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# Active Resistor Power Factor Correction

IP.com Disclosure Number: IPCOM000101352D
Original Publication Date: 1990-Aug-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 4 page(s) / 87K

IBM

## Related People

Wunderlich, RA: AUTHOR

## Abstract

Typical power supplies (AC/DC converters) that have large filter capacitors to meet PLD (Power Line Disturbance) conditions usually do not meet a PF (Power Factor) of 0.7 or greater. The usual method of obtaining good PF and meeting PLD conditions requires a complex circuit. Fig. 1-3 show a typical AC/DC converter with its input voltage and current signals. The power factor for this power supply was about 0.58.

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Active Resistor Power Factor Correction

Typical power supplies (AC/DC converters) that have large
filter capacitors to meet PLD (Power Line Disturbance) conditions
usually do not meet a PF (Power Factor) of 0.7 or greater.  The usual
method of obtaining good PF and meeting PLD conditions requires a
complex circuit.  Fig. 1-3 show a typical AC/DC converter with its
input voltage and current signals.  The power factor for this power

To obtain a power factor of 1, the input current in Fig. 3
should be sinusoidal and in phase with the input voltage in Fig. 2.
The closer the shape of the input current is to a sine wave (and in
phase), the better the power factor.

Fig. 4 shows the power supply of Fig. 1 with some added
circuitry to improve the power factor.  Some circuitry has been
eliminated to simplify the operation of the circuit. The idea behind
this circuit is to add a sinusoidal current that is in phase with the
input voltage only when there is no current required for charging the
filter capacitor C1 or supplying load current.  The voltage V1 is the
rectified input voltage Fig. 5.  D2 is a zener diode rated at 15
volts.  When V1 is greater than 15 volts, Q2 turns on and current
flows through R2.  The amount of current that flows through R2 is
determined by R2's value.  Also this current is used to increase the
power factor.  When a current spike occurs to charge C1 or supply
load current, the current is reflected to R3 through transformer T1.
When this occurs, Q1 turns on and turns off...