High DC Output Voltage Research Articles

A novel cascading scheme to improve the performance of voltage multiplier circuits

The voltage multiplier (VM) circuit is a cascade arrangement designed from a series of rectifiers to obtain high DC output voltage. In this classical approach, the DC voltage which is getting gener...

English

This paper presents a high step-up dc-dc converter based on the Cockcroft-Walton (CW) voltage multiplier without using step-up transformer. The proposed converter is quite suitable for applying low-input dc voltage, to high output dc voltage dc generation systems. It provides continuous input current to load with low ripple voltage and current. Voltage stress on the all switching device, diodes, and capacitors are lower than the other type. Moreover, based on the 3-stage Cockcroft-Walton (CW) voltage multiplier, the proposed converter can provide a suitable dc source is solar cells, fuel cell and other type source for a 3-stage multilevel inverter. In this paper, the control strategy employs two independent frequencies, one operates at high frequency to minimize the size of the inductor and other one operates at relatively low frequency to the desired output voltage ripple. The simulation is carried over by the MATLAB-SIMULINK.

SiC Power Devices in a Soft Switching Converter, Including Aspects on Packaging

In many applications of power electronic converters efficiency and size are important figures of merit. Low losses in the power semiconductors and high frequency operation are important factors. The converters considered in this paper are off-line powered and in the power range of 50 – 150 kW with a high-voltage dc-output. The switching frequency is 20-40 kHz. With modern IGBTs an efficient operation (n> 95%) can be obtained when using soft-switching topologies. Fig 1(a) shows the schematic diagram of an SLR, series loaded resonant converter [1]. In Fig 1(b) typical waveforms of transformer current and voltage are depicted. In a recent paper, [2], frequency dependent IGBT losses are evaluated. Fig 2 shows the on-state voltage of an IGBT when conducting a sinusoidal current at different frequencies. At the higher frequency (30 kHz, Tr4) the increase of conduction losses is evident. Power switches made from SIC show excellent properties enabling; low conduction losses, high frequency operation and an ability to operate at high die temperatures [3]. Fig 3 (a) shows the on-state voltage of an unipolar SIC switch while Fig 3(b) shows the on-state voltage of a bipolar switch. Measurements have been performed up to 200 kHz without showing any high-frequency effects. High voltage SiC PiN diodes can replace several series connected Si diodes due to the higher critical field strength in SiC. This enables substantially reduced conduction losses in the output rectifier. In Fig 4 on-state voltages of 10 kV SiC and Si-diodes are shown, indicating a 50% reduction of losses.

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.

A High Efficiency Orthogonally Switching Passive Charge Pump Rectifier for Energy Harvesters

The design and analytical modeling of a high efficiency energy harvester comprising a passive voltage-boosting network (VBN) and a switching charge pump rectifier (CPR) is presented in this paper. To improve the power conversion efficiency (PCE), the VBN increases the voltage at the input of the CPR and provides control signals for switching. Unlike traditional Schottky and diode-connected MOS transistor rectifiers, the proposed orthogonally switching CPR (OS-CPR) comprises MOS transistors as voltage-controlled switches. Analytical models for the OS-CPR are developed and presented. Circuit-level optimization techniques are employed to reduce conduction and switching losses. Simulated in a 90 nm standard CMOS technology (IBM 9RF), a 5-stage 915 MHz OS-CPR achieves a dc voltage of 1.35 V and a PCE of 11.9% with a 1 MΩ load at -18.2 dBm available input power ( <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">P</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S,AV</sub> ). To show technology scalability of the design, the OS-CPR is also validated using AMS 0.18 μm high-voltage (HV) CMOS technology. When benchmarked with traditional rectifiers, the OS-CPR (under similar conditions) achieves a higher PCE and a higher output dc voltage. The OS-CPR is easily scalable to operate over multiple sub-GHz ISM frequency bands.

The High-Gain Boost Converter for Maximum Power Point Tracking in Photovoltaic System

The aim of this paper is to introduce a high-gain Boost circuit and to use the maximum power model to analyze the principles of maximum power point tracking (MPPT) in photovoltaic (PV) system .The principle is applied to the high-gain Boost circuit and control circuit, through a specific MPPT algorithm to change the duty cycle of Boost circuit realizes maximum power tracking and higher DC output voltage, the control circuit are formed by the CPLD and the AVR microcontroller, through which the control circuit to generate a varying duty cycle and 40KHz PWM pulse to control High-gain Boost circuit. Algorithm uses the incremental conductance method. Experiments show that maximum power point tracking effect is good.

An Efficient AC–DC Step-Up Converter for Low-Voltage Energy Harvesting

The conventional two-stage power converters with bridge rectifiers are inefficient and may not be practical for the low-voltage microgenerators. This paper presents an efficient ac-to-dc power converter that avoids the bridge rectification and directly converts the low AC input voltage to the required high dc output voltage at a higher efficiency. The proposed converter consists of a boost converter in parallel with a buck-boost converter, which are operated in the positive half cycle and negative half cycle, respectively. Detailed analysis of the converter is carried out to obtain relations between the power, circuit parameters, and duty cycle of the converter. Based on the analysis, control schemes are proposed to operate the converter. Design guidelines are presented for selecting the converter component and control parameters. A self-starting circuit is proposed for independent operation of the converter. Detailed loss calculation of the converter is carried out. Simulation and experimental results are presented to validate the proposed converter topology and control schemes.

A high-input-voltage backlight module driver for multi-lamp LCD panels

A half-bridge (HB) resonant inverter for driving a backlight module with multiple cold cathode fluorescent lamps (CCFLs) is proposed. Conventionally, a backlight module driving inverter is designed to operate with a low-input DC voltage. Therefore, a buck converter is required to step down the high-output DC voltage of a power factor correction (PFC) pre-regulator. The circuit cost is high and the conversion efficiency is low. In this letter, a high-input-voltage HB resonant inverter with only one transformer is used to drive multiple lamps. Analysis and design considerations are discussed in detail. Simulations and experimental results are close to the theoretical prediction. Copyright © 2010 John Wiley & Sons, Ltd.

Single-phase two-stage boost rectifiers with sinusoidal input current

Single-phase two-state boost rectifiers with sinusoidal input current are presented and a novel topology with two active power devices is proposed. These contain a capacitor for pumping action in DC circuit. This gives two-stage boost operation to obtain higher DC output voltage. The rectifier can be operated in the switch mode for pumping action and for forcing the input current to follow its sinusoidal reference independent of the working conditions. The results of the proposed rectifier are compared with those of the rectifier with a single active power device. The prototype tested is implemented to investigate the steady-state operation in the output voltage regulation. The experimental and the simulated results prove that the proposed rectifier has the expected performance.

Three-level zero-voltage switching pulse-width modulation DC–DC boost converter with active clamping

DC–DC step-up converters for high-output voltage applications typically demand high voltage devices, leading to high conduction and switching losses. This identified demand has motivated research on active clamping and multi-level topologies. On this context, this study presents the study of a novel DC–DC boost converter with three-level boost-type active clamping, zero-voltage switching (ZVS) soft-switching and constant frequency pulse-width modulation. As shown analytically and through experimental results, high efficiency and reduced voltage ratings for the power semiconductors are achieved, thus, making the topology suitable for converters requiring high-output DC voltage. Furthermore, a topological modification for achieving ZVS operation in all semiconductors and other types of switching cells for boost-type converters is introduced.

The Capacity Optimization for the Static Excitation Controller of the Dual-Stator-Winding Induction Generator Operating in a Wide Speed Range

The dual-stator-winding induction generator (DWIG) designed to achieve wide-speed-range operation with reduced capacity of the static power controller is presented. The DWIG consists of a standard squirrel-cage rotor and a stator with two separate windings wound for the same number of poles. This generator has a diode bridge rectifier load connected across to the power winding and a static excitation controller (SEC) to the control winding. Investigations into the reactive power released by the fixed excitation capacitor bank versus rotor speed under various loads represent that the minimal capacity of SEC can be achieved by an appropriate selection of excitation capacitor bank. With the help of instantaneous power theory, the control mechanism for the DWIG system working with a variable rotor speed is analyzed. Moreover, the system control strategy which is fit for the wide-speed-range operation using the stator flux orientation is consequently proposed. An 18-kW DWIG system with a 270-V high voltage DC output is developed. The simulation and experimental results illustrate a desirable performance, and the compact implementation of SEC is obtained.

Maximum power tracking of piezoelectric transformer HV converters under load variations

The problem of maximum power point tracking of high output dc voltage converters that apply piezoelectric transformers (PT) and voltage doublers was studied theoretically and experimentally. It was shown that the operating frequency of the PT, at which maximum power is reached, is a function of the load. Hence, under load variations, and to overcome parameter instability, there is a need for some frequency tracking mechanism that will help to lock the operating frequency to the optimum one. The proposed method to achieve frequency tracking is based on a phase locked loop (PLL). The PLL inputs are the phase of the input voltage driving the PT and the phase of the current flowing through one of the voltage doubler diodes. Theoretical analysis, verified by experiments, shows that when the phase shift of the diode current relative the phase of the input voltage is zero, the voltage gain of the system is at its maximum. By applying this approach, the system's operation can be made independent of input voltage, load variations, temperature (within a permitted range), and the spread and nonlinearity of the PT parameters, as well as their drift with time.

Generation of Pulsed Electric Fields for Processing Microbes

This paper first reviews viable microbe processing mechanism and then presents generation of pulsed electric fields for processing microbes. Microbe processing includes food sterilization, waste treatment, pollution control, and medical diagnostics and treatment. To generate pulsed electric fields for achieving sterilization, a generated high dc output voltage is chopped into pulsed waveforms, in which their pulse-width varies from tens of nanoseconds to hundreds of microseconds, period changes from 0.1 to 1 ms, and electric field intensity is from tens to hundreds of kV/cm. In this study, we propose wide pulses stacked with narrow pulses to prevent undesired air breakdown and reduce power consumption. Modified half-bridge series resonant converters are used to generate high dc voltages. They are operated at high frequency, in discontinuous conduction mode and with a PWM control; therefore, its weight and size can be reduced significantly and its efficiency can be correspondingly improved.

A unity power factor converter using half-bridge boost topology

A single-phase high-efficiency near-unity power-factor (PF) half-bridge boost converter circuit, which has been proposed earlier by other researchers, is presented with detailed analysis. This converter is capable of operating under variable PF. However, the focus of this paper is in achieving unity PF operation only. The efficiency of this circuit is high because there is only one series semiconductor on-state voltage drop at any instant. The existence of an imbalance in the voltages of the two DC-link capacitors, which was noted before, is confirmed here. The cause for the imbalance is analyzed using appropriate models, and a control method to eliminate it is discussed in detail. Analysis and design considerations for the power circuit using the fixed-band hysteresis current control (HCC) technique are provided. The analytical results are verified through simulation using switched and averaged circuit models of the scheme and also through experimental work. At 90-V AC input and 300-W 300-V output, the experimental prototype demonstrates an efficiency of 96.23% and a PF of 0.998. This converter, with its relatively high DC-output voltage, is well suited for the 110-V utility supply system. A circuit modification for universal input voltage range operation is also suggested.

High power factor correction circuits with space vector and hysteresis control methods

This paper presents a new topology of the three-phase ac to dc converter. Only three ac switches are required to perform the power factor correction. The series connection of the two output capacitors is adapted to employ the high dc output voltage. A space vector modulation strategy is used to control two of the three ac switches at any time, hence the switching numbers can be reduced. The addition of a hysteresis current control technique can simplify the hardware circuit and reduce the cost. Furthermore the input current can be made to follow any desired waveform. Finally, simulation and experimental results are presented to verify the characteristics of unity power factor and sinusoidal input current.