Inductor-less power converter

Abstract

To provide an inductor-less power converter that can improve the overall energy loss of a power converter.SOLUTION: An inductor-less power converter 1 includes a plurality of cascaded capacitor stages CSn (n=1 to 4). Each of the capacitor stages includes a flying capacitor Cn connected in parallel across an input terminal pair and an output terminal pair of the capacitor stage CSn. A switching block SBm (m=1 to n+1) is provided between cascade connection stages. Each of the switching blocks SBm includes: an input terminal pair and an output terminal pair; and switching means for connecting one of the input terminals of the switching block with one of the output terminals, and connecting one of the top plate or the bottom plate of the capacitors of each capacitor stage with the top plate or bottom plate of the capacitor of each subsequent cascaded capacitor stage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention generally relates to a power converter. More specifically, the present invention relates to an inductorless power converter having multiple stages of switched capacitors for converting an input voltage to an output voltage at a conversion ratio. [Background technology]

[0002] A power converter is an electrical device that converts an input voltage into an output voltage. These voltages may vary depending on the conversion ratio, and the input current may differ from the output current in form and / or frequency. For example, a converter may be configured to convert an alternating current (AC) input voltage to a direct current (DC) output voltage, preferably with a different voltage difference.

[0003] Such power converters are typically used in portable electronic devices such as mobile phones, laptop computers, and portable computers to convert electrical energy from one voltage level to another, or from one type to another, but are also widely used in the Internet of Things (IoT), devices, or wireless sensor nodes, and WSNs. In such applications, the main power source is often (primarily) supplied by a battery, and these devices often further have energy harvesting modules that extract energy for battery charging and / or power supply to the load.

[0004] Power converters designed around a series of switches and capacitors are well-known and widely used. Recently, switched-capacitor designs with multiple stages have become increasingly common. Such designs have the advantage of being suitable for small, integrated designs or fully integrated implementations, compared to known inductor-based power converters, because they lack magnetic components or large form factor components.

[0005] Also, such a design does not require a dummy load, so it can handle a wider range of loads. Also, the conversion efficiency of such a power converter is generally higher than that of an inductor-based alternative. Overall, such an inductorless design is ideal for battery-driven applications.

[0006] However, the inductorless design also has drawbacks compared to inductor-based alternatives. An inductor-based power converter has a continuous conversion ratio from a large conversion ratio, while the inductorless design has a limited number of discrete conversion ratios and a low maximum or minimum conversion ratio. Furthermore, although an inductorless power converter may have different conversion ratios, switching the conversion ratio causes energy losses and degrades the overall performance of the converter. In particular, this is significant when compared to inductor-based alternatives that have a continuous conversion ratio so that no energy losses occur when switching from one conversion ratio to another.

[0007] Therefore, there is a need for an improved inductorless power converter configured to switch between multiple conversion ratios to improve the overall energy loss of the power converter. SUMMARY OF THE INVENTION

[0008] In a first embodiment, an inductorless power converter is provided having a conversion ratio between an input voltage and an output voltage for converting an input voltage at an input terminal to an output voltage at an output terminal, the power converter having a plurality of cascaded capacitor stages, each capacitor stage having a flying capacitor connected in parallel across the input terminal pair and output terminal pair of the capacitor stage, a switching block provided between each cascaded stage, the switching block having an input terminal pair and an output terminal pair, and switching means for connecting one of the input terminals of the switching block to one of the output terminals, and for connecting either the top plate or bottom plate of the capacitor of each capacitor stage to the top plate or bottom plate of the capacitor of each subsequent cascaded capacitor stage, the power converter further comprises a control unit arranged to operate the switching means of each switching block according to a selected conversion ratio setting from a list of planned conversion ratio settings, each representing a different conversion ratio, and constituting the connection state of each of the switching blocks, the planned conversion ratio settings so that the steady voltage of each flying capacitor is equal between each conversion ratio setting and can be switched between conversion ratio settings without loss.

[0009] The proposed converter is an inductorless power converter configured for DC-DC conversion, converting an input voltage to an output voltage from direct current (DC) to direct current (DC). The input voltage is supplied to the input terminal pair, and the output voltage is supplied to the output terminal pair. The ratio of the input voltage to the output voltage defines the conversion ratio, which may be greater than or less than 1; that is, the voltage may be boosted or bucked, and therefore may increase or decrease.

[0010] The converter is a switched-capacitor converter, particularly a DC-DC switched-capacitor converter. The converter consists of multiple stages, each of which can be considered a cascaded stage having a capacitor or a flying capacitor. The capacitors may be charged and discharged depending on how they are connected. The connection method of the capacitors is defined by the operation of the switching block connected between each of the flying capacitors (also called capacitor stages). Thus, the converter has n capacitor stages, thereby having n flying capacitors, and between each capacitor stage there is a switching block equipped with switching means, such as integrated switching means such as transistors. Switching blocks may also be present between each capacitor stage and the input and output terminals.

[0011] Each switching block's switching means may have four terminals: an input terminal pair and an output terminal pair. Thus, one terminal is connected to the top plate of the preceding capacitor stage (or the input terminal of the first switching block), one to the top plate of the succeeding capacitor stage (or the output terminal of the last switching block), one to the bottom plate of the preceding capacitor stage (or the ground of the first switching block), and one to the bottom plate of the succeeding capacitor stage (or the ground of the last switching block). The switching means is arranged to connect one of the input terminal pairs to one of the output terminal pairs, thus resulting in either the top plate of the preceding capacitor stage being connected to the top plate of the succeeding capacitor stage, or the top plate of the preceding capacitor stage being connected to the bottom plate of the succeeding capacitor stage, or the bottom plate of the preceding capacitor stage being connected to the top plate of the succeeding capacitor stage.

[0012] Because the control methods for the switching means differ, and the connection methods for each capacitor differ, the number of capacitor stages, and consequently the number of switching blocks, determines the number of conversion ratio options. Increasing the number of stages increases the number of configurable conversion ratios.

[0013] While switching means can be operated according to multiple conversion ratio settings, it has been found that switching these settings can reduce the efficiency of the converter. In particular, the inventors have found that such efficiency losses can be reduced or, in some cases, avoided. The inventors' insight was that switching between conversion ratios can be achieved losslessly, and therefore without or at least with minimal efficiency losses, if the steady-state voltage of each flying capacitor is kept equal between conversion ratios. Therefore, the control unit may be configured to allow the selection of a conversion ratio setting only if this requirement is maintained, out of all possible conversion ratios. Thus, the current conversion ratio may be changed by the controller to the next conversion ratio according to a list or sub-selection of all conversion ratio settings in which it is determined that the steady-state voltage of each flying capacitor is kept equal between the current conversion ratio and the subsequent conversion ratio (and therefore the conversion ratio setting).

[0014] The proposed power converter can achieve conversion according to a number of discrete conversion ratios and according to boost or buck conversion, for example, by operating the converter in either buck or boost mode. The proposed power converter has the advantage that energy losses associated with the discharge and / or charging of flying capacitors are kept to a minimum or completely eliminated. Conventional power converters based on flying capacitors or switching capacitors may require settling time between conversion ratio settings, which reduces operational effectiveness and efficiency. The proposed power converter also has the advantage of enabling a fully integrated IC design.

[0015] In one example, the converter features four cascaded capacitor stages.

[0016] In one example, the converter has five switching blocks.

[0017] In one example, the control unit includes a memory unit for storing a list of planned conversion ratio settings, the list of planned conversion ratio settings being a sub-selection of all possible conversion ratio settings.

[0018] In one example, the converter is configured for a direct current (DC) input voltage.

[0019] In one example, the converter is configured to convert an input voltage to an output voltage in a power range of 10 μW to 100 mW, more preferably between 50 μW and 50 mW.

[0020] In one example, the converter is positioned to power one or more of the following: a sensor module, an IoT device, a USB device, or a Bluetooth® module.

[0021] In one example, the converter further comprises a multi-output voltage rail having multiple outputs, each having a different output voltage level, and each output comprises an output capacitor connected in parallel on the output and a switching output means for connecting the voltage rail to each output.

[0022] In one example, each switching output means is activated sequentially to sequentially charge each of the output capacitors.

[0023] In one example, the converter further comprises a multi-input voltage rail having multiple inputs, each having a different input voltage level, and each input comprises an input capacitor connected in parallel on the input and a switching input means for connecting the voltage rail to each input.

[0024] In one example, each switching input means is activated sequentially to sequentially charge each of the input capacitors.

[0025] In a further aspect of this disclosure, an energy harvester configuration is provided, which is: An energy harvesting module for harvesting ambient energy, preferably one of solar, thermal, kinetic, or radio frequency energy, and providing the harvested energy as an input voltage to an energy harvester arrangement, An inductorless power converter as described in any of the above claims, It is equipped with.

[0026] Those skilled in the art will understand that the energy harvesting modules described above are merely examples, and that the disclosure is not limited to these examples, and that any other type of applicable energy source may be used with a suitable type of energy harvesting module.

[0027] In one example, this arrangement is: The system further comprises a maximum power point tracking module, which acts as the control unit of the inductorless power converter to operate the switching means of each switching block of the power converter according to a maximum power point tracking algorithm selected according to the steady-state voltage of each flying capacitor so as to be equal between each conversion ratio setting.

[0028] The present invention will now be described in more detail by specific embodiments with reference to the accompanying drawings. Identical or similar parts and / or components are indicated by the same reference numeral. The present invention is by no means limited to the disclosed embodiments. [Brief explanation of the drawing]

[0029] Herein, the present disclosure will be described by an embodiment of an inductorless power converter according to a first aspect and an energy harvester arrangement according to a second aspect, with reference to the following drawings.

[0030] [Figure 1]A schematic diagram of an embodiment of an inductance - less power converter according to a first aspect of the present disclosure is shown, indicating possible connections between one input terminal and one output terminal of the switching block. [Figure 2] A schematic diagram of the inductance - less power converter of FIG. 1 is shown, indicating an embodiment of one of the switching blocks. [Figure 3] An example of the configuration of an inductance - less power converter according to a first aspect of the present disclosure for four different conversion ratios is shown. [Figure 4] A schematic diagram of another embodiment of an inductance - less power converter according to a first aspect of the present disclosure is shown. [Figure 5] A schematic diagram of an embodiment of an energy harvester arrangement according to a second aspect of the present disclosure is shown.

MODE FOR CARRYING OUT THE INVENTION

[0031] FIGS. 1 and 2 show an inductance - less power converter 1 for converting an input voltage V A at the input terminals of the inductance - less power converter 1 to an output voltage V B at the output terminals of the inductance - less power converter 1. The power converter 1 includes four cascaded capacitor stages CS n (n = 1 to 4), and each capacitor stage includes a flying capacitor C n connected in parallel across the input terminal pair and the output terminal pair of the capacitor stage CS n .

[0032] Between each cascaded stage CS n , a switching block SB m (m = 1 to n + 1) is provided. Each switching block SB m includes an input terminal pair, an output terminal pair, and the switching block SB mIt comprises a switching means for connecting one of the two input terminals and one of the two output terminals. Regarding switching block SB2, Figure 1 shows in more detail the four possible connections between the input and output terminals of each switching block SB2, but this is for other switching blocks SB m It can also be applied to this.

[0033] The first switching block SB1 connects either the top or bottom plate of capacitor C1, which is connected to the output terminal of the first switching block SB1, to the input voltage V of the power converter 1. A It is positioned to connect to either the top or bottom plate of capacitor C4 connected to the input terminal of the last switching block SB5, and the output voltage V of power converter 1. B It is positioned to connect either to or to earth.

[0034] Switching Block SB m (m=2~4) represents each switching block SB m Capacitor C connected to the input terminal m-1 Either the top plate or the bottom plate, and each switching block SB m Capacitor C connected to the output terminal m It is positioned to connect either the top plate or the bottom plate.

[0035] The control unit 21 of the power converter 1 (not shown in Figures 1 to 3 for clarity) controls each switching block SB according to the selected conversion ratio setting from the list of planned conversion ratio settings. m The switching means is arranged to operate. Each planned conversion ratio setting is based on the input voltage V A and output voltage V B This represents the different conversion ratios between and for each switching block SB. m This configures the connection state for each of the following. The planned conversion ratio setting is determined by each flying capacitor C between each conversion ratio setting.n The steady-state voltages are defined to be equal, allowing for lossless switching between conversion ratio settings.

[0036] Figure 2 shows the switching block SB. m One embodiment is shown, a switching block SB m is a switching block SB m Each of the input and output terminals is connected to a common internal node V int,m It is equipped with four switching means for connection. The switching means, for example, transistors, are controlled by the control unit 21 of the power converter 1.

[0037] The control unit 21 includes a memory unit 23 for storing a list of planned conversion ratio settings, the list of planned conversion ratio settings being a sub-selection of all possible conversion ratio settings.

[0038] The voltage of each capacitor is the internal node voltage V int,m The following internal node voltages V are obtained by adding or subtracting from the following: int,m+1 It can create an internal voltage V int,m For more information, see below:

number

[0039] Weight coefficient w A , w B , w x (x=n=1~4) defines how the capacitors are connected. Weight coefficient w A When the ground terminal is connected to the input terminal of switching block SB1, the input voltage V of power converter 1 is 0. A If it is connected to the input terminal of switching block SB1, it can be set to one of 1. Weight coefficient w B When the ground terminal is connected to the output terminal of switching block SB5, the voltage is 0, or the output voltage V of power converter 1. BIf it is connected to the output terminal of switching block SB5, it can be one of 1. Capacitor weighting coefficient w x (x=n) is the capacitor C n If bypassed, the capacitor voltage V is 0. Cn If subtracted, -1, or the capacitor voltage V Cn When added, it can be any of 1. Weight coefficient w A , w B , w x For more information, see below:

number

[0040] The premise is as follows: Input voltage V of power converter 1 A This is, for example, a fixed voltage supplied from a battery or supply rail, and capacitor C n The steady-state voltage applied is fixed, and the input voltage V of power converter 1 is fixed. A Assuming it is a fraction of V, Cx =V A ·k x The input voltage V of power converter 1 A and the output voltage V of power converter 1 B The ratio is the conversion ratio V B =V A Defined by M.

[0041] Internal node voltage V int,m Using the formula for , we get:

number

[0042] this is,

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[0043] The following formula:

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[0044] The following example illustrates how to create multiple conversion ratios M using the same k vector, where the magnitude of k is equal to the number of capacitors n. In this example, power converter 1 has four capacitors C n (n=1~4) and five switching blocks SB m (m=1~5) and is provided. The corresponding equation is that the power converter 1 is a capacitor C n It can be expanded as needed, whether you want to have more or fewer features.

number

[0045] Figure 3 shows two capacitors C n (n=1~2) and three switching blocks SB m (m=1~3) and V C1 =V A 2 / 3 and V C2 =V A The complete configuration for power converter 1 is shown, where k = [2 / 3 1 / 3] such that k is 1 / 3, and there are four possible conversion ratios M.

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[0046] Each switching output means S y This is the output capacitor C yEach of them is sequentially activated by the control unit 21 in order to charge them sequentially.

[0047] Figure 5 shows one embodiment of an energy harvester arrangement 100 according to a second aspect of the present disclosure. The energy harvester arrangement 100 comprises an energy harvester for harvesting ambient energy, preferably one of solar, kinetic, or radio frequency energy. The harvested energy is provided as an input voltage to an inductorless power converter 1, as described above. The output voltage of the inductorless power converter 1 is supplied to a battery.

[0048] The energy harvester configuration 100 further comprises a maximum power point tracking (MPPT) module 11, which acts as a control unit 21 for the inductorless power converter 1. The MPPT module 11 controls each flying capacitor C to be equal between each conversion ratio setting. n The switching means of each switching block SBm of the power converter 1 are controlled according to a maximum power point tracking algorithm selected according to the steady-state voltage.

[0049] Based on the above description, a person skilled in the art may provide modifications and additions to the disclosed methods and arrangements, all of which are included in the appended claims.

Claims

1. An inductorless power converter having a conversion ratio between the input voltage and the output voltage for converting the input voltage of an input terminal to the output voltage of an output terminal, the inductorless power converter comprises a plurality of cascaded capacitor stages, each cascaded capacitor stage comprises a flying capacitor connected in parallel to the input terminal pair and output terminal pair of the cascaded capacitor stage, a switching block is provided between each cascaded capacitor stage, the switching block has an input terminal pair and an output terminal pair, and the input terminal of the switching block is connected to one of the output terminals, and the top of the capacitor of each cascaded capacitor stage An inductorless power converter comprising a switch configured to connect either a plate or a bottom plate to the top plate or bottom plate of the capacitors of each subsequent cascaded capacitor stage, wherein the inductorless power converter further comprises a control unit arranged to operate the switching of each switching block according to a conversion ratio setting selected from a predetermined list of conversion ratio settings, each representing a different conversion ratio and constituting the connection state of each switching block, wherein the predetermined conversion ratio settings allow the steady voltage of each flying capacitor to be equal between each conversion ratio setting and to be switched between the conversion ratio settings without loss.

2. The inductorless power converter according to claim 1, wherein the inductorless power converter comprises four cascaded capacitor stages.

3. The inductorless power converter according to claim 1, wherein the inductorless power converter comprises five switching blocks.

4. The inductorless power converter according to claim 1, wherein the control unit comprises a memory unit for storing the list of predetermined conversion ratio settings, the list of predetermined conversion ratio settings being a sub-selection of all possible conversion ratio settings.

5. The inductorless power converter according to claim 1, wherein the inductorless power converter is arranged for a direct current (DC) input voltage.

6. The inductorless power converter according to claim 1, wherein the inductorless power converter is arranged to convert an input voltage to an output voltage in a power range of 10 μW to 100 mW, more preferably 50 μW to 50 mW.

7. The inductorless power converter according to claim 1, wherein the inductorless power converter is arranged to supply power to at least one module or device selected from the group consisting of a sensor module, an IoT device, a USB device, and a Bluetooth® module.

8. The inductorless power converter according to claim 1, further comprising a multi-output voltage rail having a plurality of outputs, each having a different output voltage level, wherein each output comprises an output capacitor connected in parallel to the output and a switching output configured to connect the multi-output voltage rail to each output.

9. The inductorless power converter according to claim 1, wherein the inductorless power converter is arranged to convert an input voltage to an output voltage in a power range of 50 μW to 50 mW.

10. The inductorless power converter according to claim 1, further comprising a multi-input voltage rail having a plurality of inputs, each having a different input voltage level, wherein each input comprises an input capacitor connected in parallel to the input and a switching input configured to connect the multi-input voltage rail to each input.

11. The inductorless power converter according to claim 2, wherein the inductorless power converter comprises five switching blocks.

12. The inductorless power converter according to claim 2, wherein the control unit comprises a memory unit for storing the list of predetermined conversion ratio settings, the list of predetermined conversion ratio settings being a sub-selection of all possible conversion ratio settings.

13. The inductorless power converter according to claim 2, wherein the inductorless power converter is arranged for a direct current (DC) input voltage.

14. The inductorless power converter according to claim 8, wherein each switching output is sequentially activated to sequentially charge each of the output capacitors.

15. The inductorless power converter according to claim 10, wherein each of the switching inputs is sequentially activated to sequentially charge each of the input capacitors.

16. Energy harvester configuration, An energy harvesting module for harvesting ambient energy selected from the group consisting of solar energy, thermal energy, kinetic energy, and radio frequency energy, and for providing the harvested energy as an input voltage to the energy harvester arrangement, The inductor-less power converter according to claim 1, An energy harvester configuration that includes the following features.

17. The energy harvester arrangement further comprises a maximum power point tracking module, The energy harvester arrangement according to claim 16, wherein the maximum power point tracking module acts as the control unit of the inductorless power converter to operate the switching of each switching block of the inductorless power converter according to a maximum power point tracking algorithm selected such that the steady-state voltage of each flying capacitor is equal between each conversion ratio setting.

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