Effects of Floating Ring Bearing Manufacturing Tolerance Clearances on the Dynamic Characteristics for Turbocharger

The inner and outer oil film dynamic characteristic coefficients of floating ring bearings（FRBs） change due to the manufacturing tolerance of the floating ring, journal and intermediate, which leads to high-speed turbocharger＇s vibration too large and even causes nonlinear vibration accident. However, the investigation of floating ring bearing manufacturing tolerance clearance on the rotordynamic characteristics is less at present. In order to study the influence law of inner and outer clearance on turbocharger vibration, the rotor dynamic motion equations of turbocharger supported in FRBs are derived by analyzing the size relations between floating ring, journal and intermediate for the inner and outer oil film clearances, the time transient response analysis for combination of FRBs clearance are developed. A realistic turbocharger is taken as a research object, the FE model of the turbocharger with FRBs is modeled. Under the conditions of four kinds of limit state bearing clearances for inner and outer oil film, the nonlinear transient analyses are performed based on the established FE dynamic models of the nonlinear rotor-FRBs system applied incentive combinations of gravity and unbalance force, respectively. From the waterfall, the simulation results show that the speed for the appearance of fractional frequency is not identical and the amplitude magnitude is different under the four kinds of bearing manufacturing tolerance limit clearances, and fractional frequency does not appear in the turbocharger and the amplitude is minimum under the ODMin/IDMax bearing manufacturing tolerance clearances. The turbocharger vibration is reduced by controlling the manufacturing tolerance clearance combinations of FRBs, which is helpful for the dynamic design and production-manufacturing of high-speed turbocharger.

β-Ga_(2)O_(3) junction barrier Schottky diode with NiO p-well floating field rings

Recently,β-Ga_(2)O_(3),an ultra-wide bandgap semiconductor,has shown great potential to be used in power devices blessed with its unique material properties.For instance,the measured average critical field of the vertical Schottky barrier diode(SBD)based onβ-Ga_(2)O_(3) has reached 5.45 MV/cm,and no device in any material has measured a greater before.However,the high electric field of theβ-Ga_(2)O_(3) SBD makes it challenging to manage the electric field distribution and leakage current.Here,we showβ-Ga_(2)O_(3) junction barrier Schottky diode with NiO p-well floating field rings(FFRs).For the central anode,we filled a circular trench array with NiO to reduce the surface field under the Schottky contact between them to reduce the leakage current of the device.For the anode edge,experimental results have demonstrated that the produced NiO/β-Ga_(2)O_(3) heterojunction FFRs enable the spreading of the depletion region,thereby mitigating the crowding effect of electric fields at the anode edge.Additionally,simulation results indicated that the p-NiO field plate structure designed at the edges of the rings and central anode can further reduce the electric field.This work verified the feasibility of the heterojunction FFRs inβ-Ga_(2)O_(3) devices based on the experimental findings and provided ideas for managing the electric field ofβ-Ga_(2)O_(3) SBD.

Low on-resistance 1.2 kV 4H-SiC power MOSFET with Ron, sp of 3.4 mΩ·cm^2

A 4H-SiC power MOSFET with specific on-resistance of 3.4 mΩ·cm^2 and breakdown voltage exceeding 1.5 kV is designed and fabricated.Numerical simulations are carried out to optimize the electric field strength in gate oxide and at the surface of the semiconductor material in the edge termination region.Additional n-type implantation in JFET region is implemented to reduce the specific on-resistance.The typical leakage current is less than 1μA at VDS=1.4 kV.Drain–source current reaches 50 A at VDS=0.75 V and VGS=20 V corresponding to an on-resistance of 15 mΩ.The typical gate threshold voltage is 2.6 V.

A novel high-voltage device structure with an N^+ ring in substrate and the breakdown voltage model

A novel high-voltage device structure with a floating heavily doped N＋ ring embedded in the substrate is reported, which is called FR LDMOS. When the N＋ ring is introduced in the device substrate, the electric field peak of the main junction is reduced due to the transfer of the voltage from the main junction to the N ＋ ring junction, and the vertical breakdown characteristic is improved significantly. Based on the Poisson equation of cylindrical coordinates, a breakdown voltage model is developed. The numerical results indicate that the breakdown voltage of the proposed device is increased by 56% in comparison to conventional LDMOS.

Development of 10 kV 4H-SiC JBS diode with FGR termination

The design, fabrication, and electrical characteristics of the 4H-SiC JBS diode with a breakdown voltage higher than 10 kV are presented. 60 floating guard rings have been used in the fabrication. Numerical simulations have been performed to select the doping level and thickness of the drift layer and the effectiveness of the edge termination technique. The n-type epilayer is 100 μm in thickness with a doping of 6 × 10^14 cm^-3. The on-state voltage was 2.7 V at JF = 13 A/cm^2.