KR-102964274-B1 - Method and device for energy harvesting using a cold start voltage converter

KR102964274B1KR 102964274 B1KR102964274 B1KR 102964274B1KR-102964274-B1

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 by a cold start voltage converter, and then the main voltage converter system charges the first rechargeable energy storage device until it reaches an upper charge threshold level. The voltage of the auxiliary energy storage device is monitored and maintained to be equal to a target value suitable for operating the controller, or alternatively, within a predetermined voltage range corresponding to a supply voltage range to operate the controller of the main voltage converter system. The present invention also relates to a power management integrated circuit for energy harvesting comprising a cold start and a main voltage converter system, wherein an internal voltage node is maintained within a voltage range suitable as a target value or as a supply voltage for the controller of the main voltage converter system.

Inventors

데 보스, 줄리엔
고쎄트, 지오프로이

Assignees

이-피스

Dates

Publication Date: 20260512
Application Date: 20201127
Priority Date: 20191210

Claims (17)

A method for energy harvesting using a power management integrated circuit comprising a cold-start voltage converter, a main voltage converter system (20), and a controller (40) for controlling the main voltage converter system, wherein the controller is operable if the supply voltage (V sup ) at the supply input of the controller is greater than or equal to the minimum required supply voltage (V CS ), and the method comprises: The step of connecting an energy harvester (70) to the input of the main voltage converter system, A step of coupling a first rechargeable energy storage device (BATT1) to the output of the main voltage converter system, The step of connecting the above energy harvester (70) or another energy source to the input of the above cold start voltage converter, A step of coupling an auxiliary rechargeable energy storage device (C1) to the output of the cold start voltage converter, A step of coupling the auxiliary rechargeable energy storage device (C1) to the supply input of the controller to use the auxiliary rechargeable energy storage device (C1) when charged as a voltage source for the controller, A step of monitoring the auxiliary voltage (V C ) of the auxiliary rechargeable energy storage device (C1) and monitoring the first storage parameter (V Batt1 ) indicating the charge level of the first rechargeable energy storage device (BATT1), A step of charging the auxiliary rechargeable energy storage device (C1) by operating the cold start voltage converter until the auxiliary voltage (V C ) reaches a predetermined switching voltage ( V SW ) that is greater than or equal to the minimum required supply voltage (V CS), A step of activating the operation of the main voltage converter system and deactivating the operation of the cold start voltage converter when the auxiliary voltage (V C ) reaches the predetermined switching voltage (V SW ), The method comprises the step of operating the main voltage converter system (20) to charge the first rechargeable energy storage device (BATT1) with energy from the energy harvester (70) as long as the first storage parameter (V Batt1 ) of the first rechargeable energy storage device (BATT1) is less than a predetermined upper storage value (V Batt1-up ), and maintaining the auxiliary rechargeable energy storage device (C1) electrically disconnected from the first rechargeable energy storage device (BATT1) during the charging of the first rechargeable energy storage device (BATT1). The auxiliary voltage (V C ) of the above auxiliary rechargeable energy storage device (C1), a) equal to the target value, or alternatively, b) maintaining within a voltage range between a lower threshold voltage (V sup-min ) and an upper threshold voltage (V sup-max ) that is higher than the lower threshold voltage (V sup-min ). Includes, The step of maintaining the auxiliary voltage equal to the target value or within the voltage range comprises operating the main voltage converter system, or alternatively operating the cold start voltage converter to recharge the auxiliary energy storage device (C1) with energy from the energy harvester (70).
In paragraph 1, The step of maintaining the auxiliary voltage (V C ) equal to the target value is, It includes continuously compensating for a decrease in charge of the auxiliary energy storage device (C1) so that the auxiliary voltage (V C ) is maintained equal to the target value, and The step of maintaining the auxiliary voltage (V C ) within the lower threshold voltage (V sup-min ) and the upper threshold voltage (V sup-max ) comprises: A method comprising recharging the auxiliary rechargeable energy storage device ( C1) until the auxiliary voltage (V C ) reaches the upper threshold voltage (V sup- max) if the auxiliary voltage (V C ) has decreased below the lower threshold voltage (V sup- min ).
In claim 1, if the auxiliary voltage (V C ) decreases 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 the recharging is, i) a step of disengaging the output portion of the main voltage converter system from the first rechargeable energy storage device (BATT1), ii) connecting the output portion 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 ) reaches the upper threshold voltage (V sup-max), iii) If the auxiliary voltage (V C ) reaches the upper threshold voltage (V sup-max ), disengage the output of the main voltage converter system from the auxiliary rechargeable energy storage device (C1) and connect the output of the main voltage converter system to the first rechargeable energy storage device (BATT1). A method including
In paragraph 1 or 3, a) If the first storage parameter (V Batt1 ) is higher than a predetermined lower storage value (V Batt1-min ), and b) If the auxiliary voltage ( VC ) is reduced to less than the lower threshold voltage (Vsup -min ) and the energy harvester does not provide energy, or if the auxiliary voltage ( VC ) is reduced from a value exceeding the lower threshold voltage (Vsup -min ) to a predetermined critical threshold voltage ( VTB ) ( VCS < VTB < Vsup -min , where VCS , VTB , and Vsup -min are the minimum required supply voltage, the critical threshold voltage, and the lower threshold voltage, respectively), The above auxiliary rechargeable energy storage device (C1) is recharged with energy from the first rechargeable energy storage device (BATT1), and The above recharge is, i) a step of disengaging the energy harvester (70) from the input of the main voltage converter system, ii) a step of disengaging the first rechargeable energy storage device (BATT1) from the output portion of the main voltage converter system, iii) a step of coupling the first rechargeable energy storage device (BATT1) to the input portion of the main voltage converter system, iv) connecting 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 ) reaches the upper threshold voltage (V sup-max), v) If the auxiliary voltage (V C ) reaches the upper threshold voltage (V sup-max ), reconnect the energy harvester to the input of the main voltage converter system and reconnect the first rechargeable energy storage device (BATT1) to the output of the main voltage converter system. A method including
In any one of paragraphs 1 through 3, A method further comprising the step of activating the operation of the cold start voltage converter to recharge the auxiliary rechargeable energy storage device ( C1 ) until the predetermined switching voltage (V SW ) is reached, if the auxiliary voltage (V C) is reduced from the lower threshold voltage (V sup-min ) to a value less than the minimum required supply voltage (V CS), wherein the operation of the cold start voltage converter is then deactivated and the operation of the main voltage converter system is activated.
A method according to any one of claims 1 to 3, wherein the main voltage converter system (20) comprises a first voltage converter (20a) and a second voltage converter (20b), wherein the charging of the first rechargeable energy storage device (BATT1) by 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) by energy from the energy harvester (70) or by energy from the first rechargeable energy storage device (BATT1) is performed by operating the second voltage converter (20b), and the recharging of the auxiliary rechargeable energy storage device (C1) is performed separately from the charging of the first rechargeable energy storage device (BATT1).
A method according to any one of claims 1 to 3, wherein the main voltage converter system (20) comprises a buck/boost voltage converter configured to operate in buck mode when V in > (V out + Δ), to operate in boost mode when V in < (V out - Δ), and to operate in buck-boost mode when V in = V out ± Δ, wherein V in and V out are the input voltage and output voltage of the main voltage converter system, respectively, and Δ is the operating parameter of the buck/boost voltage converter.
A method according to any one of claims 1 to 3, wherein the first rechargeable energy storage device (BATT1) has an energy storage capacity that is more than one hundred times greater than the energy storage capacity of the auxiliary rechargeable energy storage device (C1).
In any one of paragraphs 1 through 3, After charging the first rechargeable storage device (BATT1), if the first storage parameter (V Batt1 ) of the first rechargeable energy storage device (BATT1) decreases below the upper storage value (V Batt1-up ), the main voltage converter system (20) is operated to recharge the first rechargeable energy storage device (BATT1) with energy from the energy harvester (70) to maintain the charged first rechargeable energy storage device (BATT1), and during the recharging of the first rechargeable energy storage device (BATT1), the auxiliary rechargeable energy storage device (C1) is kept electrically disconnected from the first rechargeable energy storage device (BATT1). A method that further includes.
As a power management integrated circuit (1) for energy harvesting, One or more power input terminals for receiving input power from an energy harvester or another power source, A first storage device terminal (12) that can be connected to a first rechargeable energy storage device, An integrated on-chip capacitor (C int ) or auxiliary terminal (9) that can be 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) among the above one or more power input terminals, A controller (40) configured to control the main voltage converter system (20), wherein the controller (40) is operable if the supply voltage (V sup ) at the supply input of the controller (40) is greater than or equal to the minimum required supply voltage (V CS ). i) to transfer input power to the auxiliary terminal (9) or to the integrated on-chip capacitor (C int ), ii) to receive the input power through the first power input terminal (11) or the second power input terminal (8) among the one or more power input terminals, and iii) to start operation if a minimum input voltage is available at the input of the cold start voltage converter and the supply voltage (V sup ) for the controller is lower than the minimum required supply voltage (V CS ) is configured to start operation. Includes, The above power management integrated circuit, An internal node (N aux ) electrically connected to the auxiliary terminal (9) or the integrated on-chip capacitor (C int ) such that the auxiliary voltage ( V aux) of the internal node corresponds to the voltage at the auxiliary terminal (9) or to the voltage of the integrated on-chip capacitor (C int ), wherein the internal node (N aux ) is additionally electrically connected to the supply input of the controller such that the supply voltage at the input of the controller corresponds to the auxiliary voltage (V aux ), and the internal node (N aux ) is electrically disconnected from the first storage device terminal (12) such that the auxiliary voltage (V aux ) is independent of the voltage at the first storage device terminal (12). It is characterized by including a monitoring device (45) coupled with the controller (40) and configured to monitor the auxiliary voltage (V aux ) of the internal node and to monitor the first storage parameter (V Batt1 ) at the first storage device terminal (12), The above controller (40), i) to operate the main voltage converter system (20) to transfer power to the first storage device terminal (12) through the first power transfer path (P -O1) as long as the first storage parameter (V Batt1 ) is less than a predetermined upper limit storage value (V BATT1-up), and ii) to operate the main voltage converter system (20) to transfer power to the auxiliary terminal (9) or to the integrated on-chip capacitor (C int ) through a second power transfer path (P-O2), or alternatively to activate the operation of the cold start voltage converter (30) to transfer power to the auxiliary terminal (9) or to the integrated on-chip capacitor (C int ), and to maintain the auxiliary voltage (V aux ) within a voltage range between a) equal to a target value or b) a lower threshold voltage (V sup-min ) and an upper threshold voltage (V sup-max ) higher than the lower threshold voltage (V sup-min), wherein the target value and the lower threshold voltage (V sup-min ) are higher than the minimum required supply voltage (V CS ).
In Paragraph 10, Maintaining the above auxiliary voltage (V aux ) equal to the target value is, It includes operating the main voltage converter system or the cold start voltage converter (30) to continuously maintain the auxiliary voltage ( Vc ) equal to the target value, and Maintaining the above auxiliary voltage (V aux ) within the voltage range is, A power management integrated circuit ( 1 ), comprising operating the main voltage converter system ( 20 ) or the cold start voltage converter (30) to transfer power to the auxiliary terminal (9) or the integrated on-chip capacitor (C int ) until the auxiliary voltage (V aux ) is increased to an upper threshold voltage (V sup -max) higher than the lower threshold (V sup-min ) when the auxiliary voltage (V aux) is reduced to less than the lower threshold voltage (V sup-min).
In item 10, the above main voltage converter system (20) is, A first voltage converter (20a) having an output portion coupled to the first storage device terminal (12) through the first power transfer path (P-O1) and an input portion connected to the first power input terminal (11), and A second voltage converter (20b) having an output connected to the integrated on-chip capacitor (C int ) or the auxiliary terminal (9) via the second power transfer path (P-O2) and an input connected to one of the first power input terminal (11), the first storage device terminal (12), or an additional power input terminal. A power management integrated circuit including
In claim 10, the main voltage converter system (20) comprises a buck/boost voltage converter configured to operate in buck mode when V in > (V out + Δ), to operate in boost mode when V in < (V out - Δ), and to operate in buck-boost mode when V in = V out ± Δ, wherein V in and V out are the input voltage and output voltage of the main voltage converter system (20), respectively, and Δ is the operating parameter of the buck/boost voltage converter, a power management integrated circuit.
In any one of claims 10 to 13, the main voltage converter system (20) is controlled by the controller (40) and includes an input selection circuit (22) configured to select an input path from a plurality of input paths, wherein the main voltage converter system (20) receives input power through the selected input path, and the plurality of input paths for the main voltage converter system include at least i) a first input path (P-I1) that electrically connects the first power input terminal (11) to the input section of the main voltage converter system (20), and ii) a second input path (P-I2) that electrically connects an additional power input terminal (18) to the input section of the main voltage converter system (20), or alternatively, electrically connects the first storage device terminal (12) to the input section of the main voltage converter system.
In paragraph 14, the controller (40) is further configured to operate the main voltage converter system (20) to select the second input path (P-I2) and to transfer power through the second power transfer path (P-O2) to the auxiliary terminal (9) or to the integrated on-chip capacitor (C int ), and the power management integrated circuit, wherein the selection of the second input path (P-I2) is performed if any of the following two conditions occur: a) where the auxiliary voltage (V aux ) is reduced from a value higher than the lower threshold voltage (V sup-min ) to a predetermined threshold voltage (V TB ) (V CS < V TB < V sup-min , where V CS , V TB , and V sup-min are the minimum required supply voltage, the threshold voltage, and the lower threshold voltage, respectively), or b) When the monitoring device detects that the auxiliary voltage (V C ) has decreased to less than the lower threshold voltage (V sup-min ) and that input power is not available at the first input terminal.
In any one of paragraphs 10 to 13, the controller is, iii) A power management integrated circuit further configured to activate the operation of the cold start voltage converter to recharge the auxiliary rechargeable energy storage device ( C1 ) until a predetermined switching voltage (V SW ) is reached, if the auxiliary voltage (V C ) is reduced from the lower threshold voltage (V sup- min) to a value less than the minimum required supply voltage (V CS), and then deactivate the operation of the cold start voltage converter and activate the operation of the main voltage converter system.
As a system (100) for energy harvesting, An integrated circuit (1) according to any one of paragraphs 10 to 13, An energy harvester (70) coupled to the first power input terminal (11), A first rechargeable energy storage device (BATT1) which is a capacitor or supercapacitor coupled to the first storage device terminal (12), An auxiliary rechargeable energy storage device (C1) coupled to the auxiliary terminal (9) A system for energy harvesting including

Description

Method and device for energy harvesting using a cold start voltage converter The present invention relates to a method and device for energy harvesting. More specifically, the present invention relates to a method and device for initiating charging of a rechargeable storage device using a power management integrated circuit (PMIC) comprising a cold-start voltage converter and a mains voltage converter system. The use of a voltage converter to extract energy from an energy harvester and to charge a rechargeable energy storage device is well known in the art. Subsequently, the energy stored in the rechargeable storage device can be used as a power source for, for example, an application load. The application load to be powered by the harvested energy can be any type of application, such as, for example, a portable device, a sensor, an external circuit, or a wireless transmitter. Various energy harvesters can be used as energy sources, for example, photovoltaic cells (PV), thermoelectric generators (TEGs), piezoelectric energy generators, and electromagnetic energy sources. Rechargeable storage devices are rechargeable batteries, for example, Li-ion batteries, supercapacitors, or conventional capacitors. Generally, an integrated circuit for energy harvesting includes a mains voltage converter system comprising one or more voltage converters, such as boost, buck, or buck-boost DC-DC voltage converters. The operation of the mains voltage converter system is controlled by a controller. The controller requires a supply voltage, for example, 2.5 V, 3.3 V, or 5 V. However, a PMIC for energy harvesting does not have an internal power source that powers the controller. In a PMIC of the prior art, the controller receives power from a rechargeable energy storage device connected to the output terminal of the PMIC. In some known embodiments, the PMIC includes, for example, a buck converter for converting the voltage of the rechargeable energy storage device to the supply voltage required for the controller. In other embodiments, the controller is connected to the storage device at the same voltage through a switch. Since the rechargeable energy storage device is not initially charged, the PMIC includes a cold start voltage converter that, in addition to the main voltage converter system, begins acquiring energy from the energy harvester without the use of the main voltage converter system. However, a cold start voltage converter, for example, including a charge pump, has low efficiency compared to the efficiency of the main voltage converter system regulated by a controller. Generally, the cold start voltage converter is used until the rechargeable energy storage device is sufficiently charged to provide the required supply voltage and start the operation of the main voltage converter system. This cold start voltage converter is a self-starting voltage converter configured to start operation when the input voltage at the input of the cold start voltage converter exceeds a minimum threshold value. A PMIC known under reference number AEM10940 and provided by e-peas SA of Belgium includes a cold start voltage converter that starts operating, for example, with an input voltage (V in ) as low as 380 mV and an input power of at least 11 μW. One of the problems with energy harvesting systems is that when starting with a depleted rechargeable storage device, it takes a long time to charge the rechargeable storage device with a cold start voltage converter. As a result, it also takes a long time before the applied load can accept power from the rechargeable storage device and start operating. In particular, if the rechargeable storage device is a supercapacitor that is 0 volts when completely uncharged, the charging time of the supercapacitor can be very long. However, charging the rechargeable battery to the required charge level to be ready to supply power to the applied load for a sufficiently long period can also take a considerably long charging time. An additional problem with the PMIC is that after charging the rechargeable energy storage device, the applied load can only accept power from the rechargeable energy storage device as long as the voltage exceeds the threshold voltage corresponding to the supply voltage required for the controller. For example, the rechargeable storage device can initially be charged up to 4.5 V, but when this voltage subsequently drops below, for example, a supply voltage of 2.5 V, the PMIC stops operating. This occurs even if the external load requires, for example, only a supply voltage of 1.2 V. When using capacitors or supercapacitors as storage devices, not all energy stored in the storage device can be used to supply the load, and oversizing of the storage device is necessary to achieve the target energy autonomy of the application, which is a period without the occurrence of energy harvesting. Therefore, there is room to improve integrated circuits for energy harvesting. This aspect and