POWER FACTOR CORRECTION

IN AC-DC CONVERTERS WITH

BOOST TOPOLOGY

Presented BY

Under The Guidance of

INTRODUCTION Power factor plays a key role in delivering QUALITY Power to customers. Power Factor correction seeks to eliminate current spikes. This paper deals with concept of power factor correction with BOOST TOPOLOGY.

POWER FACTOR AND

NEED FOR CORRECTION

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The term power factor is borrowed from elementary AC circuit theory. When a sinusoidal AC power source feeds either an inductive or a capacitive load, the load current is also sinusoidal but lags or leads the input voltage by some angle x

In AC power circuit jargon, the magnitude of cos x is referred to as the power factor. It is desirable to keep the power factor as close to unity as possible, i.e., to keep the input line current sinusoidal and in phase with the sinusoidal input line voltage. The means to achieve this is referred to as power factor correction.

POWER FACTOR AND NEED FOR CORRECTION:

In the field of switching regulators circuit configuration which causes input line current to be non-sinusoidal or sinusoidal but out of phase which sinusoidal input voltage are to have harmonics of the line voltage results in a lowered power factor

Power Factor Correction In

Switching Power Supplies

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VACACI

C0 V0

Fig: Bridge Rectifier

with Filter Capacitor (C0)

Fig: Output Voltage with and without Filter Capacitor

(C0)

Fig: Input Line current with Filter Capacitor (C0)

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Power Factor Correction-Basic Circuit Details

V AC

ACI

L1

D1 C0 0R

V0 = VIN /(1-T ON /T)

RS

Q1

T

TON

VIN

Fig: Basic Circuit for Power Factor Correction 7

Fig: voltage waveform after the Bridge Rectifier with Power Factor Correction

Fig: Current waveform after the Bridge Rectifier with Power Factor Correction

VIN

V0=

─────── 1-TON / T

The output- input voltage relation of a Boost convertor is given by

Boost convertor “boosts” a low voltage to a higher voltage

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Q ON1 Q Q Q Q Q1 1 1 1 1ON ON ON ON ON

di/dt = V /L1

di/dt = V0- V

IN

IN /L1( )

Significant currents in boost converter at points progressively higher up on the half sinusoidal waveforms

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The final voltage which controls the Boost Regulators ON time must be a mix of the dc output voltage error and the input line current error voltage.

The optimum value of a inductor has to be selected.

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Simplified diagram of power

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power factor correction circuit with Boost Topology

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Conclusion:

The new concept of power factor correction with boost topology proposed in this paper corrects the power factor to 0.9lag.

The power taken by the converter from the ac supply side is 1000w and almost 1000w is obtained at the DC output side of the converter.

The performance of the above configuration has to be studied further by considering EMI.

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