Regulated Switched Capacitor Converter

Abstract

Embodiments of the present disclosure generally relate to regulated switched capacitor converters. Circuits and methods for voltage conversion within a variant switched capacitor converter (SCC) are provided. The circuit topology of the variant SCC includes an adjustable converter inserted between a switch ladder and a rectifier of the variant SCC. The adjustable converter can be an inductor-based switching converter, such as a buck converter, a boost converter, or a buck / boost converter. The adjustable converter sets the output voltage of the variant SCC and sets the base current flowing through the adjustable converter. The total output current is an amplified version of the base current. Because the base current is much lower than the total output current, the adjustable converter can use an inductor that is much smaller than the inductor required for a voltage converter, through which the entirety of the output current flows through the inductor.

Description

Technical Field

[0001] The present application relates to circuit topologies for hybrid switched capacitor converters for providing a regulated output. Background Art

[0002] Switching direct current (DC) to direct current voltage converters are used in various applications to convert power at an input voltage to power at a desired output voltage. Such voltage converters are used to power loads such as battery chargers, microprocessors, servers, computers, televisions, and many other electronic devices. Voltage converters can step up or step down input voltages, but for brevity and clarity of description, the following background description focuses on buck converters.

[0003] Buck converters represent common types of non-isolated buck converters, in which an electronic switch converts an input DC voltage into an alternating current (AC) voltage applied to an inductor. The switch and inductor are used together with some types of rectifiers to gradually reduce the input voltage and gradually increase the input current, so that a lower voltage and a higher current are provided at the output of the converter. The output voltage (or current) can be adjusted by adjusting the frequency and / or duty cycle at which the electronic switch is switched, so as to maintain a relatively constant voltage (or current) at the output. However, such converters suffer relatively high power losses in both the switch and the inductor. In particular, the entirety of the output current must pass through the inductor. Although the resistive losses of the inductor are preferably minimized, they cannot be eliminated and may result in significant power losses for high output currents. In addition, the voltage drop across the inductor is proportional to its inductance, and a large inductor must be used to support a buck converter with a large step-down ratio. Therefore, large, bulky and expensive inductors are required to support a high input-to-output voltage ratio, as well as a high output current flowing through these inductors. For these reasons, buck converters are generally avoided for applications requiring large step-down ratios.

[0004] Switched capacitor converters (SCCs), including those based on Dickson or similar charge pumps, use a series of electronic switches and capacitors to step down an input voltage. SCCs are generally more efficient than inductor-based buck converters for relatively high voltage step-down ratios and do not require large magnetic components (e.g., inductors). However, conventional SCCs are only capable of providing discrete / fixed step-down ratios, such as 2:1, 3:2, 6:1, and are not suitable for regulation. Therefore, conventional SCCs, at least by themselves, are not suitable for powering loads that require a relatively constant voltage.

[0005] Converter circuit topologies and associated techniques are desired that are capable of regulating output voltage while achieving high efficiency, having low converter impedance, and avoiding large magnetic or other components. Summary of the invention

[0006] According to an embodiment of a regulated switched capacitor converter (SCC), the regulated capacitor converter includes a first I / O terminal and a second I / O terminal, a rectifier coupled to the second I / O terminal, a first capacitor coupled between a first voltage node and a ground reference, a switch ladder, and a variable voltage converter. The switch ladder is coupled between the first I / O terminal and the first voltage node, and includes a first switch, a second switch, and a second capacitor. The first switch is coupled to the first capacitor at the first voltage node. The second switch is coupled to the first switch at the second voltage node, and is also coupled between the first I / O terminal and the first switch. The second capacitor is coupled between the second voltage node and a node of the rectifier. The variable voltage converter is coupled between the first voltage node and the second I / O terminal, and is configured to provide a variable voltage drop between the first voltage node and the second I / O terminal. In a preferred embodiment, the variable voltage switching converter includes a switching power stage and an inductor, such as is typically included in a buck converter or a boost converter.

[0007] According to an embodiment of a regulated SCC system, the system comprises a regulated SCC as described above and a controller. The controller is configured to generate a first control signal for controlling a first switch, a second control signal for controlling a second switch, and a power level control signal for controlling a power level of a variable voltage switching converter. The power level control signal can be used to control a variable voltage drop across the variable voltage switching converter and can be used to regulate the output voltage of the regulated SCC system.

[0008] According to an embodiment, a method for controlling a regulated SCC is provided, the regulated SCC comprising a first input / output (I / O) terminal and a second input / output (I / O) terminal, a rectifier coupled to the second I / O terminal, a first capacitor coupled between a first voltage node and a reference voltage, a switch ladder, and a variable voltage switching converter. The switch ladder comprises a first switch and a second switch coupled between the first I / O terminal and the first voltage node, and a second capacitor coupling an interconnection node of the first switch and the second switch to a first node of the rectifier. The variable voltage switching converter comprises a power stage and an inductor, and is coupled between the first voltage node and the second I / O terminal. The method comprises generating a first control signal for controlling the conductivity of the first switch, generating a second control signal for controlling the conductivity of the second switch, and generating a power stage control signal for controlling the conductivity of the power stage. The generated power stage control signal can be used to adjust the output voltage of the regulated SCC.

[0009] Those skilled in the art will recognize additional features and advantages upon reading the following detailed description, and upon viewing the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] The elements of the drawings are not necessarily drawn to scale relative to each other. The same reference numerals represent corresponding similar parts. The features of the various illustrated embodiments may be combined unless they exclude each other. The embodiments are depicted in the drawings and are detailed in the following description.

[0011] Figure 1 A schematic diagram of a regulated switched capacitor converter (SCC) is shown.

[0012] Figure 2A and Figure 2B Shown with Figure 1 The voltage and current waveforms corresponding to the regulated SCC.

[0013] Figure 3 Shows that with Figure 1 Schematic diagram of alternative regulated SCCs for different conversion ratios of the regulated SCCs.

[0014] Figure 4A , Figure 4B and Figure 4C A schematic diagram of an adjustable converter that may be used within a regulated SCC is shown.

[0015] Figure 5 A schematic diagram of an alternative regulated SCC having yet another different conversion ratio and using a buck / boost converter is shown.

[0016] Figure 6 shows a schematic diagram of a regulated SCC, where the power is Figure 1 The power flows in the opposite direction to that shown.

[0017] Figure 7 A method for controlling a regulated switched capacitor converter is described. DETAILED DESCRIPTION

[0018] Embodiments described herein provide circuits and methods for voltage conversion using a charge pump variant switched capacitor converter (SCC) topology. The SCCs described herein are not limited to discrete step-up or step-down ratios like conventional SCCs, but are dynamically adjustable so that a regulated output can be provided. These variant SCCs provide efficiency, high current, and power density similar to conventional SCCs, but also provide the regulation required by many loads (e.g., microprocessors or other digital circuits).

[0019] Charge pump-based SCCs are becoming increasingly popular due to their ability to support large voltage step-down (or step-up) ratios and high current throughput, while having high efficiency (low power losses) and requiring minimal area / volume for the circuit. Of particular note, conventional SCCs do not require bulky magnetic components such as inductor-based buck and boost converters. In a common application for SCCs, data centers are increasingly distributing power buses with 48V direct current (DC) voltages that must be down-converted for use by individual servers, processors, and the like. SCCs can provide such down-conversion and output, for example, a 12V DC power supply, an 8V DC power supply, or a 6V DC power supply. Many loads (e.g., processors) must be powered by even lower voltages, and also require that the supplied power be regulated to maintain a relatively constant voltage even when the load current and input voltage vary.

[0020] One technique for providing regulated power in systems using conventional SCCs is to couple an inductor-based buck converter between the SCC and the load. The buck converter, typically located at the point of load (POL), can provide the final voltage step-down conversion and voltage regulation. While the inductor in such a system is smaller than in a system that relies entirely on a buck converter for down-conversion, such an inductor is still relatively large because it must be able to carry the entire current provided to the load. In addition and related thereto, the resistive power losses of the inductor can be significant.

[0021] The recently introduced hybrid Dickson converter provides a type of SCC with a step-down ratio that is not limited to a discrete / integral ratio. The hybrid Dickson converter modifies a conventional SCC by coupling an inductor between the rectifier of the SCC and the load. In a further variation, a hybrid dual-inductor converter uses an inductor to couple each of the two sets of SCC branches (capacitors) to the load. Similar to the SCC / buck converter systems described above, these hybrid converters suffer from the disadvantage that all output current must be carried by one or more inductors.

[0022] Embodiments described herein provide a variant SCC circuit topology in which an adjustable voltage converter is coupled between an SCC switch ladder and a rectifier. The adjustable voltage converter may be, for example, an inductor-based buck converter. The adjustable voltage converter may set the output voltage of the variant SCC to a value converted from a fixed ratio of an input voltage from the variant SCC. The voltage across the adjustable voltage converter may be dynamically adjusted to provide a regulated output voltage, for example, by controlling the adjustable voltage converter using a closed-loop controller. The switching frequency or duty cycle of the adjustable voltage converter may be independent of the switching frequency of the switches within the SCC switch ladder and the rectifier. Thus, an optimized frequency may be used for switches in the switch ladder, for example, switching at near zero voltage or zero current, while the closed-loop controller independently changes another switching frequency or duty cycle to achieve a desired voltage across the adjustable voltage converter.

[0023] The adjustable voltage converter sets the output current level of the variant SCC, but does not carry all of the output current. For a buck variant SCC with N switches in its switch ladder, only about 1 / N th In addition to providing only a portion of the voltage drop of the entire variant SCC, the inductor within the adjustable voltage converter only needs to carry a relatively small portion (approximately 1 / N) of the current output from the variant SCC. th ). Because the size of an inductor depends on the voltage across it and its power (current) rating, the low required inductor voltage and current allow the inductor to be relatively small compared to other inductor-based voltage converters. In addition, the low current through the inductor results in relatively small resistive power losses in the inductor compared to voltage converter topologies in which the entire output current must flow through the inductor.

[0024] Embodiments are described below by specific examples of variant SCCs. These examples have a common feature in that they include an adjustable voltage converter inserted between the SCC switch ladder and the SCC rectifier, wherein the adjustable voltage converter determines the output voltage of the variant SCC. Alternatively, the adjustable voltage converter can be considered to provide an adjustable base current, and the SCC switch ladder and the SCC rectifier effectively apply current amplification (increase) to the base current. The description focuses primarily on a variant SCC that steps down the input voltage to provide a reduced output voltage, but the circuit topology of the variant SCC also supports a boost mode in which the input terminals and output terminals are functionally swapped. It should be understood that the following examples are not meant to be limiting. Circuits and techniques well known in the art are not described in detail in order to avoid obscuring the unique aspects of the present invention. Features and aspects from the example embodiments may be combined or rearranged unless the context does not allow this.

[0025] The following description continues with an embodiment of a variant SCC having three switching stages in its switching ladder and a buck converter for its adjustable voltage converter, so that three or more voltage step-downs are achieved. The topology is explained in detail using voltage and current waveforms. This is followed by a description of several alternative versions of the variant SCC in which the number of switching stages is changed, different adjustable voltage converters are used, and the power flow is reversed in order to provide a step-up of the voltage. Finally, a method for operating the variant SCC is described.

[0026] Variant switched capacitor converter with three switching stages

[0027] Figure 1 An embodiment of a variant SCC 100 according to the present invention is shown. The variant SCC 100 includes a switch ladder 110, a rectifier 120, an adjustable converter 130 and a controller 190. The adjustable converter 130 is inserted between the switch ladder 110 and the rectifier 120 and is provided with current from the switch ladder 110 and the first capacitor C1. The variant SCC 100 also includes a first terminal 101 and a second terminal 102 for connecting to an input power source and an output load. For the illustrated operating mode, the first terminal 101 is connected to a first terminal 102 having an input voltage V IN The second terminal 102 provides an output voltage V for the load of the variant SCC. OUT (For ease of illustration, the input power supply and load are not shown.) The output capacitor C OUT is coupled to the second (output) terminal 102 and is responsive to the output voltage V OUT Perform filtering.

[0028] The illustrated switch ladder 110 includes three switches Q1, Q2, Q3 and two connection capacitors C2, C3 and is configured and controlled in substantially the same manner as in a conventional SCC, except for its rectifier connections. Switch control signals PWMA, PWMB alternately turn on switches of group 'A' including switch Q2 and group 'B' including switch Q1 and switch Q3. In a first time interval, the group B switches are turned on and the group A switches are turned off, so that energy is transferred from V to V via switch Q3. IN The energy is transferred to capacitor C2 and from capacitor C2 to capacitor C1 and adjustable converter 130 via switch Q1. In a second time interval, group A switch Q2 is turned on and group B switch is turned off, so that energy is transferred from capacitor C3 to capacitor C2 via switch Q2. In addition to the positive current flowing through switch Q3, switch Q2, switch Q1 and capacitor C3, capacitor C2, connecting capacitor C3, connecting capacitor C2 provides current I to rectifier 120. RA 、Current IRB More specifically, if Figure 1 As shown, each of the capacitors C3 and C2 provides an average current to the rectifier 120 after rectification. IN > Among them IN > is the input current I IN The average of RA >≈ RB >≈ IN Because the operation of the switch ladder 110 is similar to the corresponding operation within a conventional SCC, no further details regarding the operation of the switch ladder 110 are provided.

[0029] In a notable difference relative to conventional SCC, the output of the switching ladder 110 (in Figure 1 The voltage V1 in FIG. 1 represents that the rectifier output and the second (output) terminal 102 are not directly coupled to the rectifier output and the second (output) terminal 102, and the average current is not directly supplied to the second (output) terminal 102. IN >. Instead, the current I1 from the first switch Q1 charges the first capacitor C1, which serves as energy storage for the adjustable converter 130. The adjustable converter 130 then draws the current I0 from the first capacitor C1 (and / or the first switch Q1) in order to achieve the desired voltage drop V across it. ADJ . Provide a voltage sufficiently higher than V OUT The voltage V1 at both ends of the adjustable converter 130 is positive voltage V ADJ decreases, so that the adjustable converter 130 can control the voltage V OUT , for example, in order to set the output voltage V OUT to the desired target voltage.

[0030] The adjustable converter 130 shown is a switching buck converter and includes a high-side switch QH, a low-side switch QL and an inductor L1. The conductivity of the high-side switch QH and the low-side switch QL is controlled by control signals PWMH, PWML, which are provided by the controller 190 and the inverter 182. At most, one of the high-side switch QH and the low-side switch QL is set to be turned on at a given time. For typical continuous conduction mode (CCM) operation, when the switch transitions state, the conductivity of the high-side switch QH and the low-side switch QL alternates with a short dead time inserted to ensure that the two switches are not turned on at the same time, that is, to avoid shoot-through. The control signals PWMH, PWML can be driven at a fixed frequency, but driven with a variable duty cycle, which determines the voltage drop V across the adjustable converter. ADJ , or having a variable frequency and a fixed duty cycle, or utilizing some combination thereof.

[0031] ​​​​​​In an alternative embodiment, the inverter 182 is not present, and the controller 190 generates separate signals for PWMH and PWMHL, rather than a single control signal PWMHL as illustrated. Such an alternative allows support for a discontinuous conduction mode (DCM), in which both switches QH, QL can be turned off during periods of low current drawn by the load in order to avoid negative current I L1 Through inductor L1. Figure 3 , Figure 5 and Figure 6 A configuration in which the controller generates separate control signals PWMH, PWML is shown in . The control signals PWMH, PWML of the adjustable converter 130 are separate from the control signals PWMA, PWMB for the switching ladder 110 and the rectifier 120 and can be generated independently of the control signals PWMA, PWMB.

[0032] exist Figure 1 The buck converter shown in FIG. 1 is only one example of an adjustable converter. Additional types of adjustable converters are shown in FIG. Figure 4A , Figure 4B and Figure 4C FIG. 1 is a block diagram of a schematic ...

[0033] Rectifier 120 couples the capacitor of switch ladder 110 (sometimes referred to as the “second branch”) to second (output) terminal 102 and is used to provide a rectified output voltage V OUT . The rectifier 120 includes a first half-bridge including switches Q7 and Q8 coupled to the second capacitor C2, and a second half-bridge coupled to the third capacitor C3 including switches Q9 and Q10. The switches Q7 ... Q10 of the rectifier 120 are controlled by switch control signals PWMA, PWMB, which also control the conductivity of the switches Q1, Q2, Q3 in the switch ladder 110. During the previously mentioned first time interval, the switch Q9 is turned on, while the capacitor C3 is discharged via the third switch Q3, and the current flows to the output terminal 102 via the switch Q9. During the previously mentioned second time interval, the switch Q10 is turned on and the capacitor C3 is discharged to the second capacitor C2 via the second switch Q2. Therefore, the second half-bridge supplies current to the output terminal during the first time interval. The first half-bridge operates in a complementary manner, thereby supplying current to the output terminal 102 via the switch Q8 during the second time interval. Thus, the rectifier 120 provides full-wave rectification because current is provided to the output terminal 102 during the first time interval and the second time interval, which represents substantially all of each switching cycle. OUT Make the output voltage V OUTSmoothing is performed to reduce ripple caused by switching of the rectifier 120 and to reduce voltage disturbances caused by load transients. Because the operation of the rectifier 120 is similar to the operation of similar rectifiers within other SCCs, no further description is provided.

[0034] In a conventional 3:1 SCC, there is no adjustable converter, and the steady-state average voltage V across the third capacitor C3 is C3 Will be V C3 =2*V OUT , and the steady-state average voltage V across the second capacitor C2 C2 Will be V C2 =1*V OUT In contrast, the corresponding steady-state voltage for variant SCC 100 is:

[0035] V C3 =V IN -V OUT ,

[0036] V C2 =V IN -2*V OUT ,

[0037] Where V IN Does not need to be equal to 3*V OUT , that is, for non-zero V ADJ V IN ≠3*V OUT During the first time interval, with the rectifier switch Q7 turned on, the second capacitor C2 is coupled to ground, and the first capacitor C1 is charged via the first switch Q1 to match the steady-state voltage V across the second capacitor C2. C2 =V IN -2*V OUT . Voltage V1 = Vin-2*V OUT It can then be used to supply the adjustable converter 130 .

[0038] Figure 1The switches within the illustrated variant SCC 100 are power metal oxide semiconductor field effect transistors (MOSFETs), but other switch types may also be used. For example, in some applications, junction field effect transistors (JFETs), bipolar junction transistors (BJTs), insulated gate bipolar transistors (IGBTs), high electron mobility transistors (HEMTs), or other types of power transistors may be preferred. The switches of the adjustable converter 130 may be of the same or different type as the switches of the switch ladder 110 or the rectifier 120. Although they are generally of the same switch type, the switches Q1, Q2, Q3 of the switch ladder may be sized differently to accommodate different voltage and / or current requirements at different stages (particularly during startup). The switches may be integrated on the same semiconductor die, may each be set on a separate die, or may be otherwise distributed across multiple semiconductor dies. Each of the MOSFET switches within the SCC 100 has a drain terminal and a source terminal, and a gate terminal that controls conductivity between the drain terminal and the source terminal. A gate driver is typically included to convert digital control signals (such as PWMA, PWMB, PWMH, PWML) into voltage levels suitable for the control terminals (e.g., gates) of each of the drive switches. For ease of illustration, switch drivers are not shown for the switches of variant SCC 100.

[0039] The controller 190 includes an open loop controller 194 and a closed loop controller 192. The open loop controller generates a switching control signal PWMAB, which is also shown as PWMA, and is inverted by the inverter 184 to generate a switching control signal PWMB. The switching control signals PWMA, PWMB control the conductance of switches within the switching ladder 110 and the rectifier 120. These switching control signals are typically pulse width modulated (PWM) waveforms with a fixed frequency and a duty cycle of approximately 50%.

[0040] The closed-loop controller 192 (which may include, for example, a proportional-integral-derivative (PID) controller) generates a high-side switch control signal PWMH and a low-side switch control signal PWML to provide a regulated output voltage V at the output of the adjustable controller 130. OUT . Output voltage V OUT The sensed version is provided to the controller 190 so that the closed-loop controller 192 can adjust the switch control signal PWMHL, for example, by adjusting the PWM duty cycle, so that even when the input voltage V IN or load current I OUT When the output voltage V OUT Maintain near the desired target voltage. Input voltage V INMay optionally be used by controller 190, for example, to provide feed-forward control for the power flow direction described.

[0041] In some variants, the closed-loop controller 192 may not be included. For example, a variant SCC 100 may not need to provide a regulated output voltage V OUT , but it may be necessary to provide a voltage reduction that is not an integer ratio (eg, a 3.5:1 ratio). For this case, the switch control signal PWMHL (or PWMH, PWML) may be generated by an open-loop controller.

[0042] As shown, the open-loop controller 194 and the closed-loop controller 192 need not be within the same controller 190. For example, the closed-loop controller 192 may be part of the adjustable converter 130 and may generate its switching control signals PWMH, PWML independently of the controller 190.

[0043] The controller 190 and its components may be implemented using a combination of analog hardware components (such as transistors, amplifiers, diodes, and resistors) and a processor circuit that primarily includes digital components. The processor circuit may include one or more of a digital signal processor (DSP), a general-purpose processor, and an application-specific integrated circuit (ASIC). The controller 190 may also include a memory, such as a non-volatile memory, such as a flash memory, that includes instructions or data used by the processor circuit, and one or more timers, such as for generating a first conduction interval and a second conduction interval based on a switching frequency and a dead time interval.

[0044] Using a buck converter as the adjustable converter 130, the average inductor current I L1 The relationship with the buck converter input current I0 is L1 >= <i0> / d, where d is the duty cycle corresponding to the interval of the high-side switch QH. Therefore, the average output current I of the variant SCC100 is OUT Given by:

[0045]

[0046] Among them, <i0>= IN >, providing the following current gain

[0047]

[0048] where N is the number of switches in the switching ladder. If the duty cycle d is close to 100%, for example 90%, the gain simplifies to the approximation Igain ≈ N, and the current I L1 The output current I OUT 1 / N th Note that the reduced current of the adjustable converter 130 depends on its topology. While a buck converter gives a current reduction of less than 1 / N of the current, a boost converter will provide a current reduction of more than 1 / N of the current. This is Figure 4A , Figure 4B and Figure 4C is further addressed in the description of .

[0049] Although the power flow from the first terminal 101 to the second terminal 102 is described above, the power flow may be reversed, in which case the variant SCC will perform boosting, and in this case the voltage at the first terminal 101 may be the output voltage to be regulated. Figure 6 Such a configuration is further described.

[0050] Figure 2A and Figure 2B shows the corresponding Figure 1 The voltage and current waveforms of the operation of the variant SCC 100 are provided and described only to aid understanding. Figure 1 The waveforms correspond to the steady-state operating condition of the variant SCC 100 after any startup transients (e.g., capacitor charging) have completed. These waveforms include switch control signals PWMAB, PWMHL; switch step current I IN , switch step current I2, switch step current I1; capacitor current Ia, capacitor current Ib; voltage V3, voltage V2, voltage V1, voltage V at each node of variant SCC100 OUT ; and the input current I0 and output current I of the adjustable converter 130 L1 .

[0051] The control signal PWMAB controls the switches Q1, Q2, Q3 of the switching ladder 110 and the switches Q7 ... Q10 of the rectifier 120, and corresponds to Figure 1 ​200 and 201. The control signal PWMAB is shown in FIG. 202. When the control signal PWMAB is high, the switches Q2, Q8, Q10 of group A are turned on. When the control signal PWMAB is low, the switches Q1, Q3, Q7, Q9 of group B are turned on. Dead time is automatically inserted between the intervals of group A and the intervals of group B to avoid cross conduction. The waveform 202 shown for the control signal PWMAB has a frequency of 500 kHz and a duty cycle of approximately 50%.

[0052] The control signal PWMHL controls the switches QH and QL of the adjustable converter 130, which is Figure 1 200 is a step-down converter in FIG. 200 . When the control signal PWMHLH is high, the high-side switch QH is turned on, and when the control signal PWMHLH is low, the low-side switch QL is turned on. (Dead time is automatically inserted between the intervals of the high-side switch QH and the intervals of the low-side switch QL to avoid cross conduction.) The control signal PWMHL shown has a frequency of 1.2 MHz and a duty cycle of approximately 90%, i.e., the high-side switch QH is turned on for 90% of each switching cycle, and the low-side switch QL is turned on for 10% of each switching cycle. Note that the frequency of waveform 204 of the control signal PWMHL (1.2 MHz) is independent of and different from the frequency of the control signal PWMAB (500 kHz). The control signal PWMHL shown may be controlled by a closed-loop controller (e.g., Figure 1 The PID 192) generates an output voltage V under the condition that the attached load sinks a relatively constant current. OUT regulated to approximately 20 V. Alternatively, Figure 2A and Figure 2B The waveform 204 may correspond to a situation where the open-loop controller is generating the control signal PWMHL, in which case the output voltage V OUT will be fixed at 90% of the buck converter input voltage V1 , ignoring ripple and losses within the adjustable converter 130 .

[0053] At time t1, the aforementioned first time interval begins and the group B switches are turned on. When the third switch Q3 is turned on, the voltage V3 rises to the input voltage V except for a small voltage drop across the third switch Q3. IN In the illustrated example, the input voltage V IN At time t1, the voltage V3 rises to about 65V and quickly rises to about 64V ​​at time t1, after which it slowly rises to nearly 65V at time t2. Also at time t1, the first switch Q1 is turned on and the voltage V2 drops to match the voltage V1 at the input of the adjustable converter 130, where the voltage V1 is smoothed / stabilized by the first capacitor C1. During the interval between time t1 and t2, for the waveform shown, the voltage V2 is about 23V. Also starting at time t1, as energy from the second capacitor C2 charges the first capacitor C1 via the first switch Q1, the voltage V1 rises slightly, for example, from 22V to 23V.

[0054] At time t2, the aforementioned second time interval begins, and group A switch Q2 is turned on. With the node corresponding to voltage V3 and voltage V2 coupled together, voltage V3 drops and voltage V2 rises until they are both approximately 44 V. With the node having voltage V1 disconnected from the node having voltage V2, voltage V1 slowly dissipates between time t2 and time t3 as energy is drawn from first capacitor C1 to provide current I0 to adjustable converter 130.

[0055] During the entire switching cycle between time t1 and time t2 (and elsewhere), the output voltage V OUT The ripple will vary within a narrow range around its target value of 20V, for example between about 19.5V and 20V. In a more typical circuit, a larger output capacitor will be used (depending on the load variation) so that the ripple will be well below 1% of the target voltage, and preferably within 0.1% to 0.5%. (In Figure 2A Used to generate waveform V OUT The capacitor C used in the circuit OUT With a 1μF capacitor, the Figure 2A Some ripples can be discerned in the

[0056] Waveforms 212 and 214 correspond to currents Ib and Ia flowing to the third capacitor C3 and the second capacitor C2, respectively. At time t1 when switch Q3 is turned on, the current Ib flowing to capacitor C3 reaches a peak value of about 6A, and then decays until time t2 when switch Q3 is turned off. At time t2 when switch Q3 is turned off and switch Q2 is turned on, a positive current flows from the third capacitor C3 to the second capacitor C2. This is illustrated as a negative current peak (approximately -6A) for Ib and a corresponding positive current peak (+6A) for Ia at time t2. When switch Q2 is turned off, these current magnitudes decay to more stable magnitudes until time t3. Also at time t3, switch Q1 is turned on, causing current (and energy) to flow from capacitor C2 to capacitor C1. This is illustrated as a negative current peak (approximately -6A) on waveform 212 of current Ia. Furthermore, at time t3 , the switch Q3 is turned on so that the current positive current Ia flows from the first terminal 101 in the same manner as at time t1 .

[0057] The input current I flowing through the third switch Q3 is also shown. IN , the current I2 through the second switch Q2 and the current I1 through the first switch Q1 are waveforms 222, 224, and 226 corresponding to each other. During the interval between time t1 and time t2, the input current I IN , flows to the third capacitor C3 through the third switch Q3, and can be regarded as being substantially the same as the current Ib during this interval. Between time t2 and time t3, the third switch Q3 is turned off, so that there is no input current I IN , as shown in waveform 222. Also during the interval between time t1 and time t2, current I1 flows through the first switch Q1, as shown in waveform 226. During this period, current I1 is substantially the same as current Ia of the second capacitor C2, except for the reverse polarity.

[0058] During the interval between time t2 and time t3, the second switch Q2 is turned on (switch Q3 and switch Q1 are turned off), and positive current I2 flows through the switch Q2. During this interval, current I2 is substantially the same as the negative value of current Ib and current Ia.

[0059] As shown in the waveform 204 of the control signal PWMHL, the high-side switch QH is turned off between time t4 and time t5. (The low-side switch QL is turned on during this period.) Because no current I0 is sunk by the adjustable converter 130 during this interval, the current I1 through the first switch Q1 drops slightly at time t4 relative to its other conditions. (Similarly, the magnitude of the current Ia from the second capacitor C2 also drops slightly at time t4.) This phenomenon can also be observed at other times when the group B switch is turned on and the high-side switch QH is turned off, for example, the current I1 can also be seen to drop faster at time t6.

[0060] Figure 2B The input current I0 and the inductor current I corresponding to the adjustable converter 130 are shown. L1 The waveforms 250 and 260 are shown. These currents I0 and I L1 The inductor current I L1 has a typical triangular pattern for the buck converter current. For example, between time t7 and time t8, the high-side switch QH is turned on and the inductor current I L1 increases linearly, as shown in waveform 260, thereby creating a current across the adjustable converter 130 that is caused by the inductor current I L1 The slope and inductance of L1 determine the voltage V ADJ Between time t8 and time t9, the low-side switch QL is turned on and the inductor current I L1 Decreases linearly.

[0061] The current I0 flowing into the adjustable converter 130 is shown in the waveform 250. This current I0 substantially follows the inductor current I except for the interval in which the high-side switch QH is turned off (e.g., between time t8 and time t9). L1 During such intervals, no current I0 flows into the adjustable converter 130 .

[0062] Figure 2A and Figure 2B The waveform corresponds to a Figure 1 A circuit in which capacitor C1, capacitor C2 and capacitor C3 have a capacitance of 500nF, and inductor L1 is 2.7μH.

[0063] Variant Switched Capacitor Converters with Other Step-Down Ratios

[0064] Can be modified Figure 1 The circuit topology shown in can be used to provide different down-conversion ratios. For example, a 2:1 buck converter can be created by removing the third switch Q3, the third capacitor C3, and the second half-bridge (switch Q9, switch Q10). Figure 1 Unlike the SCC100 of FIG. 100 , such a converter will have only a half-wave rectifier (switch Q7, switch Q8) at its output and will therefore experience more ripple, which may limit the utility of such a converter. In addition, a major advantage of the circuit topology provided herein is that a relatively small current is provided by the inductor of the adjustable converter. A variant SCC with two switches in its switching ladder will provide a nominal step-down ratio of 2:1, and the inductor current will only be reduced by a factor of about 2 relative to a conventional buck converter. Because the inductor current represents approximately 1 / N of the total output current of the variant SCC described herein, th , where N is the number of switches (and the nominal step-down ratio), so the inductor current is preferably reduced by having a larger number of switches and the associated larger step-down ratio. Figure 3 (The current reduction of 1 / N depends on the type of adjustable converter in use. For a buck converter, the current reduction will be less than 1 / N, while for a boost converter it will be more than 1 / N.)

[0065] Figure 3 A variant SCC 300 having a step-down ratio of X:1 is shown, where X ≥ 6, and is typically between 6 and 7. Figure 3 The variant SCC 300 has Figure 1 The circuit structure of is similar to the circuit structure of , and only the substantial differences are described below.

[0066] The switch ladder 310 includes 6 switches and 5 capacitors, thereby generating a down-conversion ratio of 6:1 or greater. Each connected capacitor C2 ... C6 provides an output current I OUT About 1 / X of th , so that the switch ladder 310 and the rectifier 120 provide an output current I OUT About 5 / X th Therefore, the adjustable converter 130 only needs to provide an output current I OUT About 1 / X of th The low current through the adjustable converter 130 and its inductor L1 means that the inductor L1 can be relatively small and the power loss of the inductor L1 will be relatively low. This represents an advantage over Figure 1 Advantages of the variant SCC100.

[0067] Although the topology of the rectifier 120 is similar to Figure 1 , but the odd number (5) of capacitors C2 ... C6 in variant SSCC300 generates a current imbalance between the half bridges of rectifier 120. The first half bridge including switches Q7 and Q8 is fed by three capacitors (C6, C4, C2) to support 3 / X of the output current th The second half bridge including switches Q9 and Q10 is fed by two capacitors (C5, C3) and thus supports 2 / X of the output current. th This imbalance will result in an output voltage V OUT . For some applications, and in particular for switch ladders with a relatively small number of switches, it may be preferred that the switch ladder comprises an odd number of switches and an even number of capacitors in order to reduce the current imbalance through the half-bridges of the rectifier. Furthermore, the imbalance may mean that different switches may be required in the half-bridges because they support different current levels. Alternatively, the rectifier may comprise more than two half-bridges, for example one half-bridge for each capacitor (leg) of the switch ladder, which will evenly distribute the current load between the half-bridges and allow similarly sized switches throughout the rectifier.

[0068] In addition, the operation of the variant SCC 300 is similar to that in Figure 1 The operations shown in FIG. 1 are not described herein and therefore no further explanation is provided.

[0069] Optional adjustable converter

[0070] Figure 1 The adjustable converter 130 is a buck converter including a half-bridge and an inductor, but it should be understood that other converters, buck converters or other converters may be used instead. Figure 1 The adjustable converter 130. Several alternatives of the adjustable converter are described below.

[0071] exist Figure 1 The buck converter topology shown in FIG. 1 can be replaced by other buck converter circuits. For example, the low-side switch QL of the adjustable converter 130 can be replaced by a diode. This provides the advantage of requiring only one switch control signal, but has the disadvantage of being more complex than an active rectifier switch (such as Figure 1 The low-side switch QL) has the disadvantage of higher power losses through the passive diode. The buck converter can be based on different Figure 1 The circuit topology of the adjustable converter 130 is shown in FIG. 1 , but typically includes an inductor and two switches, or a switch and a diode.

[0072] Figure 4A A buck converter 430a is shown which is similar to the buck converter of adjustable converter 130. However, Figure 4A The buck converter 430 includes a p-channel MOSFET PH for the high-side switch QH and an n-channel MOSFET NL for the low-side switch QL. This can allow for a simplified driver circuit and a single switch control signal PWM_ADJ. However, using this type of push-pull circuit eliminates the option of operating in DCM.

[0073] Regardless of the specific components and topology, buck converters offer the advantage of fast response time. For systems that require tight regulation from a variant SCC, buck converters are often preferred because they provide good performance in response to load transients. However, a disadvantage of buck converters is that they may require larger inductors than other switching converter types. Because buck converters are well known, further details about their operation are not provided here.

[0074] Figure 4B A boost converter 430b is shown having a topology similar to that of the buck converter 430a, but in an inverted orientation, i.e., the input current flows through the inductor L1, and the output current flows through the half-bridge consisting of the high-side switch QH and the low-side switch QL. Compared to the buck converter 430a, the boost converter 430b carries a smaller current through its inductor L1, and thus its inductor can be smaller. Compared to the variant SCC using the buck converter, the boost converter 430b relies on the SCC ladder 110 and the rectifier 100 to carry the output current I OUT Boost converters, such as boost converter 430b, have the disadvantage of providing a slower response to load transients than, for example, a buck converter. Because boost converters are well known, further details about their operation are not provided herein.

[0075] Figure 4C A buck / boost converter 430c is shown, which can operate in buck mode or boost mode, as determined by switch control signals PWMHa, PWMLa, PWMHb, PWMLb. Buck / boost converter 430c includes a first half-bridge QHa, QLa configured similarly to the half-bridge of buck converter 430a and a second half-bridge QHb, QLb configured similarly to the half-bridge of boost converter 430b. When operating in buck mode, switch control signals PWMHb, PWMLb are set to keep the high-side switch QHb turned on and the low-side switch QLb turned off, that is, the boost portion is set to pass mode. Switches QHa, QLa are controlled by control signal PWMHa, which provides the necessary output voltage V in the same manner as previously described for the buck converter. OUT When operated in the boost mode, the switch control signals PWMHa, PWMHa are set to keep the high-side switch QHa turned on and the low-side switch QLa turned off, i.e., the buck portion is set to pass mode. The switches QHb, QLb are controlled by the control signals PWMHb, PWMLb to provide the necessary output voltage V in the same manner as described above for the boost converter. OUT .

[0076] For converter 430a, converter 430b, converter 430c, or similar topologies shown, the high-side switch QH can be kept on and the low-side switch QL can be turned off to affect a pass-through mode. Such a mode can be used, for example, if the variant SCC falls out of regulation, or during startup when the voltage V1 is not yet high enough to provide regulation.

[0077] Regulated switched capacitor converter with buck / boost converter

[0078] Figure 5 Another variant SCC 500 is illustrated. This variant SCC differs from the previously described variant SCC in that the switch ladder 510 includes four switches and three capacitors, resulting in a 4:1 nominal voltage down-conversion. The buck / boost converter 530 (which may be similar to Figure 4C The buck / boost converter 430 c) is described as being used as an adjustable converter. The controller 590 is configured to provide signals PWMHa, PWMLa, PWMHb, PWMLb for controlling the switches of the buck / boost converter 530 .

[0079] As illustrated, the input voltage V of the variant SCC 500 is IN is nominally 48V, and the output voltage V OUT Such a configuration is commonly used in server applications, where unregulated 48V DC voltage is distributed and must be down-converted and potentially regulated to 12V, and in automotive applications.

[0080] If the input voltage V IN If the output voltage V is close enough to its nominal value of 48V and is fairly stable, the controller 590 can set the buck / boost converter 530 to pass mode, in which no regulation is performed. OUT If the input voltage Vin drops too far below its 12V target, or similarly, the input voltage Vin drops too much, the controller 590 switches to operate the buck / boost converter 530 in a boost mode of operation to regulate the output voltage V OUT If the controller 590 detects that the output voltage V OUT If the input voltage Vin rises above its 12V target or similarly the input voltage Vin rises too much, the controller 590 switches the buck / boost converter 530 to a buck operating mode in order to regulate the output voltage V OUT Assuming the input voltage V IN If the expected range of is sufficiently constrained, then variant SCC 500 advantageously provides voltage step-down conversion (current step-up conversion) while requiring a relatively small inductor in the buck / boost converter 530 and providing reasonable response time to transients.

[0081] Bidirectional Regulated Switched Capacitor Converter

[0082] The aforementioned variant SCC assumes operation in which power flows from the first terminal 101 to the second terminal 102 in order to down-convert the voltage. The variant SCC circuit topology also supports power flow in the opposite direction in order to provide voltage up-conversion. Such operation is Figure 6 is shown in .

[0083] Figure 6 shows a similar Figure 1 However, the first terminal 101 serves as an output terminal which can be connected to a load, and the second terminal 102 serves as an input terminal for being connected to a power source.

[0084] The controller 690 is configured to input a direction control signal DIR, which determines the operation mode of the variant SCC 600. If the direction DIR indicates voltage down conversion, the voltage V at the second terminal 102 is IO2 is processed into an output voltage, and the switch control signal PWMH and the control signal PWML are controlled to appropriately adjust the voltage V IO2 , as described above. However, if the direction DIR indicates voltage up-conversion and power flow from the second terminal 102 to the first terminal 101, the voltage V at the first terminal 101 IO1 is processed into an output voltage, and the switch control signal PWMH and the control signal PWML are controlled to adjust the voltage V to the desired target voltage. IO1 .

[0085] Note that the device connected to the first terminal 101 of the variant SCC 600 may operate as a power source in some modes and as a load in other modes. For example, the device connected to the first terminal 101 may be a battery that provides power to the variant SCC 600 during a certain period of time and is charged by the variant SCC 600 during another period of time. Similarly, the second terminal 102 may likewise be connected to a device (e.g., a motor / generator) that sometimes operates as a load and sometimes operates as a power source.

[0086] Method for controlling a regulated switched capacitor converter

[0087] Figure 7 A method 700 for controlling a variant SCC, such as any of the variant SCCs described above, is shown. This method may be implemented in a controller of a variant SCC, such as Figure 1 or a similar controller).

[0088] The method 700 begins with the step of generating 710 control signals for switches within group 'A' of the variant SCC. The method continues by generating 720 control signals for switches within group 'B'. Although shown as separate steps, it should be understood that the control signals for group 'B' can be derived from the control signals for group 'A' and vice versa. The method proceeds by sensing 730 the output voltage V of the variant SCC. OUT Continue, and based on the output voltage V OUT A power stage control signal is generated 740. In a typical embodiment, the power stage control signal controls switches within an adjustable converter, such as a buck, boost, or buck / boost converter. In one embodiment, the output voltage V OUT The output voltage V may be adjusted by the generated power level control signal. In another embodiment, the output voltage V may not be adjusted. OUT , so that fixed voltage down conversion is achieved. Such an embodiment may not require sensing 730 output voltage V OUT The steps of method 700 are typically repeated while the variant SCC is in operation.

[0089] Although the present disclosure is not limited in this regard, the following numbered examples demonstrate one or more aspects of the present disclosure.

[0090] Example 1. A regulated switched capacitor converter (SCC) comprising a first I / O terminal and a second I / O terminal, a rectifier coupled to the second I / O terminal, a first capacitor coupled between a first voltage node and a ground reference, a switch ladder, and a variable voltage converter. The switch ladder is coupled between the first I / O terminal and the first voltage node and comprises a first switch, a second switch, and a second capacitor. The first switch is coupled to the first capacitor at the first voltage node. The second switch is coupled to the first switch at the second voltage node and is also coupled between the first I / O terminal and the first switch. The second capacitor is coupled between the second voltage node and a node of the rectifier. The variable voltage converter is coupled between the first voltage node and the second I / O terminal and is configured to provide a variable voltage drop between the first voltage node and the second I / O terminal. In a preferred embodiment, the variable voltage switching converter comprises a switching power stage and an inductor.

[0091] Example 2. The regulated SCC of Example 1, wherein the variable voltage switching converter is a buck converter configured to step down a first voltage of a first voltage node and provide a resulting stepped down voltage at a second I / O terminal when the regulated SCC is operated in a mode in which a positive current flows into the first I / O terminal and out of the second I / O terminal.

[0092] Example 3. The regulated SCC according to Example 1, wherein the variable voltage switching converter is a boost converter configured to step up a first voltage of a first voltage node and provide a resulting boosted voltage at a second I / O terminal when the regulated SCC is operated in a mode in which a positive current flows into the first I / O terminal and out of the second I / O terminal.

[0093] Example 4. The regulated SCC of Example 1, wherein the variable voltage switching converter is a buck / boost converter configured to operate in a first mode in which a first voltage at a first voltage node is stepped down to provide a resulting stepped down voltage at a second I / O terminal, and in a second mode in which the first voltage is stepped up to provide a resulting stepped up voltage at a second I / O terminal when the regulated switched capacitor converter is operated in a mode in which a positive current flows into the first I / O terminal and out of the second I / O terminal.

[0094] Example 5. The regulated SCC of Example 1, wherein the variable voltage switching converter sets an average base current flowing into the variable voltage switching converter from the first voltage node, and wherein the switch ladder and the rectifier provide a multiplied current to the second terminal, wherein the multiplied current has an average value that is amplified by N relative to the average base current, wherein N is dependent on the number of switches in the switch ladder.

[0095] Example 6. The regulated SCC of Example 1, wherein a first average current flows to the first terminal and a second average current flows from the second terminal, wherein the second average current is X times higher than the first average current, and wherein X is greater than 1 and is not an integer.

[0096] Example 7. The regulated SCC of embodiment 1, wherein the switch ladder further comprises: a third switch coupled to the second switch at a third voltage node and coupled between the first I / O terminal and the second switch; and a third capacitor coupled between the third voltage node and the second node of the rectifier.

[0097] Example 8. The regulated SCC of Example 1, wherein the first I / O terminal is an input for coupling to a power source, the second I / O terminal is an output for coupling to a load, and an output voltage at the output is stepped down relative to an input voltage at the input.

[0098] Example 9. The regulated SCC of Example 1, wherein the regulated SCC is configured to operate as a buck converter during a first interval, wherein a positive current flows into the first I / O terminal and out of the second I / O terminal, and wherein a voltage at the second I / O terminal is stepped down relative to a voltage at the first I / O terminal, and wherein the converter is configured to operate as a boost converter during a second interval, wherein a positive current flows into the second I / O terminal and out of the first I / O terminal, and wherein a voltage at the first I / O terminal is stepped up relative to a voltage at the second I / O terminal.

[0099] Example 10. A regulated SCC system includes the regulated SCC of Example 1 and a controller. The controller is configured to generate a first control signal for a first switch, a second control signal for a second switch, and a power level control signal for switching a variable voltage switching converter. The power level control signal can be used to control a variable voltage drop across the variable voltage switching converter and can be used to regulate an output voltage of the regulated SCC system.

[0100] Example 11. The regulated SCC system of Example 10, wherein the variable voltage switching converter comprises at least one of a buck converter, a boost converter, and a buck / boost converter, and the power stage control signal controls conductance of a switch within the power stage.

[0101] Example 12. The regulated SCC system of Example 10, wherein the rectifier comprises a first half-bridge comprising: a first rectifier switch having a conductivity controlled by the second control signal; and a second rectifier switch having a conductivity controlled by the first control signal.

[0102] Example 13. The regulated SCC system of Example 10, wherein the controller further comprises: a closed-loop controller configured to generate a power stage control signal; and an open-loop controller configured to generate the first control signal and the second control signal.

[0103] Example 14. The regulated SCC system of Example 10, wherein a frequency of the first control signal is different than a frequency of the power stage control signal.

[0104] Example 15. The regulated SCC system of Example 10, wherein the first I / O terminal is an input for coupling to a power source, the second I / O terminal is an output for coupling to a load, and an output voltage at the output is stepped down relative to an input voltage at the input, and wherein the controller is further configured to: sense the output voltage at the second I / O terminal; and generate a power stage control signal based on the output voltage to regulate the output voltage to a desired target voltage.

[0105] Example 16. The regulated SCC system of Example 10, wherein the controller is configured to: operate the regulated switched capacitor converter system as a buck converter during a first interval, wherein a positive current flows into a first I / O terminal and out of a second I / O terminal, a voltage at the second I / O terminal is stepped down relative to a voltage at the first I / O terminal, and generate a power stage control signal to regulate the voltage at the second I / O terminal; and operate the regulated SCC system as a boost converter during a second interval, wherein a positive current flows into the second I / O terminal and out of the first I / O terminal, a voltage at the first I / O terminal is stepped up relative to a voltage at the second I / O terminal, and generate a power stage control signal to regulate the voltage at the first I / O terminal.

[0106] Example 17. A method for controlling a regulated SCC, the regulated SCC comprising a first input / output (I / O) terminal and a second input / output (I / O) terminal, a rectifier coupled to the second I / O terminal, a first capacitor coupled between a first voltage node and a reference voltage, a switch ladder, and a variable voltage switching converter. The switch ladder comprises a first switch and a second switch coupled between the first I / O terminal and the first voltage node, and a second capacitor coupling an interconnection node of the first switch and the second switch to a first node of the rectifier. The variable voltage switching converter comprises a power stage and an inductor, and is coupled between the first voltage node and the second I / O terminal. The method comprises generating a first control signal for controlling the conductivity of the first switch, generating a second control signal for controlling the conductivity of the second switch, and generating a power stage control signal for controlling the conductivity of the power stage. The generated power stage control signal can be used to adjust the output voltage of the regulated switched capacitor converter.

[0107] Example 18. The method of Example 17, further comprising sensing a second voltage at the second I / O terminal, and wherein the power stage control signal is generated based on the sensed second voltage to regulate the second voltage to a desired target voltage.

[0108] Example 19. The method of Example 17 also includes: operating the regulated SCC as a buck converter during a first interval, wherein a positive current flows into the first I / O terminal and flows out of the second I / O terminal, a voltage at the second I / O terminal is stepped down relative to a voltage at the first I / O terminal, and generating a power stage control signal to regulate the voltage at the second I / O terminal; and operating the regulated SCC as a boost converter during a second interval, wherein a positive current flows into the second I / O terminal and flows out of the first I / O terminal, a voltage at the first I / O terminal is stepped up relative to a voltage at the second I / O terminal, and generating a power stage control signal to regulate the voltage at the first I / O terminal.

[0109] As used herein, the terms "having", "including", "comprising", and the like are open terms that indicate the presence of stated elements or features but do not preclude additional elements or features. The articles "a", "an", and "the" are intended to include the plural as well as the singular, unless the context clearly indicates otherwise.

[0110] It should be understood that the features of the various embodiments described herein may be combined with each other, unless specifically stated otherwise.

[0111] Although specific embodiments have been shown and described herein, it will be appreciated by those skilled in the art that various alternative and / or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. This application is intended to cover any modifications or variations of the specific embodiments discussed herein. Therefore, the present invention is limited only by the claims and their equivalents. ​

Claims

1. A regulated switched capacitor converter SCC, comprising: A first I / O terminal; Second I / O terminal; a rectifier coupled to the second I / O terminal; a first capacitor coupled between the first voltage node and a reference node; a switch ladder coupled between the first I / O terminal and the first voltage node and comprising: a first switch coupled to the first voltage node, a second switch coupled to the first switch at a second voltage node and coupled between the first I / O terminal and the second voltage node, and a second capacitor coupled between the second voltage node and the first node of the rectifier; A variable voltage switching converter is coupled between the first voltage node and the second I / O terminal and is configured to provide a variable voltage drop between the first voltage node and the second I / O terminal, the variable voltage switching converter comprising a power stage and an inductor.

2. The regulated SCC of claim 1 , wherein the variable voltage switching converter is a buck converter configured to step down a first voltage of the first voltage node and provide a resulting stepped down voltage at the second I / O terminal when the regulated SCC is operated in a mode in which a positive current flows into the first I / O terminal and out of the second I / O terminal.

3. The regulated SCC of claim 1 , wherein the variable voltage switching converter is a boost converter configured to step up a first voltage of the first voltage node and provide a resulting boosted voltage at the second I / O terminal when the regulated SCC is operated in a mode in which a positive current flows into the first I / O terminal and out of the second I / O terminal.

4. The regulated SCC of claim 1 , wherein the variable voltage switching converter is a buck / boost converter configured to operate in a first mode in which a first voltage at the first voltage node is stepped down to provide a resulting stepped down voltage at the second I / O terminal, and in a second mode in which the first voltage is stepped up to provide a resulting stepped up voltage at the second I / O terminal when the regulated switched capacitor converter is operated in a mode in which a positive current flows into the first I / O terminal and out of the second I / O terminal.

5. The regulated SCC of claim 1 , wherein the variable voltage switching converter sets an average base current flowing from the first voltage node into the variable voltage switching converter, and wherein the switching ladder and the rectifier supply a multiplied current to the second I / O terminal, wherein the multiplied current has an average value that is amplified by N relative to the average base current, wherein N is dependent on the number of switches in the switching ladder.

6. The regulated SCC of claim 1 , wherein a first average current flows to the first I / O terminal and a second average current flows from the second I / O terminal, wherein the second average current is X times higher than the first average current, and wherein X is greater than 1 and is not an integer.

7. The regulated SCC of claim 1 , wherein the switching ladder further comprises: a third switch coupled to the second switch at a third voltage node and coupled between the first I / O terminal and the second switch; as well as A third capacitor is coupled between the third voltage node and the second node of the rectifier.

8. The regulated SCC of claim 1 , wherein the first I / O terminal is an input for coupling to a power source, the second I / O terminal is an output for coupling to a load, and an output voltage at the output is stepped down relative to an input voltage at the input.

9. The regulated SCC according to claim 1, wherein the regulated SCC is configured to operate as a buck converter during a first interval, wherein a positive current flows into the first I / O terminal and out of the second I / O terminal, and a voltage at the second I / O terminal is stepped down relative to a voltage at the first I / O terminal, and The converter is configured to operate as a boost converter during a second interval, wherein a positive current flows into the second I / O terminal and out of the first I / O terminal, and a voltage at the first I / O terminal is stepped up relative to a voltage at the second I / O terminal.

10. A regulated switched capacitor converter (SCC) system, comprising: A first I / O terminal; Second I / O terminal; a rectifier coupled to the second I / O terminal; a first capacitor coupled between the first voltage node and a reference node; a switch ladder coupled between the first I / O terminal and the first voltage node and comprising: a first switch coupled to the first voltage node, a second switch coupled to the first switch at a second voltage node and coupled between the first I / O terminal and the second voltage node, and a second capacitor coupled between the second voltage node and the first node of the rectifier; a variable voltage switching converter coupled between the first voltage node and the second I / O terminal and configured to provide a variable voltage drop between the first voltage node and the second I / O terminal, the variable voltage switching converter comprising a power stage and an inductor; and A controller is configured to generate a first control signal for the first switch, a second control signal for the second switch, and a power stage control signal for the power stage.

11. The regulated SCC system of claim 10, wherein the variable voltage switching converter comprises at least one of a buck converter, a boost converter, and a buck / boost converter, and the power stage control signal controls the conductance of a switch within the power stage.

12. The regulated SCC system of claim 10, wherein the rectifier comprises a first half-bridge, the first half-bridge comprising: a first rectifier switch having a conductivity controlled by the second control signal; as well as A second rectifier switch has a conductivity controlled by the first control signal.

13. The regulated SCC system of claim 10, wherein the controller further comprises: a closed-loop controller configured to generate the power stage control signal; as well as An open-loop controller is configured to generate the first control signal and the second control signal.

14. The regulated SCC system of claim 10, wherein a frequency of the first control signal is different than a frequency of the power stage control signal.

15. The regulated SCC system of claim 10, wherein the first I / O terminal is an input for coupling to a power source, the second I / O terminal is an output for coupling to a load, and an output voltage at the output is stepped down relative to an input voltage at the input, and wherein the controller is further configured to: sensing the output voltage at the second I / O terminal; and The power stage control signal is generated based on the output voltage to regulate the output voltage to a desired target voltage.

16. The regulated SCC system of claim 10, wherein the controller is configured to: operating the regulated SCC system as a buck converter during a first interval, wherein a positive current flows into the first I / O terminal and out of the second I / O terminal, a voltage at the second I / O terminal is stepped down relative to a voltage at the first I / O terminal, and generating the power stage control signal to regulate the voltage at the second I / O terminal; and The regulated SCC system is operated as a boost converter during a second interval, wherein a positive current flows into the second I / O terminal and out of the first I / O terminal, a voltage at the first I / O terminal is stepped up relative to a voltage at the second I / O terminal, and the power stage control signal is generated to regulate the voltage at the first I / O terminal.

17. A method for controlling a regulated switched capacitor converter (SCC), the SCC comprising a first I / O terminal and a second I / O terminal, a rectifier coupled to the second I / O terminal, a first capacitor coupled between a first voltage node and a reference voltage, a switch ladder comprising a first switch and a second switch coupled between the first I / O terminal and the first voltage node, and a second capacitor coupling an interconnection node of the first switch and the second switch to a first node of the rectifier, and a variable voltage switching converter comprising a power stage and an inductor, and the variable voltage switching converter is coupled between the first voltage node and the second I / O terminal, the method comprising: generating a first control signal for controlling conductivity of the first switch; generating a second control signal for controlling conductivity of the second switch; as well as A power stage control signal is generated for controlling the conductance of the power stage.

18. The method according to claim 17, further comprising: sensing a second voltage at the second I / O terminal, and The power stage control signal is generated based on the sensed second voltage to regulate the second voltage to a desired target voltage.

19. The method according to claim 17, further comprising: operating the regulated SCC as a buck converter during a first interval, wherein a positive current flows into the first I / O terminal and out of the second I / O terminal, a voltage at the second I / O terminal is stepped down relative to a voltage at the first I / O terminal, and generating the power stage control signal to regulate the voltage at the second I / O terminal; as well as The regulated SCC is operated as a boost converter during a second interval, wherein a positive current flows into the second I / O terminal and out of the first I / O terminal, a voltage at the first I / O terminal is stepped up relative to a voltage at the second I / O terminal, and the power stage control signal is generated to regulate the voltage at the first I / O terminal.

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