A single-stage high-power-factor electronic ballast withduty-ratio-controlled series resonant inverter

A single-stage high-power-factor electronic ballast is developed by making an integration of an active filter and a series resonant inverter. The function of power-factor correction is performed by adjusting the duty ratio of the inverter power switches with a simple control circuit. A prototype unit designed for a 36-W compact fluorescent lamp is built and tested to verify the predicted results     

Analysis of the self-oscillating series resonant inverter forelectronic ballasts

In this paper, we examine the self-oscillating series resonant inverter for electronic ballast applications from a system point of view. By considering the discharge lamp as a linear resistor in steady state, we derive a time-domain closed-form expression of the circuit state variables. Importantly, we observe that the self-oscillating series resonant inverter with lamp loads can be naturally modeled as a relay system. Based on this formulation, the self-oscillating frequencies of the inverter for variable lamp impedance conditions are found via the Tsypkin's locus. The stability of the self-oscillating frequencies is determined in a sampled-data system framework     

A high-power-factor DC-linked resonant inverter

A new approach of power-factor correction for the DC-linked high-frequency resonant inverters is proposed. The high-power-factor operation is achieved by altering the energy delivery process of the conventionally used topology. The load resonant circuit of the proposed topology draws a high-frequency pulse current directly from the AC source. This approach can be accomplished merely with an additional small capacitor as the energy buffer and a diode as the energy transfer switch. The design and experimental results for an implementation example are given to verify the theoretical analyses     

A resonant inverter for electronic ballast applications

Electronic ballasts must provide enough open circuit voltage to start the fluorescent lamp and current limiting while the lamp is running. Resonant inverters may be utilized in electronic ballasts because of their load-dependent characteristics. The three basic types of resonant inverters, the series-loaded, parallel-loaded, and the series-parallel-loaded, are compared using fundamental approximation techniques for their applicability in electronic ballasts operating from a low voltage source. A parallel-loaded resonant inverter operating slightly above its resonant frequency is selected because of the high voltage gains possible. Operation above the resonant frequency allows zero-voltage turn on of the semiconductor devices. Zero-voltage turn off can be achieved with the addition of lossless snubber capacitors. Experimental results from a lab prototype are used to verify the design procedure     

Analysis of transient and steady-state processes in the series (resonant)inverter

This paper deals with analysis of the transient and steady-state processes in series (resonant) inverters. Sets of differential and difference equations governing the transient and steady state processes are obtained and solved. The solution is found in closed analytical form. Theoretical and experimental results, both for transient and steady-state conditions, are compared and satisfactory agreement shown.     

A source voltage-clamped resonant link inverter for a PMSM using apredictive current control technique

A simple source voltage-clamped resonant link (SVCRL) inverter is proposed to clamp the DC-link voltage to the input source voltage and reduce the current rating of a resonant inductor. The current control of a permanent magnet synchronous motor (PMSM) employing a predictive current control technique (PCCT) for the SVCRL, inverter is also investigated to overcome the disadvantage of the current-regulated delta modulation (CRDM) control technique. By employing the PCCT based on the discrete model of a PMSM and estimation of back electromotive force (EMF), the minimized current ripple with a small number of switchings can be obtained. Finally, the comparative computer simulation and experimental results are given to show the usefulness of the proposed technique     

Design and analysis of an IC-less self-oscillating series resonant inverter for dimmable electronic ballasts

This paper presents a low-cost solution of converting the popularly adopted nondimmable electronic ballast circuit for fluorescent lamps with self-oscillating series resonant inverter into a dimmable one. The dimming function is achieved by increasing the switching frequency of the inverter from the natural frequency of the resonant tank, so that less energy is coupled to the lamp. Control of the switching frequency is based on deriving an adjustable dc current source from the resonant inductor in the resonant tank to control the operating point of the saturable transformers for driving the switches in the inverter. The overall implementation does not require any integrated circuit. A 17-W prototype has been built and studied. Theoretical predictions have been verified with experimental results. The lamp can be dimmed down to 10% of the full power.     

Auxiliary resonant commutated pole inverter using two internalvoltage-points of DC source

This paper presents a new auxiliary resonant commutated pole inverter that has series-connected batteries as the DC source. This inverter has two main switches and two auxiliary switches, and of all these devices achieve soft switching. The resonant operations are employed only during the commutating intervals; therefore, pulsewidth modulation (PWM) can be applied to the circuit. This circuit has the feature of using two internal voltage points of the DC source. Consequently, the circuit has the advantages of stability, simplicity in control, and high efficiency. The principle of the circuit operation and the experimental results are described in this paper     

Gate-assisted reverse and forward recovery of high-power GTOs inseries resonant DC-link inverters

The series resonant DC-link inverter is an attractive circuit topology for interfacing a DC current with a three-phase AC system. It uses gate turn-off thyristors (GTOs) as semiconductor switches. The conventional solution requires an additional series diode to perform the turn off process and to enable forward recovery of the GTO. This paper uses a single GTO along with a special gate drive to provide reverse and forward recovery. A new device testing circuit was designed to create the same electrical and thermal stresses as in a series resonant DC-link inverter. Experimental results using 2000 A GTOs at 26 kHz switching frequency demonstrate that the total device losses are reduced, while the hold-off time is slightly increased. The new single-device solution makes resonant switching attractive for very high-power applications     

Class DE current-source parallel resonant inverter

This paper introduces a Class DE current-source parallel resonant inverter, along with its design procedure and experimental results. This circuit offers several desirable features. First, the proposed circuit lacks harmonic components of input current over the voltage-source inverters. Second, the source pin of the MOSFET is directly connected to the ground, so that it is not necessary to use a complicated gate-drive circuit. Third, by maintaining zero-current switching, power loss by the parasitic inductor at turn-off decreases. The measured efficiency is over 90% at the output power of 3.5 W and the operating frequency of 0.5 MHz     

Analysis of tuning in resonant inverter

A model and analysis are presented for tuning of a resonant inverter. The model uses linearised phase-frequency characteristic of a tank load near the resonant frequency. To demonstrate the validation of the model, a low-power prototype was implemented using a CD4046 phase-locked loop chip in the tuning circuit     

具有方波输出谐振逆变桥的直流——直流变换器的分析和设计

本文从具有方波输出谐振逆变桥的直流—直流变换器的基本结构出发,通过对电路元件进行简化处理,详细分析了电路在不同工作时限的输出特性,获得了开关的最小关断时间,进而以上述结论为依据,提出了这种电路的一种简单的设计方案.     

A new power-factor-correction circuit for electronic ballasts withseries-load resonant inverter

This paper presents an efficient, small-sized and cost-effective power factor correction (PFC) scheme for high-frequency series-resonant electronic ballasts. The proposed scheme introduces additional small energy tanks processing partial power and thus can perform the function of input current shaping. Theoretical and experimental results prove that the electronic ballast incorporating with only few reactive components can achieve nearly unity power factor and very low harmonic distortion     

A series resonant converter for arc-striking applications

Initiation of a plasma conduction state requires a relatively large voltage to ionize the gas. A new version of the series resonant converter is proposed that uses the magnetizing inductance of the transformer for resonance. This converter is not suitable for most power supply applications, but the unique load characteristics associated with plasma loads make this type of converter well suited for arc striking, while allowing safe operation during the plasma state. A feature of the resonant converter is that the controller need not be complex, thus making it suitable for application in competitive industrial systems. Possible transformer configurations are investigated, which include an air core and a number of ferrite cored transformers. The series resonant converter with the best-suited transformer is verified experimentally in a tungsten inert gas welding application     

A contact-less system using a series resonant converter and a rectangular type core

Since the contact-less power transmission system accomplishes power transfer using magnetic coupling of the transformer without a mechanical contact, it has the advantages of electric isolation, safety, reliability, low maintenance and a long-product life. However, a contact-less transformer with a large air gap has a low coupling coefficient and high leakage inductance. This, in turn, results in poor power conversion efficiency. In this article, a contact-less power transmission system based on a rectangular type core and a series resonant converter is proposed to improve system efficiency and performance. The proposed system is designed with an air gap of 1 mm and 50 kHz switching frequency, but it is assumed that in a practical application, the air gap varies. It is verified by experimental results that the proposed contact-less power transmission system based on the rectangular type core and a series resonant converter can substantially reduce the circulating current and improve the system efficiency. Also, it is verified that even with an increased air gap, the proposed system maintains soft switching and avoids switching devices' current spikes while suppressing the increase of the circulating current caused by an air gap increase.     

A ZVS imbricated cell multilevel inverter with auxiliary resonant commutated poles

The imbricated-cell multilevel converter is well suited to high power applications. It allows the series connection of n switches with natural voltage sharing between these switches enabled through the connection of n-1 flying capacitors. This paper deals with the application of soft-switching on this topology; to date, only the hard-switching mode has been studied. The use of soft switching enables an increase of the switching frequency (resulting in the size reduction of the flying capacitors) without a decrease of the converter efficiency. Of the soft switching methods considered, the Auxiliary Resonant Commutated Pole (ARCP) technique was chosen due to the relative ease in which it can be incorporated into the converter topology. Furthermore, this technique offers numerous advantages: loss reduction, no added stress to the switches and compatibility with PWM control. The main properties of the ARCP multicell converter are the same as the hard-switched topology: an increase of the apparent output switching frequency and natural self-balancing of the flying-capacitor voltages. This paper presents the results of both simulations performed and measurements taken from an experimental set-up in order to study the viable system functioning. The introduction of soft-switching strongly complicates the theoretical study of the balancing mechanisms, however. As a result, the authors depend on simulations to validate the natural balancing effect during soft switching. Lastly, a general method of loss measurement is presented. Results show that the converter losses are reduced by at least 30%.     

A novel current initialization scheme for parallel resonant dc link inverter

In this paper a novel current initialization scheme is proposed for a parallel resonant dc link inverter. The method of current initialization is based on the state transition analysis of the system as a boundary-value problem. It is shown that, for a given load current, it is possible to force the dc link voltage to go to zero at a prescribed time by properly choosing the initial dc link current. This technique makes it possible to operate the resonant dc link inverter without any zero-crossing failure, which is the most important issue for satisfactory operation of such an inverter. The proposed current initialization technique is validated through digital computer simulation studies and practical implementation results.     

Demonstration of compact solid-state opening and closing switchutilizing GTOs in series

A compact opening and closing solid-state switch was designed, constructed, and demonstrated. The switch repetitively switches over 4 MW of peak power and yet is only 0.45 m by 0.12 m by 0.32 m and has a mass of 13 kg. The switch uses commercially available gate turn-off thyristors (GTOs), arranged in series to enable the collected devices to switch a voltage five times the rating of an individual device. The system uses commercially available components exclusively, yet takes advantage of state-of-the-art components. These include multilayer ceramic capacitors which are arrayed to produce a snubber capacitor, and small high-voltage isolated power transformers that protect each of the seven GTO stages from breakdown damage via their power supplies. Each stage is controlled via a fiber-optic link, and turn-on and turn-off times are adjustable for each of the seven stages. System dV/ dt exceeded 1 kV/μs and system di/dt exceeded 200 A/μs, for both turn-on and turn-off. The system was only limited in the amount of power it could switch by thermal considerations. A much higher power could be switched if there were advanced cooling. The cooling devices were quite modest, in that this was only a demonstration of the principle     

A series resonant AC-to-DC rectifier with high-frequency isolation

In this paper, a new series resonant AC-to-DC rectifier with high-frequency isolation is introduced. The proposed approach employs a PWM controlled AC controller, a series resonant tank and a high-frequency isolation transformer. With this approach, the single phase input AC is directly processed via the AC-to-AC converter eliminating the AC-to-DC rectification stage present in the conventional system. The output of the HF transformer is rectified and processed via a filtering stage to obtain a DC output. With the addition of an input filter, the input current is near sinusoidal at unity power factor. Simulation and experiment results are presented to verify the basic concept     

A simple control technique for series resonant converters

A control strategy for series resonant converters, based on the control of the state space trajectory, is proposed. Its simple implementation allows high frequency applications and requires only resonant current sensing. Quite linear and load independent control characteristics are obtained. Simulated and experimental results show good steady-state stability, fast dynamic response for wide reference step variations, and well-controlled converter start-up