Classifications Power semiconductor device

1 classifications

1.1 diodes
1.2 switches
1.3 amplifiers

classifications

fig. 1: power devices family, showing principal power switches.

a power device may classified 1 of following main categories (see figure 1):

a two-terminal device (e.g., diode), state dependent on external power circuit connected.
a three-terminal device (e.g., triode), state dependent on not external power circuit, signal on driving terminal (this terminal known gate or base).
a 4 terminal device (e.g. silicon controlled switch -scs). scs type of thyristor having 4 layers , 4 terminals called anode, anode gate, cathode gate , cathode. terminals connected first, second, third , fourth layer respectively.

another classification less obvious, has strong influence on device performance:

a majority carrier device (e.g., schottky diode, mosfet, etc.); uses 1 type of charge carriers.
a minority carrier device (e.g., thyristor, bipolar transistor, igbt, etc.); uses both majority , minority carriers (i.e., electrons , electron holes).

a majority carrier device faster, charge injection of minority carrier devices allows better on-state performance.

diodes

an ideal diode should have following characteristics:

when forward-biased, voltage across end terminals of diode should zero, no matter current flows through (on-state).
when reverse-biased, leakage current should zero, no matter voltage (off-state).
the transition (or commutation) between on-state , off-state should instantaneous.

in reality, design of diode trade-off between performance in on-state, off-state, , commutation. indeed, same area of device must sustain blocking voltage in off-state , allow current flow in on-state; requirements 2 states opposite, diode has either optimised 1 of them, or time must allowed switch 1 state other (i.e., commutation speed must reduced).

these trade-offs same power devices; instance, schottky diode has excellent switching speed , on-state performance, high level of leakage current in off-state. on other hand, pin diode commercially available in different commutation speeds (what called fast , ultrafast rectifiers), increase in speed associated lower performance in on-state.

switches

fig.2 : current/voltage/switching frequency domains of main power electronics switches.

the trade-offs between voltage, current, , frequency ratings exist switch. in fact, power semiconductor relies on pin diode structure in order sustain voltage; can seen in figure 2. power mosfet has advantages of majority carrier device, can achieve high operating frequency, cannot used high voltages; physical limit, no improvement expected in design of silicon mosfet concerning maximum voltage ratings. however, excellent performance in low voltage applications make device of choice (actually choice, currently) applications voltages below 200 v. placing several devices in parallel, possible increase current rating of switch. mosfet particularly suited configuration, because positive thermal coefficient of resistance tends result in balance of current between individual devices.

the igbt recent component, performance improves regularly technology evolves. has replaced bipolar transistor in power applications; power module available in several igbt devices connected in parallel, making attractive power levels several megawatts, pushes further limit @ thyristors , gtos become option. basically, igbt bipolar transistor driven power mosfet; has advantages of being minority carrier device (good performance in on-state, high voltage devices), high input impedance of mosfet (it can driven on or off low amount of power).

the major limitation of igbt low voltage applications high voltage drop exhibits in on-state (2-to-4 v). compared mosfet, operating frequency of igbt relatively low (usually not higher 50 khz), because of problem during turn-off known current-tail: slow decay of conduction current during turn-off results slow recombination of large number of carriers flood thick drift region of igbt during conduction. net result turn-off switching loss of igbt considerably higher turn-on loss. generally, in datasheets, turn-off energy mentioned measured parameter; number has multiplied switching frequency of intended application in order estimate turn-off loss.

at high power levels, thyristor-based device (e.g., scr, gto, mct, etc.) still choice. device can turned on pulse provided driving circuit, cannot turned off removing pulse. thyristor turns off no more current flows through it; happens automatically in alternating current system on each cycle, or requires circuit means divert current around device. both mcts , gtos have been developed overcome limitation, , used in power distribution applications.

a few applications of power semiconductors in switch mode include lamp dimmers, switch mode power supplies, induction cookers, automotive ignition systems, , ac , dc electric motor drives of sizes.

amplifiers

amplifiers operate in active region, both device current , voltage non-zero. consequently power continually dissipated , design dominated need remove excess heat semiconductor device. power amplifier devices can recognized heat sink used mount devices. multiple types of power semiconductor amplifier device exist, such bipolar junction transistor, vertical mos field effect transistor, , others. power levels individual amplifier devices range hundreds of watts, , frequency limits range lower microwave bands. complete audio power amplifier, 2 channels , power rating on order of tens of watts, can put small integrated circuit package, needing few external passive components function.

another important application active-mode amplifiers in linear regulated power supplies, when amplifier device used voltage regulator maintain load voltage @ desired setting. while such power supply may less energy efficient switched mode power supply, simplicity of application makes them popular, in current ranges 1 amp.