AN4544 datasheet(22/35 Pages) STMICROELECTRONICS

22 / 35 page

Datasheet explanation

AN4544

22/35

DocID026535 Rev 1

2.6.1

Input, output and reverse transfer capacitances (Cies), (Coes) and (Cres)

IGBT dynamical characteristics are influenced by parasitic capacitances. The typical values

of the capacitance are measured under specific conditions: VCE = 25 V, f = 1 MHz and

VGE = 0 V, and its decrease is inversely proportional to the biased voltage introduced in the

collector-to-emitter.

Figure 18. IGBT section and equivalent model with parasitic capacitances between

terminals

2.6.2

Input capacitance (Cies)

This is the input capacitance measured between the gate and emitter terminals with the

collector shorted to the emitter for AC signals. Cies is given by the gate to collector

capacitance (CGC) in parallel with the gate to emitter capacitance (CGE):

Equation 9

The input capacitance has to be charged to the threshold voltage before the device begins

to turn on, and discharged to the plateau voltage before the device begins to turn off.

Therefore both the impedance of the drive circuitry and Cies, have a direct relationship to the

turn on and turn off delays.

2.6.3

Output capacitance (Coes)

This is the output capacitance measured between the collector and emitter terminals with

the gate shorted to the emitter for AC voltages. Coes is given by the collector-to-emitter

capacitance (CCE) in parallel with the gate to collector capacitance (CGC):

Equation 10

For soft switching applications, Coes can affect the resonance of the circuit.

ies

oes

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