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Simulating Power Factor Correction Switching Converters Using Analog Models

IP.com Disclosure Number: IPCOM000099543D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 116K

Publishing Venue

IBM

Related People

Kelkar, S: AUTHOR

Abstract

Switching converter power processors for power factor correction are assuming greater importance and are being used in many systems. The boost topology switching converter can be used as a preprocessor to improve input power factor and disclosed are analog models that facilitate the simulation of such circuits. These models have all of the advantages of earlier models (1) and lead to a simulation technique characterized by ease of use, flexibility, generality and accuracy.

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Simulating Power Factor Correction Switching Converters Using Analog Models

       Switching converter power processors for power factor
correction are assuming greater importance and are being used in many
systems.  The boost topology switching converter can be used as a
preprocessor to improve input power factor and disclosed are analog
models that facilitate the simulation of such circuits.  These models
have all of the advantages of earlier models (1) and lead to a
simulation technique characterized by ease of use, flexibility,
generality and accuracy.

      Fig. 1 shows the power stage of a typical boost topology
switching converter.  The inductor stores energy when the switch S is
on and releases it to the output when the switch is turned off.  The
output capacitor supplies the load while the switch is on.  The
circuit is used as a power factor correction preprocessor by suitably
modifying the control loop such that the input current drawn from the
rectified input is in phase, thus power factors of the order of 0.95
are possible.  The output of the boost converter is a DC voltage of
magnitude higher than the input and forms the bus voltage for the
rest of the power system.  When used for power factor correction the
circuit operates in both continuous and discontinuous modes depending
on the supply voltage.  Since the supply voltage is a rectified sine
wave, there is always a portion of the cycle when the voltage is low
enough to cause discontinuous operation.

      The switching portion of the circuit comprises the transistor
and the output diode and the intention is to develop analog models
for this digital part of the circuit. A composite model suitable for
both continuous and discontinuous modes is developed along with an
equation to help decide the operating mode.  The model is suitable
for large signal simulation, such as transient response and
steady-state power factor calculation.

      The state space averaging technique (2,3) is used to develop
two equivalent nonlinear equations that describes circuit behavior
over a complete cycle for both modes of operation.  The key step is
the combination of the two equations and then the synthesis of an
equivalent circuit. The circuit should retain as much as possible of
the actual circuit topology so as to make it easy to use the model.
Fig. 2 shows the model derived; this model is suitable for large
signal simulation in both modes of operation.  The switching cell
model is complicated only because both modes are included and the
inductor L behaves like a current source in discontinuous mode.  d1
is the duty cycle produced by the control loop and corresponds to the
time when S is on.  d2 corresponds to the time wh...