Hitachi IGBT Module Application Manual
5.3.2 Gate Electric Charge Characteristics
Figure 26 shows the relation between gate electric charge ( Q
) and gate-emitter voltage and segments
the gate electric charge characteristics into three regions ( labeled A, B, and C ).
Figure 26. Example of Gate Electric Charge Characteristics
Region A clearly shows that the electric charge ( Q
) is determined by gate
voltage and input capacitance of IGBT module during the condition that collector-
emitter voltage is higher than the output voltage of the gate driver.
Region B shows the negative reverse transfer ("mirror effect") of reverse transfer
capacitance ( C
). Here, gate-emitter voltage cannot vary, but collector-emitter
voltage does and, as a consequence, gate current remains constant with value
determined by the output voltage of the gate driver and gate resistance.
Region C shows the situation where the collector-emitter voltage approaches the
saturation voltage while the input capacitance and maximum value of reverse
transfer capacitance are connected in parallel.
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