Buck converter.
Buck-boost converter.
BTDF
See
bidirectional transmission dis-
tribution function
.
BTMA
See
busy tone multiple access
.
See also
ISMA
.
bubble chamber
an instrument for ren-
dering visible the tracks of ionizing particles.
It is characterized by a vessel filled with a su-
perheated transparent liquid, commonly hy-
drogen or deuterium. The passage of an ion-
izing particle through this liquid is marked by
the appearance of a series of bubbles along
the particle trajectory. If the liquid is sub-
jected to a magnetic field, as is usually the
case, the charged particle trajectories will be
curved, the curvature providing information
about the particles’ charge and momentum.
buck converter
a transistor is switched
by PWM trigger pulses and a diode provides
a current continuation path when the transis-
tor is off, thus the input voltage is chopped.
A lowpass LC filter is used to attenuate the
switching ripple at the output. The input cur-
rent to a basic buck converter is discontinu-
ous; therefore, in many applications an LC
prefilter is applied to reduce EMI. The out-
put voltage
v
o
is related to the input volt-
age
v
i
by
v
o
= v
i
d and it can be controlled
by varying the duty ratio
d. Isolated version
of a buck converter include forward, push-
pull, halfbridge, and bridge converters. Also
called chopper or step-down converter.
buck-boost converter
See
buck-boost
transformer
.
buck-boost transformer
a special pur-
pose 2- or 4-coil transformer used to produce
modest increases or decreases in the utiliza-
tion voltage at a load site. The low-voltage
coil(s), which typically have rated voltages
of 5% to 15% of the high-voltage coils, and
in use, the high- and low-voltage, coils, are
connected in series to produce an autotrans-
former arrangement. If primary voltage is ap-
plied to the high voltage coil and load voltage
is taken from the series coil combination, the
low-voltage coil adds to, or boosts, the load
utilization voltage. Conversely, reductions
in load utilization voltage occur when these
primary and secondary connections are re-
versed causing the low-voltage coil to buck
the supply voltage. A typical 4-coil buck-
boost transformer would have two 120 V pri-
mary coils and two 12 V secondary coils,
which could be used to produce voltage ra-
tios of (120/132), (120/144), (240/252), and
(240/264).
In a basic buck-boost converter, the induc-
tor accumulates energy from the input volt-
age source when the transistor is on and re-
leases energy to the output when the transis-
tor is off. It can be viewed as a buck converter
followed by a boost converter with topologic
simplification. In a buck-boost converter, the
output voltage
v
o
is related to the input volt-
c
2000 by CRC Press LLC