Milan M. Jovanovic

Present and future of distributed power systems

The current stage of development of distributed power systems is presented. Various DC-bus and AC-bus distributed power system architectures are discussed. System integration issues related to paralleling and cascading of DC/DC converters are explained. Benefits and challenges of distributed power systems in various applications are summarized.<<ETX>>

Comparison between CCM single-stage and two-stage boost PFC converters

In this paper, the analysis of the major-component ratings of the continuous current mode (CCM) single-stage power-factor-correction (PFC) and the CCM boost two-stage PFC converters is given. The results of the analysis are summarized in a number of design plots generated for different output power levels. Finally, merits and limitations of these two approaches are discussed.

Effect of switch capacitance on zero-voltage switching of resonant converters

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.<<ETX>>

Analysis of reactive power in resonant converters

A number of resonant power converters are analyzed to derive the reactive power and RMS current circulating through the transformer. The results of the analysis are used to define design guidelines that minimize the circulating energy in the converters and maximize their efficiencies and power densities. The analyzed converter topologies include the half-bridge zero current switching quasi-resonant converter (HB ZCS-QRC), the half-bridge zero-voltage-switched multiresonant converter (HB ZVS-MRC), the constant-frequency half-bridge zero-voltage-switched multiresonant converter (CF HB ZVS-MRC), the HB ZVS that uses the magnetizing inductance as a resonant element (HB ZVS-MRC (L/sub M/)), and the full-bridge series-parallel-resonant converter (FB SPRC). The results of the analysis show that the HB ZCS-QRC and the soft-switched HB ZVS-MRC (L/sub M/) circulate relatively small amounts of power. However, the circulating power in the HB ZVS-MRC, CF HB ZVS-MRC, and SPRC is found to be considerably larger. The analysis is used to generate sets of characteristics for each converter that can be used in their design optimization based on the minimization of the circulating power.<<ETX>>

Constant-frequency zero-voltage-switched multi-resonant converters: analysis, design, and experimental results

The multi-resonant-switch concept is modified to provide constant-frequency operation. Complete DC analysis and designs of the constant frequency forward and half-bridge multi-resonant converters are presented. Different implementations for the half-bridge topology are discussed. The performances of a 50 W forward converter and a 100 W, offline, half-bridge converter are also presented. A significant constant improvement of the performance of the constant-frequency zero-voltage-switched multi-resonant converter is expected from the development of MOSFETs with very low on-resistance (synchronous rectifiers).<<ETX>>

Comparison of half-bridge off-line, ZCS-QRC and ZVS-MRC

The performance of the half-bridge (HB) zero-current-switched (ZCS) quasi-resonant converter (QRC) and zero-voltage-switched (ZVS) multiresonant converter (MRC) is compared with respect to their efficiency, input voltage range, semiconductor stresses, power density, and reliability. The efficiency of the HB ZVS-MRC at a given nominal input is shown to be highly dependent on the range of the input voltage, and it suffers when the converter has to be designed to cover a wide range. However, this is not the case for the HB ZCS-QRC. Experimental versions of the HB ZCS-QRC and HB ZVS-MRC were designed for the input voltage range from 150 to 350 V and a maximum output power of 100 W, under the same constraints, to facilitate their comparison. >

Single-stage input-current-shaping technique with voltage-doubler-rectifier front end

In this paper, a new single-stage input-current-shaping (S/sup 2/ICS) technique that integrates the voltage-doubler-rectifier front end with a DC/DC output stage is introduced. Due to the voltage-doubler-rectifier front end, a reduction of line-current harmonics can be achieved with a higher conversion efficiency compared to the corresponding S/sup 2/ICS circuit with the conventional wide-range full-bridge rectifier. The proposed technique requires energy-storage capacitors with the same total capacitance and with half of the voltage rating as in the conventional S/sup 2/ICS counterpart, which reduces the size and cost of the power supply. The performance of the proposed technique is evaluated on a 450 W (5 V/90 A) experimental prototype circuit.

Effect of FET output capacitance on ZVS of resonant converters

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.

Comparison of half-bridge ZCS-QRC and ZVS-MRC for offline applications

Performance comparisons of the half-bridge (HB) half-wave zero-current-switched (ZCS) quasi-resonant converter (QRC) and the zero-voltage-switched (ZVS) multiresonant converter (MRC) are presented. The two converters were compared with respect to their efficiency, input voltage range, semiconductor-component stresses, power density, and reliability. A qualitative loss analysis reveals that the efficiency of the HB ZVS-MRC can be significantly lower at a nominal operating voltage when the input-voltage range is wide. The maximum efficiency of the HB ZCS-QRS is almost independent of the input-voltage range. These findings were verified experimentally by measuring efficiencies of 100 W offline HB ZCS-QRCs and ZVS-MRCs designed for various input-voltage ranges.<<ETX>>

Comparison of single-ended-parallel MRC and forward MRC

The forward zero voltage switched (ZVS) multiresonant power converter (MRC) and the class-E derived single ended parallel (SEP) MRC are compared on the basis of their relative current and voltage stresses, and efficiency for 50 W on-board power applications. The comparison is performed using SABER large-signal simulations with experimental verification of the results. It is found that the forward ZVS-MRC operates with lower current and voltage stresses under full load conditions, whereas the SEP-MRC operates with lower current and voltage stresses under light load conditions. As a result, the full-load efficiency of the forward ZVS-MRC is higher than that of the SEP-MRC, but the efficiency of the SEP-MRC is less dependent on load variations.<<ETX>>