HIGHLY EFFICIENT REGULATED HYBRID CONVERTER WITH MULTIPLE CAPACITIVE CURRENT-CARRYING BRANCHES

Abstract

A power converter configured to receive an input voltage via a voltage input terminal and output a predetermined output voltage via a voltage output terminal, comprising: two or more voltage rail providing cells connected between the voltage input terminal and ground; a switching network comprising a plurality of switches and configured to create a current path through the two or more voltage rail providing cells such that the two or more voltage rail providing cells provide two or more voltage rails each corresponding to a predetermined input-output voltage difference;At least one power storage cell connected between the two or more voltage rail providing cells and the voltage output terminal, wherein the at least one power storage cell is configured to output the predetermined output voltage to the voltage output terminal; A control circuit configured to control the switching network to select at least one of the two or more voltage rails to set the predetermined output voltage.

Description

[0001] The present disclosure relates to a power converter. In particular, the present disclosure relates to a power converter configured to receive an input voltage and output a predetermined output voltage via energy storage elements. BACKGROUND

[0002] Recently, the demand for high-efficiency power converter solutions has increased. In some cases, this requires doubling the output power capability while maintaining the overall thermal budget. In the consumer electronics sector, every square millimeter of PCB area is considered, and thus, minimal silicon die area and a low number of external components are critical when considering new solutions.

[0003] To increase power delivery capability while minimizing input current, one common solution is to increase the input voltage. However, this can increase power stage losses. Therefore, efficient power conversion with a higher step ratio (the ratio of input voltage to output voltage), with increased input voltage levels and low output voltage levels (e.g., 20 / 24 / 28V input voltage levels to 1-4.8V output voltage range) is required.

[0004] The present invention relates to power conversion topologies and control methodology, of which there are two common approaches: inductor-based converters (such as buck converters) and capacitor-switching power converters (such as the Dickson converter).

[0005] Inductor-based switching power converters maintain a well-regulated output voltage over a wide input voltage range, but are difficult to integrate and have higher density / power because they require a power inductor.

[0006] Capacitor switching converters do not use a power inductor, have a smaller area and better energy storage density, but are limited to providing a fixed reduction ratio with the output voltage following the input voltage and do not provide a regulated output voltage.

[0007] Fig. Figure 1 shows a circuit diagram of a capacitor-switching power converter, specifically a 4:1 Dickson converter. The power converter is a single power stage that produces a fixed (unregulated) reduction ratio.

[0008] Alternatively, a two-stage cascaded power conversion approach can be used to exploit the positive characteristics of both the capacitor-switching power converter and the inductor-based power converter.

[0009] Fig. Figure 2 shows a block diagram of a two-stage cascaded power converter in which a capacitor-switching power converter circuit provides a first stage to lower an initial input voltage rail, and wherein an intermediate voltage rail is input to an inductor-based power converter in a second stage, wherein the inductor-based power converter is used to provide a necessary regulated output voltage over the entire input voltage range.

[0010] Although the two-stage cascaded solution takes a path to exploit the positive characteristics of the capacitor-switching power converter and the inductor-based power converter, it requires additional PCB area and has inherent power losses associated with each stage, reducing the overall operating efficiency. SUMMARY

[0011] It is desirable to provide an improved power converter.

[0012] According to a first aspect of the disclosure, there is provided a power converter configured to receive an input voltage via a voltage input terminal and output a predetermined output voltage via a voltage output terminal, comprising: two or more voltage rail supply cells connected between the voltage input terminal and ground; a switching network comprising a plurality of switches and configured to create a current path through the two or more voltage rail providing cells such that the two or more voltage rail providing cells provide two or more voltage rails each corresponding to a predetermined input-output voltage difference; at least one power storage cell connected between the two or more voltage rail providing cells and the voltage output terminal, the at least one power storage cell configured to output the predetermined output voltage to the voltage output terminal; a control circuit configured to control the switching network to select at least one voltage rail of the two or more voltage rails to set the predetermined output voltage.

[0013] Optionally, the two or more voltage rail supply cells are two or more capacitor cells.

[0014] Optionally, the at least one power storage cell is at least one inductor cell.

[0015] Optionally, each of the two or more voltage rails is provided by two of the two or more capacitor cells.

[0016] Optionally, the power converter of claim 1, wherein the switching network creates the current path through the two or more voltage rail providing cells by switching each of the voltage rail providing cells to be connected to ground or the voltage output terminal; wherein each voltage rail providing cell is switchably connected to ground and the voltage output terminal.

[0017] Optionally, the selected at least one voltage rail is connected in series to provide the predetermined output voltage across the power storage cell.

[0018] Optionally, an additional voltage rail is added by connecting two additional voltage rail provision cells.

[0019] Optionally, each capacitor cell includes the following: a capacitor; and at least one capacitor connection switch of the switching network, wherein the at least one capacitor connection switch connects the capacitor to one of the two or more voltage rails.

[0020] Optionally, each voltage rail supply cell includes a first inductor.

[0021] Optionally, the switching network includes the following: three voltage input switches, two of the voltage input switches connecting an input voltage terminal to a capacitor of one of the two or more capacitor cells and a third voltage input switch connecting the input voltage terminal to the inductor cell; and a plurality of output voltage switches, the output voltage switches connecting the first set of capacitors and the second set of capacitors to the output voltage; and a plurality of ground switches, the ground switches connecting the first set of capacitors and the second set of capacitors to ground.

[0022] Optionally, the control circuit controls the switching network to operate in a first mode in a first phase and in a second mode in a second phase.

[0023] Optionally, the control circuit controls the switching network to switch between the first mode and the second mode.

[0024] Optionally, a first set of capacitors of the two or more capacitor cells is charged in the first mode and discharged in the second mode; and a second set of capacitors of the two or more capacitor cells is charged in the second mode and discharged in the first mode.

[0025] Optionally, the first set of capacitors is charged simultaneously in the first mode; the second set of capacitors is charged simultaneously in the second mode; and the first set of capacitors provides the two or more voltage rails in the first mode and the second set of capacitors provides the two or more voltage rails in the second mode.

[0026] Optionally, the first mode includes the following: Charging the first set of capacitors; and Discharging the second set of capacitors to charge at least one capacitor of the first set of capacitors and / or to magnetize a second inductor of the inductor cell; and the second mode comprising: Charging the second set of capacitors; and Discharging the first set of capacitors to charge at least one capacitor of the second set of capacitors and / or to magnetize the second inductor of the inductor cell.

[0027] Optionally, in the first mode, the second inductor is connected between the voltage output terminal and one of the two or more voltage rails, such that the second inductor is magnetized according to a potential difference between the voltage rail and the voltage output terminal; and In the second mode, the second inductor is connected between the voltage output terminal and another of the two or more voltage rails, so that the second inductor is magnetized according to a potential difference between the voltage rail and the voltage output terminal.

[0028] Optionally, the first mode and the second mode each comprise a second step; and the second step of the first mode and the second mode includes: Demagnetizing the inductor of the inductor cell; and Reducing a current applied across the inductor of the inductor cell.

[0029] Optionally, the charging and discharging of the first set of capacitors and the second set of capacitors is controlled by turning the switches of the switching network on and off.

[0030] Optionally, the charging of a first capacitor of the first set of capacitors is controlled by turning on one of the voltage input switches and connecting the first capacitor between the input voltage and the output voltage; the charging of the other capacitors of the first set of capacitors is controlled by turning on the at least one capacitor connection switch and connecting the first set of capacitors to the second set of capacitors; the charging of a second capacitor of the second set of capacitors is controlled by turning on one of the voltage input switches and connecting the second capacitor between the input voltage and the output voltage; and the charging of the other capacitors of the second set of capacitors is controlled by turning on the at least one capacitor connection switch and connecting the second set of capacitors to the first set of capacitors.

[0031] Optionally, the two or more capacitor cells are interconnected by a first plurality of switches of the switching network.

[0032] Optionally, the two or more capacitor cells are distributed on both sides of the inductor cell so that an equal number of capacitor cells are positioned on a left side and a right side of the inductor cell.

[0033] Optionally, the power converter includes six capacitor cells and one inductor cell.

[0034] According to a second aspect of the disclosure, a method is provided for adjusting an output voltage using a power converter configured to receive an input voltage via a voltage input terminal and output a predetermined output voltage via a voltage output terminal, the power converter comprising two or more voltage rails, the method comprising: Controlling, by a control circuit, a switching network comprising a plurality of switches to create a current path through two or more voltage rail providing cells such that the two or more voltage rail providing cells provide two or more voltage rails, each voltage rail corresponding to a predetermined input-output voltage difference; Selecting, by the control circuit, at least one voltage input rail of the two or more voltage input rails to set a predetermined output voltage; Outputting, by a power storage cell connected between the two or more voltage rail providing cells and a voltage output terminal, the predetermined output voltage to the voltage output terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The disclosure will now be described in more detail by way of example and with reference to the accompanying drawings, in which: Fig. Figure 1 shows a capacitor switching power converter as known in the prior art; Fig. Figure 2 shows a two-stage power converter as known in the prior art; Fig. 3 shows a block diagram illustrating a power converter; Fig. Figure 4 shows a block diagram illustrating a power converter; Fig. Figure 5 shows a circuit diagram illustrating a power converter; Fig. 6A and Fig. 6B shows a circuit diagram illustrating a first switching sequence of a power converter; Fig. 6C and Fig. 6D shows a circuit diagram illustrating a second switching sequence of a power converter; Fig. Figure 7 shows a circuit diagram illustrating a power converter; Fig. Figure 8 shows a circuit diagram illustrating a power converter; Fig. 9A shows a diagram illustrating waveforms of a power converter; and Fig. Figure 9B shows a diagram illustrating waveforms of a power converter. DETAILED DESCRIPTION

[0036] Fig. 3 shows a block diagram illustrating a power converter 300 according to a first embodiment. The power converter 300 is configured to receive an input voltage via a voltage input terminal and to output a predetermined output voltage via a voltage output terminal. The power converter 300 includes at least one voltage input terminal configured to receive an input voltage (for example, the input voltage may be a predetermined input voltage or may be variable), at least one voltage output terminal configured to output an output voltage (for example, the output voltage may be a regulated output), two or more voltage rail provision cells (or modules or circuits) 301, a control circuit 303, a switching network 305 comprising a plurality of switches, and configured toto create a current path through the two or more voltage rail providing cells 301 such that the two or more voltage rail providing cells provide two or more voltage rails each corresponding to a predetermined input-output voltage difference, and at least one power storage cell (or module or circuit) 307 connected between the two or more voltage rail providing cells and the voltage output terminal, wherein the control circuit 303 is configured to control the switching network to select at least one voltage rail of the two or more voltage rails to set a predetermined output voltage.

[0037] For example, power converter 300 may be a hybrid power converter circuit. The two or more voltage rail supply cells may be two or more flying capacitor voltage rail supply cells. The two or more voltage rail supply cells may be two or more capacitor cells. The at least one power storage cell may be at least one inductor cell.

[0038] The two or more voltage rails are provided by the two or more voltage rail provision cells. More specifically, each of the two or more voltage rails is provided by two of the two or more voltage rail provision cells. That is, the voltage rail provision cells are paired such that, for example, C1 = C3 = Vin-Vout; thus, C1 and C3 provide a voltage rail with a potential difference of Vin-Vout.

[0039] The control circuit 303 is configured to select at least one of the two or more voltage rails to set a predetermined (or desired or preset) output voltage. For example, each voltage rail may represent a specific potential difference provided by each voltage rail providing cell; thus, multiple voltage rails may be selected to set a specific output voltage. For example, the number of individual voltage rails may be selected depending on the input voltage variance of the input voltage and the output voltage and a regulation tolerance. The selected at least one voltage rail is connected in series to provide the predetermined output voltage across the power storage cell. The control circuit 303 may be a driver circuit or the like.

[0040] The voltage input terminal may be shared by the two or more voltage rail provision cells 301 and the at least one power storage cell 307. The voltage output terminal may be shared by each of the two or more voltage rail provision cells 301 and the at least one power storage cell 307. For example, the bottom plate of each capacitor of the two or more voltage rail provision cells 301 may be switchably connected to ground (i.e., connected with a switch therebetween) and separately to the voltage output terminal.

[0041] The two or more voltage rails are provided by the two or more voltage rail provision cells 301 and the switching network 303, with the switching network 305 configured to control the provision of current to each of the two or more voltage rail provision cells 301. Each voltage rail provision cell serves as a current path acting as a voltage rail. The plurality of switches of the switching network 305 can be opened or closed (turned on or off) to control which voltage rail provision cells 301 are charged or discharged at different times. Thus, additional voltage rails can be added by connecting two additional voltage rail provision cells 301. The switching network 305 is controlled by the control circuit 303.

[0042] For example, the control circuit 303 may control the switching network 305 to operate (or implement) a switching sequence that causes a first set of capacitors (or other power storage device) of the two or more voltage rail provision cells 301 to charge while a second set of capacitors of the two or more voltage rail provision cells 301 discharges, or vice versa. The capacitors of the two or more voltage rail provision cells may be flying capacitors. Discharging the second set of capacitors may charge some of the first set of capacitors, or vice versa. For example, a first capacitor may be charged at a first time and may discharge at a second time.At the first time, the first capacitor may either be charged directly from Vin or may be charged by discharging a second capacitor (i.e., the first capacitor is charged by current received from the discharging second capacitor); at the second time, the first capacitor may discharge to charge a third capacitor or may discharge to magnetize an inductor of the inductor cell 307. In some examples, the switches of the switching network 305 may be field-effect transistors (FETs).

[0043] In some examples, the two or more voltage rail provision cells 301 may be switched capacitor circuits. For example, the two or more voltage rail provision cells may be switched capacitor circuits similar to the Fig. 1 shown switched capacitor circuit (state of the art).

[0044] In one example, each of the two or more voltage rails can be set to a different input-output voltage difference (the difference between the input voltage and the output voltage—for example, an intermediate input-output voltage difference) by providing it through the two or more voltage rail provision cells 301. Across the input voltage range, various combinations of the two or more voltage rails can be connected in series to provide a regulated voltage output. Thus, the voltage output can be regulated over a wide input voltage range by using combinations of the two or more voltage rails.For example, the two or more voltage rails may include four voltage rails, where the four voltage rails have voltages corresponding to "Vin" (input voltage), "Vin-Vout" (where Vout is the output voltage), "Vin-2Vout" (where 2Vout is 2 times Vout), and "Vin-3Vout" (where 3Vout is 3 times Vout). In this example, six voltage rail supply cells may be provided to continuously supply the four voltage rails.

[0045] In some examples, the power converter may be a circuit that is symmetrical, such that an equal number of voltage rail provision cells are positioned on one side of the at least one power storage cell and another side of the power storage cell. That is, the two or more capacitor cells are distributed on both sides of the at least one inductor cell, such that an equal number of capacitor cells are positioned on a left side and a right side of the inductor cell.

[0046] Fig. Fig. 4 shows a block diagram illustrating a power converter 400 according to the first embodiment. The power converter may be the same as the power converter 300 described with reference to Fig. 3 is described.

[0047] The power converter comprises two or more voltage rails; two or more capacitor cells (or circuits or modules) 401 (e.g., capacitor cells C1, C2 to capacitor cell Cn); a switching network 403; a control circuit (or controller) 405; at least one inductor cell 407 (e.g., inductor cells L1, L2 to inductor cell Lm); input voltage Vin; output voltage Vout; and switch S GND and S VOUT .

[0048] The power converter may be scalable. Specifically, the number of voltage rails may be increased by adding two additional capacitor cells 401 for each additional voltage rail. For example, to add one additional voltage rail, two additional capacitor cells may be connected. In another example, to add two additional voltage rails, four additional capacitor cells may be added. Additionally, additional inductor cells 407 may also be added.

[0049] In a preferred example, power converter 400 may include four voltage rails provided by six capacitor cells and one inductor cell. However, it should be understood that the number of capacitor cells and inductor cells may be varied based on desired input-output voltage ratios. For example, eight capacitor cells may be used to provide five voltage rails (Vin, Vin-Vout, Vin-2Vout, Vin-3Vout, Vin-4Vout), or four capacitor cells may be used to provide three voltage rails (Vin, Vin-Vout, Vin-2Vout).

[0050] Each capacitor cell of the two or more capacitor cells 401 may comprise a capacitor and at least one capacitor connection switch of the switching network 403, wherein the at least one capacitor connection switch connects the capacitor to one of the two or more voltage rails (for example, by connecting it to an adjacent capacitor cell of the two or more capacitor cells 401). The capacitor cells are connected by switches S GND and S VOUT connected to ground and the output voltage. For example, the base plate of each capacitor of each capacitor cell is switchably connected to both ground and the output voltage. For example, each capacitor can be switchably connected to ground and the output voltage by two switches per capacitor, or the two switches can be shared by a plurality (or group, or set, or number) of capacitors.

[0051] In a preferred example, each capacitor cell of the two or more capacitor cells 401 includes a capacitor, a switch connecting the capacitor to ground, a switch connecting the capacitor to V out , and a switch connecting the capacitor either to another capacitor belonging to another capacitor cell or to at least one inductor cell 407. However, fewer switches may be used, as described with reference to Fig. 5 described.

[0052] In alternative examples, each capacitor cell may also include an inductor (as in Fig. 7). These inductors enable smooth charging of the capacitors and prevent redistribution current peaks during the transfer of energy between capacitors. For example, the inductors can be parasitic inductors. This is further explained with reference to Fig. 9A and Fig. 9B.

[0053] Fig. 5 shows a power converter 500 according to a second embodiment. For example, the power converter may be another example of the power converters 300, 400 described with reference to Fig. 3 and Fig. 4 are described.

[0054] In this embodiment, power converter 500 includes six capacitor cells, each capacitor cell including a capacitor 501-1 through 501-6 and a switch, the switches being part of a switching network (such as switching network 303 or 403). The capacitors are connected such that a first set of capacitors 501-1, 501-3, 501-5 is switchably connected to Vout and ground; and such that a second set of capacitors 501-2, 501-4, 501-6 is separately switchably connected to Vout and ground. That is, switch 503-11 is connected between the first set of capacitors 501-1, 501-3, 501-5 and Vout and switch 503-13 is connected between the second set of capacitors 501-2, 501-4, 501-6 and Vout, allowing the switching network to form a current path through each capacitor to provide a voltage rail.Additionally, switch 503-12 is connected between the first set of capacitors 501-1, 501-3, 501-5 and ground, and switch 503-14 is connected between the second set of capacitors 501-2, 501-4, 501-6 and ground. This allows the control circuit to control the switching network to allow the first set of capacitors 501-1, 501-3, 501-5 and / or the second set of capacitors 501-2, 501-4, 501-6 to discharge to ground by controlling the switching network such that the first or second set of capacitors is connected to ground.

[0055] The switching network includes switches 503-1 to 503-14. The switching network is controlled by a control circuit (not shown) such as control circuits 305, 405, as described with reference to Fig. 3 and Fig. 4 described.

[0056] That is, the switching network comprises three voltage input switches 503-1, 503-5, 503-9, wherein two of the three voltage input switches 503-1, 503-9 connect the input voltage to the capacitor cells 501-1 and 501-6. Another voltage input switch 503-5 connects the input voltage to the inductor 507. The switching network also comprises at least two output voltage switches 503-11 and 503-13, wherein the at least two output voltage switches connect the first set of capacitors 501-1, 501-3, and 501-5 and the second set of capacitors 501-2, 501-4, and 501-6 to the output voltage Vout; and at least three ground switches 503-10, 503-12 and 503-14 connecting the first set of capacitors, the second set of capacitors and the inductor 507 to ground.

[0057] In alternative examples, the switching network may include a larger number of switches. For example, in a preferred example, each capacitor cell may include a switch for connecting the capacitor to ground and a switch for connecting the capacitor to Vout. In another alternative example, the power converter may be symmetrical, and capacitors of each group on each side may share switches for connecting the capacitors to ground and Vout (as described with reference to Fig. 8).

[0058] The control circuit can control the switching network to operate in a first mode in a first phase and in a second mode in a second phase. More specifically, the switching network can be controlled by the control circuit such that in a first phase, a first plurality of switches of the switching network are closed (or turned on), thereby allowing the first set of capacitors to be charged, and in a second phase, a second plurality of switches of the switching network are closed (or turned on), thereby allowing the second set of capacitors to be charged. The first set of capacitors can discharge in the second phase, and the discharged current can charge the second set of capacitors. The second set of capacitors can discharge in the first phase, and the discharged current can charge the first set of capacitors.The control circuit can control the switching network to switch between the first mode and the second mode.

[0059] Thus, the switching network can be controlled (by the control circuit) to provide a set of voltage rails that can be selected to provide a predetermined output voltage.

[0060] That is, each capacitor cell serves as a current path that acts as a voltage rail. Thus, the capacitor cells can be replicated to provide additional voltage rails. Thus, the power converter 500 is scalable, allowing as many or as few voltage rails as needed to achieve a desired input-to-output ratio.

[0061] The power converter 500 further includes an inductor cell (for example, the inductor cell may be the same or similar to the inductor cells 307, 407 described with reference to Fig. 3 and Fig. 4), which includes an inductor 507 and switches 503-4, 503-5, 503-6, 503-10. Switch 503-5 connects inductor 507 to voltage Vin, so that when the potential stored on the capacitor cell (for example, Vin-3Vout for capacitor 501-3) directly connected to the inductor cell falls below Vout, switch 503-5 allows inductor 507 to access Vin as a pull-up voltage that can be used to magnetize the inductor. The inductor 507 of the inductor cell is magnetized by current discharged through capacitors 501-3 and / or 501-4 to produce a desired output voltage.

[0062] Fig. Figure 5 shows an example of a power converter with a minimal number of switches. It should be understood that other examples may include a larger number of switches (as in Fig. 7 and Fig. 8).

[0063] Fig. 6A, Fig. 6B, Fig. 6C and Fig. 6D show an example of a power converter, such as those described with reference to Fig. 3, Fig. 4 and Fig. 5, which operate in a first mode and a second mode, respectively. For example, the hybrid power converter circuit may operate in the first mode during a first phase and in the second mode during a second phase. The first mode and the second mode may be alternated; for example, the hybrid power converter circuit may operate in the first mode, followed by the second mode, followed by the first mode, and so on. The first mode and the second mode may both include a first step and a second step.

[0064] Fig. Figure 6A shows the power converter operating in a first mode, where the power converter performs a first step of the first mode. In the first step of the first mode, switches S1A, S3A, S5A, S7A, and S9A (all odd-numbered switches on a left side of the inductor cell) and S2B, S4B, S6B, S8B, and S10B (all even-numbered switches on a right side of the inductor cell) are closed (or turned on), allowing capacitors CA-1, CA-3, and CB-2 to be charged simultaneously.

[0065] More specifically, on the left side of the inductor cell, switches S1A and S3A are closed (turned on), connecting capacitor CA-1 between Vin and Vout and charging the capacitor to Vin-Vout. At the same time, switches S7A, S5A, and S9A are closed (turned on), connecting capacitors CA-2 and CA-3 and allowing charge to be transferred from CA-2 to CA-3 (i.e., capacitor CA-2 discharges and capacitor CA-3 charges). In this example, capacitor CA-2 was previously charged to Vin-2Vout in a previous mode, causing capacitor CA-3, connected to Vout by switch S9A, to be charged to a potential of Vin-3Vout.

[0066] On the right side of the inductor cell, switches S2B, S4B, and S6B are closed (turned on), connecting capacitors CB-3 and CB-2 and allowing charge to be transferred from CB-3 to CB-2 (i.e., capacitor CB-3 discharges and capacitor CB-2 charges). Switches S10B and S8B are also closed (turned on), allowing capacitor CB-1 to discharge and connecting a switching node connected to inductor L1 between switches S8A and S8B to Vin-3Vout, causing inductor L1 to be magnetized to a voltage (Vin-3Vout) -Vout. Specifically, when S8A and S10A are closed, one end of inductor L1 is connected to a potential of Vin-3Vout, while the other end of inductor L1 is connected to Vout. Thus, the voltage difference across the inductor L1 is (Vin-3Vout)-Vout, which defines the magnetizing voltage applied across the inductor L1.

[0067] Thus, the inductor L1 provides a predetermined voltage of (Vin-3Vout)-Vout to the voltage output terminal.

[0068] That is, the switching network creates a current path through the capacitor cells, so the capacitor cells provide the voltage rails. For example, when switches S1A and S3A are closed (turned on), a current path is created through capacitor CA-1, providing a voltage rail with a potential difference of Vin-Vout. When switches S2B and S6B are closed (turned on), a current path is created through capacitor CB-2, providing a voltage rail with a potential difference of Vin-2Vout. When switches S5A and S9A are closed (turned on), a current path is created through capacitor CA-3, providing a voltage rail with a potential difference of Vin-3Vout. Thus, in the first mode, the voltage rails Vin-Vout, Vin-2Vout, and Vin-3Vout are provided by creating current paths through capacitors CA-1, CB-2, and CA-3.

[0069] Fig. Figure 6B shows a second step of the first mode, which occurs once the peak inductor current is reached. On the right side of the inductor cell, switches S2B and S8B are turned off (opened), ending the magnetization step of the first mode. Switch S9 is turned on (closed), and Vout is applied to inductor L1 to lower its current. For example, the current can be lowered linearly.

[0070] Fig. Figure 6C shows the power converter operating in a second mode, where the power converter performs a first step of the second mode. In the first step of the second mode, switches S1B, S3B, S5B, S7B, and S9B (all odd-numbered switches on the right side of the inductor cell) and S2A, S4A, S6A, S8A, and S10A (all even-numbered switches on the left side of the inductor cell) are closed (or turned on), allowing capacitors CA-2, CB-3, and CB-1 to be charged simultaneously.

[0071] More specifically, on the right side of the inductor cell, switches S1B and S3B are closed (turned on), connecting capacitor CB-3 between Vin and Vout and charging the capacitor to Vin-Vout. At the same time, switches S7B, S5B, and S9B are closed (turned on), connecting capacitors CB-2 and CB-1 and allowing charge to be transferred from CB-2 to CB-1 (i.e., capacitor CB-2 discharges and capacitor CB-1 charges). In this example, capacitor CB-2 was previously charged to Vin-2Vout in a previous mode, causing capacitor CB-1, connected to Vout by switch S10B, to be charged to a potential of Vin-3Vout.

[0072] On the right side of the inductor cell, switches S2A, S4A, and S6A are closed (turned on), connecting capacitors CA-1 and CA-2 and allowing charge to be transferred from CA-1 to CA-2 (i.e., capacitor CA-1 discharges and capacitor CA-2 charges). CA-2 charges to Vin-2Vout. Switches S10A and S8A are also closed (turned on), allowing capacitor CA-1 to discharge and connecting a switching node connected to one end of inductor L1 between switches S8A and S8B to Vin-3Vout, causing inductor L1 to be magnetized to a voltage (Vin-3Vout) -Vout. Similar to the above, when S8B and S10B are closed, one end of inductor L1 is connected to a potential of Vin-3Vout, while the other end of inductor L1 is connected to Vout.Thus, the voltage difference across the inductor L1 is (Vin-3Vout)-Vout, which defines the magnetizing voltage applied across the inductor L1.

[0073] Thus, inductor L1 again provides a predetermined voltage of (Vin-3Vout)-Vout to the voltage output terminal in the second mode.

[0074] That is, the switching network creates a current path through the capacitor cells, so the capacitor cells provide the voltage rails. For example, when switches S1B and S3B are closed (turned on), a current path is created through capacitor CB-3, providing a voltage rail with a potential difference of Vin-Vout. When switches S2A and S6A are closed (turned on), a current path is created through capacitor CA-2, providing a voltage rail with a potential difference of Vin-2Vout. When switches S5B and S9B are closed (turned on), a current path is created through capacitor CB-1, providing a voltage rail with a potential difference of Vin-3Vout. Thus, in the first mode, the voltage rails Vin-Vout, Vin-2Vout, and Vin-3Vout are provided by creating current paths through capacitors CB-3, CA-2, and CB-1.

[0075] Fig. Figure 6D shows a second step of the second mode, which occurs once the peak inductor current is reached. On the left side of the inductor cell, switch S6A is turned off (opened), ending the magnetization step of the first mode. Switch S9 is turned on (closed), and -Vout is applied to inductor L1 to lower its current. For example, the current can be lowered linearly.

[0076] Thus, in this example, it can be seen that four voltage rails are provided: Vin, Vin-Vout, Vin-2Vout, and Vin-3Vout. The four voltage rails are provided by multiple capacitive current paths provided by a combination of the capacitor cells (or modules) and the switching network, and can be selected (by controlling the switching network) to provide a predetermined output voltage. The four voltage rails are continuously provided by implementing a symmetrical circuit structure and mirroring the function of the left and right sides of the circuit across the two modes. That is, the left side of the circuit in the first mode performs the function of the right side of the circuit in the second mode, and vice versa. Thus, the capacitors continuously switch between charging and discharging.

[0077] Fig. Figure 7 shows an exemplary power converter that provides an example of how the capacitor cells and inductor cells can be replicated. An exemplary capacitor cell is indicated by dot-dashed box 703, and an exemplary inductor cell is indicated by dot-dashed box 707.

[0078] The exemplary capacitor cell 703 includes capacitor CB-n and switches 705-7, 705-12, 705-17. Switch 705-7 connects capacitor CB-n to another capacitor cell (such as the capacitor cell that includes capacitor CB-2). Switch 705-12 connects capacitor CB-n to Vout. Switch 705-17 connects capacitor CB-n to ground. A current path may be created through capacitor CB-n, charging capacitor CB-n and providing a voltage rail with voltage Vin-nVout.

[0079] Thus, it can be seen that the power converter discussed herein can be scaled by adding additional capacitor cells to provide additional voltage rails.

[0080] The example inductor cell 707 includes four switches: 705-24, 705-21, 705-22, 705-23, and inductor Lm. Switch 705-24 connects inductor Lm to Vin, which charges Lm to Vin-Vout when the voltage across the capacitors drops below Vout. Switches 705-21 and 705-22 connect inductor Lm to the capacitor cells on the left and right sides of the inductor cells, respectively. Switch 705-23 connects inductor Lm to ground, allowing it to demagnetize after reaching peak current.

[0081] Fig. Figure 7 also shows an example where each capacitor cell also includes an optional inductor Lr1 to Lr4. These inductors Lr1 to Lr4 enable smooth charging of the capacitors and prevent redistribution current spikes during energy transfer between capacitors. In other examples, there may be more or fewer inductors depending on the number of capacitor cells; for example, if the power converter includes eight capacitor cells, six of the capacitor cells may include an inductor. The two capacitor cells connected to the at least one inductor cell do not require a parasitic inductor.

[0082] Fig. Figure 8 shows a power converter 800 according to a third embodiment. The power converter 800 can operate in substantially the same manner as the power converters described with reference to Figures Fig. 3 to Fig. 7 are described.

[0083] The power converter 800 is a symmetrical circuit comprising six capacitor cells distributed so that there are three capacitors on the right side and three capacitors on the left side of the inductor cell. Specifically, capacitors 801-1, 801-2, and 801-3 are positioned on the left side of the inductor cell, and capacitors 801-4, 801-5, and 801-6 are positioned on the right side of the inductor cell.

[0084] In this example, the odd-numbered capacitors (801-1, 801-3, 801-5) belong to a first set of capacitors, and the even-numbered capacitors (801-2, 801-4, 801-6) belong to a second set of capacitors. For example, the first set of capacitors may be similar to the first set of capacitors described with reference to the Fig. 3 and Fig. 5 is described.

[0085] The capacitors of the first set of capacitors, positioned on the left side of the inductor cell (capacitors 801-1 and 801-3), are connected to switches 805-15 and 805-16. Switch 805-15 connects capacitors 801-1 and 801-3 to Vout. Switch 805-16 connects capacitors 801-1 and 801-3 to ground.

[0086] The capacitors of the second set of capacitors, located on the left side of the inductor cell (capacitor 801-2), are connected to switches 805-11 and 805-12. Switch 805-11 connects capacitor 801-2 to Vout. Switch 805-12 connects capacitor 801-2 to ground.

[0087] Similarly, capacitors of the first set of capacitors, which now discuss the right side of the inductor cell, are connected to switches.

[0088] It is understood that in other examples there may be additional capacitors on each side of the inductor cell; these capacitors would follow the same connection scheme as described for the Fig. The specific circuit shown in Figure 8 is described.

[0089] Although the provisions referred to Fig. 5 to Fig. While the power converters described in Figure 8 use a symmetrical (double-sided) arrangement of capacitor cells or the like, it should be understood that the circuits are not necessary to be symmetrical. In other examples, a single-sided arrangement of capacitor cells or the like may be used. For example, the capacitors may be grouped into a first group and a second group and connected such that even in a single-sided arrangement, the power converter is functionally the same.

[0090] Fig. 9A and Fig. 9B show two sets of diagrams illustrating stationary waveforms of a power converter, such as those described with reference to the Fig. 1 to Fig. 8 described power converter.

[0091] Fig. Figure 9A shows a set of diagrams representing the steady-state waveforms of a power converter, where each capacitor cell (or voltage rail supply cell) includes an inductor. In comparison, Fig. 9B shows a set of diagrams illustrating the steady-state waveforms of a power converter where each capacitor cell (or voltage rail supply cell) does not include an inductor.

[0092] It can be seen that the waveforms of Fig. 9A show smooth transitions throughout the switching sequence. Thus, it can be seen that the inclusion of inductors in the capacitor cells helps prevent large changes in the voltage across the capacitors. With reference to Fig. 6A, for example, when switches S1A and S3A are closed (turned on), connecting capacitor CA-1 between Vin and Vout, the inclusion of an inductor in the capacitor cell helps prevent large redistribution current spikes that can occur when the capacitor voltage is far from the final target voltage of Vin-Vout.

[0093] Various improvements and modifications of the foregoing may be made without departing from the scope of the disclosure.

Claims

[1] A power converter configured to receive an input voltage via a voltage input terminal and to output a predetermined output voltage via a voltage output terminal, comprising: two or more voltage rail supply cells connected between the voltage input terminal and ground; a switching network comprising a plurality of switches and configured to generate a current path through the two or more voltage rail supply cells such that the two or more voltage rail supply cells provide two or more voltage rails, each corresponding to a predetermined input-output voltage difference; at least one power storage cell connected between the two or more voltage rail supply cells and the voltage output terminal, wherein the at least one power storage cell is configured to output the predetermined output voltage to the voltage output terminal; a control circuit configured to control the switching network to select at least one of the two or more voltage rails in order to set the predetermined output voltage. [2] Power converter according to claim 1, wherein the two or more voltage rail supply cells are two or more capacitor cells; wherein the at least one power storage cell is at least one inductor cell; and where each of the two or more voltage rails is provided by two of the two or more capacitor cells. [3] Power converter according to claim 1, wherein the switching network generates the current path through the two or more voltage rail supply cells by switching each of the voltage rail supply cells so that it is connected to ground or the voltage output terminal; wherein each voltage rail supply cell is switchably connected to ground and the voltage output terminal. [4] Power converter according to claim 1, wherein the selected at least one voltage rail is connected in series to provide the predetermined output voltage via the power storage cell; and wherein an additional voltage rail is added by connecting two additional voltage rail supply cells. [5] Power converter according to claim 2, wherein each capacitor cell comprises: a capacitor; and at least one capacitor connection switch of the switching network, wherein the at least one capacitor connection switch connects the capacitor to one of the two or more voltage rails. [6] Power converter according to claim 2, wherein the switching network comprises: three voltage input switches, wherein two of the voltage input switches connect an input voltage terminal to a capacitor of one of the two or more capacitor cells, and a third voltage input switch connects the input voltage terminal to the inductor cell; and a plurality of output voltage switches, wherein the output voltage switches connect the first set of capacitors and the second set of capacitors to the output voltage; and a multitude of ground switches, wherein the ground switches connect the first set of capacitors and the second set of capacitors to ground. [7] Power converter according to claim 2, wherein the control circuit controls the switching network such that it operates in a first mode in a first phase and in a second mode in a second phase; and wherein the control circuit controls the switching network such that it switches between the first mode and the second mode. [8] Power converter according to claim 7, wherein a first set of capacitors of the two or more capacitor cells is charged in the first mode and discharged in the second mode; wherein a second set of capacitors of the two or more capacitor cells is charged in the second mode and discharged in the first mode. [9] Power converter according to claim 8, wherein the first set of capacitors is charged simultaneously in a first step of the first mode; wherein the second set of capacitors is charged simultaneously in a first step of the second mode; and where the first set of capacitors provides the two or more voltage rails in the first mode and the second set of capacitors provides the two or more voltage rails in the second mode. [10] Method for setting an output voltage using a power converter configured to receive an input voltage via a voltage input terminal and to output a predetermined output voltage via a voltage output terminal, wherein the power converter comprises two or more voltage rails, the method comprising: Control, by means of a control circuit, of a switching network comprising a plurality of switches to generate a current path through two or more voltage rail supply cells, such that the two or more voltage rail supply cells provide two or more voltage rails, each voltage rail corresponding to a predetermined input-output voltage difference, and each voltage rail supply cell being connected between the voltage input terminal and ground; Select, by the control circuit, at least one of the two or more voltage rails to set a predetermined output voltage; Output, through a power storage cell connected between the two or more voltage rail supply cells and a voltage output terminal, the predetermined output voltage to the voltage output terminal.

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