Optimum trajectory switching control for series parallel resonant converter

The analysis of resonant converters including the capacitance of the switches is presented. New dc characteristics are obtained for the series, parallel, and series-parallel resonant converters (SPRC). The operating regions where the converters operate with zero-voltage switching (ZVS) are determined as a function of the switch capacitance. The more pronounced effect can be seen in the series resonant converter (SRC), while the parallel resonant converter (PRC) is the most insensitive. The results of the analysis have been verified on an experimental prototype.

This paper presents a new circuit topology known as series-parallel resonant converter (SPRC), which is a combination of both the series resonant converter (SRC) and the parallel resonant converter (PRC) topologies. This topology has several advantages when compared to the individual SRC and PRC. For example, the SPRC can operate under open load conditions, and it allows for zero-current switching operation. Using the steepest descent algorithm, the state-plane equations are numerically solved to obtain the performance characteristic curves. Based on these curves, a converter design procedure can be devised. A specific design example is given.

Owing to limited computational resources and the very large difference between electrical and thermal time constants, simulation for resonantly operated DC–DC converters using physical or ideal switching model is very time‐consuming or impossible. In this contribution, a novel thermal–electrical averaging model of resonantly operated DC–DC converters is proposed to reduce the computational burden and time consumption. The thermal–electrical model is based on extended describing function method. All required parameters for the thermal model can be obtained from the datasheets or on the website. The thermal–electrical models are applied in series–parallel resonant converters with LC‐type and C‐type output filters as examples, and verified by comparison with two standard simulation tools. The thermal–electrical modelling procedure proposed in this contribution can of course also be applied for other types of resonant converters, such as series resonant converter, parallel resonant converter and multi‐phase resonant converter.

A novel analytical methodology is proposed and applied to investigate the steady-state processes in voltage-fed parallel and series-parallel resonant DC-DC power converters with a capacitive output filter. In this methodology, the rectifier, output capacitor and load are replaced by an equivalent circuit which includes a capacitor and resistor connected in parallel. Excellent agreement was obtained when comparing the numerical values calculated by the proposed model to cycle-by-cycle SPICE simulation and to the numerical results of earlier studies.

A practical method for the steady-state design of parallel resonant DC/DC power converters is presented. The method uses a set of pre-derived equations from an LLCC-type series-parallel resonant converter (LLCC-SPRC). Although four tank elements are used in an LLCC-SPRC, only two ratios of these tank elements are needed during design. The values of the four tank elements can be found from the design results. In addition to designing an LLCC-SPRC, the prederived equations can also be used to design and analyze conventional LCC-type series-parallel (LCC-SPRC), LLC-type parallel (LLC-PRC), and LC-type parallel (LC-PRC) resonant power converters. In other words, four power converters can be designed by the same equations. A design procedure along with design examples is given. Experimental circuits are implemented and measured based on the design results to verify the validity of the derived equations and the design procedure.

The authors present an analysis of the series-parallel resonant power converter (SPRC) that includes the capacitance of the switches. New DC characteristics are obtained, and the regions where the converter operates with zero voltage switching are determined as a function of the switch capacitance. The analysis is also valid for series and parallel resonant converters. The analysis is verified experimentally on a 50 W, 1 MHz SPRC converter. >

This paper describes the design of a 20 kW (10kV, 2A) DC power supply using two stage control which consists of the silicon controlled rectifier (SCR) for input voltage control and the series-parallel resonant converter (SPRC) for output voltage control. In order to overcome the general constraint of SPRC, the restricted controllable load range with softswitching, the additional stage for adjusting input voltage by controlling the triggering angle of SCR is proposed and it facilitates the wide load range operation of SPRC with maintaining high-efficiency not only light-load but also rated operation. From the analysis of the controllable load range of SPRC with soft-switching, the control methodology of both switching-frequency of resonant inverter and triggering angle of SCR is explained. Based on the proposed control concept, a detailed design of a 20 kW power supply is provided including the PSpice simulation, the high-voltage transformer and the high-voltage rectifier. Finally, the experimental results which were carried out with various kinds of load condition verify the high-performance of proposed two stage control method from the view point of high-efficiency, wide controllable load range, and reliability.

A new contactless power converter topology for a seriously low coupling (less than 0.15) using low-cost commercialized ferrite core transformer with high efficiency and wide air-gap (23 mm) is presented in this paper. Among the typical resonant converter topologies for contactless power transferring systems, Series-Series Resonant Converter (SSRC) and Series-Parallel Resonant Converter (SPRC) are widely used in number of power electronic applications. Because of the simple strategy and superior response irrespective of coupling factor and load changes, SSRC topology is widely applied in contactless transformer applications. However, in seriously low coupling and wide air-gap applications, the switching frequency must be increased to several MHz range in order to operate the converter at the optimized operating region. Unless some high-cost, low resistance windings are selected, due to skin effect and proximity effect, the ac conduction loss will be dangerously high when the converter is operating at the high frequency range. To solve this problem, a modified and improved topology of series-series parallel resonant converter for wide-gap (23 mm) contactless power transfer applications with the coupling rate of 0.15 is proposed.

Every Renewable based energy source requires an additional buffer unit to deliver power to either a standalone system or a grid system. Most of the time unit buffer either provides constant voltage DC-power or AC-power. Higher efficiency in the conversion process can only be achieved if ongoing losses of the buffer system are low. Square sine control approach for Higher-Order Series-Parallel resonant DC-DC Converter is presented in the paper which provides excellent results in both highly and lightly loaded conditions. This control also provides stable bandwidth for input voltage source acceptance which is mostly to be considered as a PV-based source. The strategy also enhances the reliability of the converter by providing a stable and most delightful way of soft switching triggering so as to maintain the output voltage by un-affecting the switching cycle of the Solid-State Semi-conducting Device (SSSD). Selection for the components used in converter design was also studied with a susceptive case study. Further to this control for the entire converter unit is maintained to single variable control so as to reduce the complexity of the system and enhance efficiency. The simulated results of the programmable single variable square sine-wave control is presented for the higher-order resonant converter operating under variable input condition.

A full bridge high-frequency link series parallel resonant converter (SPRC) operating in discontinuous current mode is analyzed using the state-space approach. The equations are solved using the PROMATLAB software. Design curves for the converter gain and other component stresses are presented in normalized form. The converter has been optimized for peak component stresses, and the corresponding design curves obtained from PROMATLAB and SPICE3 simulation are presented. Using the optimal design curves, a 250-kHz experimental converter operating on a wide input voltage (1:2) has been built to verify the theoretical and SPICE3 simulation results.

Comparing with the conventional transformer without the air gap, a non-contact transformer with a large air gap between the long primary winding and the secondary winding has increased leakage inductance and reduced magnetizing inductance. For transferring the primary power to the secondary one, the high frequency series resonant converter has been widely used for the non-contact power supply system with the increased leakage inductance of a non-contact transformer due to the large air gap. However, the high frequency series resonant converter has the disadvantages of the low efficiency and the high voltage gain characteristics in the overall load range due to the large air gap and the high circulating magnetizing current. In this paper, the characteristics of the high efficiency and unit voltage gain are revealed in the proposed three-level series-parallel resonant converter. The results are verified on the simulation based on the theoretical analysis and the 5 kW experimental prototype.

This paper presents design procedures for UPS topologies based on series-parallel resonant converters. The UPS topologies considered have the following features: (i) unity power factor operation, (ii) isolation between the input, output and battery from each other using a single high frequency transformer, and (iii) zero voltage switching for the high frequency converters. Operation with both inductive and capacitive output filters are investigated and their impact on the stresses in the resonant circuit is pointed out. Experimental results are given to support the analysis and to validate the developed design procedures.

This paper presents the operating principle, analysis, design, simulation and experimental results for a high frequency (HF) transformer isolated AC-to-DC series-parallel resonant converter (SPRC) operating on the utility line, in discontinuous current mode (DCM). The equivalent models, the state space analysis of the SPRC in DCM are presented. PROMATLAB software is used to solve the equations and to obtain important design parameters. SPICE simulation and experimental results obtained from a 150 W prototype are presented to verify the analysis. High power factor operation (>0.99) with low harmonic distortion ( >

Because of their reduced switching losses, DC-to-DC resonant converters have been used extensively in the design of smaller size and lighter weight power supplies. The steady state and dynamic behaviors of both the conventional series and parallel resonant converters have been thoroughly analyzed and small-signal models around given nominal operating points have been obtained. These models have been used in the past to design controllers that attempted to keep the output voltage constant in the presence of input perturbations. However, these controllers did not take into account neither load nor components variations, and this could lead to instability in the face of component or load changes. Moreover, prediction of the frequency range for stability was done a posteriori, either experimentally or by a trial and error approach. In this paper we use /spl mu/-synthesis to design a robust controller for a series resonant converter. In addition to robust stability the design objectives include rejection of disturbances at the converter input while keeping the control input and the settling time within values compatible with a practical implementation. >

In this contribution the frequency-domain modeling techniques for resonant converters under optimized modulation are reviewed. As a general modeling technique, the standard AC fundamental harmonic approach is suitable for all resonant converter topologies. However, it becomes inaccurate if the current or voltage of the resonant tank is distorted from sinusoidal waveform. The extended AC fundamental harmonic approach provides a much higher modeling accuracy, but it lacks generality. In order to overcome these drawbacks a general, systematic time-domain modeling procedure with high modeling accuracy is introduced and demonstrated by a series-parallel resonant converter with LC output-filter under optimized modulation. Verification with experimental results is given.