Highly efficient switching charging device with reduced input voltage ripple

Abstract

Electronic device comprising a rechargeable battery and a voltage- or current-controlled power converter (150) for charging the battery, wherein the power converter (150) is designed to provide electrical power at an output voltage V out to charge the battery at an output of the power converter (150) from electrical power at an input voltage V into be derived at an input of the power converter (150), wherein the power converter (150) comprises an inductor (L), a first sub-converter (110) with several first switches (S1, S2, S3, S4) and a first capacitor cell (C1), and a second sub-converter (120) with several second switches (S5, S6, S7, S8) and a second capacitor cell (C2); wherein the power converter (150) comprises only a single inductor for the first sub-converter and for the second sub-converter, and a controller; wherein the controller is configured to control the several first and the several second switches such that the first and the second sub-converter are operated in a nested manner, and wherein a commutation cycle of the power converter comprises: - a first phase, during which the first capacitor cell and the inductor are connected in series between the input and the output of the power converter (150), and during which the second capacitor cell and the inductor are connected in series in parallel with the output of the power converter (150); - a second phase, during which the first capacitor cell and the inductor are connected in series in parallel with the output of the power converter (150), and during which the second capacitor cell and the inductor are connected in series between the input and the output of the power converter (150); and - a third phase, during which the first and second capacitor cells are decoupled from the output of the power converter (150), during which the charge of the first and second capacitor cells remains unchanged, and during which the inductor is arranged between the input and the output of the power converter (150) or is connected in parallel to the output of the power converter (150), wherein the controller is designed to control the multiple first and second switches in such a way that the power converter is operated in the third phase following the first phase and / or following the second phase within one commutation cycle, and wherein The controller is designed to do the following: - Determining an output current I out at the end of the first phase and / or at the end of the second phase; - Control the several first and second switches during the third phase such that the inductor is then arranged between the input and the output of the power converter (150) when the output current I out at the end of the first phase and / or at the end of the second phase less than a reference current I ref is; and - Control the several first and second switches during the third phase such that the inductor is then connected in parallel to the output of the power converter (150) when the output current I out at the end of the first phase and / or at the end of the second phase greater than the reference current I ref is.

Description

Technical field

[0001] The present invention relates to power converters with regulated output voltage or output current. In particular, the present invention relates to switching power converters for charging applications. background

[0002] The efficiency of a conventional switching power converter, such as a buck converter, is dominated by the losses in the switches (e.g., field-effect transistors, FETs) and the converter's inductor. If the power converter is operated with a relatively high input voltage Vin, the efficiency is significantly reduced. inIf the power is supplied via a high-voltage supply, the power converter typically exhibits reduced conversion efficiency because the switches must be implemented using high-voltage technology, resulting in an increased switching area and higher reverse recovery losses. Relatively large FETs typically lead to relatively high switching losses due to increased gate charge and LX capacitance.

[0003] The voltage applied to the inductor of a buck converter is proportional to the difference between the input voltage V in and the output voltage V out , i.e. V in - V out , during the magnetization phase or proportional to -V outDuring the demagnetization phase, increased inductor voltages cause increased current fluctuations dI / dt, thus requiring an increased switching frequency (to achieve a predetermined current ripple) and / or an increased current ripple (for a specific switching frequency). In both cases, this leads to increased inductor core losses and increased power dissipation.

[0004] Maintaining low current changes dI L / dt at increased input and output voltage requires due to the relationship dI L / dt = V L / L typically refers to inductors (i.e., coils) with an increased inductance L. Coils with an increased inductance L, however, have an increased number of turns. For inductors to maintain their DC resistance (DCR) even with an increased number of turns, each turn must use wire of increased thickness to compensate for the impedance increase. Thus, the size of the inductor doubles with an increased inductance L (due to the increased number of turns and the increased wire thickness). Conversely, if the inductor dimensions are not increased, an increased inductance L results in the DCR of the inductor doubling due to the additional number of turns and the use of thinner wire.

[0005] In recent years, battery-powered applications (such as smartphones and tablets) have seen increases in processing power, screen resolution, and refresh rate, and have added associated standby modes. This results in increased battery drain, meaning that electronic devices like smartphones typically require daily recharging. The limited operating time of battery-powered electronic devices can be addressed by using battery packs with increased capacity, but recharging such a pack requires less frequent recharging. This is because most electronic devices are charged via a standard (micro) USB port, which provides a limited current (~1.5 A).Therefore, a 5 Ah battery pack needs several hours to recharge even if the battery technology (usually LiIon / LiPolymer) would allow recharging in less than an hour (charging with 1 to 2 times the capacity per hour).

[0006] Recent changes to the USB charging specification allow voltages higher than the standard 5V, enabling more than four times the power from the USB supply (9V, 12V, and 20V). However, due to the limitations of space and height in electronic devices (especially regarding the inductors used for switching power converters), an increased input voltage Vi may not be feasible. inThe power dissipation of a power converter (provided, for example, via the USB port) cannot be compensated for by using inductors with a higher inductance L. As a result, either the DCR of the inductor must be increased or the switching frequency must be increased. Both measures lead to increased power dissipation and potentially to hot spots on the housing of an electronic device. US 2013 / 0 176 076 A1, US 2008 / 0 157 732 A1, DE 10 2010 013 375 A1, US 2015 / 0 084 611 A1, US 2014 / 0 070 787 A1, WO 2012 / 074 967 A1, DE 11 2012 004 377 T5, US 2014 / 0 043 010 A1 and US 8 619 445 B1 describe different power converters.

[0007] US Patent 2013 / 0176076A1 describes a voltage regulator for an envelope-tracking power supply system. The voltage regulator comprises a voltage control module with at least one energy storage element, the first terminal of which is connected to a first node and the second terminal of which is connected to a second node of the module. The module further comprises an input for receiving a reference voltage signal, which can be connected to either the first or second node, an output, which can be connected to either the first or second node, and a ground plane, which can be connected to either the second node.

[0008] US Patent 2008 / 0157732A1 describes a DC / DC converter with a pre-converter stage (e.g., charge pump) and a post-regulator stage (e.g., boost converter). The duty cycle of the post-regulator stage is controlled via a feedback path from the converter output to an input of the post-regulator stage. The pre-converter stage increases or decreases the input DC voltage by a positive or negative integer or fractional factor; the post-regulator stage variably boosts the voltage depending on the duty cycle.

[0009] German patent DE 10 2010 013 375 A1 describes a switching power supply for halving or doubling an input voltage using two capacitors and two groups of switching elements. By closing the first group and opening the second, the capacitors are connected in series between the input and ground; by closing the second group and opening the first, they are connected in series in reverse order. The output is tapped between the capacitors; the method comprises the aforementioned switching sequences.

[0010] US 2015 / 0084611A1 describes a device (e.g., a boost converter) with a first switch coupled to an inductor and carrying a charging current from a current source, and at least two second switches connected in series and in parallel to the first switch, which selectively direct the inductor current to at least two capacitors connected in series. A control circuit operates the first and second switches.

[0011] WO 2012 / 074 967 A1 describes an integrated 3-level DC / DC converter that combines features of inductor-based buck converters and switching capacitor converters. It utilizes a flying capacitor and an output inductor and operates in a four-step cycle: in two steps the capacitor regulates the output voltage, and in the other two the inductor. A power supply and an integrated power distribution system using this converter are also disclosed.

[0012] In DE 11 2012 004 377 T5, a device with a power converter circuit is described, consisting of a first active layer with a set of active devices and a first passive layer with a set of passive devices, as well as an intermediate connection that connects the devices arranged on the respective surfaces, wherein the surfaces are facing each other.

[0013] US Patent 2014 / 0043010A1 describes a DC-DC converter that receives one or more input voltages and generates one or more output voltages. It can operate with multiple voltage conversion ratios, the selection of which depends on the input. The converter can include multiple capacitors, inductors, and switches forming switched cells, in cascade, stack, or combinations thereof, with each cell capable of operating in multiple modes.

[0014] US Patent 8,619,445 B1 describes the detection of transient or fault conditions in a switching capacitor power converter by measuring internal voltages / currents at switching elements or phase nodes, or at the terminals, and comparing them with predefined ranges. In case of deviation, a fault control system modifies the operation, for example, by using a high-voltage switch to electrically disconnect certain switching elements from terminals or by adjusting the timing characteristics of the phase signals.

[0015] In JP H03-235 657 A, an arrangement with an inductor between several capacitors and an output capacitor is described. An output capacitor C3 is connected in parallel to capacitors C1 and C2, which are charged sequentially by a DC voltage source E; C3 is charged by C1 and C2. During the charging of C3, energy is stored in the inductor L and released to C3 from C1 / C2 during periods without charging.

[0016] US 2014 / 0184189A1 describes a DC-DC converter for converting multiple input voltages into multiple output voltages using multiple capacitors, inductors, and switches. The switches connect the capacitors to form a switching capacitor network with several distinguishable conversion ratios; the inductors enable continuous operation between these ratios, and the overall mode is selected depending on the input voltage.

[0017] This document addresses the aforementioned technical problem. Specifically, it deals with the technical problem of providing a power converter for relatively high input voltages and / or relatively high conversion ratios with reduced size and power dissipation. Summary

[0018] According to one aspect, a power converter (especially a switching power converter) is described which is designed to convert electrical power at an output voltage V. out at the output of the power converter from electrical power at an input voltage V into be derived at the input of the power converter. The input and output of the power converter typically each include a positive and a negative contact. The input voltage can correspond to the voltage between the positive and negative contacts at the input. The output voltage can correspond to the voltage between the positive and negative contacts at the output. The power converter can, in particular, be designed to charge a battery. Specifically, the power converter can be designed to supply a substantially constant charging current (for example, the reference current I). ref) to supply to a battery. The power converter includes an inductor (also called a coil) and a capacitor cell (which includes a capacitor, is equivalent to a capacitor, or includes a capacitive voltage divider), several switches (each including, for example, one or more metal-oxide-semiconductor transistors), and a controller (which includes, for example, a processor).

[0019] The controller is designed to control the multiple switches such that a commutation cycle of the power converter includes a first phase during which the capacitor cell and the inductor are connected in series. Furthermore, during the first phase, the magnitude of a voltage across the series connection of the capacitor cell and the inductor corresponds to the magnitude of (V in - V out In particular, the voltage across the series connection of the capacitor cell and the inductor V can be in - V outThis corresponds to the following: In other words, during the first phase, the capacitor cell and the inductor can be connected in series between the input voltage (and the input of the power converter) on one side and the output voltage (and the output of the power converter) on the other. As a result, the capacitor cell can be charged during the first phase.

[0020] Furthermore, the controller is designed to control the multiple switches such that the commutation cycle of the power converter includes a second phase during which the capacitor cell and the inductor are connected in series. Furthermore, during the second phase, the magnitude of the voltage across the series connection of the capacitor cell and the inductor corresponds to the magnitude of V. out In particular, the voltage across the series connection of the capacitor cell and the inductor can be -V outThis corresponds to the series connection of the capacitor cell and the inductor. In other words, the series connection of the capacitor cell and the inductor can be connected in parallel to the output voltage (and the output of the power converter). As a result, the capacitor cell can be discharged during the second phase.

[0021] Furthermore, the controller is designed to control the multiple switches in such a way that the commutation cycle of the power converter includes a third phase during which the capacitor cell is decoupled from the output of the power converter (e.g., the capacitor cell can be floating). During the third phase, the magnitude of a voltage across the inductor can equal the magnitude of (V in - V out ) or the amount of V out correspond. In particular, the voltage across the inductor V can in - V out or -V outTherefore, the third phase can include a first variant, during which the inductor is coupled to the input voltage (on one side of the inductor) and to the output voltage (on the other side of the inductor), and a second variant, during which the inductor is coupled to ground and to the output voltage, i.e., during which the inductor is connected in parallel with the output of the power converter.

[0022] The output voltage can be regulated to a predetermined reference voltage, for example V ref = V in / 2. V out can be any voltage smaller than V in Assume, but the controller regulates the duty cycle of the first and second phases so that the voltage across the capacitor V c above the capacitor cell ~ V in / 2. The highest implementation efficiency can usually be achieved for V out = Vc = V in / 2 can be achieved. The controller can be designed to adjust the duration of the first, second, and third phases during a commutation cycle (i.e., the duty cycle) so that the output voltage of the power converter matches the predetermined reference voltage V. ref is regulated.

[0023] The third phase can be used to adjust the (average) output current of the power converter to a predetermined reference current I. refto regulate. For this purpose, the output current of the power converter can be measured using current sensing devices, which may employ current sensing techniques such as matched filters and / or current mirroring. The output current at the end of the first and / or the second phase can be measured. In particular, the cumulative and / or average output current at the end of the first and / or the second phase can be measured. Furthermore, it can be determined whether the (cumulative / average) output current at the end of the first and / or the second phase is greater or less than the predetermined reference current I. refDepending on this comparison, either the first or the second variant can be used for a third phase that follows the first and / or second phase. In particular, the first variant can be used if the output current is below the predetermined reference current I. ref The second variant is used when the output current exceeds the predetermined reference current I. ref lies.

[0024] The controller can be designed to adjust the duration of the third phase such that at the end of the third phase the (average) output current is greater than or equal to the reference current I. ref is, in particular, when the (average) output current I out at the end of the first phase and / or at the end of the second phase, the current is smaller than the reference current I. refAlternatively or additionally, the controller can be designed to set the duration of the third phase such that the (average) output current I at the end of the third phase is... out less than or equal to the reference current I ref is, in particular, when the (average) output current I out at the end of the first phase and / or at the end of the second phase greater than the reference current I ref This allows for precise regulation of the output current.

[0025] The power converter allows the use of relatively small inductors. Furthermore, the power converter reduces voltage fluctuations across the inductor. Therefore, the power converter enables a reduction in both its size and power loss.

[0026] The controller can be designed to control the multiple switches so that the power converter operates in the third phase following the first phase and / or following the second phase within a single commutation cycle. Inserting the third phase following the first and following the second phase can reduce input voltage ripple.

[0027] The controller can be designed to set a duty cycle of a commutation cycle such that the input voltage V in greater than or equal to 2V out In particular, the duty cycle of a commutation cycle can be controlled so that the output voltage (on average) is lower than the reference voltage V. refThis corresponds, for example, to half the input voltage. The duty cycle can correspond to, or depend on, the ratio of the duration of the first phase to the duration of a complete commutation cycle, which includes the first phase, the second phase, and optionally one or more third phases.

[0028] The power converter can comprise a first sub-converter, which includes several first switches (for example, a subset of all the several switches) and a first capacitor cell (for example, a first capacitor). Furthermore, the power converter can comprise a second sub-converter, which includes several second switches (for example, a subset of all the several switches) and a second capacitor cell (for example, a second capacitor).

[0029] The first and second sub-converters can be operated in a nested manner, thereby reducing the ripple of the input voltage / current. Specifically, the controller can be configured to control multiple first and multiple second switches such that the first and second sub-converters operate in a nested manner. The nested operation can be such that during the first phase, the second capacitor cell is discharged; during the second phase, the first capacitor cell is discharged; and during the third phase, the first and second capacitor cells are decoupled from the output (e.g., floating). Furthermore, during the first phase, the first capacitor cell can be charged, and during the second phase, the second capacitor cell can be charged (as in the example of...). Fig. 1b). Alternatively, the first and second capacitor cells can be continuously charged with the same current during the first and second phases (as shown, for example, in the example of Fig. 4a is shown).

[0030] Furthermore, the controller can be designed to control the multiple first and second switches such that during the first and second phases, the first capacitor cell is connected in series with the inductor, and the second capacitor cell is also connected in series with the inductor. Therefore, the current through the inductor is supplied by both the first and second capacitor cells. Consequently, the power converter can comprise only a single inductor for both the first and second sub-converters. This further reduces the size of the power converter.

[0031] The multiple first switches can include a first switch designed to couple a first side of the first capacitor cell (directly) to the input voltage, a second switch designed to couple the first side of the first capacitor cell (directly) to the inductor, a third switch designed to couple a second side of the first capacitor cell (directly) to the inductor, and a fourth switch designed to couple the second side of the first capacitor cell (directly) to ground. Furthermore, the multiple second switches can include an eighth switch designed to couple a first side of the second capacitor cell (directly) to the input voltage, a seventh switch designed to couple the first side of the second capacitor cell (directly) to the inductor, and a sixth switch.The system includes a switch designed to couple a second side of the second capacitor cell (directly) to the inductor, and a fifth switch designed to couple the second side of the second capacitor cell (directly) to ground.

[0032] Alternatively, the first and second capacitor cells can be connected in series between the positive and negative contacts of the power converter input. One end of the first capacitor cell can be connected to the positive contact of the power converter input, the other end of the first capacitor cell can be connected to the first end of the second capacitor cell, and the other end of the second capacitor cell can be connected to the negative contact of the power converter input.The multiple switches can include a first switch designed to couple the second end of the first capacitor cell (directly) to the inductor, a second switch designed to couple the second end of the first capacitor cell (directly) to ground and / or the negative terminal of the power converter output, a third switch designed to couple the second end of the second capacitor cell (directly) to the negative terminal of the power converter output, and a fourth switch designed to couple the first end of the first capacitor cell (directly) to the inductor. Therefore, nested operation of the two sub-converters can be implemented with a reduced number of switches, thus reducing the size and power dissipation of the power converter.In particular, the two sub-converters, each comprising the two capacitor cells, use at least some of the same switches and / or include at least some of the same switches.

[0033] The power converter can include a first inductor and a second inductor. The controller can be configured to operate the multiple switches such that, during a first fraction of the first phase and a first fraction of the second phase, the capacitor cell is connected in series with the first inductor, while the second inductor is coupled to ground. Furthermore, the controller can be configured to operate the multiple switches such that, during a second fraction of the first phase and a second fraction of the second phase, the capacitor cell is connected in series with the second inductor, while the first inductor is coupled to ground. Finally, during a further fraction of the first phase and / or the second phase, the first and second inductors can be connected in parallel to each other and in series with the capacitor cell.By dividing the inductor into a first inductor and a second inductor, the conversion efficiency of the power converter can be further increased.

[0034] As stated above, a capacitor cell can comprise a single capacitor. Alternatively, a capacitor cell can comprise a capacitive voltage divider, such as a Dickson voltage divider, which includes multiple capacitors. In this way, different reference voltages V can be applied. ref must be provided for the output voltage, for example V ref = 2V in / 3, V in / 3, V in / 4 etc. The reference voltage V ref Specifies the output voltage at which the various power converters operate with optimal efficiency. Furthermore, the reference voltage V specifies refthe output voltage, in which the third phase of the operation of the power converter usually changes from a first variant to a second variant or vice versa.

[0035] The inductance L of an inductor, measured in Henrys, can be at least one or two orders of magnitude smaller than the capacitance C of a capacitor, measured in Farads. Therefore, a small, energy-efficient power converter can be provided.

[0036] According to another aspect, a cascaded power converter is described. The cascaded power converter comprises a power converter as described in this document. Furthermore, the cascaded power converter includes a capacitive voltage divider stage designed to derive the input voltage for the power converter from a global input voltage, where the global input voltage is greater than the input voltage. A commutation cycle of the capacitive voltage divider stage can be synchronized with a commutation cycle of the power converter. Furthermore, the frequency of the commutation cycle of the capacitive voltage divider stage can be k times lower than the frequency of the commutation cycle of the power converter, where k is a positive integer.By using a cascaded power converter, the power efficiency of a power converter can be optimized for conversion ratios of less than or equal to 0.25.

[0037] According to another aspect, a method for operating a controller of a power converter, as set out in this document, is described. The method may include steps corresponding to the characteristics of the controller and power converter described in this document. The method concerns the control of the switches of a power converter, wherein the power converter is designed to deliver electrical power at an output voltage V. out from electrical power at an input voltage V into derive, wherein the power converter comprises an inductor, a capacitor cell, and several switches. The method includes controlling the several switches such that a commutation cycle of the power converter includes a first phase during which the capacitor cell and the inductor are connected in series and during which a voltage V is applied across the series connection of the capacitor cell and the inductor. in - V out This corresponds to the method. Furthermore, the method includes controlling the several switches such that the commutation cycle of the power converter includes a second phase during which the capacitor cell and the inductor are connected in series and during which the voltage across the series connection of the capacitor cell and the inductor - V outThis corresponds to the method. Furthermore, the procedure includes controlling the multiple switches such that the commutation cycle of the power converter includes a third phase, during which the capacitor cell is potential-free and during which the voltage across the inductor V in - V out or -V out corresponds.

[0038] According to another aspect, a software program is described. The software program can be designed to run on a processor and, when run on the processor, to perform the procedure steps set out in this document.

[0039] According to another aspect, a storage medium is described. The storage medium may include a software program designed to run on a processor and, when run on the processor, to perform the procedure steps set out in this document.

[0040] According to another aspect, a computer program product is described. The computer program may include executable commands which, when executed on a computer, perform procedural steps as outlined in this document.

[0041] It should be noted that the methods and systems, including their preferred embodiments, as described in this document, may be used separately or in combination with other methods and systems disclosed herein. Furthermore, the features described in connection with a system are also applicable to a corresponding method. Moreover, all aspects of the methods and systems described in this document may be combined in any way. In particular, the features of the claims may be combined with one another in any manner.

[0042] In this document, the term “couple” or “coupled” refers to elements that are electrically connected to each other, whether directly, such as via wires, or in any other way. Brief description of the drawings Fig. 1a and Fig. 1b shows exemplary power converters; Fig. 2a and Fig. 2b shows exemplary voltages and currents at a power converter; Fig. Figures 3a to 3e show exemplary operating phases of a power converter; Fig. 4a to 4f show further examples of power converters; Fig. Figure 5 shows another exemplary power converter; Fig. Figure 6 shows a flowchart of an exemplary procedure for controlling a power converter. Detailed description

[0043] As outlined above, this document addresses the technical problem of providing power converters designed to handle an increased input voltage V. in and / or to handle increased input power, while still having a limited size and limited power loss.

[0044] In particular, this document aims to increase battery charging conversion efficiency (wired or wireless) to >93% in order to reduce power loss to a level that can be managed without overheating the electronic device. In this context, the negative impact on efficiency caused by charging device supply voltages that are significantly higher than the battery pack voltage is addressed. The challenge lies in working within the space constraints of the target electronic device, which typically requires the use of relatively small inductors. Furthermore, the input voltage ripple, which occurs due to the relatively low switching frequencies, should be reduced to achieve limited overshoot and limited electromagnetic interference emission from the wires to the electronic device's power supply.

[0045] As stated above, this document focuses specifically on battery charging. However, it should be noted that the disclosure in this document also applies to all applications requiring a high-efficiency DC-DC step-down converter, particularly when space constraints prevent the use of high-inductance coils for a low switching frequency.

[0046] One way to handle an increased input voltage is to use several buck converters in a cascade configuration. However, the efficiencies of cascaded stages are multiplied, resulting in a reduced overall efficiency in addition to increased cost and footprint. The disadvantages of cascaded converters can be mitigated by using unregulated switched capacitive voltage division within at least one of the stages, since capacitors are much smaller than inductors with similar energy storage capacity, and the conversion efficiency can reach up to 98–99%. A limitation of cascaded buck converters is the maximum conversion ratio, which is always lower than the conversion ratio of the individual stages. Thus, in the case of switched capacitive division, the maximum conversion ratio of the entire converter is lower than the conversion ratio of the divider cell (e.g., 1 / 2).The conversion ratio D < 0.5 when using a capacitive 2:1 divider stage. This prevents the use of cascaded converters for certain applications.

[0047] Another option is to use multi-stage buck converters. A multi-stage buck converter typically requires twice the number of switches as a conventional buck converter. However, at least the lower and middle switches (relative to ground) of a multi-stage buck converter are not exposed to voltages higher than VDS(on). in / 2 are, which allows the use of FETs with reduced voltage values, the lower input resistances R dsonwith similar parasitic capacitance and reduced reverse recovery losses. The reduced switching frequency of a multi-stage buck converter improves efficiency, but the duration of the time intervals is increased when no current is drawn from the input. For a 2:1 conversion ratio, the full output current is drawn from the input rail at a duty cycle of approximately 50%. In the case of a USB charging device, this increases the input voltage ripple, as the maximum connection capacitance is limited by the USB specifications.

[0048] Fig. Figure 1a shows a nested 3-stage buck converter 100. The nested 3-stage buck converter 100 comprises two instances or two sub-converters 110, 120 of a 3-stage buck converter 100, which are operated in a nested manner, thereby reducing the input voltage ripple. The structure of Fig. 1a can be achieved using a single inductor 104 (see Fig. 1b) instead of the separate inductors 112, 122 each for instances 110, 120, are made more compact in order to reduce the size of the nested 3-stage step-down converter 150 compared to the nested 3-stage step-down converter 100.

[0049] The power converter 150 from Fig. 1b reduces the input voltage ripple caused by a limited input capacitance at low switching frequencies. Furthermore, the power converter 150 requires only a single inductor 104.

[0050] Fig. 2a shows an example of an input voltage V in 201, an inductor current I L1 202, a capacitor voltage V C1 203 at the capacitor C1, an output current I out 204, an output voltage V out 205 and the control voltage 206 for the switches of the converter 110. Fig. 2b shows an example of an input voltage V in 201, an inductor current I L1 202, a capacitor voltage V C1 203 at the capacitor C1, an output current I out 204, an output voltage V out 205 and the control voltage 206 for the switches of converter 150. It is evident that, using the same total switching area, the voltage ripple of the input voltage 201 can be reduced to less than 10% when using converter 150. Furthermore, a symmetrical shape of the inductor current ripple can be achieved when using converter 150. In contrast, the inductor current signal of Fig. 2a differs slightly for successive switching cycles. This results from the fact that one of the inductor demagnetization phases discharges in parallel with the switching capacitor, while the subsequent inductor demagnetization phase simultaneously charges the switching capacitance.

[0051] The power converter 150 includes a control circuit (not shown) designed to control the switches S1 to S8 of the power converter 150. In particular, the switches can be operated such that the power converter 150 is successively switched to different phases. Examples of phases are shown in Fig. 3a to 3e are shown.

[0052] In the first phase, which takes place in Fig. As shown in 3a, all odd-numbered switches S1, S3, S5, and S7 are closed (whereas the even-numbered switches S2, S4, S6, and S8 are open). The first phase carries the inductor current I. L during the charging of the pump capacitor C1 from I in and the parallel discharge of the pump capacitor C2.

[0053] In a second phase, which takes place in Fig. As shown in Figure 3b, all odd-numbered switches S1, S3, S5, and S7 are open, while the even-numbered switches S2, S4, S6, and S8 are closed. The second phase carries the inductor current I. L during the charging of the pump capacitor C2 from I in and the parallel discharge of the pump capacitor C1.

[0054] The duration of the first and / or second phase can be controlled such that the charge of the two pump capacitors C1 and C2 is balanced. In the case of a constant output current, this condition results in identical durations for the first and second phases.

[0055] Furthermore, the multi-stage buck converter 150 is operated in a third phase to balance the current in the inductor L after the charging and discharging of the pump capacitor network C1, C2 is complete. For a steady state, two rules should be satisfied over a complete commutation cycle of the converter 150: 1. The charging and discharging of the pump capacitor network is equal (the capacitor charge and voltage are the same at the beginning and end of a cycle), i.e., 0 = ∫(I C x dt). 2. The current through the inductor L is the same at the beginning and at the end of the cycle, that is, 0 = ∫(dI L x dt).

[0056] The first condition can be achieved by adjusting the duration of the first and second phases. The second condition can be achieved using a third phase. In particular, the second condition can be achieved by operating the power converter 150 in either a first or second variant of a third phase. The first variant of the third phase is in Fig. 3c is shown and the second variant of the third phase is in Fig. 3D representation.

[0057] The third phase increases the current through the inductor without affecting the charge of the pump capacitors C1 and C2. The duration of the third phase can be determined by the target or reference output voltage V. ref (e.g. V in / 2) are regulated and, for a constant output current, generates the same inductor current I L at the beginning of each cycle (which consists of the first, second, and third phases). If V in > 2 x Vout The arrangement of is typically Fig. 3D selected (i.e., the first variant); otherwise, the arrangement of Fig. 3C selected (i.e., the second option).

[0058] The third phase can only be implemented after the second stage, or, with reduced inductor current ripple, it can also be inserted between the first and second phases. The inductor current ripple increases with the difference in V. out to their optimal value ½ x V in This ripple can be compensated for by increasing the switching frequency, but in both cases the conversion efficiency is reduced.

[0059] The converter 150 can be used in an optional fourth phase (in Fig. 3e shown) are operated in which the current through the inductor is zero and I outonly the output capacitor Cout supplies current. This phase can be used if the commutation cycle provides a higher average current than is drawn from the output. During the fourth phase, all switches can be open (at least switches S1, S4, S5, and S8). The fourth phase can be inserted when the inductor current IL crosses zero. The fourth phase can be described as a discontinuous conduction mode (DCM), pulse frequency modulation (PFM), or pulse suppression mode. The fourth phase regulates the output voltage / current by temporarily stopping the current through the inductor. The fourth phase can be terminated when V out (or I out ) has fallen below a minimum threshold (hysteresis control).

[0060] If there is a ground shift of the negative potential of the input voltage V in, which are connected to the negative potential of the output voltage V out If the circuit is linked and not relevant in a specific application, it can be used with circuit 400. Fig. 4a would be a sensible option. This implements input ripple cancellation with a reduced number of switches compared to the 150 power converter. The 400 power converter can be operated in at least three phases, as described in the context of the Fig. 3a to 3e is explained. A typical input for such a converter cell 400 is the rectifier output of an AC / DC converter or a wireless charging coil, as in circuit 410 of Fig. 4b shown.

[0061] Another variant of the circuit 150 according to the invention Fig. 1b is in Fig. 4c is shown. A typical application for the 420 circuit from Fig. 4c is, for example, the core power supply for low-voltage / high-performance application processors from a multi-cell battery pack (e.g., a 2-cell battery pack) (for example, with V bat ≥ 6 V, V out ≤ 1.5 V). The 420 power converter can be operated in at least three phases, as described in connection with Fig. Sections 3a to 3e are explained. The phases, especially the first and second phases, can be divided into different fractions, in which the respective inductors are connected in series with the capacitor. In other words, the inductors can be operated in a nested configuration. Furthermore, the inductors can be used simultaneously (for example, during another fraction of the first and / or the second phase).

[0062] Architecture 420 by Fig. The 4c ​​reduces the number of switching capacitors but uses several smaller inductors, each sized for a fraction of the maximum output current of the 420 converter. Switches S5 and S8 to ground allow independent switching and / or regulation of the first and second inductors L1 and L2 (including interleaved switching for ripple cancellation), improving conversion efficiency, especially at low output voltages. Switches S3 and S7 are connected in parallel with the 420 converter's switching capacitor. Line losses can be relatively low for the 420 converter because it has a reduced number of switches compared to other architectures, particularly between the inductor and the supply rails V. in and the mass.

[0063] Improved input ripple cancellation can be achieved when operating two 420 cells. Fig. 4c can be achieved in nested configurations, e.g. in the arrangement with four inductors 430, as in Fig. Shown in 4D.

[0064] An alternative example of a circuit 110 with optimized efficiency for a conversion ratio D ~ 0.25 and less is circuit 440 in Fig. Figure 4e shows the circuit 440, which includes a second-stage divider 441. The circuit 440 arranges a capacitive voltage divider 441 with a multi-stage buck converter in a cascade configuration. In a typical example, switches S5 and S7 change their state in parallel with switches S6 and S8, which is synchronized with the switching of the multi-stage buck converter at a rate that is half, or 1 / k, of its clock frequency. Thus, current is drawn from the input only in every second (or every k-th) cycle of the cascaded power converter 440.

[0065] The input current ripple caused by the converter time intervals during which no current is drawn from the input can be reduced by another exemplary converter 450 that connects two nested instances of the divider stage of the second stage 451, as in Fig. 4f shown. The converter 450 comprises two nested divider stages of the second stage 441, which are arranged in a cascade circuit with a three-stage buck converter 110, 451. The capacitors C2 and C3 in Fig. The 4f implement a voltage divider, with each supplying ~50% of the input current to the three-stage buck converter (where 50% is continuously from V). in (can be obtained).

[0066] To further reduce the input current / input voltage ripple, the three-stage step-down converters 451 shown above can be replaced by power converters, such as those found in Fig. 1a, Fig. 1b, Fig. 4a, Fig. 4b, Fig. 4c and Fig. Figure 4d shows the following. For improved efficiency at very low conversion ratios (e.g., D ≤ 0.125), the three-stage buck converter 451 can also be replaced with integrated circuits as shown in Figure 4d. Fig. 4e and Fig. 4f are shown.

[0067] The capacitive cell(s) mentioned in the previous examples of Fig. The topologies shown in 1a, 1b, 4a to 4f can be replaced with other topologies such as a serial-parallel topology, a Dickson topology, etc., thereby achieving optimal implementation efficiency even with divisor ratios of, for example, 3:1, 1.5:1 (especially different from 2 n :1) is made possible. As an example, the circuit replaces 500 of Fig. 5 the switching capacitors C1 and C2 of Fig. 1a with two 3:1 cells of a Dickson topology.

[0068] The power converters described in this document can employ relatively low-frequency switching to achieve highly efficient battery charging (wired and wireless) from input voltages significantly higher than the output voltage used to charge a battery pack. The input voltage ripple of the power converters can be improved simply by using a small inductor at low switching frequencies. The power converters can be implemented on a printed circuit board (PCB).

[0069] A multi-stage buck converter combined with small, low-inductance coils is described for charging batteries. Furthermore, low input current / voltage ripple can be achieved with a low-frequency multi-stage buck converter in combination with a single small inductor and low input capacitance.

[0070] Using multi-stage switching cells for step-down conversion of battery charging from input voltages significantly higher than the battery pack voltage enables a low switching frequency combined with low inductance (small coils). The low switching frequency increases conversion efficiency (reduces power loss). The described architecture adds ripple cancellation to multi-stage step-down converter cells without requiring multiple inductors. Furthermore, automatic charge regulation can be achieved via the switching capacitance, eliminating the need for a separate control circuit.

[0071] Fig. Figure 6 shows a flowchart of an exemplary procedure 600 for controlling a power converter 150. The power converter is designed to convert electrical power at an output voltage V. out from electrical power at an input voltage V into derive, wherein the power converter 150 comprises an inductor L, a capacitor cell C1, C2 and several switches S1, S2, S3, S4, S5, S6, S7, S8.

[0072] The method 600 comprises controlling 601 of the several switches such that a commutation cycle of the power converter 150 includes a first phase during which the capacitor cell and the inductor are connected in series and during which a voltage V is applied across the series connection of the capacitor cell and the inductor. in - V out corresponds. Furthermore, the method 600 comprises controlling 602 the several switches such that the commutation cycle of the power converter includes a second phase during which the capacitor cell and the inductor are connected in series and during which the voltage across the series connection of the capacitor cell and the inductor -V outThis corresponds to the method 600. In addition, the method 603 includes controlling the several switches such that the commutation cycle of the power converter includes a third phase, during which the capacitor cell is potential-free and during which the voltage across the inductor V in - V out or -V out This corresponds to the following: By controlling the power converters according to Method 600, the ripple of the input voltage / input current can be reduced. Furthermore, the use of a capacitor cell in conjunction with an inductor allows the use of inductors with reduced inductance, thus providing smaller power converters. Additionally, the power losses of the power converter can be reduced.

[0073] It should be noted that the description and drawings merely illustrate the principles of the proposed methods and systems. Those skilled in the art will be able to implement various arrangements which, although not explicitly described or shown here, embody the principles of the invention and are contained within its concept and scope. Furthermore, all examples and embodiments presented in this document are provided primarily and expressly for illustrative purposes only, to assist the reader in understanding the principles of the proposed methods and systems. Moreover, all statements made herein that provide principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to include their equivalents.

Claims

[1] Electronic device comprising a rechargeable battery and a voltage- or current-controlled power converter (150) for charging the battery, wherein the power converter (150) is designed to provide electrical power at an output voltage V out to charge the battery at an output of the power converter (150) from electrical power at an input voltage V into be derived at an input of the power converter (150), wherein the power converter (150) comprises an inductor (L), a first sub-converter (110) with several first switches (S1, S2, S3, S4) and a first capacitor cell (C1), and a second sub-converter (120) with several second switches (S5, S6, S7, S8) and a second capacitor cell (C2); wherein the power converter (150) comprises only a single inductor for the first sub-converter and for the second sub-converter, and a controller; wherein the controller is configured to control the several first and the several second switches such that the first and the second sub-converter are operated in a nested manner, and wherein a commutation cycle of the power converter comprises: - a first phase, during which the first capacitor cell and the inductor are connected in series between the input and the output of the power converter (150), and during which the second capacitor cell and the inductor are connected in series in parallel with the output of the power converter (150); - a second phase, during which the first capacitor cell and the inductor are connected in series in parallel with the output of the power converter (150), and during which the second capacitor cell and the inductor are connected in series between the input and the output of the power converter (150); and - a third phase, during which the first and second capacitor cells are decoupled from the output of the power converter (150), during which the charge of the first and second capacitor cells remains unchanged, and during which the inductor is arranged between the input and the output of the power converter (150) or is connected in parallel to the output of the power converter (150), wherein the controller is designed to control the multiple first and second switches in such a way that the power converter is operated in the third phase following the first phase and / or following the second phase within one commutation cycle, and wherein The controller is designed to do the following: - Determining an output current I out at the end of the first phase and / or at the end of the second phase; - Control the several first and second switches during the third phase such that the inductor is then arranged between the input and the output of the power converter (150) when the output current I out at the end of the first phase and / or at the end of the second phase less than a reference current I ref is; and - Control the several first and second switches during the third phase such that the inductor is then connected in parallel to the output of the power converter (150) when the output current I out at the end of the first phase and / or at the end of the second phase greater than the reference current I ref is. [2] Device according to claim 1, wherein the controller is designed to set a duration of the third phase such that at the end of the third phase - the output current I out then greater than or equal to the reference current Iref is when the output current I out at the end of the first phase and / or at the end of the second phase less than a reference current I ref is; and - the output current I out then less than or equal to the reference current I ref is when the output current I out at the end of the first phase and / or at the end of the second phase greater than a reference current I ref is. [3] Device according to one of the preceding claims, wherein - during the first phase the first capacitor cell is charged and the second capacitor cell is discharged; - during the second phase, the first capacitor cell is discharged and the second capacitor cell is charged. [4] Device according to one of the preceding claims, wherein - the multiple first switches comprise a first switch designed to couple a first side of the first capacitor cell to the input voltage, a second switch designed to couple the first side of the first capacitor cell to the inductor, a third switch designed to couple a second side of the first capacitor cell to the inductor, and a fourth switch designed to couple the second side of the first capacitor cell to ground; - the multiple second switches include an 8th switch (S8) designed to couple a first side of the second capacitor cell to the input voltage, a 7th switch (S7) designed to couple the first side of the second capacitor cell to the inductor, a 6th switch (S6) designed to couple a second side of the second capacitor cell to the inductor, and a 5th switch (S5) designed to couple the second side of the second capacitor cell to ground. [5] Device according to any one of claims 1 to 3, - wherein the first and second capacitor cells are connected in series between a positive and a negative contact of the input voltage; - wherein a first end of the first capacitor cell is coupled to the positive contact of the input voltage; - wherein a second end of the first capacitor cell is coupled to a first end of the second capacitor cell; - wherein a second end of the second capacitor cell is coupled to the negative contact of the input voltage; and - which include several switches: - a first switch designed to couple the second end of the first capacitor cell to the inductor, - a second switch designed to couple the second end of the first capacitor cell to ground, - a third switch designed to couple the second end of the second capacitor cell to ground, and - a fourth switch designed to couple the first end of the first capacitor cell to the inductor. [6] Device according to one of the preceding claims, wherein - the first capacitor cell comprises a single capacitor; or - the first capacitor cell includes a capacitive voltage divider such as a Dickson voltage divider, which consists of several capacitors. [7] Device according to one of the preceding claims, wherein the inductance L of the inductor, measured in Henry, is at least one or two orders of magnitude smaller than the capacitance C of the capacitor, measured in Farad. [8] Device according to any of the preceding claims, further comprising: - a capacitive voltage divider stage designed to derive the input voltage for the power converter from a global input voltage; - where the global input voltage is greater than the input voltage; - a commutation cycle of the capacitive voltage divider stage is synchronized with a commutation cycle of the power converter; and - a frequency of the commutation cycle of the capacitive voltage divider stage is k times smaller than a frequency of the commutation cycle of the power converter, where k is an integer. [9] Method (600) for charging a battery using a power converter (150), wherein the power converter is designed to deliver electrical power at an output voltage V out from electrical power at an input voltage V in to derive, wherein the power converter (150) comprises an inductor (L), a first sub-converter (110) with several first switches (S1, S2, S3, S4) and a first capacitor cell (C1), and a second sub-converter (120) with several second switches (S5, S6, S7, S8) and a second capacitor cell (C2); wherein the power converter (150) comprises only a single inductor for the first sub-converter and for the second sub-converter, and a controller; wherein the method (600) comprises - Control (601) the several first and second switches such that a commutation cycle of the power converter includes a first phase during which the first capacitor cell and the inductor are connected in series between the input and the output of the power converter (150), and during which the second capacitor cell and the inductor are connected in series in parallel with the output of the power converter (150); - Controlling (602) the multiple first and second switches such that the commutation cycle of the power converter includes a second phase during which the first capacitor cell and the inductor are connected in series in parallel with the output of the power converter (150), and during which the second capacitor cell and the inductor are connected in series between the input and the output of the power converter (150); and - Controlling (603) the multiple first and second switches such that the commutation cycle of the power converter includes a third phase during which the first and second capacitor cells are decoupled from the output of the power converter (150), during which a charge of the first and second capacitor cells remains unchanged, and during which the inductor is arranged between the input and the output of the power converter (150) or is connected in parallel to the output of the power converter (150), wherein the multiple first and second switches are controlled such that the power converter is operated in the third phase following the first phase and / or following the second phase within one commutation cycle, and the method comprises the following steps: - Determining an output current I out at the end of the first phase and / or at the end of the second phase; - Control the several first and second switches during the third phase such that the inductor is then arranged between the input and the output of the power converter (150) when the output current I out at the end of the first phase and / or at the end of the second phase less than a reference current I ref is; and - Control the several first and second switches during the third phase such that the inductor is then connected in parallel to the output of the power converter (150) when the output current I out at the end of the first phase and / or at the end of the second phase greater than the reference current I ref is.

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