Jurgen Petzoldt

A novel control principle of bi-directional DC-DC power conversion

This paper presents a novel control method for DC-DC power converters with bi-directional power flow and galvanic isolation. A high efficiency is achieved by using a minimal number of power electronic devices working in the soft switching mode. No reverse blocking switches are required. Different circuit variants can be derived from the proposed basic principle. Suitable industrial applications for the new principle of DC-DC conversion are UPS, photovoltaic applications, battery chargers, back-fire applications and auxiliary power supplies.

Modelling of asymmetrical pulse width modulation with frequency tracking control using phasor transformation for half-bridge series resonant induction cookers

A FPGA-based asymmetrical pulse width modulation (APWM) with frequency tracking control method is introduced for half-bridge series resonant induction cookers. Two control loops within FPGA are implemented. Phase-locked loop (PLL) is used as frequency tracking control to keep ZVS over wide range, APWM as power regulation. Large and small signal PSPICE compatible circuit model are obtained by phasor transformation. Dynamic models for half-bridge series resonant induction cooker are extracted from these circuits, and their characteristics are analysed. Finally models are verified and conclusions are given

Control system analysis and design of a resonant inverter with the variable frequency variable duty cycle scheme

This paper proposes a general modelling analysis method for a complete closed-loop control system for resonant inverters, such as LC series resonant inverter, LLC and LCC series-parallel resonant inverters, which use variable frequency variable duty cycle scheme. A half-bridge series resonant induction cooker with the variable frequency asymmetrical pulse width modulation (VFAPWM) control is used as a modelling example. Two control loops are implemented for this control system, by which the inverter is operated at zero-voltage-switching (ZVS) over wide load range. Phase-locked loop (PLL) is used as frequency tracking control, asymmetrical pulse width (APWM) as power regulation. The complete closed-loop dynamic model of a half bridge series resonant inverter system is solved. Then, the analysis and design of these control loops are discussed, and design considerations are provided. Finally, experiment results are given.

Determination of transient transistor capacitances of high voltage MOSFETs from dynamic measurements

This paper describes for the first time the determination of transient transistor capacitances of a high voltage transistor in a commutation circuit with application relevant conditions. Therefore, the gained characteristics reflect the transistor capacitances during switching. The dependency on operating conditions can be analyzed. New information on the drain current distribution between channel current and output capacitance current is gained from dynamic measurements. As a result, a recommendation is made for more accurate calculation of switching losses.

Real time calculation of the chip temperature of power modules in PWM inverters using a 16 bit microcontroller

Investigations of the transient chip temperature of IGBT and diode in power modules are presented in this paper. The calculation of chip temperature and power losses occurs on-line in a microcontroller. Advanced practical results achieved in a step down converter are shown at different load cycles and output frequencies with the same average load current. An analysis of results and errors is also shown.

Envelope Model of Frequency-Duty-Controlled LLC Converters

Tins paper presents envelope model of frequency- duty-controlled LLC converters. With this model, its DC and AC characteristics can be quickly simulated. Moreover, its transfer functions have been solved and analyzed. Thus, the compensator with duty cycle control, variable frequency control, or variable frequency variable duty cycle control can be easily designed using this model.

Envelope model for resonant converters and application in LLC converters

This paper presents the large and small signal envelope models for switching networks and rectifiers with variable frequency phase-shifted control for resonant converters. The model can be used to quickly perform DC and AC analysis with SPICE-compatible soft tools for a converter with frequency control, duty cycle control and variable frequency and variable control. Then the large signal envelope model of a LLC converter is given, the DC and AC sweep results with P SPICE are presented, by which its characteristic can be analyzed. Finally the verified results are given.

A new control scheme of the three-phase four-wire PWM converter under unbalanced and distorted input conditions

This paper presents circuit model and mathematical model of power for three-phase four-wire PWM converter under unbalanced and distorted input voltages. Based on the system model, a new positive-negative-zero sequence current reference control method is proposed to eliminate of harmonics of DC link voltage to alleviate the stress of the DC-link capacitor and to reduce the harmonics of input AC currents. The results show that the proposed control method has better performances than the conventional single positive sequence control under unbalanced and distorted input voltages.

A half-bridge series resonant inverter for induction cookers using a novel FPGA-based control strategy

Asymmetrical pulse width modulation (APWM) with frequency tracking control strategy is proposed for half bridge series resonant inverter for induction cookers, by which inverter is operated at zero-voltage-switching (ZVS) over wide load range. The FPGA-based full digital control system construction and operation are described. Steady state characteristics, such as normalized output power, turn-off current and average current through switches, are calculated. Some design considerations including selection of snubber capacitor, determination of dead time, ZVS boundary and presetting of phase-locked loop (PLL) are discussed. Finally, experiment results are given

Influence of device and circuit parameters on the switching losses of an ultra fast CoolMOS/SiC-diode device-set: simulation and measurement

The device-set consists of an ultra fast CoolMOS/sup TM/ and an ultra fast high voltage ThinQ!/sup TM/ SiC-Schottky diode nearly reaches the performance (losses, frequency, ruggedness) of pure SiC technology. So, new fields of application can be opened with future converter generations in high frequency power electronics. To optimize the circuits, the influence of parasitic parameters of the power semiconductor devices and circuit topologies on the switching behavior has to be analyzed exactly. Therefore, a suitable simulation tool was developed and verified by measurements in a typical application circuit. Results of simulations and measurement are presented in this paper.