Search

This work presents a 48-1V dc–dc converter with an on-chip switch and gallium nitride (GaN) hybrid power conversion. By series connecting a 12-level Dickson switched-capacitor with a two-phase switched-inductor circuit, the capacitors take over most of the 48-V voltage stresses. The circuit, thus, reduces to an equivalent 4-1V converter, making the on-chip 5-V transistor applicable for a 48-V high-voltage design. Due to the easy integration of on-chip switches and superior switch figures of merit over other 48-1V counterparts, this proposed design is able to achieve the highest switching frequency, the lowest external switch count, and the improved power density compared with other prior-state-of-the-arts. The prototype was fabricated using a 0.18- $\mu \text{m}$ BCD process with an evaluation board volume of 17 mm $\times $ 15 mm $\times $ 2.6 mm. The converter achieves a maximum 8-A loading capacity with the input range from 36 to 60 V and the output from 0.5 to 1 V. The measured peak power efficiency is 90.2%, and the power density is 998 A/in3 considering the power stage volume. [ABSTRACT FROM AUTHOR]

Series connection of SiC power MOSFET is an attractive approach to expand the blocking voltage of SiC devices, whereas the dynamic voltage balancing among the series-connected devices is the most critical challenge of the technique. In this article, a simple, fast, and cost-effective dynamic voltage balancing circuit of the series-connected SiC MOSFETs is proposed to suppress the voltage imbalance among the devices. The proposed circuit is composed of a resistor-capacitor (RC) snubber with a coupled inductor to effectively sense the voltage imbalance and add a compensated signal to the gate driving voltage. In the article, the operation principle of the proposed method is described in detail and the parameter selection of the circuit is given. Then the optimized layout of the circuit in a typical half-bridge SiC power module is proposed to reduce the stray parameters introduced by the coupled inductor effectively. The proposed method is verified by experiments under different conditions. Compared with a purely RC snubber balancing strategy, the capacitor can be significantly reduced. Since only passive components are required in the feedback loop, the proposed method demonstrates a reliable and straightforward approach to achieve equal voltage sharing of the series-connected devices. [ABSTRACT FROM AUTHOR]

DC transformers based on power electronics are key items of equipment for medium voltage dc (MVDC) distribution systems. Both high and low step-ratio dc–dc conversions are required to interface dc links at different voltages to form an integrated dc distribution system. The transformer-coupled resonant modular multilevel dc–dc converter (RMMC) is well-suited to high step-ratio connection between an MVDC network and a low voltage dc network but it is not suitable in low step-ratio conversion for linking two MVDC networks with similar but not identical voltages. This article presents a circuit evolution of the high step-ratio transformer-coupled RMMC into its low step-ratio transformer-less RMMC counterpart. These two RMMCs share the same structure and the same resonant process within the resonant submodule stack giving rise to the same operational advantages. Also, the circuit design experience can be readily transferred from one to the other. From these two base RMMC circuits, a family of RMMCs with further configurations is elaborated that provide a wider variety of connection options for MVDC distribution systems. In this circuit family, each high step-ratio transformer-coupled RMMC has a low step-ratio transformer-less RMMC counterpart and one can be transformed into the other via the circuit evolution process presented. The theoretical analysis for both high and low step-ratio RMMCs has been verified through full-scale simulations of medium voltage examples and further verified through down-scaled experiments on laboratory prototypes. [ABSTRACT FROM AUTHOR]

The modular multilevel matrix converter (M3C) is introduced and applied to a single-stage ac/dc solid-state transformer (SST), which uses only one concentrated medium-frequency transformer (MFT) for isolation. As a result, the transformer insulation design is simplified significantly and higher power density could be achieved. Meanwhile, a novel decoupling transformation based on two internal three-phase circulating systems is proposed to improve the previous method. Through this transformation, the unbalanced capacitor voltage components can be divided into four independent dimensions, which correspond to four kinds of capacitor voltage ripple frequency. And a dc-side vector model is then established to calculate the required circulating current reference for capacitor balancing. Besides, under the application of SST, the capacitor voltage ripple suppression strategy via injection of extra circulating current is proposed. The amplitude and frequency index is optimized to obtain the best effect. Therefore, the submodule capacitor volume can be reduced to achieve higher power density. Simulation and experimental results are also provided to verify the theoretical analysis. [ABSTRACT FROM AUTHOR]

The crosstalk voltage on the gate-source terminal of SiC power mosfets in a phase-leg circuit is composed of the gate–drain capacitor introduced voltage and the common-source inductor introduced voltage. The mathematical model of the crosstalk voltage indicates that to suppress two types of crosstalk voltage, there exists a contradictory requirement on the off-state gate loop impedance. This challenge reduces the effectiveness of conventional crosstalk elimination methods. As an improvement, a crosstalk voltage suppression circuit that synchronously eliminates the crosstalk voltage of gate–drain capacitance and the common-source inductance is proposed. In this article, instead of creating low-impedance gate loop in the off-state, a high-impedance gate loop is formatted to eliminate the voltage drop on the common-source inductance. Meanwhile, the potential false turn-on or the negative voltage spikes caused by gate–drain capacitance is eliminated by the precharge voltage in the gate-source capacitor. The required prestored charge is analyzed considering the nonlinear behavior of the junction capacitance of the SiC mosfets. The proposed gate driver is experimentally verified in different switching conditions. [ABSTRACT FROM AUTHOR]

In this paper, a coupled-inductor-based LCC resonant converter with the primary-parallel–secondary-series (PPSS) configuration is proposed to achieve output-voltage sharing ability for HV generator applications. The PPSS configuration of the LCC resonant converter with the voltage multipliers is introduced to achieve high output-voltage and increase the output-power level. However, the variations of the magnetizing inductance, leakage inductance, and winding capacitance of the HV transformer and voltage multiplier impact on the output-voltage sharing performance. Subsequently, the resonant inductors in the primary side of the conventional LCC resonant converters with the PPSS configuration are coupled to achieve the output-voltage sharing without any additional circuits and control efforts. Furthermore, an analytical equivalent circuit model considering the magnetizing inductor of the HV transformer is derived to analyze the output-voltage sharing ability. Moreover, the design method for the coupled inductors considering the output-voltage sharing performance affected by the leakage inductance of the coupled inductors is presented. Finally, the output-voltage sharing performance of the proposed coupled-inductor-based LCC resonant converter with the PPSS configuration is validated by the experimental results of a 50-V input, 5-kV output 100-W prototype. The prototype experimental results show that the unbalance voltage degree decreases from 67.7% to 8.5% with the utilization of the coupled inductor. [ABSTRACT FROM AUTHOR]

Linear ramp slope compensation (LRC) and quadratic slope compensation (QSC) are commonly implemented in peak-current-mode-controlled dc–dc converters in order to minimize subharmonic and chaotic oscillations. Both compensating schemes rely on the linearized state-space averaged model (LSSA) of the converter. The LSSA ignores the impact that switching actions have on the stability of converters. In order to include switching events, the nonlinear analysis method based on the Monodromy matrix was introduced to describe a complete-cycle stability. Analyses on analog-controlled dc–dc converters applying this method show that system stability is strongly dependent on the change of the derivative of the slope at the time of switching instant. However, in a mixed-signal-controlled system, the digitalization effect contributes differently to system stability. This paper shows a full complete-cycle stability analysis using this nonlinear analysis method, which is applied to a mixed-signal-controlled converter. Through this analysis, a generalized equation is derived that reveals for the first time the real boundary stability limits for LRC and QSC. Furthermore, this generalized equation allows the design of a new compensating scheme, which is able to increase system stability. The proposed scheme is called polynomial curve slope compensation (PCSC) and it is demonstrated that PCSC increases the stable margin by 30% compared to LRC and 20% to QSC. This outcome is proved experimentally by using an interleaved dc–dc converter that is built for this work. [ABSTRACT FROM AUTHOR]

This paper proposes a method to extract the junction temperature of high-voltage and high-power p-i-n diodes. It is investigated that the swept-out charge during reverse recovery current fall time is affected by junction temperature variation, which makes the swept-out charge a possible thermo-sensitive electrical parameter (TSEP). Thanks to the specific package of high-power IGBT modules with p-i-n diodes, the swept-out charge of a p-i-n diode can be measured by the induced voltage $v_{{eE}}$ on the parasitic inductor $L_{{eE}}$ between Kelvin and power emitter terminals. In typical inductive half-bridge circuit, the comprehensive analysis of commutation between the upper p-i-n diode and lower enabled IGBT discloses the monotonic relationship among the reverse recovery charge, reverse current fall time, and junction temperature. A double pulse chopper circuit is used to validate the theoretical analysis. The experimental results show that the dependence between diode junction temperature and charge during the reverse recovery current fall time is approximately linear. A three-dimensional lookup table is calibrated and can be used to estimate the p-i-n diode junction operating temperature. Finally, an experimental comparison of four TSEPs for p-i-n diode is presented to verify the feasibility of the implementation of proposed TSEP. [ABSTRACT FROM AUTHOR]

An advanced technique of energy compression with the third harmonic circulating current generation is presented in this paper to improve the surface treatment performance in the dielectric barrier discharge (DBD) systems. First, the relationship between the energy compression degree and contact angle is explored, which shows that the polymer surface wettability can be improved by the high energy compression degree in DBD. And then, an additional inductor is inserted into the resonant tank in the current-fed parallel-series resonant converter to generate the third harmonic current component, which can reduce the discharge-time-ratio and compress the energy transferred to the DBD loads. Furthermore, the method of rectifier-compensated fundamental plus third harmonic approximation (RCFTHA) is introduced to describe the current-fed parallel-series resonant converter by superposing two equivalent linear circuits operating at the fundamental and third harmonic frequencies, respectively. Consequently, the discharge-time-ratio optimization with the parallel-series resonant tank design is realized. Finally, the experimental results from a 350-W prototype substantiate the effectiveness of the energy compression with the third harmonic circulating current and the accuracy of RCFTHA. [ABSTRACT FROM AUTHOR]

Thermo-sensitive electrical parameter (TSEP) approaches are widely employed in the junction temperature extraction and prediction of power semiconductor devices. In this paper, the turn-off delay time is explored as an indicator of a TSEP to extract the junction temperature from high-power insulated gate bipolar transistor (IGBT) modules. The parasitic inductor LeE between the Kelvin and power emitter terminals of an IGBT module is utilized to extract the turn-off delay time. Furthermore, the monotonic dependence between the junction temperature and turn-off delay time is investigated. The beginning and end point of the turn-off delay time can be determined by monitoring the induced voltage veE across the inductor LeE. A dynamic switching characteristic test platform for high-power IGBT modules is used to experimentally verify the theoretical analysis. The experimental results show that the dependency between IGBT junction temperature and turn-off delay time is near linear. It is established that the turn-off delay time is a viable TSEP with good linearity, fixed sensitivity, and offers nondestruction on-line IGBT junction temperature extraction. [ABSTRACT FROM AUTHOR]

An advanced hybrid LLC series resonant converter with integrated flying-capacitor cell is proposed in this paper to enable the high step-down conversion in the high input voltage applications. The inherent flying-capacitor branch in the primary side can effectively halve the primary switch voltage stress compared with the half-bridge LLC converters. And the input voltage can be shared equally and automatically between the two series half-bridge modules without additional balance circuit or control strategies due to the built-in flying-capacitor cell. Moreover, the inherent soft switching performance during wide load range that exists in the LLC converters is still kept to reduce the switching losses, which ensures the high efficiency. Besides, the proposed converter can be extended to further decrease the switch voltage stress by employing stacked connection. Finally, a 500 ∼ 640 V-input 48 V-output 1 kW prototype is built and tested to verify the effectiveness of the proposed converter. The results prove that the proposed converter is an excellent candidate for the high input voltage and high step-down dc/dc conversion systems. [ABSTRACT FROM PUBLISHER]

Single-phase voltage source transformerless inverters have been developed for many years and have been successful commercial applications in the distributed photovoltaic (PV) grid-connected systems. Moreover, many advanced industrial topologies and recent innovations have been published in the last few years. The objective of this paper is to classify and review these recent contributions to establish the present state of the art and trends of the transformerless inverters. This can provide a comprehensive and insightful overview of this technology. First, the generation mechanism of leakage current is investigated to divide the transformerless inverters into asymmetrical inductor-based and symmetrical inductor-based groups. Then, the concepts of dc-based and ac-based decoupling networks are proposed to not only cover the published symmetrical inductor-based topologies but also offer an innovative strategy to derive advanced inverters. Furthermore, the transformation principle between the dc-based and ac-based topologies is explored to make a clear picture on the general law and framework for the recent advances and future trend in this area. Finally, a family of clamped highly efficient and reliable inverter concept transformerless inverters is derived and tested to offer some excellent candidates for next-generation high-efficiency and cost-effective PV grid-tie inverters. [ABSTRACT FROM PUBLISHER]

In this paper, a decoupled controlled triport dc/dc converter is derived by combining two bidirectional single-phase buck–boost converters and one isolated full-bridge converter for multiple input source applications. The power density is improved, and the circuit structure is simplified because the power devices are completely shared in the primary side. Furthermore, the pulsewidth modulation plus phase-shift control strategy is introduced to provide two control freedoms and achieve the decoupled voltage regulation within a certain operating range. The duty cycle of the bidirectional buck–boost converters is adopted to balance the voltage between the two primary input terminals, while their phase angle is applied to regulate the accurate secondary voltage. Furthermore, zero-voltage-switching soft-switching operation is provided for all of the primary power switches due to the inherent phase-shift control scheme. Moreover, the two filter inductors in the bidirectional buck–boost converters and the isolated transformer in the full-bridge topology are integrated and replaced by the winding-cross-coupled inductors to reduce the component numbers and simplify the magnetic structure. Finally, a 1-kW prototype is built to verify all theoretical considerations, and it is shown that the proposed topology is particularly advantageous in the distributed power generation system with multiple energy sources. [ABSTRACT FROM PUBLISHER]

In this paper, a soft-switching dc/dc converter with secondary-side phase-shift control strategy is proposed to improve the conversion efficiency and minimize the primary switch voltage stress in the high input voltage applications. Zero-voltage-switching performance is achieved for both the primary- and secondary-side power devices in a wide load range to reduce the switching losses due to the secondary-side phase-shift control scheme. Furthermore, compared with the conventional phase-shift control mechanism, the circulating current at the freewheeling stage is effectively suppressed as well to minimize the conduction losses. Moreover, the voltage stress of the primary switches is only half of the input voltage by employing the improved three-level structure, which makes the low-voltage rated power devices available to improve the circuit performance. In addition, the converter can work in the buck, balance, and boost modes to achieve a relatively wide input voltage range, which is an expected advantage for the communication power system to minimize the electrolytic capacitors with an acceptable hold-up time. The operation principle is analyzed and experimental results of a 1-kW 100-kHz prototype are provided to verify the effectiveness and the advantages of the proposed converter. [ABSTRACT FROM AUTHOR]

An advanced symmetrical voltage quadrupler rectifier (SVQR) is derived in this paper to serve as the secondary rectification topology, which helps to extend the converter voltage gain and reduce the output diode voltage stresses. The output voltage is four times of the conventional full-bridge voltage rectifier with the same transformer ratio, which benefits to reduce the turns ratio of the transformer and decrease the parasitic parameters. Also, low voltage-rated diodes with high switching performance can be applied to improve the efficiency. Meanwhile, all the diodes in SVQR have the same voltage and current stresses, which simplifies the thermal design. Furthermore, two output electrolytic capacitors are connected in series to share the high output voltage, and the voltage balance can be realized naturally without any additional voltage-sharing scheme. A clear picture is made in this paper to give a general framework and universal applications for the derived SVQRs for high step-up and high output voltage conversion systems. A dual boost converter is used as an example to demonstrate the clear advantages of the derived SVQRs. [ABSTRACT FROM AUTHOR]

First, the limitations of the conventional interleaved boost converters in high-step-up and high-output-voltage applications are addressed in this paper. Then, a general derivation law of the nonisolated converters from their isolated counterparts is proposed and studied to give a universal solution for high-performance topology deduction. By employing the direct energy transfer concept, a family of nonisolated high-step-up interleaved boost converters is originated to make the turns ratio of a built-in transformer as another design freedom for the voltage gain extension. The derived converters have the advantages of large voltage conversion ratio, low power switch voltage stress, small input current ripple, and zero-voltage-switching soft-switching performance. The steady-state operation of the derived converter is analyzed, and the circuit performance is summarized to explore its advantages in the high-step-up, high-output-voltage, and large-current conversion systems. Finally, a 1-kW prototype with 40-V input and 380-V output voltages is implemented and tested to show the effectiveness of the derived converters. One of the main contributions of this paper is that a clear picture is made on the universal derivation law to generate high-step-up and high-performance dc/dc converters. [ABSTRACT FROM PUBLISHER]

A high-efficiency fuel-cell power-generation system with an active-clamp flyback–forward converter is presented in this paper to boost a 12-V dc voltage into a 220-V 50-Hz ac voltage. The proposed system includes a high-efficiency high-step-up interleaved soft-switching flyback–forward converter and a full-bridge inverter. The front-end active-clamp flyback–forward converter has the advantages of zero-voltage-switching performance for all the primary switches, reverse-recovery-problem alleviation for the secondary output diodes, large voltage-conversion ratio, and small input-current ripple. Furthermore, there are two coupled inductors in the proposed converter. Each coupled inductor can work in the flyback mode when the corresponding main switch is in the turn-on state and in the forward mode when it is in the turnoff state, which takes full use of the magnetic core and improves the power density. In addition, the full-bridge inverter with an LC low-pass filter is adopted to provide low-total-harmonic-distortion ac voltage to the load. Therefore, high-efficiency and high-power-density conversion can be achieved in a wide input-voltage range by employing the proposed system. Finally, a 500-W prototype and another 1-kW converter are implemented and tested to verify the effectiveness of the proposed system. [ABSTRACT FROM AUTHOR]

A novel isolated zero-voltage-transition (ZVT) boost converter with coupled inductors is proposed in this paper to satisfy the high power, high step-up, and isolated requirements. In the proposed converter, the input-parallel configuration is adopted to share the large input current and to reduce the conduction losses, while the output-series structure is employed to double the output voltage gain. Consequently, a transformer with a low turns ratio can be applied, which makes the transformer design and optimize easily. Moreover, the active clamp circuits are employed to reduce the switch voltage stress and to recycle the energy stored in the leakage inductance. The ZVT is achieved during the whole switching transition for all the active switches, so the switching losses can be reduced greatly. Furthermore, the diode reverse-recovery problem is partly solved due to the leakage inductance. In addition, the magnetic integration technology is applied to improve the efficiency and to reduce the magnetic component size. Finally, a 48-V input 380-V output 1-kW prototype operating with 100-kHz switching frequency is built and tested to demonstrate the effectiveness of the proposed converter. [ABSTRACT FROM PUBLISHER]

In this paper, a voltage multiplier cell is inserted in the conventional boost converter operated in continuous conduction mode (CCM) to provide another design freedom for the voltage-gain extension. Thus, the voltage conversion ratio is enlarged and the narrow turn-OFF period is avoided in the high step-up applications. Furthermore, the voltage multiplier cell makes the voltage stress of all the power devices lower than the high output voltage. As a result, the low-voltage-rated power devices can be employed to reduce the conduction losses and to improve the power device reliability. Moreover, zero-voltage switching soft-switching operation is achieved for the power MOSFETs in the whole-switching transition. Zero-current switching turn-OFF condition is provided for the diodes. Therefore, the power device switching losses and the diode reverse-recovery losses are minimized greatly. In addition, the input current ripple is reduced due to the CCM operation compared with most of the published single-stage single-phase high step-up converters, which makes it more advantageous in the hybrid electric vehicles and the fuel-cell power conversion systems. Finally, the experimental results from a 500-W, 36–380-V prototype are provided to validate the effectiveness of the proposed converter. [ABSTRACT FROM PUBLISHER]