Component Characteristics and Comparison

What factors are compared when choosing a power electronic switch?

Voltage rating, current rating, switching speed, control type, and cooling needs.

Compare BJT and MOSFET.

BJT: current-controlled, low input impedance, slower. MOSFET: voltage-controlled, high input impedance, faster.

Compare MOSFET and IGBT.

MOSFET: fast, lower voltage. IGBT: slower, higher voltage/current capability.

Compare SCR and GTO in control.

SCR turns off only when current < IH; GTO turns off with a negative gate pulse.

Compare MOSFET and IGBT in frequency.

MOSFETs suit higher frequency; IGBTs suit lower frequency but higher voltage.

Choose a switch for 3 kV, 2 kA DC with full control.

Use an IGBT or GTO based on required speed; both are fully controllable high-power devices.

What is second breakdown?

Second breakdown is a catastrophic localized failure in BJTs caused by the combined effects of high voltage, high current, and localized heating, leading to thermal runaway and permanent device damage. Short between collector and emitter. Not present in MOSFETs

Voltage- vs current-controlled devices?

Voltage-controlled: MOSFET, IGBT. Current-controlled: BJT, SCR.

How are comparison tables presented?

Columns list device types, rows list ratings, speed, control signal, and typical applications.

Power Diode - Semiconductor Diode

• Operating frequency: 50-60 Hz

• Control: None (uncontrolled, conducts when forward-biased)

• Max voltage/current: Up to several kV / several kA

• Second breakdown: No

• Parallel use: Possible with current-sharing resistors

• Forward voltage drop: 0.7-1.1 V (silicon)

• Tail current: None

• Advantages: Simple, rugged, inexpensive

• Disadvantages: No control, reverse-recovery losses for standard diodes

• Applications: Rectifiers, freewheeling or flyback paths, snubbers, PV blocking diodes, clamping"

Thyristor - Silicon Controlled Rectifier (SCR)

• Operating frequency: 400-500 Hz

• Control: Current-controlled (single gate pulse to turn on/ turn-off by reducing anode current below holding current Ih or by commutation)

• Max voltage/current: Up to about 10 kV / 5000 A

• Second breakdown: No (device latches)

• Parallel use: Difficult - needs careful current sharing

• Forward voltage drop: Typically 1-2 V

• Tail current: Present at turn-off due to stored charge

• Advantages: Very high voltage and current capability, low conduction loss

• Disadvantages: Slow switching, half-controlled (cannot turn off via gate), needs snubber/commutation

• Applications: Controlled rectifiers, AC voltage controllers, soft starters, heater control, large DC drives"

GTO - Gate Turn-Off Thyristor

• Operating frequency: Up to about 1 kHz

• Control: Fully controlled via gate (positive pulse to turn on, large negative gate current to turn off)

• Max voltage/current: Up to 4.5 kV / 3 kA

• Second breakdown: No (thyristor-type)

• Parallel use: Limited, requires balancing networks

• Forward voltage drop: About 1-3 V

• Tail current: Present at turn-off

• Advantages: No external commutation circuit needed, high power capability

• Disadvantages: Requires large gate drive power, slower than transistor switches

• Applications: High-power inverters and choppers, DC motor drives, traction converters"

MCT - MOS-Controlled Thyristor

• Operating frequency: Tens of kHz

• Control: Voltage-controlled MOS gate provides turn-on and turn-off

• Max voltage/current: Roughly 1-2 kV / 100-500 A (device dependent)

• Second breakdown: No (thyristor-type)

• Parallel use: Limited, needs sharing components

• Forward voltage drop: Low

• Tail current: Small compared to GTO

• Advantages: High input impedance, lower drive power than GTO, faster switching than SCR/GTO

• Disadvantages: dv/dt sensitive, technology less common, complex structure

• Applications: High-frequency converters, UPS, variable-speed drives, SMPS where fully controlled thyristor behavior is desired"

SITH - Static Induction Thyristor

• Operating frequency: Up to hundreds of kHz

• Control: Voltage-controlled by gate potential (field-controlled)

• Max voltage/current: Up to 5 kV / 5 kA (technology dependent)

• Second breakdown: No (thyristor-type)

• Parallel use: Possible with care

• Forward voltage drop: Very low

• Tail current: Very small

• Advantages: Extremely fast switching, low switching loss, high efficiency

• Disadvantages: Expensive and complex, limited availability

• Applications: RF and pulse power, induction heating, high-frequency inverters"

BJT - Bipolar Junction Transistor

• Operating frequency: Up to about 10 kHz in power switching

• Control: Current-controlled (requires continuous base current)

• Max voltage/current: Up to 1200 V / 500 A (power BJTs)

• Second breakdown: Yes (critical limitation)

• Parallel use: Difficult due to negative temperature coefficient, needs emitter resistors

• Forward voltage drop: Vce(sat) typically 0.8-1.5 V

• Tail current: Moderate storage tail at turn-off

• Advantages: Low saturation voltage, good current capability

• Disadvantages: Continuous drive power, slower switching, thermal runaway risk

• Applications: Older inverters and choppers, linear amplifiers, some SMPS stages"

MOSFET - Metal Oxide Semiconductor Field Effect Transistor

• Operating frequency: Greater than 1 MHz possible

• Control: Voltage-controlled, very low steady-state gate current

• Max voltage/current: Up to 600 V / 40 A (higher current at lower voltages common)

• Second breakdown: None

• Parallel use: Easy due to positive temperature coefficient of Rds(on)

• Forward voltage drop: Low, behaves as resistive (depends on Rds(on))

• Tail current: None

• Advantages: Very fast switching, low drive power, high efficiency at low-to-medium voltage

• Disadvantages: Higher conduction loss at high voltage due to Rds(on), body diode reverse recovery

• Applications: DC-DC converters, SMPS primary and synchronous rectification, low-voltage motor drives, high-frequency PWM inverters"

IGBT - Insulated Gate Bipolar Transistor

• Operating frequency: Up to 20 kHz (typical power range)

• Control: Voltage-controlled (MOS gate)

• Max voltage/current: Up to 1.2 kV / 400 A per device (higher in modules)

• Second breakdown: None (rugged SOA compared to BJT)

• Parallel use: Easier than BJT, still requires sharing components

• Forward voltage drop: 2-4 V (approximately)

• Tail current: Present at turn-off due to stored charge

• Advantages: High current density, low drive power, good conduction at medium-high voltage

• Disadvantages: Slower than MOSFET, switching loss from tail current

• Applications: Medium and high-power inverters, motor drives, EV traction, UPS, welders, induction heating"