This project focused on the design and implementation of a AC to DC Boost Converter with power factor correction, having an input voltage of 85 to 135 Vrms and a constant output of 220 volts. Having power factor correction means that less current flows through the circuit, due to not having reactive currents flowing in the circuit. Less current in the circuit means that components do not have to be oversized, thus saving on cost of components and also saving on your power bill.

Power factor correction is realized in Alternative Enery Solutions' design by allowing the UC3855 controller chip to modify the pulse width (PWM) of the gating signals for both the main transitor and Zero Voltage Transition (ZVT) transitor. By strategically changing the PWM, the UC3855 shapes the input current to match the phase of the voltage. The effects of the PWM can be seen in the diagram below. Notice here how the phase difference between the two rectified waveforms is zero.

A simple bridge rectifier is used to perform AC to DC conversion. The DC voltage from the rectifier is between 85 and 135 V. The rectified voltage is then boosted to 220 VDC through the used of a DC to DC booster circuit. The diagram [1] below shows the basic DC to DC circuit.

To increase the efficiency of the boost converter zero voltage transition (ZVT) soft switching techniques were used.

The diagram [2] below shows a basic AC to DC booster circuit.

The operation of this circuit identical to the operation of the DC to DC booster circuit. More details of this circuit can be found here.

The diagram [3] below shows the whole circuit, including the connections needed to use the UC3855A as the controller for the zero voltage switching and power factor correction. The resistor/capacitor values seen in this diagram are a sample for a AC to DC booster circuit which requires 85 - 270 Vrms input voltage, and supplies a 400 VDC load with a maximum of 250 W.

To see the approximate components used for 85-135 Vrms to 220 VDC Booster, the .pdf file with calculation can be downloaded here. These values are only approximate and have been changed slightly during the fine tuning process of the prototype circuit.

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[1] Diagram of the circuit taken from IEEE Transactions on Power Electronics, "A New ZVT-PWM DC-DC Converter" by H. Bodur and A.F. Bakan.

[2] Diagram from IEEE Transactions on Power Electronics, "A New ZVT-PWM DC-DC Converter" by H. Bodur and A.F. Bakan. with modifications by author.

[3] Diagram taken from Texas Intruments, "UC3855A/B High Performance Power Factor Preregulator" by J. Noon. Application notes available here.