Switched-Capacitor Converter State Model Generator

Traditionally, switched-capacitor (SC) converters have suffered from high transient currents, which limit both the efficiency and power density of such converters. Soft-charging operation can be employed to eliminate the current transients and greatly improve the power density of SC converters. In this approach, a second-stage magnetic converter is cascaded with the SC stage to act as a controlled current load. Another approach is to use resonant SC converters with zero-current switching. This paper shows that resonant and soft-charging operations of SC converters are closely related, and a technique will be proposed, which achieves either operation by adding a single inductor to existing SC topologies. In addition, since most preexisting resonant or soft-charging SC converters were devised in an ad-hoc manner, this paper formulates an analytical method that can determine whether an existing conventional SC converter topology is compatible with the proposed approach. A number of common SC topologies are analyzed, including Dickson, series-parallel, ladder, Fibonacci, and doubler configurations. Through comparison to simulated results, as well as experimental work, the proposed method is validated and a family of high-performance SC converters is obtained.

Switched Capacitor (SC) DC-DC converters are transformer and inductor less DC-DC converters that are used to step up, step down or invert a supply voltage where the power requirements are usually less than 5W. The outputs of the currently available SC converters are referenced with respect to the input supply ground. Though SC converters are ideally suited for many low power miniaturized industrial applications due to their small size, lack of ground isolation in SC converters prevents their use in low power applications that require ground isolation due to ground noise sensitivity of the load. The work presented in this paper introduces the concept of ground isolation in a buck SC converter without the use of isolation transformers like conventional DC-DC converters. Switched capacitors driven by opto-isolated drives are employed to transfer power from the source to the load. The introduction of ground isolation in SC converters significantly widens its scope of application in industry. A state space averaged (SSA) model of the SC converter is developed to study its dynamic and steady state characteristics. The validity of the SSA model is verified with measurements on the hardware model.

A ground-isolated switched capacitor (SC) dc-dc converter-based current equalization scheme for partially shaded photovoltaic (PV) strings of a grid-connected system is presented. SC converters are compact, light, and have very high efficiency even for a wide variation in load under certain operating conditions. These features make them ideal for integration with the PV module for current equalization. The factors affecting the maximum output power that the SC converter can deliver, the limiting value of the maximum output power, and efficiency issues of the SC converter are studied. These studies are required to optimize the design of the equalizing SC converter and to maximize its efficiency. A novel algorithm that utilizes the results of the aforementioned analysis to maximize the net power available due to the SC converter-based current equalization scheme for grid-connected applications is proposed. Experimental results showing the advantages of current equalization with SC converters as compared to that with conventional dc-dc converters are presented.

Switched capacitor (SC) dc–dc converters, which have traditionally been used for on-chip power supplies, are now being considered for medium to high-power applications. This paper presents a method for automatically synthesizing SC converters as well as deriving the expressions for their charge-multipliers. Charge multipliers can be used to calculate important design characteristics such as converter output voltage regulation, efficiency, and component current ratings, which can then be used to appraise different topologies. However, whilst a full appraisal of converters also requires component voltage ratings, this work is the first step in developing an automatic software tool that will employ a search-based algorithm to generate optimum SC topologies for a given application. The method is based on the proposition that all SC converters can be synthesized from a so-called “basic cell”. The automatic derivation and solution of the charge transfer equations for a traditional Fibonacci SC converter is presented as an example of the proposed method, which is validated against existing analytic equations as well as a detailed Spice simulation. The automatic calculation of the charge-multipliers for two other well-known SC converters is also demonstrated, including a new, arbitrarily generated circuit, which again is validated against detailed spice simulations.

Switched capacitor (SC) converters are becoming quite popular for use in DC-DC power conversion. The concept of equivalent resistance in SC converters is frequently used to determine the conduction losses due to the load current. A variety of methodologies have been presented to predict the equivalent resistance in hard-switched SC converters. These works, however, did not consider the effect of stray inductance on equivalent resistance. Current power converter design practices favor higher switching frequencies, moving hard-switched SC converters into operating areas in which stray inductance affects converter performance. This paper presents an analytic equation that can be used to evaluate the effects of stray inductance on the equivalent resistance of switched capacitor converters. The concepts proposed here are verified by both digital simulation and a prototype converter. The equations presented can be used to evaluate the effects of stray inductance on SC converter performance, thereby helping designers set a maximum operating frequency to limit its effect.

The switched-capacitor (SC) converters are gaining popularity in some practical use. Its resonant counterpart, with a small inductor as current shaper in the architecture, has the advantage of smoother charging current, smaller voltage and current variation ratio and so on. This paper presents a generic and thorough analysis of the efficiency mechanism of the resonant switched-capacitor converter (RSCC). It decomposes any RSCC into three basic sub-circuits of SRLC circuit, CRLC circuit and SRLC² circuit, which are analyzed and compared with corresponding sub-circuits of SCC, respectively. Then the overall efficiency of a RSCC could be derived. Furthermore, a new calculation method of output impedance is developed in another perspective to reveal the high efficiency mechanism of RSCC. On this basis, the high efficiency operation condition for RSCC could be obtained. Finally, a resonant bridge modular switched-capacitor converter (RBMSCC) is proposed and built for example of extended implementation of RSCC to achieve high efficiency operation. Some useful comments for designing resonant switched-capacitor converters are suggested.

This paper presents a fully-integrated reconfigurable switched-capacitor (SC) converter that extracts power from a 1. 5-1.SV input voltage and regulates a 0. 3-1.SV output voltage. The converter employs a proposed output-boosting scheme that increases the output voltage of the conventional 3-ratio SC converter power-efficiently. Therefore, the voltage conversion ratios increase from 3 to 14 without the need for additional cascaded SC converter stages. The proposed converter was designed and simulated with a 0. 1S$\mu$m CMOS process and achieved a peak efficiency of 86.7% and a maximum output current of 0.8 mA.

This article focuses on the modeling of a novel switched-capacitor converter with phase shift modulation, which is proposed in the previous work. This switched-capacitor converter can realize high voltage gain with high efficiency and power density based on its modular topology. However, it is difficult to build the accurate and standard models for the general form with any number of modules as the numerous passive components will result in a high order model. This problem limits the voltage regulation ability and dynamic performance of switched-capacitor converter, especially for high voltage gain application. In this article, the general steady-state model is first derived. Then, the relationship between the order of dynamic model based on the conventional method and the number of modules in converter is derived to illustrate the complexity and high computational cost. Therefore, a simplified modeling method is proposed, which can reduce the order and complexity of the system, and has considerable consistency compared with precise model. The approximate modeling method can be easily applied on general form of the converter and is friendlier for controller design. Simulation verifies the theoretical correctness of the modeling. And experiment on a prototype whose controller is designed according to the model proves the practicability.

In this paper, an ultra-high-speed, low-loss gate driver circuit using a CMOS-type class-D oscillator and a Switched Capacitor (SC) converter directly driven by it are proposed and demonstrated. Conventional buffer drivers suffer from large power losses, making it difficult to operate SC converters in the several hundreds of MHz range. The proposed driver circuit achieves low-loss operation in this frequency range by employing an inductor-based constant-current gate drive that self-oscillates utilizing CMOS-type class-D oscillator. This approach enables a significant reduction of the flying capacitor value in the SC converter. The proposed oscillator driver and SC converter are implemented using only 1.0V transistors in a 65nm CMOS process. The oscillator inductors and flying capacitors are all integrated on-chip. The measurement results show that the SC converter can be driven at 480MHz with a driver power loss of 61mW, achieving a maximum efficiency of 60.2% at an output current of 350mA.

A power management unit (PMU) with battery extender and output load regulation is presented using 0.18$\mu$m CMOS technology. For designing few sub-circuits of the PMU, subthreshold region of MOSFET is utilized, which significantly contributes to achieve low power operation. The proposed PMU consists of a voltage regulator, a voltage monitor, a battery backup module and two DC-DC Switched Capacitor (SC) Converters. The regulator output voltage V OUT is regulated at 0.95 V and 0.968 V at input voltages of 0.98 V and 1.33 V respectively. To ensure continuous operation at the load circuit, a battery extender module is implemented in case of unavailability of EH source. The power consumption of the PMU at input voltages of 0.98 V and 1.33 V is 46nW and 1.567 $\mu$W respectively. Near threshold operation is ensured at the load side by further regulating the voltage at the output to 0.67 V and 0.5 V using 3:2 and 2:1 SC Converters respectively. The current consumption of the 3:2 and 2:1 SC Converters is 748 nA and 751 nA respectively. The proposed PMU can deliver output current up to 1 mA at 1.33 V of input voltage and is suitable for numerous applications where low power operation is essential as it consumes a small amount of power.

In this paper, a novel topology of switched-capacitor converter is proposed. Compared with the existing switched-capacitor topologies, such as the Dickson-based switched-capacitor converter or the ladder switched-capacitor converter, it limits both voltage stress and current stress of components under lower level, which reduces the volume of capacitor banks and the conduction loss. These characteristics can help high-power density and high-efficiency design, especially in high-voltage-gain applications. The phase shift modulation strategy corresponding to the proposed switched-capacitor converter is also presented in this paper. With phase shift modulation, voltage gain can be adjusted as continuous value. The voltage regulation ability makes up the defect of conventional switched-capacitor converters, and the ZVS operation of all the switching devices is also achieved with the proposed modulation method so that the WBG devices can play more strength in the converter with higher switching frequency. The derivation of the circuit topology and phase shift modulation will be introduced in this paper. The steady analysis and performance comparison will prove the advantage of the proposed converter. A 600-W prototype is built, and the experiment results are presented to validate the proposed converter.

Photovoltaic (PV) systems consist of multiple dc-dc converters, including a front-end converter for PV string control, a bidirectional converter for battery regulation, and voltage equalizer to preclude partial-shading issues, and hence they are prone to be complex and costly. To cope with this issue, this paper proposes the PWM- and PFM-controlled switched capacitor converter (SCC)-based multiport converter (MPC) integrating voltage equalizer. The proposed MPC can be derived by integrating a bidirectional PWM converter, series-resonant converter (SRC), and SCC. The PWM converter and SRC regulate battery and load voltages, respectively, while the SCC plays a role of the voltage equalization. Not only is the system as a whole dramatically simplified but also the circuit element count is significantly reduced thanks to the integration. The 150-W prototype for three PV modules was built for verification. The experimental results demonstrated the extractable maximum power from PV modules was significantly improved by the SCC, while the battery and load voltages were individually regulated by the PWM and PFM controls, respectively.

In this article, basic cell (BC) of a novel switched capacitor converter (SCC) has been proposed first. After that, the generalized structure of proposed SCC is developed. The developed SCC requires reduced number of switches, drivers, diodes, capacitors, and lower number of conducting switches in current flow paths and capacitor charging paths as compared to the other recently developed SCCs. A switched capacitor multilevel inverter (SCMLI) utilizing two numbers of generalized SCCs is developed next. Further, cascaded extension of proposed SCMLI is realized and analyzed for symmetric and asymmetric dc source configurations. A detail analysis of optimum selection of capacitance for switched capacitors of 13-level SCMLI is presented. An extensive comparison study shows that the proposed SCMLI requires lower number of components as compared to other SCMLIs. Further, the proposed structure has minimum cost function per level per boosting factor as compared to the other SCMLIs. Extensive experimental results considering fundamental switching frequency scheme are presented to validate the merits and effectiveness of the proposed structure.

Switched capacitor (SC) dc–dc converters are showing great potential for new applications such as data centres, electric vehicles, and power transmission. Many SC topologies have been synthesized on an ad-hoc basis, although new computer methods are being introduced to formalize this process. This article presents a general synthesis technique that can be incorporated into a computer algorithm to assist with the development of new SC circuits. The technique is based on interleaving SC converter circuits, where two unipolar converters are connected in parallel, and each leg is driven by separate, complementary gate signals. By applying this method to the traditional Ladder SC converter, a topology termed a simplified interleaved ladder (SIL) converter, is synthesized and tested using a hardware prototype. The resonant implementation of the SIL converter has desirable features for MV/LV applications when compared with other existing SC circuits.

In recent years, there has been an ever-increasing interest in monolithic power supplies. Integrating the power supply with the application has many direct benefits, including a reduction of the bill of materials and reduced size. Even more substantial are the potential efficiency gains due to reduced power delivery network losses and voltage margins, especially in a world dominated by energy limited devices where this translates directly into improved battery life. However, to warrant a migration to integrated power supplies, it is crucial that these gains do not get eclipsed by the decreased efficiency of the power converter caused by the reduced quality of integrated passives. Switched-Capacitor (SC) converters have become more and more popular because, contrary to inductive converters, they only use transistors and capacitors, both of which are native to CMOS technologies and scale well into deep-submicron nodes. The maximal efficiency of an SC converter depends on two factors [1]: a topological parameter whose optimal value depends on the Voltage Conversion Ratio (VCR), and a, the relative size of the parasitic, so-called Bottom-Plate (BP), capacitance to the flying capacitance. The further the VCR is removed from 1/1 and the larger a, the lower the efficiency that is obtained. With a typically around 1.5% for MOM- and MIM-, and 7% for MOS capacitors, an SC converter could theoretically achieve an efficiency of 89% and 79% respectively for a 1/2 conversion [1]. Due to additional losses (control, leakage, etc.), this efficiency ceiling is lower, but its existence is still confirmed by previous work. The highest reported monolithic SC converter efficiencies in baseline CMOS are 87% [2], although at a more favorable VCR of 4/5, and 85% [3], both using MIM capacitors. Higher efficiencies have been demonstrated using high-density Deep-Trench (90%) [4] or Ferro-Electric (91% in 1/2) [5] capacitors, which have reportedly up to 25 times smaller α. However, these capacitors are not part of baseline CMOS and thus require additional masks and costs.