Design And Development Of Unity Power Factor Ac To Dc Converter Employing Switched Mode Power Conversion

Abstract

Switched mode power supplies present a non-linear impedance to the mains, as a result of the input circuitry. The input circuitry consists of a full-wave recti er followed by storage capacitor. The capacitor maintains a voltage of approximately the peak voltage of the input sine wave. In this case, current is drawn from the input only when input voltage exceeds the capacitor peak voltage and this pulse of current must contain enough energy to sustain the load until next peak. So the current pulse must be 5 to 10 times the average current in magnitude. Power factor correction shapes the input current of o -line power supplies so as to maximize the real power available from mains. Ideally the electrical appliance should present a load that emulates a pure resistor so that reactive power drawn by it is zero. Various methods like, buck discontinuous conduction mode (DCM), boost continuous conduction mode (CCM), buck/boost (DCM) schemes are available for power factor correction (PFC) for high frequency pulse width modulated (PWM) non-isolated supply. PFC would be integrated into SMPS so as to comply with the IEC standard 61000-3-2. Work during this stage involved study and implementation of driver IC TLP250 and then the control IC SG3525 has been con gured and used along with the driver card and experimental results have been obtained. The open loop results for SMPS has been observed where the variation in control pin voltage a ects the inverter output voltage. The loop has been closed with feedback circuit and suitable results has been noted. Then the Active PFC circuit has been tested separately and nally integrated with SMPS. Attempts are made in this work to integrate the PFC circuit with SMPS and to see the overall power factor remains unity at various loading conditions of SMPS.