Over the last few years, power factor correction has become an important field of research, due mainly to changing low frequency EMC standards. Our interest lies in AC/DC conversion from 230 V line voltage. Since July 1 1995 and for this type of line, European standard EN 61000-3-2 has replaced EN 60555-2, which entails great change for low and medium power converters.
Usually, the stage between the network and a DC/Dc converter is composed of an uncontrolled diode rectifier followed by a structure comprising at least an inductor and a capacitor. First, the capacitor sets the voltage variation in primary DC voltage and the inductor induces the input current waveform. However, these characteristics are not controlled by the typical rectifier and depend on network conditions or on load variations. This low-cost, robust system is analysed respecting EN 60555-2 and EN 61000-3-2 criteria. The relation between total harmonic distortion and the power factor is shown.
In order to improve the behavior of this stage, an active component has been added to the existing passive components when redesigning the chopper. This chopper is controlled in "Power Factor Correction" mode i.e. input current is triggered to a sinusoidal current from a loop. Depending on the choice of the chopper, one or several high frequency passive components are needed but a low frequency filter (capacitance on output) is still required.
The paper goes on to study the use of the boost chopper as a preregulator in association with another converter, and then the use of the insulated flyback converter to supply DC output voltage. For both, the different PFC control modes which enable a sinusoidal line current to be obtained are analysed and discussed for discontinuous and continuous conduction modes.
| Filename: | Unnamed file |
| Filesize: | 929.9 KB |
