International audienceIn this paper, a 2.5-kW 330–410-V/14-V, 250-kHz dc/dc converter prototype is developed targeted for electric ve-hicle/hybrid vehicle applications. Benefiting from numerous ad-vantages brought by the LLC resonant topology, this converter is able to perform high efficiency, high power density, and low EMI. To arrange high-output current, this paper proposes a parallel-connected LLC structure with developed novel double-loop control to realize an equal current distribution and an overall efficiency improvement. Considering the LLC cell's dimensioning, this paper establishes a more precise model by taking the secondary leak-age inductance into consideration. System amelioration and design considerations of the developed LLC are also presented in this pa-per. A special transformer is presented, and various types of power losses are quantified to improve its efficiency. This converter also implements synchronous rectification, power semiconductor mod-ule, and an air-cooling system. The power conversion performance of this prototype is measured and the developed prototype attains a peak efficiency of 95% and efficiency is higher than 94% from 500 W to 2 kW, with a power density of 1 W/cm 3 . Finally, the EMC results of this prototype are also measured and presented

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Testing at system level is evaluated by measuring the sensitivity of point-of-load (PoL) converter parameters, submitted to total ionizing dose (TID) irradiations, at both system and component levels. Testing at system level shows that the complete system can be fully functional at the TID level more than two times higher than the qualification level obtained using a standard-based component-level approach. Analysis of the failure processes shows that the TID tolerance during testing at system level is increased due to internal compensation in the system. Finally, advantages and shortcomings of the testing at system level are discussed.

Power cycling of the Point-of-Load converter is observed during system level heavy ions tests. This event has low cross section and is observed for reduced supply voltage of device under test. Laser tests are used to reproduce this effect and show that it might be due to propagation of single event transients from the voltage reference to operational amplifier being part of the undervoltage protection circuit. Laser tests show that propagating transients are the ones with high enough positive peak and insignificant negative peak value whereas some transients with bigger maximum and/or peak to peak value do not propagate. SPICE simulation shows that in operational amplifier with low voltage difference between V+ and V-, there is difference in propagation of unipolar and bipolar transients from input to output of the amplifier. Analysis of the voltage controlled current source in the amplifier explains also difference in propagation of bipolar transients with negative peak followed by positive peak and with positive peak followed by negative peak.