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A gate drive circuit for gallium nitride (GaN) enhancement mode (e-mode) transistors is presented, which avoids parasitic turn-on of the power devices in the halfbridge configuration. New e-mode GaN devices turn on at very low threshold voltages between 1V and 2V. This makes the transistors highly sensitive to spurious turn-on and thus reduces the required safety margin of the gate drive signals. To avoid this parasitic turn-on, a very low gate loop impedance is required. This prevents the halfbridge against bridge shorts during the switching events and guarantees stable gate drive control with increased switching efficiency. The new gate drive circuit is developed in a SPICE simulation environment and verified in a prototype setup by a double pulse test. The simulation matches very well with the experimental result and demonstrates the suppression of parasitic semiconductor turn-on with the proposed gate drive. Furthermore the dissipated switching energy is reduced, compared to a standard gate drive circuit. High DCDC converter efficiency of 98.67% at 1kW output power is achieved by using the driving circuit for a buck converter prototype with 200kHz switching frequency.
An accurate SPICE model is proposed in this paper to calculate the power losses of high voltage converter systems. This supports power circuit optimization in the very first design stage. The parasitic package inductances and the nonlinear voltage dependent semiconductor capacitances are taken into account. In addition the high frequency behavior of the power inductor is investigated. A detailed loss breakdown is done to analyze the main sources of power loss and their physical reasons. The simulation results of the converter waveforms and of its efficiency match very well to the experimental results. The prototype boost converter shows a top efficiency greater than 98.3 % at a switching frequency of 1 MHz and an output voltage of 400 V at the maximum output power of 1 kW.
A Parametric Layout Study of Radiated Emission from High-Frequency Half-Bridge Switching Cells
(2016)
We present a numerical modeling study of radiated emission from half-bridge switching cells based on the method of moments (MoM). A low loop inductance cell design enables high-speed switching of power semiconductors which is demonstrated on a prototype circuit. The layout is further optimized for low radiated emission by variation of the heat sink placement. This is achieved by the heat sink attached to the phase terminal. The performance of the structure in terms of loop impedance, electric field radiation and sensitivity to cable attachments are numerically studied. Emission peaks arising from loop resonances can be reduced by over 20 dB with damping elements in the switching cell. The improved EMI performance of the proposed structure is attributed to decoupling of the loop current from the heat sink structure.
Zusammen maßnehmen
(2016)
Applications in engineering frequently require the adjustment of certain parameters. While the mathematical laws that determine these parameters often are well understood, due to time limitations in every day industrial life, it is typically not feasible to derive an explicit computational procedure for adjusting the parameters based on some given measurement data. This paper aims at showing that in such situations, direct optimization offers a very simple approach that can be of great help. More precisely, we present a numerical implementation for the local minimization of a smooth function f:Rn→R subject to upper and lower bounds without relying on the knowledge of the derivative of f. In contrast to other direct optimization approaches the algorithm assumes that the function evaluations are fairly cheap and that the rounding errors associated with the function evaluations are small. As an illustration, this algorithm is applied to approximate the solution of a calibration problem arising from an engineering application. The algorithm uses a Quasi-Newton trust region approach adjusting the trust region radius with a line search. The line search is based on a spline function which minimizes a weighted least squares sum of the jumps in its third derivative. The approximate gradients used in the Quasi-Newton approach are computed by central finite differences. A new randomized basis approach is considered to generate finite difference approximations of the gradient which also allow for a curvature correction of the Hessian in addition to the Quasi-Newton update. These concepts are combined with an active set strategy. The implementation is public domain; numerical experiments indicate that the algorithm is well suitable for the calibration problem of measuring instruments that prompted this research. Further preliminary numerical results suggest that an approximate local minimizer of a smooth non-convex function f depending on n≤300 variables can be computed with a number of iterations that grows moderately with n.
Reference design projects are implemented to the Xilinx Zynq on the Zedboard which is extended by user defined electronic hardware connected through the Zedboard's FMC (FPGA Mezzanine Card) connector. The implementation method with HDL Workflow Advisor includes constraint definitions for modified reference design projects for use with digital input and outputs and Zynq's XADC (Analog-Digital converter) which is characterized and compared to its data sheet. The bandwidth of the Zynq's internal AXI (Advanced eXtensible Interface) bus connected to the Simulink host PC is determined.
Position measuring devices with sinusoidal measuring signals are widely used in position-controlled servo drives in industrial automation, e.g., for machine tools or semiconductor production machines. Usually, the feedback signal for the speed or velocity controller is calculated from the measured position. Therefore, position measuring errors affect these control loops. This study presents an analytic error model that considers non-ideal sinusoidal measuring signals with basic deviations (amplitude differences, offset errors, and phase shift) as well as signal harmonics. The model was used to systematically investigate the influence of signal quality and the number of signal periods from position measuring devices on speed ripple, across a wide range of speeds. A test stand with a high-resolution reference angle measuring device was used to confirm the results.