Page 107 - Electrical Engineering Dictionary

Buck converter.

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