The theoretical performance limits of two-phase switched-capacitor (SC) DC-DC power converters are discussed in this paper. For a given number of capacitors k, the complete set of attainable DC conversion ratios is found. The maximum step-up or step-down ratio is given by the k/sup th/ Fibonacci number, while the bound on the number of switches required in any SC circuit is 3k-2. Practical implications, illustrated by several SC power converter examples, include savings in the number of components required for a given application, and the ability to construct SC power converters that can maintain the output voltage regulation and high conversion efficiency over a wide range of input voltage variations. Limits found for the output resistance and efficiency can be used for selection and comparison of SC power converters. >

Performance limits of switched-capacitor DC-DC converters

A new family of a single-switch three-diode dc-dc pulsewidth-modulated (PWM) converters operating at constant frequency and constant duty cycle is presented in this paper. The proposed converters are different from the conventional dc-dc step-up converters, and they posses higher voltage gain with small output voltage ripples. Other advantages of the proposed converters include lower voltage stress on the semiconductor devices, simple structure, and control. Moreover, the reduced voltage stress on the diodes allows using Schottky diodes for alleviating the reverse-recovery current problem, as well as decreasing the switching and conduction losses. The principle of operation, theoretical analysis, and experimental results of one prototype rated 40 W and operating at 94 kHz are provided in this paper to verify the performance of this new family of converters.

A Family of Single-Switch PWM Converters With High Step-Up Conversion Ratio

One of the main orientations in power electronics in the last decade has been the development of switching-mode converters without inductors and transformers. Light weight, small size and high power density are the result of using only switches and capacitors in the power stage of these converters. Thus, they serve as ideal power supplies for mobile electronic systems (e.g. cellular phones, personal digital assistants, and so forth). Switched-capacitor (SC) converters, with their large voltage conversion ratio, promise to be a response to such challenges of the 21st century as high-efficiency converters with low EMI emissions and the ability to realize steep step-down of the voltage (to 3 V or even a smaller supply voltage for integrated circuits) or steep step-up of the voltage for automotive industry or Internet services in the telecom industry. This paper is a tutorial of the main results in SC-converter research and design.

Switched-capacitor power electronics circuits

In this tutorial, the utility of a fuzzy system is demonstrated by providing a broad overview, emphasizing analog mode hardware, along with a discussion of the author's original work. First, the difference between deterministic words and fuzzy words is explained as well as fuzzy logic. The description of the system using mathematical equations, linguistic rules, or parameter distributions (e.g., neural networks) is discussed. Fuzzy inference and defuzzification algorithms are presented, and their hardware implementation is discussed. The fuzzy logic controller was used to stabilize a glass with wine balanced on a finger and a mouse moving around a plate on the tip of an inverted pendulum. >

A fuzzy inference engine in nonlinear analog mode and its application to a fuzzy logic control

A new step-up DC-to-DC power converter with high power density is presented. It contains no inductors or transformers. The controlled energy transfer from an unregulated voltage source to a regulated output voltage is realized through a switched-capacitor circuit. The operation of the switches in the power stage is dictated by a PWM-type feedback circuit. The new regulator is simulated by using an averaged state-space approach. The transient and steady-state waveforms, as well as the AC small-signal input-to-output and control-to-output transfer functions are obtained by both simulation and experiments. The power supply, implemented for a nominal power of 15 W, and input-to-output voltage ratio of 5/12, features high efficiency for this class of powers, small output voltage ripple, continuous input current, low weight and small size. >

Step-up DC power supply based on a switched-capacitor circuit

A small size emergency power supply was investigated. This was realized by adopting a quick detector of momentary power failure and a compact DC-DC converter. The power failure detector has a novel type of T-V (time-voltage) conversion using an SC (switched capacitor) integrator and can detect power failures at its earliest stage. The DC-DC converter was constructed by an SC transformer in which the voltage of each stage increases according to the form of the Fibonacci sequence. The proposed power supply is supplied with power from chargeable batteries for several minutes, while the computer system saves important data to an auxiliary memory such as a disk and can complete its emergency quit operation. The circuit configurations, operations and experimental results are presented. >

Emergency power supply for small computer systems

A new approach to a low ripple-noise switching converter is presented. The starting circuit is a basic switched-capacitor (SC) converter cell from which several types of low ripple-noise switching converters are generated. Two generated converters are employed for switching regulators hybridized by copper thick films on alumina substrates to realize low ripple noise. As a result, the ripple noise in the output voltages is reduced to less than 5 mVpp. Finally, this approach enables design of an ideal switching converter with zero input and output current ripple. >

A new approach to low ripple-noise switching converters on the basis of switched-capacitor converters

Current-Mode Analog Fuzzy Hardware with Voltage Input Interface and Normalization Locked Loop

A switched-capacitor (SC) DC-DC converter is developed to reduce the input current ripple and to achieve miniaturization A fixed-capacitor added to an original SC reduces the input current ripple This converter is miniaturized by a copper thick-film hybrid technique The features of this converter are as follows: (1) low input current ripple (one third compared with that of original SC DC-DC converters), (2) very high efficiency (90%), and (3) very high power density (23 W/in/sup 3/ in the 10 W class) >

New switched-capacitor DC-DC converter with low input current ripple and its hybridization

A voltage-input current-output membership function circuit (MFC) and a normalization locked loop (NLL) are proposed. They are useful building blocks for current-mode analog fuzzy hardware. The voltage-input current-output MFC consists of two-source-coupled-type operational transconductance amplifiers (OTAs). The MFC is used in the input parts of the analog fuzzy hardware system. The fuzzy hardware system can execute the singleton fuzzy control algorithm. In the algorithm, the weighted average operation is processed. When the weighted average operation is directly realized by analog circuits, a divider must be implemented. The NLL circuit, which can process the weighted average operation without the divider, is implemented using a one-source-coupled OTA. The proposed circuits were designed by using 2- mu m CMOS design rules and their operations were confirmed using SPICE simulations. >

Takahiro Inoue

Papers

Emergency power supply for small computer systems

A new approach to low ripple-noise switching converters on the basis of switched-capacitor converters

Current-Mode Analog Fuzzy Hardware with Voltage Input Interface and Normalization Locked Loop

New switched-capacitor DC-DC converter with low input current ripple and its hybridization

Current-mode analog fuzzy hardware with voltage input interface and normalization locked loop