A MODIFIED SEPIC CONVERTER FOR HIGH-

POWER-FACTOR

RECTIFIER AND UNIVERSAL INPUT

VOLTAGE APPLICATIONS  BY : Y SAI KUMAR D RAKESH REDDY R RAJA SHEKAR REDDY Y SRINIVAS

INTRODCUTIONIn this project A high-power-factor rectifier suitable for universal line base on a

modified version of the single-ended primary inductance

converter (SEPIC) is presented. As generally know, there are many applications with high-

voltage sources fed, such as the burn-in test plant with energy

recycling, the DC-DC converter used in the car as the pre-stage

of the DC-AC converter, etc.

The new configuration also allows the

reduction of the losses associated to the diode

reverse recovery current, and soft commutation is

obtained with a simple regenerative snubber

circuit.

EXISTING SYSTEM LIMITATIONS

1. The size of passive components used is

higher.

2. For high power applications the power

factor correction is not efficient.

3. Soft switching is not performed.

4. Multistage system makes the system

losses higher

PROPOSED SYSTEM MERITS

1. the voltage ratio of the circuit is higher

2. there is no phase shifting circuit is

needed

3. can be used for high switching frequency

operation

BLOCK DIAGRAM

POWER FACTOR RECTIFICATION

•The power factor of an AC electric power system is defined as the ratio of the real power flowing to the load to the apparent power in the circuit 

•It dimensionless number between 0 and 1.

•In an electric power system, a load with a low power factor draws more current than a load with a high power factor for the same amount of useful power transferred.

•The higher currents increase the energy lost in the distribution system, and require larger wires and other equipment.

DRIVER CIRCUIT

DRIVER CIRCUIT COMPONENTS

OPTOCOUPLER

•OCTOCOUPLER is utilized mainly to isolate signals.

•Here it isolates micro-processor voltage to main circuit voltage.

BUFFER IC –CD4050

•The CD4050BC hex buffers are monolithic complementary MOS (CMOS) integrated circuits constructed with N- and P-channel enhancement mode transistors.

•. These devices are intended for use as hex buffers, CMOS to DTL/ TTL converters, or as CMOS current drivers, and at VDD = 5.0V, they can drive directly two DTL/TTL loads over the full operating temperature range.

TRANSISTOR

•In electronics, a transistor is a semiconductor device commonly used to amplify or switch electronic signals.

•. The transistor is the fundamental building block of modern electronic devices, and is used in radio, telephone, computer and other electronic systems.

SPECIFICATIONS

•The driver circuit is supplied using a step down transformer 230V/12V AC .In this project the driver circuit is mainly used to amplify the pulse output coming from the microcontroller circuit.

•The output from pin 1 and 2 of PIC16F877A is passed to the buffer IC CD4050 .

•The buffer IC acts as a NOT gate .the output from the buffer IC is passed to the two optocoupler respectively

•Thus the 5V pulse from the microcontroller circuit is amplified to 12V and sent to MOSFET switch.

MICRO-CONTROLLER

PIC16F877 A PIN OUT

SPECIFICATIONS

To perform the various operations and conversions required to switch, control and monitor the devices a processor is needed. The processor may be a microprocessor, micro controller or embedded controller.

In this project an micro controller has been preferred because we require to generate clock pulse. We have chose PIC16F877A in this project mainly for the following features.

FEATURES

FEATURES OF PIC16F877A High-Performance RISC CPU Operating speed: 20 MHz, 200 ns instruction

cycle Operating voltage: 4.0-5.5V Industrial temperature range (-40° to +85°C) 15 Interrupt Sources 35 single-word instructions All single-cycle instructions except for program

branches (two-cycle)

ADVANTAGES

The 16F877A is one of the most popular PIC microcontrollers and it's easy to see why - it comes in a 40 pin DIP pin out and it has many internal peripherals

This makes it easier to decide what external devices to attach without worrying too much if there enough pins to do the job.

One of the main advantages is that each pin is only shared between two or three functions so its easier to decide what the pin function (other devices have up to 5 functions for a pin)

DIS-ADVANTAGES

A disadvantage of the device is that it has no internal oscillator so you will need an external crystal of other clock source.

MOSFET SWITCH-IRFP250N

ADVANTAGE

1. Achieve high voltage ratio,2. Boost the voltage.3. Operate at current levels above 240 A

on the same output voltage, 4. Reduced size of passive components,5. No voltage clamp is needed.

APPLICATIONS

1. High-voltage sources fed ,2. Burn-in test plant,3. Energy recycling,4. In the car as the pre-stage of the

DC-AC converter

CONCLUSION

Hence SEPIC converter configuration is utilized in boosting up the voltage which is used in various applications……

QUERIES