The precise measurement of the on-state voltage of power devices working in real operating conditions is the key for their characterization as well as health monitoring. This letter proposes a new on-state voltage measurement circuit featuring very high bandwidth and accuracy. An auxiliary circuitry allows to decouple the measurement system reference potential from the noisy device-under-test environment. The dc, ac, and dynamic performance have been validated from measurements on a prototype.

This paper proposes and analyzes a two-stage dc-dc isolated converter for electric vehicle charging applications, where high efficiency over a wide range of battery voltages is required. The proposed conversion circuit comprises a first two-output isolation stage with CLLC resonant structure and a second two-input buck regulator. The transformer of the first stage is designed such that its two output voltages correspond, ideally, to the minimum and maximum expected voltage to be supplied to the battery. Then, the second stage combines the voltages provided by the previous isolation stage to regulate the output voltage of the whole converter. The first stage is always operated at resonance, with the only function of providing isolation and fixed conversion ratios with minimum losses, whereas the second stage allows output voltage regulation over a wide range of battery voltages. Overall, it is shown that the solution features high conversion efficiency over a wide range of output voltages. This paper comprehensively describes the solution, including modeling, analyses, design considerations for the main circuit components (e.g., magnetics, switches), and modulation choices. Experimental results are reported considering a converter module prototype rated $10 \mathrm{kW}$ , input voltage $800 \mathrm{V}$ , and output range $250 \mathrm{V}$ to $500 \mathrm{V}$ , employing silicon-carbide and gallium-nitride semiconductors.

Isolated, zero-voltage-switching dc-dc converter topologies represent attractive solutions in the continuous run toward higher switching frequencies, allowing more compact power supplies. Among them, the asymmetrical half-bridge flyback converter represents an interesting option, featuring simple duty-cycle control at constant switching frequency, as opposed to the popular LLC converter. The majority of papers dealing with this topology consider an approximated voltage gain similar to that of an isolated buck converter operating in continuous conduction mode, i.e., proportional to the duty cycle and, practically, load independent. On the contrary, the true voltage gain is nonmonotonic at high duty-cycle values. Anytime the converter is designed for a resonant operation, as is advisable to eliminate any reverse recovery problem of the rectifier diode, the voltage gain not only increases, but also becomes a function of the switching frequency. This article investigates the converter's voltage gain in detail, deriving a theoretical framework capable of capturing its real behavior and dependencies. The proposed analytical model has been verified through simulations as well as experimental measurements taken on a 160-W prototype working at 400 kHz.

This article presents the analysis and design of a high-power-factor rectifier that integrates a discontinuous conduction mode operated Boost input cell with an asymmetrical half-bridge flyback converter (AHBFC). The particular connection of the dc–dc stage with the boost cell makes the dc link voltage decrease at light load, thus naturally limiting the switches’ voltage stress. A suitable design procedure is described that accounts for the resonant nature of the AHBFC, and allows to calculate all converter parameters to meet the design specifications and to achieve zero-voltage turn- on for the switches in any operating condition, considering both input voltage and load variations. The theoretical analysis is validated by experimental results taken on a $\mathbf {160\,}$ W rated prototype, working at the nominal switching frequency $\mathbf {f_{s}= 400\,}$ kHz, with a line voltage rms value ranging from $\mathbf {85\,}$ to $\mathbf {135\;{\mathrm V}}$ .

A new high step-up DC-DC converter topology combining a charge pump mechanism with a standard inductor-based Buck cell is here presented. Its main advantages are: minimum switch voltage stress, given by the input voltage, and reduced energy in the magnetic element compared to a conventional Boost converter designed for the same voltage gain. The proposed topology is derived through a modification of the basic voltage-doubler charge pump cell that, thanks to a coupled inductor, allows to make the flying capacitor voltages dependent on the switch duty-cycle. Both capacitor charging and discharging paths benefit from the inherent leakage inductance of the coupled inductor, with consequent soft diode turn off with no reverse recovery problems and ringing free operation. A proper design of the Buck inductance permits a quasi-square-wave operation, thus allowing a zero-voltage turn on of the switches. Suitable design criteria are proposed so as to achieve the desired converter operation mode, without need for any iterative process. Experimental results based on a 44 V to 400 V - 300 W prototype confirm the theoretical analysis and expectations, showing a quite flat efficiency curve that stays above 90% down to one tenth of the nominal power.

This paper proposes and analyzes a two-stage isolated dc-dc converter for electric vehicle charging applications, where high efficiency over a wide range of battery voltages is required. It employs a first pre-regulation stage and a second half-bridge LLC stage, integrated with the first. The second stage is always operated at resonance, ensuring high efficiency. The first pre-regulation stage is responsible for the desired input-to-output voltage conversion ratio and the zero-voltage switching operation of all the switches. This allows low conversion losses even with voltages that may vary over a wide range. The paper presents the conversion structure, the converter analysis, the design of the magnetic elements, and demonstrates the converter operation considering an experimental prototype interfacing a $\boldsymbol{750} \mathbf {V}$ dc-link with an output bus with nominal voltage range $\boldsymbol{250} \mathbf {V}$-$\boldsymbol{500} \mathbf {V}$. The implemented module is rated $\boldsymbol{5} \mathbf{kW}$ and achieves a peak efficiency of $\boldsymbol{98.0\%}$ at $\boldsymbol{3} \mathbf{kW}$ output power.