Page 436 - Power Electronics Handbook

Glossary of terms 425
Feedback: The process of sampling the load voltage or current and feeding
this back to the control device to enable exact regulation. Also the process
of feeding back energy from the load to the supply.
FET: Field effect transistor. Terminology applied to unipolar transistors. See
also JFET and MOSFET.
Firing angle: See Delay angle.
Firing circuit: The circuit which provides current and voltage to turn on a
power semiconductor, usually a thyristor or a triac. This is also called a
gating circuit or trigger circuit.
Flip chip: Semiconductor chip which has bumps on its surface so that it can
be put face down and connected onto the substrate tracks or package
leads.
Forced commutation: The use of external circuitry, such as a charged
capacitor, to turn off a power semiconductor switch. This is primarily used
in thyristor choppers and inverters. (See also Natural commutation.)
Free-wheeling diode: The diode which is placed across the load to carry the
load current, when the power semiconductor switch turns off. This is also
referred to as a commutation diode since it assists in commutation, or
turn-off, of the power switch.
Full wave: An a.c. to d.c. converter in which the a.c. input current flows in
both directions.
Fully controlled: An ax. to d.c. converter in which the power can flow in
either direction, this usually being achieved by the use of controllable
devices, such as thyristors, in all the converter arms.
Gating circuit: See Firing circuit.
GTO: Gate turn off switch. A four layer semiconductor which can be turned
on and off by a gate signal.
Hdfeoatrdled: An a.c. to d.c. converter in which the power can only flow
from the a.c. supply to the d.c. load. This is usually caused by converters in
which only half the components are controllable (thyristors), or where a
free-wheeling diode is placed across the load.
Half wave: An a.c. to d.c. converter in which the current in the a.c. line
flows in one direction only.
Holding current: The value of the current flowing through a semiconductor
switch below which it will return to its off state.
IGBT: Insulated gate bipolar transistor. A hybrid power semiconductor
device which combines the low saturation voltage of a bipolar transistor with
the low input current requirements of a unipolar transistor.
Integral cycle control: A method for regulating the a.c. power to the load
by controlling the number of whole or half cycles of the supply. This is also
known as burst firing, and uses zero crossing control techniques.
Inverse parallel: See Anti-parallel.