2.7 IGBT Characteristics

For generating an alternating voltage (650V, up to 40A peak) at 4 - 20kHz, an electronic power switching device is needed.

Table 2 compares the characteristics of electronic power switching devices, capable of switching at frequencies of several kHz.

	POWER MOSFETs	IGBTs	Bipolars	Darlingtons
Type of Drive	Voltage	Voltage	Current	Current
Drive Power	Minimal	Minimal	Large	Medium
Drive Complexity	Simple	Simple	High Large positive and negative currents are required	Medium
Current Density For Given Voltage Drop	High at low voltages Low at high voltages	Very High Small trade-off with switching speed	Medium Severe trade-off with switching speed	Low
Switching Losses	Very Low	Low to Medium depending on trade-off with conduction losses	Medium to High depending on trade-off with conduction losses	High
Cost / kW (Power - Devices)	High	Low	Medium	High

Table 2.2: Comparison of power switching devices

The best choice (cost, complexity) is an IGBT (Insulated Gate Bipolar Transistor). Its characteristics are further described in [IR-AN-983].

Figure 2.15: IGBT: cross-section, symbol and equivalent