Figure 6 and Figure 7 As shown, the DC-DC buck / boost voltage converter can operate in boost mode, buck mode, or buck-boost mode, depending on the input and output voltages of the main voltage converter system. When the main voltage converter system input voltage is less than the voltage converter output voltage, the buck / boost voltage converter will operate in boost mode. On the other hand, if the input voltage is higher than the output voltage, the buck / boost voltage converter will operate in buck mode. If the input and output voltages are approximately the same, the converter will operate in buck / boost mode. The output voltage of the main voltage converter system considered for determining the buck / boost voltage converter's operating mode will depend on the selected power delivery path. For example, when the first power delivery path P-O1 or the second power delivery path P-O2 is selected, the output voltages considered correspond 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 buck / boost converter's operating mode corresponds to the voltage at the input terminal of the selected input path.

[0144] The main voltage converter system 20 includes a plurality of power switches, such as Figure 6 The illustrated embodiment includes an output selection circuit 21 having switches S1 and S2, and a buck / boost converter 20a includes switches S3A, S3B, S4A, and S4B. Figure 6 The embodiment shown, Figure 7 The embodiment of the main voltage converter system shown includes fewer switches. Figure 7 In the embodiment of FIG. 5 , some switches of the buck / boost voltage converter 20 a are also used as selection switches of the output selection circuit. Figure 6The function of switch S3B used during nominal operation of the buck / boost voltage converter is Figure 7 The switching operation is performed by the switch S2, which simultaneously performs the function of selecting the first power delivery path PO-1 when the switch S1 remains open. Similarly, if the switch S2 remains open when the second power delivery path PO-2 is selected, the switch S1 is used during the nominal operation of the buck / boost voltage converter instead of Figure 6 In other words, the switches used for the output selection circuit can be shared with the switches used for the nominal operation of the buck / boost voltage converter. Figure 9 The illustrated embodiment of the voltage converter system 20 includes an output selection circuit 21 having switches S1 and S2, an input selection circuit 22 having switches S5 and S6, and a buck / boost converter having switches S3A, S3B, S4A, and S4B. Figure 8 In the embodiment, Figure 9 Compared to the embodiment of FIG. 1 , the number of switches is reduced because both the output selection circuit and the input selection circuit share switches with the buck / boost voltage converter.

[0145] A switch must be interpreted as an electronic switch 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.

[0146] In order to operate in boost mode e.g. Figure 7 The buck / boost voltage converter embodiment shown in FIG is used to charge a first storage device with energy from an energy harvester, with switch S1 remaining open, switch S4B remaining closed, and switch S4A remaining open during charging of the first energy storage device BATT1. The boost mode begins with a magnetic energy charging phase of inductor 25, in which switch S3A is closed and switch S2 is open, followed by a magnetic energy discharging phase, in which switch S3A is open and switch S2 is closed. As is known in the art, power is delivered from the energy harvester to the first rechargeable energy storage device BATT1 in boost mode by repeatedly controlling switches S3A and S2.

[0147] To operate in buck mode Figure 7, a buck / boost voltage converter is used to charge the first energy storage device BATT1, with switch S2 remaining closed, and switches S3A and S1 remaining open during the charging of the first energy storage device BATT1. Buck mode begins with a magnetic energy charging phase of inductor 25, in which switch S4A is open and switch S4B is closed, followed by a magnetic energy discharging phase, in which switch S4A is closed and switch S4B is open. As is known in the art, power is delivered from the energy harvester to the first rechargeable energy storage device BATT1 in buck mode by repeatedly controlling switches S4A and S4B.

[0148] As mentioned above and as Figure 7 The example shown shows that switch S2 not only serves as a standard switch required for operating the DC / DC buck / boost voltage conversion, but also forms part of the output selection circuit 21. In fact, by opening switch S2 and closing switch S1, the second power delivery path P-O2 is selected. In this way, the number of electronic switches used to perform both the nominal operating function of the voltage converter and the power delivery path selection function is limited. However, using, for example, Figure 9 and Figure 6 The illustrated dedicated switches for the input and / or output selection circuits also have the advantage that there is less parasitic capacitance at the node switched from the inductor 25 and therefore less power loss.

[0149] In a preferred embodiment, if Figure 10 As shown, the power management integrated circuit includes a second storage device terminal 13 connectable to a second rechargeable energy storage device BATT2, and the plurality of power delivery paths includes a third power delivery path P-O3 configured to electrically connect the output of the main voltage converter system 20 to the second storage device terminal 13. Figure 10 The switch S7 shown selects the third power delivery path.

[0150] Typically, the second rechargeable energy storage device BATT2 has a second storage parameter V BATT2 ,like Figure 11 Schematically shown, the second storage parameter is indicative of the charge level of the second rechargeable energy storage device BATT2 .

[0151] Preferably, the controller 40 is configured to store the first parameter V BATT1 The predefined upper storage value V has been reached BATT1-up 0 , the third path P-03 is selected and the main voltage converter system 20 is operated to deliver power from the first power input terminal 11 to the second storage device terminal 13. Advantageously, when the first rechargeable energy storage device has reached the upper storage value V BATT1-upBy charging the second rechargeable energy storage device BATT2 connected to the second storage device terminal 13 at a defined charge level, additional energy can be stored and used later, for example, when the energy harvester is not supplying any power. The second energy storage device can have, for example, a large energy storage capacity and can therefore be used as a large energy storage.

[0152] In an embodiment, such as Figure 8 、 Figure 9 and Figure 11 As shown, the main voltage converter system 20 includes an input selection circuit 22, which is controlled by a controller 40 and is configured to select an input path from a plurality of input paths so as to receive input power via the selected input path. In this way, the main voltage converter system can receive input power from various energy sources.

[0153] In an embodiment of an energy harvesting system, such as Figure 8 and Figure 11 As shown, 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, which are configured to electrically connect the first power input terminal 11 and the further power input terminal 18, respectively, to the input of the main voltage converter system 20. The first BATT1 or second BATT2 rechargeable energy storage device can be electrically connected to the further power input terminal 18, for example, via a connection external to the 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 is no longer supplying any power. In this way, the application load 90 can continue to operate even when the energy harvester is not supplying any power.

[0154] In an embodiment, Figure 8 As shown, the PMIC comprises a further power input terminal 18 and a second input path P-I2, which electrically connects the further input terminal 18 to the input of the main voltage converter system 20. In this way, when the auxiliary voltage V aux has dropped below the lower threshold voltage V sup-minWhen the energy harvester does not supply energy or does not supply sufficient energy, the main voltage converter system 20 can transfer charge from the additional power input terminal 18 to the auxiliary output terminal 9 by selecting the second input path P-I2. In an embodiment, an additional energy harvester or power source can be connected to the additional power terminal 18. In other embodiments, the first output terminal 12 can be electrically connected to the additional input terminal 18 to enable charge to be transferred from the first output terminal to which the first rechargeable energy storage device BATT1 is connected, for example, to the additional input terminal 18.

[0155] exist Figure 9 In the embodiment shown, the second input path PI-2 is an internal path of the PMIC 1 that connects the first output terminal 12 to the input of the main voltage converter system 20. As described above, when the auxiliary voltage V aux has dropped below the lower threshold voltage V sup-min When the energy harvester does not supply energy or does not supply sufficient energy, the main voltage converter system 20 can transfer charge from the first output terminal 12 to the auxiliary output terminal 9 by selecting the second input path P-I2.

[0156] In an embodiment including the additional power input terminal 18 described above, the controller 40 is further configured to select the second input path P-I2, select the second power delivery path P-O2, and operate the main voltage converter system 20 until the auxiliary voltage V aux Has increased to the upper threshold V sup-max In an embodiment, if V aux has risen above the lower threshold voltage V sup-min The value drops to the predefined critical threshold voltage V T-B , where V CS <V T-B <V sup-min , then select the second input path and the second output path. Figure 2 Schematically shows the predefined critical threshold voltage V T-B In an alternative embodiment, if the auxiliary voltage V C has dropped below the lower threshold voltage V sup-min , and if the monitoring unit detects that no input power is available at the first input terminal at the same time, selecting the second input path and the second output path.

[0157] exist Figure 11In the embodiment shown, the energy harvesting system further includes a primary battery 80 connected to the additional input terminal 16 of the PMIC 1. A switch SW allows selection 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 operating and the storage device is depleted.

[0158] Usually, such as Figure 11 As shown, the input of the main voltage converter system 20 is also connected to a further input terminal 17 which is coupled to an external capacitor C2. This external capacitor C2 allows stabilization of the input voltage of the main voltage converter system.

[0159] As discussed above, the cold cranking voltage converter 30 receives input power from the energy harvester 70 , or from another energy source such as, for example, a primary battery, another storage device, or an auxiliary power source such as a USB connection. Figure 11 This is shown in FIG, where an auxiliary energy source 75 is coupled to a dedicated input terminal 8 of the PMIC to supply input power to the cold start voltage converter. Advantageously, such an auxiliary power supply also allows testing of the PMIC without having to wait for energy harvesting to occur.

[0160] In e.g. Figure 6 and Figure 7 In the illustrated embodiment, the main voltage converter system 20 includes a single voltage converter 20a for delivering power to 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 a specific number of voltage converters. For example, as discussed above, in Figures 12 to 15 , an embodiment of a main voltage converter system 20 including a first voltage converter 20a and a second voltage converter 20b is shown. In these examples, the first voltage converter is configured to deliver power to the first output terminal 12 or the second output terminal 13, and the second voltage converter is configured to deliver 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 a first and second inductors, respectively. Advantageously, when using the first and second voltage converters, both voltage converters can be used simultaneously.

[0161] In an embodiment of an energy harvesting system using capacitors and / or supercapacitors, the energy storage capacity of the first rechargeable energy storage device BATT1 is between 1 microfarad and 100 farads, and the energy storage capacity of the auxiliary rechargeable energy storage device C1 is between 0.1 nanofarad and 100 microfarads.

Claims

1. A method for energy harvesting using a power management integrated circuit, the 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, and wherein: If the power supply voltage at the power input terminal of the controller (V sup ) is equal to or higher than the minimum required supply voltage (V CS ), the controller is operable, and the method comprises the following steps: coupling an energy harvester (70) to the input of the main voltage converter system, coupling a first rechargeable energy storage device (BATT1) to the output of the main voltage converter system, coupling the energy harvester (70) or another energy source to the input of the cold start voltage converter, coupling an auxiliary rechargeable energy storage device (C1) to the output of the cold-cranking voltage converter, coupling the auxiliary rechargeable energy storage device (C1) to a power input of the controller to use the auxiliary rechargeable energy storage device (C1) as a voltage source for the controller when charging, Monitor the auxiliary voltage (V C ), and monitoring a first storage parameter (V Batt1 ), Charging the auxiliary rechargeable energy storage device (C1) by operating the cold starting voltage converter until the auxiliary voltage (V C ) has reached a value equal to or higher than the minimum required supply voltage (V CS ) of the predefined switching voltage (V SW ), If the auxiliary voltage (V C ) has reached the predefined switching voltage (V SW ), then enabling the operation of the main voltage converter system and disabling the operation of the cold start voltage converter, As long as the first storage parameter (V Batt1 ) is lower than the predefined upper 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), wherein the upper storage value (V Batt1-up ), which, when reached, corresponds to the first rechargeable energy storage device being charged, such that the charged rechargeable energy storage device can be used to provide power to an application load, and when the first rechargeable energy storage device (BATT1) is charged to the upper storage value (V Batt1-up ), maintaining the auxiliary rechargeable energy storage device (C1) electrically separated from the first rechargeable energy storage device (BATT1) so that the auxiliary voltage (V C ) remains independent of the voltage at the first rechargeable energy storage device (BATT1), After the first rechargeable energy storage device (BATT1) is charged to the upper storage value (V Batt1-up ) during which the auxiliary voltage (V C ): a) is equal to a target value, and wherein the target value is a predefined voltage value corresponding to an appropriate voltage value for operating the controller (40), or alternatively, b) At the lower threshold voltage (V sup-min ) and is higher than the lower threshold voltage (V sup-min ) upper threshold voltage (V sup-max ), wherein the voltage range corresponds to an optimal voltage range as a power supply voltage for operating the controller, And wherein, the target value and the lower threshold voltage (V sup-min ) is equal to or lower than the predefined switching voltage (V SW ) and is higher than the minimum required supply voltage (V CS ), and wherein said maintaining said auxiliary voltage equal to said target value or within said voltage range comprises: operating said main voltage converter system, or alternatively operating said cold start voltage converter, to recharge said auxiliary rechargeable energy storage device (C1) with energy from said energy harvester (70).

2. The method according to claim 1, in, The auxiliary voltage (V C ) equal to the target value include: Continuously compensates for the charge reduction of the auxiliary rechargeable energy storage device (C1) so that the auxiliary voltage (V C ) remains equal to the target value, And wherein, the auxiliary voltage (V C ) is at the lower threshold voltage (V sup-min ) and the upper threshold (V sup-max ) include: If the auxiliary voltage (V C ) has dropped below the lower threshold voltage (V sup-min ), the auxiliary rechargeable energy storage device (C1) is recharged until the auxiliary voltage (V C ) has reached the upper threshold voltage (V sup-max ).

3. The method according to claim 1, wherein If the auxiliary voltage (V C ) drops below the lower threshold voltage (V sup-min ), the main voltage converter system is operated to recharge the auxiliary rechargeable energy storage device (C1) with energy from the energy harvester (70), and wherein the recharging comprises the following steps: i) decoupling 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 operating the main voltage converter system to recharge the auxiliary rechargeable energy storage device (C1) until the auxiliary voltage (V C ) has reached the upper threshold voltage (V sup-max ), iii) If the auxiliary voltage (V C ) has reached the upper threshold voltage (V sup-max ), the output end of the main voltage converter system is disconnected from the auxiliary rechargeable energy storage device (C1), and the output end of the main voltage converter system is coupled to the first rechargeable energy storage device (BATT1).

4. The method according to claim 1, wherein recharging the auxiliary rechargeable energy storage device (C1) with energy from the first rechargeable energy storage device (BATT1) when: a) The first storage parameter (V Batt1 ) is higher than the predefined lower storage value (V Batt1-min ),as well as b) The auxiliary voltage (V C ) drops below the lower threshold voltage (V sup-min ) and the energy harvester does not provide energy, or the auxiliary voltage (V C ) from above the lower threshold voltage (V sup-min ) drops below a predefined critical threshold voltage (V T-B ), where the minimum required supply voltage (V CS )<the predefined critical threshold voltage (V T-B )<the lower threshold voltage (V sup-min ), And wherein, the recharging comprises the following steps: i) decoupling 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 operating the main voltage converter system to recharge the auxiliary rechargeable energy storage device (C1) until the auxiliary voltage (V C ) has reached the upper threshold voltage (V sup-max ), v) If the auxiliary voltage (V C ) has reached the upper threshold voltage (V sup-max ), the energy harvester is recoupled to the input of the main voltage converter system, and the first rechargeable energy storage device (BATT1) is recoupled to the output of the main voltage converter system.

5. The method according to claim 3, wherein recharging the auxiliary rechargeable energy storage device (C1) with energy from the first rechargeable energy storage device (BATT1) when: a) The first storage parameter (V Batt1 ) is higher than the predefined lower storage value (V Batt1-min ),as well as b) The auxiliary voltage (V C ) drops below the lower threshold voltage (V sup-min ) and the energy harvester does not provide energy, or the auxiliary voltage (V C ) from above the lower threshold voltage (V sup-min ) drops below a predefined critical threshold voltage (V T-B ), where the minimum required supply voltage (V CS ) predefined critical threshold voltage ( <V T-B )<the lower threshold voltage (V sup-min ), And wherein, the recharging comprises the following steps: i) decoupling 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 operating the main voltage converter system to recharge the auxiliary rechargeable energy storage device (C1) until the auxiliary voltage (V C ) has reached the upper threshold voltage (V sup-max ), v) If the auxiliary voltage (V C ) has reached the upper threshold voltage (V sup-max ), the energy harvester is recoupled to the input of the main voltage converter system, and the first rechargeable energy storage device (BATT1) is recoupled to the output of the main voltage converter system.

6. The method according to any one of claims 1 to 5, further comprising the steps of: If the auxiliary voltage (V C ) has been reduced from the lower threshold voltage (V sup-min ) drops below the minimum required supply voltage (V CS ), the operation of the cold start voltage converter is enabled to recharge the auxiliary rechargeable energy storage device (C1) until the predefined switching voltage (V SW ), and then disabling operation of the cold start voltage converter and enabling operation of the main voltage converter system.

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

8. The method according to any one of claims 1 to 5, wherein The main voltage converter system (20) includes a buck / boost voltage converter configured to in >(V out +Δ) in buck mode, at V in <(V out -Δ) in boost mode, and V in =V out ±Δ when operating in buck-boost mode, where V in and V out are the input voltage and output voltage of the main voltage converter system, respectively, and Δ is an operating parameter of the buck / boost voltage converter.

9. The method according to any one of claims 1 to 5, wherein The energy storage capacity of the first rechargeable energy storage device (BATT1) is more than one hundred times greater than the energy storage capacity of the auxiliary rechargeable energy storage device (C1).

10. The method according to any one of claims 1 to 5, further comprising the following steps: If, after charging the first rechargeable energy storage device (BATT1), the first storage parameter (V Batt1 ) drops below the upper 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 maintain the charging of the first rechargeable energy storage device (BATT1) and to maintain the electrical separation of the auxiliary rechargeable energy storage device (C1) from the first rechargeable energy storage device (BATT1) during the recharging of the first rechargeable energy storage device (BATT1).

11. The method according to claim 1, wherein The auxiliary rechargeable energy storage device (C1) is a capacitor.

12. The method according to claim 9, wherein The energy storage capacity of the first rechargeable energy storage device (BATT1) is thousands of times greater than the energy storage capacity of the auxiliary rechargeable energy storage device (C1).

13. A power management integrated circuit (1) for energy harvesting, the power management integrated circuit comprising 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, Integrated on-chip capacitors (C int ) or an auxiliary terminal (9) capable of being connected to an auxiliary rechargeable energy storage device, a main voltage converter system (20) configured to receive 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 wherein, If the power supply voltage (V sup ) is equal to or higher than the minimum required supply voltage (V CS ), the controller is operable, A cold start voltage converter (30) configured to i) deliver input power to the auxiliary terminal (9) or 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, and iii) obtaining a minimum input voltage at the input of the cold start voltage converter and a power supply voltage (V sup ) is below the minimum required supply voltage (V CS ) starts the operation, It is characterized in that the power management integrated circuit includes Internal nodes (N aux ), the internal node and the auxiliary terminal (9) or the integrated on-chip capacitor (C int ) is electrically connected so that the auxiliary voltage of the internal node (V aux ) corresponds to the voltage at the auxiliary terminal (9) or to the voltage at the integrated on-chip capacitor (C int ) corresponds to the voltage of the internal node (N aux ) is further electrically connected to the power input terminal of the controller so that the power voltage at the input terminal of the controller is equal to the auxiliary voltage (V aux ) corresponds to, and the internal node (N aux ) is electrically separated from the first storage device terminal (12), so that the auxiliary voltage (V aux ) is independent of the voltage at the first storage device terminal (12), A monitoring unit (45) coupled to the controller (40) and configured to monitor the auxiliary voltage (V aux ) and for monitoring a first storage parameter (V Batt1 ), The controller (40) is configured to i) As long as the first storage parameter (V Batt1 ) is lower than the predefined upper storage value (V Batt1-up ), the main voltage converter system (20) is operated to deliver power to the first storage device terminal (12) via a first power delivery path (P-O1), wherein the upper limit storage value (V Batt1-up ), which, when reached, corresponds to the first rechargeable energy storage device being charged, and ii) operating the main voltage converter system (20) to deliver power to the auxiliary terminal (9) or the integrated on-chip capacitor (C) via a second power delivery path (P-O2) int ), or alternatively enabling operation of the cold start voltage converter (30) to deliver power to the auxiliary terminal (9) or the integrated on-chip capacitor (C int ), and maintain the auxiliary voltage (V aux ): a) equal to a target value, wherein the target value is a predefined voltage value corresponding to an appropriate voltage value for operating the controller (40), or b) at a lower threshold voltage (V sup-min ) and is higher than the lower threshold voltage (V sup-min ) upper threshold voltage (V sup-max ), and wherein the target value and the lower threshold voltage (V sup-min ) is higher than the minimum required supply voltage (V CS ), and wherein the voltage range corresponds to an optimal voltage range as a power supply voltage for operating the controller.

14. The power management integrated circuit according to claim 13, in, The auxiliary voltage (V aux ) equal to the target value include: The main voltage converter system or the cold start voltage converter (30) is operated to continuously maintain the auxiliary voltage (V aux ) is equal to the target value, And wherein, the auxiliary voltage (V aux ) is within a voltage range including: If the auxiliary voltage (V aux ) has dropped below the lower threshold voltage (V sup-min ), the main voltage converter system (20) or the cold start voltage converter (30) is operated to deliver power to the auxiliary terminal (9) or the integrated on-chip capacitor (C int ), until the auxiliary voltage (V aux ) has increased above the lower threshold voltage (V sup-min ) upper threshold voltage (V sup-max ).

15. The power management integrated circuit according to claim 13, wherein: The main voltage converter system (20) includes a first voltage converter (20a) having an output coupled to the first storage device terminal (12) via the first power delivery path (PO1) and an input connected to the first power input terminal (11), and A second voltage converter (20b) having a second power supply coupled to the integrated on-chip capacitor (C int ) or the auxiliary terminal (9) and an input connected to any one of the following: the first power input terminal (11), the first storage device terminal (12) or the additional power input terminal.

16. The power management integrated circuit according to claim 14, wherein: The main voltage converter system (20) includes a first voltage converter (20a) having an output coupled to the first storage device terminal (12) via the first power delivery path (PO1) and an input connected to the first power input terminal (11), and A second voltage converter (20b) having a second power supply coupled to the integrated on-chip capacitor (C int ) or the auxiliary terminal (9) and an input connected to any one of the following: the first power input terminal (11), the first storage device terminal (12) or the additional power input terminal.

17. The power management integrated circuit according to any one of claims 13 to 16, wherein: The main voltage converter system (20) includes a buck / boost voltage converter configured to in >(V out +Δ) in buck mode, at V in <(V out -Δ) in boost mode, and V in =V out ±Δ when operating in buck-boost mode, where V in and V out are the input voltage and output voltage of the main voltage converter system (20), respectively, and Δ is an operating parameter of the buck / boost voltage converter.

18. The power management integrated circuit according to any one of claims 13 to 16, wherein: The main voltage converter system (20) includes an input selection circuit (22), which is controlled by the controller (40) and is configured to select an input path from a plurality of input paths, so that the main voltage converter system (20) receives input power via the selected input path, and wherein the plurality of input paths for the main voltage converter system include at least: i) a first input path (P-I1), which electrically connects the first power input terminal (11) to the input end of the main voltage converter system (20); and ii) a second input path (P-I2), which electrically connects another power input terminal (18) to the input end of the main voltage converter system (20), or alternatively, electrically connects the first storage device terminal (12) to the input end of the main voltage converter system.

19. The power management integrated circuit according to claim 18, wherein: The controller (40) is further configured to select the second input path (PI2) and operate the main voltage converter system (20) to deliver power to the auxiliary terminal (9) or the integrated on-chip capacitor (C) via the second power delivery path (PI2). int ), and wherein said selecting of said second input path (P-I2) is performed if either of the following two situations occurs: a) If the auxiliary voltage (V aux ) has risen from above the lower threshold voltage (V sup-min ) drops to a predefined critical threshold voltage (V T-B ), where the minimum required supply voltage (V CS )<the predefined critical threshold voltage (V T-B )<the lower threshold voltage (V sup-min ),or b) If the auxiliary voltage (V aux ) has dropped below the lower threshold voltage (V sup-min ) and the monitoring unit detects that no input power is available at the first power input terminal.

20. The power management integrated circuit according to any one of claims 13 to 16 and 19, wherein: The controller is further configured to iii) If the auxiliary voltage (V aux ) has been reduced from the lower threshold voltage (V sup-min ) drops below the minimum required supply voltage (V CS ), the operation of the cold start voltage converter is enabled to recharge the auxiliary rechargeable energy storage device (C1) until a predefined switching voltage (V SW ), and then disabling operation of the cold start voltage converter and enabling operation of the main voltage converter system.

21. The power management integrated circuit according to claim 20, wherein: The predefined switching voltage (V SW ) is equal to or higher than the target value or alternatively is equal to or higher than the lower threshold voltage (V sup-min ).

22. A system (100) for energy harvesting, the system comprising: · an integrated circuit (1) according to any one of claims 13 to 21, an energy harvester (70), the energy harvester being coupled to the first power input terminal (11), a first rechargeable energy storage device (BATT1) coupled to the first storage device terminal (12), • An auxiliary rechargeable energy storage device (C1) coupled to the auxiliary terminal (9).

23. The system of claim 22, wherein: The first rechargeable energy storage device (BATT1) is a rechargeable battery, a capacitor or a supercapacitor.

24. The system of claim 22, wherein: The first rechargeable energy storage device (BATT1) is a supercapacitor having an energy storage capacity between 1 microfarad and 100 farads.

25. The system of claim 22, wherein: The auxiliary rechargeable energy storage device is a capacitor having an energy storage capacity between 0.1 nanofarad and 100 microfarad.

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