73 research outputs found
Multilevel Gate Driver with Adjustable Gate Voltage for Thermal Stress Reduction of Power Switches in Electric Drive Application
No full textDue to varying load currents, the junction temperature variations of power switches causes thermal stress and compromises lifetime. In this paper, proper gate voltage control is used for all power switches in a three-phase electric drive to smooth the profile of conduction losses, therefore reducing thermal stress. A multilevel gate driver with an adjustable gate voltage is introduced for experimental verification of the thermal control method. The lifetime is estimated at last, which indicates an improvement by a factor of two
Thermal Stress Reduction and Lifetime Improvement of Power Switches with Dynamic Gate Driving Strategy
No full textThe thermal stress and lifetime of semiconductor power switches are largely influenced by its current flow profile. Considerable thermal stress and reduced lifetime problems occur especially at low frequency operation. In this paper, a dynamic gate driver that supplies adjustable voltage is proposed to mitigate thermal stress for lifetime improvement
A modular high-voltage pulse generator based on transformer charging with high boosting capability and low-voltage dc input
No full textBy applying repetitive and high-voltage pulses across a specific medium like a reactor or a chamber, a transient plasma is generated which can be used for various applications including water treatment, air purification, and food sterilization. In order to generate the aforementioned pulses, in this paper, a modular high-voltage pulse generator (HVPG) based on cascaded full-bridge sub-modules (FB-SMs) and transformer-based charging is proposed. By utilizing transformer-based charging, the need for a complex balancing circuit with numerous sensors is eliminated and all capacitors are charged incessantly via an uninterruptible charging circuit. The proposed topology has a high boosting gain and is able to charge all capacitors from a low-voltage dc input through the use of an inverter, transformer network, and voltage multiplier circuits. The FB-SMs can provide bipolar and variable voltage pulses, as well as modularity, both benefiting the efficient and cost-effective generation of plasma.The operation principle and the modulation strategy of the proposed HVPG is analyzed and verified by the simulation results using PLECS software
Comparative study of two analytical methods for calculating the parasitic capacitance in toroidal transformers
Full text linkTransformers are of paramount importance in the implementation of different power converters such as pulsed power generators and switched-mode power supplies. The role of the transformer network is becoming even more prominent in applications that use networks of transformers or multi-winding configurations, such as series-connected transformers in pulsed power generators to provide several isolated voltages. Recently, toroidal cores have gained more popularity owing to offering compact size, less weight, and less leakage inductance due to the absence of gaps in their structure. However, their parasitic capacitance can adversely influence the performance of the power converters due to the resulting electromagnetic interference (EMI). Therefore, the parasitic capacitance of the transformer is a decisive factor in the system performance and it should be targeted to allow performance boosting. In this paper, the parasitic capacitance of transformers is modeled based on two different analytical methods. In addition, an accurate function is proposed to calculate effective parasitic capacitances considering all capacitive couplings, including turn-to-turn and turn-to-core capacitors. Afterward, these two methods are verified by planar, axisymmetric, and 3-D finite-element simulations via FEMM and COMSOL Multiphysics software, respectively. Finally, different analyses and simulations are compared with experimental results
A Delta-Sigma Modulated Multi-MHz GaN Half-Bridge featuring Zero-Voltage Switching and Blanking Time Compensation
No full textThis paper proposes a method to control a soft-switching gallium-nitride (GaN) based half-bridge with a delta-sigma (ΔΣ) modulator at multi-megahertz switching frequencies. A GaN-based High Electron Mobility Transistor (HEMT) can be operated at very high switching frequencies. However operating at these switching frequencies can be challenging as pulse-width modulators have several drawbacks when requiring zero-voltage switching with a variable switching frequency. Therefore a ΔΣ-modulator is extended to support zero-voltage switching operation for the entire output range. Also a compensation scheme is implemented that reduces the output voltage distortion due to blanking time. As a result of the proposed ΔΣ modulation scheme, the switching frequency automatically varies to minimize the inductor current ripple. The proposed method is validated in simulation including system non-idealities. Additionally the converter switching frequency range and zero-voltage switching behavior of the half-bridge is analyzed. Results show an improvement up to 14dB in output voltage distortion compared to the same PWM modulated converter with a constant switching frequency. Besides, the PWM modulated converter is not continuously soft-switching and has unnecessarily large inductor current ripple especially at small modulation indices
Determining an optimal ion energy for plasma processing of a dielectric substrate
No full textAn ion energy for plasma processing of a dielectric substrate (109) is determined by exposing the dielectric substrate (109) to a plasma discharge and applying a pulsed voltage waveform to the dielectric substrate. The pulsed voltage waveform comprises a sequence of pulses, each pulse comprising a higher voltage interval and a lower voltage interval having a voltage slope. Further, first pulses of the sequence having differing voltage slopes between one another are generated and applied to the dielectric substrate. For each one of the first pulses, the voltage slope (S) and an output current (I P ) corresponding to the voltage slope are determined. For each one of the first pulses, at least one coefficient (k, b) of a mathematical relation between the voltage slope and the corresponding output current based solely on the voltage slope and the output current determined for one or more of the first pulses is determined. A test function is applied to the at least one coefficient and an optimal voltage slope value corresponding to the at least one coefficient making the test function true is selected. An apparatus for plasma processing of a dielectric substrate implements the above method
Thermal stress reduction of power transistors: Model-based dynamic gate driving applied to electric motor drives
Full text linkHigh Power GaN Module Using 3D-Printed Liquid Coolers for Hard-Switching at Megahertz
No full textThis work presents a power module for high frequency operation, designed to get the maximum performance out of Gallium-Nitride (GaN) devices. The use of metal 3D-printed liquid coolers, ceramic insulation and advanced Indium interface material leads to extremely low thermal resistance and low parasitic impact on switching performance. The presented module consists of four half-bridges, rated for 400 V and output currents of 15 A. The thermal interface achieves a resistance of 1.38 K/W from junction to coolant at a chip cooling area of 19 mm(exp2), while the ceramic insulation contributes 3 pF to the switch-node. The low parasitic design enables a peak switching speed of 186 V/ns during a hard switched turn-on and 30 V overshoot after soft commutation at full load current
High-Frequency Inductor Current Estimator for Power Converters
No full textA method is proposed to estimate the high-frequency inductor current in a half-bridge circuit. Modern wide-bandgap semiconductors such as GaN allow for multi-megahertz switching frequencies. As a result, the frequency content of the inductor current also increases. The conversion delay of an analog-to-digital converter results in a difference between the measured and instantaneous inductor current, especially when the current slope exceeds tenths of milliamps per nanosecond. To overcome this problem, the inductor current is estimated on a digital controller in real-time and the output voltage and current are used for feedback purposes. A slower closed-loop reduced-order observer is developed and extended with an extrapolator to calculate the inter-sample response at a very high frequency. The closed-loop reduced-order observer uses the difference between the measured and estimated output voltage and consequently ensures robustness for model inaccuracies and non-linearities present in the power converter. The extrapolator is running in open-loop but uses the calculated error during the previous update cycle of the closed-loop observer. The proposed estimator is tested in simulation and verified on a field programmable gate array (FPGA). Both the reduced-order closed-loop observer and open-loop extrapolator are merged into a single block to minimize the computational effort in the FPGA
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