27-11-2012, 06:02 PM
ADVANCED DC/DC CONVERTERS
4.Advanced DC- DC Converters ~ Prasad ~ Team Tolly.pdf (Size: 6.27 MB / Downloads: 131)
A review of the DC/DC conversion technique development reveals that the
idea was induced from other equipment. Transformers successfully convert an
AC source voltage to other AC output voltage(s) with very high efficiency.
Rectifier devices such as diode, transistor, and thysistor effectively rectify an
AC source voltage to DC output voltage. Nearly eight decades ago, people
sought to invent equipment to convert a DC source voltage to another DC
output voltage(s) with high efficiency. Unfortunately, no such simple apparatus
such as a transformer and/or rectifier was found for DC/DC conversion purpose.
High frequency switch-on and -off semiconductor devices paved the way
for chopper circuits. This invention inspired the idea for DC/DC conversion.
Therefore, the fundamental DC/DC converters were derived from the corresponding
choppers. At present, the fundamental converters — Buck converter,
Boost converter, and Buck-Boost converter — are still the basic circuits
for DC/DC conversion technique in research and development.
The voltage-lift technique is a popular method that is widely applied in
electronic circuit design. Applying this technique effectively overcomes the
effects of parasitic elements and greatly increases the output voltage. Therefore,
these DC/DC converters can convert the source voltage into a higher
output voltage with high power efficiency, high power density, and simple
structure. It is applied in the periodical switching circuit. Usually, a capacitor
is charged during switch-on by a certain voltage. This charged capacitor
voltage can be arranged on top-up to output voltage during switch-off.
Therefore, the output voltage can be lifted. A typical example is the sawtooth-
wave generator with voltage-lift circuit.
The voltage-lift technique has been successfully employed in the design
of DC/DC converters. However, its output voltage increases in arithmetic
progression, stage by stage. The super-lift technique is a great achievement
in DC/DC conversion technology. It is more powerful than the voltage-lift
technique; the output voltage transfer gain of super-lift converters can be
very high, which increases in geometric progression, stage by stage. It effectively
enhances the voltage transfer gain in power series. Four series of superlift
converters created by the authors are introduced in this book. Some
industrial applications verified their versatile and powerful characteristics.
Multiple-quadrant operation is often required in industrial applications.
Most publications in the literature concentrate on the single-quadrant operation.
This fact is reasonable since most novel approaches were derived from
its simple structure. To compensate for these losses, the authors have spent
much time and spirit to develop multiple-quadrant converters, positivenegative
converters in various generations.
Introduction
Conversion technique is a major research area in the field of power electronics.
The equipment for conversion techniques have applications in industry,
research and development, government organizations, and daily life. The
equipment can be divided in four technologies:
• AC/AC transformers
• AC/DC rectifiers
• DC/DC converters
• DC/AC inverters
According to incomplete statistics, there have been more than 500 prototypes
of DC/DC converters developed in the past six decades. All existing
DC/DC converters were designed to meet the requirements of certain applications.
They are usually called by their function, for example, Buck converter,
Boost converter and Buck-Boost converter, and zero current switching
(ZCS) and zero voltage switching (ZVS) converters. The large number of
DC/DC converters had not been evolutionarily classified until 2001. The
authors have systematically classified the types of converters into six generations
according to their characteristics and development sequence. This
classification grades all DC/DC converters and categorizes new prototypes.
Since 2001, the DC/DC converter family tree has been built and this classification
has been recognized worldwide. Following this principle, it is now easy
to sort and allocate DC/DC converters and assess their technical features.
Positive Luo-Pump
The circuit diagram of the positive Luo-pump and some current and voltage
waveforms are shown in Figure 1.12. Switch S and diode D are alternately
on and off. Usually, this pump works in continuous operation mode, inductor
current is continuous in this case. The output terminal voltage and current
is usually positive.
Negative Luo-Pump
The circuit diagram of the negative Luo-pump and some current and voltage
waveforms are shown in Figure 1.13. Switch S and diode D are alternately
on and off. Usually, this pump works in continuous operation mode, inductor
current is continuous in this case. The output terminal voltage and current
is usually negative.
Cúk-Pump
The circuit diagram of the Cúk pump and some current and voltage waveforms
are shown in Figure 1.14. Switch S and diode D are alternately on and
off. Usually, the Cúk pump works in continuous operation mode, inductor
current is continuous in this case. The output terminal voltage and current
is usually negative.