A fifth-order fully differential interface circuit (IC) with onchip-test function is presented to improve the noise performance for micromechanical sigma-delta ('-") accelerometer. The proposed onchip-test technique for '-" accelerometers avoids a shaker table applying a sinusoidal signal as the simulated acceleration which involves distortion itself. An electrostatic force feedback linearization circuit is presented to reduce the harmonic distortion resulting in a larger dynamic range (DR). The post-simulation results show that the electrostatic force feedback linearization circuit decreases the harmonic distortion effectively and the proposed on-chip-test technique achieves 98 dB third-order harmonic distortion detection, and the nonlinearity of the proposed circuit is 0.02%.

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The commercial mature gallium nitride high electron mobility transistors (GaN HEMT) technology has drawn much attention for its great potential in industrial power electronic applications. GaN HEMT is known for low on-state resistance, high withstand voltage, and high switching frequency. This paper presents comparative experimental evaluations of GaN HEMT and conventional Si insulated gate bipolar transistors (Si IGBTs) of similar power rating. The comparative study is carried out on both the element and converter level. Firstly, on the discrete element level, the steady and dynamic characteristics of GaN HEMT are compared with Si-IGBT, including forward and reverse conducting character, and switching time. Then, the elemental switching losses are analyzed based on measured data. Finally, on a complementary buck converter level, the overall efficiency and EMI-related common-mode currents are compared. For the tested conditions, it is found that the GaN HEMT switching loss is much less than for the same power class IGBT. However, it is worth noting that special attention should be paid to reverse conduction losses in the PWM dead time (or dead band) of complementary-modulated converter legs. When migrating from IGBT to GaN, choosing a dead-time and negative gate drive voltage in conventional IGBT manner can make GaN reverse conducting losses high. It is suggested to use 0 V turn-off gate voltage and minimize the GaN dead time in order to make full use of the GaN advantages.

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In order to enhance interference immunity and reduce the breakage of rotating shafts (rotors) which happens frequently especially in submersible permanent magnet synchronous motor (PMSM) applications, first a typical rotor structure is established serving as the comparative object, and then two improved schemes with optimal mechanical structure are proposed. Rotor strength, rotor stiffness, and the influence of unilateral magnetic pull on the rotor deflection are calculated analytically. The modal simulation, stress field simulation, and unilateral magnetic pull simulation are analyzed using finite element method (FEM). Position deviation and bending deformation of the rotor caused by the unilateral magnetic pulling force is taken into account to improve the simulation accuracy. The simulation results illustrate that the submersible rotor improved by the proposed schemes presents more excellent stiffness and strength performance compared with the traditional scheme, which indicates that the proposed schemes have important reference values for the structural design of submersible rotor.