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With the increase of switching frequency, dissipation of switching device became one of the most important factors which constrained the efficiency of DC-DC converter. A phase-shifted full-bridge circuit which based on the phase-shifted quasi-resonant converter was introduced in this paper. We developed a switching power supply prototype for 1000W. Some specific circuits, waveforms from the saber...
Aiming at the problems of the traditional sliding mode controllers for DC-DC switching Converters, a fixed frequency PWM sliding-mode controller for DC-DC switching Converters is proposed by employing the nonlinear differential geometry theory and impulse integral model in this paper. Design of this controller combines the nonlinear differential geometry theory with the variable structure controlling...
In this paper, a Pulse Width Modulation (PWM) technique for modular multilevel converter has been explored. The PWM technique is implemented using carrier based level shifted PWM strategy. It does not necessitate the calculation of duty cycles, and can be easily implemented in a DSP. With the proposed technique, harmonics in the phase voltage is shifted to twice the switching frequency. Thus, the...
Pulse Width Modulation technique (PWM) and Pulse Frequency Modulation technique (PFM) are commonly used techniques to generate pulses to control switches in DC-DC converters. However, these techniques generate various losses as well as output fluctuations when used at wide load ranges. The conduction losses and output voltage ripples are dominant in PWM at high loads, and switching losses are dominant...
Pulse width-modulated (PWM) inverters are used more and more to operate electrical machines and to interface renewable energy systems with the utility grid. However, there are abundant high-frequency harmonics in the output voltage of a PWM inverter, which increase the iron losses and result in derating of the machine or transformer connected to them. Predicting the iron losses caused by the PWM supply...
Photovoltaic applications require regulation by high performance dc-dc converters since the dc voltage generated is normally unregulated and depends heavily on load and ambient conditions. In this paper, a ZV-ZCS full-bridge phase-shift PWM dc-dc converter is being proposed for photovoltaic cell applications. The proposed converter operates at high switching frequency with high efficiency and large...
A 5-level PFC topology with fault-diagnostic and fault-tolerant capability is proposed and compared to known structures. It is derived from a 3-level non differential double-boost PFC including fly-cap cells. The series-connection of the two low-voltage switching-cells is decoupled by a single flying capacitor that provides a direct fault-tolerant capability and a post-failure operation increasing...
A new asymmetrical hybrid multilevel inverter topology is presented. The new topology improve the number of the output voltage level greatly through cascading two five-level H-bridge cells. A hybrid PWM strategy is proposed for the new topology that the switches of different cells works in different switching frequency to low switching losses. Lastly, an experimental 17-level asymmetrical inverter...
Voltage total harmonic distortion and related quadratic criteria are accepted as figures of merit of a multilevel PWM converter voltage quality. The dominating frequency domain voltage quality evaluation approach, in fact, is essentially numerical as it involves infinite double Fourier series expansion with Bessel function coefficients and requires high switching harmonics count. Suggested time domain...
The paper studies discontinuous space-vector modulation and switching sequence design in the case of grid-connected three-level neutral-point-clamped voltage-source converter operating with low switching frequency. Discontinuous pulse-width modulation (DPWM) methods of two-level modulation theory are used in three-level modulation and the effect of discontinuous switching sequence design on the switching...
A current-fed DC-DC converter with zero-current switching (ZCS) is presented in this paper. The front stage, which is a DC-DC buck converter, is used to regulate the output voltage by utilizing pulse-width modulation. The rear stage, which is a push-pull DC-DC converter by using the current-fed technique, is used to transfer energy from low voltage side to high voltage side for high voltage applications...
The paper is focused on the numerical calculation of total losses in each power device of 3L-ANPC (Active-NPC) and 3L-ASNPC (Active-Stacked-NPC) multilevel converters in a STATCOM application. Due to the symmetry of the structures the conduction and switching losses are calculated only for half of power devices. The modulation functions and the conduction/switching intervals are elaborated in order...
The presence of a spectrum spreading effect in a DC-to-DC converter operating in Pulse-Width Modulation (PWM) with a modulated switching frequency is analyzed. A step-down DC-to-DC converter prototype with a digital PWM ramp signal modulator is implemented in a standard CMOS 0.18-μm process. The step-down DC-to-DC converter has an 6-bit up/down binary counter to vary its switching frequency between...
In this paper, a simple feed-forward modulation technique for single-phase two-cell multilevel cascaded converters is presented. All the possible switching states of the power converter are taken into account applying a two dimensional control region. The proposed technique uses the actual values of the DC-Link capacitor voltages to obtain output phase voltages and currents with low harmonic distortion...
This paper presents an oversampled digital controller IC for low-power switch-mode power supplies (SMPS) that achieves fast response with a minimized addition of switching losses due to its control actions. To reduce the voltage deviation and improve converter response time, the controller samples the output voltage four times per switching cycle. A single voltage sample is processed by the conventional...
This paper presents an improved asymmetric space vector modulation (ASVM) for two level voltage source converters (VSCs) when the switching frequency is only 9 times of line frequency. By adding two pulses in each line cycle when the fundamental voltage crosses zero, the total harmonic distortion (THD) of output current can be reduced significantly with very limited penalty. The applications of improved...
For PWM DC-DC converters, keeping the output voltage steady is very important. When the input voltage has a step change, up impulse or down impulse voltage will occur in the output. Both the magnitude and the duration time of the over voltage are severely influencing to the whole system, which will destroy or disorder the circuit. Step-down converter is used as an example to investigate the input...
A fully digital controlled low-EMI switching converter combining RPPM (random pulse position modulation), our improved version of hybrid DPWM (digital pulse width modulator) and AEDPWM (area-efficient DPWM) schemes is proposed to achieve low-EMI (electromagnetic interference) with reduced area and power consumption. A FPGA-controlled prototype buck converter operating at 1 MHz switching frequency...
It has been shown that the resolution of DPWM can be dramatically increased by either constant on-time modulation or constant off-time modulation as compared to that for constant frequency modulation. However, the switching frequency increases dramatically for constant on/off-time modulation method under heavy/light load conditions. The objective of this paper is to propose a hybrid control technique...
This DC-DC buck converter is able to operate up to 120-MHz switching frequency with peak power efficiency of 87% for 75% duty cycle and 93% at 60 MHz. Key feature of this design is a new control method that replaces the conventional op-amp based scheme. The proposed circuit uses a current-mode control and a voltage-to-pulse converter for the PWM. The circuit, fabricated using a 0.18-mum CMOS technology,...
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