Method for operating a parallel arrangement of semiconductor power switches

A method for operating a parallel circuit of semiconductor power switches, wherein the parallel circuit comprises a power connector to feed current to and a power connector to collect current from a load, wherein a master control signal with a primary pattern of frame switching pulses is provided to the parallel circuit for a total current through the parallel circuit, wherein further the semiconductor power switches are controllable with individual control signals, said method comprising the steps of

• a) generating at least one secondary pattern of slave switching pulses for the individual control signal of at least one semiconductor power switch,
• b) using, at least temporarily, during a number of frame switching pulses in the primary pattern, a different number of slave switching pulses in the secondary pattern is for relieving the semiconductor power switch of the parallel circuit in a conductive state, and
• c) generating, at least temporarily during individual frame switching pulses, several slave switching pulses in the secondary pattern,
• wherein a number of slave switching pulses in the secondary pattern is regulated in response to a load of the corresponding semiconductor power switch of the parallel circuit, an actual load value of the semiconductor power switch is measured, and a number of slave switching pulses per frame switching pulse is increased or decreased if the actual load value is exceeding a desired load value,
• wherein a time that a given semiconductor power switch is switched-on is decreased with increasing load of the given semi-conductor power switch.

A method for operating a parallel circuit of semiconductor power switches, wherein the parallel circuit comprises a power connector to feed current to and a power connector to collect current from a load, wherein a master control signal with a primary pattern of frame switching pulses is provided to the parallel circuit for a total current through the parallel circuit, wherein further the semiconductor power switches are controllable with individual control signals, said method comprising the steps of

• a) generating at least one secondary pattern of slave switching pulses for the individual control signal of at least one semiconductor power switch,
• b) using, at least temporarily, during a number of frame switching pulses in the primary pattern, a different number of slave switching pulses in the secondary pattern is for relieving the semiconductor power switch of the parallel circuit in a conductive state, and
• c) generating, at least temporarily during individual frame switching pulses, several slave switching pulses in the secondary pattern,
• wherein a number of slave switching pulses in the secondary pattern is regulated in response to a load of the corresponding semiconductor power switch of the parallel circuit, an actual load value of the semiconductor power switch is measured, and a number of slave switching pulses per frame switching pulse is increased or decreased if the actual load value is exceeding a desired load value,
• wherein a time that a given semiconductor power switch is switched-on is decreased with increasing load of the given semi-conductor power switch,
• wherein a number of the slave switching pulses of all secondary patterns is concurrently regulated by a compensation regulator for thermal symmetrisation of the parallel circuit.