Investigation into the operation of the single-stage current source charge-pump power factor correction system

This thesis describes the systematic characterisation a power factor correction system for
mains powered appliances. The research is motivated by increasing number of mains
powered devices such as mobile phones, tablets, gaming consoles, computers, etc that
require an Alternating Current (AC) to Direct Current (DC) power converters. It is crucial to
design these power converters as small, efficient, inexpensive and with high power quality as
possible. This thesis focuses on a power factor corrector system that offers all the mentioned
advantages.
This work starts by defining the types of power in AC systems and the power quality
parameters. In addition, the benefits of having high power quality and how it is mandated by
the law are reported. The existing systems to improve power quality and/or provide Power
Factor Correction (PFC) along with advantages and disadvantages of each system are
demonstrated. The full comparison of the PFC systems is provided, and it is shown why the
Current Source Charge Pump PFC (CSCP-PFC) is a convenient method to implement for AC-DC
conversion systems.
A review of state of the art in the CSCP-PFC systems and the technologies underpinning this
system are reported. In addition, the inconsistencies in the existing research on this system
are discussed.
A novel mathematical model based on Fundamental Mode Approximation (FMA) and
describing function of the PFC system is demonstrated and verified. A subsequent
investigation using this model has determined that the model requires further modification
fully capture specific details regarding the circuit’s behaviour. During the course of this
investigation, a novel technique was developed to extract and record the modes of operation
of the system using LTspice package and MATLAB software. The findings showed that the
circuit exhibits an extensive pattern of circuit configurations that cannot be easily represented
by the FMA model developed.
Finally, a hardware based mode sequence identifier was implemented and used to
characterise a practical CSCP-PFC platform. The operation of several converters was
investigated and comparison between practical experiments and simulation made to
determine whether the behaviour of the circuit could be simplified sufficiently to be
conveniently modelled by using describing function techniques.