Power Semiconductors Flashcards
What does IGBT stand for?
Insulated gate bipolar transistor
Draw the circit symbol for and IGBT, as well as its equivalent circuit.
What are the 3 key features of an IGBT?
- No intrinsic anti-parallel diode
- No change in conduction losses with temperature
- Switching losses increases with temperature
What voltage and frequency ranges should an IGBT be used for?
Medium frequency (approx. 100kHz)
Medium voltage (0.1-10V)
What does BJT stand for?
Bipolar junction transistor
Draw an NPN BJT
Draw a PNP BJT
When does an NPN BJT conduct?
When current is flowing into its base terminal
In order for a BJT to conduct, what is required of the base terminal?
That it takes a continuous current
Draw a thyristor
Draw the equivalent circuit for a thyristor
List the key features of a thyristor
- Slow switching speed
- di/dt needs limiting to reduce instantaneous power dissipation and current crowding
- dv/dt needs limiting to prevent injection of current from stray capacitance (causes false triggering)
What applications is a thyristor most suitable for?
High-voltage (+10V)
Low frequency (<100Hz)
What does MOSFET stand for?
Metal-Oxide-Semiconductor Field-Effect Transistor
What is the defining feature of a source terminal?
Primary charge carriers enter the semiconductor at it
What are the four types of MOSFET?
- N-Channel Enhancement-mode
- N-Channel Depletion-mode
- P-Channel Enhancement-mode
- P-Channel Depletion-mode
What does “enhancement-mode” mean with regards to a MOSFET?
It means that no conducting channel is present across the source-drain terminals of the MOSFET until a voltage is applied across the gate-source junction
What does “depletion-mode” mean with regards to a MOSFET?
A conducting channel exists in the MOSFETs default state: applying a gate-source voltage removes this channel
What are the primary charge carriers in an N-channel MOSFET?
Electrons
What are the primary charge carriers in P-channel MOSFETs?
Holes
Why is it important to energise the control circuitry for D-mode MOSFETs before their attached power circuitry?
Because D-mode MOSFETs default to the ON-state - in order to have control of the power system as soon as it becomes live, it must be possible to drive the gate OFF before any voltage exists between the drain-source terminals.
Draw and label the 4 types of MOSFET
What applications are MOSFETs most suitable for?
High frequency ( > 100kHz)
Low voltage ( < 0.1V)
List the key features of a MOSFET
- Voltage-driven (draws no steady-state current and therefore does not incur gate conduction losses)
- A transient capacitive current exists whilst it is switching
- Source-drain resistance is temperature-dependent
- Low switching losses
- Source-drain resistance is proportional to the max. drain-source voltage to the power of 2.6
