The invention relates to a method for statically balancing the loading of
power semiconductor switches (S.sub.1, S.sub.2, S.sub.3) in a parallel
circuit (1). To achieve this in prior art, switching instants of
individual switches (S.sub.1, S.sub.2, S.sub.3) are adapted in the case
of GTOs and current amplitudes of individual switches are adapted in the
case of IGBTs. According to the invention, a primary pattern (4) of
frame-switching pulses is predetermined for a total current (i) through
the parallel circuit (1) and a secondary pattern (51, 52, 53) comprising
more or fewer pulses than the primary pattern (4) is generated for at
least one switch (S.sub.1, S.sub.2, S.sub.3). In contrast in conventional
methods, the asynchronicity of the pulses enables a rapid redistribution
of the loading between the parallel switches (S.sub.1, S.sub.2, S.sub.3),
thus reducing or obviating the need for inductive suppressor circuits for
limiting the current. The method is compatible with methods for the
dynamic synchronization of transient switching and is suitable for
"latching" and amplitude-controlled power semiconductor switches
(S.sub.1, S.sub.2, S.sub.3). The examples relate to the addition or
omission of subordinate switching pulses during long or short
frame-switching pulses and to an active control (6) of the number of
subordinate switching pulses, depending on the loading of the switches
(S.sub.1, S.sub.2, S.sub.3).