THYRISTORS Flashcards
class of semiconductor devices characterized by 4-layers of alternating p and n materials. Four-layer devices act as either open or closed switches.
-THYRISTORS
It is a rectifier constructed of silicon material with a third terminal for control purposes.
-SILICON CONTROLLED RECTIFIER
resistance is typically 100 kOhms or more.
-REVERSE
resistance of the SCR is typically 0.01 to 0.1 ohm.
-DYNAMIC
SCR can be turned on by exceeding the forward breakover voltage or
-GATE CURRENT
Turning off SCR
- Anode current interruption
- Forced commutation
times of of SCRs are typically 0.1 to 1 microsecond.
-TURN ON
times of SCRs are typically 5 to 30 microsecond.
-TURN OFF
is that voltage above which the SCR enters the conduction region.
-FORWARD BREAKOVER VOLTAGE
is the value of gate current necessary to switch the SCR from the forward-blocking region to the forward conduction region under specified conditions.
-GATE TRIGGER CURRENT
is that value of current below which the SCR switches from the conduction state to the forward blocking region under stated conditions.
-HOLDING CURRENT
are the regions corresponding to the open circuit condition for the controlled rectifier which block the flow of charge (current) from anode to cathode.
-FORWARD AND REVERSE BLOCKING
is equivalent to the Zener or avalanche region of the fundamental two-layer semiconductor diode.
-REVERSE BREAKDOWN VOLTAGE
The characteristics of the device are essentially the same as those for the SCR.
-SILICON CONTROLLED SWITCH
can be used to turn the device either on or off.
-ANODE GATE CONNECTION
a negative pulse must be applied to the anode gate terminal.
-TURN ON THE DEVICE
while a positive pulse is required to
-TURN OFF THE DEVICE
An advantage of the SCS over a corresponding SCR is the
-REDUCED TURN OFF TIME
Turn off time is typically within the range 1 to 10 microseconds for the
-SILICON CONTROLLED SWITCH
Turn off time is typically 5 to 30 microseconds for the
-SILICON CONTROLLED RECTIFIER
The device is in the off state unit until the breakover voltage is reached, at which time avalance conditions develop and the device turnd on
Shockley diode
A gate terminal for controlling the the the turn on conditions of the bilateral device in either direction
Triac
Three terminal device with only one pn junction
Unijunction transistor
Four layer pnpn device with a gate connected directly to the sandwiched n type layer
Programmable unijunction transistor
Converts ac power to dc power which is known rectification
Controlled rectifiers
Converts a fixed voltage ac to a variable voltage dc. It is used primarily to control the speed of dc motors
Ac to dc controlled rectifier
Converts a fixed voltage dc a variable dc.
Dc to dc chopper
Converts a voltage and fixed frequency ac to a variable voltage and variable (lower) frequency
Dc to ac inverter
A hybrid power semiconductor device which combines the attributes of the bjt and the MOSFET. Has high input impedance and low on state voltage drop
Insulated gate bipolar transistor
A thyristor which can be turned on and off by a built in mosfet type gate
MOS controlled thyristor
Converts ac to dc power, which is known as rectification
Controlled rectifiers
Directly converts a fixed-voltage dc supply to a variable voltage dc supply. Can be used to control the speed of dc motor
Chopper
Also known as buck converter. Output voltage is lower than input voltage
Step down chopper
Also known as boost converter. Output voltage is higher than input voltage
Step up chopper
Also known as buck-boost converter
Step-down and step-up chopper
The fundamental behavior of photoelectric devices was introduced earlier with the description of the photodiode
Photo transistors
Package that contains both an infrared LED and photo detector such as a silicon diode
Opto isolators
