Peter Ide

Adaptive digital slope compensation for peak current mode control

Peak current mode control as well as digital control offers a number of benefits. Therefore it is an interesting approach to combine these two techniques in one control structure. Based on microcontrollers with on-chip comparators, this combination is realizable with very low effort. In order to eliminate the drawbacks of peak current mode control, a slope compensation has to be added. This paper presents such a slope compensation implemented on a microcontroller not using an analog ramp signal but instead pre-calculating the desired comparator switch-off threshold. In contrast to conventional analog control, adaptive algorithms can be used to maintain optimal slope compensation over a wide operating range. Problems that occur in practice due to reverse recovery current spike and computing time can be handled with simple measures. The effectiveness of the proposed digital slope compensation is verified by experimental results.

Enhanced control scheme for three-phase three-level rectifiers at partial load

A prominent boost-type three-level topology (VIENNA Rectifier I), which proved to represent a cost-effective and highly efficient solution for switched-mode rectifiers is inspected toward its operation at discontinuous conduction mode (DCM). This mode of operation occurs not only at high input voltage in conjunction with low load currents but even at medium loading in the vicinity of mains voltage zero crossings. When this circuit is operated in DCM, additional measures are required for improved behavior to avoid conflicts with requirements on total harmonic distortion and regulations as well as safe operation in terms of voltage balancing and overvoltage protection. A detailed analysis of DCM and associated states is performed enabling determination and location of error voltages. Basic rules for the location of error voltages can be found. This leads to a novel optimized modulation and control scheme, facilitating designs without additional inductance. Selected simulation and measurement results prove the enhanced modulation scheme.

Semi-Digital Interleaved PFC Control with Optimized Light Load Efficiency

A control structure for an interleaved power factor correction (PFC) rectifier with smart combination of analog and digital control parts is presented in this paper. Analog technique is employed to accomplish high control bandwidth while digital control is used for parts of lower dynamic demands. This results in low microcontroller costs though the system is kept flexible. Particularly, the control strategy can be adapted depending on the operation point. Since the light load performance is in recent focus of interest, appropriate algorithms to improve light load efficiency were implemented on a prototype system and are briefly described in this paper. The effectiveness of the proposed semi-digital control approach is verified by experimental results.

Scalable multi phase interleaved boundary mode PFC concept enabling energy- and cost efficient PSUs in the kW-range

A new concept of an interleaved multi phase power factor correction (PFC) rectifier which is operating at the boundary of discontinuous to continuous conduction mode (DCM/CCM boundary) is presented in this paper. DCM or DCM/CCM boundary mode operation of boost PFC topologies inherently avoids reverse recovery losses within the switching diodes which do occur at conventional CCM operation. This offers the possibility to employ cheaper Si- instead of high-performance SiC diodes (as required for efficient CCM operation) and, at the same time is even more energy efficient. Based on digital control this paper introduces a new extended concept of interleaving four or more boost phases in boundary mode operation yielding a modular PFC approach which is N times scalable with respect to the desired output power. Experimental results of a 1500W prototype PFC converter verify the proposed concept.

Fuel cell inverter system with integrated auxiliary supply

An innovative, flexible modular concept for a fuel cell inverter system with optimized overall efficiency for a domestic heater is presented and compared with conventional and fully bidirectional solutions. Three types of bidirectional insulated DC/DC converters are discussed. The design should take into account the asymmetrical flow of power from the fuel cell to the mains and back to the fuel cell for the supply of the auxiliary equipment. An integrated auxiliary power supply turned out to be best, which is fed during normal operation directly by the fuel cell, and, during start-up by the mains. A loss analysis for both operation modes has been carried out as support for the final design decision

Enhanced control scheme for three-phase/three-level rectifiers at partial load

A prominent boost-type three-level topology, which proved to represent a cost effective and highly efficient solution for switched mode rectifiers is inspected towards its operation at discontinuous conduction mode (DCM). This mode of operation occurs not only at high input voltage in conjunction with low load currents but even at medium loading in the vicinity of mains voltage zero crossings. And since the requirements on THD conflict with the actual behavior of the circuit when operated at DCM measures are needed for optimization. A detailed analysis of DCM and associated states is performed. Basic rules for the location of error voltages can be found. This leads to a novel measure to optimize the modulation and control scheme respectively, facilitating designs without additional inductance. Selected simulation and measurement results prove the enhanced modulation scheme.

Effects in magnetic components for switched mode applications in the MHz range

Increasing switching frequencies and faster switching transitions in switched mode applications extend the harmonic content of voltage and current, a magnetic component is stressed with far beyond its first resonance frequency. Several problems occur like oscillations due to parasitic reactive currents and radiation by leakage fields and they become a critical issue to a design. This contribution focuses on those effects and phenomena not being reported yet and shows solutions to the related problems.

Advanced modular communication concepts for data logging and conditioning in photovoltaic inverter systems

This paper describes an investigation in order to find an optimal solution for the communication of a PV installation. Most important is the quality of the collected data to be able to do detailed analysis. High investment costs make it necessary to get the PV installation controlled. In addition to that, because of variable power categories, different requirements in the data acquisition are also necessary. These requirements are overlapping various areas beginning from a LED in the PV inverter up to a data collection in a storage system. In addition to that, the price for a solution must be in a reasonable relationship to the size of the PV installation.