WESTCODE An IXYS Company
Fast Symmetrical Gate Turn-Off Thyristor type H0500KC25#
Diagram 11, Turn-off parameter definitions.
In addition to the turn-off figures given in characteristic data, the curves of figures 10, 11 & 12 give the
relationship of IGQ QGQ and tgq to turn-off current (ITGQ) and diGQ/dt. Only typical values of IGQ are given due
to a great dependence upon the gate circuit impedance, which is a function of gate drive design not the
device. The tgq is also, to a lesser extent, affected by circuit impedance and as such the maximum figures
given in data assume a good low impedance circuit design. The curves of figures 17 & 18 give the tail time
and minimum off time to re-fire device as a function of turn-off current. The minimum off time to re-fire the
device is distinct from tgw, the gate off time given in characteristics. The GTO thyristor may be safely re-
triggered when a small amount of tail current is still flowing. In contrast, the gate circuit must remain low
impedance until the tail current has fallen to zero or below a level which the higher impedance VGR circuit
can sink without being pulled down below –2 Volts. If the gate circuit is to be switched to a higher
impedance before the tail current has reached zero then the requirements of diagram 12 must be applied.
(VGR - itail R)>2V
The figure tgw, as given in the characteristic data, is the maximum time required for the tail current to
decay to zero. The figure is applicable under all normal operating conditions for the device; provided
suitable gate drive is employed. At lower turn-off current, or with special gate drive considerations, this
time may be reduced (each case needs to be considered individually).Typical turn-off losses are given in
the curves of figures 13 & 14, the integration period for the losses is nominally taken to the end of the tail
time (Itail<1A) i.e. :-
Eoff = ∫ iv.dt.
Data Sheet. Type H0500KC25# Issue 2
Page 8 of 15