Output DC Voltage Level Research Articles

Tunable AC/DC converter using graphene-germanium barristor based half-wave rectifier

Tunable DC voltage control circuit based on a half-wave rectifier was developed using a graphene–germanium barristor. The output DC voltage level could be modulated at 30–100% of the peak voltage by controlling the Schottky barrier height between graphene and germanium using a gate bias. Owing to the simple and low-temperature integration process, this device can be used for a variable DC power supply in monolithically integrated circuits or flexible devices.

A High-Power, Medium-Voltage, Series-Resonant Converter for DC Wind Turbines

A new modulation scheme is introduced for a single-phase series-resonant converter, which permits continuous regulation of power from nominal level to zero, in presence of variable input and output dc voltage levels. Rearranging the circuit to locate the resonant LC tank on the rectifier side of the high turns-ratio transformer combined with frequency control and phase-shifted inverter modulation keep transformer flux constant from nominal frequency down to dc, always in subresonant continuous or discontinuous conduction mode. This overcomes the principal deficit of series-resonant converters, and the resulting compact and efficient transformer, and soft-commutated inverter, present particular advantages in high-power, high-voltage applications, such as dc offshore wind turbines. With transformer excitation frequency in hundreds of Hz range, line-frequency diodes can be employed in the high-voltage rectifier valve. Circuit operation and conduction modes, governing equations, and sample waveforms are presented, together with experiments from a scaled demonstrator.

Analysis of SMPS in Clinical Medical Equipment

There exists low voltage in circuit of domestic and imported medical equipment and it is what we call power supply. In the past, equipment mainly uses transformer to step down the voltage of power supply. With the progress of science and technology, the technique is gradually replaced by SMPW (switch mode power supply) which is extensively applied to various types of medical equipment due to the high efficiency and wide voltage range. The mains power supply is rectified and filtered into a DC high voltage and then use the switch circuit and energy storage elements to convert them into a variety of required DC voltage output, output DC voltage level can be adjusted by changing the off time (namely Mark-Space Ratio) of switching circuit.

Stability analysis of a high-step-Up DC grid-connected two-stage boost DC-DC converter

High conversion ratio switching converters are used whenever there is a need to step-up dc source voltage level to a much higher output dc voltage level such as in photovoltaic systems, telecommunications and in some medical applications. A simple solution for achieving this high conversion ratio is by cascading different stages of dc-dc boost converters. The individual converters in such a cascaded system are usually designed separately applying classical design criteria. However these criteria may not be applicable for the complete cascaded system . This paper first presents a glimpse on the bifurcation behavior that a cascade connection of two boost converters can exhibit. It is shown that the desired periodic orbit can undergo period doubling leading to subharmonic oscillations and chaotic regimes. Then, in order to simplify the analysis the second stage is considered as constant current sink and design-oriented analysis is carried out to obtain stability boundaries in the parameter space by taking into account slope interactions between the state variables in the two-different stages.

3boost: A High-Power Three-Phase Step-Up Full-Bridge Converter for Automotive Applications

This paper describes a simple dc-dc step-up converter topology for switch-mode dc power supplies. The proposed configuration is well suited for high-power applications with battery supply. In the automotive framework, the push-pull architecture is the most widespread. However, as power increases, the use of a full-bridge architecture is mandatory. This paper presents a full-bridge architecture where the traditional single-phase transformer is replaced by a three-phase transformer. A prototype was realized and tested for the power supply of automotive devices. In this environment, one of the most important requirements is the ability to provide a burst of power during short-duration events, together with high-efficiency and high-quality output voltage. The latter constraints can be achieved by only using closed-loop switch-mode dc-dc converters at high switching frequency, thus reducing converter efficiency and creating electromagnetic-compatibility (EMC) problems. In this paper, the aforementioned issues were tackled relying on an open-loop topology. Open-loop converters are feasible if the output resistance of the converter is as low as possible, and a possible solution is the minimization of power losses. The solution is the use of a three-phase transformer with a delta-wye connection within a full-bridge converter topology. The configuration will be referred to as 3boost power supply. The three-phase transformer replaces the common single-phase transformer, and it is driven by a three-phase full-bridge inverter operating in six-step modulation. At secondary, a three-phase full wave diode rectifier is used to obtain the output dc voltage level. Therefore, a unitary transformer utilization factor is achieved. A simple theoretical comparison between the three types of converters-push-pull, conventional full bridge, and 3boost is shown. A low-power version of the converter was realized. Experiments confirm that this topology allows to achieve a high efficiency, a lower ripple factor, and a good EMC behavior.

The Impact of Gate-Oxide Breakdown on Common-Source Amplifiers With Diode-Connected Active Load in Low-Voltage CMOS Processes

The influence of gate-oxide reliability on common-source amplifiers with diode-connected active load is investigated with the nonstacked and stacked structures under analog application in a 130-nm low-voltage CMOS process. The test conditions of this work include the dc stress, ac stress with dc offset, and large-signal transition stress under different frequencies and signals. After overstresses, the small-signal parameters, such as small-signal gain, unity-gain frequency, phase margin, and output dc voltage levels, are measured to verify the impact of gate-oxide reliability on circuit performances of the common-source amplifiers with diode-connected active load. The small-signal parameters of the common-source amplifier with the nonstacked diode-connected active-load structure are strongly degraded than that with the stacked diode-connected active-load structure due to a gate-oxide breakdown under analog and digital applications. The common-source amplifiers with diode-connected active load are not functionally operational under digital application due to the gate-oxide breakdown. The impact of soft and hard gate-oxide breakdowns on the common-source amplifiers with nonstacked and stacked diode-connected active-load structures has been analyzed and discussed. The hard breakdown has more serious impact on the common-source amplifiers with diode-connected active load.