Patent ID: 7035064

Claim:
A circuit arrangement operable under control of a master control system to provide adaptive overload protection for power semiconductor switches with anti-parallel free-running diodes in a power supply system, comprising: sensors for continuously monitoring at least two directly measurable operating parameters of at least one of said semiconductor switches and said power supply system; a data storage memory for storing correction factors in the form of characteristic curve fields and for storing baseline power loss values measured in a defined operating mode of the power supply system; a means for determining applicable correction factors based on current values of said directly measurable operating parameters and based on said characteristic curve fields; a multiplication stage for multiplying the baseline power losses with the applicable correction factors to determine an amount of power lost in the semiconductor switches; a means for determining a junction temperature of the semiconductor switches based on said amount of lost power, using a theoretical thermal model of said semiconductor switches; a comparator means for comparing said junction temperature to a maximum permissible temperature; and a means for transmitting a result of said comparison to the master control system so that operating mode parameters of the power supply system can be adjusted and an emergency shut-down can be prevented in a case where said comparator means indicates a thermal overload condition.