Shouxiang Li

A Family of Two-Switch Boosting Switched-Capacitor Converters

A family of “Two-Switch Boosting Switched-Capacitor Converters (TBSC)” is introduced, which distinguishes itself from the prior arts by symmetrically interleaved operation, reduced output ripple, low yet even voltage stress on components, and systematic expandability. Along with the topologies, a modeling method is formulated, which provokes the converter regulation method through duty cycle and frequency adjustment. In addition, the paper also provides guidance for circuit components and parameter selection. A 1-kW 3X TBSC was built to demonstrate the converter feasibility, regulation capability via duty cycle and frequency, which achieved a peak efficiency of 97.5% at the rated power.

A New Hybrid Boosting Converter for Renewable Energy Applications

A hybrid boosting converter (HBC) with collective advantages of regulation capability from its boost structure and gain enhancement from its voltage multiplier structure is proposed in this paper. The new converter incorporates a bipolar voltage multiplier, featuring symmetrical configuration, single inductor and single switch, high gain capability with wide regulation range, low component stress, small output ripple and flexible extension, which make it suitable for front-end PV system and some other renewable energy applications. The operation principal, component stress, and voltage ripple are analyzed in this paper. Performance comparison and evaluation with a number of previous single-switch single-inductor converters are provided. A 200-W 35 to 380 V second-order HBC prototype was built with peak efficiency at 95.44%. The experimental results confirms the feasibility of the proposed converter.

A New Single-Switch Isolated High-Gain Hybrid Boosting Converter

A new single-switch isolated hybrid boosting converter featuring low-component stress, simple control, high efficiency, high power density, and flexible gain extension is proposed in this paper. At the primary side, a new design of energy regenerative snubber is proposed to provide soft-switching condition, suppress voltage spike, and recycle leakage energy. At secondary side, a bipolar voltage multiplier (BVM) structure which enhances the gain boosting capacity, reduces the output ripple, and facilitates fly-back-forward operation of transformer is proposed. Based on this structure, the transformer can deliver energy to the output at both magnetizing and magnetic resetting stages. In addition, the bulky high-voltage-rated output filter capacitor can be eliminated due to the cascaded and autobalanced capacitors in the BVM structure. A 200-W 35- to 400-V prototype is built to demonstrate the feasibility of the proposed topology. The peak efficiency of 93.8% is reached and 91.2% is achieved at rated power.

Analysis and design of a 1-kW 3X interleaved switched-capacitor DC-DC converter

Switched-Capacitor (SC) technologies have been an active research topic for DC-DC power conversion for many years. Without participation of inductor, they have the potential to achieve small size, light weight and high-power density. From literature research, most of the SC converters reported were implemented in low power level in the range of 5 to 50 watts. Typically they have discontinuous input current and use a large number of active switches. Recently, a new two-switch boost switched-capacitor (TBSC) converter was reported in [1] that achieves automatic interleaved DC-DC conversion with only two active switches. The TBSC converter can step up the input voltage by N times, where N=2, 3, 4, ..., with continuous input current and small output voltage ripple. This paper explores the feasibility of engaging this TBSC converter for high power applications in the kilowatts level with 3X gain. A simplified modeling method and analysis method is presented to provide solid guidance for analysis and design of the TBSC converter. A 1-kW 150/450-V prototype was implemented that achieved a peak efficiency of 97.5% at full load.

Decoupled PWM Plus Phase-Shift Control for a Dual-Half-Bridge Bidirectional DC–DC Converter

This paper presents the analysis of low leakage inductance current regions, small-signal model, and decoupled control for a dual-half-bridge isolated bidirectional dc–dc converter with pulse width modulation plus phase-shift strategy. Traditionally, the duty cycle of the transistors is fixed at 0.5 and only the phase-shift is varied to regulate the output voltage. With PPS control, two control freedoms—the duty cycle is used to regulate the voltage gain and phase-shift is used to control the power flow—can be obtained to expand input-voltage variation range. In addition, since the amplitude of leakage inductance current is limited, the current stresses of transistors can be reduced. According to the analysis, there exists a region in which higher leakage inductance current leads to lower output power and thus, causes more conduction loss. Attention should be paid to avoid this operation region. Then, a small-signal model is derived in the low conduction loss region with the state space averaging method to facilitate the closed-loop design. In addition, a decoupled control strategy is proposed to eliminate the interactions between phase-shift ratio and duty cycle, so as to simplify the proportional-integral controller design significantly. A prototype was built to verify the theoretical analysis.

A hybrid bidirectional DC-DC converter for dual-voltage automotive systems

With the increasing power demand of automotive systems, a 42V power system has the trend to coexist with the traditional 14V system in order to decrease the system current stress. In the dual-voltage and dual-battery architecture, a compact, high efficient and bidirectional DC/DC converter is typically needed. In this paper, a hybrid bidirectional DC-DC converter for 42/14V dual-voltage automotive systems is presented. This converter is a hybrid combination of a switched-capacitor converter and an inductor-based converter with low number of components, whose input current ripple and peak charging current are small with the help of the inductor. The nominal duty cycle for the 42/14V system is 0.5, so it will not go to extreme values even if the battery is overcharged to a higher voltage value or is depleted to a lower voltage value, therefore increasing the voltage-gain range and ensuring high efficiency. A comprehensive analysis of steady-state operation, small signal model and component stress is given. A 42/14V prototype rated at 20∼120W with a peak efficiency of 97.8% in boost mode and 98.3% in buck mode was built to verify the analyses.

A family of resonant two-switch boosting switched-capacitor converter with ZVS operation and a wide voltage-gain range

In this paper, a family of Resonant Two-switch Boosting Switched-capacitor Converters (RTBSCs) with ZVS operation and a wide voltage-gain range is proposed. By adding a small resonant inductor to the TBSCs, the two bulky capacitor banks can be replaced by two much smaller resonant capacitors. Further by operating it above the resonant frequency, the transistors are ZVS turned on and diodes are ZCS turned off. The soft switching operation makes it possible to increase the switching frequency without sacrificing the overall efficiency, so the size can be decreased. Moreover, the voltage-gain range of the RTBSCs is increased significantly. As a result, the input-voltage range can be increased if the output voltage is regulated. The operation principle, voltage-gain curves, output characteristics and the voltage/current stress of the resonant tank for this family are analyzed. A 3X RTBSC prototype rated at 20∼130W with a peak efficiency 98% was built to verify the analysis.

Analysis and modelling of a bidirectional push-pull converter with PWM plus phase-shift control

This paper presents analysis and modeling for a bidirectional push-pull dc-dc converter. In particular, attention is paid to leakage current reduction with PWM plus phase-shift control. The leakage current in different operating modes has been compared to identify the efficient modes for various operation conditions. The state space averaging method is adopted to derive the small signal and large signal models of the most efficient mode. A 30~70V/300V prototype was built. Both simulation results and experimental results prove the validity of the model.

A new hybrid boosting converter

A new Hybrid Boosting Converter(HBC) is proposed in this paper. It combines the advantages of regulation capability of traditional inductor based DC-DC converters and gain boosting ability of switched capacitor converters. It is capable of boosting the input voltage to ten times with single active switch and one inductor while maintaining high efficiency. In addition, the switch stress is low and output voltage has a wide regulation range. A modeling method for the proposed converter is presented in this paper. The PWM regulation capability is confirmed by theory and experiment. A 200W, 35V to 380V HBC prototype was built that demonstrated a peak efficiency of 95.44% using normal electrolytic capacitors.