Jorma Kyyrä

Dynamics of a buck converter with a constant power load

The dynamic properties of the buck converter with a constant power load are studied in this paper. The line-to-output and control-to-output transfer functions are derived, for voltage mode control and current mode control, in continuous conduction mode and discontinuous conduction mode. A comparison with the case of a resistive load is made in each case.

High power factor rectifier based on buck converter operating in discontinuous capacitor voltage mode

The buck converter with LC input filter operating in discontinuous capacitor voltage mode has inherent power factor correction properties and continuous input current. The paper presents a detailed analysis of the converter operating in this mode, leading to design criteria. Finally, experimental results for a 48 V/sub dc//100 W converter are presented.

High power factor rectifier based on buck converter operating in discontinous capacitor voltage mode

The buck power converter with an LC input filter operating in the discontinuous capacitor voltage mode has inherent power factor correction properties and continuous input current. The paper presents a detailed analysis of the power converter operating in this mode, leading to design criteria. Finally, simulation and experimental results for a 48 VDC/100 W power converter are presented.

A new zero-voltage-transition PWM buck converter

In this paper a new zero-voltage-transition (ZVT) PWM buck converter is presented. An auxiliary circuit (consisting of one active switch and some reactive components) is added to the original buck converter. The auxiliary circuit is inactive during the ON and OFF intervals of the main switch in the normal buck converter. However, the transitions between the two states are controlled by the auxiliary circuit. Prior to turn-on, the voltage across the active switch in the buck converter is forced to zero. Thus, the turn-on losses of the active switch are practically eliminated. At turn-off the auxiliary circuit behaves like a nondissipative passive snubber, reducing the turn-off losses to a great extent. Zero-voltage-transition switching technique almost eliminates switching losses. The active switch operates under ZVT conditions, the passive switch (diode) has a controlled reverse recovery, and the switch in the auxiliary circuit operates under zero-current-switching (ZCS) conditions.

A step-down converter with low ripple input current for power factor correction

Step-down converters can be used to achieve power factor correction when a low output voltage is desired. The paper analyzes a nonisolated, two-inductor, step-down power converter and presents its application to power factor correction, when operating in the continuous conduction mode with average current mode control. The input current of the converter is continuous, since one of the inductors is on the line side. Moreover, for a proper coupling of the two inductors, the ripple of the input current can be significantly reduced. Thus, a PFC preregulator with low output voltage and low-ripple input current is obtained. The paper also presents experimental results for a 48 VDC output-voltage and 200 W output-power power factor correction preregulator, operating with 230 VRMS input voltage.

Input filter design for power factor correction converters operating in discontinuous conduction mode

Power factor correction (PFC) converters operating in discontinuous conduction mode (DCM) are very attractive for use in low-cost and low-power applications, due to simpler control when compared with continuous conduction mode (CCM) operation. Design of the EMI input filter for DCM operation has different constraints in certain aspects, when compared with the CCM case. This paper focuses on particularities of the input filter design in the DCM case.

Dynamic performance of buck converter with input voltage feedforward control

The effect of input voltage feedforward (IVFF) on the dynamical performance of a buck converter is investigated. The IVFF scheme is implemented making the pulse-width-modulation (PWM) ramp directly proportional to the input voltage. Ideally the IVFF control would make the internal loop gain constant, perfect attenuation of input noise and resistive input impedance with the phase of 180 deg. The transient response of the converter is, however, deteriorated due to limited duty ratio

USING INPUT INVARIANCE AS A METHOD TO FACILITATE SYSTEM DESIGN IN DPS APPLICATIONS

Distributed power supply (DPS) systems are extensively used to supply different electronic equipment and systems such as telecom switching systems. Continuous reduction of supply voltages of digita...

Genetic algorithm optimization of peak current mode controlled buck converter

This paper presents a genetic algorithm (GA), which optimizes the parameters of an analog controller for switched mode power converter (SMPC). A peak current mode controlled buck converter is used to test the optimization algorithm. The SMPCs response to line and load step changes is simulated with every combination of controller parameters emerging in GAs population. Each controller, i.e. each chromosome in the population, is assigned a cost depending on the simulated performance of the converter. The algorithm converges successfully. Although it relies on simulations, the measurements confirm that the controllers obtained by the GA result in a SMPC with stable and fast response with minimum over- and under-shoot. This method of controller optimization requires an accurate and reliable simulation model, but the transfer functions of the converter are not needed. Therefore, it can be most useful, if converters continuous transfer function model is unknown, or if traditional controller design techniques do not yield satisfactory results.

Modeling of multiport DC busses in power-electronic systems

This paper deals with dynamic modeling of multi-port DC busses, which are increasingly applied in various DC-power distribution systems, such as hybrid powertrains and DC microgrids. Parasitic impedances of long DC cabling together with distributed DC capacitors introduce a potential risk of small-signal instabilities in the DC bus, if resonance frequencies of the bus appear below (or around) switching frequencies of power-electronic converters. In order to predict the resonance behavior of the bus, a systematic approach for dynamic modeling of the DC bus in power-electronic systems is presented. The DC-bus model is validated by means of experiments. Furthermore, application of the model in small-signal analysis and time-domain simulations is illustrated.