The following is an edited version
of a paper first appeared in the May 1987 issue of the
Power Conversion and Intelligent Motion Magazine.
Advances in Power Sources
AN INVITED PAPER
K. Kit Sum
According to the Statistical Abstracts of the U.S. Department of Energy
Annual Report to Congress in 1981 (D.O.E. Monthly Energy Reviews 1982),
two billion kilowatt-hours (kwh) of energy was sourced by hydro electric
generators in 1900. By the year 1920, the amount of energy sourced was
increased to 20.3 billion kwh; to 51.7 billion kwh in 1940; and to 276
billion kwh in 1980 - this is in addition to 251.1 billion kwh sourced
by nuclear means in the same year. The increase of power generation
is due primarily to the increase of power consumption and the increase
of population. However, it is evident that the increase in population
will never keep up with the increase in power consumption. This condition
prompted careful consideration in the utilization of electrical energy.
Today, it is inconceivable to think of living in a society without
electricity. In today's modern society, almost everything runs on electricity.
The need for power processing is obvious. To elaborate further, one
must go back a few years.
Ever since there were electron tubes, there were linear regulators
whose output voltage is regulated or controlled by a tube functioning
as a variable resistor. Back in the early 1900's, vacuum tubes took
more than an ampere to energize the filament. They were triodes without
cathodes, and were some of the most primitive types of tubes. Electron
tubes of that era were used to build regenerative radio receivers. These
tubes perform the functions of r.f. amplifier, detection, audio amplifier,
and power amplifier. Sometimes all these functions are performed by
the same tube type. Many of these receivers use the loudspeaker armature
for the core of the filter choke while the pulsating direct current
flowing through the choke also served as the energizing current for
the electromagnet, which also functions as the magnet for the loudspeaker.
Needless to say, the resultant audio quality of the receiver was poor
and the sound was modulated by the rectified line ripple frequency.
Power processing for this type of receiver was simple and straightforward;
even half-wave rectification was used in some of them. Many of these
receivers did not have regulators in them. Voltages were allowed to
drift up or down with the line voltage. Others with regulators were
of the linear type, whose design is based on the classical feedback
theory of Black  and Bode [2,3], which formed the foundation of the
voltage mode control. Consumers also grew accustomed to the line ripple
"hum" lurking in the background of the music.
As time went on, electron tube technology improved. Cathodes were
inserted between the filament and the grid to isolate the "hum"
produced by the line frequency. More electrodes, screen and suppressor
screen grids, were inserted to form tetrodes and pentodes, respectively.
By the end of World War II, the functions of electron tubes were well-defined.
There were beam tetrodes for power amplification, triodes for small
signal amplification, pentodes for radio frequency amplification, etc.
The acorn tubes (such as the 954) were developed to handle radio frequency
signals in portable military equipment. Other types of electron tubes
were also designed for use with battery equipment. These tubes were
the so-called miniature tubes and subminiature tubes, and were very
popular in automobile radio receivers. To energize them, a +90 volts
bus is required for the plate circuits, and a 1.5 to 3.0 volts bus is
required for the filaments. Sometimes the filaments of all the tubes
were connected in series with a combination of resistors, and only one
bus was used to run both plate and filament circuits. But, in the automobile,
there is only a 12-volt battery. In order to step up the battery voltage
to run the car radio, a vibrator was used to chop up the d.c. from the
battery, then stepped up with a transformer designed to run at the chopping
frequency of the vibrator.
The vibrator, as used in the automobile, was probably one of the first
commercial attempts in switch mode power supply (SMPS) implementation.
A fundamental problem, in this case, is that the vibrator has moving
parts and physical contacts that can wear out in time, rendering a very
limited life for the power processor. Another problem is that the frequency
of operation is also very much limited by the physical design of the
reeds, thus a humming sound is always audible during operation. Power
conversion was sometimes performed by ferroresonant regulators, which
lack the precision of today's SMPS. At this point, the reader must realize
that power processing is a multi-discipline technology involving control
theory, filter synthesis, signal processing, thermal control, and magnetic
components design. The designer must be conversant with all of the above
mentioned disciplines before an optimum design can be conceived. The
concept of switch mode power conversion was long in existence, but the
technology, up to this point in time, was not quite ready.
On July 15, 1948, the birth of the point contact transistor was announced
. This transistor was somewhat difficult to manufacture, since the
point contact arrangement is, to a great extend, similar to that of
the old crystal detector, which relies on a "whisker" to make
point contact at a sensitive spot on the crystal to obtain optimum detection.
The point contact transistor was quickly replaced by the junction
transistor. The transistor did not reach the consumer market until the
mid 1950's. However, in the earlier days, the junction transistors had
rather low gain and low speed. Thus, many power processing circuits
were designed to operate at well below 20 kHz. The transistor played
a key role in facilitating the practical implementation of solid state
power processing equipment. Research work was carried out to investigate
the behavior of the transistor under large signal conditions . Suffice
to say that, similar to many products, the transistor took a while to
get established in the consumer market. In those early years, many researchers
and engineers toyed with transistors in the area of power oscillators
and processors [6 to 63].
About this time, Shockley  announced the findings of his investigation
- the field effect transistor. This was the early version of a small
signal type junction field effect transistor. The first example of a
power metal oxide silicon field effect transistor (MOSFET) did not appear
until 1959 , and in spite of further progress [66,67], did not reach
the consumer market until the late 1960's.
The big boost in electronics development came when the Soviet Union
launched the Sputnik I, the world's first artificial satellite on October
4 of 1957. In November 1960, John F. Kennedy was elected president of
the United States. He told the Americans to overtake the Soviets at
all costs. By this time, the U. S. had already launched the first successful
earth satellite TIROS I (Jan. 31, 1958). This was the time when the
reduction of size and weight of power processors became a top priority
in the space programs. Also, efforts were made to increase the switching
speed of 'slow' transistors. One of these methods made use of the tunnel
diode  in a most unconventional manner .
If the power processor is viewed as a control system, then the lack
of understanding is quite evident in reports by Raposa, Seaver and Ponsi
 and Poulo and Greenblatt , especially in the behaviour of the
control loop. In an attempt to solve a practical loop stability problem,
Froeschle [75 to 78] designed a push-pull power converter using the
approach now known as current mode control to avoid loop instability.
This is probably one of the first, if not the first, documented application
of the current mode control concept. The "two state modulation
techniques" reported by Froeschle correspond to the well known
continuous conduction mode of operation. Control is achieved by duty
ratio adjustment. This converter was regarded as a state-of-the-art
pulse-width control design at the time.
The first major breakthrough in understanding the behavior of this
type of nonlinear circuits came in 1972 when Wester  announced his
research results in three separate models with a linearization technique,
which allowed the use of linear circuit theory to analyze the control
loop of the basic power converters. The linearized model succeeded in
representing the small-signal transfer properties of the basic power
converters. However, this does not mean that there were no ways to analyze
the power converter . There has always been the large mainframe
computer with numerical approximation techniques or time domain analysis
techniques which when executed, produce quite a few yards of paper in
the printout, from which the designer is expected to gather some meaningful
information or indication of design performance. Those who have tried
these techniques will understand the tedious nature of the interpretation
process. Wester's results provided a simple means of arriving at meaningful
results with physical significance without complicated programs or costly
An important generalization in modeling, which essentially solved
the problem of modeling the transfer properties of switch mode modulators
and converters, was made by Middlebrook and Cuk in 1976 , the birth
of the canonical model. The 1976 paper provided complete small signal
modeling information on the three basic converters operating in the
constant frequency continuous conduction mode. One of the most interesting
results was the discovery of the existence of the right-half-plane zero
in the control-to-output transfer functions of the boost and the buck-boost
converters. This discovery has brought about significant understanding
of the nature of the non-linearities of the two basic converters. However,
the behavior of these two converters are rather different when operating
in the constant frequency discontinuous conduction mode. The details
of converters operating in the discontinuous conduction mode were given
in a later paper . A simplified explanation with explicit design
equations for constant frequency discontinuous conduction mode converters
can be found in .
While doing investigations in power converter modeling, Cuk also discovered
that, by applying the principles of duality, new converters are obtainable.
Thus, the boost converter was found to be a dual of the buck converter.
Delving into the dual of the flyback (buck-boost) converter, Cuk invented
the optimum topology (Cuk) converter (patented) , a converter utilizing
the principle of capacitive energy transfer. Analysis of this converter
in its basic form have been performed with the programmable calculator
Another by-product of Cuk's investigation was that the windings of
the input and output inductors of the new optimum topology converter
could be wound on the same magnetic core, producing the coupled-inductor
Cuk converter. A natural evolution from the coupled-inductor converter
was the integrated magnetic converter [86 to 91]. The reader would be
glad to know that, after many years of design and experimentation, a
workable approach to the design of coupled inductor power converters
is now available, thanks to Cuk and Zhang  who made a thorough investigation
of the problems surrounding the coupled inductor and emerge with some
elegant solutions. Zhang's findings also served to provide an interesting
solution to the integrated magnetic converter problem.
Since most of the popular power conversion topologies (the bridge converter,
the half-bridge converter, the forward converter, and the push-pull
converter) are buck-derived, they can be similarly analyzed with no
State of Power Conversion Technology
SMPS - This is, by far, the most encompassing phase in power conversion.
Broadly speaking, any power processor that uses switch(es) for the purpose
of power conversion can be regarded as a switch mode power supply (SMPS).
Even a switching power amplifier is a form of SMPS. For this reason,
most SMPS fall into one or more of the following categories:
DC to DC Converters
DC to AC Inverters
Off-Line AC to DC Converters
High Voltage Power Supplies
Switching Power Amplifiers
High Frequency Power Converters
DC to DC Converters - As the name implies, this class of power converters
accept d.c. input of one voltage range to produce one or more d.c. output
voltage levels. The d.c. input requirement is usually imposed by the
mobility of the equipment, such as a military communication transreceiver
or an airborne data acquisition system.
Other applications include battery backup of other power systems. The
current technology, with wide availability in the consumer sector, is
the constant frequency pulse-width modulated control power supplies
at the higher power range, with some variable frequency power supplies
at the lower power end.
By definition, the d.c. to d.c. converter does not require larger
input capacitors, since there is usually no hold up time requirement.
It is, therefore, imprudent to compare the power density of this class
of converters with the off-line type converters.
D.c. to d.c. converters are also making adjustments to accommodate
lower output voltage requirements (down to 1.2 volts) by modularization.
Power converters are made in modules of a given output wattage. More
modules are plugged in with the outputs connected in parallel to achieve
higher output power levels. This means that a certain degree of precision
must be designed into each module to provide current sharing capabilities.
The latest technology in this class of converter is reflected in a following
section on High Frequency Power Conversion.
D.C. to A.C. Inverters - This is another class of power processor that
command a great deal of attention in earlier years  but much less
so in recent developments. Much of the design methodology is well known
and serves to extend to quite high power levels. These power processors
are usually intended for single frequency output with the more specialized
ones designed for variable frequency output. They are very popular in
military mobile applications. For the single frequency type inverters,
a few methods of power processing are widely practiced. One method is
to 'chop' the input d.c. at a constant frequency corresponding to a
multiple of the fundamental output frequency (in the case of the push-pull
converter, this frequency will be the second harmonic of the fundamental
for single phase design). The duty ratio is set by constraining the
operating point with the transformer turns ratio to approximately 67%
for the rejection of the third harmonic. To ensure a low distortion
waveform at the output, a series LC tuned circuit is usually followed
by a parallel LC tuned circuit to filter out unwanted harmonics. An
optional third harmonic trap is sometimes included for better waveform
quality. Another method uses pulse-weighted modulation technique 
to obtain a sinusoidal output waveform. This method is highly suited
for MOSFET implementation due to the promising switching characteristics
of the device. By design, this type of power inverter requires somewhat
less stringent output filtering than the previous method. The step-approximated
synthesis method  promised less harmonic distortion and thus, required
Due to the portability of this class of equipment, surface mounting
devices will dominate the future packaging of this type of power processors
for less bulk and weight.
Off-Line A.C. to D.C. Converters - This class of power converter is
the most in demand by both the consumer and the industrial sectors.
These converters serve a wide variety of requirements and applications.
One of the most popular application is found in the computer industry
where these converters are used to run computers and peripherals. Thus,
the requirement for hold-up time is imposed on these power converters
for data preservation in the case of a power transient surge or brown
out. For a 47 to 63 Hz a.c. input, the hold-up time is provided by input
capacitors with effective capacitance approximating to 3 µF per
watt of output power, but with current state of technology it is still
difficult to find suitable capacitors to meet current ripple requirement
at the higher power range. These capacitors are necessarily of the high
voltage type and occupy a substantial amount of volume within the power
converter package. Parallelability is important for this class of power
processor, since customer requirements tend to increase rather than
staying within a prescribed power limit.
One of the major reasons for this increase in sophistication in power
converter design is due to the system designer/manager, who failed to
include some of the features into the 'system' as an integral design;
but left them all to the power design engineer. The power processor
should, at all times, be regarded as part of a system and be designed
as such. It should never be regarded as an add-on item to run a particular
system. It is foreseeable that the optimum system will have the power
supply designed for and with the system, such that the power supply
is not required to operate as a stand-alone item. By designing the power
supply with the system, it is possible to optimize packaging, heat-sinking,
power-up sequencing, cooling, etc. to a new level of performance, reliability
and power density. In future, off-the-shelf power supplies will have
to make adjustments to match an optimum system design philosophy.
One of the latest awareness, as power output level reaches 2kw and
beyond, is the power factor improvement problem. This is due to the
peak-charging of the input capacitors within a switching period which
caused a high peak current for a short period of time, resulting in
inefficient usage of the present form of input power.
Surface mounting components are also beginning to take the place of
the conventional components in this class of power converters.
For device utilization, the senseFET (announced by Motorola in Electronic
Design, Feb.20, 1986), which has the capability of sensing the current
through the device facilitated by an extra electrode, is expected to
be found in future designs of this class of power converters. International
Rectifier is expected to second source this device.
Frequency synchronization will be important for large systems requiring
more than one power supply. Parallelling and current sharing will be
common place in such a system.
High Voltage Power Supplies - As far back as 1891, Nikola Tesla performed
high frequency high voltage experiments in the United States . The
development of high voltage d.c. was due to the pioneering work of Cockcroft
and Walton [100,101]. In 1939 a high voltage photography technique was
perfected by Kirlian  who claimed to be able to capture the human
aura on film. Another area of photography requiring the use of high
voltage is X-ray photography for which a high voltage ranging from 30
to 300 kV is required . Other high speed photography includes the
generation of spectrograms in which the spectrum of a faintly radiating
source in time periods of a few microseconds is observed through an
image intensifier sourced by a high voltage power supply. In this case,
a four-stage image intensifier with a radiant gain of 105 to 106 is
placed at the spectrograph exit for this purpose .
The high voltage power supply is also used in more advanced image
intensifier tubes with microchannel plates [104 to 106]. Some of these
image tubes were installed with suitable optics for night vision enhancement,
known as 'green eyes' to military personnels. The most popular ones
were those of the 18mm second generation type, which were installed
in pairs for bifocal low light vision applications . The design
of the second generation 18mm image tube power supply was known for
its difficulties due to stringent size, weight, low noise and low power
consumption specification. Each power supply typically accommodates
an input voltage range of 2 to 2.7 V.d.c., not exceeding 14 mA of nominal
input current for the delivery of one +6 kV output, one -800 V output,
and one +200 V output, with automatic brightness control and bright
source protection shut-down features. The third generation is even more
stringent on requirements. The tube remains at the same size, but with
much higher resolution, consumes more power, but maintains the same
input power budget for the new power supply. Current development on
night vision technology has been more concentrated in the forward looking
infra red (FLIR) systems.
Note that for a 20 kV power supply, 0.1% output voltage ripple represents
20 V peak of ripple amplitude, or a swing of ±40 V peak-to-peak.
For a tightly regulated output, this ripple appears on top of the voltage
divider which samples the output voltage for feedback control. This
voltage divider is usually made up of one high value (as well as high
voltage) resistor in the range of 10 M" to a few gigaohms, and
a low value resistor. The potential drop across the high value resistor
is, by design, very high. In many cases, this resistor acted as a radiator
and affect the control circuit components in the proximity. Sometimes
loop stability is not achievable until the high voltage resistor is
Low noise high voltage power supplies are also required for applications
to devices such as the traveling wave tube (TWT) and the laser (Light
Amplification by the Stimulated Emission of Radiation).
The TWT was particularly sensitive to phase noise, which is one of
the major reasons that variable frequency type power supplies are rarely
found in a TWT amplifier system .
Other applications of the high voltage power supply include the radar
modulator , xenon or mercury arc lamp power supply circuits, high
resolution computer monitors, and television receivers.
The state of high voltage electronic technology was nicely summarized
by Williams .
Switching Power Amplifiers - One of the first known switching power
amplifiers is invented by Bedford in 1931 , who later also took
out another patent  on switching amplifier. This type of amplifier
is later known as the class D amplifier. Other pioneering work in this
area was reported by hmichen  and later by Page, et al. ,
Robertson , and Chudobiak and Page . The work by Stark 
follows along a similar line of description of .
Many Class D power amplifier techniques form the basis for switch
mode regulated power supplies. Class D amplifiers use pulse modulation
techniques to convert input signals to pulse trains, which are then
used to recover input signal information from amplified pulse trains.
A high theoretical efficiency of 100% is obtainable with 'ideal' components.
The switching power amplifier is expected to find a good future in public
address audio systems because of its high efficiency and light weight.
Except for the critical audiophile, the switching amplifier is gaining
acceptance in products such as guitar amplifiers and some electronic
Recent high efficiency switching amplifiers have been reported by Koenig
 and Lee & Troiani .
High Frequency Power Conversion - In recent years, the interest in
high frequency power conversion has been increased substantially; partly
due to the demand from equipment manufacturers for more compact and
lighter weight power processors and, partly due to the advancement in
circuit integration technology, reflecting that most of the bulk of
the system would soon be the power supply (unless it is also proportionately
reduced in size).
Higher conversion frequency is a solution, at least in principle .
But maturity in many areas of research is required to bring high frequency
high power density converter realization into perspective. These research
areas are: (a) Power Topology, (b) Magnetic Materials, (c) Capacitors,
(d) Semiconductor Devices, (e) Circuit Fabrication Techniques, and (f)
(a) Power Topology: This is a multi-dependency choice influenced by
power level, method of conversion and control, nature of the input power,
and the application intended.
As far as the method of conversion is concerned, the resonant type
of converter is currently attracting a lot of attention. A good description
of different classes of resonant converters and their modes of operation
can be found in a series of articles by Todd and Lutz . Other approaches
worthy of attention are given in [125,126,127].
For low power d.c. to d.c. applications, the forward converter appears
to have taken a foothold in the military market . This converter
operates in the semi-resonant mode. The resetting of the forward converter
power transformer is performed by a novel circuit . This power
converter claims a power density of 24 watts/in.3 but requires external
add-on heat-sinking arrangement. This is one off-the-shelf item that
is not designed to function as a stand-alone part. It is, therefore,
prudent to assume that the state-of-the-art power density is still under
24 watts/in.3 In terms of power density, it is evident that this converter
should not be compared with off-line power converters, which are being
penalized by the inclusion of large input capacitors for meeting the
hold-up time requirement.
Power conversion researchers have also looked into different standard
topologies for high frequency power conversion. One of these researchers
is Schlecht , who suggested that the single-ended forward converter
is among the best, if not the best (for component count, simplicity,
(b) Magnetic Materials: A limitation in increasing the power density
of a converter is that the magnetic components are limited to a minimum
of one turn on a winding. Note that the implementation of fractional
turns are neither simple nor economical. For off-line designs, the turns
ratio becomes approximately 14:1 for a 5-volt output power converter.
The remaining problem is to find a core with a wire window large enough
to accommodate the number of turns (14 in this case) and the current
capability of the winding. With this thought in mind, it is conceivable
that operation above a pre-determined frequency will not reduce the
core size significantly.
As far as magnetic materials are concerned, Schlecht  also indicated
that for a 50-watt d.c. to d.c. converter operating at 10 MHz with 4C4
material, the flux swing had to be reduced to .05 Tesla to avoid excessive
core loss. This is an indication of the limitation in size reduction.
It is noteworthy that as the frequency goes up, the required permeability
of the core material decreases. At frequencies approaching 50 MHz, the
permeability of the core material could practically be reduced to that
of air. Under this condition, the air-core inductor becomes a radiator
similar to the radiation output coil of a radio transmitter. The normal
interference filtering problem due to conducted emission will be transformed
to one of shielding due to radiation.
Some results of advancement in magnetic core material and magnetic
component implementation can be found in Ueda, et al. , Matsuki,
et al. , and Pollack and Smith .
(c) Capacitors: There are very few types of capacitors in the market
to-day that are suitable for high current ripple, high frequency and
high voltage applications . Many capacitor manufacturers do not
specify the capacitor in a manner required by the power converter design
engineer. Sometimes, the factory test conditions are insufficient for
the characterization of the capacitor for power conversion purposes.
As a result of the inadequacy of the manufacturers' specification, failure
modes have to be studied separately by the user.
One of the recent capacitors from Nippon Electric Corporation is the
crushed-ceramic capacitor with working voltages of 25 and 50 volts.
It has low equivalent series resistance (esr) and is characteristically
a promising candidate for high frequency power conversion. Unfortunately,
the price of this unit is far from being competitive.
A more interesting line of capacitor called the "SupraCap"
is being marketed by AVX Corporation . This capacitor is the multi-layer
ceramic type exhibiting very low esr (a few milliohms) in the frequency
range of 40 kHz to 100 kHz. This line of capacitors has voltage ratings
ranging from 50 to 500 volts.
The current state-of-the-art is aiming at high dielectric constant for
reduction in size, low esr for high current ripple capability and high
voltage for industry requirement.
(d) Semiconductor Devices: At present, it appears that the MOSFET
is the prime candidate for high frequency power conversion. But experimental
circuits have indicated that the output capacitance (Coss) of the existing
devices are too high (a few hundred pico farads) for efficient high
frequency power processing. An obvious area of improvement is, therefore,
the reduction of the output capacitance of these devices. Another important
area of improvement is the reduction of the device ON resistance (RDS(on)).
For high frequency power processing, the drain-gate capacitance also
plays an important role. However, this capacitance can be 'neutralized'
by classical circuit techniques used in tube circuits.
In regard to characterization of rectifiers, Carsten  suggested
that the quantity 'reverse recovered charge per ampere of forward current'
be used as the basis for switching performance evaluation.
A glimpse into the advances in device technology can be found in a
report by Korman, et al. . (e) Circuit Fabrication Techniques:
The power density of a power converter is very much dependent on the
packaging technique used by the manufacturer. Approximately ten years
or so ago, Zenith Corporation was advertising their television sets
as having the 'real guts' for real point-to-point hard wiring. That
was not a problem for a floor model console set.
Today, possibly one of the most enlightening experience is to open
the chassis of a video cassett recorder to observe the packaging techniques
used in the manufacture of such a sophisticated piece of equipment.
The indication is that the circuit fabrication technique plays a very
important role in the final appearance and performance of the product.
Power conversion is a continually evolving technology. As the conversion
frequency increases, the packaging and fabrication techniques are expected
to change accordingly. Some of these efforts are reflected in works
by Jones and Vergez  and Estrov .
For the more conservative power supply manufacturers, the logical
evolvement would be to go from 'surface mounted pcb' to a combination
of 'surface mounted pcb with hybrids'; and eventually to 'high voltage
power integrated circuits with any of the previous combinations' for
optimum packaging fabrication.
The surface mounted pcb is attractive for present development because
the printed circuit board (pcb) has no size limitation, whereas the
size of the ceramic substrate of the hybrid circuit is limited by its
Due to its anticipated application at high frequencies, it would appear
that printed resistors on hybrid circuits are at a disadvantage because
of conductor (resistive tract) path length tend to occupy a substantial
area and is susceptible to noise pick-up. A simple solution would be
to substitute printed resistors with chip resistors.
(f) Synchronous Rectifiers: Presently, all MOSFET's are manufactured
with a body diode which is slower than the MOS device itself. When connected
into a synchronous rectifier circuit, the direction of the polarity
of this body diode directly affects the performance of the circuit,
depending on which direction the diode is facing. Perhaps a more specialized
device could be designed for this particular application in the near
Noting that the inefficiency in low voltage output power supplies
is always due to the inefficient rectifier. Improvement in this area
would definitely constitute great improvement in temperature rise as
well as power density, since there would be less heat sinking requirement.
A more suitable device for synchronous rectification has yet to be
On April 4, 1987, President Reagan  announced that NASA is to go
ahead with a scaled-down version of the space station. The finishing
date has been targeted for mid-1990 at a cost of $10.9 billion. One
of the most controversial issues in the power conversion circle is the
method of power distribution in a space station. A quick insight into
the complexity of this task can be obtained from a few recent articles
[151 to 154].
A crude and non-exhaustive overview of the advances of power sources
for approximately half a century have been provided. To enhance the
interest of the reader, various applications of power converters to
specific devices were briefly outlined. References have been included
for further reading and follow-up investigation purposes. The author
would appreciate the opportunity of receiving comments and corrections
of errors from helpful readers.
1. H. S. Black, Stabilized Feedback Amplifiers, Bell Systems Technical
Journal, January 1934.
2. H. W. Bode, Relations Between Attenuation and Phase in Feedback Amplifier
Design, Bell Systems Technical Journal, 1940.
3. H. W. Bode, Network Analysis and Feedback Amplifier Design, Van Nostrand
Reinhold, New York, 1945.
4. J. Bardeen and W. H. Brattain, The Transistor, a Semiconductor Triode,
Physics Review, Vol.74, No.2, p.230, July 15, 1948.
5. J. J. Ebers and J. L. Moll, Large Signal Behaviour of Junction Transistors,
Proceedings of the Institute of Radio Engineers, Vol.42, p.1761, 1954.
6. R. L. Bright, et al., Transistors as On-Off Switches in Saturable-Core
Circuits, Electrical Manufacturing, Dec. 1954, p.79.
7. R. L. Bright and G. H. Royer, Electrical Inverter Circuit, U.S. Patent
No. 2783384, February 26, 1957.
8. G. Bruck, R. Harter, I. M. Wilbur, Power Supply Circuit Using Controllable
Electron Solid State Devices, U. S. Patent No. 2798160, July 2, 1957.
9. G. W. Bryan, Application of Transistors to High Voltage Low Current
Supplies, Proc. I.R.E., Vol. 40, 1952, p.1521.
10. J. W. Caldwell & T.C.G. Wagner, Boosting Power Transistor Efficiency,
Electronics, Nov.21, 1958, p.86.
11. E. L. Campbell, Combination Power Supply and Modulator Using Transistors,
Q.S.T., Sept. 1958, p.18.
12. C. H. R. Campling, Differential Magnetic Multivibrators, A.I.E.E.
paper number 57-769.
13. C. H. R. Campling, A Transistor D.C. Converter, Electronic Engineering,
Vol.30, 1958, p.508.
14. C. H. R. Campling, Magnetic Inverter Uses Tubes or Transistors,
Electronics, March 14, 1958, p.158.
15. W. H. Card, Four Transistor Inverter Drives Induction Motor, Electronics,
Vol. 32, Feb.20, 1959, p.60.
16. K. Chen and A. J. Schiewe, A Single Transistor Magnetic Coupled
Oscillator, Trans. A.I.E.E. Vol. 75, Part 1, 1956, p.396.
17. M. Cohen and D. Arany, Subminiature Beacon for Guided Missiles,
Electronics, April 1957, p.144.
18. E. H. Cooke-Yarborough, et al., D. C. Converter Circuit, British
Patent Application No. 20668, 1953.
19. R. O. Decker and F. Gourash, Operational Magnetic Amplifier with
Audio Frequency Transistor Power Supply, Trans.A.I.E.E., Vol.74, Part
1, 1955, p.490.
20. G. M. Ford, 400-Cycle Inverter is Transient-Proof, Aviation Age,
Vol.29, May 1958, p.150.
21. E. Franklin and J. B. James, The Application of Transistors to the
Trigger, Ratemeter and Power Supply Circuits of Radiation Monitors,
Proc. I.E.E., Paper No. 2049 M, Vol. 103B, March 1956, p. 497.
22. G. Grimsdell, The Economics of the Transistor D.C. Transformer,
Electronic Engineering, Vol.27, 1955, p.268.
23. R. M. Hubbard, A Transistorized D.C. to A.C. Inverter with Good
Frequency Regulation, Nat. Conf. Aeronautical Electronics, Dayton, Ohio,
May 14, 1956.
24. P. J. H. Janssen, Circuit Arrangement for Converting a Low Voltage
into a High Direct Voltage, U.S. Pat. No.2780767, February 5, 1957.
25. P. J. H. Janssen and C. De Vijver, Ringing Choke D. C. Converter
Circuit, Brit.Pat.App. No.21263/54.
26. J. L. Jensen, An Improved Square Wave Oscillator, Trans.I.R.E.,
Vol. CT-4, 1957, p.276.
27. J. L. Jensen, Saturable Core Transformer Oscillators, U.S. Patent
No. 2774878, December 18, 1956.
28. R. P. Johnson, High Power Transistorized Mobile Power Supply, Q.S.T.,
April 1958, p.11.
29. D. L. Johnston, Transistor H.T. Generator: Replacement Unit for
Hearing Aid H.T. Batteris, Wireless World, Vol.60, 1954, p.518.
30. R. L. Karl, 100 Watt Transistor Mobile Power Unit, Q.S.T., June,
31. A. Kruper, Switching Transistor Substitute for Mechanical Choppers,
Trans.A.I.E.E., Vol.74, Part 1, p.141.
32. L. H. Light, Transistor Power Supplies: Circuits for Obtaining H.T.
and E.H.T. from Low-Voltage Sources, Wireless World, Vol. 61, 1955,
33. L. H. Light, Circuit Arrangement for Converting a Lower D.C. Voltage
into a Higher D.C. Voltage, U.S. Patent No.2791739, May 7, 1957.
34. L. H. Light and P. M. Hooker, Transistor D.C. Convertors, Proc.I.E.E.,
Vol. 102B, Paper No. 1862 R, April 1955, p.775.
35. J. F. Lohr, Transistorised Static Inverter Design, Electronic Design,
April 16, 1958.
36. H. A. Manoogian, Transistor Photoflash Power Converter, Electronics,
August 29, 1958, p.29.
37. W. A. Martin, Development of Transistor Inverter at 20 kc/s Using
Power Transistors, Trans.I.R.E., Vol. I-6, 1957, p.118.
38. A. J. Myerhoff and R. M. Tillman, A High-Speed Two-Winding Transistor-Magnetic-Core
Oscillator, Trans. I.R.E., Vol. CT-4, p.228.
39. A. G. Milnes, Phase Locking of Switching Transistor Converters for
Polyphase Power Supplies, Trans.A.I.E.E., Vol.74, Part 1, 1955, p.587.
40. A. G. Milnes, Transistor Circuits and Applications, Proc. I.E.E.,
Vol. 104B, Paper No. 2368 R, May 1957.
41. D. C. Mogen, Operation of Saturable-Core Square-Wave Oscillator,
Nat.Conf. Aeronautical Electronics, Dayton, Ohio, 1956.
42. H. T. Mortimer, D.C. to A.C. Square-Wave Static Converter and Amplifier,
Naval Research Laboratory, Washington, D.C., N.R.L. Report No. 4582,
July 27, 1956.
43. J. Noordann, The Balanced Transistor Converter, Philips Telecom.
Review, Vol. 18, No.3, Sept. 1957.
44. F. Oakes, Design Considerations of Junction Transistor for the Conversion
of Power from Direct to Alternating Currents, Proc. I.E.E., Vol. 104B,
Paper No. 2299 R, January 1957, p.307.
45. D. A. Paynter, An Unsymmetrical Square Wave Power Oscillator, Trans.I.R.E.,
Vol. CT-3, 1956, p. 64.
46. D. A. Paynter, A Single Power Transistor D.C.- D.C. Converter, Proc.A.I.E.E.
and I.R.E. Conf. on Transistor Circuits, Pennsylvania University, February
47. D. A. Paynter, Transistor A.C.- D.C. Converters, Nat. Conf. on Airborne
Electronics, May 9, 1955.
48. A. R. Pearlman, Transistor Power Supplies for Geiger Counters, Electronics,
Vol.27, August 1954, p.144.
49. B. Reich, Report on Power Transistors for Converters, Electronic
Design, Vol.5, March 15, 1957, p.22.
50. G. H. Royer, Switching Transistor D.C. to A.C. Converter Having
an Output Frequency Proportional to the D.C. Input Voltage, Trans. A.I.E.E.,
Vol.74, Part 1, 1955, p.322.
51. S. Schenkerman, Designing Transistor D.C. to A.C. Converters, Electronics,
September 26, 1958.
52. P. L. Schmidt, Voltage Conversion with Transistor Switches, Bell
Labs. Record, Vol. 36, 1958, p.60.
53. J. S. Smith, D. C. Transformers, Trans. I.R.E., Vol. VC-6, 1956,
54. R. R. Smyth, Transistors as Power Conversion Devices, Proc. A.I.E.E.
and I.R.E. Conf. on Transistor Circuits, Pennsylvania University, February
55. R. R. Smyth and M. G. Schorr, Transistorised Power Sources for D.C.
to A.C. and D.C. to D.C. Conversion, Electronic Design, November 15,
56. E. E. Thompson, A Transistorised D.C. Power Supply Employing a Novel
Method of Voltage Regulation, Program of the 1958 Canadian Convention
of the I. R. E.
57. P. M. Toscano and J. B. Heffner, C.R.T. Power Supply uses Transistor
Oscillator, Electronics, Vol.29, September, 1956.
58. G. S. Tsykin, Semiconductor D.C. Converters, Radio Engineering,
Vol. 12, 1957, p.70.
59. G. C. Uchrin, Transistor Power Converter Capable of 250 watts D.C.
Output, Proc. I.R.E., Vol. 44, 1956, p. 261.
60. G. C. Uchrin and W. O. Taylor, A New Self-Excited Square Wave Transistor
Power Oscillator, Proc. I.R.E., Vol. 43, 1955, p. 99.
61. H. H. Van Abbe and J. J. Rongen, The Design of Transistor D.C. Converters,
Electronic Applications, Vol. 16, Autumn 1955, p. 59.
62. R. L. Van Allen, A Variable Frequency Magnetic-Coupled Multivibrator,
Trans. A.I.E.E., Vol. 74, Part 1, 1955, p. 356.
63. F. Weitzsch, The Application of PNP Junction Transistors as Electronic
Switches, Electronic Applications, Vol. 16, Spring 1956, p.154.
64. W. Shockley, The Unipolar Field Effect Transistor, Proc. I.R.E.,
Vol. 40, November 1952.
65. H. A. R. Wegener, The Cylindrical Field Effect Transistor, IEEE
Trans. Electron Devices, Vol.6, 1959.
66. S. Teszner and R. Giquel, Gridistor - A New Field Effect Device,
Proc. IEEE, Vol. 52, 1964, pp. 1502-1513.
67. R. Zuleeg, Multi-Channel Field Effect Transistor Theory and Experiment,
Solid State Electronics, Vol.10, 1967, pp. 559-576.
68. L. Esaki, Physical Review, Vol. 109, No.2, p.603, January 1958.
69. R. E. Morgan, High Frequency Time-Ratio Control with Insulated and
Isolated Inputs, IEEE Trans. on Magnetics, March 1965.
70. R. E. Morgan, A New Control Amplifier Using a Saturable Current
Transformer and a Switching Transistor, A.I.E.E. Trans. (Comm. and Electronics),
Vol. 77, November 1958.
71. R. E. Morgan, A New Magnetic-Controlled Rectifier Power Amplifier
with a Saturable Reactor Controlling On Time, Paper T-121, A.I.E.E.
Special Technical Conf. on Nonlinear Magnetics and Mag. Amps., Philadelphia,
Pa., October 26-28, 1960.1
72. R. E. Morgan, Conversion and Control with High Voltage Transistors
with Insulated Inputs, 1968 INTERMAG Conf. Digest.
73. F. L. Raposa, R. K. Seaver and R. A. Ponsi, Non-Dissipative DC to
DC Regulator-Converter Study, Final Technical Report, June 15, 1964
to March 31 1967, Contract No. NAS 5-3921, Goddard Space Flight Center,
Greenbelt, Maryland, Report Access Number N67 31460.
74. L. R. Poulo and S. Greenblatt, Research Investigations on Feedback
Techniques and Methods of Automatic Control, Bose Corporation, Natick,
Massachusetts, Contract Number DAAB07 -67-C-0520, Report Access Number
AD 687311, April 1969.
75. T. A. Froeschle, Two State Modulation Techniques for Power Systems,
Semi-Annual Report, Bose Corporation, Natick, Massachusetts, Contract
Number DA28-043-AMC-02282(E), Report Access Number AD 815603, June 1967.
76. T. A. Froeschle, Two State Modulation Techniques for Power Systems,
Semi-Annual Report, Bose Corporation, Natick, Massachusetts, Contract
Number DA28-043-AMC-02282(E), Report Access Number AD 823239, November
77. T. A. Froeschle, Two State Modulation Techniques for Power Systems,
Semi-Annual Report, Bose Corporation, Natick, Massachusetts, Contract
Number DA28-043-AMC-02282(E), Report Access Number AD 831768, April
78. T. A. Froeschle and J. J. Wawzonek, Two State Modulation Techniques
for Power Systems, Semi-Annual Report, Bose Corporation, Natick, Massachusetts,
Contract Number DA28-043-AMC-02282(E), Report Access Number AD 844635,
79. G. W. Wester and R. D. Middlebrook, Low Frequency Characterization
of Switched Dc-to-Dc Converters, Proc. IEEE Power Electronics Specialists
Conference, 1972 Record.
80. B. A. Wells, et al., Analog Computer Simulation of a dc to dc Flyback
Converter, Suppl. to IEEE Trans. Aerospace, Vol. AES-3, November 1967,
81. R. D. Middlebrook and S. M. C~uk, A General Unified Approach to
Modelling Switching Converter Power Stages, Proc. IEEE Power Electronics
Specialists Conference, 1976 Record.
82. S. M. C~uk and R. D. Middlebrook, A General Unified Approach to
Modelling Switching Dc-to-Dc Converters in Discontinuous Conduction
Mode, Proc. IEEE Power Electronics Specialists Conference, 1977 Record.
83. K. K. Sum, On the Design of Constant Frequency Discontinuous Conduction
Power Converters, Proc. Power Electronics Design Conference, San Jose,
California, October 1986.
84. S. M. C~uk and R. D. Middlebrook, A New Optimum Topology Switching
Dc-to-Dc Converter, Proc. IEEE Power Electronics Specialists Conference,
85. B. P. Erisman and K. K. Sum, Analysis of Optimum Topology Converter
Using HP-41 Calculator, Powerconversion and Intelli- gent Motion, November
86. G. E. Bloom and A. Eris, Practical Design Considerations of a Multi-Output
C~uk Converter, IEEE Power Electronics Specialists Conference 1979 Record.
87. S. M. C~uk, DC-to-DC Switching Converter with Zero Input and Output
Current Ripple and Integrated Magnetics, U.S. Patent No.4257087, March
88. G. E. Bloom and A. Eris, DC-to-DC Converter, U.S. Patent No.4262328,
April 14, 1981.
89. S. M. C~uk and R. D. Middlebrook, DC-to-DC Converter Having Reduced
Ripple Without Need for Adjustments, U.S. Patent No. 4274133, June 16,
90. G. E. Bloom and R. Severns, Magnetic Integration Methods for Transformer
Isolated Buck and Boost Converters, Proc. of POWERCON 11, April 1984.
91. S. M. C~uk, A New Zero Ripple Switching Dc-to-Dc Converter and Integrated
Magnetics, IEEE Power Electronics Specialists Conference 1980 Record.
92. Z. Zhang and S. M. C~uk, Coupled Inductor Analysis and Design, Proc.
IEEE Power Electronics Specialists Conference, 1986 Record.
R. L. Bright, Junction Transistors Used as Switches, Trans.A.I.E.E.,
Vol. 74, Part 1,1955, p.111.
93. R. D. Middlebrook, Design Techniques for Preventing Input-Filter
Oscillations in Switched-Mode Regulators, Proc. POWERCON 5, the Fifth
National Solid-State Power Conversion Conference held in May 4-6, 1978,
in San Francisco, California.
94. K. K. Sum, Switch Mode Power Conversion - Basic Theory and Design,
Marcel Dekker, Inc., 270 Madison Avenue, New York, N.Y. 10016, September
95. B. D. Bedford and R. G. Hoft, Principles of Inverter Circuits, John
Wiley & Sons, Inc., New York 1964.
96. R. Ruble and W. Treitel, A New Technique for Simplifying Sinewave
Synthesis Inverter Design, Proc. POWERCON 6, 1979.
97. J. P. Vergez, Jr. and V. Glover, Low Power Solid State Inverters
for Space Applications, Paper No. 20/4, WESCON 1966 Record.
98. R. W. Lye, ed. Power Converter Handbook - Theory, Design, Application,
Power Delivery Dept., Canadian General Electric Co. Ltd., 107 Park Street
North, Peterborough, Ontario, Publication No. PGEI-10355A, 2nd printing
99. N. Tesla, Lectures, Patents, Articles, Beograd, Yugoslavia (1956).
Available from W. S. Heinman, Imported Books, 1966 Broadway, New York,
N.Y. 10023; I. Hunt and W. Draper, Lightning in His Hand, the Life of
Nikola Tesla, Sage Books, c/o Swallow Publications, Chicago, IL (1964).
100. J. D. Cockcroft and E. T. S. Walton, Experimental with High Velocity
Positive Ions - (I) Further Developments in the Method of Obtaining
High Velocity Positive Ions, Proc. Royal Society, A, Vol.136, pp.619-630,
101. E. Everhart and P. Lorrain, The Cockcroft-Walton Voltage Multiplying
Circuit, The Review of Scientific Instruments, Vol.24, No.3, pp.221-226,
102. S. Krippner and D. Rubin, ed., Galaxies of Life, the Human Aura
in Acupuncture and Kirlian Photography, Gordon and Breach, New York,
N.Y. (1973); Republished with minor revisions under the title: The Kirlian
Aura, Photographing the Galaxies of Life, Doubleday, New York, N.Y.
103. P. Kafalas, An Image Intensifier System for High-Speed Spectrography,
Proc. 8th International Congress on High-Speed Photography, Stockholm,
June 23-29, 1968, pp.182-185.
104. D. J. Ruggieri, Microchannel Plate Imaging Detectors, IEEE Trans.
Nuclear Science, Vol. NS-19, No.3, June 1972.
105. Paul Henkel, et al., High Gain Microchannel Plates, IEEE Trans.
Nuclear Science, Vol. NS-25, No.1, February 1978.
106. A. Lundy, et al., Avalanche Transistor Pulser for Fast-Gated Operation
of Microchannel Plate Image Intensifiers, IEEE Trans. Nuclear Science,
Vol. NS-25, No.1, February 1978.
107. A Review, Battlefield Night Vision, Miltronics, Vol.3, No.2, June
1982, pp.73-76 and p.99.
108. Y. Cheron, et al., Study of a Resonant Converter Using Power Transistors
in a 25 kW X-Rays Tube Power Supply, Proc. ESA Sessions at 16th Annual
IEEE PESC, Univ. Paul Sabatier, Toulouse, 24-28 June, 1985, pp.295-306.
109. W. Muller, The Influence of Mode Switching on Voltage Stability
and Current Ripple Control of a Pulsed TWT, IEEE Power Electronics Specialists
Conference 1985 Record.
110. F. C. Schwarz and J. B. Klaassens, A Radar Power Supply Without
a Voltage Droop, IEEE Power Electronics Specialists Conference 1983
111. J. W. Williams, High Voltage Electronics - An Overview, IEEE Power
Electronics Specialists Conference 1980 Record.
112. I. Arens and F. Forattini, Failure Analysis of a High-Voltage System
by Probing on the Low-Voltage Side, IEEE Power Electronics Specialists
Conference 1985 Record.
113. G. R. Sundberg, A New Very High Voltage Semiconductor Switch, IEEE
Power Electronics Specialists Conference 1985 Record.
114. B. D. Bedford, U. S. Patent No.389855, September 25, 1931.
115. B. D. Bedford, U. S. Patent No.1874159, August 30, 1932.
116. J. P. hmichen, L'amplificateur "Classe D", Electronique
Industrielle, March-April 1955.
117. D. F. Page, et al., On Solid State Class D Systems, Proc.IEEE (Correspondence),
Vol. 53, April 1965.
118. J. Robertson, Solid-State Amplifier Gives 1.2 kW at 95% Efficiency,
Electronic News, sec.1, p.5, Monday, May 10, 1965.
119. W. J. Chudobiak and D. F. Page, Frequency and Power Limitations
of Class-D Transistor Amplifiers, IEEE Journal of Solid-State Circuits,
120. P. A. Stark, Class-D For Efficiency, in three parts in Audio, June,
July and August 1964.
121. L. W. Koenig, Very High Efficiency, High Power VLF/LF Amplifier,
IEEE Power Electronics Specialists Conference 1983 Record.
122. J. Lee and C. Troiani, Applications of Power MOSFET Devices in
an Ultra High Efficiency Servo Amplifier, Ninth International PCI Conf.,
123. B. Carsten, Radio Frequency Power Conversion - Fad or Future? Powerconversion
& Intelligent Motion, January 1986.
124. P. C. Todd and R. W. Lutz, Practical Resonant Power Converters
- Theory and Application, Parts I, II, and III, Powertechnics Magazine,
Vol.2, Nos. 4, 5, and 6, April, May, and June, 1986.
125. P. J. Carlson, A Duty-Cycle Controlled Series Resonant Converter,
Powertechnics Magazine, Vol. 2, No.3, March 1986.
126. B. Carsten, A Hybrid Series-Parallel Resonant Converter for High
Frequencies and Power Levels, Second International High Frequency Power
Conversion Conference 1987.
127. B. Carsten, Design Tricks, Techniques and Tribulations at High
Conversion Frequencies, Second International High Frequency Power Conversion
128. P. Vinciarelli, Forward Converter Switching at Zero Current, U.
S. Patent No.4415959, Nov. 15, 1983.
129. P. Vinciarelli, Optimal Resetting of the Transformer's Core in
Single Ended Forward Converters, U. S. Patent No.4441146, April 3, 1984.
130. M. Schlecht, 10 MHz Switcher Seminar, held at Jet Propulsion Laboratory,
January 15, 1986.
131. R. Ueda, et al., Fundamental Analysis for Design of a Divided Open-Core
Type Inductor, IEEE Trans. Magnetics, Vol. MAG-22, No.5, September 1986.
132. H. Matsuki, et al., Performance of Miniaturized Magnetic Devices
in Cloth Structure, IEEE Trans. Magnetics, Vol. MAG-22, No.5, September
133. H. C. Pollack and A. L. Smith, Slim Profile Power Inductors Made
by Powder Metallurgy, IEEE Trans. Magnetics, Vol. MAG-22, No.5, September
134. N. Kato, et al., Ferrite Substrates for High-Frequency Switching
DC-to-DC Converter Applications, IEEE Trans. Magnetics, Vol. MAG-21,
No.5, September 1985.
135. A. Kamada, et al., Optimum Ferrite Core Characteristics for a 500
kHz Switching Mode Converter Transformer, IEEE Trans. Magnetics, Vol.
MAG-21, No.5, September 1985.
136. V. J. Thottuvelil, et al., High-Frequency Characteristics of Amorphous
Metallic-Alloy Tape-Wound Cores, IEEE Power Electronics Specialists
Conference 1983 Record.
137. B. Carsten, High Frequency Conductor Losses in Switchmode Magnetics,
Eleventh International PCI Conference 1986.
138. R. A. Frantz, Reliability Considerations for Metallized Plastic
Film Capacitors Under High-Stress AC Waveforms, IEEE Power Electronics
Specialists Conference 1981 Record.
139. B. Travis, Capacitors, EDN Magazine, January 22, 1987.
140. B. Carsten, Reverse Recovery Characteristics of High Speed Rectifiers,
Powerconversion and Intelligent Motion, February 1986.
141. C. S. Korman, et al., High Efficiency, High Frequency Power Supply
Development - New Advances in Device Technology, First International
High Frequency Power Conversion Conference 1986.
142. C. B. Jones and J. P. Vergez, Application of PWM Techniques to
Realize 1 MHz Off-Line Switching Regulator with Hybrid Implementation,
Proc.IEEE Applied Power Electronics Conference 1986.
143. A. Estrov, Packaging of 1 MHz Power Supplies, 2nd Int'l. High Frequency
Power Conversion Confe. 1987.
144. C. Mullett and R. Hiramatsu, An Improved Parallel Control Circuit
for Saturable Reactor Output Regulators in High Frequency Switched Mode
Converters, Proc.IEEE Applied Power Electronics Conference 1986 .
145. E. B. G. Nijhof, The Series Resonant Power Supply and Its Control
Circuitry, Seventh Internat.PCI Conf. and Fifth Internat. MOTORCON Conf.
on Electronic Motion Control 1983.
146. B. Carsten, Distributed Power Systems of the Future Utilizing High
Frequency Converters, Second International High Frequency Power Conversion
147. C. S. Kerfoot, et al., RF Techniques Applied to High Frequency
Converters, Second International High Frequency Power Conversion Conference
148. R. B. Ridley, et al., Multi-Loop Control for Quasi-Resonant Converters,
Second International High Frequency Powe Conversion Conference 1987.
149. M. K. Kazimierczuk and K. Puczko, Feedback Control of Zero-Voltage-Switching
Resonant DC/DC Converters, Second International High Frequency Power
Conversion Conference 1987.
150. Los Angeles Times, April 4, 1987.
151. R. R. Rice, Space Station Power System Selection, 21st Intersociety
Energy Conversion Engineering Conference 1986 Record.
152. T. Natarajan and S. R. Yadavalli, An Evaluation of Inverter Topologies
for High Power Spacecraft, 21st Intersociety Energy Conversion Engineering
Conference 1986 Record.
153. J. Hayden, Multi-Megawatt Power Distribution Considerations, 21st
Intersociety Energy Conversion Engineering Conference 1986 Record.
154. W. G. Dunbar, et al., Design and Development Issues for Multi-Megawatt
Spacecraft Power Systems, 21st Intersociety Energy Conversion Engineering
Conference 1986 Record.
155. R. Charbonnier, Rochar-Electronique, January 1954.
156. C. W. T. McLyman, Flyback Converter Magnetics Design Software,
KG Magnetics Inc., P. O. Box 3095, South Pasadena, California 91030-6095,