Comparison of single-phase matrix converter and H-bridge converter for radio frequency induction heating

This paper compares the newly developed single-phase matrix converter and the more conventional H- bridge converter for radio frequency induction heating. Both the converters exhibit unity power factor, very low total harmonic distortion at the utility supply interface, good controllability under soft switching condition for a wide range of power, and high efficiencies, whilst still having simple structures. A novel switching control pattern has been proposed for the matrix converter in order to maintain the comparable performance to the H-bridge converter. Simulation and experimental results for both converters are presented. Comparisons between two converters have confirmed the excellent performance of the proposed matrix converter

Battery Charge Applications Based on Wide Output Voltage Range

In this study, high efficiency design procedure of a phase shifted full bridge (PSFB) converter is presented for on-board electrical vehicle (EV) battery charger. Presented design methodology used lithium-ion battery cells because of their high voltage and current rates compared to a lead-acid battery cells. In this case, PSFB converter can be regulated wide range output voltage with while its soft switching operation is maintained. The basic operation principles of PSFB converter is defined and its soft switching operation requirements are given. To evaluate the performance of the converter over wide output voltage range, zero voltage switching (ZVS) operation of converter is discussed based on dead time requirement. To improve efficiency, the snubber inductance effects on soft switching over wide output voltage range are evaluated. Finally, operation of the PSFB converter is validated experimentally with a prototype which has 42-54 V/15 A output range at 200 kHz switching frequency

A comparative study of electric power distribution systems for spacecraft

The electric power distribution systems for spacecraft are compared concentrating on two interrelated issues: the choice between dc and high frequency ac, and the converter/inverter topology to be used at the power source. The relative merits of dc and ac distribution are discussed. Specific converter and inverter topologies are identified and analyzed in detail for the purpose of detailed comparison. Finally, specific topologies are recommended for use in dc and ac systems

Linearized large signal modeling, analysis, and control design of phase-controlled series-parallel resonant converters using state feedback

This paper proposes a linearized large signal state-space model for the fixed-frequency phase-controlled series-parallel resonant converter. The proposed model utilizes state feedback of the output filter inductor current to perform linearization. The model combines multiple-frequency and average state-space modeling techniques to generate an aggregate model with dc state variables that are relatively easier to control and slower than the fast resonant tank dynamics. The main objective of the linearized model is to provide a linear representation of the converter behavior under large signal variation which is suitable for faster simulation and large signal estimation/calculation of the converter state variables. The model also provides insight into converter dynamics as well as a simplified reduced order transfer function for PI closed-loop design. Experimental and simulation results from a detailed switched converter model are compared with the proposed state-space model output to verify its accuracy and robustness

Input current shaped ac-to-dc converters

Input current shaping techniques for ac-to-dc converters were investigated. Input frequencies much higher than normal, up to 20 kHz were emphasized. Several methods of shaping the input current waveform in ac-to-dc converters were reviewed. The simplest method is the LC filter following the rectifier. The next simplest method is the resistor emulation approach in which the inductor size is determined by the converter switching frequency and not by the line input frequency. Other methods require complicated switch drive algorithms to construct the input current waveshape. For a high-frequency line input, on the order of 20 kHz, the simple LC cannot be discarded so peremptorily, since the inductor size can be compared with that for the resistor emulation method. In fact, since a dc regulator will normally be required after the filter anyway, the total component count is almost the same as for the resistor emulation method, in which the filter is effectively incorporated into the regulator

State-variable modelling of CLL resonant converters

The paper presents the derivation and application of state-variable models to high-order topologies of resonant converters. In particular, a 3rd order CLL resonant circuit is considered with bridge rectification and both a capacitive output filter (voltage output), and an LC output filter (current output). The state-variable model accuracy is verified against component-based simulation packages (Spice) and practical measurements, and it is shown that the resulting models facilitate rapid analysis compared to their integration-based counterparts (Spice, Saber), without the loss of accuracy normally associated with fundamental mode approximation (FMA) techniques. Moreover, unlike FMA, the models correctly predict the resonant peaks associated with harmonic excitation of the tank resonance. Subsequently, it is shown that excitation of the resonant tank by odd harmonics of the input voltage can be utilised to provide overcurrent protection in the event of an output short-circuit. Further, through judicious control of operating frequency, it is shown that 'inductive' zero voltage switching (ZVS) can still be obtained, facilitating reductions in gate-drive switching losses, thereby improving efficiency and thermal management of the supply under fault conditions. Although the results are ultimately generic to other converter counterparts, measured results from two prototype 36 V input, 11-14.4V output, 3rd - order CLL converters are included to practically demonstrate the attributes of the proposed analysis and control schemes

Study of switching transients in high frequency converters

As the semiconductor technologies progress rapidly, the power densities and switching frequencies of many power devices are improved. With the existing technology, high frequency power systems become possible. Use of such a system is advantageous in many aspects. A high frequency ac source is used as the direct input to an ac/ac pulse-density-modulation (PDM) converter. This converter is a new concept which employs zero voltage switching techniques. However, the development of this converter is still in its infancy stage. There are problems associated with this converter such as a high on-voltage drop, switching transients, and zero-crossing detecting. Considering these problems, the switching speed and power handling capabilities of the MOS-Controlled Thyristor (MCT) makes the device the most promising candidate for this application. A complete insight of component considerations for building an ac/ac PDM converter for a high frequency power system is addressed. A power device review is first presented. The ac/ac PDM converter requires switches that can conduct bi-directional current and block bi-directional voltage. These bi-directional switches can be constructed using existing power devices. Different bi-directional switches for the converter are investigated. Detailed experimental studies of the characteristics of the MCT under hard switching and zero-voltage switching are also presented. One disadvantage of an ac/ac converter is that turn-on and turn-off of the switches has to be completed instantaneously when the ac source is at zero voltage. Otherwise shoot-through current or voltage spikes can occur which can be hazardous to the devices. In order for the devices to switch softly in the safe operating area even under non-ideal cases, a unique snubber circuit is used in each bi-directional switch. Detailed theory and experimental results for circuits using these snubbers are presented. A current regulated ac/ac PDM converter built using MCT's and IGBT's is evaluated

Soft-Switching DC-DC Converters

Power electronics converters are implemented with switching devices that turn on and off while power is being converted from one form to another. They operate with high switching frequencies to reduce the size of the converters\u27 inductors, transformers and capacitors. Such high switching frequency operation, however, increases the amount of power that is lost due to switching losses and thus reduces power converter efficiency. Switching losses are caused by the overlap of switch voltage and switch current during a switching transition. If, however, either the voltage across or the current flowing through a switch is zero during a switching transition, then there is no overlap of switch voltage and switch current so in theory, there are no switching losses. Techniques that ensure that this happens are referred to as soft-switching techniques in the power electronics literature and there are two types: zero-voltage switching (ZVS) and zero-current switching (ZCS). For pulse-width modulated (PWM) Dc-Dc converters, both ZVS and ZCS are typically implemented with auxiliary circuits that help the main power switches operate with soft-switching. Although these auxiliary circuits do help improve the efficiency of the converters, they increase their cost. There is, therefore, motivation to try to make these auxiliary circuits as simple and as inexpensive as possible. Three new soft-switching Dc-Dc PWM converters are proposed in this thesis. For each converter, a very simple auxiliary circuit that consists of only a single active switching device and a few passive components is used to reduce the switching losses in the main power switches. The outstanding feature of each converter is the simplicity of its auxiliary circuit, which unlike most other previously proposed converters of similar type, avoids the use of multiple active auxiliary switches. In this thesis, the operation of each proposed converter is explained, analyzed, and the results of the analysis are used to develop a design procedure to select key component values. This design procedure is demonstrated with an example that was used in the implementation of an experimental prototype. The feasibility of each proposed converter is confirmed with experimental result obtained from a prototype converter

Development of Efficient Soft Switching Synchronous Buck Converter Topologies for Low Voltage High Current Applications

Switched mode power supplies (SMPS) have emerged as the popular candidate in all the power processing applications. The demand is soaring to design high power density converters. For reducing the size, weight, it is imperative to channelize the power at high switching frequency. High switching frequency converters insist upon soft switching techniques to curtail the switching losses. Several soft switching topologies have been evolved in the recent years. Nowadays, the soft switching converters are vastly applied modules and the demand is increasing for high power density and high efficiency modules by minimizing the conduction and switching losses. These modules are generally observed in many applications such as laptops, desktop processors for the enhancement of the battery life time. Apart from these applications, solar and spacecraft applications demand is increasing progressively for stressless and more efficient modules for maximizing the storage capacity which inturn enhances the power density that improves the battery life to supply in the uneven times. Modern trends in the consumer electronic market focus increases in the demand of lower voltage supplies. Conduction losses are significantly reduced by synchronous rectifiers i.e., MOSFET’s are essentially used in many of the low voltage power supplies. Active and passive auxiliary circuits are used in tandem with synchronous rectifier to diminish the crucial loss i.e., switching loss and also it minimizes the voltage and current stresses of the semiconductor devices. The rapid progress in the technology and emerging portable applications poses serious challenges to power supply design engineers for an efficient power converter design at high power density. The primary aim is to design and develop high efficiency, high power density topologies like: buck, synchronous buck and multiphase buck converters with the integration of soft switching techniques to minimize conduction and switching losses sustaining the voltage and current stresses within the tolerable range. In this work, two ZVT-ZCT PWM synchronous buck converters are introduced, one with active auxiliary circuit and the other one with passive auxiliary circuit. The operating principle and comprehensive steady state analysis of the ZVT-ZCT PWM synchronous buck converters are presented. The converters are designed to have high efficiency and low voltage that is suitable for high power density application. The semiconductor devices used in the topologies in addition to the main switch operate with soft switching conditions. The viii Abstract topologies proposed render a large overall efficiency in contrast to the contemporary topologies. In addition the circuit’s size is less, reliable and have high performance-cost ratio. The new generation microprocessor demands the features such as low voltage, high current, high power density and high efficiency etc., in the design of power supplies. The supply voltage for the future generation microprocessors must be low, in order to decrease the power consumption. The voltage levels are dripping to a level even less than 0.7V, and the power consumption increases as there is an increase in the current requirement for the processor. In order to meet the demands of the new generation microprocessor power supply, a soft switching multiphase PWM synchronous buck converter is proposed. The losses in the proposed topology due to increasing components are pared down by the proposed soft switching technique. The proposed converters in this research work are precisely described by the mathematical modelling and their operational modes. The practicality of the proposed converters for different applications is authenticated by their simulation and experimental results