A global and real-time control with embedded hardware artificial neural network (ANN) for imbalance current suppression of parallel connected IGBTs is firstly proposed in this paper. This method focuses on control strategy and control execution. The former one is realized by porting the ANN based PID (ANN-PID) strategy in the control loop to yield the real-time and adaptive characteristics without IGBT quantity limitation. The latter one is realized by designing the IGBT gate quantity of charge regulator (GQR) to execute the command from ANN-PID controller. The evaluation of ANN-PID algorithm results 0.023% mean error in IGBT current control that reveals the feasibility of the proposed method. A full prototype with FPGA based hardware accelerator for ANN-PID computing, including the designed GQR circuit, has been built for realization and qualification in a buck converter with parallel connected IGBTs. The experimental results show that the performance of proposed method in imbalance current suppression is improved about 3.5 to 5.5 times as the load increase from low to high with the advantage of immunity to load change and the current imbalance can be suppressed within 4%.

In this letter, 650 V generation I (thin) and generation II (ultrathin) super-junction insulated gate bipolar transistors (SJ-IGBT) based on deep trench etching and refilling processes are manufactured. It is worth mentioning that generation II is fabricated using 45 $ {\mu }\text{m}$ ultrathin wafer technology. Due to extra parasitic BJTs, both the thin and ultrathin SJ-IGBT have a larger base amplification factor, that the current density capability exceeds 650 A/cm ² . Compared with thin SJ-IGBT both at 650 A/cm ² and at room temperature, the on- state voltage of the ultrathin SJ-IGBT could be decreased by about 160 mV, turn-off energy loss could be decreased by 22%. Furthermore, the ultrathin SJ-IGBT maintains a robust short circuit capability of no less than $10~ {\mu }\text{s}$ under 400 V DC bus voltage.

China′s bid for the 2022 Winter Olympic Games will promote rapid development of domestic ski tourism. More than 10 provinces in the northern China list ski tourism as a new source of growth in the tourism industry. Formulating a scientific evaluation system is an important foundation for ski resort development. By referring to the conditions of existing international ski resorts, a comprehensive index system for evaluating ski resort development was developed based on natural factors, human factors, athletic sports, and popular ski tourism. The system was composed of one target layer, two indices, seven sub-indices and twenty-five basic indices. Based on data collected during a field investigation in 2012 and on a statistical model, the development conditions of the following ski resorts were quantified: Yabuli Ski Resort in Heilongjiang Province and Beidahu Ski Resort in Jilin Province in Northeast China, Wanlong Ski Resort in Hebei Province and Nanshan Ski Resort in Beijing in the northern China, and Silk Road International Ski Resort in Uygur Autonomous Region of Xinjiang in the northwestern China. The resulting index values of development conditions at Beidahu, Yabuli, Wanlong, Nanshan, and Silk Road International Ski Resorts were 0.304, 0.278, 0.270, 0.214, and–0.025, respectively. Various natural and human factors exert positive and negative effects on the development potential of ski resorts. The development conditions of the five ski resorts were inferior to those of first-class international resorts. Therefore, the development conditions of the five ski resorts should be improved with future construction.

The PNP bipolar junction transistors (BJTs) are susceptible to surface recombination in both the emitter–base depletion and neutral base regions when their passivation oxide layers are damaged by ionization irradiation, leading to an increase of base current. The previous model of excess base current proposed in 2015 omits the damage in the neutral base, and the impact of oxide charges, which results in an underestimation of bias sensitivity of excess base current. This work presents a physics-based improvement of the previous model, and it provides a much better fit to the experimental data for the bias dependence of excess base current for the 2N2907 vertical and gate controlled lateral PNP BJTs subjected to γ-ray irradiation. The model suggests that the damage in the neutral base can be significant for a lateral PNP with wide base, operated at high bias voltage, and exposed to a low dose. Furthermore, the model provides a simple and practical method to separate and estimate the total oxide charge and increased interface trap densities from excess base current readings on irradiated PNP BJTs. The extracted values of interface trap densities show less dependence on E-B bias voltage than with previous models, which provides evidence of its improved precision.

Drift BJTs, characterized by a graded doping profile in the base region, are susceptible to the recombination in both the base and emitter-base depletion regions when they are damaged by atomic displacement, leading to gain degradation. Previous model of the gain degradation of BJTs (i.e., Messenger-Spratt model) adopts the assumptions of the neutral base and ideal depletion, which are not valid for the drift BJTs. A drift BJT has an extra build-in electric field which breaks the neutral base condition, and the excess recombination rate is reduced and depends on the drift parameters. Furthermore, the non-ideal depletion effects can suppress the excess recombination in the junction region, which will also reduce the susceptibility of the displacement damage. This work presents a physics-based improvement of the previous model, and provides a much better fit to the experimental data of the 3CK3B drift BJTs subjected to Deuterium-Tritium 14 MeV neutron irradiation. The new model also suggests that the ideal factor of excess base current induced by displacement damage approaches to 1.33 for the BJTs technologies with narrow base or operated under low bias conditions.